Paper Number
SM16 

Session
Polymers Solutions, Melts and Blends

Title
Rheo-dielectrics and diffusion of type-A Rouse chain under fast shear flow: Method of evaluation of non-equilibrium parameters for FENE, friction-reduction, and Brownian force intensity variation

Presentation Date and Time
October 10, 2022 (Monday) 5:05

Track / Room
Track 2 / Sheraton 3

Authors (Click on name to view author profile)

1. Watanabe, Hiroshi (Institute for Chemical Research, Kyoto University)
2. Matsumiya, Yumi (Institute for Chemical Research, Kyoto University)
3. Sato, Takeshi (Institute for Chemical Research, Kyoto University)

Author and Affiliation Lines (in printed abstract book)
Hiroshi Watanabe, Yumi Matsumiya and Takeshi Sato
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan

Speaker / Presenter 
Watanabe, Hiroshi

Keywords
experimental methods; theoretical methods; polymer melts

Text of Abstract
Rouse model is the basic molecular model for unentangled linear polymer melts. This model is characterized by the spring strength κ, the segmental friction coefficient ζ, and the mean-square Brownian force intensity B. Recent studies suggest that these Rouse parameters change under fast flow thereby providing significant rheological nonlinearities [Macromolecules, 54, 3700 (2021)]. In this study, we theoretically analyze effects of the flow-induced changes of these parameters on the dielectric and diffusion behavior of the Rouse chain with type-A dipoles parallel along the chain backbone. It turned out that complex dielectric permittivity ε* normalized by its equilibrium value under steady shear is characterized by non-equilibrium parameters, r_κ=κ/κ_eq and r_ζ,ij=ζ_ij/ζ_eq but irrelevant to r_B,ij=B_ij/B_eq, where the subscript “eq” stands for the quantities at equilibrium and the subscripts “ij” (i and/or j = x, y, and z) denote the spatial direction under shear flow. Thus, the obtained analytical expression enables us to evaluate these parameters from data of the dielectric relaxation time and intensity under steady shear. In contrast, the advective diffusion behavior under steady shear is determined by r_ζ,ij and r_B,ij but irrelevant to r_κ. The mean-square displacement of the center of mass defined with respect to the known non-diffusive advection point is analytically expressed in terms of r_ζ,ij and r_B,ij, thereby allowing us to evaluate r_B,ij from the diffusion data under steady shear and the dielectrically determined r_ζ,ij. The method to experimentally evaluate the non-equilibrium parameters presented in this study provides us with a complementary basis to analyze nonlinear rheological behavior of unentangled melts.