Studies of Phase Transition in Block Copolymer Solutions by Small-Angle Light Scattering Spectroscopy

构建了一种高速光散射光谱系统，用于测量溶液中嵌段共聚物的相分离和/或相变过程中的分子运动，其弛豫时间范围为10^<-8> ~ 10^3秒。研究了高分子量聚苯乙烯（BZ）和对花香烃（PC）的选择性混合溶剂中，在通常30 ~ 150和小于10的散射角范围内，聚苯乙烯(PS)-嵌段聚丙烯酸甲酯二嵌段共聚物（M^w=1.53*10^6 (38.5wt%PS)）的相变随混合比和温度跃变的变化规律。当rheta=30-150‰时，双嵌段共聚物在PC的混合比大于60 vol%时形成单分散的胶束，并在单共聚物（unimer）与胶束之间呈现明显的闭合缔合平衡。胶束动力学的主要特征是胶束内部发生的巨大的内部运动。聚酰亚胺和聚甲基丙烯酸甲酯亚链之间的主动流体动力学异接触或成分波动导致了胶束内运动。而在5 ~ 10 ~ 10个角范围内，溶液的散射强度在小至μ s的时间间隔内波动，绝对强度变化为3个数量级。这些溶液在静止状态下的动态光散射（DLS）表明，强度波动源于其大小在一到五个数量级之间快速变化的结构；所观察到的空穴胶束结构被认为不是稳定的，而是瞬态的，在很短的时间间隔内产生和消失。Couette流下的DLS证实了这一现象，结果是剪切场中只观察到一种共聚物。在20 ~ 80℃的温度差异下，共聚物链的构象没有明显变化。少

A high-speed light scattering spectroscopy system which measures molecular motions appearing in the phase separation and/or the phase transition of block copolymers in solution was constructed, in which the molecular motions detectable are ranging from 10^<-8> to 10^3 second in the magnitude of the relaxation times. At the scattering angles rheta in the range of usual 30-150ﾟ and at rheta smaller than 10ﾟ, phase transitions on polystirene (PS)-block-poly (methyl mathacrylate) diblock copolymer of high molecular weight such as M^w=1.53*10^6 (38.5wt%PS) were investigated in selective mixed solvents of benzene (BZ) and p-cymene (PC) as a function of the mixed ratios and the temperature differences in the temperature jump. When measured at rheta=30-150ﾟ, the diblock copolymer were found to form a monodispersed micelle at the mixed ratio more than 60 vol% of PC and to be in apparent closed association equlibrium between the single copolymer (unimer) and the micelle. The micelle dynamics was … More charcterized by its vast internal motions which occur inside the micelle. The intramicellar motions were attributed to active hydrodynamic heterocontacts between PS and PMMA subchain elements, or the composition fluctuation. At smaller angles as 5-10ﾟ, however, the scattering intensity of the solution fluctuated at the time interval as small as mus, the absolute intensity varing in three order of magnitude. Dynamic light scattering (DLS) from these solutions in quiescent state made clear that the intensity fluctuations were originated from structures whose sizes varing quickly in one to five order to magnitude ; the fuge micellar structures observed are considered not of be stable but transient ones, which are created and disappear in very short time intervals. DLS under Couette flow ascertained this picture with the result that only a single copolymer was observed in the shear field. The temperature difference of 20-80ﾟC induced no detectable conformation change in the present diblock copolymer chain. Less