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The quest for sustainable monomers and \"green\" synthetic pathways for the design, fabrication, and modification of various polymers is of great importance and attracts a great deal of attention. Here, a highly versatile and novel bio-based platform was developed by reacting castor oil with propiolic acid for performing amino-yne click reactions. Owing to the electron-deficient nature of the propiolic acid esters, amino-yne click reactions were conducted with ease at room temperature, in the absence of any catalyst and solvent (as long as the amines were low-viscosity liquids at room temperature), and within 5 min. Several primary and secondary amines were shown to react readily with the developed platform. Furthermore, thermosets were prepared by using the propiolated castor oil and multifunctional amines. The prepared thermosets displayed improved thermal properties and elastomer-like mechanical properties.

Conjugated polymer extraction (CPE)-enriched high-purity semiconducting (sc) single-walled carbon nanotubes (SWCNTs) have demonstrated significant application potential as emerging electronic materials. In this work, the interaction of three fluorene-based copolymers with sc-SWCNTs in a toluene solution was systematically compared, covering a wide range of concentrations while considering the phase behavior of the polymer itself. 2D photoluminescence excitation studies show that the polymer containing semiconjugated pyridine units had a higher binding affinity to the SWCNTs due to its twistable main chain conformation. The uniform and high-density SWCNT networks deposited on a silicon wafer have been characterized by SEM and spatial Raman spectroscopy, which reveals ultrahigh sc purity with a metallic tube content less than the parts per million level. The performance of thin-film transistors could be correlated with the structure of wrapping polymers. The threshold voltage shifted with the nitrogen content in their repeat units due to electron donation from the nitrogen atoms. The off-current was reduced with the flexible copolymer, which provided better wrapping and thus limited bundling during network formation.

Recently discovered SARS-CoV-2 caused a pandemic that triggered researchers worldwide to focus their research on all aspects of this new peril to humanity. However, in the absence of specific therapeutic intervention, some preventive strategies and supportive treatment minimize the viral transmission as studied by some factors such as basic reproduction number, case fatality rate, and incubation period in the epidemiology of viral diseases. This review briefly discusses coronaviruses' life cycle of SARS-CoV-2 in a human host cell and preventive strategies at some selected source of infection. The antiviral activities of synthetic and natural polymers such as chitosan, hydrophobically modified chitosan, galactosylated chitosan, amine-based dendrimers, cyclodextrin, carrageenans, polyethyleneimine, nanoparticles are highlighted in this article. Mechanism of virus inhibition, detection and diagnosis are also presented. It also suggests that polymeric materials and nanoparticles can be effective as potential inhibitors and immunization against coronaviruses which would further develop new technologies in the field of polymer and nanoscience.

Fused Deposition Modeling (FDM), is one of the most popular and widely used Additive Manufacturing filament based technology employing materials such as Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Thermoplastic Polyurethane (TPU) and Polylactic Acid (PLA). In this technique, the part is built up layer-by-layer, affecting, both the resolution along the z-axis, and the mechanical properties dependent on the mesostructure, controlled by a large amount of production parameters such as layer thickness, raster orientation, number of contour and air gap. When dealing with functional and structural printed parts, a deep understanding of these tunable building parameters and their influence on the mechanical properties is of the utmost importance and over the years many experimental studies have been carried to investigate this need. This study is intended to explore specimens realized through FDM technique with different combinations of printing parameters to analyse their effect on the mechanical properties of ABS Plus p430. To this aim, tensile and compression specimens, had been designed and tested. Sixteen different types of tensile specimen had been realized by varying four different parameters, namely, layer thickness, part interior style, infill orientation and number of contours. Whereas, the number of compression specimens had been limited to four considering the variation of two parameters: layer thickness and part interior style. Three samples for each specimen had been produced in ABS Plus p430 using a Stratasys Fortus 250mc FDM printer and tested with a universal testing machine through tension and compression tests to analyse the correlation between printing parameters and material properties. Test results had led to important conclusions on the consistency and homogeneity of the mechanical properties and on the variation of the material’s performances in accordance with the different combinations of production parameters.

Subject of Research. The paper presents a technique for prediction of the mechanical properties of polymer materials. An equation is proposed for the highly elastic part of deformation in a differential-mode for one-dimensional polymer structures. The equation establishes that the preceding mechanical impact on deformation material properties is irrelevant. Method. A recursive method for solution of the proposed differential equation not integrable in quadratures was proposed. Tensile diagrams were experimentally obtained for fibers made of highly oriented polymers such as polyamide and polyethylene terephthalate in five loading conditions. The first load consisted in uniform loading of the fiber to rupture. In the other cases, the loading was carried out in three stages: with holding at control points, complete unloading and subsequent loading to rupture. Main Results. An equation for the highly elastic part of the deformation in a differential form is proposed and solved. Tensile diagrams are presented for one-dimensional polymer samples made of polyamide and polyethylene terephthalate up to the rupture values under various loading conditions. It is found that the preceding mechanical impacts do not affect significantly on the sample deformation properties. Samples made of polyamide and polyethylene terephthalate have practically no memory. Thus, the highly elastic part of the deformation relaxes into a stable state. Practical Relevance. The research shows that in an equilibrium state (regardless of the deformation method) each level of mechanical stress corresponds to a certain value of the equilibrium deformation; for a fixed deformation there is a fixed value of stress. The modeling results make it possible to predict the behavior of polymer materials under various operating conditions.

