Synthesis and characterization of styrene‐maleic acid block copolymers with acrylic and methacrylic acids for potential use in membrane protein extraction

Abstract

Styrene‐maleic acid (SMA) block copolymers with acrylic acid (AA) and methacrylic acid (MAA) were synthesized via a 3‐step process comprising: (1) photopolymerization of styrene and maleic anhydride in solution to yield an alternating styrene‐maleic anhydride (SMAnh) copolymer, (2) copolymerization of SMAnh with AA and MAA to yield SMAnh‐b‐AA and SMAnh‐b‐MAA block copolymers, and (3) base‐catalyzed hydrolysis of the anhydride groups to yield water‐soluble SMA‐b‐AA and SMA‐b‐MAA block copolymers. Copolymer compositions and average molecular weights were determined by the synthesis methodology used in which reversible chain transfer was a key component. Copolymer characterization was carried out by a combination of techniques, namely: ATR‐FTIR, 1H‐NMR, dilute‐solution viscometry, GPC, DSC, and TGA. These novel SMA block copolymers have been designed with a view to their use in membrane protein (MP) extraction from plant extracts and other naturally occurring substances of potential therapeutic value. The main function of the AA or MAA blocks is to widen the operational pH range of SMA in terms of (a) maintaining its water solubility at low pH and (b) stabilizing its MP assemblies in solution.