The contribution deals with the comparison of microwave heating and conventional oil bath heating. Silicon dioxide nanoparticles were grafted with MPTMS under acid conditions. Those particles contain a polysiloxane shell with physically adsorbed and chemically bound fractions which can be separated by Soxhlet extraction. The resulting fractions were analyzed with TGA and MALDI‐TOF MS; one to determine the amount of physically adsorbed and chemically bound fractions and the other to get deeper insight into the polysiloxane structures. Furthermore, it was our aim to clarify which fraction can be visualized using MALDI‐TOF MS. Our results show that the ratio of chemically bound MPTMS is higher when using microwave heating, but the same structures in the physically adsorbed fraction were built in both cases.
Superfine wool powder was blended and extruded with poly(propylene) (PP) to produce blend pellets, and the extruded pellets were hot‐pressed into a blend film. SEM photographs show that the powder could be uniformly incorporated with PP after extrusion. FT‐IR spectra shows that no substantial changes occurred in the chemical structure of both PP and wool powder in the blend film. X‐Ray diffraction analysis indicates that crystallinity of the blend film was much higher than that of the wool powder and little lower than that of PP. TG‐tested results indicate that the thermal stability of the blend film declined with an increase in the powder content. Endothermic peaks of the wool powder in the blend film become more obvious as the powder content increases. Mechanical properties decline greatly with an increase in the wool powder content in the blend film.
UV‐cured polysiloxane epoxy coatings containing titanium dioxide were prepared by means of a cationic photopolymerization process. A good distribution of the inorganic filler was achieved within the polymeric network with an average size dimension of around 500 nm. UV‐vis analysis performed on organic dye (methylene blue) stained coatings showed a high efficiency of the titania photocatalytic activity: a complete degradation of the dye on the coating surface is reached after 60 min of UV irradiation without affecting the matrix photo‐degradation.
The spherulitic morphology and growth, overall isothermal crystallization kinetics and hydrophilicity of PBSU were investigated by POM, DSC and WCA measurements in its miscible blends with PEO. The Hoffman‐Lauritzen equation was employed to analyze the spherulitic growth rates of neat and blended PBSU, which show a crystallization regime transition between regime II and III. The overall crystallization rates of PBSU decreased with increasing crystallization temperature, regardless of blend composition, while the crystallization mechanism does not change. A significant improvement in the hydrophilicity of PBSU can be achieved by blending with different weight fractions of PEO, which may be essential for the practical application of PBSU/PEO blends.
New talc/PBAT hybrid materials were prepared through reactive extrusion. First, PBAT was free‐radically grafted with MA to improve the interfacial adhesion between PBAT and talc. Then, the resulting MA‐g‐PBAT was reactively melt‐blended with talc through esterification reactions of MA moieties with the silanol functions from talc. Sn(Oct)2 and DMAP were used as catalysts. Interestingly, the tensile properties for these compatibilized composites were improved due to a better interfacial adhesion between both partners. XPS showed the formation of covalent ester bonds between the silanol functions from talc particles, and the MA moieties grafted onto the polyester backbones.
Natural biomaterials were used to improve the biocompatibility of synthetic biopolymers. PCL was electrospun with natural biopolymers, silk fibroin, and small intestine submucosa. Due to increased electrical conductivity, the diameter of the composite fibers highly depended on the amount of SIS in the polymer solution. PCL/SF/SIS electrospun composites exhibited various synergistic effects, including enhanced mechanical properties and incredibly improved hydrophilicity compared to those of pure PCL and PCL/SF fibers. An initial cell attachment test demonstrated that the interactions between PC‐12 nerve cells and the PCL/SF/SIS composites were more favorable than those between PC‐12 cells and a PCL/SF composite.
The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20° for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material).
Photoresponsive superabsorber particles containing a crosslinked hydrophilic core and a hydrophobic azobenzene‐containing shell were used to prepare photoresponsive polymeric nanomats, thus combining photoresponsivity with high porosity, toughness, and hydrophilicity. The properties of the nanomat composites were highly dependent upon the amount of the superabsorber photochromic particles added. Stable, highly elastic composite nanomats with very high loading (up to ≈50 wt.‐%), good water absorption capacity (4 000%) and relatively good tensile strength (3 MPa) were obtained. The photoresponsive behavior of the composites is demonstrated, which leads to relatively fast water desorption.
