Synthesis and Thermal Properties of Well-Defined Amphiphilic Block Copolymers Based on Polyglycidol

Abstract

A series of amphiphilic block copolymers functionalized with three different alkyl side chains (alkyl chain length = C12, C14, and C16) were synthesized and analyzed via NMR spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The block copolymers were obtained in a four-step synthesis. In the first step ethoxy ethyl glycidyl ether (EEGE) and tert-butyl glycidyl ether (tBuGE) were sequentially polymerized via an anionic mechanism. In the next step, the acetal protection groups of EEGE repeating units were selectively removed and the hydroxyl groups obtained were reacted with alkyl isocyanates. Finally, the tert-butyl ether protection groups were removed. All steps of the synthesis were controlled via 1H NMR spectroscopy, GPC, and DSC analyses. All block polymers showed three thermal transitions regardless of the chain length of the isocyanate used: a glass transition characteristic for the polyglycidol backbone and two endothermic peaks, associated with melting of the aliphatic side chains and subsequent breakdown of the hydrogen bonds due to the urethane groups. This thermal behavior suggests that diblock copolymers self-assemble into microdomains whose stability (existence) can be tuned with temperature.