Dynamics of entangled H-polymers: theory, rheology, and neutron-scattering

McLeish, T. C. B. ; Allgaier, J. ; Bick, D. K. ; Bishko, G. ; Biswas, P. ; Blackwell, R. ; Blottière, B. ; Clarke, N. ; Gibbs, B. ; Groves, D. J. ; Hakiki, A. ; Heenan, R. K. ; Johnson, J. M. ; Kant, R. ; Read, D. J. ; Young, R. N. (1999) Dynamics of entangled H-polymers: theory, rheology, and neutron-scattering Macromolecules, 32 (20). pp. 6734-6758. ISSN 0024-9297

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ma990323j

Related URL: http://dx.doi.org/10.1021/ma990323j


We present experiments and theory on the melt dynamics of monodisperse entangled polymers of H-shaped architecture. Frequency-dependent rheological data on a series of polyisoprene H-polymers are in good agreement with a tube model theory that combines path-length fluctuation (like that of star polymer melts) at high frequency, with reptation of the self-entangled “cross-bars” at low frequencies (like that of linear polymer melts). We account explicitly for mild polydispersity. Nonlinear step-strain and transient data in shear and extension confirm the presence of a relaxation time not seen in linear response, corresponding to the curvilinear stretch of the cross-bars. This time is very sensitive to strain due to the exponential dependence of the branch-point friction constants on the effective dangling path length. Strain-induced rearrangements of the branch points are confirmed by small-angle neutron scattering (SANS) on stretched and quenched partially deuterated samples. We develop an extension of melt-scattering theory to deal with the presence of deformed tube variables to interpret the SANS data.

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ID Code:102590
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