Premium
Poly(lactic acid) Synthesis in Solution Polymerization
Author(s) -
Marques Dina A.S.,
Jarmelo Susana,
G. Baptista Cristina M.S.,
Gil M.H.
Publication year - 2010
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201051010
Subject(s) - polymerization , monomer , polymer , lactic acid , polymer chemistry , materials science , thermal stability , chemical engineering , chemistry , organic chemistry , composite material , biology , bacteria , engineering , genetics
The step‐growth polymerization of L‐lactic acid in solution was studied in this work. In order to attain a polymer with high molecular weight, the water formed during the polymerization must be continuously removed. The use of organic solvents with high boiling point, drying agents and reduced pressure led to poly(lactic acid) (PLA) with high molecular weight, directly from the monomer. Tin (II) chloride dihydrate, SnCl 2 .2H 2 O, was the best of the catalysts tested as it allowed achieving PLA with a molecular weight close to 80 000 g.mol −1 . However, the stereoregurarity control is a severe problem in PLA synthesis by step‐growth due to transesterification reactions, which lead to an inversion of the conformation and a decrease of the optical purity of the polymer. Specific rotation measurements were used in this work and showed to be a powerful technique to evaluate the racemization extent. The thermal stability of the PLA samples was evaluated by DSC which exhibits a thermal behaviour similar to the commercial Polylactide.