Evolution of Chain Conformation and Entanglements during Startup Shear

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• 作者：Yuyuan Lu ; Lijia An ; Shi-Qing Wang ; Zhen-Gang Wang
• 刊名：ACS Macro Letters
• 出版年：2013
• 出版时间：June 18, 2013
• 年：2013
• 卷：2
• 期：6
• 页码：561-565
• 全文大小：305K
• 年卷期：v.2,no.6(June 18, 2013)
• ISSN：2161-1653

文摘

Using Brownian dynamics simulation, we determine chain dimensions in an entangled polymer melt undergoing startup shear at a rate lower than the reciprocal of the Rouse time yet higher than the reciprocal reptation time. Here the tube model expects negligible chain stretching. In contrast, our simulation shows the deformed coil to conform closely to affine deformation. We find that the total number of entanglements decreases with increasing shear. Remarkably, up to many Rouse time, the decline in the number of initial entanglements is slower than that under the quiescent condition. These results point to fundamental deficiencies in the molecular picture of the tube model for startup shear.