论文标题:聚乙二醇与十二烷基硫酸钠的相互作用的研究
The Interaction of Poly (Ethylene Glycol) and Sodium Dodecyl Sulfate
论文作者 杨晓明
论文导师 吴大诚,论文学位 硕士,论文专业 材料学
论文单位 四川大学,点击次数 99,论文页数 55页File Size1888k
2003-03-01论文网 http://www.lw23.com/lunwen_151162322/ 聚乙二醇;十二烷基硫酸钠;表面张力;分子尺寸;单分子膜
Polyethylene glycol;Sodium dodecyl sulfate;Surface tension;Molecular size;Monolayer
本文研究了中性高分子聚乙二醇(PEG)与阴离子表面活性剂(SDS)在溶液中的相互作用。本文通过表面张力，电导，粘度等方法研究了PEG与SDS在溶液中的的相互作用。结果表明：当SDS的浓度较低时，PEG与SDS之间无相互作用，随着SDS浓度的增加，SDS开始以预胶束的形式结合到PEG上与PEG产生相互作用，定义这一点的浓度为临界结合浓度(CAC)，CAC的确定可由表面张力，电导，粘度对SDS浓度曲线的第一个转折点来确定。当SDS的浓度继续增加到C_2时，SDS在高分子链吸附达到饱和后SDS自由胶束开始形成。在C_2点以后，溶液中SDS单体，SDS自由胶束，PEG-SDS复合物三者共存。PEG—SDS复合物较公认的模型为：PEG分子链缠绕在SDS预胶束的界面上，并且穿透到SDS预胶束的极性区，但不穿过SDS胶束的疏水部分。 由混合溶液的表面张力可知，在CAC点之前混合溶液的表面张力低于相同浓度时纯SDS溶液的表面张力，因此可以推测SDS与PEG都吸附到水溶液的表面上；CAC点到C_2点之间增加的SDS全部以预胶束的形式结合到PEG分子链上，不再吸附到溶液表面，因此混合溶液的表面张力对SDS浓度的曲线出现一个平台，同时PEG逐渐从气液界面向溶液内部转移直到气液界面只剩SDS。C_2点以后，由于PEG已被SDS吸附饱和因此加入的SDS不再吸附到PEG分子链上而继续吸附到气液界面，因此混合溶液的表面张力又开始下降直到与CMC点以后纯SDS溶液的表面张力一致。利用吉布斯吸附方程计算了两种溶质在气-液界面的吸附量，结果表明混合溶液的气液界面即有PEG又有SDS，进一步研究PEG与SDS在表面相中的相互作用研究表明PEG与SDS在气液界面有相互作用且PEG的分子量越大相互作用越强。 摘要 PEG与SDS之间的相互作用使得小分子SDS对PEG大分子在溶液中的分子尺寸产生了影响。这种影响可以通过溶液的粘度和电导率来研究。特性粘数的确定采用了两种方法，最终采用了接合点理论所确定的特性粘数数据来计算大分子的均方末端距，研究结果表明，在CAC点之前，高分子的均方末端距与未加入小分子时的均方末端距一样。在以C与C2点之间由于SDS以预胶束的形式接合到PEG分子链上，SDS胶束之间的静电斥力使得分子链的均方末端距增加。当PEG分子链吸附达到饱和以后，均方末端距的扩张达到一个最大值。电导率的研究表明:吸附到PEG分子链上的预胶束的电离度较SDS自由胶束的电离度大，因此可以推测预胶束的聚集数较SDS自由胶束的聚集数小。 研究了PEG在不同底液的气/液界面的单分子铺展膜的二/rs曲线。结果表明，底液的性质对膜的可压缩性有一定的影响，且PEG在气/液界面上铺展膜的平衡表面压及特性标度指数v受亚相溶液热力学性质的影响。
The interaction between polyethylene glycol (PEG) and sodium dodecyl sulfate (SDS) was investigated in this paper. The association between nonionic polymer (PEG) with anionic surfactant (SDS) has been verified by a variety of techniques. With increasing surfactant concentration, no interaction between the polymer and the surfactant is detected until a critical aggregation concentration, known as the CAC (Critical Association Concentration) is reached. It has to be noted that the CAC can be detected by a variety of techniques such as surface tension, conductivity and viscosity. The CAC is usually lower than the normal CMC in the absence of polymer. This is a clear indication of interaction between polymer and surfactant. Above the CAC, surfactant form aggregates bound to polymer. The polymer chains become saturated with surfactant aggregates at a concentration C2, above which polymer-surfactant complexes coexist with free micelles. The exact nature of the interaction between PEG and SDS is concluded that the PEG chain is wrapped around the SDS micelle with some of the segments of PEO adsorbed at the hydrocarbon/water interface, while most of them form loops in the surrounding water. The PEG residues interact with the hydrated methylene group and with polar groups of the SDS but do not penetrate the hydrocarbon core.The surface tension method was applied to a mixture of a highly surface active species, the surfactant, and a feebly surface of active species, the polymer, because of the simplicity of this method. We can see from the surface tension data that at lowpolymer concentration, SDS may interact with PEG, which leads to a decrease in surfactant monomer concentration; however, at high PEG concentration, the surface tension remained unchanged, so the surfactant monomer concentration remains constant, and the polymer does no absorb significantly on the surface. There are two possible causes for the disappearance of PEG: either it is forced off the surface by the high surface pressure of the surfactant and/or it is lost by the complexation with the surfactant.The effect of SDS on the molecular size of PEG in aqueous solutions has been studied experimentally by determining their viscosity and conductivity. The plots of conductivity vs. concentration for SDS-PEG aqueous solutions show two transition points, which correspond to the beginning of the complex formation (CAC) and the beginning of the surfactant micelles formation (CMC), respectively. It was found that before CAC, the unperturbed mean square end-to-end distance of the PEG in SDS aqueous solutions was the same as that of in water. In the range between CAC and CMC, an increase of end-to-end distance was observed with increasing the concentration of SDS. When concentration of SDS was larger than its CMC, the expansion of PEG chain reached a maximum. The conclusion from the experimental part is that molecular complexes are formed form PEG chains and charged SDS micelles, which make the chains expand and increase the viscosity of solution.At last, the PEG monolayer was studied. Surface pressure data lead to the conclusion that the spread polymer is in a thermodynamically favorable environment on pure water and with NaCl was added which becomes worse as DMF was added the aqueous sub-phase.
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