Mixed Fluorocarbon/Hydrocarbon Molecular Dowels Help Protect Concentrated Fluorocarbon Emulsions with Large Size Droplets Against Coalescence

Abstract

Mixed fluorocarbon/hydrocarbon amphiphiles, the so-called molecular dowels, have previously been reported to strongly stabilize concentrated (90% w/v, i.e. 47% w/v) submicronic size perfluorooctyl bromide emulsions emulsified by egg yolk phospholipids. The dowel molecules, used in equimolar amounts with phospholipids, enable the preparation of emulsions with large-sized particles which are impossible to obtain with phopholipids alone. We report here that molecular dowels (C₆F₁₃C₁₀H21, F6H10) also hinder droplet coalescence induced by mechanical stress in sterilized emulsions with average particle sizes ranging from ca 1 to 16 μm. In contrast, the addition of equimolar amounts of perfluorodecyl bromide was found to have little influence on these emulsions' resistance to mechanical stress. This is consistent with the view that mixed fluorocarbon/hydrocarbon dowels are held in the interfacial film and reinforce its cohesion with the fluorocarbon phase.