第24卷第2期化學(xué)研究與應(yīng)用 Vol.24, No.22012年2月 Chemical Research and Application Feb.,2012文章編號(hào):1004-1656(2012)020322-05乙二醇對(duì)烷基三甲基溴化銨膠團(tuán)化行為的影響凌錦龍,徐敏虹,洪迪,張艷(湖州師范學(xué)院生命科學(xué)學(xué)院,浙江湖州313000)摘要:利用電導(dǎo)法研究了烷基三甲基溴化銨表面活性劑(CTAB,n=12,14,16),即十二烷基三甲基溴化銨(TAB),十四烷基三甲基溴化銨(TTAB)和十六烷基三甲基溴化銨(CTAB),在混合極性溶劑乙二醇/水(體積分?jǐn)?shù)0~40%)中的膠團(tuán)化行為?？疾炝藴囟葘?duì)膠團(tuán)形成的影響,應(yīng)用相分離模型估算了三個(gè)表面活性劑的膠團(tuán)熱力學(xué)參數(shù)。結(jié)果表明臨界膠團(tuán)濃度(cmc)和反離子解離度(a)都隨乙二醇組分的增加而增大。在乙二醇/水混合溶劑中膠團(tuán)形成的標(biāo)準(zhǔn)吉布斯自由能相差很小混合焓都是負(fù)值而混合都為正值說明補(bǔ)償效應(yīng)在膠團(tuán)形成中起主導(dǎo)作用。關(guān)鍵詞:烷基三甲基溴化銨;乙二醇/水混合溶劑臨界膠團(tuán)濃度;膠團(tuán)熱力學(xué)中圖分類號(hào):0647.2文獻(xiàn)標(biāo)識(shí)碼:A Effect of ethylene glycol on the micellization behavior of alkyltrimethylammonium bromides LING Jin-long', XU Min-hong, HONG Di, ZHANG Yan Abstract: The micellization behavior of alky um bromide( DTAB, TAB and CTAB, respectively) in ethylene glycol(EG) and water mixtures with varying volume fraction of EG (/)has been investigated employing electrical conductivity. Temperature dependence of the critical micelle concentration() was also studied to understand the micellar thermodynamics of these systems. The pha odel of micellar formation was applied to obtain the ther of micellization. It is showed that the cmc and the degree of counterion dissociation (a) increase with increasing content of EG in mixed solvent. all differences in the standard molar Gibba free energies of micellization over the temper ated. The enthalpy of micellization is negative in all cases, whereas the entropy is al- ways positive. This behavior indicates that an enthalpy-entropy compensation effect is the governing factor for micellization. Key words alkyltrimethylammonium bromide; EG and water binary mixture; critical micelle concentration; micellar thermodynamic在混合溶劑中研究表面活性劑的熱力學(xué)性途徑:1)與表面活性劑分子的相互作用,2)改變?nèi)苜|(zhì),有助于理解溶質(zhì)溶質(zhì)和溶質(zhì)溶劑的相互作劑的特性。改變?nèi)芤罕倔w相性質(zhì)最方便的辦法就用。表面活性劑膠束性質(zhì)主要由復(fù)雜的親水是添加有機(jī)溶劑。有機(jī)溶劑主要進(jìn)入本體相而不和僧水間平衡所決定。而溶劑因素的影響有兩條參與膠團(tuán)的形成,這些有機(jī)添加劑通常要求具有收稿日期:2010-11-28修回日期:2011-10-27聯(lián)系人簡(jiǎn)介:凌錦龍(1964-),男,副教授,主要從事溶液熱力學(xué)和界面化學(xué)研究-mail: lingjinlong hute.c第2期凌錦龍等:乙二醇對(duì)烷基三甲基溴化銨膠團(tuán)化行為的影響323很高的內(nèi)聚能和介電常數(shù),以及較高的氫鍵形成40%的水溶液中的電導(dǎo)率;在20%E溶液中,測(cè)能力。