Orientation and relaxation behaviors of lamellar microdomains of poly(methyl methacrylate)-b-poly(n-butyl acrylate) thin films as revealed by grazing-incidence small-angle X-ray scattering

Abstract

The orientation behavior and domain spacing relaxation of the phase-separated structure of poly(methyl methacrylate-b-n-butyl acrylate) (PMMA-PnBA) thin films were investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Moreover, low-energy GISAXS (tender X-ray) was performed for the in-depth profiling of the microphase-separated structure. PMMA-PnBA forms a lamellar structure. Parallel orientation of the lamellae was induced by thermal annealing. XPS measurements indicated that surface segregation of the PnBA component occurred rapidly, within 1 min after annealing at 160 °C. GISAXS measurements revealed that the apparent degree of orientation and the domain spacing D|| of the parallel-oriented lamellae increased with annealing time, and the final D|| was close to the domain spacing of the bulk material. The domain spacing relaxation took longer than the orientation of the lamellae of the block copolymers. Furthermore, it was found that D|| in the vicinity of the surface was greater than inside the film, which indicates that the domain spacing near the surface relaxed faster than inside due to the higher mobility of the polymer chain. The orientation behavior and domain spacing relaxation of the phase-separated structure of poly(methyl methacrylate-b-n-butyl acrylate) thin films were investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Moreover, low-energy GISAXS was performed for the in-depth profiling of the lamellar structure. The domain spacing (D||) relaxation took longer than the orientation of the lamellae. Furthermore, the D|| in the vicinity of the surface was greater than inside the film, which indicates that the D|| near the surface relaxed faster than inside due to the higher mobility of the polymer chain.