Superhydrophilic surfaces from short and medium chain ... · Cs and GCE-Cs are multifunctional molecules with amphiphilic structures: a common hydrophobic chain to the both families

Superhydrophilic surfaces from short and medium chainsolvo-surfactants

Introduction

Coatings designed to exhibit extremewetting characteristics such as super-hydrophobicity and superhydrophilicityhave the potential to open up entirelynew routes for manipulating and con-trolling the interaction of liquids withsurfaces (Cebeci et al., 2006). Self-cleaning, antifogging, and bacteria-resistant surfaces are but a few examples

of some of the applications that couldbe enabled by the creation of surfacesthat either completely resist wetting bywater (superhydrophobic state) or thatare completely and instantaneously wetby water (high hydrophilic and super-hydrophilic states). Superhydrophilicityand superwetting surfaces refer totextured and/or structured materials(rough and/or porous) on which water(liquid) spreads completely (Drelich and

Chibowski, 2010). To obtain suchsurfaces, two basic approaches havebeen reported (Cebeci et al., 2006). Thefirst involves the use of photochemicallyactive materials such as TiO2 thatbecome superhydrophilic after expo-sure to UV, or with suitable chemicalmodifications, visible radiation. Surfacecoatings based on TiO2 typically losetheir superhydrophilic qualities withinminutes to hours when placed in a dark

Abstract: Pure monoglycerides (GM-Cs) and glycerol carbonate esters (GCE-Cs) aretwo 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 hydroxylfunctions and one ester function between the fatty acid and the glycerol parts. GCE-Cscontain two blocked oxygen atoms in the cyclic carbonate backbone and three estersfunctions: two endocyclic in the five-membered cyclic carbonate function, one exocyclicbetween the fatty acid and glycerol carbonate parts. At the physico-chemical level, GM-Cs and GCE-Cs are multifunctional molecules with amphiphilic structures: a commonhydrophobic chain to the both families and a polar head, glycerol for GMs and glycerolcarbonate for GCE-Cs. Physicochemical properties depend on chain lengths, odd or evencarbon numbers on the chain, and glyceryl or cyclocarbonic polar heads.The solvo-surfactant character of GM-Cs and overall GCE-Cs were discussed through themeasurements of critical micellar concentration (CMC) or critical aggregationconcentration (CAC). These surface active glycerol esters/glycerol carbonate esterswere classified following their hydrophilic/hydrophobic character correlated to theirchain length (LogPoctanol/water = f(atom carbon number)). Differential scanningcalorimetry and optical polarized light microscopy allow us to highlight the self-assembling properties of the glycerol carbonate esters alone and in presence of water. Westudied by thermal analysis the polymorphic behaviour of GCE-Cs, and the correlationbetween their melting points versus the chain lengths.Coupling the self-aggregation and crystallization properties, superhydrophilic surfaceswere obtained by formulating GM-Cs and GCE-Cs. An efficient durable water-repellentcoating of various metallic and polymeric surfaces was allowed. Such surfaces coated byself-assembled fatty acid esters in a stable coagel state present a novel solution for thewater-repellent coating of surfaces.

Key words: pure monoglycerides, pure glycerol carbonate esters, formulation, solvo-surfactant, critical aggregation concentration, self-assembling, superhydrophilicity, p-olymorphism

Romain VALENTINZ�ephirin MOULOUNGUI

Universit�e de Toulouse,

INP-ENSIACET,

LCA (Laboratoire de Chimie Agro-

industrielle),

INRA,

UMR 1010 CAI,

F-31030 Toulouse,

France

<[email protected]>

Article received 8 November 2012

Accepted 15 November 2012

To cite this article: Valentin R, Mouloungui Z. Superhydrophilic surfaces from short and medium chain solvo-surfactants. OCL 2013; 20(1):33-44. doi : 10.1684/ocl.2012.0490

doi:10.1684/ocl.2012.0490

OCL VOL. 20 N8 1 janvier-fevrier 2013 33

DOSSIER : CHIMIE DU V�EG�ETAL ET LIPOCHIMIE

Article disponible sur le site http://www.ocl-journal.org ou http://dx.doi.org/10.1051/ocl.2012.0490

http://www.ocl-journal.org

http://dx.doi.org/10.1051/ocl.2012.0490

environment, although much progresshas been made toward eliminating thispotential limitation. The second caseinvolves the use of textured surfaces topromote superwetting behavior. Innature, superhydrophilicity has beendeveloped by different organs of plantsand is caused by different micro- andnanostructures (Koch and Barthlott,2009). Superhydrophilic plant surfacescan be divided into those that arepermanently wet, absorb water overtheir surfaces and let water spread overthe surface. In the last case, waterdroplets spread rapidly on the peri-stome and form thin films, whichmake the peristome extremely slipperyfor insects (Bauer et al., 2008). Fastwater spreading was observed on theleaves plants where glands secretehydrophilic substances like saponinsthat, in combination with the surfaceroughness, lead to the superhydrophi-licity. Water spreading is favored whensurface roughness presents an arrange-ment where capillarity phenomenaoccur (Koch and Barthlott, 2009). Thesuperhydrophilicity provides a fasterevaporation of the water by an increaseof the water–air interface. Thus, waterevaporates from a superhydrophilicsurface much faster than that from ahydrophilic or superhydrophobic one,where water forms semi-spherical orspherical droplets. Here we showed

how surface-active molecules such asfatty acid esters respond adequately tothe question of water-retaining by poly-morphic liquid crystalline phases com-bining order and mobility at a molecularand supramolecular level. Therefore,glycerol fatty acid esters ‘‘monoglycer-ides’’ and ‘‘glycerol carbonate fatty acidesters’’ are of great importance. They aresolvo-surfactants and show self-assemblyphenomena if their concentration ishigher than a certain critical aggregationconcentration (CAC). There are someexamples of self-assembly structuresformed by polar lipids including glycerolfatty acid esters (Leser et al., 2006).Carbonic glycerylic fatty acid esters orGCE-Cs present a locked glycerol polarhead. Pure GM-Cs are associated withvariable lengths of hydrophobic chains(7–18 atoms of carbon), giving them anamphiphilic character and polymorphicproperties. Evaluation of their physico-chemical properties such as solvo-surfac-tivity and their ability to give to surfaces atexturedmorphology give them a super-hydrophilic character.

