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Titanium dioxide (TiO(2)) and TiO(2) glasses containing poly(epsilon-caprolactone) (PCL) up to 24% by weight were obtained by the sol-gel process. Powder compaction was achieved providing heat and pressure. Properties were evaluated through compression and bending tests assisted by X-ray micro-computed tomography imaging. The effects of compaction conditions (i.e. temperature, pressure and duration) on mechanical properties of inorganic/organic composites were investigated. Biocompatibility tests on organic/inorganic composites were carried out using human cells and the MTT assay to determine viability. Results indicated that the mechanical properties (i.e. Young's modulus and maximum strength), in both compression and bending, were a function of the compression moulding conditions. Highest mechanical properties were measured using a compaction pressure of 1500 MPa acting for 90 min at a die temperature of 100 degrees C. The results, however, also suggest that mechanical properties can be tailored by varying the amount of PCL to TiO(2). Strength and stiffness spanned between the properties of spongy and cortical bone. Young's modulus in both compression and bending were higher for PCL amounts of 6%. Instead, higher bending strength values were measured for PCL amounts of 12%. These weight amounts of PCL also provide higher average density values, thus suggesting that the polymeric phase is effective in toughening TiO(2)-based materials. The investigated materials also showed a very good cytocompatibility as indicated by the MTT assay results.

A composite hip prosthesis (CHP) made from poly(ether-imide) reinforced with carbon and glass fibres was manufactured and characterized. The main objective of the study was to evaluate the effect of fibre organization on the mechanical properties of the composite femoral implant and compare with the bone. A stacking sequence of drop-off plies of carbon/glass fibres reinforcing poly(ether-imide) (PEI) constitutes a symmetrical and balanced CHP. The hip was manufactured according to the finite element modelling (FEM) design and using the compression moulding and water-jet technologies. The measured stress-strain data according to tensile, flexural and torsional tests showed agreement with the numerical calculation. Young's modulus and the strength in tension are uniform along the stem axis (40 GPa and 600 MPa, respectively) while the elastic modulus in bending varies from 10 to 60 GPa in the tip-head direction. The composite stem showed a linear load-displacement relation up to 4500 N without breaking. Mechanical behaviour of the CHP is compared to that of a canine femur. Comparison with metal prostheses has also been undertaken. CHPs control stress-strain distributions, and hence the mechanical signals to bone, through a material-structure design.

The kinetic behaviour of dental composite is traditionally studied, considering only the isothermal behaviour, whereas a fast and highly non-isothermal bulk polymerization is expected as a consequence of the significant heat developed due to the exothermic nature of the polymerization reaction. In this paper the photopolymerization kinetics of a commercial dental composite activated by visible light are analysed by differential scanning calorimetry. This technique is applied to determine the degree of reaction and the glass transition temperature of thin layers of the composite matrix, at different isothermal cure temperatures. A phenomenological kinetic model is then integrated with an energy balance in order to analyse the cure behaviour of thicker composite layers. The full model results indicate that non-isothermal cure conditions may be achieved, obtaining higher values for the glass transition temperature and the degree of reaction.

Examination of the cellular components in the inflammatory exudate, which infiltrates subcutaneous cages, can be used to monitor the progress of an inflammatory response to an implanted material. Of particular interest is the study of monocyte/macrophage infiltration into the implanted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In this study, the authors propose a technique using subcutaneous tissue cages in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to different materials. The studies reported here used several materials (thermoplastic and elastomeric polymers) as the challenging agent, to demonstrate whether polymers, chemically different from each other, could differentially activate macrophages to carry out their proinflammatory role more effectively. The materials tested included: poly(etherurethane ureas) (PEUU A'), poly(etherurethane ureas) with a surface active additive, Methacrol, (PEUU C'), polymethylsiloxane (PDMS), polyetherimide, (PEI), and polyetheretherketone, (PEEK). For all tested materials, the maximum numbers of exudate cells and of Ia-positive macrophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia-positive macrophages varied according to the specific polymer present in the cages after 7 days. By day 14, the percentage of Ia-positive macrophages decreased with individual exudates showing 19-32% Ia-positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia-positive macrophages remain the same as compared with control empty cage macrophages.

We studied the hydrogen storage capacity and sorption kinetics of composite materials made of hydride forming metal particles (LaNi5 or Pd, particle size of ∼1 μm) embedded into hydrogen permeable polymers. Experimental analysis shows that (i) the composite material consisting of LaNi5 particles dispersed into polysiloxane (PS-LaNi5) shows negligible H2 storage capacity while the LaNi5 particles dispersed into polyethylene (PE-LaNi5) are completely hydrogenated and (ii) the Pd particles dispersed both into polysiloxane (PS-Pd) and polyvinylpyrrolidone (PVP-Pd) are completely hydrogenated. The interfacial interactions in the PE-LaNi5 and in the PS-Pd composite materials have weak Van der Waals character while strong interfacial interactions occur in the PS-LaNi5 and in the PVP-Pd composites due to the formation of chemical bonds between polymer side groups and the metal surface atoms. Results indicate that in the metal-polymer composites the hydrogenation of the metallic phase cannot be obtained when the interfacial interactions between metal and polymer impede the surface activation of the metallic phase as in the PS-LaNi5 composite. [ABSTRACT FROM AUTHOR]

