A　homologous　series　of　novel　heterogemini　surfactants,　(N,N-dimethyl-N-[3-(alkyloxy)-2-hydroxypropyl]alkylammonium　bromide　(referred　to　as　C(m)OhpNC(n);　m,　n　=　10,　8;　12,　8;　14,　8;　16,　8;　14,　10;　12,　12　and　10,　14)　were　synthesized.　Their　thermotropic　phase　behavior　was　investigated　by　differential　scanning　calorimetry　(DSC),　polarizing　optical　microscopy　(POM),　infrared　spectroscopy　(IR)　and　X-ray　diffraction　(XRD).　All　the　compounds　showed　high　thermal　stability　and　formed　enantiotropic　thermotropic　smectic　A　liquid　crystals.　The　mesophase　region　was　sensitive　to　the　overall　length　(m　+　n)　of　the　two　hydrophobic　tails　and　was　widened　with　increasing　(in　+　n).　When　fixing　the　overall　length　of　the　two　hydrophobic　tails　(m　+　n　=　24).　the　liquid　crystal　region　was　affected　little　by　the　dissymmetry　of　the　two　hydrophobic　chains.　The　combination　of　IR　and　XRD　results　suggested　the　cis-configuration　of　the　alkyl　chain　and　the　alkoxy　chain　with　respect　to　the　extended　N-CH2-CH(OH)　skeleton　in　both　crystal　lattice　and　liquid　crystal　mesophase.　The　folding　of　the　alkoxy　chain　at　the　carbon　atom　connecting　the　hydroxyl　group　led　to　the　hydrogen　bonding　between　the　hydroxyl　and　the　Br-　counterion,　which　is　beneficial　to　stabilizing　the　liquid　crystal　phase.　(C)　2008　Elsevier　Inc.　Ali　rights　reserved.