二元醇具有兩個(gè)羥基,既能形成分子內(nèi)氫定了三種表面活性劑在298.15K~318.15K時(shí)的鍵,也能與水形成氫鍵而構(gòu)成三維網(wǎng)狀結(jié)構(gòu)。其電導(dǎo)率。圖1是298.15K時(shí)CTAB電導(dǎo)率隨EG對(duì)表面活性劑膠團(tuán)形成的影響,已引起基礎(chǔ)研究濃度的變化關(guān)系(其他未列出)?？梢钥闯?電導(dǎo)者的廣泛興趣 PalepuTriton6等研究了率在膠團(tuán)形成前后有一個(gè)突變,兩條直線的交點(diǎn)100在二元醇(乙二醇,三甘醇,四甘醇)水溶液中即為cmc,而膠團(tuán)形成之后的直線斜率與之前的直的自聚行為及膠團(tuán)熱力學(xué)性質(zhì)。 Eastoe等研究線斜率之比即為反離子解離度a表1和表2列了在水乙二醇和水-1,3丙二醇混合溶劑中表面出了三種表面活性劑的cmc和反離子解離度a活性劑頭基對(duì)聚集行為的影響。這些研究指出了125非離子或離子表面活性劑在有二元醇存在時(shí)的不1同的膠團(tuán)行為,說明了本體相在膠團(tuán)形成過程中 EG(v/v]的重要性,揭示了通過改變本體相性質(zhì)來(lái)控制膠20%團(tuán)聚集的可能性本文選擇不同疏水鏈長(zhǎng)的烷基三甲基溴化銨(CTAB,n=12,14,16),研究了在不同乙二醇含量水溶液中的膠團(tuán)化行為,分析了溫度對(duì)膠團(tuán)形成圖1298.15K時(shí)不同體積分?jǐn)?shù)的乙二醇水溶液中的影響,探討了極性有機(jī)溶劑的加入對(duì)膠團(tuán)形成CTAB電導(dǎo)率隨濃度變化關(guān)系的影響規(guī)律。 Fig 1 Conductivity versus concentration of CTAB in EG+H2O mixtures at 298. 15K1實(shí)驗(yàn)部分由表1可以看到,cmc隨EG的增加而增加。.1試劑這主要由兩個(gè)因素引起:1)EG的加入,降低了本十二烷基三甲基溴化銨(DTAB),十四烷基三體相的內(nèi)聚能密度,因而增加了表面活性劑單體甲基溴化銨(TTAB),十六烷基三甲基溴化銨的溶解性,使cmc升高;2)助溶劑引起水的介電常(CTAB),AR,用丙酮-乙醚混合溶劑重結(jié)晶5次;數(shù)下,導(dǎo)致離子頭基間的相互斥力增加,使cm乙二醇(EG),AR;水為去離子水經(jīng)石英亞沸重蒸升高。處理,電導(dǎo)率為1.0us·cm-1。所用試劑經(jīng)測(cè)定表溫度對(duì)臨界膠團(tuán)濃度的影響,可以從表2看面張力曲線均無(wú)最低點(diǎn),表明無(wú)高活性雜質(zhì)存在。出。固定溶劑比例時(shí),表面活性劑的cmc隨溫1.2電導(dǎo)實(shí)驗(yàn)度升高而升高。這里存在兩個(gè)對(duì)立的影響因素:DDS-11A型電導(dǎo)率儀,上海精密科學(xué)儀器有1)升高溫度,表面活性劑親水基團(tuán)的水合能力下限公司雷磁儀器廠。電導(dǎo)測(cè)定在帶有恒溫水夾套降,這有助于膠團(tuán)的形成;2)升高溫度同時(shí)也導(dǎo)致的容器中進(jìn)行。溫度控制精度為±0.1K。測(cè)得表面活性劑疏水基周圍水結(jié)構(gòu)的破壞,這不利于298.15K時(shí)水中CTAB臨界膠束濃度(cmc)9.3×膠團(tuán)形成。從結(jié)果來(lái)看,第二個(gè)因素起了主導(dǎo)作10mol-,與文獻(xiàn)值相符。用。同時(shí)由表1和表2看出,對(duì)膠團(tuán)溶液的反離2結(jié)果與討論子解離度a,增加EG含量與升高溫度的效應(yīng)是一致的都是增大。部分原因可能由于膠團(tuán)聚集數(shù)2.1臨界膠團(tuán)濃度cmc下降從而導(dǎo)致膠團(tuán)表面電荷密度下降而造成測(cè)定了298.15K時(shí)DTAB,TTAB和CTAB在的乙二醇體積分?jǐn)?shù)分別為0%,10%,20%,30%和324化學(xué)研究與應(yīng)用第24卷表1298.15K時(shí)烷基三甲基溴化銨在乙二醇水溶液中的cmca,C和△C Table The cme, degree of counterion dissociation( a), Gibbs energy of micellization( G. and Gibbs energy of transfer( for alkyltrimethylammonium bromides in