OMR的合成及与其他表面活性剂混合溶液的表面性质

用酯交换甲酯化法合成出蓖麻油酸甲酯,将分离出的蓖麻醇酸甲酯与环氧乙烷反应,得到蓖麻醇酸甲酯乙氧基化物(OMR,EO平均数为10)。OMR及其与其他表面活性剂混合溶液的表面张力曲线表明,OMR分子在气液界面上的吸附和排布比较特殊,导致它的γCMC较大,为36.78 mN/m;但较大的分子结构也使它有比较低的CMC,为4.58×10-5mol/L。OMR与AEO9的混合溶液近似于理想溶液,其表面张力和CMC介于二者之间;OMR的加入能够使SDS的CMC降低近2个数量级,但混合溶液的协同作用不强;OMR与CTAB有很强的协同作用,混合溶液的表面张力曲线出现最低点,其γCMC值最小可达28.24 mN/m,远小于OMR的36.78 mN/m和CTAB的36.62 mN/m,混合溶液的CMC最低为2.80×10-5mol/L,亦低于OMR的CMC。

Synthesis of OMR and Surface Properties of Mixtures of OMR with Other Surfactants

Methyl ricinoleate was produced from castor oil by ester exchange reaction.Oxyethylated methyl ricinoleate(OMR,with average EO degree of 10) was synthesized by reaction of methyl ricinoleate with ethylene oxide.Surface properties of OMR and the mixtures of OMR with other surfactants were determined.The results show that,γ_(CMC) of OMR is 36.78 mN/m,and due to its large molecule the CMC of OMR is 4.58×10~(-5) mol/L,lower than that of AEO_9.Mixtures of OMR and AEO_9 can be considered as ideal solutions.The surface tension isotherms of the mixtures lie between the individuals′ isotherms,and the CMC and γ_(CMC) lie between the individuals′ too.Addition of OMR can lower the CMC of SDS by nearly two orders of magnitude,but it is still larger than that of OMR.This shows that the mixtures of OMR and SDS have no strong cooperative action.However,the mixtures of OMR and CTAB have strong cooperative action,and there is lowest point on the surface tension isotherm.The smallest γ_(CMC) of the mixture is 28.24 mN/m,much less than the individuals′(γ_(CMC) of OMR and CTAB being 36.78 mN/m and 36.62 mN/m respectively).The smallest CMC of the mixture is 2.80×10~(-5) mol/L,much less than that of OMR too.