Lipochemical networks ofsynthesis of c-3 agrosynthonsfrom glycerol

The transformation pathways of naturalglycerin for the directed synthesis ofagro-C3 highly reactive synthons are

illustrated in figure 1 (Mouloungui,2004; Vriet and Mouloungui, 2008).The both major synthons, listed astop value added chemicals by the USDepartment of Energy (Werpy andPetersen, 2004) are glycerol carbonateand glycidol. The study of theirreactivity opens the door to the synthesisand development of non-ionic interfacialagents that are esters ofglycerol and fattyacids, puremonoglycerides, andestersofglycerol carbonate and fatty acids. Thedevelopment of this C-3 glycerol basedchemistry by the Mouloungui’s groupsince 1994 (Mouloungui, 2004) was inrespect of twelve principles of the greenchemistry (Anastas and Warner, 1998),with atom economy, synthesis withoutsolvent, and CO2 sequestration byorganic carbonate production. Thesestudies are referenced and describedin a recent review (Corma et al., 2007).

Catalytic synthesis of glycerolcarbonate by transcarbonatationof glycerol or carbonylation ofglycerol

Glycerol carbonate is the first step in thechain generation of glyceryl synthons.Reactive glycerol carbonate is obtainedby the heterocyclization of two vicinalhydroxyl groups of glycerol in cyclo-carbonates by reacting glycerol withsources of organic or inorganic carbon-

C3 building block

Short chains

Purity >98%

α-Monoglyceride purity >85%

α-Monoglycerides purity >67%

Medium chains

GlycerolCarbonate esters

Esterification

OH

OH

OH

OHOH

OHOH

OO

OO

O

O

OO

O

OC

OC

O

Condensation

Glycidol

Transesterification

Esterification

Glycerol

Glycerolcarbonate

Figure 1. Transformation pathways of natural glycerin for the directed synthesis of agro-C3 highly reactive synthons.

34 OCL VOL. 20 N8 1 janvier-fevrier 2013

ate. Depending on the nature ofcarbonate donor, there are two meth-ods of heterocyclization of glycerol:catalytic transcarbonation of glycerolby organic carbonates (Moulounguiet al., 1996; Vieville et al., 1998) andcatalytic carbonylation of glycerol byurea (Claude et al., 2001, Moulounguiand Yoo, 2007)). Carbonation of glyc-erol by urea catalyzed by zinc sulfateis part of a systematic approach toimproving the competitiveness of themethod of synthesis of glycerol carbon-ate. Urea is a co-reactive, mineralcarbonate donor and inexpensive. It isthe masked form of CO2. Thus, the‘‘urea method’’ contributes to thealiphatic sequestration of carbon diox-ide in glycerol carbonate. The study andunderstanding of the mechanism of thereaction of urea with glycerol haveimproved the yield of the reaction andefficiency of the process. The catalyticprocess is based on the use of zincsulfate and knowledge of the nature,number and strength of the reusableLewis catalytic sites. The use of metalsulfatesprovidesheterogeneous catalyticsystems. Catalytic carbonylation of glyc-erol occurs in two consecutive steps: insitu carbamoylation and carbonylationofglycerol (Yoo and Mouloungui, 2003).The kinetics of formation of the glycerolcarbonate and gaseous ammonia arecomparable. Nucleation of zinc sulfateand the production of gaseous ammoniaresult in a change of the composition ofthe reaction system. The production ofglycerol carbonate is increased by shift-ing the equilibrium of the reactionmodulating the pressure at constanttemperature.

Catalytic synthesis of glycidol byoligomerization of glycerolcarbonate

Produced industrially by laborious pro-cesses of synthesis and purification fromallyl alcohol of petrochemical origin,glycidol is now the second generationsynthon in our integrated scheme.Work on the oligomerization of glycerolcarbonate followed by the depolymeri-zation thanks to the catalytic action andconfinement effect of zeolites haveopen the way for the development ofa new method for the synthesis ofglycidol. The one-pot synthesis of gly-cidol (Yoo and Mouloungui, 2001) iscarried out in liquid multiphase hetero-geneous catalysis (glycerol carbonate/

glycerol 85/15w/w)/solid (zeolite A)/gas(CO2-glycidol) according the followingfive steps: i) diffusion of glycerol carbon-ate and glycerol to the catalytic sites ofthe zeolite A, ii) adsorption of moleculesat the surface of the zeolite A, iii) surfacereactionbetweenglycerol carbonate andglycerol iv) desorption and diffusion ofglycidol andgaseous carbondioxidegas,and v) recycling of glycerol and sites ofthe zeolite A. A degree of glycidol 99%was isolated after flash purification (Yooand Mouloungui, 1998).

The both methods manufacture unit ofglycerol carbonate and glycidol fromglycerol are economical, clean andproductive. They contribute significantlyto control the price of the biodieselglycerin and lower prices of these twobuilding blocks. The availability of glyc-erol carbonate and glycidol allow thestudy of their reactivity and transforma-tion into more elaborate molecules likemonoglycerides and glycerol carbonateesters.

Catalytic synthesis of puremonoglyceride by condensationof glycidol with fatty acids

In view of their polyfunctional natureand their emulsifying, complexing, andlubricating properties, fatty acid mono-glycerides find application in the food(Hartunian-Sowa et al., 1990; Fujimuraet al., 1991), cosmetics, pharmaceutical(Rieger, 1990; Kabara and Lie, 1977;Kato, 1981) and textile and fiber indus-tries (Kamei, 1990; Mc Intire, 1989).In certain applications, their efficacyhinges on the incorporation of puremonoglycerides (>90%) as additives(Mouloungui and Gauvrit, 1998). Allof the conventional methods for thepreparation of monoglycerides, eitherby direct esterification of glycerol byfatty acids or by hydrolysis or transes-terification of oils, lead to mixture ofglycerides. Pure monoglycerides aregenerally obtained by molecular distil-lation, which raises their cost. Analternative chemical method is to pre-pare the monoglycerides from glycidol.In general, this reaction is conductedin the presence of a basic catalyst in ahomogeneous medium: amines and/orquaternary ammonium salts (Lok,1980), metal alcoholates (Burgoset al., 1987; Caron and Sharpless,1985), or bases (Tamura, 1992).Although the yields of the glycerolmonoesters are relatively satisfactory,

