Hydrophilic macroporous monoliths with tunable water uptake capacity fabricated by water‐in‐oil high internal phase emulsion templating

Abstract In this contribution, a series of well‐defined amphiphilic di‐block copolymers poly(ethylene oxide)‐b‐polystyrene (PEO43‐b‐PSx) with different PS segment lengths of x = 41, 78, and 130 units were synthesized through activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The as‐prepared block copolymers successfully stabilized the water‐in‐oil (W/O) high internal phase emulsions (HIPEs) containing pH responsive monomers 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and 2‐(diethylamino)ethyl methacrylate (DEAEMA). The effect of macro‐surfactant loading, PS segment length, and DMAEMA/DEAEMA content on the stability of HIPEs and the corresponding polyHIPE structure were investigated. Results show that the average void size of polyHIPE decreases with the increase of surfactant concentration. Macroporous morphologies with closed‐cell or open‐cell can be manipulated by surfactant loading as well. The openness of polyHIPE decreases as the increase in hydrophobic PS segment length. Compared to DMAEMA containing HIPE systems, stable DEAEMA containing HIPEs are more easily obtained by using the as‐prepared macro‐surfactant. Stable HIPE with a relatively large amount of DEAEMA, up to 70 vol% of oil‐phase has been achieved. The obtained PDEAEMA‐co‐PS polyHIPEs derived from 0.116 mol% PEO43‐b‐PS41 stabilized emulsion templates show pH responsiveness towards water absorption and the highest acidic water uptake capacity can be up to 6.6 times its weight at equilibrium state. This work paves the way for the preparation of hydrophilic macroporous monolith from stable W/O HIPE template, and confirms the strength of macro‐surfactant in such an approach.