Isosteric Polymer Design as an Approach to Recapitulate the Properties of Plasticized Commercial Polymers

Abstract

Plasticizers are small molecule additives compounded with polymers to tune their physical properties and facilitate processing, but plasticizers often leach from plastics, where they potentially have negative environmental and ecological consequences. Synthetic design can obviate the need for plasticizers by identifying a polymer with the required properties for an application without the need for external additives. In particular, designing isosteric analogues to commercial polymers that preserve key functionality while expanding the range of accessible thermal and mechanical properties would provide benefits beyond conventional copolymerization or side-chain modification strategies. Here, we demonstrate that a simple and efficient postpolymerization modification procedure provides access to poly(vinyl ether-co-vinyl alcohol) copolymers which are isosteric analogues of poly(vinyl butyral) (PVB). These copolymers exhibit thermal and rheological properties that are complementary to plasticized PVB and existing PVB-like polymers. The ability to tune both density of hydroxyl groups and vinyl ether side chain provided a library of copolymers with glass transition temperatures ranging from −54 to 18 °C. Rheological characterization confirmed that these materials behaved as entangled polymer melts at room temperature, with moduli and relaxation dynamics that depended on both hydroxyl content and side chain identity. Overall, this study demonstrates the value of creating isosteric analogues to commercial polymers that diversify their properties, with the potential for reducing the use of leachable small molecule additives.