Jentzsch Christoph, Sommer Jens-Uwe
Leibniz-Institut für Polymerforschung Dresden, Hohe Strasse 6, 01069 Dresden, Germany and Technische Universität Dresden, Institute of Theoretical Physics, 01069 Dresden, Germany.
J Chem Phys. 2014 Sep 14;141(10):104908. doi: 10.1063/1.4895555.
Using a variant of the Bond Fluctuation Model which improves its parallel efficiency in particular running on graphic cards we perform large scale simulations of polymer brushes in poor explicit solvent. Grafting density, solvent quality, and chain length are varied. Different morphological structures in particular octopus micelles are observed for low grafting densities. We reconsider the theoretical model for octopus micelles proposed by Williams using scaling arguments with the relevant scaling variable being σ/σ(c), and with the characteristic grafting density given by σ(c) ~ N(-4/3). We find that octopus micelles only grow laterally, but not in height and we propose an extension of the model by assuming a cylindrical shape instead of a spherical geometry for the micelle-core. We show that the scaling variable σ/σ(c) can be applied to master plots for the averaged height of the brush, the size of the micelles, and the number of chains per micelle. The exponents in the corresponding power law relations for the grafting density and chain length are in agreement with the model for flat cylindrical micelles. We also investigate the surface roughness and find that polymer brushes in explicit poor solvent at grafting densities higher than the stretching transition are flat and surface rippling can only be observed close to the stretching transition.
我们使用键涨落模型的一个变体（该变体尤其在图形处理器上运行时提高了其并行效率），对处于不良显式溶剂中的聚合物刷进行大规模模拟。改变接枝密度、溶剂质量和链长。对于低接枝密度，观察到了不同的形态结构，特别是章鱼状胶束。我们重新考虑了威廉姆斯提出的章鱼状胶束理论模型，使用标度论证，相关标度变量为σ/σ(c)，特征接枝密度由σ(c) ~ N(-4/3)给出。我们发现章鱼状胶束仅横向生长，而非纵向生长，并且我们通过假设胶束核为圆柱形而非球形几何形状来提出该模型的一个扩展。我们表明，标度变量σ/σ(c)可应用于聚合物刷平均高度、胶束尺寸以及每个胶束链数的主曲线。接枝密度和链长相应幂律关系中的指数与扁平圆柱形胶束模型一致。我们还研究了表面粗糙度，发现处于显式不良溶剂中的聚合物刷在高于拉伸转变的接枝密度下是平坦的，并且仅在接近拉伸转变时才能观察到表面波纹。
