ARGET‐ATRP using β‐CD as reducing agent for the synthesis of PMMA‐b‐PS‐b‐PMMA triblock copolymers

Abstract

ABSTRACTWe studied the role of β‐cyclodextrin (CD), a polyhydroxy cyclic sugar as reducing agent (RA) for the copper mediated activators regenerated by electron transfer atom transfer radical polymerization (ATRP) with the successful chain extension of methyl methacrylate blocks on the bifunctional polystyrene macroinitiator (PS‐MI) using nonaqueous solvent system for the first time. The PS‐MI was prepared by ATRP, had a polydispersity of 1.05 and gave triblock copolymers in the presence of β‐CD. We found that alcoholic groups of β‐CD show provisional reducing character and in situ convert Cu(II) to Cu(I) during polymerization. A well‐defined triblock copolymer with narrow molecular weight distribution (polydispersity index < 1.5) was obtained at 100 °C. The molecular weight of the block copolymers increased linearly with monomer conversion and the reaction showed good control over the molecular weights when compared to the theoretical values. We show that the mild reducing power of β‐CD is retained in a nonaqueous solvent also and is efficient with catalyst/RA ratio of 1:0.5. The effect of temperature on the reducing competency of β‐CD was evaluated and found to be active at around 80 °C even though its melting temperature is 290 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47117.