Thiol Addition to the Pendant Vinylbenzene Groups of (Vinyl)polystyrene PolyHIPE Via a Batch and a Cross-Flow Method

Abstract

This paper reports the preparation of an emulsion-derived foam with pendant vinylbenzene groups, called (vinyl)polystyrene polyHIPE. Thiols, HSR, underwent regioselective anti-Markovnikov addition to the residual vinyl groups in the presence of free-radical azo initiators, leading to a wide range of functional polyHIPEs. The large pores and the interconnected structure of polyHIPE allow reactants and solvents to be driven through the molded monolith at very low pressure. These characteristics enable functionalization of the matrix via a convective phenomenon: the cross-flow method. In this paper, comparison between this method and the batch method, corresponding to diffusion of reactants through the pores of small cubes of polymers, was carried out by calculation of the degree of functionalization and the percent conversion achieved. Fourier transform infrared (FT-IR) spectra of the resulting modified resins often showed near-complete disappearance of initial vinyl groups and their replacement by the expected spacer-supported functionalities. Addition of thiols to the vinylbenzene groups were quantified by elemental microanalysis.