Universal Multifunctional Initiator Containing Orthogonal Reactive Sites. Synthesis of Macromonomers and Comb Polymers Using Consecutive Controlled Free Radical and Cationic Ring-Opening Polymerizations

Abstract

A multifunctional reagent (1) containing orthogonal reactive sites that could serve as an initiator for multiple living polymerizations, namely, controlled free radical, anionic, and cationic polymerizations, and a source for a variety of macromonomers, including those for condensation polymerization and functional polymers, has been designed and synthesized in three steps in good yields. The reagent contained an alkoxyamine derived from 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO), an oxazoline, and a protected hydroxyl group. Thus, initiation of controlled free radical polymerization of styrene at the alkoxyamine terminal gave a polystyrene (PS) macromonomer with low polydispersity (Mw/Mn = 1.06−1.16). Cationic ring-opening polymerization of the oxazoline group gave an amphiphilic comb polymer with a hydrophilic poly(ethyleneimine) backbone and a hydrophobic PS side chain. The polymers were characterized by GPC, 1H and 13C NMR, and MALDI−TOF mass spectroscopy. The versatility of the structure is such that different types of macromonomers and macroinitiators suitable for many of the major methods of polymer synthesis can be made, making 1 a “universal” initiator.