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Polystyrene (PS) was blended with shape memory polyurethanes (SMPU). Styrene blocks were grafted onto PU chains during SMPU synthesis to yield a modified SMPU with a higher affinity towards PS. Furthermore, blends containing a compatibilizer, poly (styrene-co-maleic anhydride) (SMA), were also prepared by melt mixing the components. The non-compatibilized blends display phase separated structures with PS rich and SMPU rich phases, which were less evident in blends prepared with either the modified SMPU or SMA compatibilizer. The elastic storage modulus of PS was less affected when blended with SMPU in samples containing modified SMPU with styrene grafts. The impact strength of the blends with higher contents of SMPU modified with styrene blocks (25 and 50 wt.%), after shape recovery, was higher than the impact strength of neat PS. The incorporation of shape memory polymers into a brittle polymer matrix is a potential strategy to improve the toughness by external stimuli.

In this work, the effect of synthesizing shape memory polyurethanes in aqueous dispersions instead of in organic solvents on the structure and properties of the obtained polymers was investigated. Shape memory polyurethanes based on polycaprolactone diol and isophorone diisocyanate were synthesized by two routes: (1) aqueous dispersion (PU/SMWATER) and (2) dissolution in THF (PU/SMTHF). The samples were analyzed by infrared spectroscopy (FTIR), X-ray diffraction (XRD), static light scattering (SLS), atomic force microscopy (AFM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical tests. The aqueous dispersion method led to the production of polyurethanes with a higher degree of phase separation and a higher degree of crystallinity. The morphology of the obtained polyurethanes demonstrated that PU/SMWATER displays a structure with better defined phase separated domains. The polyurethanes exhibited similar average molar masses, soft segment glass transitions (Tgs) and mechanical properties. The lower degrees of phase separation and crystallinity of the PU/SMTHF led to lower values for the shape memory properties (shape recovery ratio (Rr)). The observed changes in the structure of the polyurethanes due to the replacement of organic solvent by an aqueous dispersion during their syntheses confirmed the preparation of shape memory polyurethanes with enhanced shape memory properties. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Packaging materials based on natural polymers are becoming popular because these polymers are derived from renewable resources and can display biodegradability. However, natural polymers are typically highly hydrophilic, and packaging films produced with them can absorb water, leading to dimensional changes and reductions in mechanical properties. In this work, films of thermoplastic starch (TPS) and blends of TPS/low-density polyethylene (LDPE) were prepared, and their surfaces were decorated to alter their hydrophilic characteristics. Micro- (polymer microspheres) and nano-components (polycaprolactone electrospun nanofibers) were deposited on the surface of starch and its blends with LDPE. Nanofibers containing silver sulfadiazine were also used to decorate the starch and its blends to change the topography (evaluated by SEM and atomic force microscopy) and to provide anti-bacterial properties. High values of contact angle (CA) and low values of CA hysteresis were measured for the modified surfaces, including a CA higher than 150° and a hysteresis lower than 10°. Therefore, it was demonstrated that the intrinsically hydrophilic surfaces of biodegradable natural polymers could be altered by creating topographical patterns through decoration with nano-/micro-components to generate hydrophobic and even superhydrophobic features that can be useful in minimizing the water absorption of these materials.

Soft actuators with a fast response to low electrical potentials are critical for wearables and robotics. In this work, hybrid hydrogel nanofiber mats were prepared and tested as soft actuators. Hybrid hydrogel nanofibers were produced by combining electrospinning with in situ photopolymerization of the hydrogel and polymerization of aniline during the formation of the nanofibers. The electrical conductivity of the obtained nanofibers measured by the 4-probe method reached values close to 0.01 S cm−1. Images obtained by atomic force microscopy in conductive mode (I-AFM) were also successfully acquired and proved the conductive and nanometric nature of the hybrid hydrogel nanofibers. Infrared spectra (FTIR) showed that photopolymerization of the hydrogel precursors and aniline polymerization during nanofiber formation were effectively achieved. The elastic modulus of the nanofibers was estimated from AFM nanoindentations, and values close to 10 MPa for the swollen samples were obtained. The swelling ability of the hybrid hydrogel nanofibers was evaluated by comparing AFM images of the nanofibers in dried and swollen conditions to reveal that the swelling degree is reduced by the presence of polyaniline in the nanofibers. The obtained hybrid hydrogel nanofiber mats were tested as actuators in an electrochemical cell. The application of low voltage (1 V) in a 1 MΩ cm water led to fast (2.5 mm s−1) and reversible displacement of the samples. During actuation, thin nanofiber mats could also withstand forces on the order of 80 μN that were measured by coupling the electrochemical cell to a load cell.

The great quantity of synthetic plastic discarded inappropriately in the environment is forcing the search for materials that can be reprocessable and biodegradable. Blends between synthetic polymers and natural and biodegradable polymers can be good candidates of such novel materials because they can combine processability with biodegradation and the use of renewable raw materials. However, traditional polymers usually present high levels of recyclability and use the well-established recycling infrastructure that can eventually be affected by the introduction of systems containing natural polymers. Thus, this work aims to evaluate the effect of reprocessing (simulated here by multiple extrusions) on the structure and properties of a low density polyethylene/thermoplastic starch (LDPE/TPS) blend compared to LDPE. The results indicated that multiple extrusion steps led to a reduction in the average size of the starch-rich phases of LDPE/TPS blends and minor changes in the mechanical and rheological properties of the materials. Such results suggest that the LDPE/TPS blend presents similar reprocessability to the LDPE for the experimental conditions used.

In this study a novel approach for improving the photo-stabilization of polymers by incorporation of nanoparticles of a new niobium compound is reported. For the first time, this approach uses the electronic properties of niobium oxyhydroxide to absorb UV light efficiently to avoid the decomposition of the polymers. The innovative results of this work consist of preparing nanoparticles of niobium oxyhydroxide and its modification by treatment with hydrogen peroxide to alter their ability to absorb radiation and act as a photo-stabilizer for preventing polypropylene degradation. Synchrotron radiation was employed: (i) to explore the niobium nanoparticle form and (ii) to investigate the macromolecular structure of neat PP and PP/Nb compounds before and after degradation. The results from this research study using FTIR-ATR, DSC and microscopies, as TEM, SEM and OM, indicate that the incorporation of niobium oxyhydroxide nanoparticles into the PP matrix provides stability against the action of ultraviolet radiation.

The formation and characterization of poly(itaconic acid)/N-methylol acrylamide/poly(ethylene glycol) (PIA/NMA/PEG) complexes through in situ polymerization of itaconic acid on poly(ethylene glycol) was investigated. FTIR indicated that PEG crystallization was hindered by complex formation. The decrease in the crystallinity of PEG was also observed by DSC and indicated that the mobility of some PEG segments was inhibited by the presence of the polyacid. According to the swelling experiments, complexes proved to be suitable for use as excipient in the preparation of drug delivery systems responsive to pH changing. DMA was used to estimate the crosslink densities and the results were found to be in good agreement with the swelling results. Further, the adhesion strength of the synthesized polymers was used as preliminary evaluation of their potential of mucoadhesion. The results indicated that the adhesion performance is related to the presence of NMA. Drugs which suffer degradation in stomach pH, such as proteins and enzymes are potential candidates to be included in the systems based on PIA/NMA/PEG to pass through the stomach (pH near to 1.2–3.5). Upon reaching the initial portion of the small intestine (pH >5.5), the polymer will swell and release the active substance via diffusion and/or erosion of the matrix.

