Grazing Incidence Neutron Spin Echo Study of Poly(N-isopropylacrylamide) Brushes

The structure and dynamic properties of poly(N-isopropylacrylamide) brushes at solid planar surfaces under good solvent conditions are studied. Polymer brushes with grafting densities in the concentrated and semidilute regime are prepared via surface-initiated atom transfer radical polymerization. The polymer brushes were removed from the substrates to determine the molar mass and molecular dispersity via size-exclusion chromatography to draw conclusions about the grafting density. The structure of the brushes was investigated with ellipsometry and neutron reflectometry measurements. We found an influence of the grafting density on the swelling properties of the poly(N-isopropylacrylamide) brushes. Furthermore, the brush dynamics at different neutron penetration depths was analyzed with neutron spin echo spectroscopy under grazing incidence. The evanescent intensity distribution was modeled with the BornAgain software package, which uses the distorted-wave Born approximation.