Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
Langmuir. 2013 Aug 20;29(33):10455-62. doi: 10.1021/la4021959. Epub 2013 Aug 7.
We investigate structural and thermodynamic properties of surface-grafted layers of model "bottle-brush" polymers by Monte Carlo simulation. The polymers consist of a longer main chain densely grafted with shorter side chains, of which the latter have some degree of affinity to the surface. Our focus is on the effect of the side-chain surface affinity on the brush properties, which we study in terms of compression isotherms spanning a broad range of grafting densities. For low grafting densities, side-chain adsorption causes the polymers to spread on the surface. As the grafting density is increased, the layer goes through a "pancake-to-brush" transition to form a brush with the main chains aligned perpendicular to the surface. We find that side-chain adsorption is decisive for the structure of dilute layers and in the transition region but has little influence on the properties of dense brushes. The close relation between compression and adsorption isotherms is discussed, and the implications of side-chain adsorption for the ability of the polymer to form a dense brush are investigated. This analysis suggests that side-chain surface affinity alone will not give rise to "brush of bottle-brushes" layers by adsorption of polymers from solution, in agreement with recent experimental results.
我们通过蒙特卡罗模拟研究了模型“瓶刷”聚合物的表面接枝层的结构和热力学性质。这些聚合物由一条较长的主链组成，主链上密集地接枝着较短的侧链，这些侧链在一定程度上与表面有亲和力。我们关注的是侧链表面亲和力对刷状性质的影响，我们通过跨越广泛接枝密度范围的压缩等温线来研究这种影响。对于低接枝密度，侧链吸附会导致聚合物在表面上展开。随着接枝密度的增加，层经历了从“饼状到刷状”的转变，形成了主链垂直于表面排列的刷状结构。我们发现，侧链吸附对稀层和过渡区的结构具有决定性影响，但对密刷的性质影响很小。讨论了压缩和吸附等温线之间的密切关系，并研究了侧链吸附对聚合物形成密刷能力的影响。这种分析表明，仅仅通过从溶液中吸附聚合物，侧链表面亲和力本身不会导致“瓶刷的瓶刷”层，这与最近的实验结果一致。
