论文标题
通过快速非平衡蒸发的聚合物 - 胶体混合物的分层
Stratification of polymer-colloid mixtures via fast nonequilibrium evaporation
论文作者
论文摘要
在聚合物 - 胶体混合物的干燥液膜中，研究了将聚合物放在较大胶体顶部的分层。通常认为，分离的聚合物 - 胶体层的形成仅是由于快速蒸发时大小的比例，如二进制胶体混合物中。通过将实验与理论模型进行比较，我们发现在干燥界面附近的粘度过渡是控制聚合物胶体混合物中分层层的另一个重要参数。以高蒸发速率，表面附近的聚合物浓度增加导致从半二硫到浓缩状态的相过渡，其中胶体颗粒被动力学地捕捉。分层仅在分层层的形成之前，才能进化到干燥界面附近的浓缩状态。否则，在形成隔离层之前，胶体将被聚合物捕获在浓缩状态中。同样，如果初始聚合物浓度太低，无法在短时间内形成足够高的聚合物浓度梯度，则不会观察到分层。我们的发现与开发用于绘画，防配合和防反射涂层的溶液铸造聚合物复合材料有关。
In drying liquid films of polymer-colloid mixtures, the stratification in which polymers are placed on top of larger colloids is studied. It is often presumed that the formation of segregated polymer-colloid layers is solely due to the proportion in size at fast evaporation as in binary colloid mixtures. By comparing experiments with a theoretical model, we found that the transition in viscosity near the drying interface was another important parameter for controlling the formation of stratified layers in polymer-colloid mixtures. At high evaporation rates, increased polymer concentrations near the surface lead to a phase transition from semidilute to concentrated regime, in which colloidal particles are kinetically arrested. Stratification only occurs if the formation of a stratified layer precedes the evolution to the concentrated regime near the drying interfaces. Otherwise, the colloids will be trapped by the polymers in the concentrated regime before forming a segregated layer. Also, no stratification is observed if the initial polymer concentration is too low to form a sufficiently high polymer concentration gradient within a short period of time. Our findings are relevant for developing solution-cast polymer composite for painting, antifouling and antireflective coatings.
