Synthesis and Properties of Di-n-dodecyl α,ω-Alkyl Bisphosphate Surfactants

Three gemini and two bolaform bisphosphate surfactants of the type 12-s-12, with s = 6, 8, 12, 18, and 24 carbon atoms, have been synthesized and their aggregation behavior has been studied. The bolaform surfactants 12-18-12 and 12-24-12 were found to form vesicles in aqueous solution, as indicated by electron microscopy. The geminis 12-6-12, 12-8-12, and 12-12-12 form micellar structures. The cmc’s of the geminis, obtained from conductivity measurements, spectroscopic methods, and microcalorimetry, are very low, on the order of 10-4 to 10-5 M. The cmc decreases with increasing spacer length. For the bolaform amphiphiles 12-18-12 and 12-24-12 noncooperative phase transitions are detected using fluorescence depolarization and DSC. NMR line-broadening studies display unusual behavior. The spacer within the 12-24-12 vesicles has been found to be membrane spanning, as confirmed by X-ray powder diffraction