A　series　of　double-chain　sulfobetain　zwitterionic　surfactants　with　varying　carbon　number　of　the　intercharge　group　(spacer),　(C16H33)2NCH3(CH2)nSO3,　where　n=2,　3,　4,　and　6,　referred　to　as　(C16)2NCnS,　were　synthesized.　The　influence　of　the　spacer　length　on　the　thermal　behaviors　of　(C16)2NCnS　in　their　pure　state　was　studied　using　thermogravimetry　(TG),　differential　scanning　calorimetry　(DSC),　polarizing　optical　microscopy　(POM),　and　X-ray　diffraction　(XRD).　Thermogravimetric　analysis　(TGA)　showed　that　the　thermal　stability　of　(C16)2NCnS　lowered　with　increasing　the　spacer　length.　All　compounds　showed　a　complex　polymorphism.　Only　for　(C16)2NC4S　and　(C16)2NC6S,　thermotropic　liquid　crystals　were　observed　using　POM.　The　former　exhibited　a　smectic　A　(SmA)　phase,　whereas　the　latter　formed　a　hexagonal　columnar　phase.　These　liquid　crystals　obtained　both　in　the　cooling　and　the　second　heating　scans　provided　compelling　evidence　for　the　thermal　stability　of　these　compounds.　©　2008　Chinese　Chemical　Society　and　College　of　Chemistry　and　Molecular　Engineering,　Peking　University.