Charged Polymers: From Polyelectrolyte Solutions to Polyelectrolyte Complexes
Charged Polymers: From Polyelectrolyte Solutions to Polyelectrolyte Complexes
复制标题
DOI：
10.1021/acs.macromol.1c01171
复制
发表时间：
2021-07-22
期刊：
影响因子：
5.5
通讯作者：
Dobrynin, Andrey, V
中科院分区：
文献类型：
--
作者：
Sayko, Ryan;Tian, Yuan;Dobrynin, Andrey, V
采用粗粒化分子动力学模拟、无规相近似（RPA）方法和标度分析研究了聚合度N+ = 400的带正电链及其与聚合度N_（10 ~ 400）的带负电链的混合物浓溶液的静态和动态性质.模拟结果表明，随着单体浓度的增加，链的有效Kuhn长度和均方端到端距离均减小，说明静电相互作用受到周围链的屏蔽.结构因子S（q）在中间波数q* 处有一个特征峰，其位置随单体浓度的降低而向较小的q值移动。结果表明，在小的q的S（q）的平台是由系统的可压缩性和增加的负电荷链的聚合度的增加。这些结果与以中性链为参考系的RPA方法计算的S（q）一致。在该方法的框架中，散射函数中最大值的位置在q* 尺度下，单体浓度为rho（-0.25）。对带相反电荷的混合链的动力学分析表明，链松弛是一个约束释放和链爬行过程的组合。约束释放被证明是在混合物中的主要机制与带负电荷的链具有中间聚合度。发现对于带电系统，管和超级管的缠结之间的聚合度Ne与浓度成比例，N-e类似于ρ（-2），相应的填充数P-e = 18.45 +/-0.93。这与中性链的混合物相反，其中除了类似于rho（-2）标度的N-e之外，超级管的缠结之间的聚合度遵循类似于rho（-4/3）的标度N-e，其中填充数P-e = 6.64 +/-0.19。
Coarse-grained molecular dynamics simulations, random phase approximation (RPA) approach, and scaling analysis are used to study static and dynamic properties of concentrated polyelectrolyte solutions of positively charged chains with the degree of polymerization N+ = 400 and their mixtures with negatively charged chains with degrees of polymerization N_ varying between 10 and 400. Simulations show that both the effective chain Kuhn length and mean-square end-to-end distance of a chain decrease with increasing monomer concentration, pointing out screening of the electrostatic interactions by surrounding chains. The structure factor S(q) has a characteristic peak at intermediate wavenumbers q* which location moves toward smaller q values with decreasing monomer concentration. It is demonstrated that the plateau in S(q) at a small q is controlled by system compressibility and increases with increasing degree of polymerization of negatively charged chains. These results are in agreement with S(q) calculated in the framework of the RPA approach considering a solution of neutral chains as a reference system. In the framework of this approach, the location of the maximum in the scattering function at q* scales with monomer concentration as rho(-0.25). Analysis of the chain dynamics in the mixtures of oppositely charged chains shows that chain relaxation is a combination of constraint release and chain reptation processes. Constraint release is demonstrated to be the dominant mechanism in mixtures with negatively charged chains having intermediate degrees of polymerization. The degree of polymerization Ne between entanglements of the tube and super tube for charged systems is found to scale with concentration as N-e similar to rho(-2) with corresponding packing numbers P-e = 18.45 +/- 0.93. This is in contrast with mixtures of neutral chains, where in addition to N-e similar to rho(-2) scaling, the degree of polymerization between entanglements of the super tube follows scaling N-e similar to rho(-4/3) with packing number P-e = 6.64 +/- 0.19.