Quantifying the Effect of Multivalent Ions in Polyelectrolyte Solutions
Quantifying the Effect of Multivalent Ions in Polyelectrolyte Solutions
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DOI：
10.1021/acs.macromol.1c01326
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发表时间：
2021-10-06
期刊：
影响因子：
5.5
通讯作者：
Dobrynin, Andrey, V
中科院分区：
文献类型：
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作者：
Jacobs, Michael;Lopez, Carlos G.;Dobrynin, Andrey, V
对于具有重复单元投影长度L的聚合物，基于溶液关联长度xi=lg(Nu)/B与每个关联斑点的重复单元数g之间的关系，我们实现了一种标度方法来量化具有单价和二价反离子的羧甲基纤维素和聚苯乙烯磺酸盐溶液的性质。参数B等于B-pe、B-g、B-th和1，指数nu=1、0.588、0.5和1，在分别由交叉浓度C-D、c(Th)和c**分开的半稀聚电解质溶液、重叠静电和热滴的溶液和浓缩聚合物溶液中。利用无纠缠溶液区域的比粘度Eta(Sp)(C)与每条链的相关斑点数目N-w/g之间的线性关系，得到了B参数的值，其中重均聚合度N-w和g=B3/(3nu-1)(Cl3)(1/(1-3nu))是重复单元浓度c和不同溶液区域的B参数的函数。这一分析表明：(I)只有一小部分自由反离子，f*<；12%；(Ii)二价离子对排斥体的重整化有很强的影响，使其减少了2倍；(Iii)二价反离子对库恩长度的重整化的影响要小得多，最高可增加10%。与含有单价反离子的聚电解质溶液相比，这些效应显著地减少了链的伸展，增加了每个溶液相关长度的重复单元数，并促进了链的解缠。有迹象表明，在羧甲基纤维素的浓溶液中，有钙离子的链桥接作用，表现为溶液粘度的增加。用这组B参数计算的溶液关联长度Xi的浓度依赖关系与由浓度c<；c(D)的散射函数的峰位得到的结果一致。
We implemented a scaling approach, based on the relationship between the solution correlation length xi = lg(nu)/B and the number of repeat units per correlation blob g for polymers with repeat unit projection length l, to quantify properties of solutions of carboxymethylcellulose and polystyrene sulfonate with monovalent and divalent counterions. The parameter B is equal to B-pe, B-g, B-th, and 1, and the exponent nu = 1, 0.588, 0.5, and 1 in semidilute polyelectrolyte solutions, solutions of overlapping electrostatic and thermal blobs, and concentrated polymer solutions, which are separated by crossover concentrations C-D, c(th), and c**, respectively. The values of the B-parameters are obtained using the linear relationship between the specific viscosity eta(sp)(c) in the unentangled solution regime and the number of correlation blobs N-w/g per chain, with the weight-average degree of polymerization, N-w, and g = B3/(3 nu-1)(cl(3))(1/(1-3 nu)) as a function of the repeat unit concentration, c, and the B-parameters in different solution regimes. This analysis shows that (i) there is only a small fraction of free counterions, f* < 12%; (ii) divalent ions have a strong effect on the renormalization of the excluded volume, reducing it by a factor of 2; and (iii) the effect of divalent counterions is much weaker on the renormalization of the Kuhn length, accounting for an increase of up to 10%. In combination, these effects significantly reduce chain stretching, increase the number of repeat units per solution correlation length, and promote chain disentanglement in polyelectrolyte solutions with divalent ions in comparison with that in solutions with monovalent counterions. There is an indication of chain bridging by Ca2+ ions in concentrated solutions of carboxymethylcellulose, manifested as an increase in solution viscosity. The concentration dependence of the solution correlation length xi calculated using the set of B-parameters is in good agreement with that obtained from the peak position of the scattering function for concentrations c < c(D).