Sulfonated Co-Poly(arylene-ethynylene) PolyHIPE Hydrogels: Synthesis and Structure–Activity Relationships

Abstract

Porous π-conjugated hydrogels with ionizable side groups provide an attractive strategy for creating water-compatible semiconducting polymer networks. Here, we report a family of sulfonated co-poly(arylene-ethynylene) polyHIPE hydrogels synthesized by Pd-catalyzed Sonogashira polycondensation within oil-in-oil high internal phase emulsion (HIPE) templates. This work demonstrates that copolymer composition and ionic functionality in π-conjugated polyHIPE materials can be systematically used to tune swelling behavior, photophysical properties, and interfacial reactivity, highlighting the versatility of conjugated polyelectrolytes as functional polymeric platforms. By varying the ratio of ionic 1,4-diiodo-2,5-bis(3-sulfonatopropoxy)benzene and neutral diiodobenzene monomers (100:0, 80:20, 50:50, and 20:80), we obtained a series of copolymers with highly interconnected macroporosity (>90%) and pronounced water affinity. Increasing sulfonate content systematically affected water uptake, network swelling, and optical properties, revealing clear structure–property relationships within the conjugated polyHIPE framework. Removal of bisphenols was used as a model function to investigate the combined effects of ionic content, porosity, and electronic structure on activity at the polymer–water interface, specifically adsorption and photocatalysis in water. Among the series, PAE-SO₃-80 exhibited the most balanced combination of adsorption capacity and photocatalytic reactivity, illustrating that copolymer composition can be used to optimize the performance of conjugated polyelectrolyte polyHIPE networks in aqueous environments.