the operating conditions in the homo-geneous phase require phase-transferagents and solvents that are able towithstand high temperatures. In hetero-geneous catalysis, amines supportedon mesoporous materials present goodresults, especially with hydrophobicsurfaces (Cauvel et al., 1997). Wedevelop the synthesis of pure mono-glycerides, by direct condensation offatty acid, like oleic acid described in thefigure 2 with glycidol in aqueous medi-um in the presence of an anion-exchange resin as a recyclable catalyst(Mouloungui et al., 2009). The newobjective in organic chemistry is thedevelopment of reactions using water asthe solvent instead of organic liquids. Ofcourse, glycidol is a solvent of oleic acid,and glycidol andwater are alsomiscible.Glycerol monooleate (GM-C18:1) andwater produce emulsions. The conden-sation of oleic acid with glycidol to formGM-C18:1 is heterogeneously catalyzedby anion-exchange resins. The follow-ing processes are involved in the overallreaction: (a) diffusion of reagents to thecatalytic sites of resins, (b) adsorptionof reagents in the catalytic sites of theresin, (c) reaction at the surface be-tween adsorbed reagents, (d) diffusionof the reaction products from the poresto the external layer of the resin, and (e)desorption of the reaction productsinto the liquid phase. The reactionon the surface (process c) is assumedto be the sole stage determiningthe kinetics. Hydrophobic-hydrophilicinteractions of the molecules of theorganic reactants were involved in thepseudoternary aquiorganic system. Twotypes of adsorption phenomenon canexplain the interactions between glyc-erol monooleate and resin on one handand oleic acid and resin on the otherhand: physisorption of glycerol mono-oleate in the outer layer of resin andchemisorption of oleic acid. The markedswelling of the anionic resin with oleicacid indicates that the fatty acid pene-trated the resin and that oleic acidwas in contact with the active sites,where it was adsorbed and activated.We also noted a marked elimination ofwater during the phase of preadsorptionof oleic acid onto the Ambersep 900-X(X = OH-, Cl-, HCO3

-) anion-exchangeresins. Oleic acid thus appears to effec-tively desiccate the polymeric lattice,thereby enhancing the organohydro-phobic nature of the solid polymericcatalyst. Then, adsorption of the fatty


acid is governed by van der Waals-typeforces between the fatty hydrophobichydrocarbon chains of the acid and thecross-linked polystyrene matrix, givingrise to a strong adsorbing capacity. Thelong-term stability of the resins is thusincreased, with an enhanced catalyticsystem. By preadsorbing oleic acid ontothe resin, the stage of transport anddiffusion (stage a) of the fatty acid isno longer a limiting step in the overallreaction. The ensuing condensationbetween oleic acid and glycidol is asurface reaction. It takes place betweenreactantswithin thedroplets dispersed inthe continuous organic hydrophobicpseudophase within and on the surfaceof the macroporous particles and gels.The kinetics appeared to obey thosedescribed by the Langmuir-Rideal modelfor the surface reaction. The conditionswere optimized for a discontinuousprocess in a stirred reactor. The highestyield of GM-C18:1 (97%) was obtainedwith the non-functionalized formAmbersep 900-Cl- at 708C.

Catalytic synthesis of puremonoglycerides by esterificationof glycerol with fatty acids

An improved method for the produc-tion of monoglycerides by direct esteri-fication of fatty acids with glycerol wasdeveloped (Eychenne and Mouloungui,1999). The reaction medium was com-posed of oleic acid (72% purity),glycerol, dodecylbenzene sulfonic acid(DBSA) as catalyst and emulsifyingagent, as well as of a molecular sieveas drying agent. Partial esterification ofglycerol by oleic acid is carried out ineither a batch reactor and in a columnfilled with a molecular sieve accordingto a continuous process. In a discontin-uous batch reactor, system gives 28% ofglycerol monooleate and strong pro-portions of di- and triesters. The addi-tion of the 3A molecular sieve to thissystem makes it possible to increase theselectivity in glycerol monooleate(47%). However, the reaction carriedout in a column filled with a 3A

molecular sieve produced a mixturecontaining 60% of glycerol monooleateafter deacidification and removal of thecatalyst and shows the advantage of acontinuous process.

Synthesis of glycerol carbonatefatty acid esters by acyl transfertreaction of fatty acids or fattyesters with glycerol carbonate

Esters of glycerol carbonate have beenrelatively little reported. The long-chaincarbonate esters are obtained by reac-tion of glycerol carbonate with acidchlorides (Oehlenschl€ager and Gercken,1979; Mouloungui and Pelet, 2001).Other synthesis routes have been de-scribed: acylation of glycerol carbonateby acetic anhydrid (Gahe andLachowicz, 1989), esterification bycarboxylic acids (Lachowicz and Gahe,1991), transesterification by methylesters (O’Brien and Beavers, 1961). Weemphasize that glycerol carbonate formwith acids and fatty esters immiscible

OH-

CH3

P. resin

CH3

CH3H3C

N-

CI- CI-

CH3

P. resin

CH3

CH3H3C

N-

CH3

P. resin

CH3

CH3H3C

N-OH-

CH3

P. resinPolymeric resin (P. resin)

Polymeric resin (P. resin)

Bulk

Bulk

Resinhydrophobation

Diffusion of reagents, Adsorption, Surface reactions,diffusion of reaction products, desorption of thereaction products

Oleic acidRCOOH

Oleic acid

Oleicacid

OA RCOOH

OA

Nearsurfaceof theresin


CH3

CH3H3C

N-

Emulsion/microemulsion catalytic system

Glycidol+

H2O

Glycidol+

H2O+

Oleic acid

CI-

CH3

P. resin

CH3

CH3H3C

N-CI-

CH3

P. resin

CH3

CH3H3C

N-


Oleic acid

O/W µeW/O

Oleic acid


GM-C18:1 Synthesis

1-GMO

GM-C18:1

GM

-C18:1G

M-C

18:1

1-GMO 1-GMO

CI- CI-

CH3

P. resin

Glycidol+

H2O

Glycidol+

H2O

CH3

CH3H3C

N-

CH3

P. resin

CH3

CH3H3C

N-


Oleic acid

O/W µeW/O


Figure 2. Physicochemical evolution of the condensation reaction of glycidol with oleic acid in the presence of Ambersep 900-Cl- resin, (w/o,water/oil; o/w, oil/water; me, microemulsion). Resin before reaction (hydrophilic resin). Adsorption of oleic acid on resin (hydrophobic resin).Contact of glycidol/water solution with resin (hydrophilic/hydrophobic resin). Resin surrounded by polymorphic system (w/o system, o/w system,or microemulsion system) (Mouloungui et al., 2009).


