| The amphoteric surfactants can affect the interfacial properties,it has good applicability in different fields,and is relatively friendly to the environment and widely used with many excellent characteristics.In this paper,a series of amphoteric surfactants containing amide groups(b1,b2,b3,b4)were synthesized by using fatty amines with different carbon atoms,acrylamide.The surfactant b5 were synthesized by using cocamido propyl dimethyl tertiary amine(PKO),sodium dihydrogen phosphate,and epichlorohydrin(ECH)as the main raw materials,it is amphoteric in type and contains amide group in molecular structure.The structures,surface chemical properties,aggregation behavior and properties of the synthesized surfactants b1?b5 were studied experimentally.The products of a1?a4 were obtained by the reaction of octadecylamine,hexadecylamine,tetradecylamine and dodecylamine with acrylamide for 3 hours at 70 ?.The products of b1?b4 were obtained by the reaction of the products of a1?a4 in the first step with sodium chloroacetate for 5 hours at 75?.The potassium ferricyanide method was used to determine the yield of each product under the reaction conditions.The yields of b1 to b4 were 68.80%,69.41%,59.35%and 80.11%,respectively.The product a1 was purified by recrystallization with ethanol after removing the solvent.The product b1 was purified by recrystallization with petroleum ether after removing the solvent.The products a2?a4 and b2?b4 were purified by recrystallization with ethyl acetate after removing the solvent.After purification,it was characterized by FTIR and NMR.The experimental data were consistent with the expected results.The surface tension of each product was measured by the ring method.At 298.15K,The CMC of product b1 was 4.93×10-5 mol·L-1,and the ?y was 41.4 mN·m-1;The CMC of product b2 was 9.75×10-5 mol·L-1,and the y was 35.6 mN·m-1;The CMC of product b3 was 1.05×10-4 mol·L-1,and the y was 31.1 mN·m-1;The CMC of product b4 was 2.75×10-4 mol·L-1,and the ? was 30.7 mN·m-1.From the conductivity curve(k-c),it can be seen that the inflection point of the k-c curve of the products b1?b4 is not particularly obvious.And from the molar conductivity curve(?-c1/2),it can be seen that the A-c1/2 curve has a maximum value,and the maximum point appears before the CMC,which indicates that b1?b4 will form self-aggregate before reaching the critical micelle concentration in the solution.That is to say,the pre-micellarization phenomenon occurs.The thermodynamic functions of the products b1?b4 were calculated and analyzed.The results show that the process of forming micelles of the products is spontaneous,and the whole process shows an exothermic phenomenon,which is dominated by entropy.From the apparent activation energy-concentration(Ea-c)curve,it can be seen that due to the pre-micellarization phenomenon,the lowest point of the curve corresponds to the concentration of the pre-micelles,and the right side of the lowest point corresponds to the critical micelle concentration.The particle size of the micelles in the system was measured using dynamic light scattering(DLS)technology.Based on the particle size distribution,the aggregation behavior of the b1?b4 systems at different concentrations were estimated,and the distribution of micelles,vesicles and sponge-like aggregates has certain regularity at different concentrations.The effects of different hydrophobic carbon chain lengths on the emulsification properties and foaming properties of the products b1?b4 were analyzed by water separation experiment and foaming experiment.Through the emulsification and mixing experiments of product b1,it can be seen that the type of product b1 is fast cracking type.The intermediate a5 was synthesized by the reaction of sodium dihydrogen phosphate with epichlorohydrin at 85 ? for 7.5 h.The product b5 was obtained by the reaction of intermediate a5 with cocamido propyl dimethyl tertiary amine(PKO)and isopropanol as the solvent at 75 ? for 5 h.The control conditions method was used to optimize the reaction conditions in the second step of the synthesis.The optimal reaction conditions were n=1.50(n=nECH/nPKO),T=75-C,and t=5 h.The yield measured by potassium ferricyanide method can reach 86.50%at this reaction conditions.The product a5 was purified by recrystallization with methanol after removing the solvent.The product b5 was purified by recrystallization with ethyl acetate after removing the solvent.After purification,it was characterized by FTIR and 1H NMR.The experimental data were consistent with the expected results.The surface tension of the product b5 was measured by the ring method.The CMC of product b5 at 298.15 K is 5.26×10-7 mol·L-1,and the y is 32.13 mN·m-1.From the comparison of the k-c curve and the A-c1-2 curve,it can be seen that the CMC of the product b5 is completely consistent on the K-c curve and the A-c1?2 curve,indicating that b5 has no pre-micellarization.The thermodynamic function of product b5 is calculated and analyzed.The results show that the process of forming micelles of the product is spontaneous,and the whole process shows an exothermic phenomenon,which is dominated by entropy.The Ea-c curve shows that the lowest point of the curve corresponds to the critical micelle concentration.The particle size of the micelles in the system was measured using DLS technology.Based on the particle size distribution,the aggregation behavior of the b5 systems at different concentrations was estimated.The distribution of micelles,vesicles and sponge-like aggregates has a certain regularity at different concentrations.It can be known from the water separation experiment that the consumption time for the b5 system to separate 10 mL of water is 330 s,indicating that the emulsification performance is good.It can be known from the foaming experiment that the initial foaming height of the b5 system can reach 58 units,and it can still reach 55 units after 5 minutes,which indicates that b5 has good foaming property and foaming stability.Through emulsification and mixing experiments of b5,it can be seen that the type of product b5 is fast cracking. |
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