MEASURING COMPONENT CONTRIBUTIONS TO THE DYNAMIC MODULUS IN MISCIBLE POLYMER BLENDS

A novel approach to investigating the theology of miscible polymer ble nds is described based on complementary infrared polarimetry and mecha nical rheometry measurements. The method provides a means by which the blend dynamic modulus G(omega) may be separated into the individiual contributions due to each of the blend components. This separation is made possible by converting the observables of dynamic infrared 1,3-d ichroism and birefringence experiments to those of dynamic shear stres s experiments through the use of constitutive relations and the applic ation of the stress-optic rule. The approach is extended to cover blen d systems which exhibit orientational coupling, an effect which influe nces the optical anisotropies but does not contribute to the state of stress. Validity of the analysis technique is demonstrated by studying highly entangled miscible blends of 1,4-polyisoprene, PI (M(w) = 75 0 00), and 1,2-polybutadiene, 1,2-PB (M(w) = 204 000), containing a frac tion of deuterium-labeled PI chains (M(w) = 90 000). Orientational cou pling in this blend is observed and is found to be characterized by a coupling coefficient epsilon = 0.35 +/- 0.05.