Viscometric properties of block polymers near a critical point.

The three viscometric coefficients for the disordered phase of a diblock copolymer melt near its critical point are calculated from a dynamical mean field theory. The zero-shear rate limit of these coefficients are respectively the steady shear viscosity eta, the first normal stress coefficient psi sub 1, and the second normal stress coefficient psi sub 2. We find that all three coefficients are singular as the critical point is approached, scaling respectively as a sup (-3/2), a sup (-5/2), and a sup (-5/2), where a = 2(chi N) sub 8 - 2 chi N is a measure of the temperature difference from criticality. Chi is the usual Flory interaction parameter, chi sub 8 is its value on the classical (Leibler) spinodal, and N is the total number of Kuhn segments on each block copolymer chain.