Effects of drying temperature in solution coating process on the structural changes upon uniaxial stretching of sphere-forming block copolymer films

The correlation between mechanical properties and the structural changes of a block copolymer having spherical microdomains in uniaxial stretching was examined by atomic force microscopy observations and two-dimensional small-angle X-ray scattering measurements. For this purpose, coated layers composed of di- and tri-block copolymer blends were prepared by solution coating at different drying temperatures. It was revealed that the bcc lattice underwent affine deformation up to a certain stretching ratio (lambda), irrespective of the drying temperature, and that the upper limit of lambda for the affine deformation is approximately the same as the stretching ratio at which the stress-strain curve rises dramatically. It was also found that the packing regularity of spheres in the uniaxial stretching direction is enhanced with stretching after a plateau region where the regularity does not change. The behavior of the packing regularity as a function of the stretching ratio strongly depends on the drying temperature. We could correlate the fracture of the block copolymer film having spherical microdomains with the completion of the stretching-induced ordering of spheres in the stretching direction.