Topography of collapsed triglyceride monolayers on glass

The stability and conformation of tripalmitin (TP) and triolein (TO) Langmu ir-Blodgett (LB) monolayers on glass were investigated using Atomic Force M icroscopy (AFM). Compression isotherms revealed that TP reached the solid s tate at 15 mN m(-1), with a trident conformation. LB deposition of the mono layer on the glass surface was performed at the solid state (30 mN m(-1)) w ith a transfer ratio close to 1. The TO monolayer collapsed in the liquid-e xpanded phase at 13 mN m(-1). LB deposition was performed at 11 mN m(-1) wi th a transfer ratio of 1.4. The LB films were imaged by AFM (tapping mode). The TO monolayer collapsed in amorphous droplets. TP presented tiny amorph ous drops plus crystalline shapes with unit layers of a thickness of 40-46 Angstrom, corresponding to the long spacing of the beta and alpha polymorph ic forms. TP monolayer thus collapsed in aggregates to form crystalline str uctures. The thickness of the first step was mostly 86 Angstrom, but someti mes 68 Angstrom steps were observed, while the transferred monolayer genera lly reorganizes as a tuning fork in a regular crystalline unit, but can als o remain as a trident, providing a hydrophobic support for upper layers. Th is findings supply backing for technical processes such as the interpretati on of fat fractionation by microfiltration membranes, based on triglyceride /solid interaction statements.