Two-Dimensional Physical Networks of Lipopolymers at the Air/Water Interface: Correlation of Molecular Structure and Surface Rheological Behavior

Recent surface rheology and film balance experiments on monolayers of PEG lipopolymers and phospholipid/PEG lipopolymer mixtures at the air−water interface have revealed a new class of quasi two-dimensional physical networks. Two different kinds of associative interactions are necessary to form the network: microcondensation of alkyl chains of lipopolymers to form small clusters and water molecule mediation of the interaction between adjacent PEG clusters via hydrogen bonding. In the experiments presented here, we are interested to learn whether the physical gelation is PEG specific or whether it is a more general characteristic of lipopolymers at the air−water interface. To address this topic, we have expanded our surface rheology and film balance experiments to poly(oxazoline) lipopolymers. Our experiments indicate the occurrence of a rheological transition if the poly(oxazoline) lipopolymers consist of a dioctadecylglycerol anchor. This shows that the physical gelation among lipopolymers is not a PEG-...