binary systems (Silvestre et al., 2010).Different parameters were studied: i) thesolubility of these reagents by thedetermination of solubility parametersand the radius of the Hansen solubilitysphere of glycerol carbonate, fatty acidsandmethyl oleate oleic sunflower, ii) thecompatibilizing power of the glycerolcarbonate ester (final product) on the co-reactive evaluated by the study of theevolution of the interfacial tension ofsystems like glycerol carbonate/fattyacid/glycerol carbonate ester or glycerolcarbonate/fatty ester/glycerol carbonateester, depending of the studied reac-tions: esterification and alcoholysis(Mouloungui and Pelet, 2001). Theresults explained that glycerol carbonateis immisciblewith, reactants such as fattyacids and fatty esters, and the productedglycerol carbonate ester. The glycerolcarbonate is a mono-alcohol with highpolar properties. It is a donor-acceptor ofhydrogenbonds. Toallow the reaction totake place, it is important to involveamphiphilic catalysts, penetrating thepseudo-ternary mixtures of glycerol car-bonate/fatty acid-glycerol carbonate es-ter or glycerol carbonate/fatty esters-glycerol carbonate ester. The para-tolu-ene sulfonic acid was found to be anamphiphilic catalytic agent with theability to organize the glycerol carbonatemedium in the octanoic acid. This leadto a hydrophilic zone embedded in ahydrophobic medium constituted of theamphiphilic glycerol carbonate octano-ate. The esterification reaction takesplace simultaneously at the interface ofglycerol carbonate/octanoic acid andin the hydrophobic phase fatty acid-glycerol carbonate ester. Using amphi-philic organotin catalysts such as dibu-tyltin oxide, the acylation of glycerolcarbonatebyalcoholysis also involves thesolubilizationof glycerol carbonate in thehydrophobic phase: glycerol carbonatemethyl ester-glycerol carbonate oleateorganized in reverse micelles. The quan-titative synthesis of glycerol carbonateesters with yields of 60-95% is inter-preted in this way through the establish-ment of non-covalent bonds.

Physico-chemicalproperties

Molecular conformation

Monoglycerides and glycerol carbonateesters are two families of bifunctionnal

biomolecules. The hydrophobic part ofmonoglycerides is a hydrocarbon chainand the hydrophilic component is aglycerol unit. The hydrocarbon chain isprovided by the plant fatty acids. Theyare inserted in position 1 of the glycerol.The glyceryl polar head containingtwo free hydroxyl and the lipophilicfatty acid chain give to monoglyceridesan amphiphilic character. Glycerolcarbonate esters differ because theyare monoglycerides of fatty acid estersin which the hydroxyl functions areblocked. They are oleophilic com-pounds in which the hydrophobicmoiety is a hydrocarbon chain and thehydrophilic part is the glycerol cyclo-carbonate head. Chemically, monogly-cerides consist of an exocyclic esterlinkage between the hydrophobic partand the polar head. Glycerol carbonatefatty acid esters consist of an exoxyclicester linkage between the hydrophobicpart and the polar head containing twoendocyclic ester functions. These bothtype of ester functions can be discrimi-nated by FTIR spectroscopy (figure 3).The endocyclic esters (Oki andNakanishi, 1971), are characterized bya band at 1797 cm-1 whereas theexocyclic ester, give �a vibrational bandat 1743 cm-1. The conformation vari-ability of the polar heads, glycerol orglycerol carbonate, were very interest-ing because this impacts the hydrogenbonding capacity. At interfaces and in

presence of water, physico-chemicalproperties could be affected.

Polymorphism of pure molecules

There is no long-chain compoundwhich is not polymorphic, and thisproperty is particularly pronounced infats and lipids. The crystallization be-havior of fatty molecules (the crystalli-zation rate, crystal size and network,crystal morphology and crystallinity) isdirectly influenced by the polymor-phism; polymorphism depends on themolecular structure itself and on severalexternal factors such as temperature,pressure, solvent, the rate of crystalliza-tion, and impurities. Differential scan-ning calorimetry (DSC) is a technicwhich allows highlighting the differentpolymorphisms. A DSC Mettler ToledoDSC1Stare System apparatus (PerkinElmer, USA) equipped with an Intra-Cooler cooling system was used. Thepurge gas was nitrogen at a rate of 20ml/min. Indium (Tm = 156.68C, DHf =28.45 J/g) and distilled water (Tm = 08C,DHf = 333.79 J/g) were used for calibra-tion. Data were analyzed using Pyrissoftware (Perkin Elmer). Samples of ca.4-10 mg were weighed into aluminumpans to the nearest 0.1 mg, and coverswere hermetically sealed into placedwith O-rings. An empty, hermeticallysealed aluminium pan was used as thereference. To erase the thermal history

2

O

O

OO

O

O

O

OH OH

1.8

cm-1A

bso

rban

ce

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

02000 1950 1900 1850 1800 1750 1700 1650 1600 1550 1500

Figure 3. Transmission FTIR analysis of glycerol monolaurate and glycerol carbonate laurate inDMSO. Concentration in fatty acid ester �0.01mg.mL-1. Bruker Tensor 27 apparatus equippedwith DTGS detector was used.


of the samples, they were heated to808C for 5 min before the analysis ofthermal behavior. Successive cycle ofcooling and heating were appliedwith different cooling and heatingrate: 18C/min, 58C/min, 108C/minand 208C/min.

Monoglyceride polymorphism is wellknown (Malkin, 1954). As show infigure 4, the glycerol monolauratepresent four polymorphs, sub a, a, b’,b. The b form corresponds to the morestable form and was attributed to themelting point of the molecule. At lowcooling and heating rate (18C/min), themore stable form b appears preponder-ant. Increasing the cooling and heatingrate, 18C/min to 208C/min, other lessstable forms are present. They are notedin order of stability sub a, a, b0 and b.Monoglycerides differ from triacylgly-cerol which present generally threepolymorphs. We compared the thermalbehavior of pure monoglycerides(figure 4) to that of pure glycerolcarbonate esters (figure 5). As showfor the glycerol carbonate laurate,glycerol carbonate fatty acid esterspresent four polymorphs, and it isclearly visible in the figure 5 that theheight of the peak corresponding to themore stable form (melting temperature)is very more intense than other transi-tions whatever be the cooling andheating rates. This behavior differs fromthat of monoglycerides. It appears thatglycerol carbonate esters are few sensi-ble to thermal events. This is the result ofthe blocking of the hydroxyl function onthe polar head of glycerol carbonatefatty acid ester. Same experiments wereperformed on GCE-Cs of lower chainlength C8, C9 andC10 andwe noted onfigure 6 the temperature of the thermaltransitions.

All thermograms present very similarshapes with same number of phasetransitions. For each glycerol carbonateester, four temperature transitionswere found. All increased with thechain length. The more intense form 4corresponding to the melting transitionis always preponderant whatever maybe the scanning temperature rates. Themelting temperature increased with thechain length, nor linearly (figure 6).Melting temperature values of GM-Cswere lower than the melting points ofsame chain length monoglycerides.

We studied in more detail thermalbehavior of glycerol carbonate laurate

with Polarized light microscopy. ANikon Eclipse E600 optical microscope(Nikon Corporation, Japan) was usedequipped with polarized filters and aMettler Toledo FP82HT hot stage man-aged by a FP90 central unit. The images(figure 7) were acquired with a highresolution, low noise CCD Nikon DXM-1200 color camera and analyzed usingLUCIA G version 4.8 software. Thecentral processor unit was programmedto heat the sample at a heating rate of58/min until the melting of the sample.Images were acquired with a magnifi-cation of hundred times at each 18C.

