Study On Synthesis And Properties Of Hydrophobic Diquaternary Gemini Surfactants

Gemini surfactants had received much attention and interest, because their better physicochemical properties and utilities than conventional surfactants. But most research was only focused on the synthesis and properties of hydrophilic Gemini surfactants. In order to know how to synthesize hydrophobic Gemini surfactants and what were their properties, this work was done.Spacer-inserting was used in the synthesis of diquaternary Gemini surfactants. It was founded that, it was quaternary ammonium bromide, not diquaternary ammonium bromide obtained by the reaction of 1,2-dibromoethane or 1,3-dibromopropane with dialkylmethylamine, because of the position-hindrance of short-chain spacer group and dialkylmethylamine. But three diquaternary compounds whose spacer groups were -(CH2)4-, N,N'-dimethyl-N,N,N',N'-tetraoctyl-1,4-butane diammonium dibromide, N,N'-dimethyl-N,N,N',N'-tetradecyl-1,4-butane diammonium dibromide, N,N'-dimethyl-N,N,N',N'-tetradodecyl-1,4-butane diammonium dibromide, were synthesized by the reaction of 1,4-dibromoalkane with dialkylmethylamine. The mixture of 1,4-dibromobutane and dialkylmethylamine in the molar ratio of 1:5 in n-propanol was heated to reflux for 48h. The compounds were isolated by washing with ethyl ether, and then were recrystallized in solvent mixtures of acetone and ethyl ether. So diquaternary Gemini surfactants whose spacer groups were -(CH2)4- can be synthesized by spacer-inserting. But the great excessive dialkylmethylamine and by-product make the purification of target difficult.To quicken the speed of nucleophilic substitution, 1,6-dichlorohexane and 3-oxa-1,5-dichloropentane were converted into 1,6-diiodohexane and 3-oxa-1,5- diiodopentane in potassium iodide. And to make the product be easy of purification, the excess of amine was reduced to 50% from 150%. Then the diiodoalkane reacted with dialkylmethylamine into diquaternary ammonium iodide, and obtained three diquaternary compounds whose spacer groups were -(CH2)6-, N,N'-dimethyl- N,N,N',N'-tetraoctyl-1,6-hexane diammonium diiodide, N,N'-dimethyl-N,N,N',N'-tetradecyl-1,6-hexane diammonium diiodide, N,N'-dimethyl-N,N,N',N'-tetradodecyl -1,6-hexane diammonium diiodide. But only one diquaternary compound whose spacer group was -(CH2)2O(CH2)2-, N,N'-dimethyl-N,N,N',N'-tetradodecyl-3-oxa- pentane diammonium diiodide, was obtained under the same reaction conditions, because of the effect of spacer. So it was easier to synthesize diquaternary Gemini surfactants with longer spacer. Also spacer group had an effect on the properties of diquaternary ammonium.As a result, all the diquaternary ammonium halide had been identified to be the respected structures by chemical analysis, 1HNMR and IR. Effects of reaction temperature, the ratio of reagents, reaction time, solvent, side reaction and by-product had been discussed in detail. Research of this novel compounds was the first in domestic, and report about this study had not been founded.All the compounds were soluble in polar organic solvent, insoluble in non-polar organic solvent and water. They could induce the surface tension of glycerol and diiodomethane, were hydrophobic surfactants with good surface activity. Also their solubility and surface activity were not the same with spacer and hydrophobic group changed.