Synthetic biodegradable polymers are considered strategic in the biomaterials field and are used in various applications. Among the polymers used as biomaterials, polyurethanes (PUs) feature prominently due to their versatility and the ability to obtain products with a wide range of physical and mechanical properties. In this work, new biodegradable polyurethane films were developed based on hexamethylene diisocyanate (HDI) and glycerol as the hard segment (HS), and poly(caprolactone) triol (PCL triol) and low-molecular-weight poly(ethylene glycol) PEG as the soft segment (SS) without the use of a catalyst. The films obtained were characterized by structural, mechanical and biological testing. A highly connected network with a homogeneous PU structure was obtained due to crosslinked bonds. The films showed amorphous structures, high water uptake, hydrogel behavior, and susceptibility to hydrolytic degradation. Mechanical tests indicated that the films reached a high deformation at break of up to 425.4%, an elastic modulus of 1.6 MPa and a tensile strength of 3.6 MPa. The materials presented a moderate toxic effect on MTT assay and can be considered potential materials for biomedical applications.

Bio-based polymers have been reported to have applications in biomedical and pharmaceutical areas. Polysaccharides, especially prepared from plant sources, have served a variety of uses. This work aims to prepare a polymer for use as a pharmaceutical excipient containing a functionalized carbohydrate (pectin) and acrylic monomers (methyl methacrylate, butyl methacrylate and ethyl acrylate) via an emulsion polymerization technique. Carbon double bonds were incorporated into the pectin by reacting this natural polymer with glycidyl methacrylate. The methacrylated pectin was then polymerized with acrylic monomers by emulsion polymerization. The mucoadhesive performance of the materials was investigated by in vitro preliminary assays based on viscometric studies, texture analysis and film wettability. The obtained results showed that the synergistic viscosity increase with greater concentrations of modified pectin. The contact angle decreased, suggesting an increase in the wettability for polymers with large amounts of methacrylated pectin. The addition of mucin in lattices caused an increase in the intermolecular forces and in the work of adhesion. This corroborates the use of pectin as a mucoadhesive excipient for mucoadhesive drug delivery systems.

The use of polyethylene is limited due to its low impact strength among other mechanical properties at extreme ambient temperatures, for example at −46 °C and 66 °C. In this work, different polymer components, such as ultra-high molecular weight polyethylene (UHMWPE) and ethylene-vinyl acetate (EVA), were incorporated in high density polyethylene (HDPE) to test their ability to improve toughness of HDPE at extreme ambient temperatures. The polymer blends were processed by extrusion and injection molding and characterized by rotational rheometry, electron microscopy, thermal analysis, tensile, impact and dynamic mechanical tests. The results showed that low concentrations of EVA and UHMWPE in HDPE increased substantially the impact strength of HDPE at room temperature as well as in extreme ambient temperatures (−46 °C and 66 °C). This result indicates that these HDPE blends can be considered good candidates to replace pure HDPE in applications in which high values of toughness are required at extreme ambient temperatures.

Materials that can switch from stiff to soft or from brittle to tough by slightly changing the temperature, pH, electric, or magnetic fields of their environments, can have a pronounced impact on many applications, including sensors, biomedical materials for less invasive surgeries, and packaging materials. In this work, temperature-sensitive poly(N-isopropyl acrylamide) grafts and low molar mass polyethylene glycol were incorporated in the interfacial region between clay nanoparticles and a bacteria-derived polyhydroxybutyrate matrix to determine if the application of an external stimulus, such as small changes in temperature, could increase the toughness of the nanocomposites. The obtained materials were characterized by using thermal analysis, infrared spectroscopy, dynamic light scattering and dynamic mechanical tests. Mechanical properties were also evaluated at different temperatures and showed that small changes in temperature, such as from 25°C to 40°C, led to a pronounced increase in strain at break of the nanocomposites containing the modified interface. The external stimulus associated with the increase in temperature from 25°C to 40°C can reduce the interfacial interactions between clay and polymer matrix and create a highly plasticized polymer layer between the components of the nanocomposite, which favored the sliding of the interface and ultimately led to high values of elongation. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

The adhesion between polymer adhesives and dentin involves the removal of minerals, by acid etching the dentin surface, to allow for monomer infiltration among collagen fibrils. However, instability within this hybrid layer has been observed, which may partially be attributed to a slow degradation of the collagen not protected by the adhesive. The objective of this work was to improve the stability of the hybrid layer by increasing the interactions between adhesives and collagen through the incorporation of a monomer that behaves reactively toward collagen in the adhesive. In this work, a control adhesive was prepared based on a chemical formulation containing Bis-GMA and HEMA, and was modified by incorporating different concentrations (5, 10, and 20%) of NSA (N-acryloxysuccinimide), which contains an ester group capable of interacting with primary amine. These experimental adhesives were applied to bovine dentin for the in vitro production of the interfacial layer, which was analyzed by Raman spectroscop...

Materials based on a mixture of poly(vinylidene fluoride) (PVDF), poly(2-hydroxyethyl methacrylate) (PHEMA) and LiClO4 were produced to evaluate their ionic behavior and morphological structure to determine if they can be used as an electrolyte in electrical devices. FTIR chemical analysis results indicated the presence of interactions between PVDF, PHEMA and LiClO4. MDSC results showed that the transition temperatures of the polymers shifted to higher temperatures for systems containing high concentrations of each polymer. SEM images indicated that there was some miscibility between the polymers especially for the 25 and 75 wt. % compositions. In terms of the electrical performance, the ionic conductivity level of the electrolyte could be controlled by changing the composition of the system.

Bionanocomposites based on polyhydroxybutyrate (PHB) and cellulose nanowhiskers (CNWs) were prepared by dispers- ing CNWs in poly(ethylene glycol) (PEG) plasticizer subsequently incorporating the CNWs/PEG suspensions in the matrix. The ther- mal properties of the nanocomposites indicate an enlargement in the processing window in comparison to the neat PHB. The nano- composites showed a remarkable increase in the strain level (50 times related to the neat PHB), without a significant loss of the tensile strength with the incorporation of small concentrations of CNWs in the final nanocomposite (up to 0.45 wt %). This behavior was explained in terms of a considerable chain orientation promoted by the presence of CNWs in the same direction of the applied load, which activated shear flow of the polymer matrix. The results described here can be explored to extend the applications of this biopolymer. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 3613-3621, 2013

The purpose of this study was to develop triamcinolone acetonide-loaded polyurethane implants (TA PU implants) for the local treatment of different pathologies including arthritis, ocular and neuroinflammatory disorders. The TA PU implants were characterized by FTIR, SAXS and WAXS. The in vitro and in vivo release of TA from the PU implants was evaluated. The efficacy of TA PU implants in suppressing inflammatory-angiogenesis in a murine sponge model was demonstrated. FTIR results revealed no chemical interactions between polymer and drug. SAXS results indicated that the incorporation of the drug did not disturb the polymer morphology. WAXS showed that the crystalline nature of the TA was preserved after incorporation into the PU. The TA released from the PU implants efficiently inhibited the inflammatory-angiogenesis induced by sponge discs in an experimental animal model. Finally, TA PU implants could be used as local drug delivery systems because of their controlled delivery of TA.

