Tailored conditions for controlled and fast growth of surface-grafted PNIPAM brushes

Abstract

Abstract Surface-initiated Atom Transfer Radical Polymerization is an established technique for synthesis of polymer brushes via “grafting from” method. However, dynamic behavior of surface-tethered macromolecules during their growth requires more detailed studies to obtain uniform polymer brush films. It was addressed here by varying solvent composition in grafting of poly(N-isopropylacrylamide) brushes. Complementary in situ (quartz crystal microbalance) and ex situ (atomic force microscope, spectroscopic ellipsometry) techniques were employed to investigate the influence of methanol molar fraction (xMe) in methanol/water polymerization mixture on the brush growth. Grazing-angle polarized FT-IR spectroscopy was used to monitor macromolecular arrangement in the brushes. While achieving controlled, uniform and relatively fast growth of macromolecules is challenging a compromise may be reached by tuning solvent composition. The most balanced conditions with this respect were found in a narrow solvent composition window at ca. xMe ≈ 0.16 and below 0.31. The results may be applied for tailoring polymerization conditions of other polymer brush systems.