Synthesis of Biomimetic Poly(hydroxybutyrate): Alkoxy- and Carboxytriazolines as Latent Ionic Initiator

Abstract

A well-defined high molecular weight poly(3-hydroxybutyrate) was synthesized by “living”/controlled ring-opening polymerization (ROP) of β-butyrolactone (BL) using a metal-free catalytic system. The ROP was initiated from either primary alcohol or carboxylic acid added with 1 equiv of a stable carbene, i.e., 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene carbene, 1. Interestingly, perfect control over molecular weight (Mn up to 32 000 g·mol-1), molecular weight distribution (Mw/Mn ∼ 1.1 − 1.3) and end group fidelity was attained using t-BuOH as the only polymerization solvent at 80 °C. Structural and kinetics studies highlighted an anionic polymerization mechanism where the protonated 1 (1-H) played the role of associated counterion. Attesting for the control of the ROP, amphiphilic block copolymers were further synthesized by polymerization of BL from poly(ethylene oxide) α-methoxy, ω-carboxylic acid macroinitiator while their tensioactive properties were evidenced by the pendant drop method.