Effects of conditions in hot-melt coating process on microphase-separated structures and macroscopic deformation in coated layers composed of di- and triblock copolymer blends

Abstract

Effects of the coating rate, the cooling temperature and the discharge rate in the hot-melt coating process on the microphase-separated structure and the macroscopic deformation have been revealed using blend specimens of MA/MAM where MA and MAM are a poly(methylmethacrylate)-block-poly(n-butylacrylate) diblock copolymer and a poly(methylmethacrylate)-block-poly(n-butylacrylate)-block-poly(methylmethacrylate) triblock copolymer, respectively. It was found that the hot-melt coated specimen had the anisotropic distribution of the spheres where the d spacing of the nanostructure in the machine direction (MD) is longer than that in the transverse direction (TD) and had a lower ordering regularity of the spherical microdomains in the MD due to shear and elongational deformation. The change of the macroscopic size upon the release of the coated layer from the substrate also confirmed the elongation of the soft-segment (poly (n-butylacrylate)) chains in the MD during the hot-melt coating by exhibiting the macroscopic shrinkage in the MD upon the release. However, the extent of the microscopic elongation (d spacing) was lower than the macroscopic elongation in the MD. This implies that the soft-segment chains are relaxed due to pulling-out of the poly (methylmethacrylate) chains from the hard spherical microdomains. As for the effects of the coating rate, the extent of the chain stretching of the soft segment was increased with the coating rate when the discharge rate (the flux of materials provided onto the substrate through the die lip) was kept constant. However, no effects were confirmed when the discharge rate was so controlled to maintain the thickness of the as-coated layer constant. Thus, the effects of the coating rate and the discharge rate were compensated, and the effects on the chain stretching of the soft segment can be recognized simply in terms of the thickness of the as-coated layer. As for the effects of the cooling-roll temperature, it was found that the extent of the chain stretching of the soft segment was decreased with an increase in the cooling-roll temperature.