EG aqueous solution at 298.15 K PEd/%cmc/10-3mol·l--ckmol△kmol DTAB014.540.25335.721016.910.26034.920.792019.010.28134.001.713022.380.32032.553.164028.490.38530.325.39 TTAB03.810.24141.80104.190.25241.130.67204.650.26540.371.43306.080.28738.723.08408.860.31636.495.30 CTAB0.930.25547.5711.180.26746.221.35201.390.27045.442.13301.890.28143.843.73402.960.30541.346.23表2不同溫度下烷基三甲基溴化銨在20%E水溶液中的cmca及膠團(tuán)熱力學(xué)參數(shù) Table 2 The emc, degree of counterion dissociation( a) and thermodynamic parameters of micellization for alkyltrimethylammonium bromides in 20%EG aqueous solution at various temperatures T/Kcmc/10-3mol·l- -AC/.mol"-AH/. mol-" TAS/. mol- DTAB298.1519.010.28134.0019.4414.57303.1520.440.30633.7619.8013.96308.1522.060.33033.5120.173.33313.1523.850.35433.2320.5312.69318.1525.800.37932.9120.8712.04298.154.650.26540.3829.8810.50303.155.150.27640.3530.699.66308.155.770.28740.2531.518.74313.156.520.29840.1032.337.77318.157.400.31239.8433.106.74 CTAB298.151.390.27045.4430.0515.39303.151.560.27845.4830.9214.57308.151.750.28745.4931.7813.7113.151.980.29545.4632.6712.80318.152.220.30345.4633.5611.92.2膠團(tuán)熱力學(xué) Gibbs自由能△,混合△及混合熵△由相分離模型可得到膠團(tuán)形成的標(biāo)準(zhǔn)摩爾△=(2-a)RTInX(1)第2期凌錦龍等:乙二醇對(duì)烷基三甲基溴化銨膠團(tuán)化行為的影響325△H=-(2-a)()(2)基從本體相向膠團(tuán)的遷移更為困難?！鰿越大, aTcmc也越高。表2數(shù)據(jù)表明,在同一EG濃度下,混合自由 TAS=AH-AG(3)能隨溫度的變化很小,幾乎不變.隨烷基鏈碳原式中a是反離子解離度,是用摩爾分?jǐn)?shù)表示子數(shù)目的增加,變得更負(fù),即膠團(tuán)形成的自發(fā)的cmc濃度。從cmc隨溫度的變化關(guān)系可以求出性增大,所以相應(yīng)的cmc也降低。膠團(tuán)混合都△H。圖2為各表面活性劑nXm隨溫度的變化是負(fù)值,隨溫度增加而降低,混合熵都是正值,也關(guān)系,均為線性關(guān)系,這與文獻(xiàn)2的結(jié)論一致。隨溫度增加而降低。這說明了在20%EG水溶液為考察共溶劑對(duì)膠團(tuán)化過程的影響,引入了中,烷基三甲基溴化銨的膠團(tuán)化行為并不是熵驅(qū)遷移自由能△G動(dòng),而是熵補(bǔ)償效應(yīng)的結(jié)果。 Callaghan在研究EG水溶液中溴代十六烷基吡啶聚集行為時(shí),認(rèn) DTAR為在高濃度的EG水溶液中(富醇區(qū)),隨溫度升 TTAR -CTAE高混合△H變小,而變△S從正變?yōu)樨?fù),因此△H是膠團(tuán)形成的驅(qū)動(dòng)力。Ruiz研究了在20%(wt)EG水溶液中(富水區(qū)),認(rèn)為膠團(tuán)化過程仍然是在與水結(jié)構(gòu)性質(zhì)類似的環(huán)境中進(jìn)行的,EG的加295300305310315320入僅僅產(chǎn)生很小的溶質(zhì)溶劑相互作用,膠團(tuán)形成 T/K圖2在20%E水溶液中烷基三甲基澳化主要是焓熵補(bǔ)償效應(yīng)。Lee2在研究EG水溶液ln隨溫度的變化關(guān)系中SDS的聚集行為時(shí)也有相似的結(jié)論。