High-purity semiconducting single-walled carbon nanotubes (sc-SWCNTs) are promising for portable and high-sensitivity gas sensors because of their excellent physical and electrical properties. Here, we describe the synthesis of a novel indigo-fluorene-based copolymer (PFIDBoc) that has been designed to selectively enrich sc-SWCNTs with excellent purity (>99.9%) yet contain a latent function in the form of a tert-butoxy (t-BOC)-protected amine that can be later revealed and exploited for carbon dioxide (CO₂) gas sensing. SWCNTs wrapped with the PFIDBoc polymer can be easily converted via an on-chip thermal process to reveal a vinylogous amide moiety with a secondary amine nitrogen within the indigo building block of the copolymer which is perfectly suited for CO₂ recognition. Thin-film transistors and sensors were inkjet-printed onto rigid and flexible substrates, demonstrating the versatility of enriched PFIDBoc-derived sc-SWCNT dispersions. The printed transistors exhibited a mobility up to 9 cm² V⁻¹ s⁻¹ and on/off current ratios >10⁵. We further demonstrate herein a CO₂ sensor for indoor air quality monitoring even in low humidity environments, possessing a linear response with up to ∼5.4% sensitivity and a dynamic range between 400 and 2000 ppm in air with a relative humidity of ∼ 40%.

International audience; Smart emissive materials that can react to external stimuli in a reversible way are challenging to develop and have been the subject of considerable interest. Here, we present a printable hybrid material that can withstand numerous writing-erasing cycles. This material is based on a poly(methyl methacrylate) host matrix embedding by copolymerization of a red NIR phosphorescent metal cluster and a blue green 3-oxindole emitter. Irradiation of the homogeneous and stable hybrid films changes the emission color from white to deep red because of the oxygen perturbed energy transfer from the organic dye to the metal cluster. Because of the low PMMA gas permeability, encrypted data lifetime can be tuned from minutes to days, can be self-erased, and be rewritten at will. This material represents a key stepping stone for anticounterfeiting, optoelectronic, data recording, and many other technologies © 2019 Elsevier Ltd

Polymers constitute a group of materials having a wide-ranging impact on modern pharmaceutical technology. Polymeric components provide the foundation for the advancement of novel drug delivery platforms, inter alia orodispersible films. Orodispersible films are thin, polymeric scraps intended to dissolve quickly when put on the tongue, allowing them to be easily swallowed without the necessity of drinking water, thus eliminating the risk of choking, which is of great importance in the case of pediatric and geriatric patients. Polymers are essential excipients in designing orodispersible films, as they constitute the backbone of these drug dosage form. The type of polymer is of significant importance in obtaining the formulation of the desired quality. The polymers employed to produce orodispersible films must meet particular requirements due to their oral administration and have to provide adequate surface texture, film thickness, mechanical attributes, tensile and folding strength as well as relevant disintegration time and drug release to obtain the final product characterized by optimal pharmaceutical features. A variety of natural and synthetic polymers currently utilized in manufacturing of orodispersible films might be used alone or in a blend. The goal of the present manuscript was to present a review about polymers utilized in designing oral-dissolving films.

The objective of current work is to analyse the influence of different welding techniques and welding parameters on the morphology and mechanical strength of friction stir welds (FSW) in polymers, based on data collected in the literature. In the current work, only articles that provide data on the joint efficiency, or sufficient information to estimate it are considered. The process using conventional tool is presented and compared with new procedures developed for FSW of polymers, such as those using tools with heated stationary shoulder, preheating of the polymer or double-side passage of the tool. The influence of tool rotational speed (w), welding speed (v), tilt angle and geometry of the pin are discussed. This work focuses on the polymers most studied in the literature, polyethylene (PE) and polypropylene (PP). The use of external heating and tools with stationary shoulder proved to be of great importance in improving the surface finish, reducing defects, and increasing the mechanical strength of the welds. The increase in the w/v ratio increased the joint efficiency, especially when using conventional tools on PE. A trend was obtained for conventional FSW, but it was difficult to establish mathematical relationships, because of the variability of welding conditions.

