论文标题
半脱水和浓缩的zwittionic聚合物溶液中的自我辅助理论
Theory of self-coacervation in semi-dilute and concentrated zwitterionic polymer solutions
论文作者
论文摘要
基于随机相近似，我们在zwitterionic聚合物溶液中发展了一种自我辅助分子理论。我们表明，单体单元的体积相互作用与聚合物骨架上带电组的静电相关性之间的相互作用会导致液态液相分离（自我辅助）。我们根据静电相互作用强度分析了凝聚酸盐相聚合物浓度的行为 - Bjerrum长度与链的键长的比率。我们确定在广泛的聚合物浓度值中 - 从半浸泡到相当浓的溶液 - 单体单元的链连接性和排除的体积相互作用对偶极单体单元对总自由能的静电相互作用的贡献的影响极为弱。我们表明，对于相当弱的静电相互作用，静电相关性表现为keesom的相互作用，就像点状的自由旋转偶极子（Keesom Orchime）一样，而在强静电相互作用的区域中，静电能量由Debye-H {ü} Ckel Limiting Lain（Debye Lagime）描述。我们表明，对于实际的zwittionic凝聚力，Keesom semime仅用于足够小的聚合物浓度的凝聚液相，而Debye Segime则大约实现了相当密集的凝聚力。使用密度函数理论的平均场变体，我们计算$“ $ coacervate-solvent $” $接口的表面张力（表面自由能）作为批量聚合物浓度的函数。获得的结果可用于估计实际应用所需的聚合物链的参数，例如药物封装和递送以及粘合剂材料的设计。
Based on the random phase approximation, we develop a molecular theory of self-coacervation in zwitterionic polymer solutions. We show that the interplay between the volume interactions of the monomeric units and electrostatic correlations of charged groups on a polymer backbone can result in liquid-liquid phase separation (self-coacervation). We analyse the behavior of the coacervate phase polymer concentration depending on the electrostatic interaction strength -- the ratio of the Bjerrum length to the bond length of the chain. We establish that in a wide range of polymer concentration values -- from a semi-dilute to a rather concentrated solution -- the chain connectivity and excluded volume interaction of the monomeric units have an extremely weak effect on the contribution of the electrostatic interactions of the dipolar monomeric units to the total free energy. We show that for rather weak electrostatic interactions, the electrostatic correlations manifest themselves as Keesom interactions of point-like freely rotating dipoles (Keesom regime), while in the region of strong electrostatic interactions the electrostatic free energy is described by the Debye-H{ü}ckel limiting law (Debye regime). We show that for real zwitterionic coacervates the Keesom regime is realized only for sufficiently small polymer concentrations of the coacervate phase, while the Debye regime is approximately realized for rather dense coacervates. Using the mean-field variant of the density functional theory, we calculate the surface tension (surface free energy) of the $"$coacervate-solvent$"$ interface as a function of the bulk polymer concentration. Obtained results can be used to estimate the parameters of the polymer chains needed for practical applications such as drug encapsulation and delivery, as well as the design of adhesive materials.
