Thermosensitive polylactic-acid-based networks

• PLA-based networks were effectively obtained by Diels–Alder reaction.
• Network formation and its reversibility were verified by dynamic mechanical analyses.
• The thermal-reversibility was proved on several cycles.
• The effect of the node density on the reversibility temperatures was evaluated.
• Reversibility temperature approaching the human body one was reached.

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 (Mn). 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.

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