Title
Molecular and morphological characterization of poly(L-lactic acid-co-glycolic acid) P(L-LA/GA) copolymers prepared by Azeotropic distillation
Author
Mariana Gutiérrez-Sánchez, Francisco Javier Medellín-Rodríguez, Laura Ivone, Silva-de- la- Cruz
Year
2016
Journal
Journal of Polymer Research
Abstract
The synthesis and molecular/morphological characterization of poly(L-lactic acid-co-glycolic acid) P(L-LA/GA) copolymers were investigated. The optimum reaction conditions were first determined by azeotropic distillation polymerization of poly(L-lactic acid) P(L-LA) homopolymers. Once the best reaction conditions were determined, the P(L-LA/GA) copolymers were synthesized by increasing the glycolic acid (GA) proportion in the reaction mixture from 0 to 7.5 mol%. The 13C NMR technique allowed inferring the formation of a copolymer with increasing segmental GA characteristics. These last with the potential to be rejected from the main crystals, assumption that was supported by the convergence of the crystallization and melting temperatures as the molar ratio of GA increased. The diffraction patterns of the copolymers demonstrated the gradual formation of α-α” crystal blends with the GA content and the crystallization and meting results allowed conclude that the increasing number of GA units in the main chain was related to molecular rejection, which resulted in a secondary exclusion phase, the major contribution to melting at the first melting endotherm. This behavior was in correlation with the step-like crystallization and melting mechanism previously proposed for high temperature engineering polymers.
Instrument
J-810
Keywords
Circular dichroism, Stereochemistry, Polymers