Surface freezing, i.e. the formation of a solid bilayer at the surface of a pure alcohol melt above the freezing temperature, was recently discovered. We demonstrate here that the structure of the bilayer can be influenced by specific bulk additives. Two different additives, able to form hydrogen bonds (water) and both hydrogen bonds and van der Waals interactions (α,ω-diols), are used. The surface layer's structure is studied by surface-specific X-ray methods. We find that water swells the bilayer by intercalation into its center at a molecular water:alcohol ratio of approx. 1:2. For the diolated alcohols a reversible monolayer-bilayer surface phase transition is observed, the first of its kind for surface-frozen layers. A continuous decrease of the molecular tilt with increasing diol concentration is also found for the tilted bilayer phases.
|Number of pages||7|
|Journal||Colloids and Surfaces A: Physicochemical and Engineering Aspects|
|State||Published - 30 Apr 2000|
|Event||The 15th European Chemistry at Interfaces Conference - Jerusalem, Isr|
Duration: 18 Oct 1998 → 22 Oct 1998
Bibliographical noteFunding Information:
The financial support of the work at Bar-Ilan University by Exxon Research and Engineering Co. is gratefully acknowledged, as is the beamtime allocation at beamline X22B, NSLS, BNL. Brookhaven National Laboratory is supported by the division of Materials Research, DOE, under contract DEAC02-98CH10886.
- Bulk additives
- Monolayer-bilayer surface phase transition
- Pure alcohol melts
- Surface freezing