PET/PC共混体系的酯交换反应对其高压结晶行为的影响

利用转矩流变仪、DSC、SEM及WAXD等表征手段研究了PET/PC共混体系的酯交换反应对其高压结晶行为的影响.SEM观察表明,PET和PC熔混时的酯交换反应有利于PET/PC体系在高压结晶时生成厚度较大的伸直链晶体,且可以促进其高压下酯交换反应的发生.楔形伸直链晶体和弯曲伸直链晶体的存在证明链滑移扩散和酯交换反应两种机制对体系中聚酯伸直链晶体的增厚有贡献.拟合分峰法和War-ren-Averbach傅里叶分析法的计算结果表明,随PET/PC体系熔混时酯交换反应程度的增加,高压结晶共混物的结晶度降低,PET的平均微晶尺寸增大,点阵畸变平均值则减小,而微晶尺寸分布变宽.提出了在共聚物组分都具备结晶能力时,结晶诱导化学反应和化学反应诱导结晶两种过程在一定条件下可同时发生的观点.

Controllable Assembly of Colloid Particles on the Surface of Polyelectrolyte Multilayer Films

Colloidal adsorption onto certain substrates is of great interest in both basic colloidal chemistry and colloidal lithography with a larger surface area. We studied the assembly of sulfonated polystyrene particles that have anionic charges on the surfaces of the polyelectrolyte multilayer(PEM) films composed of poly(diallyldimethylammonium chloride)(PDDA) and poly(sodium 4-styrenesulfonate)(PSS). The monolayer assembly of the colloid particles without three-dimensional aggregation could be observed by atomic force microscope(AFM) and scanning electron microscope(SEM), and the number of colloids adsorbed per square micrometer was varied systematically from 2 to 7 by fine-tuning the fabrication and postfabrication of PEMs. Based on an electrostatic point of view, an approaching particle is attracted by the precursor film and repulsed by adsorbed particles, the balance between the attraction and repulsion is affected by alternation of surface property of PEMs. This method can provide a fabrication way of a wide range of dotted materials in which its feature size is the diameter of colloid particles.