The article discusses the grain morphology of the natural filler from hazelnut and walnut shell flour. It was observed that the geometry of both meals is similar to each other and resembles uneven balls in shape. The heterogeneity and well-developed outer surface of the flour grains allow for filling the voids with the polymer matrix. The analysis of the surface of the SEM images allowed to observe the presence of natural filler flour grains in the entire volume of the produced polymer composites, uneven distribution and small agglomerates, as well as the presence of voids, distributed in the matrix and in the matrix/filler interface. As a result of the visual evaluation of the activity of microorganisms (mycelium) on the surface of the produced polymer composite materials PP/hazelnut and walnut shell flour with a different % share, different fraction, it was found that the best fungistatic effect was shown by the samples marked with the symbol hazelnut at the fraction 315–443 µm. The least fungistatic material was found to be the samples with walnut shell meal filler at the fraction 315–443 µm (F2 and F4), on which the microorganisms achieved significant growth (more than 50% of the test area). The highest value of contact angle was obtained for samples with hazelnut filler fraction 315–443 (C2 and C4), which also confirms its best fungistatic effect.

The intracellular delivery of emerging biomacromolecular therapeutics, such as genes, peptides, and proteins, remains a great challenge. Unlike small hydrophobic drugs, these biotherapeutics are impermeable to the cell membrane, thus relying on the endocytic pathways for cell entry. After endocytosis, they are entrapped in the endosomes and finally degraded in lysosomes. To overcome these barriers, many carriers have been developed to facilitate the endosomal escape of these biomacromolecules. This mini-review focuses on the development of anionic pH-responsive amphiphilic carboxylate polymers for endosomal escape applications, including the design and synthesis of these polymers, the mechanistic insights of their endosomal escape capability, the challenges in the field, and future opportunities.

Nanorods consisting of a polystyrene core and a poly(4-vinylpyridine) shell produced via the self-assembly route of comb-shaped supramolecules exhibit very poor mechanical properties. Adding a sufficient amount of poly(2,6-dimethyl-1,4-diphenyl oxide) introduces entanglements to the PS-core resulting in nanorods with much better properties, which can be used as templates for e.g. transition metal oxide tubes.

Among the recently insulating materials broadly utilized in high voltage outdoor insulation, silicone rubber (SiR) has gotten the foremost consideration. Actually, SiR is becoming an efficient countermeasure to insulator contamination issues. To enhance different properties of polymeric materials, micro- and nanofillers have been used for dielectric applications. In this study, micron-sized titanium dioxide (TiO(2)) and nano-sized TiO(2) fillers were added to the SiR matrix to improve electrical and mechanical properties. Dielectric strength, tensile strength, and elongation at break tests were monitored. Also, a scanning electron microscope was carried out. The samples were prepared by mixing micro-TiO(2) into SiR with the content of 0, 10, 20, 30, and 40 wt% and also mixing nano-TiO(2) into SiR with the content of 0, 1, 3, 5, and 7 wt%. A feed-forward neural network technique was used to estimate the dielectric strength in different conditions and different percentages of fillers. Adding nano TiO(2) filler enhances the electrical and mechanical properties of SiR composites. SiR with 5 wt% nano TiO(2) showed the best improvement in electrical and mechanical properties.

Intermolecular cross-linking is one of the most important techniques that can be used to fundamentally alter the material properties of a polymer. The introduction of covalent bonds between individual polymer chains creates 3D macromolecular assemblies with enhanced mechanical properties and greater chemical or thermal tolerances. In contrast to many chemical cross-linking reactions, which are the basis of thermoset plastics, enzyme catalysed processes offer a complimentary paradigm for the assembly of cross-linked polymer networks through their predictability and high levels of control. Additionally, enzyme catalysed reactions offer an inherently ‘greener’ and more biocompatible approach to covalent bond formation, which could include the use of aqueous solvents, ambient temperatures, and heavy metal-free reagents. Here, we review recent progress in the development of biocatalytic methods for polymer cross-linking, with a specific focus on the most promising candidate enzyme classes and their underlying catalytic mechanisms. We also provide exemplars of the use of enzyme catalysed cross-linking reactions in industrially relevant applications, noting the limitations of these approaches and outlining strategies to mitigate reported deficiencies.

Surface tracking and erosion is an irreversible degradation occurring on the insulator surface, and this can ultimately lead to failure of the insulator. Polymeric materials such as silicone rubber have many advantages; including a superior hydrophobic surface. However, polymers are exposed to ageing and degradation resulting from electrical and environmental stresses. The rotating wheel dip test is adopted to conduct a comparative study of surface conduction on the two insulators. A conventional design has been selected and compared with insulators having textured surface. Monitoring of the shed surface and insulator trunk using an IR camera were carried out to assess the temperature distribution along insulator profiles. A spatial analysis was also performed to identify key features of the two designs. Localised surface conductance measurements are proposed in this study. This helps to understand and distinguish the trends of conductance and its distribution on each surface, helping to predict the future surface degradation associated to each design.