Novel polymeric excipients need to be designed to allow for the controlled delivery of many drugs to treat a variety of diseases. In this work, two polymers based on different proportions of ethyl acrylate, methyl methacrylate, and butyl methacrylate were synthesized by multistage emulsion polymerization using a redox initiator system to yield excipients for the manufacture of prolonged release tablets by the coating or compression technique. Fourier Transform Infrared spectrometer (FTIR) indicated that the polymerization reaction of the monomers was complete without carbon double bond absorption bands. Differential Scanning Calorimetry (DSC) analysis indicated that the glass transition temperature (T g) of the polymers was around 50 °C. The dispersions obtained were characterized in terms of particle size and particle size distribution (PSD) using Dynamic Light Scattering (DLS), and the particle charge (zeta potential) was measured by electrophoretic mobility. The measurements showed particle diameters of approximately 200 nm and a zeta potential close to −60 mV. The low viscosity obtained for the polymers was attributed to bimodal PSD. The dispersions were freeze dried and the particles were submitted to in vitro cell tests to make a preliminary check of the toxicity of the materials. The low viscosity of the polymers, the absence of volatile solvents, and the high solid content (>50%) are ideal for these polymers to be used as coatings and matrices pharmaceutical excipients for prolonged release tablets. In vitro MTT tests suggested that the materials can be considered nontoxic.

The use of surfaces with tunable properties triggered by external stimuli is effective in controlling the interactions between biomaterials and biological entities, such as proteins and cells. The goal of this work is to prove that the presence of poly-n-isopropylacrylamide (P-N-IPAAm) chains grafted onto polyurethane (PU) membranes and used for medical wound dressings can allow the behavior of the surfaces to be shifted from hydrophobic to hydrophilic by reducing the temperature to values lower than the low critical solution temperature (LCST) of the polymer, which is close to 32°C. The manipulation of this behavior can then be used to control cell and protein adhesion on the surface. Grafting of P-N-IPAAm was accomplished by treating the surface of polyurethane membranes with ultraviolet (UV) radiation, followed by polymerizing the isopropylacrylamide from the modified surfaces. The wettability of the surfaces was studied using contact angle measurements as a function of temperature. Infrared spectroscopy was also used to characterize these modified surfaces. The ability of the grafted surfaces to allow adsorption of proteins was evaluated as a function of temperature. The results showed that the amount of proteins adsorbed on the polyurethane membranes could be radically changed by altering the temperature above or below 32°C. In vivo biocompatibility tests were performed on P-N-IPPAm samples, and no indication of toxicity was noted after 7 days of implantation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The treatment of posterior segment ocular diseases, such as uveitis, by using eye drops and oral drugs is usually not effective due to the body's natural barriers to drug penetration. In this study, ocular implants to treat uveitis were synthesized by incorporating dexamethasone acetate, an important type of corticoid used in the treatment of some uveitis, into a biodegradable polyurethane containi clay nanoparticles. Biodegradable polyurethane nanocomposites having poly(caprolactone) oligomers as soft segments were obtained by delaminating clay particles within a polyurethane aqueous dispersion. The drug was incorporated into the polymer by dispersing it in the waterborne polyurethane followed by a drying step. Nanoparticles derived from clay were demonstrated to be able to tailor the mechanical properties of polyurethanes to achieve values that can match the properties of ocular soft tissues. Infrared spectra (FTIR) showed that the presence of clay particles was able to change the microphase separation process typical of polyurethanes. X-ray diffraction and small angle x-ray scattering (SAXS) results were explored to show that the incorporation of both dexamethasone acetate and nanocomponents derived from clay led to a less defined two-phase polyurethane. The presence of clay nanoparticles increased the rate of drug release measured in vitro . Human retinal pigment epithelial cells (ARPE-19) were cultured in contact with polyurethanes and polyurethane nanocomposites, and the viability of them (evaluated by using MTT assay after 7 days) showed that no toxic components were released from polyurethanes containing no drugs during the test.

In this work, we propose the use of shape-memory polymer as an anchoring system for a bladder sensor. The anchoring system was designed from a biomedical biodegradable water-based poly(ester-urethane) produced in an aqueous environment by using isophorone diisocyanate/hydrazine (hard segment) and poly(caprolactone diol)/2,2-bis (hydroxymethyl) propionic acid (soft segment) as the main reagents. Tensile strength and elongation-at-break deterioration upon degradation in synthetic urine were investigated. In-body shape recovery was simulated and measured in synthetic urine. Results indicated that shape recovery can occur at body temperature and expulsion of the sensor by the body along with urine may occur through the combined effect of urine hydrolytic attack and compression exerted by the bladder walls.

The combination of bioactive ceramics and polymers can allow the preparation of composites with tailorable mechanical properties and bioactive behavior. In these composites, bioactive ceramics can act as a source of both reinforcement and bioactivity, while the polymer matrix can add toughness and processability to the material. On the other hand, the effect of using a highly dimensional unstable phase as a reinforcing agent on the long-term properties of the composite is a major concern regarding the lifetime of possible applications. In this work, a bioactive glass-polysulfone particulate composite was prepared by hot-pressing at 215 degrees C a mixture of polysulfone and different concentrations of bioactive glass particles (Bioglass 45S5, particle size range: 125-106 microm) to yield composites having 20 and 40 vol % of bioactive glass particles. The obtained composites were exposed to a simulated body fluid at 37 degrees C for different periods of time ranging from 1 h to 60 days. After the test, the mechanical properties of the composites were investigated by a four-point bending test, while DMS (dynamic mechanical spectroscopy) was used to identify the effect of water on the structure and behavior of the composite. The interface between glass particles and the polymer was also investigated by SEM/EDX and diffuse reflection infrared spectroscopy. The results showed that a decay in the mechanical properties of the composites within the first 20 h of test can occur. Otherwise, after this initial decay, no more pronounced reduction in properties could be noted. The analyses of the fracture surface of composites tested in vitro indicated the hydration of the surface of the particles. Therefore, it was concluded that water migration through the interface of the composite causes surface dissolution of glass particles and formation of voids, which were responsible for the observed decay in mechanical properties. Composites with modified interfaces revealed less damaged fracture surfaces than composites with untreated interfaces.

In recent years, there has been increased interest in biodegradable polyurethanes for use in regenerative medicine because of their versatility and biocompatibility. Nevertheless, these polymers are usually produced using organic solvents that can lead to the release of toxic components. In this work, polyurethane/montmorillonite nanocomposites were designed to work as guided tissue regeneration membranes to treat periodontal diseases. Polyurethanes were synthesized in an aqueous environment. The composition, morphology, and mechanical properties of the biomaterials were evaluated. The cellular viability, proliferation, and morphology changes of rat culture cementoblasts were also investigated using a montmorillonite assay. Small-angle X-ray scattering, X-ray diffraction, and infrared spectroscopy results showed that the degree of clay delamination within the polymer was able to tailor the phase morphology of the polymer, the chemical aspects of the surface, the mechanical properties, and the kinetics of hydrolysis of the materials. The produced scaffolds provided a good environment for the adhesion and proliferation of cementoblasts and thus can be considered suitable biomaterials for participating in procedures associated with periodontal regeneration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The combination of polymers with macromers derived from inorganic species and oligomers to yield controlled hyper structures can potentially allow the design of materials with tunable mechanical, optoelectronic properties and chemical behavior. In this work, novel hybrid structures were processed based upon the controlled insertion of macromers derived from inorganic groups and oligomers into previously chemically modified polymer frameworks. The chemical procedure involved a series of steps that started with the creation of a functionalized framework to act as host for the construction of the polymer–macromer hyper structures. The designed polymer framework was obtained by incorporating highly polar groups, such as sulfonic acid, into poly(aryl ether sulfones). Following this step, the newly promoted reactive sites were used to insert alkoxysilane groups through reacting modified poly(aryl ether sulfones) with specifically selected silane compounds. The chemical reactions and the obtained novel structures were characterized using NMR, FTIR, AFM and thermal analysis. Results showed that structural parameters such as the concentration of siloxane bonds across the material and the density of cross-links could be controlled by selecting different conditions of reaction. Completely homogeneous and also heterogeneous, but still controlled, structures could be produced using the described procedure. The developed polymer structures containing controlled profiles of concentration, densities and chemical functionalities can have tailorable mechanical properties and chemical activity.

