Functional group interactions of adsorbed small charged bolaform molecules and their effects on intermolecular and surface forces in dispersions

This study illustrates how polar functional groups adjacent to bolaform charged groups modified the interaction behaviour of the compound with an oppositely charged surface. Adsorbed fumaric (trans-1,2-ethylene dicarboxylic) acid bridges particles in dispersions. However the presence of hydroxyl group adjacent to the two bolaform carboxylic groups depresses this particle bridging behaviour. Instead dihydroxyfumaric acid adsorbed to form a steric barrier. Molecular modelling shows that each of the two hydroxyl groups in dihydroxyfumate formed a hydrogen bond with the same carboxylic acid group leaving the other fully charged and free to adsorb onto a particle. In contrast, the presence of a methyl group adjacent to a bolaform carboxylic acid group did not affect the particle bridging attribute of the compound and this behaviour was displayed by adsorbed mesaconic or 2-methylfumaric acid.