International audience; Sol–gel coatings containing diethylphosphite can efficiently protect polyurethane (PU) foam from fire. However, diethylphosphite can cause an allergic skin reaction and produce toxic fumes during combustion. The purpose of this study was to screen alternative additives to replace diethylphosphite. The screened flame-retardant molecules were phosphorus donors of low toxicity compared with halogenated compounds, such as resorcinol bis(diphenyl phosphate) (RDP) and bisphenol A bis(diphenyl phosphate), and bio-based additives with potential flame-retardant functional groups such as chitosan, adenosine triphosphate, cysteine and tyrosine. UL 94 and mass-loss calorimetry tests were used to examine the reaction to fire of the different formulations, and the most promising formulations were characterized using scanning electron microscopy, strain–stress tests and thermogravimetric analyses coupled with Fourier transform infrared spectrometry. It was observed that RDP is as effective as diethylphosphite in producing flame-retardant coatings. Chitosan and cysteine can also be used, but they need to be mixed with RDP to provide acceptable flame-retardant properties. Mechanical tests showed that the addition of chitosan and cysteine in the coatings increased the Young’s modulus of the PU foam and decreased the tensile strength.

Aromatic moieties containing oligoesters have been synthesized by enzymatic polymerization of AB-type alkylenehydroxybenzoates via different polymerization methods. Oligo(2-hydroxyethoxy benzoate) (OHEBA) was obtained with number average molecular weights (M-n) around 2000 g mol(-1). A low degree of polymerization was achieved or no oligomer formation was observed from the enzymatic reaction of compounds modified by one or more methoxy groups. MALDI-TOF MS analysis suggests that the most dominant species in the resulting HEBA oligomer samples are ester/-OH end groups. The thermal properties of the enzymatically produced oligoesters were fully characterized using DSC, TGA and WAXD as well as rheology studies and have been compared with higher molecular weight polymers prepared by conventional polycondensation reactions from the same p-hydroxy benzoic acid derivative. These semi-crystalline oligomers and polymers were found to be mimicking the thermoplastic aromatic/aliphatic polyester regarding their macromolecular structure and thermal behavior. The molecular weight of the obtained AB-type OHEBA was successfully increased to 13 050 g mol(-1) by using it as a macromolecular monomer in sequential polymerization.

Background: Inspired by structural hierarchies and the related excellent mechanical properties of biological materials, we created a smoothly graded micro- to nanoporous structure from a thermoplastic polymer.Results: The viscoelastic properties for the different pore sizes were investigated in the glassy regime by dynamic flat-punch indentation. Interestingly, the storage modulus was observed to increase with increasing pore-area fraction.Conclusion: This outcome appears counterintuitive at first sight, but can be rationalized by an increase of the pore wall thickness as determined by our quantitative analysis of the pore structure. Therefore, our approach represents a non-chemical way to tune the elastic properties and their local variation for a broad range of polymers by adjusting the pore size gradient.

Massive blood loss is responsible for numerous causes of death. Hemorrhage may occur on the battlefield, at home or during surgery. Commercially available biomaterials may be insufficient to deal with excessive bleeding. Therefore novel, highly efficient hemostatic agents must be developed. The aim of the following research was to obtain a new type of biocompatible chitosan-based hemostatic agents with increased hemostatic properties. The biomaterials were obtained in a quick and efficient manner under microwave radiation using l-aspartic and l-glutamic acid as crosslinking agents with no use of acetic acid. Ready products were investigated over their chemical structure by FT-IR method which confirmed a crosslinking process through the formation of amide bonds. Their high porosity above 90% and low density (below 0.08 g/cm3) were confirmed. The aerogels were also studied over their water vapor permeability and antioxidant activity. Prepared biomaterials were biodegradable in the presence of human lysozyme. All of the samples had excellent hemostatic properties in contact with human blood due to the platelet activation confirmed by blood clotting tests. The SEM microphotographs showed the adherence of blood cells to the biomaterials&rsquo, surface. Moreover, they were biocompatible with human dermal fibroblasts (HDFs). The biomaterials also had superior antibacterial properties against both Staphylococcus aureus and Escherichia coli. The obtained results showed that proposed chitosan-based hemostatic agents have great potential as a hemostatic product and may be applied under sterile, as well as contaminated conditions, by both medicals and individuals.

