We demonstrate that the co-nonsolvency effect strongly affects the responsive behavior of PMMA-<i>b</i>-PNIPAM in the polymer-rich part of the phase diagram. Thin films equilibrated in water vapor show a swelling and contraction at the exchange of the atmosphere to mixed vapor of water and methanol. The film kinetics are investigated in-situ by spectral reflectance and time-of-flight neutron reflectometry. The water and methanol contents are calculated using scattering contrast variation. Hydration and co-solvent exchange processes at the PNIPAM amide and alkyl functional groups are resolved with Fourier-transform infrared spectroscopy. Results on both mesoscopic and molecular length scales indicate the film response is governed by a methanol absorption phase leading to additional swelling, followed by contraction with little change in the water/methanol ratio.

Co-nonsolvency induced response of thin PMMA-<i>b</i>-PNIPAM films in mixed water/methanol vapor

ACS Spring Meeting 2021

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Co-nonsolvency induced response of thin PMMA-b-PNIPAM films in mixed water/methanol vapor