Preparation of well-defined Poly(Vinyl alcohol) by hydrolysis of Poly(Vinyl acetate) synthesized by RAFT suspension polymerization

Abstract

Poly(vinyl alcohol) (PVA) is a widely used synthetic polymer that is made by hydrolysis of poly(vinyl acetate) (PVAc). A significant challenge in the production of well-defined PVA arises due to the high frequency of chain transfer reactions that occur in the radical polymerization of PVAc, which limits the molecular weight and leads to branching. Upon hydrolysis of PVAc, both acetate groups and branch points can be hydrolyzed, resulting in a PVA with a significantly lower molecular weight than the parent PVAc, making control over the molecular weight distribution of PVA difficult. In this work we demonstrate the production of PVAc with a well-defined and linear structure by reversible addition-fragmentation chain transfer (RAFT) polymerization under conditions in which chain transfer is reduced. PVAc samples were prepared by suspension polymerization using both conventional free-radical polymerization and RAFT polymerization at 50 °C. When using RAFT polymerization, upon hydrolysis there was a minimal decrease of the degree of polymerization and high molecular weight PVA of low dispersity was obtained. These results demonstrate the synthesis of well-defined PVA and offers a potential route to the production of PVAc and PVA products with uniform properties.