溫度的升 Fig Plot of InX versus temperature for高,主要是弱化了氫鍵形成能力和液體的結(jié)構(gòu)化, alkyltrimethylammonium bromides in 20% EG aqueous solution導(dǎo)致溶液的極性降低,疏溶劑作用減弱,使表面活性劑離子頭基間的斥力增加,延緩膠團(tuán)的形成,△=(ec+2-2(4)cmc增大。計(jì)算結(jié)果一并列于表1和表2中。由表1的膠團(tuán)熱力學(xué)參數(shù)來(lái)看,C都為負(fù)3結(jié)論值,說明膠團(tuán)的形成是自發(fā)的。隨EG濃度的增加,△C也呈增加趨勢(shì),因此EG的加入不利于膠烷基三甲基溴化銨的cmc和反離子解離度a團(tuán)的形成。膠團(tuán)cmc隨本體相組成的變化原則上都隨混合溶劑中EG濃度的增加而增大。升高溫由遷移自由能△G決定,從水到乙二醇+水混合度的影響與添加乙二醇的效應(yīng)一致。在EG水溶物的遷移自由能的大小取決于水、有機(jī)溶劑以及液中,膠團(tuán)形成的驅(qū)動(dòng)力是熵補(bǔ)償效應(yīng)。隨著水有機(jī)溶劑的相互作用都是正值,是溫度升高,混合溶液極性降低,疏水作用減弱,延因?yàn)镋G的加入,導(dǎo)致疏水鏈溶解性增大,致使尾緩膠團(tuán)形成。參考文獻(xiàn): [1 Binana-Limbele W, Zana R. Electrical conductivity study kinetic investigation J]. J Solution Chem, 2008,37(1): of the self-association of ionic surfactants in solution in 59-72 ethyleneglycol, formic acid and formamide J ] Collid [3] Ray A. Micelle formation in pure ethylene glycol[ J]. J Am Polym Sci,1989,267(5):440447. Chem Soc,1969,91(23):6511-6512. [2]Kolay S, Ghooh K K, Mac Donald, et al. Micellization of [4]Gracie, Tumer D, Palepu R. Therrmodynamic properties alkyltriphenylphosphonium bromides in ethylene glycol of micellization of sodium dodecyl sulfate in binary mix- and diethylene glycol+water mixtures thermodynamic and tures of ethylene glycol with water[ J]. Can J Chem, 1996,326化學(xué)研究與應(yīng)用第24卷74(9):1616-1625. arnitine chlorides in ethylene glycol J]. J Chem Soc,5]葉錫麟,李玉書,胡秀杰 Triton X--100在乙二醇中的膠 Faraday Trans1,1981,77:2907-2912體性質(zhì)[]物理化學(xué)學(xué)報(bào),1994,10(5):456460[15]凌錦龍,計(jì)兵,莫勤華,等 Triton X-100/CTAB在乙二 [6]Moore S A, Glenn M, MacDonald M, et al. Micellar醇/水混合溶劑中的熱力學(xué)性質(zhì)和膠團(tuán)化行為[J]物 and associated thermodynamic properties of binary mix-理化學(xué)學(xué)報(bào),2009,25(7):1297-1302. tures of alky] triphenyl phosphonium bromides in ethylene [16]Palepu, Charibi, Bloor D M, et al. Electrochemical glycol and water mixtures]. Colloid Polym Sci, 2007, studies associated with the micellization of cationic sur-285(5):543-552. factants in aqueous mixtures of ethylene glycol and glyc- []Ruiz C C, Molina-Bolivair J, Aguiar J, et al. Effect oferol[]. Langmuir,1993,9(1)110-112 ethylene glycol on the thermodynamic and micellar proper-[] Eastoe J, Nave