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Authors
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Schmaljohann, D. ; Beyerlein, D. ; Nitschke, M. ; Werner, G.
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Title
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Thermo-Reversible Swelling of Thin Hydrogel Films Immobilized by Low-Pressure Plasma
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Date
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08.11.2004
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Number
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11394
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Abstract
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Thin films of graft copolymers consisting of poly(N-isopropylacrylamide) (PNiPAAm) or poly(N,N-diethylacrylamide) (PDEAAm) as polymer backbone and poly(ethyleneglycol) as side chains were cross-linked on fluoropolymer substrates by low-pressure plasma treatment. All immobilized polymers exhibit a lower critical solution temperature between 34 and 40 C. The swelling and collapsing of the hydrogels was examined with temperature-dependent spectroscopic ellipsometry. Two time ranges of swelling were observed: a fast 'dynamic' and a slow 'equilibrium' swelling. The dynamic swelling occurs within minutes or less, whereas the equilibrium swelling needs several days to complete. The surface-bound hydrogels show a shift in the transition temperature toward lower temperatures compared with the behavior in solution. Full reversibility of the dynamic swelling/collapsing was found, but the temperature scan exhibits a hysteresis between heating and cooling cycles. The PNiPAAm-containing hydrogels show a sharper transition compared to the PDEAAm-containing hydrogels, which is almost linear over a wide temperature range.
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Publisher
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Langmuir
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Wikidata
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Citation
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Langmuir 20 (2004) 10107-10114
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DOI
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https://doi.org/10.1021/la034653f
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Tags
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MBC_Plasma
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