Sealed microchannels and simple microfluidic networks with good efficiency and controlled quality of the structures were developed from a photocurable and PCR‐compatible material based on a PEG–methacrylate oligomers mixture. The influence of UV exposure time and of conversion degree on microchannel geometry were studied to obtain structures with controlled depth, vertical sidewalls, and good reproducibility. The roughness inside channels was as low as 50–100 nm, less than that typical of alternative LOC prototyping techniques such as micromilling. Efficient channel sealing was also achieved without using a different sealing material. Surface smoothness and hydrophilicity (static contact angle below 60°) allow spontaneous water flow inside the channels by capillarity without need of surface treatments.
In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.
A recently developed electrohydrodynamic printing method is described that can be used to create ordered structures and complex patterns using coarse processing needles and two polymeric materials. The results highlight the method's potential for direct 3D writing of biomedical polymers and composites for a variety of biomedical applications.
Novel fluoroalkyl end‐capped oligomer/hydroxyapatite nanocomposites have been easily prepared by the reaction of disodium hydrogenphosphate and calcium chloride in the presence of self‐assembled molecular aggregates formed by fluoroalkyl end‐capped oligomers in aqueous media. The fluorinated hydroxyapatite nanocomposites thus obtained were found to exhibit a good dispersibility in a variety of media, and were applied to the surface modification of glass.
A difunctional methacrylate oligomer was mixed with a variable amount of a MAPTMS precursor in the presence of both a radical and a cationic photoinitiator. The simultaneous photolysis of both photosensitive molecules upon UV irradiation allowed the single‐step generation of a type‐II polymethacrylate/polysiloxane nanocomposite film. Methacrylate and methoxysilyl conversions during irradiation were efficiently monitored by FTIR spectroscopy. The inorganic structure of the resulting silica‐based hybrid films was characterized using 29Si solid‐state NMR. Finally, the reinforcement ability of the resulting hybrid films was also assessed by using a unique range of characterization techniques: DMA, scratch test, and nanoindentation.
A new, nickel‐coated graphite resistance‐change‐based method for gel‐point determination for epoxy‐based thermoset resins is presented and compared with DSC and rheological methods. Gelation times determined by this new method are in very good agreement with conventional techniques; this new method is potentially simpler and less time consuming than existing ones.
A fluorinated acrylic resin was synthesized for use as a co‐monomer with a commercially available epoxy resin for UV‐cured interpenetrating polymer network preparation. Hybrid IPN networks were achieved with morphology ranging from a co‐continuous IPN to complete phase separation simply by changing monomer ratios. Highly hydrophobic coatings with good adhesion properties on glass substrates were obtained.
A systematic study of the effects of , flow rate, voltage, and composition on the morphology of electrospun PLGA nanofibers is reported. It is shown that changes of voltage and flow rate do not appreciably affect the morphology. However, the of PLGA predominantly determines the formation of bead structures. Uniform electrospun PLGA nanofibers with controllable diameters can be formed through optimization. Further, multi‐walled carbon nanotubes can be incorporated into the PLGA nanofibers, significantly enhancing their tensile strength and elasticity without compromising the uniform morphology. The variable size, porosity, and composition of the nanofibers are essential for their applications in regenerative medicine.
Chemical and mechanical experiments are reported to elucidate the macroscopic effects of crosslinker length and composition on the thermomechanical response of acrylate‐based SMPs. To this end, EGA‐based formulations underwent a battery of basic tests which revealed that by increasing crosslinker chain length, polymer Tg can be decreased but there will be increases in compliance, step recoverability, and damping in a glassy state. Addition of methacrylate groups can cause increases in swelling, Tg, storage modulus in shorter chains, and greater damping at a rubbery state. All tested polymers exhibited mild hydrophilicity. PEGDA formulations exhibited good recoverability and could be an option for vascular applications.
Porous cellulose acetate butyrate foams with a bimodal cell size distribution were produced using supercritical carbon dioxide as a blowing agent. It is demonstrated that the cell size distribution is tunable, due to the semi‐crystalline nature of the polymer. The resulting morphology will either be homogeneous or bimodal, depending on the depressurization rate. Mercury intrusion porosimetry shows that the produced cellulose acetate butyrate foams possess an open cellular structure.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
Nowadays, silicon represents the most important material used for microelectronic applications. In this paper, both H–Si (111) surfaces and H–Si powders are used to initiate a multifunctional acrylate photopolymerization. The polymers formed are characterized by IR spectroscopy. This should be the way to create either an acrylate polymer coating on a Si wafer or a polymer film containing covalently linked silicon particles.
