FOLLOWUS
a.State Key Laboratory of Polymer Science and Technology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
b.School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, China
yylu@ciac.ac.cn
Received:13 June 2025,
Accepted:02 August 2025,
Published Online:11 October 2025,
Published:05 November 2025
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Ma, L. C.; Ruan, Y. J.; Lu, Y. Y.; An, L. J. Structural origins of shear banding in bidisperse polymer melts. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-025-3421-8
Li-Cheng Ma, Yong-Jin Ruan, Yu-Yuan Lu, et al. Structural Origins of Shear Banding in Bidisperse Polymer Melts[J/OL]. Chinese journal of polymer science, 2025, 431-10.
Ma, L. C.; Ruan, Y. J.; Lu, Y. Y.; An, L. J. Structural origins of shear banding in bidisperse polymer melts. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-025-3421-8 DOI:
Li-Cheng Ma, Yong-Jin Ruan, Yu-Yuan Lu, et al. Structural Origins of Shear Banding in Bidisperse Polymer Melts[J/OL]. Chinese journal of polymer science, 2025, 431-10. DOI: 10.1007/s10118-025-3421-8.
Shear banding in entangled polymer melts remains a fundamental yet unresolved phenomenon in nonlinear polymer rheology. Here
we perform molecular dynamics simulations of bidisperse entangled melts—comprising equal numbers of chains with lengths
N
=200 and
N
=400—to uncover the structural origins and dynamic evolution of shear banding. This bidisperse system amplifies spatial heterogeneities in the entanglement network and facilitates direct comparison with monodisperse melts of
N
=300
revealing quantitatively consistent steady-state shear stress versus shear rate responses. Notably
a pronounced stress plateau spanning over an order of magnitude in shear rate is observed
within which shear banding emerges reproducibly across independent simulations
as confirmed by systematic velocity profile and interface position analyses. Our findings challenge the prevailing notion that shear banding arises solely from dynamic flow instabilities. Instead
we establish a microstructure-driven framework
demonstrating that shear band nucleation is governed by pre-existing structural heterogeneities—specifically
localized weakening of the entanglement netw
ork at short-chain-enriched “soft spots”
indicative of a robust microstructural memory effect. During shear start-up
short chains preferentially disentangle and migrate along the shear direction; beyond a critical strain
long chains retract and redistribute away from the fast shear band center to minimize elastic energy. This chain-length-dependent migration dynamically enriches the shear band in short chains
stabilizing its structure and revealing a molecular mechanism that links entanglement heterogeneity to macroscopic flow localization. By bridging molecular-scale structural features with nonlinear rheological responses
this work offers a complementary perspective to classical tube and convective constraint release (CCR) models
highlighting the critical interplay between microstructural heterogeneity and chain migration in the onset and persistence of shear banding.
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