Thermo-reversible swelling of thin hydrogel films immobilized by low-pressure plasma

Schmaljohann, Dirk, Beyerlein, D, Nitschke, M and Werner, C 2004. Thermo-reversible swelling of thin hydrogel films immobilized by low-pressure plasma. Langmuir 20 (23) , pp. 10107-10114. 10.1021/la034653f

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Abstract

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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Pharmacy
Publisher:	ACS Publications
ISSN:	0743-7463
Last Modified:	19 Mar 2016 22:02
URI:	https://orca.cardiff.ac.uk/id/eprint/945

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