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首页> 外文期刊>Journal of Applied Polymer Science >IMPROVED ACCURACY AND PRECISION IN THE LIGHT-SCATTERING CHARACTERIZATION OF HOMO- AND COPOLYMERS IN THF
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IMPROVED ACCURACY AND PRECISION IN THE LIGHT-SCATTERING CHARACTERIZATION OF HOMO- AND COPOLYMERS IN THF

机译：THF中均聚物和共聚物的光散射表征中提高的准确性和精度

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A one-point method was developed for the estimation of weight-averaged molecular weights from light-scattering data. The method is based on the calculation of the second virial coefficient from theoretical predictions of the dependence of Az on the molecular weight. The second virial coefficient is then regressed for a particular polymer-solvent combination from a series of preexisting measurements over a range of molecular weights. The one-point method is found to yield as accurate molecular weight estimates as obtained from a Debye plot using the conventional dilution technique. The variance in the estimation of the Rayleigh factor has also been found to be highly dependent on the measurement concentration. Therefore, the precision in the estimation of molecular weight can be improved by calculating molecular weights at or near the optimal concentration, which is itself molecular weight-dependent. The one-point method is demonstrated for poly(methyl methacrylate)s of various polydispersities in tetrahydrofuran. The molecular weight of polystyrene and polystyrene-coacrylic acid were also estimated by the one-point method in THF. In the case of the polystyrene-co-acrylic acid, THF becomes a poorer solvent with increasing levels of acrylic acid in the copolymer, and the parameter (A(2)M(0.5)) is found to vary with the copolymer composition, as is theoretically predicted. (C) 1997 John Wiley & Sons, Inc. [References: 40]
机译：开发了一种单点方法，可根据光散射数据估算重均分子量。该方法基于第二维里系数的计算，该第二维里系数是根据Az相对于分子量的理论预测得出的。然后，根据一系列在分子量范围内预先存在的测量结果，对特定的聚合物-溶剂组合，计算出第二维里系数。发现单点方法可产生准确的分子量估算值，如使用常规稀释技术从德拜图获得的那样。还发现瑞利因子估计中的方差高度依赖于测量浓度。因此，可以通过计算最佳浓度或最佳浓度的分子量来提高分子量估计的精度，最佳浓度本身就是分子量依赖性的。证明了在四氢呋喃中具有各种多分散性的聚（甲基丙烯酸甲酯）的单点方法。聚苯乙烯和聚苯乙烯-共丙烯酸的分子量也通过单点法在THF中估算。在聚苯乙烯-共丙烯酸的情况下，随着共聚物中丙烯酸含量的增加，THF成为较差的溶剂，并且发现参数（A（2）M（0.5））随共聚物组成而变化，因为在理论上是预测的。 （C）1997 John Wiley＆Sons，Inc. [参考：40]

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