Adsorption and aggregation of 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecyl ammonium bromide) in aqueous solution: effect of intermolecular hydrogen-bonding.

The adsorption and aggregation of 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecyl ammonium bromide) (abbreviated as 12-3(OH)-12) in aqueous solution have been investigated by equilibrium and dynamic surface tension, surface dilational rheology, conductivity, fluorescence probing, viscosity, zeta potential and dynamic light scattering measurements. The results measured by dynamic surface tension, molar and differential conductivities strongly suggested the formation of dimolecular moieties in dilute systems prior to their adsorption and aggregation, which was attributed to intermolecular hydrogen-bonding between the hydroxyl substituted spacers. This increased the hydrophobicity of the molecular moieties and greatly promoted their adsorption at the air/water interface and association in solution. The intermolecular hydrogen-bonding between the molecules adsorbed at the air/water interface made their arrangement tighter and thus produced lower γ(cmc) compared with unsubstituted 12-3-12. Moreover, the effect of intermolecular hydrogen bonding promotes growth of 12-3(OH)-12 micelles and leads to dissociation of the counterions on the aggregate surfaces.