Monitoring Micelle Formation of Nonionic Polyurethane in Water by Fluorescence Spectrophotometry

A series of nonionic polyurethanes were dissolved in water and their miceller self-assembly behaviors were characterized by aid of a fluorescence spectrophotometer. Fluorescence and resonance light scattering techniques were carried out for characterizing the micelles, and information such as aggregation number, critical micelle concentration, micropolarity, and micelle volume change was obtained. The micropolarity decreased as the aggregation number increased. The nonionic polyurethane micelle volume with two long ethoxyl chains per polyurethane molecule was smaller than the one with short chains, even with the same aggregation number, and was less polar. The micropolarity depended on both the aggregation number and the volume of a single micelle.     

Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm^?3) and Tween 80 (1 mol dm^?3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.     

苄泽类非离子型表面活性剂与明胶的相互作用

采用表面张力和稳态荧光光谱法考察了具有不同疏水结构的2种苄泽类非离子型表面活性剂Brij58和Brij78与明胶之间的相互作用。结果表明,苄泽类非离子型表面活性剂与明胶之间相互作用的驱动力为疏水作用力,且两者之间的相互作用受到其疏水基团的影响,Brij78在明胶溶液中的临界聚集浓度低于Brij58体系,表明疏水链更长的Brij78与明胶之间的相互作用更强。明胶分子的内源荧光光谱强度受苄泽类非离子型表面活性剂的影响,但最大吸收峰位置未发生蓝移,Brij78/明胶体系的内源荧光强度高于Brij58/明胶体系;此外,表面活性剂浓度较低时,明胶的加入使溶液中疏水微区极性明显降低,且明胶浓度越大降低程度越大。