Methacrylic acid microcellular highly porous monoliths: Preparation and functionalisation

By polymerisation of high internal phase emulsions (HIPEs), containing styrene (STY), divinylbenzene (DVB) and methacrylic acid (MAA) in the continuous phase, highly porous polymers including carboxylic functional groups were prepared. The ratio of methacrylic acid to divinylbenzene was varied in order to obtain polyHIPEs with a different degree of crosslinking which influenced a surface area of the polymers, being substantially higher (185 m2/g) with a higher degree of crosslinking (51% DVB) than with a lower degree of crosslinking (24% DVB, 46 m2/g). Up to 90% porous samples were prepared and the optimum hidrophilicity-lipophilicity balance (HLB) of the surfactant was found to be around 4.8-4.9. Both thermal and photo initiation were used to induce polymerisation. The resulting polymers had an open cellular morphology with cavity diameters between 21.8 μm and 44.2 μm and with interconnecting pores between 2.2 μm and 5.0 μm. Monolithic supports were used for further functionalisation with thionyl chloride and multifunctional amines, namely 1,4-diaminobutane and 1,12-diaminododecane. The functionalisation degree with thionyl chloride was 76%.