The University of Oklahoma, School of Chemical, Biological and Materials Engineering, Sarkeys Energy Center, T-317, Norman, Oklahoma 73019, USA.
J Chem Phys. 2012 Sep 14;137(10):104703. doi: 10.1063/1.4752195.
Monte Carlo simulations are presented for a minimal model of one spherical colloidal particle as it interacts with one attractive flat substrate. The colloidal particle is decorated by either 6 or 14 grafted polymer chains. The chains are always rather short, with their radius of gyration, estimated at infinite dilution in good solvent conditions, never larger than the spherical colloid diameter. Although all simulations are conducted under "good-solvent" conditions for the grafted polymer chains, we find that small changes in the polymer segment-polymer segment energetic interaction parameter can lead to significantly different scenarios. When the Lennard-Jones attraction is weak, 0.12 k(B)T, increasing the polymer length decreases the likelihood of colloidal adsorption, as expected. On the contrary, when the attraction is 0.18 k(B)T, increasing the length of the grafted polymer chains promotes the adsorption of the colloidal brush onto the surface. When the Lennard-Jones energetic parameter that describes polymer segment-polymer segment interactions is 0.15 k(B)T, as the length of the grafted polymer chains increases the probability of colloidal adsorption decreases to a minimum, and then increases. The results, explained in terms of a competition between entropic (due to the reduction in degrees of freedom available to the grafted polymer chains upon colloidal brush adsorption) and enthalpic driving forces (due to favorable colloid-surface and polymer segment-surface interactions), could be useful for controlling the circulation lifetime of liposomes within the blood stream, and optimizing solar energy harvesting by depositing colloidal particles on solid surfaces.
我们提出了一个最小的胶体粒子与一个有吸引力的平面基底相互作用的模型的蒙特卡罗模拟。胶体粒子被 6 个或 14 个接枝聚合物链修饰。这些链总是相当短的，其旋转半径，在良好溶剂条件下无限稀释时估计，从不大于球形胶体的直径。尽管所有的模拟都是在“良好溶剂”条件下进行的，但我们发现，聚合物链段之间的相互作用参数的微小变化会导致明显不同的情况。当伦纳德-琼斯吸引力较弱，为 0.12 k(B)T 时，增加聚合物长度会降低胶体吸附的可能性，这是预期的。相反，当吸引力为 0.18 k(B)T 时，增加接枝聚合物链的长度会促进胶体刷吸附到表面上。当描述聚合物链段之间相互作用的伦纳德-琼斯能量参数为 0.15 k(B)T 时，随着接枝聚合物链长度的增加，胶体吸附的概率先降低到最小值，然后再增加。这些结果可以用熵（由于胶体刷吸附时接枝聚合物链的自由度减少）和焓（由于胶体-表面和聚合物链-表面相互作用有利）之间的竞争来解释，这对于控制脂质体在血流中的循环寿命以及通过在固体表面沉积胶体颗粒来优化太阳能收集可能是有用的。
