Abstract: The interaction of diphenylamine-4-diazonium salt(DDS) and sodium dodecylsu-fate(SDS) in aqueous solution was studied. The results show that, the relative viscosity(η_r) of solution(0=0.05 mol/L) changes with SDS/DDSmolar ratio ξ distinctly in three regions. In region Ⅰ(ξ=0～1.9), the DDSreacts with SDSto form precipitate and the η_ris low. In region Ⅱ( ξ =1.9～2.3), the precipitate dissolves and the η_rrises dramatically and reaches the maximum at ξ=2.3, which is 2520 times greater than that of original. In region Ⅲ( ξ >2.3). The relative viscosity of solution decreases rapidly with increasing ξ. The phenomenon has been interpreted as follows: the viscosity increasing of the solution is ascribed to the electrostatic attraction between the diazonium cation of DDSand the anion of SDS, further more the diphenylamine moiety of DDSembeds into the hydrophobic area of SDSrod micelles to form larger aggregates. As a result, the viscosity of the solution increases rapidly. It was confirmed that the viscosity change of the DDS/SDSsolution is sensitive towards light, i.e. the increased viscosity will decrease under irradiation of UVlight because the light decomposes the diazonium group. This behavior may be used to develop a light sensitive viscosity system.

Key words: Diphenylamine-4-diazonium salt, Sodium dodecylsulfate, Relative viscosity