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Regeneration of materials properties through surface regeneration can extend the lifetime of devices and is still an emerging field of research. (Self-)regenerating antimicrobial polymer surfaces can help to fight biofilm formation and related bacterial infections. In this paper, four different polymer multilayer designs for the regeneration of antimicrobial surfaces by layer shedding are presented. The multilayer architectures consist of 100–200 nm thick, discrete polymer layers. They are made from poly(guanidinium oxanorbornene) networks as the antimicrobial component, and different interlayers made from degradable poly(adipic anhydrides), depolymerizable poly(ethyl glyoxylate), or water-soluble poly(acrylamide). Layer shedding is designed to occur after hydrolysis, dissolution, or depolymerization under simulated physiological conditions. The multilayer fabrication and disassembly is monitored by fluorescence microscopy, ellipsometry, Fourier transform infrared (FT-IR) spectroscopy, and atomic force microscopy. By testing the antimicrobial activity of the restored surfaces, their functional integrity after layer shedding is confirmed.

Multi-polymeric nanocomposite hydrogels with multi-functional characteristics have been engineered with high interest around the globe. The ease in fine tunability with maintained compliance makes an array of nanocomposite biomaterials outstanding candidates for the biomedical sector of the modern world. In this context, the present work intends to tackle the necessity of alternatives for the treatment of diabetic foot ulcers through the formulation of nanoclay and/or polymer-based nanocomposite hydrogels. Laponite RD, a synthetic 2-D nanoclay that becomes inert when in a physiological environment, while mixed with water, becomes a clear gel with interesting shear-thinning properties. Adding Laponite RD to chitosan or gelatin allows for the modification of the mechanical properties of such materials. The setup explored in this research allows for a promising polymeric matrix that can potentially be loaded with active compounds for antibacterial support in foot ulcers, as well as enzymes for wound debridement.

Innovation in the field of protected crops represents an argument of great applied and theoretical research attention due to constantly evolving technologies and automation for higher quality flower and vegetable production and to the corresponding environmental and economic impact. The aim of this paper is to provide an analysis of some thermomechanical properties of rigid polymeric laminates for greenhouses claddings, including innovative tests such as the thermographic ones. Four types of laminates have been analysed: two polycarbonates, a polymethylmethacrylate and a polyethylene terephthalate (PET). The tests gave interesting results on different important properties, such as radiometric properties, limit stresses, strains and ductility. Moreover, a direct comparison of infrared images and force elongation curves gave important information on the relation of the (localised or homogeneous) damage evolution, with both an applicative and theoretical implication. Finally, even if to the authors knowledge at present there are no examples of using PET for covering greenhouses, the results of this paper indicates the thermomechanical and radiometric characteristics of this material make it interesting for agricultural applications.

The separation process is very important in a variety of scientific fields, especially in biochemistry and biotechnology. The separation performance of a method can be determined by the separation time and the purity of the separated molecule, which is directly proportional with the ligand chosen for the target molecule. The separation time is actually a very important step for the cost and the time-dependent analysis, especially in medical applications. Magnetic separation is a very advantageous technique because it eliminates the time-consuming sample preparation and centrifugation steps. However, the magnetic performance of adsorbent may not be strong enough to respond the magnetic force applied externally. Therefore, in nanoparticle studies, magnetic performance of nanoparticles is highly important. In this study, the magnetic performance of polymeric microparticles synthesized using different magnetic cores (Fe2O3&Fe3O4, Fe&Ni, Ni&Co, Fe&Ni&Co) with a solid support, HEMA (2-hydroxyl ethylmethacrylate), and a functional monomer, AdeM (adenine methacrylate), were compared. Some other properties such as size, zeta potential, surface morphology, etc. were also studied.

The present paper studies the effects of the additions between 3.00 and 7.00 wt% of additive Granic 422 instead of polypropylene on polymeric tapes properties as color difference, structure and tensile parameters. Micro-structural analysis revealed additional agglomerations of calcium carbonate particles on the surfaces of the tapes after application of new portions of the variable additive. Composition-property relations showing the changes in properties of tapes were suggested. For increase in color difference of the tapes from zero to 0.18, a logarithmic relation was used. For other indices, the linear relations were proposed. On the basis of the relations, the positive changes of 2.0-2.7% in macro-structural parameters (width, thickness, linear density) and negative changes of 2.1-8.8% in tensile characteristics were obtained.

A sulfur-rich copolymer is synthesized via a sustainable, eco-friendly approach using two major wastes namely, elemental sulfur (industrial waste) and cardanol (agro waste) and its application as cathode active material in Li-S battery. The presence of chemically bound sulfur (90 wt%) utilising cardanol (10 wt%) derivative in the copolymer (S90) showed a reduction in the active material dissolution into the electrolyte. In addition, the organic sulfur units get dispersed into the insoluble/insulating Li-2 S-2/Li2S phase and thus found to suppress their irreversible dep-osition. Li-S battery based on S90/multi-walled carbon nano-tubes (MWCNT) (10 wt%) exhibited a reversible capacity of 1302 mAh g(-1) at 2nd cycle, maintaining a high reversible capacity of 928 mAh g(-1) after 70 cycles at a relatively constant coulombic efficiency over 99% at current rate of 200 mA g(-1). At 1000 mA g(-1) current rate, the composite cathode delivered a reversible capacity of 697 mAh g(-1) at 2nd cycle and retained 75% of its initial capacity even after 180 cycles.