Controlled delivery of drugs is a major issue in the treatment of ocular diseases, such as in the treatment of uveitis. In this study, dexamethasone acetate, an important type of corticoid used in the treatment of some uveitis, was incorporated into biodegradable polyurethanes (PU) having different macromolecular architectures. The biodegradable polyurethanes were obtained by preparing PU aqueous dispersions having poly(caprolactone) and/or poly(ethylene glycol) as soft segments. The drug was incorporated into the polymer by dissolving it in the PU aqueous dispersion. FTIR results showed the presence of the drug in the polymer with its original chemical structure. Small angle X-ray scattering (SAXS) results were explored to show that the incorporation of dexamethasone acetate led to the modification of the nanostructure of the polyurethane having only poly(caprolactone) as the soft segment, while the drug did not change significantly the microphase separated structure of PU having both poly(caprolactone) and poly(ethylene glycol) as soft segments. The evaluation of the release of the drug in vitro demonstrated that the obtained biodegradable polyurethanes were well succeeded in delivering dexamethasone acetate at an almost constant rate for 53 weeks. The presence of poly(ethylene glycol) together with poly(caprolactone) as soft segment in biodegradable PU was able to increase the rate of dexamethasone acetate release when compared to the rate of drug release from PU having only poly(caprolactone).

Polyester concretes have been used in constructions for more than 20 years. This type of polymer concrete can advantageously replace traditional Portland concrete in situations that require fast consolidation of the material. Otherwise, polyester concretes are usually more expensive than Portland concretes. Part of the high cost of the polyester concretes is due to the fact that the aggregates used in the formulation of the concretes need to be dried prior to their incorporation into the polymer matrix. In this work, the use of different curing systems (methacrylic acid and maleic anhydride) was investigated to test the hypothesis that the introduction of acid functionalities into unsaturated polyesters based on isophthalic acid could both restrict the detrimental effect of moisture in the curing process and also improve interfacial interactions even in polyester concretes containing wet aggregates. In this work, as there was no search for ways to reduce cost of polyester concretes and also to contribute to the environmental preservation, unsaturated polyesters were synthesized from PET bottles and tested in the fabrication of concretes by reacting them with a conventional curing agent (styrene). Gel permeation chromatography, infrared spectroscopy, and electron microscopy were used to monitor and analyze the production of unsaturated polyester resins and concretes. Mechanical properties were also evaluated by compression tests. Results showed that methacrylic acid and maleic anhydride, when used as curing agents, led to the production of polyester concretes having higher mechanical properties in both dry and wet states than conventional polyester (based on isophthalic acid) concretes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Porous scaffolds have been developed in many forms and materials, but few have reached the combination of adequate physical, biological and mechanical properties. In previous works hybrid foams bioactive glass polyvinyl alcohol (PVA) were prepared by the sol-gel process for application as scaffold for bone tissue engineering. We observed that synthesis parameters such as PVA hydrolysis grade, PVA solution concentration, and PVA content in the hybrids affected both synthesis results and structural characteristics of the obtained foams. A marked change in foaming behavior occurs for PVA contents around 60%. In this work we analyze the effect of different compositions and synthesis parameters on the mechanical behavior of PVA-bioative glass foams. The compression tests showed that an increase of PVA fraction changes the mechanical behavior due to different mechanisms leading to cell collapse. For hybrids with lower PVA contents (20 to 30%) the cell collapse is due to brittle crushing. For intermediate polymer content (40-60%) the contribution of plastic yielding in the plateau region increases and it becomes the predominant mechanism of cell collapse for samples with higher polymer content (70-80%).

Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of these bioceramics with the flexibility of polymers. In previous work hybrid foams with 80% bioactive glass and 20% polyvinyl alcohol (PVA) were prepared by the sol-gel process for application as scaffold for bone tissue engineering. In this work it was evaluated the effect of increasing the PVA content of the hybrids on structural characteristics and mechanical properties of hybrid foams produced by this method. The hybrids were prepared with inorganic phase composition of 70%SiO2-30%CaO and PVA fractions of 20 to 60% by the sol-gel method. The structural and mechanical characterization of the obtained foams was done by FTIR, SEM, Helium Picnometry, and compression tests. To reduce the acidic character of the hybrids due to the catalysts added, different neutralization solutions were tested. The immersion of hybrids in a calcium acetate solution was the most adequate neutralization method, avoiding calcium loss while maintaining pH nearly 7,0 and low PVA loss. The foams presented porosity of 60-85% and pore diameters of 100-500μm with interconnected structure. The pore structure varied with the polymer content in the hybrid. The compression tests showed that an increase of PVA fraction in the hybrids improved their mechanical properties.

Investigation of novel biomaterials for bone engineering is based on the development of porous scaffolds, which should match the properties of the tissue that is to be replaced. These materials need to be biocompatible, ideally osteoinductive, osteoconductive, and mechanically well-matched. In the present paper, we report the preparation and characterization of hybrid macroporous scaffold of polyvinyl alcohol (PVA)/bioactive glass through the sol–gel route. Hybrids containing PVA (80, 70 and 60 wt%) and bioactive glass with composition 58SiO2–33CaO–9P2O5 were synthesized by foaming a mixture of polymer solution and bioactive glass via sol–gel precursor solution. PVA with two different degree of hydrolysis (DH), 98.5% (high degree) and 80% (low degree) were also investigated, in order to evaluate the influence of residual acetate group present in polymer chain on the final structure and properties of 3D porous composite produced. The microstructure, morphology and crystallinity of the hybrid porous scaffolds were characterized by X-ray diffraction (XRD), Infrared Fourier Transform spectrometry (FTIR) and Scanning electron microscopy (SEM/EDX) analysis. In addition, specific surface area was assessed by B.E.T. nitrogen adsorption method and mechanical behavior was evaluated by compression tests. Preliminary cytotoxicity and cell viability were also performed by the MTT assay. VERO cell monolayers were grown in 96-well microtiter plates. The results have clearly showed that hybrid foams of polyvinyl alcohol/bioactive glass (PVA/BG) with interconnected macroporous 3D structure were successfully produced. All the tested hybrids of PVA/BG have showed adequate cell viability properties for potential biological applications.

In the present work, we aimed to investigate the immobilization of Bovine Serum Albumin (BSA) into poly (vinyl alcohol) (PVA) network. PVA hydrogels with BSA were characterized by Synchrotron SAXS radiation associated with Fourier Transform Infrared Spectroscopy (FTIR). We synthesized hydrogels by dissolving PVA in aqueous solution (5.0 wt%) and crosslinked with glutaraldehyde (GA). PVA and PVA/GA hydrogels samples were immersed in BSA aqueous solution for protein immobilization. FTIR spectra showed major vibration bands associated with PVA and GA chemical groups, and BSA protein amides. Regarding to SAXS characterization, the slope of the log I(q), scattering intensity, as a function of log q, the scattering vector, provided important information about the morphology of entities present in the system. Two different scattering patterns were obtained for PVA (slope = 3.5) and PVA/BSA (slope=1.5 and 3.0). These results have given strong evidence of nano-ordered dispersed globular BSA immobilized into chemically crosslinked PVA hydrogel network. SAXS analyses have indicated that the scattering q-vector maximum value was shifted by altering PVA polymer hydrogel with GA crosslinker and also with BSA incorporation into the network.