Temperature scans of samples werecarried out with polarized light micros-copy aiming at identifying the phasetransitions observed using DSC. Below498C, all images show the samplecompletely solid, being possible toobserve the crystals in thin overlappedlayers and presenting an irregularshape. At 258C, ambient temperature,the crystal was observed after the firsttransition (form1 in DSC). At 308C,morphology of crystals changes andthe image became brighter. Anotherphase transition was observed at 378Caccording the DSC data (form3) and

85

75

65

55

45

35

25

15

Temperature (°C)

Sub α

1°C/min5°C/min10°C/min20°C/min

αβ

β′

Hea

t flo

w (

u.a.

) En

do5

-5

5 15 25 35 45 55 65 75-5

Figure 4. Thermogramms of glycerol monolaurate (GM-C12).

Form 1

Form 2

Form 3

Form 4

15

20

25

30

35

40

Temperature (°C)

Hea

t flo

w (

u.a.

) En

do

5 15 25 35 45 55 65 75-5

1°C/min10°C/min5°C/min20°C/min

Figure 5. Thermogramms of glycerol carbonate laurate (GCE-C12).


finally at 498C, the last phase transitionbefore melting was observed. Here,it seems that numerous crystalspresent similar morphology. It is notingthat during heating, no liquid phaseappeared which means that phasechanges were solid/solid. Probablyglycerol carbonate laurate crystalsare composed of a mixture of phaseswith different crystallographic charac-teristics. To identify them, a study byX-Ray diffraction should be carriedout.

Self-assembling with water

When heating monoglycerides andglycerol carbonate esters in presenceof water above their melting point orKraft point, coagel can be obtained.Coagels are made up of densely packedlamellar layers of surfactants interlockedby hydrophilic regions that contain aspecific amount of strongly bound

water molecules. The stability of mono-glyceride layers is related to the specificamount of the ‘‘frozen’’ water mole-cules. DSC experiments provide infor-mations on the number of hydrationwater molecules strongly interactingwith the amphiphilic headgroupsthrough hydrogen bonding (Ambrosiet al., 2004). In formulation the crystalsare linked in connective domains orjunction zones, probably containing allof the material. Each substance actseither by substituting part of thehydration water molecules, or by inser-tion within the hydrophobic tail domainor in the hydrophilic region. Thisstabilizes the hydrated mixture of fattyacid esters on the surfaces. Calorimetricstudies showed the presence of twotypes of water in the coagel phase: bulkor free water that freezes and thenmeltsat about 0 8C, and frozen, stronglybound water that does no melt in thetemperature range investigated. DSC

experiments allow the determination ofthe percentage of strongly bound waterper hundred grams of sample, Wb(%).It can be calculated from the decreaseof the area of the endothermic peakassociated with the melting of bulkwater, as follows:

Wb(%) = (100 – P)333.79–∆Hexp

333.79

Here 333.79 J g-1 is the heat of meltingof pure water (Dean, 1985) and DHexp isobtained from the measured peak areafor each coagel at a glycerol carbonateester concentration P. The number ofstrongly bound water molecules persurfactant polar headgroup, N, can becalculated as follows: N=(Mn Wb)/(Mw

P) where Mw and Mn are the molecularweights of water and glycerol carbonateester, respectively. Strongly bound wa-ter molecules form a thin compartmentsandwiched between the surfactantbilayers, whereas bulk water surroundsthe plate like ‘‘islands’’ and dissolves thefew monomers in equilibrium with thecoagel phase. The gelation of mono-glycerides has been studied (Krog,1975), and it can be calculate fromthe determined diffraction parametersthat 14.4 molecules of water per mole-cule of monoglyceride are involved in60/40 w/w monoglyceride-water. Inthe same conditions replacing glycerolmonolaurate by glycerol carbonatelaurate, this value decrease to 4.4molecules of water per molecule ofglycerol carbonate laurate as shown infigure 8.

These results are consistent with thechemical nature of monoglycerides andglycerol carbonate esters. Monoglycer-ides are donor-acceptor of hydrogenbond whereas glycerol carbonate estersare only acceptor. Monoglycerideshave the ability to ‘‘freeze’’ morewater molecules than glycerol carbon-

70

60

50

40

30

20

10

0

6 7 8 9 10 11 12 13 14-10

Tem

per

atur

e (°

C)

Fatty acid carbon number

Figure 6. Transition temperatures (� form 1, form 2, form 3 and form 4) observed byDSC for fatty acid glycerol carbonates esters of different chain length GCE-C8, GCE-C9, GCE-C10, GCE-C12 and melting point temperature of monoglycerides.

Form125°C

Form230°C

Form337°C

Form449°C

Figure 7. Light microscopy images of glycerol carbonate laurate. Magnification 100 times.


ate esters. By self-aggregation, glycerolcarbonate laurate is an efficient water-reppellent molecule.

Surface activity

Surface tensionmeasurements allow thedetermination of several importantparameters. Accepting that Gibbs ad-sorption model describes the behaviorof micellization for esters, from theplot of surface tension values againstthe natural logarithm of concentration

(figure 9), before micellization, it ispossible to determine the surface excessand the molecular area, accordingequations:

= and A =-Γ 1RT T,P

1NAΓ

∂γ∂inC

Where G is the surface excess, A themolecular cross-sectional area, NA theAvogadro’s number, T the temperature,R the gas constant, P the pressure and Cthe concentration.

Figure 9 shows profiles obtained forsurface tension variations upon mono-glycerides and glycerol carbonateesters. Surface excess values were de-termined where a linear dependencebetween surface tension and concen-tration natural logarithm was observed.It has to be stressed that the mechanismof aggregation (e.g., micellization,pseudophase separation, etc.) doesnot affect the process of estimating Asince all the data points that are takenfor the calculations correspond toconcentrations lower than the concen-tration at which the aggregation pro-cess starts. For the solutions thatremained clear, the critical aggrega-tion concentration (CAC) is expectedto correspond to the critical micelleconcentration (CMC). In the case ofsolutions that appeared turbid in thevicinity of the concentration where asurface tension plateau was observed,the term CAC can still be appliedbecause a reversible aggregation pro-cess was taking place and the surfac-tants can also called solvo-surfactants(Queste et al., 2006). For reasons ofconsistency we will be describing all ofthe compounds studied in terms oftheir CAC and the surface tension atthe CAC. The CAC in this study has beengraphically determined by plottingsurface tension against the logarithmof the weight/volume concentration.Two straight lines were fitted to thesteep and the (nearly) flat part of thesurface-tension curves. The results arepresented in table 1. The data plottedin figure 9 can be used to produceestimates of the cross-sectional areaof the surfactant molecules at theinterface, assuming their adsorption isdescribed by the Gibbs adsorptionisotherm. These values are shown intable 1. Glycerol carbonate esters havethe bulkiest headgroup at the interface.The calculated value of A for glycerolheptanoate (GM-C7) is 25.6 A2 lower ofvalue obtained for glycerol carbonateheptanoate 38.7 A2. Knowing A, it ispossible to predict the geometry ofthe aggregates by applying the criticalpacking parameter criterion, CPP(Israelachvili et al., 1976).

