Surface pattern in thin poly(styrene-maleic anhydride) films

Monodispersed poly(styrene-maleic anhydride) alternating copolymer (SMA) is synthesized through radical polymerization, and characterized by GPC, DSC, FT-IR and H-1 NMR spectra. The mole fraction, chi, of styrene in the copol ymer is 0.51, determined from integrated H-1 NMR spectrum, this value is co nsistent with the alternating structure. FT-LR spectra show that maleic anh ydride moieties on the backbone chains hydrolyze in a THF solution containi ng water, and HCl can accelerate the hydrolysis process. Atomic force micro scopy reveals that well-arrayed and uniform-sized holes formed in thin SMA films on single crystal silicon wafer substrates spin-cast from the THF sol utions containing HCl. HCl can also influence hydrogen bonding between the carboxylic acid groups in the THF solution, which is crucial for the format ion of holes in the thin films. The volatilization process in the spin-cast ing is divided into two stages, THF and water volatilization. The formation of holes is interpreted as the trace of water droplets emulsified by the h ydrolyzed SMA in the second stage, i.e. water volatilization. Results also indicate that there are both mobile and bound water populations in the solu tion, and that the bound water is responsible for the hole or valley patter n of these thin films. (C) 1999 Elsevier Science Ltd. All rights reserved.