Effect of Microdomain Structure and Process Conditions on the Mechanical Behavior of Cylindrical Block Copolymer Systems

We investigate the effect that process conditions have on the structural characteristics and mechanical response of a cylindrically phase-separated poly(styrene−ethylene-co-butylene−styrene) (SEBS) triblock copolymer system. Small-angle X-ray diffraction (SAXD) and transmission electron microscopy (TEM) have been used to study the microdomain and grain structure, respectively. It is observed that the structural changes that occur with different process conditions and thermal treatment alter the mechanical behavior in both monotonic tensile and cyclic tests. Results show that the d-spacing decreases with increasing temperature and increasing cooling rate from the melt state. These subtle changes in d-spacing are correlated with the elastic modulus. Such variations in domain spacing and size depend on the segregation power (χ) of the system. Grain size changes significantly with cooling rate and upon annealing fine-grain structures but has no significant effect on the material's modulus.