Photorheological effects in aqueous micellar tetramethylammoniumhydrogen-2-dodecyl malonate via photodimerization of acridizinium bromide

Aqueous solutions of tetramethylammoniumhydrogen-2-dodecyl malonate (TMHM) were investigated theologically in the absence and presence of monomeric an d photodimerized acridizinium bromide as solubilizates. Upon constant shear ing a viscosity increase (accompanied by viscoelasticity) was observed in a certain range of TMHM concentration after an induction period. This indica tes the formation of shear induced structures. viscoelasticity was characte rized via stress relaxation experiments revealing a single relaxation proce ss with time constants of 0.2-0.3 s mostly. At certain shear rates a tempor al oscillation of viscosity was observed. In the presence of acridizinium b romide the elasticity was reduced and the TMHM concentration range of visco elastic flow was narrowed while relaxation time constants remained constant . Photodimerization of acridizinium bromide (performed in situ) reverted th e effects induced by the monomers. (C) 1999 Academic Press.