Synthesis of Near-Monodisperse Acidic Homopolymers and Block Copolymers from Hydroxylated Methacrylic Copolymers Using Succinic Anhydride under Mild Conditions

Abstract

A new convenient route to well-defined, low-polydispersity polyacids is reported that does not require protecting group chemistry. First, near-monodisperse hydroxylated polymers are synthesized via ATRP of either 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, or glycerol monomethacrylate and then esterified using excess acid anhydride under mild conditions. For example, using a succinic anhydride/hydroxy group molar ratio of two in pyridine, essentially complete esterification of the hydroxy groups in poly(2-hydroxyethyl methacrylate) occurred within 48 h at 20 °C. Moreover, varying this molar ratio allows the final degree of esterification to be easily controlled. THF was examined as an alternative solvent, but a tertiary amine catalyst was required to achieve high degrees of esterification under these conditions. According to 1H NMR studies, the succinate ester bonds were susceptible to hydrolysis at or above pH 12 but were relatively stable at pH 2. Finally, a new poly(ethylene oxide)-based diblock copolymer was synthesized that dissolves molecularly at neutral pH but undergoes micellar self-assembly at low pH.