title: Micellization Behavior of Long-Chain Substituted Alkylguanidinium Surfactants.
abstract: Surface activity and micelle formation of alkylguanidinium chlorides containing 10, 12, 14 and 16 carbon atoms in the hydrophobic tail were studied by combining conductivity and surface tension measurements with isothermal titration calorimetry. The purity of the resulting surfactants, their temperatures of Cr→LC and LC→I transitions, as well as their propensity of forming birefringent phases, were assessed based on the results of ¹H and (13)C NMR, differential scanning calorimetry (DSC), and polarizing microscopy studies. Whenever possible, the resulting values of Krafft temperature (TK), critical micelle concentration (CMC), minimum surface tension above the CMC, chloride counter-ion binding to the micelle, and the standard enthalpy of micelle formation per mole of surfactant (ΔmicH°) were compared to those characterizing alkyltrimethylammonium chlorides or bromides with the same tail lengths. The value of TK ranged between 292 and 314 K and increased strongly with the increase in the chain length of the hydrophobic tail. Micellization was described as both entropy and enthalpy-driven. Based on the direct calorimetry measurements, the general trends in the CMC with the temperature, hydrophobic tail length, and NaCl addition were found to be similar to those of other types of cationic surfactants. The particularly exothermic character of micellization was ascribed to the hydrogen-binding capacity of the guanidinium head-group.
authors: Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. roza.bouchal@etud.univ-montp2.fr.
authors: Roza
authors: R
authors: Bouchal
authors: Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. ha_ab1@yahoo.fr.|Department of Chemistry, University Badji-Mokhtar, BP12 Annaba, Algeria. ha_ab1@yahoo.fr.
authors: Abdellah
authors: A
authors: Hamel
authors: Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. peter.hesemann@umontpellier.fr.
authors: Peter
authors: P
authors: Hesemann
authors: Laboratoire Charles Coulomb, UMR 5221 CNRS-UM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. martin.in@univ-montp2.fr.
authors: Martin
authors: M
authors: In
authors: Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. benedicte.prelot@umontpellier.fr.
authors: Bénédicte
authors: B
authors: Prelot
authors: Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Place Eugène Bataillon, F-34095 Montpellier cedex 5, France. jerzy.zajac@umontpellier.fr.
authors: Jerzy
authors: J
authors: Zajac
mesh_terms: D002151:Calorimetry; D002412:Cations; D019791:Guanidine / Q000031:analogs & derivatives / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature
chemical_list: D002412:Cations; D008823:Micelles; D013501:Surface-Active Agents; D019791:Guanidine
keywords: Krafft temperature; alkylguanidinium chlorides; critical micelle concentration; standard enthalpy of micelle formation; surface tension; surfactants