Flow birefringence at the sol-gel transition

2014 The information provided by a flow birefringence experiment at the sol-gel transition in the sol phase is discussed There are two competing effects : cluster rotations, and cluster elastic deformation. In a steady state, rotational effects turn out to be dominant. For small velocity gradients S we predict an extinction angle x such that 03C0/4 x diverges with an exponent roughly equal to 3.4 i.e. a very strong effect In the vicinity of the transition, the birefringence 0394n has the same divergence as the macroscopic viscosity. J. Physique 43 (1982) 467-473 MARS 1982, Classification Physics Abstracts 61.40K 82.70 47.20 05.50