表界面化学第3章表面活性剂课件.ppt

1、第三章第三章表面活性剂表面活性剂李硕琦山东科技大学材料学院2015.4. . .3.1 Molecular structure of surfactant表面活性剂的分子结构表面活性剂的分子结构Surfactants belong to a class of compound known as amphiphiles(两亲物质).An abbreviation for surface active agents. . .3.1 Molecular structure of surfactant结构上结构上双亲物质的定义An amphiphile is a substance that comb

2、ines in the one molecule a segment that tends to water insoluble (不溶于水) and oil soluble (溶于油), i.e. hydrophobic or oleophilic, and a segment that tends to be water soluble, i.e, hydrophilic.Phospholipids have amphipathic character. . .磷脂的分子结构BEA Confidential. | 4. . .3.1 Molecular structure of surfa

3、ctantA surfactant is a compound that lowers the surface tension (降低表面张力) of a liquid, increasing the contact between the liquid and another substance. 功能上功能上表面活性剂表面活性剂的定义. . .3.1 Molecular structure of surfactantSurfactants are water-soluble amphiphiles and are strongly adsorbed at surfaces. The dri

4、ving force for this strong adsorption comes from the amphiphilc nature of the surfactant molecule.表面活性剂可在表面吸附强烈，驱动力来自于其双亲性。. . .3.1 Molecular structure of surfactantThe hydrophobic portion of the molecule can be largely located in the vapour phase out of water while the hydrophilic portion can be im

5、mersed in the water.疏水端在气相，亲水端在水相. . .3.1 Molecular structure of surfactantSuch adsorbed films are known as Gibbs monolayers (Monolayer because there is normally only one layer).这样的吸附层被称为吉布斯单分子层 . . .BEA Confidential. | 9. . .3.2 Surfactant Classification There are four classes of surfactant, define

6、d by the ionic nature of the hydrophilic moiety: anionic(阴离子型), cationic(阳离子型), non-ionic(非离子型) and zwitterionic(两性离子型).十二酸(月桂酸)钠-肥皂十二烷基苯磺酸钠盐-洗衣粉十二烷基硫酸钠. . .3.2 Surfactant Classification 溴化十六烷基三甲铵十二烷基氯化吡啶. . .3.2 Surfactant Classification 环氧乙烷类-佰草集. . .3.2 Surfactant Classification 十二烷基二甲基甜菜碱十二烷基二甲基

7、甜菜碱pH不敏感不敏感- -完美完美十二烷基丙氨酸. . .3.3 Surface tension of surfactant solutions表面活性剂溶液的表面张力表面活性剂溶液的表面张力The surface tension of a surfactant solution, when plotted against concentration, usually falls smoothly to a lower limit which it remains constant.表面活性剂溶液表面张力和浓度的变化曲线下降后保持水平. . .3.3 Surface tension of s

8、urfactant solutions表面活性剂溶液的表面张力表面活性剂溶液的表面张力The curve is nearly linear at very low concentrations and the Gibbs equation (吉布斯吸附方程) indicates that the adsorption is then proportional to the concentration.222ddaRTa a 活度，（gama）吸附量222ddaRTa 非离子型离子型. . .1.dg/da0，增加溶质的浓度使表面张力升高， 为负值，是负吸附。表面层中溶质浓度低于本体浓度。非表面

9、活性物质属于这种情况。222ddaRTa . . .3.3 Surface tension of surfactant solutionsWhen the surface tension is plotted against ln c there is a nearly linear fall just before an abrupt change to the constant value of surface tension.若以表面张力和lnc做直线，则会在表面张力突变为定值之前有一段线性的下降区域。. . .3.3 Surface tension of surfactant solu

10、tionsThe Gibbs equation shows that where the -ln c curve is linear the adsorption is constant, suggesting that the adsorption has reached a limit.Saturation adsorptioncddRTln12222ddaRTa . . .3.3 Surface tension of surfactant solutions吸附量的计算吸附量的计算Adsorption values can be calculated from such surface

11、tension data using the Gibbs equation.cddRTln12. . .3.3 Surface tension of surfactant solutions数据较少时候的两个可以的近似数据较少时候的两个可以的近似At low surfactant concentrations the slope d /d c is nearly constant, and at concentrations just below the region of constant surface tension the slope d -ln c is nealy constant

12、. . . .3.3 Surface tension of surfactant solutions吸附等温线吸附等温线Adsorption isotherms. . .3.3 Surface tension of surfactant solutions例题例题分子截面积的求取分子截面积的求取. . .3.3 Surface tension of surfactant solutions例题例题分子截面积的求取分子截面积的求取. . .3.3 Surface tension of surfactant solutions例题例题分子截面积的求取分子截面积的求取. . .3.3 Surface