Aqueous dispersion of polyurethane ionomer (PUD), based on poly (propylene glycol) (PPG) as soft segment, isophorone diisocyanate (IPDI) as diisocyanate, dimethylol propionic acid (DMPA) as ionic center, hydrazine (HZ) as crosslinker and triethyl amine (TEA) as neutralizer, was reinforced with 1 to 5 wt % of clay to obtain nanocomposites. Substitution of Na+-montmorillonite for bentonite was made by using three types of bentonite. The tensile strength and elongation at break decreased for all nanocomposites having 5% clay in comparison to pristine polyurethane. The enhancement of mechanical properties over pristine polyurethane was achieved only by using 1% of clay. The structure of layered silicates in polyurethane was found to be maintained in some extent as evidenced from wide-angle X-ray diffraction analysis. Nevertheless, the rather weak and broad diffraction peaks appearing in the curves of bentonite clays nanocomposites indicated that a nanostructure of silicate in waterborne PU system has been formed using a low cost raw material and an environmental friendly aqueous polymer precursor.

Summary: Interactions between surfaces with attached polymers are very common in both biological and engineering fields. These types of interactions are critical in processes such as coagulation and flocculation in mineral processing, biological recognition in metabolic processes and stress transference in polymer composites, among others. Although many mechanisms have been proposed to explain phenomena occurring at the interfaces on a molecular level, few experimental procedures can give direct information about them. In this work, interactions occurring at interfaces containing attached polymer chains, such as the ones that are present in polymer composites, were studied by using AFM. In order to identify the effect of the structure of the interface on phenomena such as stress transference and energy dissipation, polymers with different molar mass, areal density and chemical architecture were synthesized and attached to substrates and AFM cantilevers. Force-distance curves, obtained by AFM, provided some fundamental information about the mechanisms involved when polymers attached to different surfaces interact. Results showed that chains grafted on different surfaces can interact via entanglements and intersegmental bonding. Based upon the application of the AFM modified technique, interfaces containing polymers, such as in polymer composites, can be designed and optimized through the manipulation of its structure to achieve new roles in the performance of systems.

Biossensores têm a função de detectar e analisar tanto quantitativa como qualitativamente a presença de uma certa molécula em um determinado meio, isto com resposta em tempo real e sem etapas intermediárias de processo. Para isso, o biossensor possui sempre em seu conjunto um sistema de reconhecimento biológico que o diferencia de qualquer outro tipo de sensor. O objetivo deste trabalho foi desenvolver hidrogéis condutores a partir da combinação de polianilina com hidrogel poli(metacrilato de hidroxietila) e avaliar alguns aspectos associados à possível utilização deste como base de um biossensor capaz de detectar a presença de frações tóxicas do antígeno do veneno do escorpião Tytius Serrulatus. Hidrogéis condutores foram sintetizados a partir da mistura, em diferentes proporções, de polianilina e poli(metacrilato de hidroxietila) em um solvente comum. A condutividade elétrica (método de quatro pontas), capacidade de inchamento e morfologia (microscopia eletrônica de varredura) foram avaliadas para blendas com diferentes composições. Antígenos relativos ao veneno do escorpião Tytius Serrulatus foram incorporados às blendas condutoras a partir do inchamento dos hidrogéis por soluções aquosas contendo as moléculas de interesse. A imobilização e bioatividade das biomacromoléculas nos hidrogéis foram constatadas através de ensaio imunoabsorvente ELISA cujos resultados foram avaliados por espectroscopia na região do ultravioleta-vísivel. Os resultados mostraram que a incorporação de baixos conteúdos de Pani (20% em massa) em hidrogéis de poli(metacrilato de hidroxietila) foi suficiente para a produção de materiais com elevada condutividade elétrica e grande capacidade de inchamento. Moléculas associadas ao veneno do escorpião Tytius Serrulatus foram imobilizadas com sucesso nos hidrogéis condutores e mantiveram suas capacidades funcionais.

The purpose of this study is to develop novel poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogel blends and PVA-derived organic–inorganic hybrid materials and perform nanostructural characterizations. PVA and PEG hydrogels were prepared by dissolving the polymer in aqueous solution, followed by addition of glutaraldehyde (GA) chemical crosslinker. Hybrids were synthesized by reacting PVA in aqueous solution with tetraethoxysilane (TEOS). PVA/TEOS were also modified in the nanometer-scale by crosslinking with GA during the synthesis reaction. Hydrogels and hybrids were characterized by using small-angle X-ray scattering synchrotron radiation (SAXS) and Fourier transform infrared spectroscopy (FTIR). Thin film samples were prepared for SAXS experiments. SAXS results have indicated different nano-ordered disperse phases for hydrogels made of PVA, PEG, PVA/GA, PVA/PEG. Also, PVA/TEOS and PVA/TEOS/GA hybrids have indicated different X-ray scattering patterns. FTIR spectra have showed major vibration bands associated with organic–inorganic chemical groups present in the hybrid nanocomposites PVA/TEOS and PVA/TEOS/GA. PVA/PEG hydrogels and PVA-derived hybrid materials were successfully produced with GA crosslinking in nanometer-scale network.

Incorporation of polyaniline (PAni) into thermoplastic elastomers can be used to produce materials that potentially combine the good mechanical properties and processability of thermoplastic elastomers with electrical, magnetic and optical characteristics of PAni. In this work, a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene copolymer (SEBS) was chemically modified by grafting a sulfonic group onto the chain backbone in order to promote higher levels of compatibility between the thermoplastic elastomer and polyaniline. The sulfonation process was performed by reacting SEBS with acetyl sulfate. Infrared spectroscopy and titration were used to monitor the amount of sulfonic groups successfully grafted on SEBS. Mechanical tests performed in sulfonated SEBS showed that sulfonation levels lower than 15% did not reduce substantially the mechanical properties of SEBS. PAni doped with dodecylbenzenesulfonic acid (PAni·DBSA), used in the preparation of the blends, was prepared by the “in situ doping polymerization” method. PAni·DBSA was then blended in solution with SEBS having different levels of sulfonation. The introduction of sulfonic group into the structure of SEBS improved coulombic interactions between the phases in the blend and enhanced compatibility. As a consequence, higher values of electrical conductivity (measured by the four-probe method) were achieved in blends with sulfonic groups grafted onto polymer chains. Concentrations as low as 20 wt% of PAni were able to lead to electrical conductivities of PAni·DBSA/sulfonated SEBS blends close to 1.2 S/cm. Optical micrographs of the blends showed that PAni·DBSA/sulfonated SEBS microstructure is composed of a very disperse group of small conducting particles. This type of microstructure would then be responsible for the enhanced electrical conductivity and low percolation threshold of PAni·DBSA/sulfonated SEBS, when compared to PAni·DBSA/SEBS blends.

Nos últimos anos tem-se verificado uma acentuada desaceleração no desenvolvimento de novos homopolímeros, e nota-se um crescente interesse no estudo e desenvolvimento de processos que misturam os polímeros já existentes, dando origem às blendas poliméricas. Neste trabalho, blendas de poliestireno e policarbonato foram preparadas por extrusão em diferentes proporções. O processo de separação de fases foi estudado através da combinação de ferramentas analíticas como microscopias de infravermelho (micro-FTIR), óptica, eletrônica de varredura, e análise térmica. Resultados obtidos a partir das microscopias eletrônica e óptica permitiram definir as correlações entre morfologia e grau de estabilidade das fases do sistema. A composição e proporção relativas das fases das blendas foram determinadas usando microscopia de infravermelho. Tais resultados foram utilizados no cálculo do parâmetro de interação polímero-polímero de Flory-Huggins. In the last decade, a progressive reduction on the development of new homopolymers could be observed, while processes, such as blending, that combine commercially available polymers were emphasized. In this work, polycarbonate-polystyrene blends were extruded in compositions from 0% to 100% of polycarbonate in weight. The phase separation process was studied by combining a series of analytical techniques such as scanning electron, optical and infrared microscopy (micro-FTIR). Electron and optical microscopy allowed the determination of a correlation between phase morphology and the degree of phase stability of the system. The composition of the phases and information on phase stability were determined by using micro-FTIR. The Flory-Huggins interaction parameter could also be calculated from the micro-FTIR data.

