摘要
阴、阳离子表面活性剂之间强烈的相互作用利于形成自由弯曲的蠕虫状胶束。本文利用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)和阴离子表面活性剂油酸钠(Na OA)制备了CTAB/Na OA蠕虫状胶束,研究了两表面活性剂的混合比和表面活性剂总浓度的变化对蠕虫状胶束体系稳态流变性及动态粘弹性的影响。结果表明,蠕虫状胶束在剪切过程中的解缠、拟网状结构的破坏以及最终沿剪切速度方向取向等是蠕虫状胶束产生剪切稀释特性的原因。两表面活性剂的混合比和表面活性剂总浓度的变化导致表面活性剂之间的静电作用、疏水作用发生较大的变化,最终引起体系内部表面活性剂聚集体形态的差异。体系内蠕虫状胶束长度、体系结构复杂程度、蠕虫状胶束形成的网络结构的致密度等都影响着体系的流变行为。在混合比R=3.6、总浓度CT=0.24mol/L时,体系中蠕虫状胶束最长,网络结构最为紧密,体系的零剪切粘度达到最大值。表面活性剂浓度一定时,混合比的提高有助于蠕虫状胶束的定向生长,弛豫时间τR和储能模量高频区平台模量G0提高,R=3.6时两者皆达到极大值,此后由于蠕虫状胶束的分枝化及(或)胶束破裂导致τR及G0下降。在表面活性剂混合比一定(R=3.6)时,表面活性剂浓度的提高利于蠕虫状胶束的增长或者分枝化,增加了胶束网络结构缠绕(融合)点的密度,导致G0逐渐增大。Cole-Cole图证实本文研究的蠕虫状胶束体系是符合Maxwell模型的线性粘弹性流体。
The strong interactions between anionic and cationic surfactant can induce the formation of flexible wormlike micelles. The wormlike micelles were prepared by mixing cetyltrimethyl ammonium bromide （CTAB） and sodium oleate （NaOA）. The influence of molar ratio （R） and total surfactant concentration （CT） on the steady-state rheological properties and dynamic viscoelasticity of wormlike mieelles were studied. The results showed that the untangling of wormlike mieelles, the broken of the network and the orientation of wormlike micelles along with the direction of shearing rate result in shear thinning. Electrostatic and hydrophobic interactions vary obviously with R and Cr and lead to the difference in morphology of surfaetants＇ aggregation. The rheological behavior is affected by the length of wormlike micelles, the complexity of structure and the density of network. When R = 3.6 and Cv = 0.24mol/L, the wormlike micelles are the longest and the zero-shear viscosity reaches a maximum. When Ca, is constant, the increase of R benefits the growth of wormlike micelles in one dimension and thus leads to the extension of the relaxation time τR and the increase of plateau value G0. TR and Goreaeh a maximum when R = 3.6. Thereafter, the increase of R promotes the branching and/or the fracture of wormlike micelles and therefore results in the decrease of τR and Go. When τR is constant （R = 3.6） , the increase of Cτ contributes to the branching and growth of wormlike mieelles, increase the density of the network, so that Go is enhanced. The Cole-Cole plots demonstrated that the system fits the Maxwell＇ s mechanical model as linear viscoelastic fluid.
出处
《化学通报》
CAS
CSCD
北大核心
2015年第8期710-716,共7页
Chemistry
基金
国家自然科学基金项目(21173079
91334203
21476072)资助
