CRYSTALLIZATION AND PLASTICIZATION OF POLY(L-LACTIDE) (PLLA) WITH SUPERCRITICAL CO_2

摘要

This work investigates the structure and solid-state transitions occurred in PLLA polymers in supercritical carbon dioxide (scCO_2), with the aim to understand formation of microparticles for drug delivery applications. It is shown that PLLA exposed to CO_2 form consistently crystalline structures for both low- and high-molecular weight PLLA. However these structures were susceptible to pressure and temperature changes despite the supposed rigidity of the crystalline lamellar regions. The tendency of PLLA particles to form agglomerates is explained by a combination of a kinetic mechanism during nucleation and a slower process of structural changes occurred after this nucleation stage.