Addressing the mid-point of polymer chains for multiple functionalization purposes through sequential thiol-epoxy 'click' and esterification reactions

Abstract

A synthetic strategy is devised for the preparation of mid-chain multifunctional polymers. In this strategy, small molecules carrying one or two epoxide units along with two polymerization-initiating sites were prepared in two to three synthetic steps. Atom transfer radical polymerization (ATRP) of methylmethacrylate (MMA) monomer using the newly designed initiators gave rise to epoxide-mid-reactive polymers. A careful chain cleavage study confirmed the midpoint location of the reactive site(s) on the polymer chain. Dual-modification of these reactive epoxide unit(s) through sequential thiol-epoxy and esterification reactions then afforded the midpoint multiply functionalized polymeric structures. Due to compatibility of the ATRP process with the reactive epoxide unit(s) and the cascade nature of the functionalization processes, the present strategy is free from the protective-group requirement of organic synthesis. Moreover, it allows for varying the number and nature of functionalities at the midpoint of a polymer chain.