A novel approach to investigating the rheology of miscible polymer blends is described based on complementary infrared polarimetry and mechanical rheometry measurements. The method provides a means by which the blend dynamic modulus G*(ω) 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-dichroism and birefringence experiments to those of dynamic shear stress experiments through the use of constitutive relations and the application of the stress-optic rule. The approach is extended to cover blend systems which exhibit orientational coupling, an effect which influences 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 (Mw = 75 000), and 1,2-polybutadiene, 1,2-PB (Mw = 204 000), containing a fraction of deuterium-labeled PI chains (Mw = 90 000). Orientational coupling in this blend is observed and is found to be characterized by a coupling coefficient ϵ = 0.35 ± 0.05.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry