长链N-烷基-3-甲基吡啶溴盐表面活性剂合成及性能

Synthesis and Properties of Surfactants:Long-Chain N-Alkyl-3-Methylpyridinium Bromide

以3-甲基吡啶和正溴代烷为原料合成了3种长链N-烷基-3-甲基吡啶溴盐离子液体表面活性剂[Cnmpy][Br](n为疏水尾链所含碳原子个数,n=12、14、16)。采用FTIR和NMR(1H、13C)对化合物结构进行了表征。采用电导率法和Du Noüy环法测定了表面活性剂的临界胶束浓度(CMC),考察了疏水基链长、温度对CMC的影响,并计算了胶束形成过程的热力学参数;测定了所合成表面活性剂对金黄色葡萄球菌、大肠杆菌和枯草芽孢杆菌的抑菌活性。结果表明,298.15K时,电导率法测得[Cnmpy][Br](n=12、14、16)的CMC分别为9.98、2.50和0.564 mmol/L;Du Noüy环法较电导率法测得的CMC小1.15～1.37倍。疏水基尾链碳原子数对CMC的影响符合Stauff-Klevens公式。CMC随着温度的升高,呈现先降低后升高的趋势。[Cnmpy][Br]表面活性剂的标准胶束吉布斯自由能和标准胶束化焓均为负值,表明胶束的形成是自发放热过程。抑菌活性实验结果表明,[C14mpy][Br]对3个菌种的抑菌活性最强,抑菌圈直径分别为25.0、28.0和26.0 mm。

Three long-chain ionic liquids surfactants: N-alkyl-3-methylpyridinium bromide [Cnmpy][Br](n is the number of carbon atoms in hydrophobic tail, n=12, 14, 16) were synthesized from 3-methylpyridine with n-alkyl bromides and characterized by FTIR and NMR(1 H, 13 C). The critical micelle concentration(CMC) values of surfactants were determined by employing conductometry and Du Noüy ring method. The effects of carbon chain length in hydrophobic tail and temperature on the CMC were also investigated. The thermodynamic parameters of the micellization process of the surfactants were also calculated. The antibacterial activities of the synthesized surfactants against Staphylococcus aureus, Escherichia coli and Bacillus subtilis were measured. The results showed that the CMC values for [Cnmpy][Br](n=12, 14, 16)was found to be 9.98, 2.50 and 0.564 mmol/L, respectively. The CMC value measured by Du Noüy ring method were 1.15 to 1.37 times lower than that by conductometry. The relationship between the number of carbon atoms in carbon atoms in hydrophobic tail and the CMC value was in accordance with StauffKlevens rule. The CMC values initially decreased and finally increased with the increase of temperature.The ΔGm and ΔHm values of [Cnmpy][Br] surfactants were negative, indicating that the micellization process was a spontaneous exothermic process. The results of antibacterial activities showed that[C14 mpy][Br] surfactant had the strongest antibacterial activity against the three bacteria. The inhibition zone diameters were 25.0, 28.0 and 26.0 mm, respectively.