中文摘要：

合成了具有两根十六烷烃链，两个离子头基（季铵盐和磺酸盐）中变化不同长度联接链的新型磺基甜菜碱两性表面活性剂（C16H33）2NCH3（CH2）nSO3（记为（C16）2NCnS，n=2，3，4，6）。采用TGA、DSC、XRD和POM等技术考察了它们的热行为。研究表明，热分解温度随着联接链增长而降低；固相在加热过程出现了多种晶型转变，但只有（C16）2NC4S和（C16）2NC6S形成了液晶，前者为近晶A液晶，后者为六方柱状液晶。这些液晶在升温和降温过程中都被观察到，表明其热稳定性良好。

英文摘要：

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.