水溶性高分子分子量对其与电荷稳定的胶体分散体系的混合体系相行为的影响

利用同步辐射小角X射线散射技术，对不同相对分子质量的水溶性高分子聚氧化乙烯(PEO)与电荷稳定的聚甲基丙烯酸甲酯(PMMA)乳胶的混合体系的相行为进行了研究。 PEO与PMMA乳胶混合体系的相行为与体系中乳胶粒子的体积分数和PEO的浓度相关。 在一定乳胶粒子体积分数下，在较低PEO浓度下，混合体系保持均匀分散性。 而当PEO浓度高于某一临界浓度时，混合体系将发生相分离，生成集团相或者形成面心立方(FCC)晶体结构。 PEO相对分子质量的大小也是影响混合体系相行为的重要因素。 当PEO的相对分子质量较高时，混合体系发生相分离所对应的临界PEO浓度较低。 除此，PEO相对分子质量对混合体系的结晶行为也有影响。 在低乳胶粒子体积分数下，较高相对分子质量的PEO容易使乳胶粒子结晶。 相反的，在较高乳胶粒子体积分数下，较低相对分子质量的PEO容易使乳胶粒子堆积形成结晶结构。

Effect of Relative Molecular Mass of Poly(ethylene oxide) on the Phase Behavior of Charge Stabilized Poly(methyl methacrylate) Colloidal Dispersion

The effect of the relative molecular mass of poly(ethylene oxide) on the phase behavior of its mixture with charge stabilized poly(methyl methacrylate) colloidal dispersion was investigated by means of synchrotron small-angle X-ray scattering technique. The phase structure of the mixture is generally determined by the volume fraction of the colloidal dispersion and the concentration of the polymer. At a certain volume fraction of colloidal dispersion, the mixtures present a homogeneous state when the polymer concentration is below a critical value. When the polymer concentration is larger than the critical concentration, sedimentation can be observed. The mixtures are in a cluster phase or a crystalline state with a face-centered cubic structure. The relative molecular mass of poly(ethylene oxide) also plays an important role in the phase behavior of the mixture. Our results show that the critical concentration of the polymer is low for the mixtures with the polymer of high relative molecular mass. The relative molecular mass of the polymer also affects the formation of crystals.