Polymer composites based on the introduction of bioactive materials into polymer matrices can combine mechanical with bioactive properties suitable for many potential biomedical applications. In this work, glass-ceramics derived from the crystallization of bioactive glasses were tested as reinforcing agents in polymer composites. The kinetics of crystallization of soda-lime silica glasses containing phosphorous was studied to define conditions for obtaining glass-ceramics having different microstructures. This type of glass can be used in biomedical applications due to its ability to bind to bone (bioactive behavior). Evaluation of the mechanical properties of glass-ceramic bodies derived from bioactive glasses has allowed us to determine the relationship between microstructure and properties. A particular microstructure capable of leading to fine grained glass-ceramics with enhanced properties was then reproduced in bioactive glass particles. Thus, bioactive glass particles were crystallized to different levels and used as reinforcing agents in polymer (polysulfone) composites. Mechanical properties of composites were evaluated using a four-point bending test. Glass-ceramic reinforced composites showed higher elastic modulus than glass reinforced composites. Therefore, crystallization of silicate glasses used as reinforcing agents in polymer matrices is a possible way to enhance the mechanical properties of composites. Polymer composites having bioactive glass-ceramic particles display some mechanical properties comparable to human cortical bone.

Calcium phosphates and bioactive glasses have been used in many biomedical applications for more than 30 years due basically to their bioactive behavior. However, ceramics are too brittle for applications that require high levels of toughness and easy processability. In this work, a biphasic calcium phosphate (BCP) and a bioactive glass composition (BG) were combined with polymers to produce composites with tailorable properties and processability. The BCP particles were synthesized by a precipitation technique. The BG particles were produced by sol-gel processing. The BCP particles were treated with a silane agent to improve the compatibility between particles and the polymer matrix. Dense samples were produced by hot pressing (200 °C) a mixture of 30 wt.% of particles in poly (methyl methacrylate). The samples produced were characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Mechanical properties were evaluated by a three point bending test. Samples were also submitted to in vitro bioactivity test and in vivo toxicity test. Results showed that the production of the composites was successfully achieved, yielding materials with particles well dispersed within the matrices. Evaluation of the in vivo inflammatory response showed low activity levels for all composites although composites with silane treated BCP particles led to milder inflammatory responses than composites with non-treated particles.

By a combination of inorganic and organic species at a molecular level, a new series of biomaterials having optimal controllable properties can be fabricated. The goal of this work is to determine how the reactivity of the composites (inorganic–organic hybrids) can be controlled by altering the nanostructure of the materials. Hybrids were synthesized by reacting poly(vinyl alcohol) (PVA) in acidic solution with either tetraethoxy silane (TEOS) or tetramethoxy silane (TMOS). The inorganic phase was also modified by incorporating calcium and phosphate compounds. The properties of the hybrids were determined by swelling experiments, infrared spectroscopy, and scanning electron microscopy/microprobe analysis. Transparent PVA–silicate hybrid free-standing films, having a range of compositions within the system, were produced by allowing the rate of hydrolysis of the alkoxide to be compatible with the kinetics of the dissolution processes of both the polymer and calcium-phosphate compounds. Results obtained from swelling experiments and infrared spectroscopy showed that the crosslink density can be increased when hybrids are prepared with larger concentrations of the inorganic component. Moreover, hybrids prepared at temperatures as high as 60°C have, among other properties, greater crosslink densities and inorganic phases with larger amounts of S–O–Si bridging bonds. Swelling experiments also showed that the obtained hybrids varied in their reactivities ranging from fast dissolution to hydrogel properties. We also demonstrate that the degree of reactivity can be controlled by manipulating structural factors of the hybrids such as the crosslink density, proportion of the phases and composition of the inorganic phase, among others.

Composites that can mimic the in vitro bioactive behavior of bioactive glasses were designed to fulfill two main features of bioactive glasses that are responsible for their high bond-to-bone rates: (1) capability of providing ions such as calcium and phosphate to the nearby environment and (2) ideal surface structure that allows fast heterogeneous precipitation of hydroxy-carbonate-apatite (HCA). The novel composites were prepared by incorporating bioactive glass particles into polymer matrices. The in vitro bioactivity test was performed by introducing samples into a buffered solution as well as into a simulated body fluid solution. FTIR was used to evaluate the kinetics of HCA (hydroxy-carbonate-apatite) precipitation. The results showed that the obtained composites can supply ions, such as silicates and phosphates in rates and concentrations comparable or superior than bulk bioactive glasses. Moreover, the surface chemistry of the composites was altered to mimic the surface of bioactive glasses. It was demonstrated that the in vitro bioactivity of the composites was enhanced by chemically modifying polymer surfaces through the introduction of special alkoxysilane groups. Nesse trabalho, compósitos de matriz polimérica foram projetados para reproduzir duas importantes características dos vidros bioativos, que são responsáveis por capacitar a tais materiais se ligarem rapidamente ao tecido ósseo: (1) capacidade de prover íons, como os de cálcio e fosfato, ao ambiente vizinho; e (2) possuir uma estrutura de superfície ideal que favoreça uma rápida precipitação heterogênea de hidroxiapatita carbonatada (HCA). Este novo compósito foi preparado através da incorporação de partículas de vidro bioativo numa matriz polimérica. O teste in vitro de bioatividade foi realizado através da introdução das amostras em soluções-tampão, assim como em soluções simuladoras dos fluidos orgânicos. Espectroscopia no infravermelho foi usada para avaliar a cinética de precipitação da HCA. Os resultados mostraram que os compósitos desenvolvidos podem suprir íons em taxas e concentrações comparáveis ou superiores às de vidros bioativos puros. Além disso, a química de superfície dos compósitos foi alterada para reproduzir o tipo de superfície presente em vidros bioativos. Os resultados demonstraram que a bioatividade in vitro de compósitos pode ser ampliada através da modificação química das superfícies do polímero via introdução de grupos alcoxissilanos especiais.

Many chemical and physical methods, such as plasma, e-beam, sputtering, CVD and others, have been used to modify the structure of polymer surfaces by depositing thin inorganic films. Most of these techniques are based upon the use of high energy sources that ultimately can damage either chemically or physically polymer surfaces. Moreover, these methods are usually not versatile enough to allow the design of structurally and chemically tailored surfaces through the control of the distribution of chemical functionalities throughout the surface. In this work, inorganic species were introduced onto polymer substrates in a controlled manner by performing a sequence of chemical reactions at the surface. Sulfonation followed by silanization reactions were used to graft alkoxysilane species at the surface of poly(aryl sulfones). The heterogeneous chemical modification of poly(aryl sulfones) was monitored by FTIR-ATR (Attenuated Total Reflection - FTIR). Model compounds were used to study the chemical reactions occurring during the grafting procedure. The results showed that the developed procedure can allow a controlled introduction of inorganic species onto polymer surfaces. Furthermore, in order to prove that this procedure enables the deposition of specific chemical functionalities onto polymer surfaces that can be used to create chemically and structurally tailored surfaces, silicate films were deposited on previously silanated PAS bioactive glass composites. In vitro tests showed that the surface modified composite can enhance the rates of hydroxy-carbonate-apatite precipitation.

