Superhydrophilic surfaces from short and medium chain solvo-surfactants

Romain Valentin,Zéphirin Mouloungui

doi:10.1051/ocl.2012.0490

Abstract

Pure monoglycerides (GM-Cs) and glycerol carbonate esters (GCE-Cs) are two families of oleochemical molecules composed of a polar part, glycerol for GM-Cs, glycerol carbonate for GCE-Cs, and a fatty acid lipophilic part.From a chemical point of view, GM-Cs include two free oxygen atoms in the hydroxyl functions and one ester function between the fatty acid and the glycerol parts. GCE-Cs contain two blocked oxygen atoms in the cyclic carbonate backbone and three esters functions: two endocyclic in the five-membered cyclic carbonate function, one exocyclic between the fatty acid and glycerol carbonate parts. At the physico-chemical level, GMCs and GCE-Cs are multifunctional molecules with amphiphilic structures: a common hydrophobic chain to the both families and a polar head, glycerol for GMs and glycerol carbonate for GCE-Cs. Physicochemical properties depend on chain lengths, odd or even carbon numbers on the chain, and glyceryl or cyclocarbonic polar heads.The solvo-surfactant character of GM-Cs and overall GCE-Cs were discussed through the measurements of critical micellar concentration (CMC) or critical aggregation concentration (CAC). These surface active glycerol esters/glycerol carbonate esters were classified following their hydrophilic/hydrophobic character correlated to their chain length (LogP<sub>octanol/water<sub/> = f(atom carbon number)). Differential scanning calorimetry and optical polarized light microscopy allow us to highlight the selfassembling properties of the glycerol carbonate esters alone and in presence of water. We studied by thermal analysis the polymorphic behaviour of GCE-Cs, and the correlation between their melting points versus the chain lengths.Coupling the self-aggregation and crystallization properties, superhydrophilic surfaces were obtained by formulating GM-Cs and GCE-Cs. An efficient durable water-repellent coating of various metallic and polymeric surfaces was allowed. Such surfaces coated by self-assembled fatty acid esters in a stable coagel state present a novel solution for the water-repellent coating of surfaces.

Highlights

Coatings designed to exhibit extreme wetting characteristics such as superhydrophobicity and superhydrophilicity have the potential to open up entirely new routes for manipulating and controlling the interaction of liquids with surfaces (Cebeci et al, 2006)
We develop the synthesis of pure monoglycerides, by direct condensation of fatty acid, like oleic acid described in the figure 2 with glycidol in aqueous medium in the presence of an anionexchange resin as a recyclable catalyst (Mouloungui et al, 2009)
We showed that glycerol carbonate esters are new polymorphic molecules different from monoglycerides

Summary

Introduction

Coatings designed to exhibit extreme wetting characteristics such as superhydrophobicity and superhydrophilicity have the potential to open up entirely new routes for manipulating and controlling the interaction of liquids with surfaces (Cebeci et al, 2006). Carbonic glycerylic fatty acid esters or GCE-Cs present a locked glycerol polar head. The esterification reaction takes place simultaneously at the interface of glycerol carbonate/octanoic acid and in the hydrophobic phase fatty acidglycerol carbonate ester.

Results

Conclusion