Poly(L-lactide) Nanocomposites Containing Octaglycidylether Polyhedral Oligomeric Silsesquioxane: Prepartion, Structure And Properties

Three species of PLLA-POSS hybrids were prepared by ring-opening polymerization and solution ring-opening polymerization. Their structures and dipersibility were characterized. PLLA/PLLA-POSS nanocomposites were prepared by solution mixing of PLLA-POSS hybrids and neat PLLA. The effect of introducing PLLA-POSS hybrids on thermal properties and isothermal crystallization of PLLA was analyzed. The enhancements of different PLLA-POSS on thermal properties and crystallization rate for PLLA were discussed.PLLA-POSS hybrids were prepared from ring-opening polymerization of L-lactide, POSS, Sn(Oct)2(PLLA-EP0409 hybrids were prepared by solution ring-opening polymerization, with xylene as solvent). FTIR and 1HNMR showed that the PLLA reaced with POSS to form a copolymer. X-ray analysis showed that the POSS in the hybrids were not gathered; they had a good dispersion; and the addition of POSS did not change the microstructure of PLLA.The thermal properties of PLLA/PLLA-POSS were studied by DSC and TGA. DSC analysis showed that the Tg, Tch and Tm of PLLA/PLLA-POSS nanocomposites with PLLA-POSS hybrids content of 1-10% were higher than those of neat PLLA. TGA analysis showed that the introduction of POSS could effectively enhance the thermal stability of PLLA in air atmosphere conditions, and the enhanced effect was not obvious in nitrogen atmosphere conditions. The main factors of enhancing thermal stability properties of PLLA as follow: the Si-O-Si cage structure had a strong rigidity; nano-effectiveness of POSS; hydrogen bonds. We found that POSS with different functional groups had various degrees of enhancement on the thermal properties of PLLA, and in which AM0265 with amino had the best effect, which mainly due to the fact that reaction of POSS and PLLA brought the different groups. The reaction of AM0265 with PLLA brought amide groups, which can form hydrogen bonds with the PLLA, thus AM0265 with amino had the best effect. The isothermal crystallization behaviour was investigated via depolarized light intensity method. It was found that PLLA-POSS hybrids played the role of heterogeneous nucleation and accelerated the crystallization rate of PLLA. POM analysis showed that the PLLA-POSS hybrids made PLLA nucleation density increased, and spherulite became dense. Simultaneously, we found that different PLLA-POSS had different effect on accelerating the crystallization rate of PLLA, among which the PLLA-AM0265 hybrids was the best.