Thermodynamics of plasticized triblock copolymers. Part II: Model verification by light transmittance and rheology

Abstract An earlier paper proposed a theoretical model for the thermodynamics of microphase separation in a plasticized triblock copolymer. Data on laser light transmission through plasticized films and on dynamic viscosity: of these films are presented in support of model predictions. Two styrenebutadiene‐styrene copolymers were tested: Kraton 1101 with block weights (12.5‐75‐12.5) × 10 3 and TR‐41‐1467 with weights (9.6‐47.5‐9.4) × 10 3 using the solvent dipentene (p‐mentha 1, 8 diene), which is favorable for both blocks. The role of such solvents is to depress the temperature of microphase separation, T s . Optical and rheological measurements of T s agreed with each other arid, in most cases, with the theory; discrepancies with theory were noted only when T s was less than T s for polystyrene. These data along with electron microscopy also support the prediction that the favored morphology for these systems is a mixture of planar and inverted (middle‐block) cylinders and spheres.