Orientation relaxation of linear chains enclosed in a network studied by birefringence measurements

 The relaxation of linear poly(styrene sulfonate) chains in a swollen poly(acrylamide) network is investigated by birefringence measurements. After a stepwise deformation of the network relaxation occurs, because the linear chains are initially deformed as well, but diffuse into an isotropic conformation via the reptation mechanism. The course of the birefringence with time agrees essentially with what follows from the reptation model. It could be shown that the relaxation time varies approximately with the third power of the molar mass of the enclosed molecules when networks of sufficiently high network density are used. On the other hand, the dependence of the relaxation time on network density or degree of swelling, respectively, seems to be much stronger than what is expected from theory. Received: 9 September 1996 Accepted: 25 November 1996