S, Downer A, et al. Adsorption of ionic ties of Tween 20[]. Colloid Polym Sai, 2003,281(6): surfactants at the air-solution interface]. Langmuir,531-541.2000,16(10):45114518 [8] Huang J, Zhu B Y, Zhao G X. Vesicle formation of a 1 [18] Rodriguez A, Graciani MM, Fernandez G, et al. Effects of catanionic surfactant mixture in ethanol solution[ J]. Lang- glycols on the thermodynamic and micellar properties ofmuir,1997,13(21):5759-5761 TTAB in water]. J Colloid Interface Sci, 2009, 3389]黃建濱,何萍,何煦,等甲酰胺與正負(fù)離子表面活性劑(1):207-215.有序溶液的研究[J]物理化學(xué)學(xué)報(bào),1998,14(12):19] Ruiz CC. Thermodynamics of micellization of tetradecylt1080-1087. rimethylammonium bromide in ethylene glycol-water bi-[10]黃建濱,韓峰,吳濤非水溶劑中囊泡等分子有序組合 nary mixtures[ J]. Colloid Polym Sci, 1999,277(7) 701-體的形成[]物理化學(xué)學(xué)報(bào),2003,19(8):779-784707.[11]asc,dasb. Thermodynamic and interfacial adsorption[20]趙國(guó)璽表面活性劑物理化學(xué)[M],北京:北京大學(xué)出 studies on the micellar solutions of alkyltrimethylammoni-版社,1991:231-250. um bromides in ethylene glycol()-water(2) mixed sol [21] Rodriguez A, Graciani M M, Moya M. Effects of addi- vent media[]. J Chem Eng Data, 2009 54 (2) 559. tion of polar organic solvents on micellization )] Lang-565.muir,2008,24(22):12785-12792. 12] Hussain, Tan B H, Gudipati CS, et al. Micelle forma- [22]Callaghan A, Doyle R,, Alexander E, et al. Thermodynam- tion of amphiphilic e-b-poly N-vinylpyrroli- ic properties of micellization and adsorption and electro- done)diblock copolymer in methanol and water-methanol chemical studies of hex n bromide in bina- binary mixtures]. Langmuir, 2009, 25 (10) 5557- ry mixtures of 1, 2-ethanediol with water[]. Langmuir,55641993,9(12):3422-3426 13 Ruiz CC, Molina-Bolivair J A, Aguiar, et al. Thermody- 23 ]Lee D J, Huang W H. Enthalpy-entropy compensation in namic and structural studies of Triton X-100 micelles in micellization of sodium dodecyl sulphate in water/metha- ethylene-water mixed solvents]. Langmuir, 2001,17 nol, water/ethylene glycol and water/ glycerol binary mix-(22):6831-6840. tures J]. Colloid Polym Sci, 1996, 274 (2) 160-165 14 Ionescu L G. Fung D S. Formation of micelles of acyle-(責(zé)任編輯童冬梅)