Silane coupling agents have been frequently used as interfacial agents in polymer composites to improve interfacial strength and resistance to fluid migration. Although the capability of these agents in improving properties and performance of composites has been reported, there are still many uncertainties regarding the processing-structure-property relationships and the mechanisms of coupling developed by silane agents. In this work, an Atomic Force Microscope (AFM) was used to measure interactions between polymers and silica substrates, where silane networks with a series of different structures were processed. The influence of the structure of silane networks on the interactions with polymers was studied and used to determine the mechanisms involved in the coupling phenomenon. The AFM results showed that phenomena such as chain penetration, entanglements, intersegment bonding, chain conformation in the vicinities of rigid surfaces were identified as being relevant for the overall processes of adhesion and adsorption of polymeric chains within a silane network. AFM adhesion curves showed that penetration of polymeric chains through a more open silane network can lead to higher levels of interactions between polymer and silane agents.

Interactions between polymers and inorganic surfaces are present in a series of phenomena involving processes such as coagulation and deffloculation of ceramic powder and adsorption of organic macromolecules on the surface of implants, among others. In this work, Atomic Force Microscopy (AFM) was modified to allow the evaluation of interactions between polymeric chains and inorganic surfaces (silica) with different structures. Polymers (sulfonated polysulfone) were grafted onto AFM cantilevers. AFM force-distance curves were obtained for this modified tip against a series of substrates produced by depositing silica films on silicon wafers. The structure of the silica layer was modified by employing heat treatments at different temperatures. The results showed that the interactions between polymer and surfaces are dependent on the structure of the surfaces. Penetration of the polymeric chains can occur through a soft gel layer (substrates treated at low temperature, 110 °C). For surfaces with dense silica layers, the results showed that not only the concentration of hydroxy groups but also their spatial distribution along the surfaces are important in defining the magnitude of interactions between polymers and surfaces. A model involving a molecular recognition process, in which interactions are maximized for inorganic surfaces with structures that can match the chemical architecture of the polymer, was then used to explain the obtained results.

Mantas não tecidas de nanofibras de três polímeros biodegradáveis poli(ácido láctico), PDLLA, poli(Ε-caprolactona), PCL, e poli(butileno adipato-co-tereftalato), PBAT e seus nanocompósitos com uma nanoargila montmorilonita (MMT) foram produzidas por eletrofiação. A morfologia, o comportamento térmico e a estrutura interna das nanofibras foram analisados por microscopia eletrônica de varredura e transmissão, calorimetria diferencial de varredura e difração de raios X, respectivamente. Observou-se que as nanofibras dos nanocompósitos possuíam diâmetros menores do que os correspondentes polímeros puros e que as nanofibras de PBAT puro e de PBAT/MMT apresentavam a menor cristalinidade de todas as mantas. A viabilidade celular de todas as nanofibras foi analisada pela técnica de redução do sal de tetrazolium pelo complexo enzimático piruvato desidrogenase presente na matriz de mitocôndrias (teste MTT). Os resultados mostraram que nenhuma manta nanofibrílica apresentou toxicidade às células e que as nanofibras de PBAT puro e seu nanocompósito propiciaram ainda um ambiente mais favorável ao desenvolvimento celular de fibroblastos de cardiomiócitos do que as condições oferecidas pelo controles, provavelmente por apresentarem menores diâmetros e baixa cristalinidade em relação às demais nanofibras. Estes resultados mostram o potencial de uso destas mantas nanofibrílicas como suportes de crescimento celular. Non-woven mats of nanofibers of three biodegradable polymers, viz. poly(lactic acid), PDLLA, poly(Ε-caprolactone), PCL, and poly(butylene adipate-co-terephthalate), PBAT, and their nanocomposites with montmorillonite nanoclay (MMT) were produced by electrospinning. The morphology, thermal behavior and internal structure of the nanofibers were analyzed by scanning and transmission electron microscopy, differential scanning calorimetry and wide angle X-ray diffraction, respectively. The nanofibers of the nanocomposites had lower diameters than the nanofibers of the corresponding neat polymers, while the nanofibers from PBAT and PBAT/MMT were the least crystalline. The cell viability of all the nanofibers was analyzed by reduction of the tetrazolium salt by the pyruvate dehydrogenase enzymatic complex present in the mitochondria (MTT test). None of the nanofibers was toxic to the cells and the PBAT and PBAT/MMT nanofibers exhibited a more favorable environment for developing fibroblasts from cardiomyocytes than the control, probably due to their low crystallinity. These results demonstrated the potential use of nanofibers´ mats as scaffolds for cell growth.

The development of polymer/bioactive glass has been recognized as a strategy to improve the mechanical behavior of bioactive glass-based materials. Several studies have reported systems based on bioactive glass/biopolymer composites. In this study, we developed a composite system based on bioactive glass nanoparticles (BGNP), obtained by a modified Stober method. We also developed a new chemical route to obtain aqueous dispersive biodegradable polyurethane. The production of polyurethane/BGNP scaffolds intending to combine biocompatibility, mechanical, and physical properties in a material designed for tissue engineering applications. The composites obtained were characterized by structural, biological, and mechanical tests. The films presented 350% of deformation and the foams presented pore structure and mechanical properties adequate to support cell growth and proliferation. The materials presented good cell viability and hydroxyapatite layer formation upon immersion in simulated body fluid. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

Biodegradable polyurethane was synthesized by preparing aqueous polyurethane dispersion having poly(caprolactone) and poly(ethylene glycol) as soft segments. Montmorillonite particles were delaminated within the waterborne polyurethane to produce a nanocomposite. The triamcinolone acetonide (TA), an important corticoid drug, was dispersed into the nanocomposite followed by a drying step to produce an implantable drug delivery system. Infrared (FTIR) results demonstrated that the original chemical structure of the TA was preserved after incorporation into the nanocomposite. Wide angle (WAXS) and small angle X-ray scattering (SAXS) results suggested that TA and clay do not dramatically change the morphology phase of the polymer although they can interact with each other. The presence of montmorillonite particles in the nanocomposite reduced the rate of TA release as compared to the pure polyurethane and enhanced the mechanical properties of the polymer. The overall results indicate that montmorillonite clay-based polyurethane nanocomposite could be potentially applied as local TA delivery system.

Two types of photopolymerizable and injectable polyurethane acrylates (PUAs), based on poly(propylene glycol) or poly(caprolactone diol) and hydroxyethyl methacrylate, were synthesized and characterized in order to obtain information regarding their use as an injectable material for biomedical applications. Structural characteristics of the biomaterials, including the degree of phase separation, were evaluated by Fourier transform infrared spectroscopy. The viscosities of the obtained biomaterials make them suitable for injection, molding and photopolymerization using visible light, as demonstrated by the injection test. The cured polymers had mechanical properties comparable to those of certain soft tissues, such as skin. An in vitro cell-polyurethane cytotoxicity study was carried out with mesenchymal stem cells from rat tibias and femurs. The proliferation/viability of the cells in the presence of the synthesized material was assessed by the MTT assay, collagen synthesis analysis and the expression of alkaline phosphatase. The results that were obtained through the in vitro tests indicated that PUAs are cytocompatible. The in vivo experiments were correlated with the in vitro tests and showed low levels of toxicity for the obtained biomaterials. Histology cross-sections showed that the biomaterials induced no significant inflammatory reaction. Our study demonstrates the potential for using synthesized photocurable polyurethanes in biomedical applications. Furthermore, the obtained injectable polymer systems employ minimally invasive procedures and can be molded in situ before photopolymerization with visible light.

