Synthesis And Properties Of Imide-based Carboxylate Surfactants

The imide-based carboxylate surfactants possess advantages of convenient synthetic procedure,strong design of molecules,excellent comprehensive performance.In recent years,the development of new products of such surfactants has been studied prosperously both at home and abroad.In this paper,eight kinds of imide-based carboxylate surfactants（SMM-n and SMI-n,n=12,14,16,18）were synthesized by amidation,imidization and neutralization with maleic anhydride（MAH）,itaconic anhydride（IAn）,long chain amines（dodecylamine,tetradecylamine,cetylamine,octadecylamine）and sodium hydroxide as raw materials.The optimal reaction condition of the synthesis of SMM-n and SMI-n was obtained via single factor experiments and orthogonal experiment.Thus,it was carried out with n（MAH/IAn）:n（M-n）=1.20:1 at 35℃for 35 min.The structures of the intermediates（maleamic acids,M-n）and the desired compounds（SMM-n and SMI-n）were confirmed by FT-IR,¹H NMR and elemental analysis.The physicochemical properties of the surfactants were studied,including critical micelle concentration（CMC）,minimum surface tension(γ_CMC),Krafft point,solubilization ability,lime soap dispersing power,emulsifying property,foam property and wettability.The results were as follows:（1）SMM-n and SMI-n possessed good ability of reducing the surface tension of water.Theγ_CMC of SMM-12 and SMI-18 was 27.72 mN/m and 30.70 mN/m,respectively.The surfactants formed micelles in solution easily,and the hydrocarbon chain was the driving force of micellization and adsorption.（2）The Krafft points of SMM-n and SMI-n increased with the increase of alkyl carbon number.SMM-12 and SMI-12 had lower Krafft points of<0℃,which meant they were used in extensive range.SMM-18 and SMI-18 had higher Krafft points of80.2℃and 83.5℃,respectively,which meant they were suitable for high temperature environment.（3）SMI-n performed better than SMM-n in solubilization property,emulsifying power and wetting property.SMM-n was better than SMI-n on lime soap dispersing power.As for the foaming power,SMM-n lathered more than SMI-n,but the foams were less stabler than that of SMI-n.（4）The effect of inorganic salts on CMC of SMI-n was investigated through the CMC results of SMI-n by changing the concentration of NaCl,type of cations（Na⁺、Li⁺、K⁺）and type of anions（F^-、Cl^-、Br^-）.The results showed that SMI-n resisted salt to a certain extent.The effect of cations on CMC of SMI-n was Li⁺>K⁺>Na⁺,and the effect of anions was F^->Cl^->Br^-.