二元混合高分子刷溶剂响应特性的分子机制--密度泛函理论

Molecular Mechanism of Solvent-Responsive Behavior of Mixed Polymer Brushes——Density Functional Theory

采用加权密度近似密度泛函理论研究了二元混合接枝高分子刷在不同性质溶剂诱导下的垂直相分离情况。计算发现,对于具有一定相容性的等链长和等链节间相互作用能的二元混合接枝高分子刷,在非选择性溶剂中,不良溶剂使得高分子刷收缩,良溶剂使得高分子刷溶胀,但不会发生垂直的相分离;在选择性溶剂中,混合高分子刷可以在溶剂诱导下发生垂直相分离,亲溶剂的高分子链出现在高分子刷的表层,憎溶剂的高分子链蜷曲于高分子刷的底层,接枝高分子刷表现为亲溶剂性质;溶剂的选择性越大,两种接枝高分子链的相容性越差,越容易分层。

The density functional theory（DFT） is used to describe the perpendicular phase separation of binary mixed polymer brush grafted on a surface immersing in different solvents.The DFT predicts that： for binary compatible polymer brushes with the same chain length and interaction potential,the grafted layer shrinks in non-selective poor solvent and swells in non-selective good solvent with no perpendicular phase separation.When the brushes are exposed to a selective solvent,perpendicular phase separation induced by the solvent occurs,the solvophilic chains swell to the upper layer while the solvophobic chains twist at the bottom,and the surface modified by grafted polymer brush is solvophilic.The degree of phase separation is decided by the selectivity of solvent and the incompatibility of two polymers.