论文标题
半脱水和浓缩溶液的分子动力学模拟：渗透压中意外的有限尺寸效应
Molecular Dynamics Simulations of Semi-Dilute and Concentrated Solutions: Unexpected Finite Size Effects in Osmotic Pressure
论文作者
论文摘要
我们通过分子动力学模拟和良好的溶剂条件，探索了从1到100的各种聚合指标，在1到100的聚合指数中探索半稀释和浓缩的低聚合物和聚合物。该参数范围涵盖了无重叠和强链重叠制度，这是由聚合物堆积分数量化的$ 0.1 \leφ\ le {14} $。与一些共同的信念相反，渗透压的非理想部分表现出强大的有限尺寸影响。在重叠制度中，它与de cloizeaux的缩放形式大大偏离。有限尺寸校正项与1/N成正比，而不论$φ$。我们提出了一个简单的现象学描述，对无限链极限和1/n校正项的单体密度依赖性的渗透压。我们扩展了有限尺寸效应的处理以覆盖具有2个不同链长度的二进制混合物，并证明所提出的状态方程适用于有效的质量质量积聚的反链长度$ 1/n_ {eff} $。我们还讨论了回旋半径的密度依赖性的有限尺寸效应。
We explore semi-dilute and concentrated oligomers and polymers in a broad range of polymerization indices N ranging from 1 to a 100 and in a range of monomer number densities $ϕ$ from 0.1 to 0.8 via molecular dynamics simulations and under good solvent conditions. This parameter range covers both no-overlap and strong chain overlap regimes, as quantified by the polymer packing fraction $0.1\leΦ\le{14}$. Contrary to some common beliefs, the non-ideal part of the osmotic pressure demonstrates strong finite size effects. In the overlap regime, it deviates substantially from the scaling form of de Cloizeaux. The finite size correction term is proportional to 1/N, irrespective of $Φ$. We propose a simple phenomenological description of the osmotic pressure in the infinite chain limit and of the monomer density dependence of the 1/N correction term. We extend the treatment of finite size effects to cover binary mixtures with 2 different chain lengths, and demonstrate that the proposed equation of state is applicable with an effective mass-averaged inverse chain length $1/N_{eff}$. We also discuss finite size effects in the density dependence of the gyration radius.
