COIL STRETCH TRANSITIONS IN MIXED SHEAR AND EXTENSIONAL FLOWS OF DILUTE POLYMER-SOLUTIONS
COIL STRETCH TRANSITIONS IN MIXED SHEAR AND EXTENSIONAL FLOWS OF DILUTE POLYMER-SOLUTIONS
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DOI：
10.1021/ma00197a022
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发表时间：
1989-07-01
期刊：
影响因子：
5.5
通讯作者：
MAGDA, JJ
中科院分区：
文献类型：
--
作者：
LARSON, RG;MAGDA, JJ
Zimm的珠弹簧模型的稀释溶液的灵活的聚合物，占线圈扭曲的影响，流体动力学相互作用的概括是用来计算一般平面流的分子扭曲和线圈拉伸过渡。将任意不可压缩平面流动表示为剪切流动和平面伸展的叠加，我们发现剪切流动可以降低产生螺旋-伸展转变所需的临界伸展速率cc，而原始Zimm理论预测剪切对ec没有影响。de Gennes的标度理论预言的剪切对jc的影响比在珠-弹簧计算中得到的要大得多，这显然是因为de Gennes假定的圆柱形不能准确地描述真实的相变前螺旋形状。我们的计算中cc对剪切的依赖性较弱，这与Dunlap和Leal最近的实验数据是一致的。
A generalization of Zimm’s bead-spring model for dilute solutions of flexible polymers that accounts for the influence of coil distortion on hydrodynamic interactions is used to calculate molecular distortions and coil-stretch transitions in general planar flows. Expressing an arbitrary incompressible planar flow as a superposition of a shearing flow and a planar extension, we find that the shearing flow can reduce the critical extension rate cc required to produce a coil-stretch transition, whereas theoriginal Zimm theory predicts no influence of shearing on ec. The scaling theory of de Gennes predicts a much larger influence of shearing on jc than is obtained in the bead-spring calculations, apparently because the cylindrical shape assumed by de Gennes does notaccurately describe the true pretransition coil shape. The weaker dependence of cc on shearing foundin our calculations is consistent with recent experimental data of Dunlap and Leal.