This study examines the preparation of electrically conductive polymer networks based on furan-functionalised polyketone (PK-Fu) doped with multi-walled carbon nanotubes (MWCNTs) and reversibly crosslinked with bis-maleimide (B-Ma) via Diels-Alder (DA) cycloaddition. Notably, the incorporation of 5 wt.% of MWCNTs results in an increased modulus of the material, and makes it thermally and electrically conductive. Analysis by X-ray photoelectron spectroscopy indicates that MWCNTs, due to their diene/dienophile character, covalently interact with the matrix via DA reaction, leading to effective interfacial adhesion between the components. Raman spectroscopy points to a more effective graphitic ordering of MWCNTs after reaction with PK-Fu and B-Ma. After crosslinking the obtained composite via the DA reaction, the softening point (tan(&delta, ) in dynamic mechanical analysis measurements) increases up to 155 &deg, C, as compared to the value of 130 &deg, C for the PK-Fu crosslinked with B-Ma and that of 140 &deg, C for the PK-Fu/B-Ma/MWCNT nanocomposite before resistive heating (responsible for crosslinking). After grinding the composite, compression moulding (150 &deg, C/40 bar) activates the retro-DA process that disrupts the network, allowing it to be reshaped as a thermoplastic. A subsequent process of annealing via resistive heating demonstrates the possibility of reconnecting the decoupled DA linkages, thus providing the PK networks with the same thermal, mechanical, and electrical properties as the crosslinked pristine systems.

This work reports on ABA triblock copolymer microparticles encoded with CdSe/CdS core-shell quantum dots (QDs) realized by electrospraying. This method allows for simple but efficient embedding of QDs in polymer beads while retaining the fluorescent properties of the original QDs. The creation of poly(styrene-ethylene-butylene-styrene) (SEBS) monodisperse spherical microparticles with a tunable morphology for applications of the final QD loaded product is attainable via solvent variation. By varying the selectivity of the solvent for one of the distinct blocks in the polymer, the final particle morphology can be selectively altered while maintaining the same overall process conditions, allowing to tailor the particles from homogeneously flat in a non-selective solvent to dense spherical particles in an endblock selective solvent system. The mechanism responsible for this transition in morphology could be related to differences in mass transfer in the droplets and thus solvent evaporation rates arising from particular microphase structures. Finally, fluorescence characteristics of the final QD embedded polymer particles and photodegradation stability are investigated by spectrophotometry and are compared to the temporal evolution of the original quantum dots, indicating significant stability improvement and well dispersed QDs in an optimized polymer matrix morphology. ispartof: Macromolecular Materials And Engineering vol:305 issue:2 status: published

Cells take decisions on their responses depending on the stimuli received by the surrounding extracellular environment, that provides the essential cues at the micro and the nano-lengthscales required for adhesion, orientation, proliferation and differentiation. In this study, discontinuous microcones on silicon (Si) and continuous microgrooves on polyethylene terephthalate (PET) substrates were fabricated via ultrashort-pulsed laser irradiation at various fluences, resulting in microstructures with different roughness and geometrical characteristics. The topographical models attained were specifically developed to imitate the guidance and alignment of Schwann cells for oriented axonal regrowth, towards nerve regeneration. At the same time, positive replicas of the silicon microstructures formed were successfully reproduced, via soft lithography, on the biodegradable polymer poly(lactide-co-glycolide) (PLGA). The anisotropic continuous (PET) and discontinuous (PLGA replicas) microstructured polymeric substrates were assessed in terms of their influence on the Schwann cells responses. It is shown that the developed micropatterned substrates enable control over the cellular adhesion, proliferation and orientation and are thus useful to engineer cell alignment in vitro. This property could be potentially useful in the fields of neural tissue engineering and for dynamic microenvironment systems that simulate in vivo conditions.

The aim of the present work is to evaluate the impact of pure palm biodiesel fuel (B100) and biodiesel blends with 0.32% oleic, palmitic, acetic, myristic, and stearic acids on the properties of some polymeric materials used commonly in the manufacture of auto parts such as the polyamide 66 (PA66), polyoxymethylene (POM), and high-density polyethylene (HDPE). The effects of the B100 and B100–acid blends on polymeric materials were examined by comparing changes in the gain/loss of mass and by measuring the hardness, the impact strength, and the tensile strength of the materials at the end of the exposure. The characterization of the polymers was carried out before and after exposure by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). After the immersion in B100–acids blends, the HDPE exhibited an increase in mass of 5%, which was very similar in all blends. The PA66 showed a small decrease in weight (2% approx.) in all mixtures. The POM presented an increase in the percentage of weight in the mixture of B100 with acetic acid of 0.3%. A decrease was observed in the crystallinity of the HDPE when exposed to blends of B100–acids. This behavior may be associated with a plasticizing effect in the HDPE exposed to the blends. The mechanical properties of POM and HDPE showed no significant changes after immersion in the fuels. On the other hand, PA66 exhibited a significant decrease in maximum stress value after immersion in B100, B100–oleic acid and B100–palmitic acid blends. The variation of the mechanical properties of the PA66 after exposure to B100 was potentiated by addition of organic acids. The assessed polymers did not undergo appreciable changes in the chemical structure of the samples after immersion in the fuels, so the variation in the mechanical properties could be explained by physical absorption of the fuel into the polymers.

