两种联接链的季铵盐Gemini表面活性剂水溶液流变行为

季铵盐Gemini表面活性剂C12-s-C12?2Br(s=2)水溶液在25 ℃,3～9 mmol?kg－1和10～40 mmol?kg－1两个浓度范围区受剪切速率γ影响不同,前者在γ=0～1875 s－1内均为牛顿型,后者在各自临界剪切速率γ*之后由牛顿型转变为膨胀型,且零剪切粘度η0随浓度c急剧增大,这是由于溶液中的线状胶团相互缠绕所致.当在联接链中增加乙氧基（C12-s-En-C12?2Br, s=2, n=1、2、3）,由于单元分子几何形状发生明显变化,只生成球状胶团,使其在c=3～120 mmol?kg－1和γ=0～1 875 s－1范围内始终表现为牛顿型,η0仅随c和γ略为增大.降低温度有利于剪切力诱导流型转变,但若在一段温度范围内溶液始终保持牛顿型,温度对η0影响很小.

Rheological Behavior of Two Kinds of Quaternary Ammonium Gemini Surfactants in Aqueous Solution

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.