聚乙二醇葡糖苷脂肪酸酯合成及性质研究

Preparation and properties of surfactants from fatty acid esters of polyethylene glycol glucosides

以葡萄糖、聚乙二醇(PEG)和高级脂肪酸为原料,通过缩醛化、酯化等步骤,合成了一种新型的非离子表面活性剂——聚乙二醇葡糖苷脂肪酸酯.考察了催化剂、反应温度和乳化剂对酯化反应进程的影响.结果表明:以氧化锌或氢氧化钠为催化剂,反应温度为180℃,可获得较高的反应速率;加入乳化剂可有效促进两相体系混合,防止糖苷焦化.用电喷雾质谱(ESI-MS)对酯化产物结构进行了表征.测定了一系列酯化产物的酸值、羟值、皂化值和HLB值,研究了表面活性与分子结构的关系.表面活性剂的亲油基碳链增长,临界胶束浓度(ccm)呈降低趋势;亲水基中乙氧基数(EO)增加,临界胶束浓度呈增加趋势,表面张力降低的能力亦下降.

A new class of nonionic surfactants-the fatty acid esters of polyethylene glycol glucosides are prepared on the basis of glucose, polyethylene glycol (PEG) and fatty acid as starting materials by means of acetalization and esterification. The effects of catalyst type, reaction temperature and the addition of emulsifying agent on the esterification reaction rate are discussed. On condition that zinc oxide or sodium hydroxide are used as catalyst and reaction temperature is 180 ℃, the reaction rate is higher. The electrospray mass spectrometry (ESIMS) analysis has proved that the final products are the multicomponent surfactant mixture. Some properties of these surfactants such as acid value, hydroxyl value, saponification value and HLB value are determined. A series of products with different HLB values can be obtained by means of adjusting EO number of hydrophilic group and changing the proportion between PEG, glucose and fatty acid. The relationship between surface tension and chemical structures of surfactants is investigated. The results show that the critical micelle concentration (ccm) linearly decreases as the chain length of hydrophobic group increases and ccm linearly increases as EO number of hydrophilic group increases.