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Description
Classic zwitterionic poly(sulfobetaine)s, poly(4-((3-methacrylamidopropyl)dimethyllammonio)butane-1-sulfonate)) (PSBP)， which exhibit an upper critical solution temperature (UCST) in aqueous media，have been widely used to investigate its swelling/deswelling behavior and phase transition mechanism. Also its block copolymers reached high attention if they contain other broadly studied nonionic thermo-responsive polymers，especially poly(N-isopropylacrylamide) (PNIPAM) and poly(isopropylmethacrylamide)(PNIPMAM), which feature a lower critical solution temperature (LCST) in aqueous solution, normally higher than UCST of PSBP. However, a comparison between the block copolymer films of PSBP-b-PNIPAM and PSBP-b-PNIPMAM, with a similar degree of polymerization and thickness of film, is still missing. We present a comparison of the humidity- induced swelling/deswelling behavior of block copolymer thin films of PSBP-b-PNIPAM and PSBP-b-PNIPMAM with a similar degree of polymerization and thickness in aqueous vapor atmosphere as studied by time-of-flight neutron reflectometry (TOF-NR). Ellipsometer results, when adjusting the spin coating parameters, contributed to control the thickness to 50-60 nm. The resulting polymer films were also characterized by Fourier transform infrared (FTIR) spectroscopy.
