Neutron and X-ray reflection from surface monolayers of a lipopolyoxazoline

A new class of lipopolymers with polyoxazoline headgroups has been synthesi zed for the design of drug carriers, These amphiphatic molecules form stabl e monolayers at the air-water interface. Using X-ray and neutron reflectivi ty, the molecular conformations of the lipopolymer at the liquid surface we re investigated as a function of surface pressure. The data are consistent with a fraction of the polyoxazoline moieties in brush-like conformations c oexisting with a smaller fraction that is closely associated with the inter face. Across the phase transition that is detected in the isotherm, the rel ative proportion between these two fractions is shifted. However, no qualit atively distinct molecular conformations are detected that would hint at a phase transition with respect to the polymer chains. (C) 2000 Elsevier Scie nce B.V. All rights reserved.