Rathee Vikramjit S, Sidky Hythem, Sikora Benjamin J, Whitmer Jonathan K
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
Polymers (Basel). 2019 Jan 21;11(1):183. doi: 10.3390/polym11010183.
The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in the process. One must contend with the inherent structural and solvation properties of the polymer, the presence of counterions, and local chemical equilibria enforced by background salt concentration and solution acidity. Moreover, for these cases, the systems of interest have locally high concentrations of monomers, induced by polymer connectivity or confinement, and thus deviate from ideal titration behavior. This work furthers knowledge in this limit utilizing hybrid Monte Carlo⁻Molecular Dynamics simulations to investigate the influence of salt concentration, pK a , pH, and counterion valence in determining the coil-to-globule transition of poorly solvated weak polyelectrolytes. We characterize this transition at a range of experimentally relevant salt concentrations and explicitly examine the role multivalent salts play in determining polyelectrolyte ionization behavior and conformations. These simulations serve as an essential starting point in understanding the complexation between weak polyelectrolytes and ion rejection of self-assembled copolymer membranes.
弱聚电解质的滴定行为非常重要，因为它们在包括纳滤和药物递送应用在内的新技术中有所应用。由于该过程涉及的系统较为复杂，目前缺乏有关条件下聚电解质滴定的全面情况。人们必须应对聚合物固有的结构和溶剂化性质、抗衡离子的存在以及由背景盐浓度和溶液酸度所强制的局部化学平衡。此外，对于这些情况，由于聚合物的连接性或受限作用，所关注的系统具有局部高浓度的单体，因此偏离了理想的滴定行为。这项工作利用混合蒙特卡罗-分子动力学模拟进一步拓展了这方面的知识，以研究盐浓度、pKa、pH值和抗衡离子价态在确定溶剂化不良的弱聚电解质的线团-球粒转变中的影响。我们在一系列实验相关的盐浓度下表征了这种转变，并明确研究了多价盐在确定聚电解质电离行为和构象中所起的作用。这些模拟是理解弱聚电解质之间的络合以及自组装共聚物膜的离子排斥的重要起点。