Owing to aurophilic interactions, linear and/or planar Au(I)-thiolate molecules spontaneously aggregate, leading to molecular gold clusters passivated by a thiolate monolayer coating. Differently from the thiolate precursors, such cluster compounds show very intensive visible fluorescence characteristics that can be tuned by alloying the gold clusters with silver atoms or by conjugating the electronic structure of the metallic core with unsaturated electronic structures in the organic ligand through the sulphur atom. Here, the photoluminescence features of some examples of these systems are shortly described. [ABSTRACT FROM AUTHOR]

The article discusses research which proposed the development of microporous gels through the use of a novel degradation process excluding supercritical fluids. Photopolymerization was used to gel together photosensitive organic-inorganic hybrid sols in a solution based on tetraethyl orthosilicate (TEOS) and organic modified alcoxysilane. The experiment yielded in a microporous gel with a porosity higher than 90%, showing physical properties similar to aerogels made by supercritical drying.

The article examines the process of producing lightweight composite material based on polyurethane and Portland cement. According to the author, the amount of water has a bearing on the morphology and porosity of the foams, thereby also affecting the cement hydration reaction. They report that the mechanical properties of the hybrid composite are influenced by water and cement contents and whether the hydrated cement particles behaved as fillers or whether they interacted to form stronger inorganic networks within the polymeric matrix.

Polymer-embedding of nano-sized indium tin oxide (SnO·In2O3, ITO) produces electrically conductive materials transparent to the visible light at filling factors higher than the percolation threshold. ITO powders are commercially available in an aggregated form and a disaggregation technique was required. Here, aggregated ITO nanoparticles were transformed to colloidal suspension by high-speed stirring. This finely dispersed ceramic suspension was stabilized by addition of poly(vinyl pyrrolidone) and the obtained colloidal system was cast on an optical-grade substrate (PET) to produce electrically conductive-transparent nanocomposite films. Preliminary mechanical and electrical characterization of these films showed good conductivity and interfacial properties. [ABSTRACT FROM AUTHOR]

The article discusses the synthesis of noble-metal/polymer nanocomposites based on thermolysis of homoleptic mercaptides dissolved in polymers. It was observed that clusters were generated when polymers were saturated by noble metal atoms. The microstructure of obtained nanocomposite films was detected by transmission electron microscopy. The research showed that thermolysis method can be effective in making contact-free dispersions of monodisperse nanoparticles in the polymetric matrix.

Abstract: Polyelectrolite hydrogels are crosslinked polymers which display high sorption capacity in water and water solutions. They are widely used in the marked of personal hygiene products, as well as in other biomedical and industrial applications. In the most industrial application they are not biodegradable and prepared starting from acrylamide. In this work, the chemical–physical analysis of a novel class of natural polymers-based microporous superabsorbent hydrogels has been presented. The main focus is the definition of the relationship between material''s chemical–physical structure and its equilibrium sorption properties. The effect of the variation of the degree of crosslinking, the polyelectrolyte nature of the backbone and the hydrogel microporosity on its swelling properties has been analysed, and a good agreement with the theoretical statements has been displayed. The effect of the ionic strength and the pH of the external solution in contact with the hydrogel on its equilibrium sorption properties has also been assessed, and an high sensitivity to these variations was detected for all the tested chemical compositions and physical structures. This work have to be considered part of the efforts towards the reduction of the environmental impact of the large scale consumption industrial polymer based products. [Copyright &y& Elsevier]

Focuses on structure optimization of polycaprolactone foams by using mixtures of carbon dioxide and nitrogen as blowing agents. Differences in transport, chemical and physical properties; Effect on density, cell number density and cell size; Microcellular structure when a mixture of two gases was employed.

Experimental results concerning the synthesis of gold nanoparticles prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer, and UV-visible spectroscopic characterization is presented. Optical spectroscopic data have been correlated tooff-linesize measurements obtained analysing transmission electron micrographs. The gold cluster size, coming from both TEM micrographs and absorbance cubic root, behaved linearly with time above a threshold temperature (70C) according to a deposition-controlled growth mechanism. The plasmon peak halfwidth behaved linearly with inverse particle radius (obtained by TEM), thus proving the hypothesized mechanism growth. The spectroscopic approach allows anon-linegold cluster measurement with possibility to fine control particle size also in the case of a fast process. [ABSTRACT FROM AUTHOR]

A new chemical route for the synthesis of alkanethiol-derivatized gold clusters of controlled size to be used for polymer functionalization has been developed. Gold clusters were prepared by reduction of tetrachloroauric acid with ethylene glycol in presence of poly(N-vinyl pyrrolidone) (PVP) as stabilizer. PVP-protected gold clusters were separated from the reactive mixture by flocculation with acetone; then, they were dissolved in a dodecanethiol/ethanol solution to produce thiol-derivatized Au clusters. Passivated clusters were dispersed in polystyrene/chloroform solutions and high-transparent purple-colored nanocomposite films were obtained by solution casting. This preparative scheme allows to produce polymer-based high-quality optical filters with complete control over the absorption properties. [Copyright &y& Elsevier]

