Role of Polymer Backbone Rigidity on the Solution Properties of Bioderived Poly(styrene- <i>co</i> -maleic anhydride) Derivatives

Abstract

Poly(styrene-co-maleic anhydride) (SMAnh) and its hydrolyzed derivative, poly(styrene-co-maleic acid) (SMA), have been widely utilized in applications such as adhesives, drug delivery systems, and hydrogels. Despite the copolymer’s versatility, there is a growing need for bioderived alternatives that retain comparable performance while reducing environmental impact. Here, we investigate how polymer backbone rigidity governs the thermal and solution properties of two bioderived analogues of SMAnh: poly(styrene-co-itaconic anhydride) (SIAnh) and poly(indene-co-maleic anhydride) (IMAnh). Using asymmetrical flow field flow fractionation with light scattering detection (AF4-LS), we present a comprehensive comparison of how different media and protonation states affect the conformation and flexibility of the corresponding hydrolyzed copolymers SMA, poly(styrene-co-itaconic acid) (SIA), and poly(indene-co-maleic acid) (IMA), thereby revealing how their chemical nature dictates their structural response in solution. Data from AF4-LS, size exclusion chromatography with light scattering (SEC-LS), and thermal analysis highlight how subtle changes in monomer substitution (itaconic, indene vs styrene/maleic) alter backbone rigidity. It was determined that SIA is the most flexible copolymer derivative, SMA exhibits intermediate rigidity, and IMA is the most rigid. Each copolymer substitution pattern results in a distinct copolymer coil conformation in solution and ionization behavior. Collectively, these data indicate that the bioderived SIAnh and IMAnh are viable alternatives to SMAnh, but with distinct rigidity-dependent properties, which may result in slightly different performance in applications.