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Neutron spin echo investigations on the segmental dynamics in semidilute polymer solutions under Θ- and good solvent conditions

Ewen, B. and Richter, D. and Farago, B. and Stühn, B. (1994):
Neutron spin echo investigations on the segmental dynamics in semidilute polymer solutions under Θ- and good solvent conditions.
In: Journal of Non-Crystalline Solids, pp. 1023-1027, 172, (Part 2), [Article]

Abstract

Semidilute polymer solutions can be considered as transient networks of lifetime, tau(g) and of average meshsize xi. xi depends on the polymer concentration, c, and the solvent conditions. If the segmental diffusion of such systems is studied on timescales t << tau(g), using the neutron spin echo technique, different relaxation modes and continuous transitions between them are identified by varying the magnitude of the scattering vector, q. Under good solvent conditions, a crossover from single chain Zimm dynamics, as valid in dilute solutions on the entire intramolecular length scale, to the collective many chain diffusion is found at q xi(c) approximate to 1. The corresponding relaxation rates, Omega(q), vary from Omega(q) similar to q(3) to Omega(q) similar to q(2). In Theta-solvents, the many chain regime was not accessible. However, due to the existence of self-entanglements, which introduce an additional length scale xi(i)(c) < xi(c), the crossover from disentangled (Omega(q) similar to q(3)) to entangled single chain relaxation (Omega(q) similar to q) becomes visible.

Item Type: Article
Erschienen: 1994
Creators: Ewen, B. and Richter, D. and Farago, B. and Stühn, B.
Title: Neutron spin echo investigations on the segmental dynamics in semidilute polymer solutions under Θ- and good solvent conditions
Language: English
Abstract:

Semidilute polymer solutions can be considered as transient networks of lifetime, tau(g) and of average meshsize xi. xi depends on the polymer concentration, c, and the solvent conditions. If the segmental diffusion of such systems is studied on timescales t << tau(g), using the neutron spin echo technique, different relaxation modes and continuous transitions between them are identified by varying the magnitude of the scattering vector, q. Under good solvent conditions, a crossover from single chain Zimm dynamics, as valid in dilute solutions on the entire intramolecular length scale, to the collective many chain diffusion is found at q xi(c) approximate to 1. The corresponding relaxation rates, Omega(q), vary from Omega(q) similar to q(3) to Omega(q) similar to q(2). In Theta-solvents, the many chain regime was not accessible. However, due to the existence of self-entanglements, which introduce an additional length scale xi(i)(c) < xi(c), the crossover from disentangled (Omega(q) similar to q(3)) to entangled single chain relaxation (Omega(q) similar to q) becomes visible.

Journal or Publication Title: Journal of Non-Crystalline Solids
Volume: 172
Number: Part 2
Divisions: 05 Department of Physics
05 Department of Physics > Institute for condensed matter physics
Date Deposited: 26 Feb 2010 14:12
Additional Information:

2nd International Discussion Meeting on Relaxations in Complex Systems, ALICANTE, SPAIN, JUN 28-JUL 08, 1993

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