Conformation and Phase Behavior of Sodium Carboxymethyl Cellulose in the Presence of Mono- and Divalent Salts
Conformation and Phase Behavior of Sodium Carboxymethyl Cellulose in the Presence of Mono- and Divalent Salts
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单价和二价盐存在下羧甲基纤维素钠的构象和相行为
DOI：
10.1021/acs.macromol.9b02228
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发表时间：
2020
期刊：
影响因子：
5.5
通讯作者：
Sharratt W
中科院分区：
文献类型：
--
作者：
Sharratt W
用小角中子散射（SANS）方法研究了羧甲基纤维素钠（NaCMC）在一价（Na+）和二价盐（Mg ~（2+）、Ca ~（2+）、Zn ~（2+）和Ba ~（2+））存在下的半稀释水溶液。选择1.3的取代度以确保聚合物在无盐溶液中分子溶解。我们发现，Na+和Mg 2+盐的添加产生H型相行为，而Ca 2+，Zn 2+，和Ba 2+，而不是产生一个混合的H/L型相行为依赖于NaCMC浓度（CP），在降低的顺序诱导浊度所需的盐浓度（在固定CP）。通过添加NaCl的电荷屏蔽诱导的特征的相关峰的消失，并最终产生散射轮廓与aq-1的依赖性在近30年的波数q。通过对过量Na+数据的描述性模型拟合，得到了与cpin g L-1的相关长度为1030 cp-0.72cp。添加不与NaCMC羧酸根基团特异性相互作用的Mg 2+产生与Na+类似的筛选行为，尽管在较低的盐浓度下，与其较高的离子强度一致。在低盐浓度下，加入特异性相互作用的Ca 2+、Zn 2+和Ba 2+会产生相对较大的λ相关峰的屏蔽，并且在高于相边界的浓度下，会导致在低q下的过度散射，与20-40 nm簇的形成相容。这种行为被解释为由于电荷密度沿着链降低，促进链间缔合和多链域形成，导致可见浑浊。总的来说，绘制类比与NaCMC在较低程度的取代，其中发生疏水缔合，我们的研究结果提供了一个框架来描述溶液结构和相行为的NaCMC在无盐和盐的解决方案。
We report a small-angle neutron scattering (SANS) study of semidilute aqueous solutions of sodium carboxymethyl cellulose (NaCMC), in the presence of mono- (Na+) and divalent salts (Mg2+, Ca2+, Zn2+, and Ba2+). A degree of substitution of 1.3 is selected to ensure that, in salt-free solution, the polymer is molecularly dissolved. We find that Na+and Mg2+salt addition yields H-type phase behavior, while Ca2+, Zn2+, and Ba2+instead yield a mixed H/L-type phase behavior dependent on the NaCMC concentration (cp), in the decreasing order of the salt concentration required to induce turbidity (at a fixedcp). Charge screening by addition of NaCl induces the disappearance of the characteristic polyelectrolyte correlation peak and eventually yields scattering profiles with aq–1dependence over nearly 3 decades in the wavenumberq. By fitting a descriptive model to data with excess Na+, we obtain a correlation length ξ′ = 1030cp–0.72Å withcpin g L–1. Addition of Mg2+, which does not interact specifically with NaCMC carboxylate groups, yields an analogous screening behavior to that of Na+, albeit at lower salt concentrations, in line with its higher ionic strength. At low salt concentration, addition of specifically interacting Ca2+, Zn2+, and Ba2+yields a comparatively greater screening of the polyelectrolyte correlation peak, and at concentrations above the phase boundary, results in excess scattering at low-q, compatible with the formation of 20–40 nm clusters. This behavior is interpreted as due to the reduction in charge density along the chain, promoting interchain association and multichain domain formation resulting in visible turbidity. Overall, drawing analogies with NaCMC at a lower degree of substitution, where hydrophobic association takes place, our findings provide a framework to describe the solution structure and phase behavior of NaCMC in salt-free and salt solutions.
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聚电解质中的沉淀对盐添加的影响
DOI：
10.1002/polb.1993.090310213
发表时间：
1993
期刊：
Journal of Polymer Science Part B
影响因子：
--
作者：
K. A. Narh;A. Keller
通讯作者：
A. Keller
影响因子：
4.4
作者：
BOUE, F;COTTON, JP;JANNINK, G
通讯作者：
JANNINK, G
DOI：
--
发表时间：
2019
期刊：
影响因子：
--
作者：
C. G. Lopez
通讯作者：
C. G. Lopez
影响因子：
3.4
作者：
IKEGAMI, A;IMAI, N
通讯作者：
IMAI, N
影响因子：
4.6
作者：
R. Schweins;J. Hollmann;K. Huber
通讯作者：
R. Schweins;J. Hollmann;K. Huber