Jacquin M, Muller P, Talingting-Pabalan R, Cottet H, Berret J F, Futterer T, Théodoly O
Complex Fluids Laboratory, CNRS UMR 166, 350 George Patterson Blvd, Bristol, PA 19007, USA.
J Colloid Interface Sci. 2007 Dec 15;316(2):897-911. doi: 10.1016/j.jcis.2007.08.025. Epub 2007 Aug 19.
We have linked the structural and dynamic properties in aqueous solution of amphiphilic charged diblock copolymers poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA, synthesized by controlled radical polymerization, with the physico-chemical characteristics of the samples. Despite product imperfections, the samples self-assemble in melt and aqueous solutions as predicted by monodisperse microphase separation theory. However, the PBA core are abnormally large; the swelling of PBA cores is not due to AA (the Flory parameter chi(PBA/PAA), determined at 0.25, means strong segregation), but to h-PBA homopolymers (content determined by liquid chromatography at the point of exclusion and adsorption transition, LC-PEAT). Beside the dominant population of micelles detected by scattering experiments, capillary electrophoresis CE analysis permitted detection of two other populations, one of h-PAA, and the other of free PBA-b-PAA chains, that have very short PBA blocks and never self-assemble. Despite the presence of these free unimers, the self-assembly in solution was found out of equilibrium: the aggregation state is history dependant and no unimer exchange between micelles occurs over months (time-evolution SANS). The high PBA/water interfacial tension, measured at 20 mN/m, prohibits unimer exchange between micelles. PBA-b-PAA solution systems are neither at thermal equilibrium nor completely frozen systems: internal fractionation of individual aggregates can occur.
我们已经将通过可控自由基聚合合成的两亲性带电二嵌段共聚物聚（丙烯酸丁酯）-b-聚（丙烯酸）（PBA-b-PAA）在水溶液中的结构和动力学性质与样品的物理化学特性联系起来。尽管产物存在缺陷，但样品在熔体和水溶液中如单分散微相分离理论所预测的那样自组装。然而，PBA核异常大；PBA核的膨胀不是由于AA（在0.25时测定的弗洛里参数χ(PBA/PAA)表明有强烈的相分离），而是由于h-PBA均聚物（通过排阻和吸附转变点的液相色谱法，LC-PEAT测定其含量）。除了通过散射实验检测到的主要胶束群体外，毛细管电泳CE分析还检测到另外两个群体，一个是h-PAA群体，另一个是游离的PBA-b-PAA链群体，它们具有非常短的PBA嵌段且从不自组装。尽管存在这些游离单体，但发现溶液中的自组装处于非平衡状态：聚集状态依赖于历史，并且在数月内胶束之间没有单体交换（时间演化小角中子散射）。在20 mN/m下测量的高PBA/水界面张力阻止了胶束之间的单体交换。PBA-b-PAA溶液体系既不是处于热平衡状态也不是完全冻结的体系：单个聚集体内部可以发生分级分离。
