Copolymerization of azide-containing carbonate with lactide and post functionalization

Abstract

The intention of this work was to study the polymerization of a cyclic carbonate monomer bearing one azido group, i.e. 2-(azidemethyl)-2-methyltrimethylene carbonate (AMTC), to disclose the characteristics of the resulted polymers and to explore the feasibility of their post-functionalization with alkynyl compounds via Click reaction. Homopolymerization of AMTC was first studied using stannous octoate (Sn(Oct)2) as the catalyst and dodecanol as the initiator, which had the characteristic of active polymerization. Copolymerization of AMTC with L-lactide (L-LA) was then investigated under the same reaction condition, in which L-LA exhibited higher reactivity than AMTC. The reactivity of AMTC was low not only in its homopolymerization but also in its copolymerization with L-LA, while the conversion of AMTC increased by extending the reaction time. The copolymer P(AMTC-co-LLA) (PLAC) had the semicrystalline characteristic due to the relative long block-like segments of PLLA ( $$ {\overline{L}}_{\mathrm{L}}=35.5 $$ ). Based on these results, copolymerization of AMTC with L-LA using PEG4K as macroinitiator was further studied to afford PLAC-PEG-PLAC copolymers. The copolymerization could be well controlled at low ratio of [M]0/[I]0 (from 10 to 50) and molar fraction of AMTC in feed (fAMTC = 0.1, 0.2). The pendent azido groups of PLAC-PEG-PLAC could undergo post-functionalization through azide-alkyne click reaction easily and efficiently.