ANISOTROPIC LIGHT-SCATTERING AND RHEOLOGICAL STUDY OF THE PHYSICAL GELATION OF ATACTIC POLYSTYRENE IN CARBON-DISULFIDE

The physical gelation of the solutions of atactic polystyrene (aPS) in carbon disulfide (CS2) is studied by the excess of anisotropic light scattering delta H-nu and by the theological properties. An abrupt jum p of delta H-nu at gelation temperature shows that a part of the chain s are stiffened upon gelation. This effect which is independent of aPS molecular weight strongly decreases with concentration. It is well co rrelated with an abrupt change of the plateau modulus G(N) which indic ates the formation of additional entanglements in the gel phase with r espect to the sol. The compatibility of these abrupt jumps with the th ermodynamic theories used to interpret the concentration and molecular -weight dependence of the gelation temperature is discussed.