Abstract
In this study phase transitions and thermodynamic properties of monolayers of short poly(ethylene glycol) chains (abbreviated as EG) covalently attached to lipids were determined by analyzing pressure−area isotherms at three different temperatures by using a film balance. The EG chain lengths were varied systematically between N = 3 and N = 15 repeating EG units. For the two longest EG chains (N = 12 and N = 15) a new synthesis is described. For short chains (N < 9) the monolayer phase transition is determined by the alkyl chain moiety of the headgroup, while for N ≥ 9 the typical behavior of lipopolymers is observed. For the fluid−gel phase transition the entropy and the corresponding latent heat were determined for 3, 6, and 9 EG lipids. In the second part the lipids were transferred to hydrophilic silicon oxide substrates by the Langmuir−Blodgett technique and characterized by their equilibrium swelling behavior under controlled humidity by using ellipsometry. In agreement with the monolayer experiment...
Published Version
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