VISCOELASTIC PROPERTIES OF THERMOREVERSIBLE GELATION OF ATACTIC POLYSTYRENE

The gelation of several samples of atactic polystyrene (aPS) in CS2 is studied by rheological methods. The Young's modulus and the loss and storage moduli are measured as a function of temperature in the sol an d gel phases. In the sol phase the concentration dependence of the pla teau modulus, G(N), is found to be in good agreement with the theoreti cal predictions. The sol-gel transition is accompanied by an abrupt in crease of G(N), which shows the formation of additional entanglements with respect to the sol. For temperatures, T, below the gelation tempe rature, T(gel), G(N) does not vary with temperature and the gel seems to reach a final structure at T = T(gel), - 10-degrees-C. These behavi ours, which are independent of the aPS molecular weight, are discussed in relation to other experimental investigations (phase diagram, anis otropic light scattering, neutron scattering).