Core-shell polymer aerogels prepared by co-polymerisation of 2,4-dihydroxybenzoic acid, resorcinol and formaldehyde

Abstract

DHBARF polymer aerogels were prepared from mixtures containing a fixed stoichiometric amount of formaldehyde (F) and varying proportions of resorcinol (R) and 2,4-dihydroxybenzoic acid (DHBA), with the objective of combining the advantages of high mesopore volume and solids content of RF aerogels with the ion exchange capacity of DHBAF aerogels. The results show that surface area, pore volume, pore size and ion exchange capacity vary in a systematic fashion as the composition of the synthesis mixture is altered. It was found that up to a DHBA mole fraction of about 0.5 preferential phase separation of RF occurred and lead to the formation of primary particles consisting of an RF core and a rough DHBAF shell. When DHBAF and DHBARF aerogels were prepared using the same %DHBA, it was found that the addition of R to the synthesis mixture resulted in increased values of surface area, mesopore volume and mean diameter while simultaneously maintaining the ion exchange capacity of the wet gel. The optimum compromise was found for a DHBARF aerogel with core-shell structure prepared using 5% DHBA and 5% R. Under these conditions the ion exchange capacity was at its maximum value of slightly higher than 2 meq g 1, the surface area was 850 m2 g 1, the mesopore volume was 2 cm3 g 1 and the mesopore mean diameter was 17 nm.