超声作用对超分子水凝胶结构及性能的影响

采用一种简便方法,以戊二酸酐和3-羟基2-氨基吡啶合成了一种新的凝胶因子3-羟基-2-N-(羧丙基羰基)氨基]吡啶(简称SWG),并采用IR、1H-NMR和元素分析确认其结构.红外光谱中2576cm-1和1906cm-1峰的出现证明羧基与吡啶基间形成了氢键.于20°C的超声仪中冷却1.5wt%的SWG水溶液,在1min内形成了超分子水凝胶.基于扫描电子显微镜(SEM)、示差扫描量热仪(DSC)及凝胶-溶液破坏温度(Tgel)分析表明,在凝胶化过程中,SWG自组装形成纤维状网络结构.随着超声功率由200W增加到500W,纤维宽度由8μm逐渐减小到2μm,凝胶网络密度逐渐增大,可冻结水含量逐渐增加,Tgel从60℃增加到70℃.因此,通过改变超声功率可有效控制凝胶的结构及性能.进一步增加SWG的浓度,可使纤维宽度及网络密度均增加,并导致凝胶的Tgel升高.采用多晶X射线衍射仪(XRD)分析表明,在凝胶形成过程中,SWG分子自组装出现明显的择优取向.

INFLUENCE OF ULTRASOUND TREATMENT ON ASSEMBLING STRUCTURES AND PROPERTIES OF SUPRAMOLECULAR HYDROGELS

A new gelator 3-hydroxy-2-N-(carboxypropyl carbonyl)amino] pyridine(defined as SWG) was synthesized from 3-hydroxy-2-amino pyridine and glutaric anhydride by a simple procedure.The gelator structure was confirmed by IR,1H-NMR and elemental analysis.The characteristic peaks of 2576 cm-1 and 1906 cm-1 in the IR spectrum indicated the formation of hydrogen bonds between carboxylic acid and pyridyl groups.Supramolecular hydrogels were formed within 1 min via cooling the 1.5 wt% SWG aqueous solution in an ultrasonic vessel at 20℃ under different ultrasonic powers.However,only macroscopic crystals were formed in the same solution without ultrasonic treatment.The gels were analyzed by SEM,DSC and gel-to-sol dissociation temperature(T_ gel) measurements.The results indicated that SWG molecules assembled into aggregating fibers during the gelating process.With increasing the ultrasonic powers from 200 W to 500 W,the fiber width decreased from 8 μm to 2 μm,the network density increased,the freezing water content increased from 86.5% to 96.1%,and the T_ gel increased from 60℃ to 70℃.Therefore the ultrasonic treatment is effective in controlling gel structures and properties.Furthermore,the gel with larger fiber,more compact fibrillar network and higher T_ gel were obtained as increasing the gelator concentration from 1 wt% to 2.5 wt%.The X-ray powder diffraction(XRD) analysis of xerogel and powder samples of SWG indicated that the molecules assembled in a preferred direction during the gelating process.These results are important for understanding the gelating mechanism and designing new hydrogels.