采用熔融共混方式,利用两嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸甲酯(PS-b-PMMA)来增容聚甲基丙烯酸环己酯(PCHMA)/聚甲基丙烯酸甲酯(PMMA)共混体系,主要研究PS-b-PMMA嵌段比、均聚物的分子量以及体系粘度对增容效果的影响.研究发现,非对称结构的嵌段共聚物较对称结构的嵌段共聚物更容易在体相形成胶束,胶束的形成减少了嵌段共聚物在界面的利用率.均聚物分子量增大,嵌段共聚物的胶束均增加.分散相分子量增大,造成了界面的嵌段共聚物稳定性减弱,容易扩散至分散相内部,形成胶束.连续相分子量增大致使链段溶胀力减小,嵌段共聚物胶束外围的乳化效果降低,而且连续相粘度增大,使得嵌段共聚物胶束滞留在连续相,难以迁移至界面.共混体系的混合剪切增加,粘度变小,嵌段共聚物的扩散速率加快.通过调控均聚物分子量和体系粘度,能有效地减少体相胶束的形成,增大嵌段共聚物在界面的利用率.通过Leibler干湿刷理论、焓驱溶胀聚合物刷以及Stokes-Einstein扩散理论可以解释相关的结论.
Melt-mixed method was used to compatibilize poly(cyclohexyl methacrylate) (PCHMA) and poly (methyl methacrylate) (PMMA) binary blends by adding diblock copolymer polystyrene-b-poly (methyl methacrylate) (PS-b-PMMA).Effects of block ratio of PS-b-PMMA,molecular weight (MW) of each homopolymer component,and viscosity of the blend on its compatibility were discussed.We found that the asymmetric block copolymers (BCPs) tend to form micelles and reduce the compatibilization efficiency,rather than the symmetric BCPs.A higher MW leads to an increased amount of BCP micelles.Specifically,increasing the MW of dispersed phase (PMMA) destabilizes the interface,enhances the BCP diffusion into the PMMA phase and forms a larger amount of micelles.On the other hand,increasing the MW of matrix (PCHMA) leads to the increase of phase viscosity,suppresses swelling and external emulsification of the micelle PS block,reduces the micelle migration and keeps the BCP micelles detented inside the PCHMA phase.Therefore,the compatibilization efficiency can be controlled by manipulating the MW of homopolymer component,BCP symmetry and shear viscosity.Finally,the results were interpreted by the Leibler wet-dry brush theory,enthalpy-driven swelling of a polymer brush and Stokes-Einstein diffusion theory.
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