关键词: Gemini表面活性剂, 流变行为, 联接链影响

Abstract: Different flow behaviors influenced by shear rate were observed in two concentration regions (3～9 mmol•kg－1 and 10～40 mmol•kg－1) of quaternary ammonium Gemini surfactant C12-s-C12•2Br(s=2) in aqueous solution. The solution in the former concentration region kept Newtonian flow through out the range of shear rate γ examined from 0 to 1 875 s－1.But in the latter concentration region, the flow transformed from Newtonian to dilatant flow after γ reached a value of critical shear rate γ* which depended on temperature and concentration. And a sharp increase of the zero-shear viscosity η0 along with the raise of c appeared in this region. It was suggested that the tangle of thread-like micelles of C12-s-C12•2Br(s=2) existed in the solution led to the phenomenon mentioned above. The surfactants C12-s-C12•2Br(s=2) turns to C12-s-En-C12•2Br(s=2, n=1,2,3) by insertion of one, two or three oxyethyl groups into the spacer of it. By the reason of the evident variation in geometric shape of unit molecule, this kind of Gemini surfactant in aqueous solution only aggregated into sphere micelles so that it retained Newtonian behavior over the range of c=0～120 mmol•kg－1 and γ=0～1 875 s－1 with slight increase of η0.In addition, reducing temperature favors shear induced structure transform but gives small effect on those systems keeping Newtonian behaviors over the temperatures range studied.

Key words: Gemini surfactants, Rheological properties, Spacer effect