In this study, a series of biodegradable polyurethane films (PU-Fs) is prepared by step-growth polymerization of hydroxylated soybean oil (SBO-OH) and L-lysine diisocyanate ethyl ester (L-LDI) that are renewable-based difunctional building blocks. The influence of loading ratio by weight (SBO-OH/L-LDI (w/w) = 1:0.5; 1:1 and 1:1.5) on the biodegradable, mechanical and thermal properties of final PU-Fs is systematically investigated. In the first step, epoxy groups of epoxidized soybean oil are converted to corresponding hydroxyl functionalities to react with the diisocyanate groups of L-LDI via film casting method at room temperature. The obtained PU-Fs with higher L-LDI loading exhibit higher thermal and mechanical properties as well as more hydrophobic characteristic compared to others. Moreover, biodegradability of resulting PU-Fs is also studied using hydrolytic and enzymatic degradation experiments. Noteworthy, it is found that around 50 and 60% of PU-Fs are degraded by enzymatic and hydrolytic experiments after 12 weeks.

The combined effects of illumination and thermal annealing on the morphological stability and photodimerization in polymer/fullerene thin films are examined. While illumination is known to cause fullerene dimerization and thermal stress their dedimerization, the operation of solar cells involves exposure to both. The competitive outcome of these factors with blends of phenyl‐C61‐butyric acid methyl ester (PCBM) and polystyrene (PS), supported on PEDOT:PSS is quantified. UV–vis spectroscopy is employed to quantify dimerization, time‐resolved neutron reflectivity to resolve the vertical composition stratification, and atomic force microscopy for demixing and coarsening in thin films. At the conventional thermal stress test temperature of 85 °C (and even up to the PS glass transition), photodimerization dominates, resulting in relative morphological stability. Prior illumination is found to result in improved stability upon high temperature annealing, compatible with the need for dedimerization to occur prior to structural relaxation. Modeling of the PCBM surface segregation data suggests that only PCBM monomers are able to diffuse and that illumination provides an effective means to control dimer population, and thus immobile fullerene fraction, in the timescales probed. The results provide a framework for understanding of the stability of organic solar cells under operating conditions.

The global consumption of plastic continues to increase, and plastic recycling is highlighted as crucial for saving fossil resources and closing material loops. Plastic can be made from different polymers and contains a variety of substances, added intentionally to enhance the plastic's properties (metals added as fillers, colourants, etc.). Moreover, plastic can be contaminated during use and subsequent waste management. Consequently, if substances and contaminants are not removed during recycling, potentially problematic substances might be recycled with the targeted polymers, hence the need for quantitative data about the nature and presence of these substances in plastic. Samples of selected polymers (PET, PE, PP, PS) were collected from different origins; plastic household waste, flakes/pellets of reprocessed plastic from households and industry, and virgin plastic. Fifteen selected metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, Sb, Ti, Zn) were quantified and the statistical analysis showed that both the polymer and origin influenced the metal concentration. Sb and Zn were potentially related to the production stage of PET and PS, respectively. Household plastic samples (waste and reprocessed) were found to contain significantly higher Al, Pb, Ti and Zn concentrations when compared to virgin samples. Only the concentration of Mn was reduced during washing, suggesting that parts of it was present as physical contamination. While most of the metals were below legal limit values, elevated concentrations in reprocessed plastic from households, aligned with increasing recycling rates, may lead to higher metal concentrations in the future.

An eco-friendly approach towards furanic-aliphatic polyesters as sustainable alternatives to aromatic-aliphatic polyesters is presented. In this approach, biobased dimethyl 2,5-furandicarboxylate (DMFDCA) is polymerized with various (potentially) renewable aliphatic diols via Candida antarctica Lipase B (CALB)-catalyzed polymerization using a two-stage method in diphenyl ether. A series of furanic-aliphatic polyesters and oligoesters is successfully produced via enzymatic polymerization. Some products reach very high (M-w) over bar (weight average molecular weight) values of around 100 000 g mol(-1). Studies on the effect of the diol structure on the enzymatic polymerization indicate that CALB prefers long-chain alkane-alpha,omega-aliphatic linear diols containing more than 3 carbons. We also found that the molecular weights of the obtained furanic-aliphatic polyesters increase steadily with the increase of reaction temperature from 80 to 140 degrees C. MALDI-ToF MS analysis reveals that five polyester species may be present in the final products. They were terminated with the ester/-OH, ester/ester, -OH/-OH, no end groups (cyclic), and ester/aldehyde groups, respectively. Furthermore, the structure-property relationships were studied by comparing the crystalline/thermal properties of a series of relevant furanic-aliphatic polyesters.

