0000000000555733
AUTHOR
Michael Schwendler
Properties of Hydrophobic Polymer Melts Tethered to the Water Surface As Determined with in Situ X-ray Reflectivity
Insoluble monolayers of hydrophobic polymers with low glass transition temperature (perfluoropolyethers, polyisoprenes) and a single ionic head group (carboxylic acid, sulfonate) have been characterized at the air/water interface via X-ray reflectivity measurements. The films are considerably thicker (30−420 A) than conventional Langmuir monolayers of low molecular weight substances or polymers with surface active repeat units. The thickness is inversely proportional to the area per head group and is in accordance with a model assuming a solvent-free hydrophobic layer of the same density as the bulk material.
Tail and Head Group Interactions in Phospholipid Monolayers
Abstract The order/disorder transition of the phospholipid 1,2-dihexadecyl-sn-glycero-3-phosphocholine and its derivatives was studied by X-ray reflection and thermodynamic measurements. We find that increasing the length of an ethylene oxide spacer (zero to three EO groups) between the phosphate group and the hydrophobic chains (i) induces a slight shift of the main transition, (ii) reduces the influence of the head groups on the chain lattice, and (iii) increases the head group length and promotes its hydration. For DH(EO)3PC in the ordered phase we find that the small phosphate groups (which are the main source of contrast in X-ray reflectivity) are homogeneously distributed within the h…