Determining the Molecular Weight of Polyelectrolytes Using the Rouse Scaling Theory for Salt-Free Semidilute Unentangled Solutions
Determining the Molecular Weight of Polyelectrolytes Using the Rouse Scaling Theory for Salt-Free Semidilute Unentangled Solutions
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DOI：
10.1021/acs.macromol.2c01007
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发表时间：
2022-08
期刊：
影响因子：
5.5
通讯作者：
A. Han;Veera Venkata Shravan Uppala;D. Parisi;C. George;Benjamin J. Dixon;Camila Denise Ayala;Xiuli Li;L. Madsen;R. Colby
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文献类型：
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作者：
A. Han;Veera Venkata Shravan Uppala;D. Parisi;C. George;Benjamin J. Dixon;Camila Denise Ayala;Xiuli Li;L. Madsen;R. Colby
基于Rouse标度模型，可以使用半稀释非缠结区域中的链动力学来确定聚电解质的分子量。有四种方法可以通过小角X射线散射测量相关长度（λ）、通过流变仪测量比粘度（ηsp）和弛豫时间（τ）以及通过NMR测量扩散系数（D）来确定链的数密度。研究了五种窄分散性聚苯乙烯磺酸铯（CsPSS）无盐溶液在水、无水乙二醇和无水甘油中的情况，以测试所有方法。结合粘度和相关长度，根据劳斯模型得出重均分子量（Mw）。结合水中的扩散系数和相关长度，可以可靠地提供N < 2000重复单元的链的数均分子量（Mn）。甘油减慢松弛动力学，并且粘度的剪切速率依赖性产生N> 100的CsPSS的可靠τ，其由Rouse模型中的z-平均和z + 1平均分子量（MzMz+1）的乘积控制。通过流变学测定的末端模量G =（η - ηs）/τ与Mw/Mz Mz +1相关。
Chain dynamics in the semidilute unentangled regime can be used to determine the molecular weight of polyelectrolytes based on the Rouse scaling model. Four methods enable determination of the number density of chains via measurements of correlation length (ξ) by small-angle X-ray scattering, specific viscosity (ηsp) and relaxation time (τ) by rheometry, and diffusion coefficient (D) by NMR. Five narrow dispersity cesium polystyrene sulfonate (CsPSS) solutions without salt are studied in water, anhydrous ethylene glycol, and anhydrous glycerol to test all methods. Combining viscosity and correlation length yields the weight-average molecular weight (Mw) from the Rouse model. Combining diffusion coefficient and correlation length in water provides number-average molecular weight (Mn) reliably for chains withN< 2000 repeat units. Glycerol slows relaxation dynamics, and the shear rate dependence of viscosity yields reliable τ for CsPSS withN> 100, which is governed by the product of z-average and z + 1 average molecular weight (MzMz+1) in the Rouse model. Terminal modulusG= (η – ηs)/τ via rheometry correlates withMw/MzMz+1.