变温核磁共振对壳聚糖/磷酸甘油盐温敏性水凝胶的初步研究

采用变温核磁共振技术对壳聚糖/磷酸甘油盐温敏性水凝胶体系的凝胶化过程进行跟踪研究. 实验结果表明, 壳聚糖中氢和磷酸甘油盐中磷的化学位移均随着温度的升高而变化, 其中壳聚糖中氢的化学位移向高场移动而磷酸甘油盐中磷的化学位移向低场移动. 在凝胶温度附近, 壳聚糖中H-2(D)的化学位移变化出现转折点, 表明其所处的化学环境发生了突变. 随着体系中磷酸甘油盐含量的增加或者pH值的增大, 壳聚糖中H-2(D)的化学位移愈加偏向高场, 体系的凝胶温度则越低. 由此, 我们提出如下壳聚糖/磷酸甘油盐温敏性水凝胶的凝胶机理: 随着温度的升高, 壳聚糖通过氨基正离子与磷酸甘油盐形成的静电吸引被破坏, 随之由于壳聚糖分子链间形成大量氢键而发生凝胶化.

Exploring Study of Chitosan/Glycerophosphate Thermosensitive Hy-drogel with Variable-temperature NMR

Variable-temperature NMR techniques were applied to monitor the gelation process of chito- san/glycerophosphate (CS/GP) thermosensitive hydrogel system. The results showed that the chemical shifts of protons in CS and phosphor in GP changed together while the temperature was increased. However, the protons in CS shown in 1H NMR spectra moved to the high field, but the phosphor shown in 13P NMR moved to the low field. In addition, the chemical shift of H-2(D) in CS showed a turning point around the gelation temperature, indicating that the chemical environment of H-2(D) has been changed dramatically. Moreover, the chemical shift of H-2(D) in CS moved to higher field and the CS/GP system showed the lower gelation temperature with the increase of either GP content or pH value of the CS/GP mixture. There- fore, the gelation mechanism of CS/GP thermosensitive hydrogel was deduced as follows: with the increase of temperature, the electrostatic interaction between CS and GP is broken down, followed by the formation of hydrogen bonds between CS macromolecular chains, which induce the gelation.