CPP is calculated by the:

CPP =Alcv

where v is the volume of the hydrocar-bon chain, A is headgroup area, and lc

040 50 60 70 80 90 100

N (

mol

/mol

)

% GEC-C12 in water

1

2

3

4

5

6

Figure 8. Number of strongly bound water molecules per molecule of glycerol carbonatelaurate.

70

65

60

GCE-C7GCE-C9GCE-C8GM-C7

GM-C11:1GM-C12

55

50

45

40

35

30

25

20-12

LnC

Surf

ace

ten

sio

n (

mN

/m)

-11 -10 -9 -8 -7 -6 -5 -4

Figure 9. Surface tension (by Wilhemy plate technique) vs natural logarithm of the concentra-tion C (in mg.mL-1) at 258C.


is the average length of the hydrophobictail. For hydrocarbon chains the follow-ing formulas can be used (Tanford,1980),

v = 27.4 + 26.9n (in Å,) (in A3)

lc ≤ lmax = 1.5 + 1.265n (in A)

Where n is the number of carbon atomsof the hydrophobic chain. The effectivehydrophobic chain length of the fattyacids should be close to nc-1, where nc isthe number of carbon atoms in the fattyacid. The CPP predicts spheres, rods,bilayers, and inverse structureswhenCPP< 1/3, 1/3 <CPP < 1/2, 1/2 <CPP< 1,and CPP > 1, respectively. The results ofthe calculations are presented in table 1.It has to be stressed that the micelleshape derived from this method isjust an estimate based on simplegeometric considerations. The methodprovides no information on the poly-dispersity of the micelles present in thesystem.

Results showed that monoglyceridesaggregate inbilayers.Glycerol carbonateesters, exceptCGE-C7give aggregates inrods with CPP values close of esters ofpolyethyleneglycol of same chain length(C9COE3 and C9COE4) (Zhu, 2009). Wenoted too that glycerol carbonate esterspolar head is a monomer unit ‘‘glycerolcarbonate’’ while polyethylene glycolpolar head is an oligomeric moiety of3 or 4 ethylenic groups.

Lipophilic activity

A first estimation of the polarity of asubstance can be performed by lookingat its logP value. The octanol-waterpartition coefficient, P, expresses thedifferential solubility of a substance

between these two immiscible solvents.It equals the ratio of the concentrationof the substance solubilized in octanolover the concentration of the substancesolubilized in water. Therefore, it isoften used as a descriptor of thehydrophobicity. Monoglycerides canprovide more links with water thanglycerol carbonate esters as explainedin previous part. This can be alsoillustrated in figure 10. LogP of mono-glycerides and glycerol carbonate estersare compared. Both experimental andcalculated values are plotted for GCE-Cs.Calculated values are lower than experi-mental values. GM-Cs logP values arefurthermore lower than those of GCE-Cs.It can be deduced that GCE-Cs, for sameatom carbon number on the fatty acidchain, are more lipophilic than GM-Cs.

Wecan suppose thatmonoglycerides areresponsible of the stability of hydratedcoagel in surface glycerol carbonateesters-monoglycerides formulations.

Surface formulation

Formulations of glycerol carbonateoctanoate, with high affinity with polarsurfaces and monoglycerides of highmelting point like glycerol monolaurate,can be applied by simple deposition andconfer to metal and polymer surfacesuperhydrophilic properties (figure 11).We showed a synergy between meltingand solvo-surfactive properties to obtainsuperhydrophilic surfaces (Valentin et al.,2012).

Water contact angle measurements(figure 11) showed that steel (S) and

Table 1. Physicochemical properties of monoglycerides and glycerol carbonate esters (25 8C).

CMC/CAC(mmol/L)

CMC/CAC(mg/L)

A Area/molecule(A2)

Vm(A3)

L(A)

g cmc(mN/m)

CPP Geometry

GM-C7 1.00 204 25.6 188.8 9.09 35.3 0.81 Bilayers

GM-C11:1 0.38 89.0 23.0 296.4 15.0 36.9 0.91 Bilayers

GM-C12 0.29 79.5 31.1 323.3 15.4 24.1 0.68 Bilayers

GCE-C7 1.13 259.9 38.7 188.8 9.1 44.4 0.54 Bilayers

GCE-C8 0.41 100.0 42.1 215.7 10.4 33.3 0.49 Rods

GCE-C9 0.25 64.5 60.0 242.6 11.6 35.5 0.35 RodsaC9COE3 0.9 273.6 45 - - 27.3 0.47 RodsaC9COE4 0.8 278.4 50 - - 28.5 0.42 Rods

a (Zhu 2009).

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.56

Carbon number on fatty chain

Log

P

8 10 12 14

Experimental GCE-Cs Calculated GCE-Cs Calculated GM-Cs

Figure 10. logP values of glycerol carbonate fatty acid esters and monoglycerides. HyperchemTM

Release 7.01. HyperChem QSAR Properties v. 7.0 was used to calculate logP. Experimentalvalues were carried up by liquid phase chromatography method on reverse C18 phase column.


polyvinyl chloride (PVC) surfaces, allcoated with monoglycerides and for-mulations of monoglycerides and glyc-erol carbonate esters, exhibit lowercontact angle values in comparison touncoated surfaces. The quality of water-repellent surfaces was improved byimproving the purity of fatty acid esters.When using only high-purity gradefatty-acid esters, high leaching-resistantsuperhydrophilic surfaces could beobtained. The stability of the coatingwas due to the formation of stablecoagels on the surfaces. This highlysuperhydrophilic coating was carried upby biomolecules containing odd num-bers of carbon on their fatty acid chainGM-C7, GM-C11:1 and even numbers

of carbon on GM-C12 and GEC-C8.Here, higher melting point GM-C12acted as surface texture agent and thelower melting point GM-C7, GM-C11:1and GEC-C8 as solvo-surfactant agents.Indeed, structuration, texture, solvo-surfactant action, and lowwater contactangles (u<108) gave superhydrophili-city. At ambient temperature, GM-C7and GCE-C8 were liquid and acted assurfactant deposited on the surfaces,leading to the decrease of the watercontact angle by detergency. GM-C12was crystallized on the surfaces and wasin a solid state. SEM analysis of GM-C12deposited on steel surfaces (figure 12)showed that the surface was very welltextured at the micrometer scale

(figure 12). We can see numerousasperities of submicrometric dimension,range where capillarity phenomenataking place. Dong et al. used thisconcept by adding silica nanoparticlesto relatively low hydrophilic polymers.Incorporation of the nanoparticles signi-ficantly decreased the contact angle dueto the increase in surface roughness andresulting 3D capillary hydrophilicity(Dong et al., 2010).

