双峰聚合物分子刷的层化机理

Stratification in Bimodal Polymer Brushes

建立了用于模拟双峰聚合物分子刷相结构的自洽场理论.模拟结果表明,良溶剂条件能够促使双峰聚合物分子刷裂分为内外两个亚分子层,其中短链居于内分子层,而长链伸展到外分子层.体系溶解性的加强不仅使聚合物的密度分布逐渐趋近强分凝理论的解析结果,而且加大了分子链的伸展和链段的局部取向程度.分子链接枝密度的增加能够促使分子刷的层化,并且在良溶剂区域,不同接枝密度的分子链密度分布可以回归到同一条主线.在良溶剂条件下,长链的聚合度对短链的密度分布影响不大,但能够导致长链向外分子层扩展.

The density profiles in a mixture of bimodal polymer brushes and solvent were simulated with the aid of a self-consistent field theory （SCFT）. The results showed that the bimodal brushes in good solvent form two sub-layers, which were in good agreement with those from both experiments and Monte Carlo simulations. And the increase of solubility not only makes the density profiles obtained by SCFT close to the results calculated with strong segregation theory （SST） asymptotically, but also leads to further stretching of polymer chains and sufficient orientation of chain segments. Moreover, the enlargement of grafting densities facilitates the stratification of brushes. In good solvent condition, density profiles with different total grafting densities could fall onto the same master curve. Additionally, polymerization index of long chains plays an important role in stretching of long chains, but it has little effect on density profiles of short chains.