Synthesis And Performances Of Dendrimer Oligomeric Surfactants

Oligomeric surfactants are made up of two or more identical amphiphilic moieties covalently connected at the level of the head groups or very close to the head groups by a spacer group. The molecular weight of oligomeric surfactants is between that of conventional surfactants and polymer surfactants, and such surfactants fill the gap between the two. Chemical structures of oligomeric surfactants are connected with chemical bonds, rather than simple physical method. This makes close contact of amphiphilic moieties, and indeed does not destroy the hydrophilicity of polar head groups. Oligomeric surfactants have more excellent physicochemical properties than that of conventional surfactants, and thus are reputed as a new generation of surfactant. Dimeric or gemini surfactants have been by far the most investigated surfactants, but few researches concerning trimeric, tetrameric or polymeric surfactant have been reported because of the difficulty in synthesis. In this paper, two kinds of oligomeric surfactants with similar dendrimer structure were synthesized by drawing experiences from syntheses of dendrimer, and their performances were studied.1. Synthesis and performances of quaternary ammonium salt tetrameric surfactantsQuaternary ammonium salt tetrameric surfactants were prepared from ethylenediamine, epichlorohydrin and dodecyl dimethyl amine by ring-opening reaction and quaternization reaction. The resulting products have been purified with washing and recrystallizing methods, and the back titration analysis of sodium tetraphenyl boron was used to the quantitative analysis of tetrameric surfactants. Their structures were identified by ESI-MS, IR,'H NMR and Elementary Analysis.Tetrameric surfactants have excellent solubility in water, the solution of acid or base, chloroform and ethanol, but poor in nonpolar solvent such as acetone, toluene and petroleum ether, etc. The Krafft point of 4C12AC is below 0℃, and the products have good compatibility with nonionic surfactants and cationic surfactants in common use. Tetrameric surfactants have better hard water resistance, which make them possible to use in high salinity reservoirs. The surface activities of 4C12AC were determined by means of pendant drop method. The cmc andγcmc values were 0.38mmol/L,21.6mN/m, respectively. The surface activities of 4C12AC have better than DTAC with single alkyl chain and Gemini 12-2-12 with double alkyl chains.Tetrameric surfactants have excellent emulsification and solubilization performances, and are superior to conventional ionic surfactant (DTAC) with identical head group and alkyl chain. The foaming performances of 4C12AC were measured with Ross-mile method at 25℃. Tetrameric surfactants have better foaming performances, and its foaming power is around 1-2 times compared with DTAC and SDS.Tetrameric surfactants have good bactericidal properties for Esherichia coli and sulfate reducing bacteria (SRB). The disinfection rate of 4C12AC is beyond 99% for Esherichia coli, and the minimal inhibitory concentration is 30mg/L for SRB, and its bactericidal effect is superior to that of field commonly used fungicide geramine (1227). The anti-swelling performance of 4C12AC is better than that of conventional surfactant DTAC, and its anti-swelling rate is beyond 80% at 2g/L,Inhibition performance of 4C12AC for corrosion of N80 steel and A3 steel in 20% (ω) HC1 solution was investigated with weight-loss measurement, polarization curve and electrochemical impedance spectroscopy, and the results show that the tetrameric surfactants are good corrosion inhibiters. They can be spontaneously absorbed and are a type of mixed inhibitors by adsorbed film on the metal surface. Its adsorption behavior follows Langmuir adsorption isotherm. The corrosion products in simulated oilfield water are most FeCO3,Fe2(OH)2CO3 and little iron oxide.2. Synthesis and performance of sulfonate gemini surfactantsSulfonate gemini surfactants with two sulfonic groups and three alkyl chain were prepared from diethylene triamine,2-bromoethane sulfonic acid sodium salt, and acyl chloride as raw materials, and their structures were identified by IR,1H NMR and elementary analysis. Sulfonate gemini surfactants have excellent surface activities, and their surface activities excelled that of the corresponding monomeric surfactants. The synergic effect is better when mixed with DTAC, the cmc and surface tension decrease with increase of DTAC.The HLB valances of TADS were calculated according to group number method, and the valances of TADS-8 and TADS-10 are 22 and 19, respectively. TADS can remarkably decrease the contact angle of the hydrophobic surface and the hydrophilic surface and enhance its wettability to water. The foaming performances of TADS increase with increase of its concentration, and are virtually unchanged at cmc. Inorganic salts have an effect on foaming performances of TADS, and with increase of concentration of TADS, foaming performances rose at first and then reduced.