Wettability by water is then enhancedwhich lead to increase the hydrophilicityof the surfaces. The concept of mixingcapillarity phenomena with detergencycan be considered as a biomimeticapproach. Indeed, in Ruellia devosiana(Koch and Barthlott, 2009) the glandssecreted surfactant substances that incombination with the surface roughnessleaded to superhydrophilicity. The wa-ter droplet spreading coefficient S wasvery close to 0 and in this case, a verylow inclination of a few degrees of thecovered surface was sufficient for a dropof water to flow spontaneously. Onsurfaces, in presence of water, multilay-er deposited fatty acid esters formcoagels (Sein et al., 2002; Ambrosiet al., 2004) and when a drop of waterwas deposited, the coagel behave like awater surface and the drop water meetsthis high hydrophilic coagel surface andspreads spontaneously.

Conclusion

The transformation pathways of naturalglycerin for the directed synthesis ofagro-C3 highly reactive synthons likeglycerol carbonate and glycidol openthe door to the synthesis and develop-ment of non-ionic interfacial agentsthat are esters of glycerol and fattyacids, pure monoglycerides, and estersof glycerol carbonate and fatty acids.The respect of the twelve principles ofthe green chemistry is achieved by thedevelopment of this C-3 glycerol basedchemistry including atom economy,synthesis without solvent and use ofthe multifunctionality of the reactantsand products. Indeed, solvo-thermal,hydroxy solvo-thermal and self-assem-bled reactive media can be use, withoutadding solvent and additional surfac-tants. Glycerol and glycerol carbonateare reactants which can act as solventsand thermal conductors. Monoglycer-ides and glycerol carbonate esters arereaction products and solvo-surfactant

90

80

70

60

50

40

30

20

10

0

Free s

urfac

e

GM-C

12

GM-C

12/G

CE-C8

GM-C

12/G

C-C7

GM-C

12/G

M-C

11:1

Wat

er c

on

tact

an

gle

(°)

S

PVC

Figure 11. Water contact angles on steel (S) and polyvinyl chloride (PVC) surfaces.

Figure 12. SEM images of glycerol monolaurate on steel surface. The sample is tilted at 708relative to the electron beam (Valentin et al., 2012).


molecules that can play the role ofsolvent, surfactant and compatibilizingagent. We showed that glycerolcarbonate esters are new polymorphicmolecules different from monoglycer-ides. Carbonation decreases meltingpoints: two hydroxyl functions areblocked on GCE-Cs while GM-Cs pres-ent two hydroxyl functions involved inintra and intermolecular hydrogenbonds. Carbonation decreases thehydrophilic character of the polar headin surface-active GCEs. Short chain andmedium chain GM-Cs and GCE-Cs aresolvo-surfactants molecules. They aredurable water-repellent agents. Formu-lation of monoglycerides and glycerolcarbonate esters on surfaces inducesuperhydrophilicity by biomimetism.This study open the way to new usesfor theses self-assembled biomoleculeslike surface protection, stabilization byemulsification, transport of water andprotic molecules.

Disclosure

Conflict of interest: none.

REFERENCES

Ambrosi M, Lo Nostro P, Fratoni L, et al.

Water of hydration in coagels. Phys Chem

Chem Phys 2004; 6: 1401-7.

Anastas PT, Warner JC. Green Chemistry:

Theory and Practice. Oxford: Oxford Universi-

ty Press, 1998.

Bauer U, Bohn HF, Federle W. Harmlessnectar source or deadly trap: Nepenthes

pitchers are activated by rain, condensa-

tion and nectar. Proc R Soc B 2008; 275:

259-65.

Burgos CE, Ayer DE, Johnson RA. A new,

asymmetric synthesis of lipids and phospho-

lipids. J Org Chem 1987; 52: 4973-7.

Caron M, Sharpless KB. Titanium isoprop-

oxide-mediated nucleophilic openings of

2,3-epoxy alcohols. A mild procedure for

regioselective ring-opening. J Org Chem1985; 50: 1557-60.

Cauvel A, Renard G, Brunel D. Monoglycer-

ide Synthesis by Heterogeneous CatalysisUsing MCM-41 Type Silicas Functionalized

with Amino Groups. J Org Chem 1997; 62:

749-51.

Cebeci FC, Wu Z, Zhai L, Cohen RE, Rubner

MF. Nanoporosity-Driven Superhydrophili-city: A Means to Create Multifunctional

Antifogging Coatings. Langmuir 2006; 22:

2856-62.

Claude S, Mouloungui Z, Yoo JW, Gaset A.

Process for the preparation of glycerol

carbonate EP0955298(A1) 2001.

Corma A, Iborra S, Velty A. Chemical Routes

for the transformation of biomass into

Chemical. Chem Rev 2007; 107: 2411-502.

Dong H, Ye P, Zhong M, Pietrasik J, Drum-right R, Matyaszeski K. Superhrophilic sur-

faces via polymer-SiO2 nanocomposites.

Langmuir 2010; 26: 15567-73.

Dean JA. Lange’s Handbook of Chemistry. NewYork: McGraw-Hill Book Company, 1985.

Drelich J, Chibowski E. Superhydrophilic and

superwetting surfaces: definition and mech-anisms of control. Langmuir 2010; 26:18624-

3.

Eychenne V, Mouloungui Z. High concen-

tration of 1-(3-)monoglycerides by directpartial esterification of fatty acids with

glycerol. Fett/Lipid 1999; 101: 424-7.

Fujimura M, Yamauchi H, Matsushita T,

Oshima M, Oya K. Shortenings containingglycerides and amylase and/or protease and

their manufacture. Japanese Patent JP 03 292

848, 1991.

Gahe G, Lachowicz A. Esters containing cyclic

carbonate, and process for their preparation.

EP0328150(A2) 1989.

Hartunian-Sowa SM, White PJ, Batres LV.Influence of monoglycerides of different

chain lengths on texture and flavor of breads

made with waxy cornstarch. Starch 1990; 42:

53-6.

