Study on Structure-Rheology Relationships in Multiphase Polymeric Systems

Abstract

Structure-rheology relationships have been studied on polymer blends, block copolymers and polymer composites. The excess shear stress of polymer blends with droplet/matrix structure after application of a large step shear strain is predicted fairly well by the Doi-Ohta theory, when the interface tensor describing the anisotropy of the interface can be evaluated from observation of the deformed interface shape. The frequency dependence of storage G' and loss moduli G" of polymer blends with bicontinuous structure shows a power law behavior with exponent of 0.75 - 0.83. For diblock, triblock and starblock copolymers with lamellar, cylinder and gyroid structures, power law exponents for the frequency dependences of G' are found to be 1/2, 1/3 - 1/5 and 0, respectively. The power law exponent for G' is sensitive to the curved structure in cylinder-forming samples, while the exponent is always 1/2 in lamellar-forming samples. The structure-rheology relationships are investigated for composites in which ceramics particles are dispersed in polymer blends with bicontinuous structure. It has been found that particles enter exclusively into one phase in binary polymer blends, when flexible polymer chains in that phase adsorb onto those particles and better compatibility than other polymer phase is obtained. The dispersed state of particles in the polymer phase is correlated with G' behavior at low and intermediate frequencies.