Effect of nanoparticle SiO2 grafted poly (methyl methacrylate) on poly(l-lactic) acid crystallization

c-Perpendicular Orientation of Poly(ʟ-lactide) Films

Poly(ʟ-lactide) (PLLA) films, even of high thickness, exhibiting co-crystalline and crystalline α phases with their chain axes preferentially perpendicular to the film plane (c_⊥ orientation) have been obtained. This c_⊥ orientation, unprecedented for PLLA films, can be achieved by the crystallization of amorphous films as induced by low-temperature sorption of molecules being suitable as guests of PLLA co-crystalline forms, such as N,N-dimethylformamide, cyclopentanone or 1,3-dioxolane. This kind of orientation is shown and quantified by two-dimensional wide-angle X-ray diffraction (2D-WAXD) patterns, as taken with the X-ray beam parallel to the film plane (EDGE patterns), which present all the hk0 arcs centered on the meridian. PLLA α-form films, as obtained by low-temperature guest-induced crystallization, also exhibit high transparency, being not far from those of the starting amorphous films.

Synthesis and characterization of highly oxidative resistant silicon–acetylene hybrid resin grafted with modified mesoporous silica

This study focused on the preparation and characterization of silicon–acetylene resin by means of grafting functionalized mesoporous silica. (3-Aminopropyl) triethoxysilane was grafted to silica surface through the hydrolysis reaction to yield mesoporous silica functionalized with (3-Aminopropyl) triethoxysilane (MA). These MA nanoparticles were transferred to the chain of silicon–acetylene resin, poly(m-dietheynylbenzene-methylsilane) (PSA) to yield PSA-g-MA, with the help of the reaction of hydrochloric acid removal. PSA-g-MA was totally characterized by Fourier transform infrared spectroscopy, energy dispersive spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscope, transmission electron microscope, and nuclear magnetic resonance, which certified the success of silica modification and functionalized nanoparticles grafted to chain of PSA. The char content of PSA-g-MA reached to 45% at 1000°C under air atmosphere, and the residual weight was increased by nearly 10%, compared with the unmodified PSA.