Associative networks of cholesterol-modified dextran with short and long micelles
作者:Hala Afifi、Marcelo A. da Silva、Cécile Nouvel、Jean-Luc Six、Christian Ligoure、Cécile A. Dreiss
DOI:10.1039/c1sm05416c
日期:——
The strong associative behaviour between cholesterol-modified dextran (CMD) and short and long polyoxyethylene cholesteryl ether (ChEO10) micelles were investigated using rheology and small-angle neutron scattering (SANS). In solutions of short rod-like micelles (ChEO10 alone), the addition of 5.0 wt% CMD induced a remarkable transition from a Newtonian system to a highly solid-like viscoelastic network, with an increase in zero-shear viscosity of over 5 orders of magnitude. The frequency sweeps at ChEO10 concentrations above 2.5 wt% were fitted to a Maxwell model with 3 elements and, quite remarkably, fell onto a single master curve, while no network was formed at 2.5 wt% micelles. Viscoelastic solutions of wormlike micelles (WLMs) were obtained by adding the co-surfactant triethylene glycol monododecyl ether (C12EO3) to ChEO10 solutions at a constant ChEO10/C12EO3 ratio of 5/1. The introduction of CMD into the WLM solutions induced a transition to a more liquid-like behaviour (G″/G′ increased), however both moduli increased by one order of magnitude. At the lowest ChEO10 concentration (2.5%), the solid-like behaviour was lost. Overall, a comparable rheological response was obtained for the WLM and the short rods with CMD, however the WLM/CMD behaviour suggested a wider spectrum of relaxation processes, longer relaxation times and higher plateau moduli. SANS data from the polymer/micelles mixtures displayed a strong structural peak and were remarkably identical for both ChEO10/CMD and ChEO10/C12EO3/CMD systems, suggesting a very similar type of network structure, independently of the initial size of the micelles. Overall, all the results taken together show a very high affinity between the polymer and the micelles and suggest a breakup of the WLM induced by CMD. The resulting network is constituted by polymeric chains connected by micellar aggregates through hydrophobic interactions between the micellar cholesterol cores and the pendent cholesterol moieties of the polymer.
利用流变学和小角中子散射 (SANS) 研究了胆固醇修饰葡聚糖 (CMD) 与短聚氧乙烯胆固醇醚 (ChEO10) 胶束和长聚氧乙烯胆固醇醚 (ChEO10) 胶束之间的强缔合行为。在短棒状胶束(仅 ChEO10)的溶液中,添加 5.0 wt% CMD 引起从牛顿系统到高度类固体粘弹性网络的显着转变,零剪切粘度增加了 5 个数量级以上震级。 ChEO10 浓度高于 2.5 wt% 时的频率扫描符合具有 3 个元素的 Maxwell 模型,并且非常引人注目地落在一条主曲线上,而在 2.5 wt% 胶束下没有形成网络。通过将辅助表面活性剂三甘醇单十二烷基醚 (C12EO3) 添加到 ChEO10 溶液中,以恒定的 ChEO10/C12EO3 比例为 5/1 获得蠕虫状胶束 (WLM) 的粘弹性溶液。将 CMD 引入 WLM 解决方案引发了向更类似液体行为的转变(G”/G' 增加),但是两种模量都增加了一个数量级。在最低 ChEO10 浓度 (2.5%) 下,类似固体的行为消失了。总体而言,WLM 和带有 CMD 的短棒获得了类似的流变响应,但 WLM/CMD 行为表明弛豫过程范围更广、弛豫时间更长和平台模量更高。来自聚合物/胶束混合物的 SANS 数据显示出很强的结构峰,并且 ChEO10/CMD 和 ChEO10/C12EO3/CMD 系统非常相似,表明网络结构类型非常相似,与胶束的初始尺寸无关。总体而言,所有结果综合显示聚合物和胶束之间具有非常高的亲和力,并表明 CMD 诱导了 WLM 的破裂。所得网络由胶束聚集体通过胶束胆固醇核心和聚合物的悬垂胆固醇部分之间的疏水相互作用连接的聚合物链构成。