Paper Number
SM26
Session
Polymer Solutions and Melts
Title
Finite cohesion due to chain entanglement in polymer melts
Presentation Date and Time
October 7, 2014 (Tuesday) 4:00
Track / Room
Track 3 / Commonwealth C
Authors
- Cheng, Shiwang (University of Akron, Department of Polymer Science)
- Lu, Yuyuan (Changchun Institute of Applied Chemistry)
- An, Lijia (Changchun Institute of Applied Chemistry)
- Wang, Zhen-Gang (California Institute of Technology)
- Wang, Shi-Qing (University of Akron)
Author and Affiliation Lines
Shiwang Cheng1, Yuyuan Lu2, Lijia An2, Zhen-Gang Wang3, and Shi-Qing Wang1
1Department of Polymer Science, University of Akron, Akron, OH; 2Changchun Institute of Applied Chemistry, Changchun, China; 3California Institute of Technology, Pasadena, CA
Speaker / Presenter
Cheng, Shiwang
Text of Abstract
Stress relaxation and delayed rate-switching during stress relaxation from step-wise deformation are carried out using a SER fixture to elucidate the existence of a finite entropic barrier against chain retraction. The stress relaxation experiment reveals identical relaxation modulus as a function of time below a threshold strain, where the relaxation is quiescent. Specifically, there is little hastened stress relaxation for step shear up to amplitude of gamma = 0.7 and for step extension up to a stretching ratio lamda = 1.5. This contrasts sharply with the theoretical description based on the most sophisticated tube theory (GLaMM). A sudden application of startup extension during different stages of the stress relaxation after a step-wise extension, i.e., the delayed-rate-switching experiment, suggests that the effect of chain stretching, leading to a transverse geometric condensation of entanglement strands, survives well beyond the Rouse time tR. In contrast, the GLaMM calculation shows that chain retraction takes place right away at any amplitude of the step-wise extension and the effect of geometric condensation decays from the onset of the relaxation.