Surfactant behavior of ionic liquids involving a drug: from molecular interactions to self-assembly.
Aggregates formed in an aqueous medium by three ionic liquids CnMImIbu made up of 1-alkyl-3-methyl-imidazolium cation (n = 4, 6, 8) and ibuprofenate anion are investigated. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), (1)H nuclear magnetic resonance measurements, and atom-scale molecular dynamics simulations are used to shed light on the main interactions governing the formation of the aggregates and their composition. At high concentration, mixed micelles are formed with a composition that depends on the imidazolium alkyl chain length. For the shortest alkyl chain, micelles are mainly composed of ibuprofenate anions with some imidazolium cations intercalated between the anions. Upon increasing the alkyl chain length, the composition of the aggregates gets enriched in imidazolium cations and aggregates of stoichiometric composition are obtained. Attractive interactions between these aggregates led to the formation of larger aggregates. As suggested by molecular simulations, these larger aggregates might constitute the early stage of phase separation. Transitions from micelles to vesicles or ribbons are observed due to dilution effects and changes in the chemical composition of the aggregates. We also show that aggregation can be probed using simple microscopic quantities such as radial distribution functions and average solvation numbers.
Institut Charles Gerhardt Montpellier, UMR 5253, CNRS-UM2-ENSCM-UM1 Place Eugène Bataillon, CC1701, 34095 Montpellier, France .
Corine
C
Tourné-Péteilh
Benoit
B
Coasne
Martin
M
In
David
D
Brevet
Jean-Marie
JM
Devoisselle
André
A
Vioux
Lydie
L
Viau
D002626:Chemistry, Pharmaceutical; D007052:Ibuprofen / Q000031:analogs & derivatives* / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D056004:Molecular Dynamics Simulation; D013501:Surface-Active Agents / Q000737:chemistry*
D052578:Ionic Liquids; D008823:Micelles; D013501:Surface-Active Agents; C547231:imidazolium ibuprofenate; D007052:Ibuprofen