Thermosensitive polylactic-acid-based networks

Polylactic-acid-based thermosensitive networks were prepared in a simple way through reversible Diels-Alder reaction. First, hydroxyl-telechelic PLA with well-controlled molar masses were synthesized by ring-opening polymerization of L-lactide using 1,4-butanediol/Sn(Oct)(2) as catalytic system in a solvent-free process. The molar ratio of lactide/initiator was fixed to control the number average molecular weight (M-n). Before the synthesis of the network, a second precursor which is the Diels-Alder adduct was prepared apart for a better control of the Diels-Alder conversion. The thermoreversible networks were then obtained by simultaneous coupling of the hydroxyl-telechelic PLA, Diels-Alder adduct, multi-alcohols such as glycerol and xylitol, and a diisocyanate (H12MDI) through the alcoholysis reaction of isocyanate. The networks' properties were characterized. The cross-linking and de-cross-linking thermal dependence of PLA-based networks was shown by solubility tests at room and high temperatures and by thermo-mechanical analysis. The effect of the node concentration and steric hindrance on the networks' formation and properties was investigated. Low de-cross-linking temperatures were obtained for some materials. (C) 2014 Elsevier B.V. All rights reserved.