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首页> 外文期刊>Journal of chromatography, A: Including electrophoresis and other separation methods >Evaluation of molecular mass and tacticity of polyvinyl alcohol by non-equilibrium capillary electrophoresis of equilibrium mixtures of a polymer and a dye
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Evaluation of molecular mass and tacticity of polyvinyl alcohol by non-equilibrium capillary electrophoresis of equilibrium mixtures of a polymer and a dye

机译：通过聚合物和染料的平衡混合物的非平衡毛细管电泳评估聚乙烯醇的分子量和立构规整度

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Non-equilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) has been used to characterize polyvinyl alcohol (PVA). Commercial PVA samples with different molecular masses, from M_w=15 up to 205kDa, were used. According to the ~(13)C NMR spectra, the samples also differed in tacticity (stereoregularity). Mixtures of PVA and the anionic azo-dye Congo Red (CR) were injected in the presence of a borate buffer. The electropherograms gave a band and a peak due to the residual PVA-CR complex and the excess dye, respectively, plus a superimposed exponential decay due to the partial dissociation of the complex during migration. The stoichiometry of the PVA-CR complex, q=[monomer]/[dye], reached a maximum, q_(sat), which depended on both M_w and tacticity of PVA. Thus, q_(sat) decreased from a molar ratio of ca. 4.9 to 3.6 at increasing M_w values, this variation also being largely dependent on tacticity. A similar dependence of the electrophoretic mobility of the complex on both M_w and tacticity was also observed. A possible explanation, based on the formation of a stack of CR ions inside the PVA-CR complex, was proposed and discussed. Finally, at increasing M_w values, the stability constant of the complex increased slightly, and the pseudo-first order dissociation rate of the complex decreased, this later parameter also showing a dependence on both M_w and tacticity.
机译：平衡混合物的非平衡毛细管电泳（NECEEM）已用于表征聚乙烯醇（PVA）。使用具有从M_w = 15到205kDa的不同分子量的商业PVA样品。根据〜（13）C NMR光谱，样品的立构规整度（立体有规性）也不同。在硼酸盐缓冲液的存在下，注入PVA和阴离子偶氮染料刚果红（CR）的混合物。电泳图分别给出了由于残留的PVA-CR配合物和过量的染料引起的谱带和峰，以及由于在迁移过程中配合物的部分解离而导致的叠加指数衰减。 PVA-CR配合物的化学计量为q = [单体] / [染料]，达到最大值q_（sat），这取决于MVA和PVA的规整度。因此，q_（sat）从大约ca的摩尔比降低。在M_w值增加时，从4.9到3.6，这种变化在很大程度上还取决于战术性。还观察到复合物的电泳迁移率对M_w和立构规整度的相似依赖性。提出并讨论了基于在PVA-CR络合物内部形成CR离子堆栈的可能解释。最后，随着M_w值的增加，配合物的稳定常数略有增加，配合物的拟一阶解离速率降低，此后一个参数也显示出对M_w和立构规整度的依赖性。

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