Recently, new methods have been developed for the utilization of elemental sulfur as a feedstock for novel polymeric materials. One promising method is the inverse vulcanization, which is used to prepare polymeric structures derived from sulfur and divinyl comonomers. However, the mechanical and electrical properties of the products are virtually unexplored. Hence, in the present study, we synthesized a 200 g scale of amorphous, hydrophobic as well as translucent, hyperbranched polymeric sulfur networks that provide a high thermal resistance (>220 °C). The polymeric material properties of these sulfur copolymers can be controlled significantly by varying the monomers as well as the feed content. The investigated comonomers are divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIB). Plastomers with low elastic content and high shape retention containing 12.5%–30% DVB as well as low viscose waxy plastomers with a high flow behavior containing a high DVB content of 30%–35% were obtained. Copolymers with 15%–30% DIB act, on the one hand, as thermoplastics and, on the other hand, as vitreous thermosets with a DIB of 30%–35%. Results of the thermogravimetric analysis (TGA), the dynamic scanning calorimetry (DSC) and mechanical characterization, such as stress–strain experiments and dynamic mechanical thermal analysis, are discussed with the outcome that they support the assumption of a polymeric cross-linked network structure in the form of hyper-branched polymers.

In this work, fibre Bragg gratings (FBGs) were inscribed in two different undoped poly- (methyl methacrylate) (PMMA) polymer optical fibres (POFs) using different types of UV lasers and their inscription times, temperature and strain sensitivities are investigated. The POF Bragg gratings (POFBGs) were inscribed using two UV lasers: a continuous UV HeCd @325 nm laser and a pulsed UV KrF @248 nm laser. Two PMMA POFs are used in which the primary and secondary preforms (during the two-step drawing process) have a different thermal treatment. The PMMA POFs drawn in which the primary or secondary preform is not specifically pre-treated need longer inscription time than the fibres drawn where both preforms have been pre-annealed at 80 °C for 2 weeks. Using both UV lasers, for the latter fibre much less inscription time is needed compared to another homemade POF. The properties of a POF fabricated with both preforms thermally well annealed are different from those in which just one preform step process is thermally treated, with the first POFs being much less sensitive to thermal treatment. The influence of annealing on the strain and temperature sensitivities of the fibres prior to FBG inscription is also discussed, where it is observed that the fibre produced from a two-step drawing process with well-defined pre-annealing of both preforms did not produce any significant difference in sensitivity. The results indicate the impact of preform thermal pre-treatment before the PMMA POFs drawing, which can be an essential characteristic in the view of developing POF sensors technology.

The ultrasound-assisted self-assembly and cross-linking of lysozyme at the water-air and water-perfluorohexane interfaces are shown to produce lysozyme-shelled hollow microbubbles (LSMBs) and microcapsules (LSMC), respectively. The arrangement of lysozyme at the air-liquid or oil-liquid interfaces is accompanied by changes in the bioactivity and conformational state of the protein. The interaction of LSMB and LSMC with human breast adenocarcinoma cells (SKBR3) is studied. LSMB and LSMC are phagocyted by cells within 2 h without exerting a cytotoxic activity. The cellular internalization kinetics of LSMB and LSMC and the effects on cell cycle are evaluated using flow cytometry. Evidence for the internalization of microparticles and degradation within the cell are also monitored by confocal and scanning electron microscopic analyses. The integrity of cell membrane and cell cycle is not affected by LSMBs and LSMCs uptake. These studies show that the positively charged LSMB and LSMC are not cytotoxic and can be readily internalized and degraded by the SKBR3 cells. LSMBs and LSMCs show a different uptake kinetics and intracellular degradation pattern due to differences in the arrangement of the protein at the air-liquid or oil-liquid interfaces. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials.

The polymerisation of furan monomers and the exploitation of some of the chemical peculiarities of the furan heterocycle have generated a wide diversity of macromolecular materials based on renewable resources. In particular, the application of the DA cycloaddition to the macromolecular chemistry opened new ways to synthesize materials with unique properties, such as self-mendability and network recyclability. In this study, non-linear polycondensations between di- and tri-functional furan (A(n)) and maleimide (B-m) monomers by means of the DA reaction are presented. The use of complementary monomers bearing more than two functionalities led to highly crosslinked structures under appropriate stoichiometric conditions, and thus, can be applied in the preparation of \"mendable\" materials.