Ge Lingling, Guo Rong, Zhang Xiaohong
School of Chemistry and Chemical Engineering, Yangzhou University, Jiangsu Province 225002, P R China.
J Phys Chem B. 2009 Feb 19;113(7):1993-2000. doi: 10.1021/jp808218j.
Lamellar-to-isotropic phase transition is observed in the system of TX-100/n-C(8)H(17)OH/H(2)O induced by neutral water-soluble polymer poly(ethylene glycol) (PEG) with molecular weight ranging from 400 to 20 000. The location of PEG in the lamellar liquid crystal and the microstructure change of the lamellar phase during phase transition are investigated by means of (2)H NMR, small-angle X-ray diffraction (SXRD), rheology, polarized optical microscopy (POM), and freeze-fracture transmission electron microscopy (FF-TEM). Calculations based on the "swelling model" show that 0.92-2.58 wt % PEG2000 penetrates into the amphiphile layer and the rest resolve in the water layer. Both of these two kinds of locations induce the lamellar-to isotropic phase transition. The longer the chain length of PEG, the higher the efficiency is. In addition, a critical molecular weight of PEG is observed before phase transition occurs, with which the disturbance of PEG on the microstructure of lamellar liquid crystal is most prominent. The critical molecular weight of PEG is independent of the thickness of water layer. The value is 2000 for the system of TX-100/n-C(8)H(17)OH/H(2)O.
在由分子量范围为400至20000的中性水溶性聚合物聚乙二醇（PEG）诱导的TX-100/正辛醇/水体系中观察到片层向各向同性相的转变。通过2H NMR、小角X射线衍射（SXRD）、流变学、偏光显微镜（POM）和冷冻断裂透射电子显微镜（FF-TEM）研究了PEG在片层液晶中的位置以及相变过程中片层相的微观结构变化。基于“溶胀模型”的计算表明，0.92 - 2.58 wt%的PEG2000渗透到两亲层中，其余的溶解在水层中。这两种位置都诱导了片层向各向同性相的转变。PEG的链长越长，效率越高。此外，在相变发生之前观察到PEG的一个临界分子量，在此分子量下PEG对片层液晶微观结构的干扰最为显著。PEG的临界分子量与水层厚度无关。对于TX-100/正辛醇/水体系，该值为2000。
