pH值对聚乙二醇渗透材料的影响及NMR的分析

为了探讨聚乙二醇(PEG)渗透材料在不同pH条件下的性能,用NaOH溶液和稀盐酸调节PEG渗透材料的pH值.采用核磁共振研究不同pH值条件对PEG结构的影响.研究表明:当pH值在2~8时,PEG渗透材料放置7d可以保持稳定的pH值;在酸性条件下,由于PEG中的O对酸中H+形成作用,削弱了O原子对与O间接相连的-CH2基团的引力,使该-CH2基团中的H原子的化学位移向低场偏移,但PEG的结构不变;在pH值大于8的条件下,氢键的形成导致线状的PEG发生立体扭结,从而产生沉淀.因此,在pH值为2~8的范围内,可以稳定使用PEG渗透材料.

Effect of pH on poly(ethylene glycol)osmotic agent and its NMR analysis

To discuss the performances of poly(ethylene glycol) osmotic agent under different pH conditions, pH value of it was adjusted by NaOH or hydrochloric acid solution. The influences of different pH values on PEG structure were detected by NMR. The results showed that when the pH value of poly(ethylene glycol) osmotic agent was in a range of 2 to 8, the osmotic agent was steady in seven days. When the hydrochloric acid solution was added into the poly(ethylene glycol) osmotic agent, the action between oxygen atom of glycol and H+ion of solution weakened the interaction between oxygen atom and the indirect —CH2 group. Although the chemical shift of the —CH2 group was shifted to low field, the poly(ethylene glycol) structure was steady under this condition. When the pH value was higher than 8, hydrogen bond was formed and this led to the three-dimensional frame structure, thus the precipitate was obtained.So the pH value of 2 to 8 is a proper range for poly(ethylene glycol) osmotic agent application.