Gallegos Alejandro, Ong Gary M C, Wu Jianzhong
Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA.
Soft Matter. 2021 Oct 20;17(40):9221-9234. doi: 10.1039/d1sm00848j.
Polymer ionization differs from that for their monomeric counterparts due to intramolecular correlations. Such effects are conventionally described in terms of the site-binding model that accounts for short-range interactions between neighboring sites. With an apparent equilibrium constant for each ionizable group and the nearest-neighbor energy as adjustable parameters, the site-binding method is useful to correlate experimental titration curves when the site-site interactions are insignificant at long ranges. This work aims to describe the electrostatic behavior of weak polyelectrolytes in aqueous solutions on the basis of the intrinsic equilibrium constants of the individual ionizable groups and solution conditions underlying the thermodynamic non-ideality. A molecular thermodynamic model is proposed for the protonation of weak polyelectrolytes by incorporating classical density functional theory into the site-binding model to account for the effects of the local ionic environment on both inter-chain and intra-chain correlations. By an extensive comparison of theoretical predictions with experimental titration curves, we demonstrate that the thermodynamic model is able to quantify the ionization behavior of weak polyelectrolytes over a broad range of molecular architectures and solution conditions.
由于分子内相关性，聚合物的电离不同于其单体对应物的电离。这种效应通常根据位点结合模型来描述，该模型考虑了相邻位点之间的短程相互作用。以每个可电离基团的表观平衡常数和最近邻能量作为可调参数，当位点间相互作用在长程范围内不显著时，位点结合方法有助于关联实验滴定曲线。这项工作旨在基于各个可电离基团的固有平衡常数和热力学非理想性背后的溶液条件，描述弱聚电解质在水溶液中的静电行为。通过将经典密度泛函理论纳入位点结合模型，提出了一个用于弱聚电解质质子化的分子热力学模型，以考虑局部离子环境对链间和链内相关性的影响。通过将理论预测与实验滴定曲线进行广泛比较，我们证明了该热力学模型能够在广泛的分子结构和溶液条件下量化弱聚电解质的电离行为。