Abstract: Thermo-chromic films based on silver/polystyrene nanocomposites have been prepared by thermal annealing of silver dodecylmercaptide/polystyrene blends at ca. 200°C. The rapid and reversible color switch (from dark-brown to light-yellow) observed at ca. 80°C is probably related to a change in the surface-plasmon absorption of silver nanoparticles that follows to variation of inter-particle distances because of polymer expansion. This polymeric material is potentially useful for a number of functional applications (e.g., optical switches, etc.). [Copyright &y& Elsevier]

The resin film infusion is a promising and low cost technique for the manufacturing of high performance polymer-based composite materials. The processing cycle is usually performed in the autoclave where, under temperature and pressure application, a bagged dry fiber mat is infiltrated by a thermoset polymer resin which is pre-shaped in film form under the fibers. After complete infusion, the consolidation step behaves as in the conventional autoclave process. The infusion process is strongly affected by the permeability of the fiber mat that determines processing issues, such as the cycle time and the complete fiber impregnation and, as a consequence, the performance of the final part. Therefore, the permeability measurement represents one of the most crucial requirements for the design and the optimization of the composite manufacturing by RFI.In this study, a non-conventional technique, based on a fiber optic sensor, has been used to guess the permeability of braided carbon fiber fabrics infiltrated with an epoxy resin by reproducing experimental conditions similar to the RFI industrial manufacturing. The fiber optic sensor, placed through the reinforcement, is able to detect the resin advancement during the infiltration by recording the light intensity drop which takes place as the resin reaches the optical fiber location. This technique represents a valid alternative to the common permeability measurement methods based on flow visualization and in addition, it can be easily used for the real time monitoring of the resin flow advancement during the real processing. [Copyright &y& Elsevier]

Abstract: Hydrogels with good mechanical stability are generally obtained by chemical crosslinking. However, the compounds used as crosslinking agents are often highly toxic, and thus they are not recommended as starting materials in view of an environmentally safe production process and a biocompatible product. In this work chemically crosslinked superabsorbent hydrogels have been synthesized from water solutions of hydroxyethylcellulose (HEC), carboxymethylcellulose sodium salt (CMCNa) and hyaluronic acid (HA), using a non-toxic water-soluble carbodiimide (WSC) as crosslinking agent. Sorption capacity both in water and in water solutions at different ionic strength has been investigated, taking into account the effect of different chemical compositions. Moreover, uniaxial compression tests and dynamic-mechanical measurements on water swollen samples have been performed to probe the elastically effective degree of crosslinking of the polymeric network. In vivo tests on humans for the application of this material as a bulking agent in dietary regimes are in process and preliminary results are encouraging. [Copyright &y& Elsevier]

Abstract: Cooling down from the equilibrium state at different rates reveals the dynamic behavior of glass forming materials. In particular, the dependence of the glass transition region on the cooling rate, q is commonly agreed to contain information regarding the activation energy of the relaxation time, τ. In this work experimental and theoretical aspects of such a relationship have been highlighted. Experimentally, the glass transition zone of amorphous polystyrene films has been investigated over two decades of cooling rate (0.5–50K/min) by using refractive index measurements. The shift of the glass transition temperature and the broadening of the transition zone at increased cooling rate have been characterized. Theoretically, the cooling experiments have been simulated within the integral formulation of the Kovacs–Aklonis–Hutchinson–Ramos (KAHR) model using the Vogel temperature dependence for the relaxation time. The Frenkel–Kobeko–Reiner equation, τq =constant, provided the needed relationship between the experiments and the theory, enabling the evaluation of the relevant parameter of the kinetic model, i.e. the Vogel activation energy and the zero configurational entropy temperature, from the shift of the glass transition temperature with cooling rate. [Copyright &y& Elsevier]

A comparison between two different techniques, namely gel leaching technique (GLT) and a phase inversion technique (PIT),to induce a connected micro-porosity in polymer hydrogels is presented. The gel leaching technique (GLT), applied to an acrylamide hydrogel, consists of carrying the crosslinking reaction within the interstitial space of an agarose gel which, after the setting of the acrylamide hydrogel, is removed by increasing the temperature above its melting point. Following this procedure, an ordered interconnected porous structure is scripted within the acrylamide hydrogel. The phase inversion technique (PIT), applied to a cellulose hydrogel, consists of a quick desiccation of the swollen hydrogel by phase inversion. This is obtained by increasing the swollen sample in a bath of acetone that has a low affinity for the hydrogel but a very high affinity for water. In this case, due to the rapid water removal, a connected but non homogeneous microporosity is achieved. Swelling studies performed on samples obtained by both techniques demonstrated an enhancement of the equilibrium water sorption properties induced by the presence of porosity. However, by comparing the sorption data, the GLT led to a higher enhancement in sorption properties compared to the PIT indicating that beside the degree of porosity also the degree of interconnectivity and the pattern of porosity may control the sorption properties of polymer hydrogels. [Copyright &y& Elsevier]