RESUMO
A biobased diglycidyl ether of vanillin (DGEVA) epoxy resin was nanostructured by poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-PPO-PEO) triblock copolymer. Due to the miscibility/immiscibility properties of the triblock copolymer in DGEVA resin, different morphologies were obtained depending on the triblock copolymer amount. A hexagonally packed cylinder morphology was kept until reaching 30 wt% of PEO-PPO-PEO content, while a more complex three-phase morphology was obtained for 50 wt%, in which large worm-like PPO domains appear surrounded by two different phases, one of them rich in PEO and another phase rich in cured DGEVA. UV-vis measurements show that the transmittance is reduced with the increase in triblock copolymer content, especially at 50 wt%, probably due to the presence of PEO crystals detected by calorimetry.
RESUMO
Two different methods were employed for the preparation of cellulose triacetate (CTA) based nanocomposites without and with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer and modified with sol-gel synthesised titanium dioxide nanoparticles (TiO2). The hybrid nanocomposites were prepared by solvent casting (SC) and solvent vapour annealing (SVA) methods. The hybrid nanocomposite films obtained by SVA presented smoother surfaces, and consequently, higher gloss values. As for transparency, only the hybrid nanocomposites prepared by SVA remained completely transparent even with high sol-gel content due to the nanostructuration of EPE triblock copolymer. Furthermore, the UV-shielding properties provided by the TiO2 nanoparticles were not modified regardless of the employed preparation method. Finally, the nanocomposites prepared by SVA presented a higher Young's modulus and tensile strength than the SC nanocomposites. The obtained results proved the efficiency of the SVA method to control the relationship between the morphology and the final properties of the hybrid nanocomposite films leading to materials with enhanced surface, optical, and mechanical properties.
RESUMO
Transparent and flexible bionanocomposites with photochromic properties based on cellulose triacetate (CTA) and sol-gel synthesized V2O5 nanoparticles were prepared. Poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer was added to achieve nanostructured materials and simultaneously control the dispersion of synthesized V2O5 nanoparticles. Investigated bionanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), tensile tests, and UV-vis spectroscopy. FTIR results confirmed the presence of hydrogen bonds in the bionanocomposites. The miscibility between components improved with the increase of sol-gel content resulting in a decrease of the Tg and Tm of CTA phase as indicated by DSC results. Addition of EPE triblock copolymer enhanced the photochromic properties of bionanocomposites reducing the time of recovery to the initial state after 5 min of UV light irradiation. The biocompatibility of pure CTA and EPE/CTA blends as well as the photochromic properties provided by synthesized V2O5 nanoparticles make their transparent and flexible bionanocomposites ideal for possible future applications.