对-(月桂基)苄基聚氧乙烯醚羧酸甜菜碱的合成与表面活性

Synthesis and surface activities of p-(n-lauryl)-benzyl polyoxyethylene ether carboxybetaine

以月桂酸、苯、聚乙二醇为原料,合成了4种具有不同氧乙烯数(分别为1,2,3,4)的对-(月桂基)苄基聚氧乙烯醚羧酸甜菜碱两性离子表面活性剂。用FTIR,1HNMR和ESI-MS对产物进行了结构鉴定。用吊片法测定了30℃时它们在水溶液中的临界胶束浓度(cmc)和表面张力(γcmc)。结果表明,水溶液中它们的cmc都达到了10-6mol·L-1,γcmc为29～35 mN·m-1;随着聚氧乙烯单元的增多,4种表面活性剂的cmc先变化不大后开始减小,而饱和吸附量则先增大后减小,分子在溶液表面的极限占有面积先减小后增大,相应的γcmc先减小后增大。

Four kinds of p - （ n - lauryl） - benzyl polyoxyethylene ether carboxybetaine with different number of ethylene oxide units （1,2,3,4） were synthesized by using lauric acid, benzene and polyethylene glycol as starting materials. Structure of the products was characterized by FFIR, 1HNMR and ESI - MS methods. Critical micelle concentration （cmc） and the surface tension at the cmc （γcmc） of the surfactants in aqueous solution at 30 ℃ were measured by means of the Wilhelmy - plate method. Results showed that cme of the all four products achieves order of magnitude of 10-6 mol · L-1, and γcmc achieves 29 -35 mN· m-1. Following the increase of EO number in the spacer group, cmc value shows slight change in the beginning and decreases later. The γcmc increases firstly and then reduces later. The Amin reduces firstly and then increases later. The γcmc shows decrease initially and then increases later.