Langmuir · 2002 · 15 citations · 20 references
Natural SciencesChemistryMaterials ScienceInorganic ChemistryPhysical ChemistrySolid-state ChemistrySupramolecular MaterialsSurfactantsAnionic SurfactantsCryogenic Electron MicroscopyGemini SurfactantsIonic SurfactantsKrafft TemperaturePhase-contrast MicroscopySurfactant AggregationSurfactant Solutions
Two series of pyrophosphate-based gemini surfactants [diimidazolium ( 1 ) and disodium P,P ‘ -dialkyl pyrophosphate ( 2 ) ( a, R = 1-octyl; b, R = 1-dodecyl; c, R = 2-dodecyl)] were synthesized, along with a series of imidazolium monoalkyl phosphate surfactants ( 3a − c ) for comparison. The surfactants were characterized by measurement of their Krafft temperatures ( T k ) and critical aggregation concentrations (cac's). The T k and cac values of the pyrophosphate surfactants are lower than those of their conventional phosphate surfactant counterparts. Aggregated surfactants 1 and 3 in D 2 O were characterized by 1 H and 31 P NMR spectroscopy, and solutions of 1c and 3c in H 2 O were characterized by phase-contrast optical microscopy and cryogenic high-resolution scanning electron microscopy (cryo-HRSEM). By optical microscopy, fiberlike aggregates were observed for gemini surfactant 1c, and both fibers and rod/tubule-like aggregates were observed for its single-chain counterpart 3c . By cryo-HRSEM, lamellar ice was observed for both 1c and 3c . Also, a single-crystal X-ray diffraction study of 1b was performed, and its cleavable nature was demonstrated.
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