Israelachvili J, Mitchell D, Ninham BW.Theory of self-assembly of hydrocarbon

amphiphiles into micelles and bilayers.

J Chem Soc Faraday Trans 1976; 2: 1525-68.

Kabara JJ, Lie MSF. Antimicrobial lipids:natural and synthetic fatty acids and mono-

glycerides. Lipids 1977; 12: 753.

Kato N. Antimicrobial activity of fatty acids

and their esters against a film-forming yeast

in soy sauce. J Food Safety 1981; 3: 121-6.

Kamei T, Teraoka T, Hirano H. Antistatic

acrylic polymer or polycarbonate laminate

sheets. Japanese Patent JP 02 276 636,1990.

Koch K, Barthlott W. Superhydrophobic andsuperhydrophilic plant surfaces: an inspira-

tion for biomimetic materials. Phil Trans R Soc

A 2009; 367: 1487-509.

Krog N. Interaction between water and

surface active lipids in food systems. In:

Duckworth RB (Ed.), Water Relation of Foods.London: Academic Press: 1975: 587.

Lachowicz A, Gahe G. Cyclo-carbonate-

contg. ester(s) - by reaction of corresp.cyclo-carbonate-alcohol(s) with mono- or

di-carboxylic acids in the presence of acid

catalyst and solvent DE3937116(A1) 1991.

Leser ME, Sagalowicz L, Michel M, Watzke H.

Self-assembly of polar food lipids. Adv Colloid

Interface Sci 2006; 123-6: 125-36.

Lok C. M. Glyceride Esters. U.S. Patent

4,234,498, 1980.

Malkin T. The polymorphism of glycerides.

Prog Chem Fats Other Lipids 1954; 2: 1-50.

Mc Intire RT. Fatty Acids in Industry; New York:

Marcel Dekker, 1989.

MoulounguiZ.Voies inhabituellesde synth�ese

de compos�es ol�eophiles �a partir des substratsv�eg�etaux solides (graines ol�eoprot�eagine-

uses), liquides (huiles v�eg�etales et d�eriv�es,

glyc�erol) pour l’industrie chimiqueOCL 2004;11: 425-35.

Mouloungui Z, Yoo JW, Gachen CA, Gaset A.

Vermeersch G. Process for the preparation of

glycerol carbonate from glycerol and a cyclicorganic carbonate, especially ethylene or

propylene carbonate EP0739888A1, 1996.

Mouloungui Z, Gauvrit C. Synthesis and

influence of fatty acid esters on the foliarpenetration of herbicides. Ind Crops Prod

1998; 8: 1-15.

Mouloungui Z, Rakotondrazafy V, Valentin R,Zebib B. Synthesis of glycerol 1-monooleate

by condensation of oleic acid with glycidol

catalyzed by anion-exchange resin in aque-

ous organic polymorphic system. Ind EngChem Res 2009; 48: 6949-56.

Mouloungui Z, Pelet S. Study of the acyl

transfer reaction: Structure and properties

of glycerol carbonate esters. Eur J Lipid SciTechnol 2001; 103: 216-22.

Mouloungui Z, Yoo JW. Glycerol catalytic

carbonation: stoechiometric technology

versus catalytic alternative for design ofglycerol carbonate. Proceedings of Oleo

and Speciality Chemicals Conference PIPOC

2007, 26-30 August 2007: 144-69.

O’Brien JL, Beavers EM. Process for preparing

carbonatoalkyl acrylates and methacrylates.

US patent 2979514, 1961.

Oki M, Nakanishi H. Conformations of the

esters. V. Conformations of carbonates.Bull Chem Soc Jap 1973; 44: 3419-23.

Oehlenschl€ager J, Gercken G. Synthesis and

mass spectrometry of 1-acyl and 3-acyl-

sn-glycerol carbonates. Lipids 1978; 13:

557-62.

Queste S, Bauduin P, Touraud D, Kunz W,Aubry JM. Short chain glycerol 1-mono-

ethers-a new class of green solvo-surfactants.

Green Chem 2006; 8: 822-30.

Rieger M. Glyceryl stearate, chemistry and

use. Cosmet Toiletries 1990; 105: 51-7.

Sein A, Verheij JA, Agterof WGM. Rheologicalcharacterization, crystallization, and gelation

behavior of monoglyceride gels. J Colloid

Interface Sci 2002; 249: 412-22.


Silvestre F, Aubry JM, Benvegnu T, et al.

Agroressources pour une chimie durable.

Actual Chim 2010; 338-9: 28-40.

Tamura T. Preparation of higher fatty acid

monoglycerides from fatty acids and glyci-

dol. Japanese Patent JP 04182451, 1992.

Tanford C. The hydrophobic effect. NewYork:Wiley Interscience, 1980.

Valentin R, Alignan M, Giacinti G, Renaud

FNR, Raymond B, Mouloungui Z. Pure

short-chain glycerol fatty acid esters andglycerylic cyclocarbonic fatty acid esters as

surface active and antimicrobial coagels

protecting surfaces by promoting super-hydrophilicity. J Colloid Interface Sci 2012;

365: 280-8.

Vieville C, Yoo JW, Pelet S, Mouloungui Z.

Synthesis of glycerol carbonate by direct

carbonatation of glycerol in supercritical CO2in the presence of zeolites and ion exchange

resins. Catal Lett 1998; 56: 245-7.

Vriet C,Mouloungui Z. Organic carbonates: a

neglected family of compounds. Actual Chim2008; 315: 19-27.

Werpy T, Petersen G (Eds.). Top value added

chemicals from biomass 2004. PNNL, NREL,

EERE (report 8674).

Yoo JW, Mouloungui Z. Catalytic carbonyla-

tion of glycerin by urea in the presence of zinc

mesoporous system for the synthesis ofglycerol carbonate. Stud Surf Sci Catal

2003; 146: 757-60.

Yoo JW, Mouloungui Z. The catalytic synthe-

sis of the glycidol from the glycerol carbonate

in presence of zeolite A. Stud Surf Sci Catal2001; 135.

Yoo JW, Mouloungui Z, Gaset A. Method for

production an epoxide, in particular of

glycidol, and installation for implementation.WO9840371(A1) 1998.

Zhu Y, Fournial AG, Molinier V, Azaroual N,Vermeersch G, Aubry JM. Self-association of

short-chain nonionic amphiphiles in binary

and ternary systems: comparison betweenthe cleavable ethylene glycol monobutyrate

and its ether counterparts. Langmuir 2009;

25: 761-8.


Documents

Superhydrophilic surfaces from short and medium chain ... · Cs and GCE-Cs are multifunctional molecules with amphiphilic structures: a common hydrophobic chain to the both families