13、 tension of surfactant solutions例题例题分子截面积的求取分子截面积的求取. . .3.4 Micelles (胶束胶束). . .3.4 Micelles(胶束胶束)As the surface becomes crowded with surfactant, more molecules will arrange into micelles. At some concentration the surface becomes completely loaded with surfactant and any further additions must arr

14、ange as micelles. . . .3.4 Micelles(胶束胶束)This concentration is called the Critical Micelle Concentration (CMC，临界胶束浓度，临界胶束浓度). . .A, surface tensionB, interfacial tensionC, osmotic pressure; D, equivalent conductivity;E, solubility of compounds with low or zero solubility in water. . .I- A continuous

15、 decrease in Surface and interfacial tensions with surfactants concentration until the Surface and interfacial tensions level become constant owing to crowding of surfactant molecules adsorbed at surfaces and interfaces. . . .A, surface tensionB, interfacial tensionC, osmotic pressure （渗透（渗透压压） ）D,

16、equivalent conductivityE, solubility of compounds with low or zero solubility in water. . .II- The osmotic pressure rises much more slowly with increasing surfactant concentration above than it does below the CMC because it depends on the number of dissolved particles. . . .A, surface tensionB, inte

17、rfacial tensionC, osmotic pressureD, equivalent conductivity （当量（当量电导电导） ）E, solubility of compounds with low or zero solubility in water. . .III- For ionic surfactants, the equivalent conductivity drops sharply above the CMC. Only the counterions of non-associated surfactant molecules can carry cur

18、rent. . .A, surface tensionB, interfacial tensionC, osmotic pressureD, equivalent conductivityE, solubility of compounds with low or zero solubility in water. . .IV-Solubility of many drugs are increased after CMC. . . .A, surface tensionB, interfacial tensionC, osmotic pressureD, equivalent conduct

19、ivityE, solubility of compounds with low or zero solubility in waterAll these properties can be used to determine the CMC. . . .3.4 Micelles(胶束胶束)胶束不影响溶液表面张力胶束不影响溶液表面张力. . .3.4 Micelles(胶束胶束)胶束不影响溶液表面张力胶束不影响溶液表面张力. . .3.4 Micelles(胶束胶束)胶束的结构胶束的结构Hydrophilic groups outward and hydrophilic segments in

20、side. . .3.5 Properties of surfactant solutionsKrafft point(离子型表面活性剂离子型表面活性剂)The Krafft point is the minimum temperature at which surfactants form micelles. . . .3.5 Properties of surfactant solutionsKrafft point(离子型表面活性剂离子型表面活性剂)The Krafft point is the minimum temperature at which surfactants form

21、micelles. . . .3.5 Properties of surfactant solutions你认为，如果我们需要使用胶束的话，你认为，如果我们需要使用胶束的话，Krafft point 是越是越高越好还是越低越好？高越好还是越低越好？. . . . .BEA Confidential. | 45. . .BEA Confidential. | 46. . .BEA Confidential. | 47. . .BEA Confidential. | 48. . .BEA Confidential. | 49. . .BEA Confidential. | 50. . .BEA C

22、onfidential. | 51. . . . . . . . . . .3.5 Properties of surfactant solutionsCloud point(非离子型表面活性剂非离子型表面活性剂)With non-ionic surfactants, raising the temperature decreases the solubility, due to weakening of the hydrogen bonds with water. Consequently at a certain temperature, known as the cloud point,

23、 large aggregates of surfactant separate out as a distinct phase and the liquid becomes cloudy. . .3.5 Properties of surfactant solutionsCloud point extraction. . .3.5 Properties of surfactant solutionsmicelle structure. . .3.5 Properties of surfactant solutionsmicelle structure. . .3.6 Solubilizati

24、on（增溶效果）（增溶效果）For spherical micelles in particular, the centre of the micelle is essentially a liquid hydrocarbon, and as such it is capable of dissolving some oil-soluble substances. Thus, solutions containing micelles sometimes increase the solubility of sparingly soluble substances by incorprating these molecules into the micelles, a process called solubilization. . .3.6 Solubilization. . .3.7 Application of surfactantwetting. . . . . . . . .3.7 Application of surfactantdetergent . . .表面活性剂的结构、性质特点吉布斯吸附方程胶束的结构临界胶束浓度克拉夫特点. . .