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

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 1 H 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.