No abstract

All-silica beta zeolite, synthesized by conventional hydroxide route, usually possesses small crystal size of a few hundred nanometers but poor hydrophobicity, whereas the fluoride-mediated one exhibits to be highly hydrophobic but microsized. To obtain nanosized all-silica beta zeolite with excellent hydrophobicity, an innovative and efficient hydrothermal route via interzeolite transformation for synthesizing all-silica beta zeolite is proposed in present study. With the assistance of beta seeds and tetraethylammonium hydroxide as the structure-directing agent, siliceous beta zeolite is well-crystallized at a high solid yield via dissolution-recrystallization of all-silica ITQ-1 crystals at an extremely low water content (HO/SiO molar ratio of 1). The obtained all-silica beta crystals are composed of 30-70 nm nanoparticles and highly hydrophobic just next to siliceous beta-F zeolite synthesized by environmentally unfriendly fluoride route, which is derived from relatively small amounts of internal defect sites. Thus, this beta zeolite is superior to other pure silica beta zeolites in the adsorption of large-sized volatile organic compounds (VOCs), which is mainly attributed to its high total pore volume and specific surface area as well as excellent hydrophobicity.

Optically active polymers with main-chain helical chiralities have attracted long-standing interest for their wide potential applications in asymmetric synthesis, molecular recognition, and photoelectrical materials.

Poly (L-lactide) (PLLA) blends with various nucleators were prepared by melt processing. The effect of different nucleators on the crystallization behavior and heat resistance as well as thermomechanical properties of PLLA was studied systematically by differential scanning calorimetry, X-ray diffraction, heat deflection temperature tester, and dynamic mechanical analysis. It was found that poly(D-lactide), talcum powder (Talc), a multiamide compound (TMC-328, abbreviated as TMC) can significantly improve the crystallization rate and crystallinity of PLLA, thus improving thermal-resistant property. The heat deflection temperature of nucleated PLLA can be as high as 1508C. The storage modulus of nucleated PLLA is higher than that of PLLA at the temperature above T g of PLLA. Compared with other nucleating agents, TMC was much more efficient at enhancing the crystallization of PLLA and the PLLA containing TMC showed the best heat resistance.