Bioactive glasses (BaG) can bind to human bone tissues and have been used in many biomedical applications for the last 30 years. However they usually are weak and brittle. On the other hand, composites that combine polymers and BaG are of particular interest, since they often show an excellent balance between stiffness and toughness. Bioactive glass-poly(vinyl alcohol) foams to be used in tissue engineering applications were previously developed by our group, using the sol-gel route. Since bioactive glass-polymer composite derived from the sol-gel process cannot be submitted to thermal treatments at high temperatures (above 400 degrees C), they usually have unreacted species that can cause cytotoxicity. This work reports a technique for stabilizing the sol-gel derived bioactive glass/poly(vinyl alcohol) hybrids by using glutaraldehyde (GA), NH(4)OH solutions and a blocking solution containing bovine serum albumin. PVA/BaG/GA hybrids were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM/EDX) analyses. Moreover, MTT (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) biocompatibility and cytotoxicity assays were also conducted. The hybrids exhibited pore size varying from 80 to 820 mum. After treatments, no major changes in the pore structure were observed and high levels of cell viability were obtained.

Foi sintetizada uma dispersão aquosa de poliuretano (PUD) na qual o poli(propileno glicol) (PPG) foi utilizado como segmento flexível. O segmento rígido foi baseado nos reagentes isoforona diisocianato (IPDI) e a diamina hidrazina (HZ), produzindo um poli(uretano-uréia). A PUD assim obtida foi modificada com Na+-montmorilonita (Na+-MMT) para gerar nanocompósitos (CPUD’s) com 1, 3 e 5 % de argila. Neste processo, o aumento do espaçamento basal das camadas de silicato foi provocado pela água sem necessidade de qualquer tratamento químico da argila. De acordo com as curvas de difração de raios X (XRD), os nanocompósitos obtidos apresentaram partículas de argila intercaladas com o polímero, enquanto a técnica de espalhamento de raios X de baixo ângulo (SAXS) detectou evidências de uma esfoliação parcial da montmorilonita. A esfoliação incompleta das partículas de argila indica re-agregação dos nanocomponentes (inicialmente delaminados na dispersão aquosa) durante a formação do filme. O grau de ligações de hidrogênio, avaliado por espectroscopia no infravermelho (FTIR), foi usado para investigar o efeito da argila no processo de separação de microfases do poliuretano e indicou uma tendência de perturbação da estrutura dos domínios do poliuretano com a presença da argila. A PUD exibiu valores de resistência à tensão na ruptura e alongamento na ruptura na faixa de 30 MPa e 1400% respectivamente. A adição de 1% de argila na PUD promoveu aumentos no módulo e tensão na ruptura de cerca de 230 e 20% respectivamente em relação ao polímero puro, sem perda significativa do alongamento na ruptura. Waterborne polyurethane (PUD) was synthesized by using poly(propylene glycol) (PPG) as soft segment. The hard segment was formed by extending isophorone diisocyanate (IPDI) with hydrazine (HZ) producing poly(urethane-urea). PUD was reinforced with Na+-montmorillonite (Na+-MMT) to yield nanocomposites (CPUD’s) with 1, 3 and 5% of clay. Water was used as swelling agent to make the basal space of silicate layers widen without any chemical treatment. According to XRD curves, the nanocomposites showed intercalation of the polymer with respect to the clay, while small angle X ray scattering (SAXS) results showed that some degree of clay exfoliation was present in the produced film. The incomplete exfoliation of the clay proved that a re-aggregation process of the nanocomponents (originally delaminated in the aqueous dispersion) had occurred during film formation. The degree of hydrogen bonding, evaluated by Fourier-transform infrared spectroscopy (FTIR), was used to investigate the effect of clay on the microphase separation of the polyurethane and indicated that the presence of the clay particles changed the structure of the polymer phase domains. PUD exhibited values of tensile strength and elongation at break about 30 MPa and 1400%, respectively. The incorporation of 1 weight % of MMT improved by 230 and 20% the modulus and strength on the polymer respectively, while keeping the elongation at break almost unchanged.

O uso de ardósia em construções tem frequentemente resultado na produção de uma grande quantidade de resíduos particulados que tem pequeno valor mercadológico e grande potencial de danificação do meio ambiente. Neste trabalho, partículas de ardósia foram testadas como agente de reforço em polipropileno. Polipropileno e partículas de ardósia foram misturados em um misturador em diferentes frações. Anidrido maleico foi também usado durante a mistura para induzir modificações no polipropileno que levassem a um aumento na interação entre os componentes. As amostras foram caracterizadas por espectroscopia no infravermelho (FTIR) e microscopia eletrônica de varredura. Materiais contendo 5 e 10% de ardósia produziram amostras com características ópticas semelhantes à rocha original. As análises por FTIR e microscopia eletrônica de varredura sugeriram que as modificações químicas no polipropileno levaram a uma melhoria parcial das interações interfaciais entre as partículas de ardósia e o polímero. Propriedades mecânicas, avaliadas por meio de ensaios de resistência à tração, mostraram que a adição das partículas de ardósia não alterou significativamente a resistência mecânica do polipropileno. Assim sendo, a incorporação de partículas de ardósia em polipropileno surge como uma tecnologia potencial para a produção de sistemas com algumas propriedades mecânicas comparáveis ao polipropileno puro, baixo custo, propriedades ópticas próximas às da ardósia e habilidade de minimizar problemas ambientais decorrentes da presença de resíduos derivados de atividades industriais. The use of slate rock in constructions often results in the production of large amount of residual powder that has very low economical value and can also damage the environment. In this work, slate powder was tested as a reinforcing agent for polypropylene. Polypropylene and slate powder were mixed in different ratios in a mixer. Maleic anhydride was also used during the mixing to induce chemical modification of polypropylene in order to improve interactions between the polymer and the inorganic powder. Samples were characterized by infrared spectroscopy and scanning electron microscopy. Samples obtained by adding 5 and 10 wt. % of slate powder in polypropylene had optical properties close to those of commercial slate. FTIR and electron microscopy results suggested that chemical modification of polypropylene led to a partial improvement on the interfacial interactions between slate powder and the polymer. Mechanical properties evaluated by using tensile tests showed that the slate powder did not affect substantially the mechanical strength of polypropylene. Therefore, the incorporation of slate powder in polypropylene emerges as a potential technology for production of systems with some mechanical properties comparable to pure polypropylene, low cost, optical properties close to pure slate and ability to minimize environment problems caused by the presence of residual powder derived from industrial activities.

Tissue engineering has evolved from the use of biomaterials for bone substitution that fulfill the clinical demands of biocompatibility, biodegradability, non-immunogeneity, structural strength and porosity. Porous scaffolds have been developed in many forms and materials, but few reached the need of adequate physical, biological and mechanical properties. In the present paper we report the preparation of hybrid porous polyvinyl alcohol (PVA)/bioactive glass through the sol-gel route, using partially and fully hydrolyzed polyvinyl alcohol, and perform structural characterization. Hybrids containing PVA and bioactive glass with composition 58SiO2-33CaO-9P2O5 were synthesized by foaming a mixture of polymer solution and bioactive glass sol-gel precursor solution. Sol-gel solution was prepared from mixing tetraethoxysilane (TEOS), triethylphosphate (TEP), and calcium chloride as chemical precursors. The hybrid composites obtained after aging and drying at low temperature were chemically and morphologically characterized through infrared spectroscopy and scanning electron microscopy. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioglass composition ratios affect the synthesis procedure. Synthesis parameters must be very well combined in order to allow foaming and gelation. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm.