期刊
MACROMOLECULES
卷 53, 期 8, 页码 2841-2855出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.macromol.0c00046
关键词
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资金
- Deutsche Forschungsgemeinschaft (DFG) [PA 771/14-1, MU 1487/17-1, LA 611/11-1]
- BMBF project Flexiprobe [05K16WOA]
The swelling and phase transition behavior upon increasing temperature of a doubly thermoresponsive diblock copolymer thin film in steps above the characteristic cloud points (CPs) of the blocks is studied. An upper critical solution temperature (UCST)-type zwitterionic poly(sulfobetaine), poly(N,N-dimethyl-N-(3-methacrylamidopropyl)-ammoniopropane sulfonate) (PSPP, CPUCST = 31.5 degrees C), is combined with a lower critical solution temperature (LCST)-type nonionic poly(N-isopropyl-/methacrylamide) (PNIPMAM, CPLCST = 49.5 degrees C) block. Using time-of-flight neutron reflectivity (ToF-NR), we observe the swelling in D2O vapor at a constant temperature of 20 degrees C, followed by two subsequent temperature jumps, from 20 to 40 degrees C (above CPUCST) and from 40 to 60 degrees C (above CPLCST). The observed response of the diblock copolymer films deviates from the aqueous solution behavior, which is mainly attributed to the increased polymer concentration. Temperature-induced changes in the thin-film nanostructure are investigated with ToF grazing-incidence small-angle neutron scattering (GISANS). Alterations in the chain conformation and hydrogen bonding are probed by Fourier transform infrared (FTIR) spectroscopy. The ionic SO3- groups (in the PSPP block) and the nonionic hydrophilic amide groups (in both blocks) are found to affect the mechanisms of D2O uptake and release significantly.
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