STEREOCOMPLEX CRYSTALLIZATION OF POLYLACTIC ACID (PLA) AND APPLICATIONS

摘要

Poly (lactide) (PLA) is a plant-derived polymer that has been intensively investigated because it is biodegradable, producible from renewable resources, nontoxic to the human body and the environment, and can be decomposed in natural environment. PLA has three isomeric forms, i.e. Poly (L-lactide) (PLLA), Poly (D-lactide) (PDLA), and Poly (racemic-lactide) (PDLLA), which display a wide variety of properties. Stereocomplexation can occur between PLLA and PDLA either in solution or in a solid state, which results in the formation of a stereocomplex crystallite (sc-crystallite) different from homo-crystallite of either PLLA or PDLA. The sc-crystallite endows PLA-based materials higher mechanical performances, thermal resistance, hydrolysis resistance, thus opening a new avenue to produce various types of biodegradable materials through tailoring the interaction. In this presentation, I will highlight some of our research in the areas: 1. The high thermal mechanical property observed in sc-crystallites could be attributed to the formation of extra non-conventional" hydrogen bond which lead to a more stable sc-crystal structure. 2. PLA nanocomposites formed by stereocomplexation of nano-filler-g-PDLA with commercial PLLA lead to high crystallinity of the resulting nanocomposites, low activation energy and also ensure a better interfacial interaction between nano-fillers and matrix. 3. Incorporation of rubber phase in PLA via copolymerization and the formation of sc-crystallite could lead to better mechanical property of PLA . Furthermore, with judicial design of interface, the PLA exhibits simultaneous enhancement in strengthen and toughness, overcoming the conflict normally observed in polymer composites. 4. Stereocomplexation of PDLA and PLLA could also be exploited to develop stimuli-responsive micelle or supramolecular hydrogel, which exhibit lower critical micelle concentration and gelation concentration, and could be potentially be used for biomedical applications.