十二烷基硫酸钠对溶液中聚乙二醇分子构象的影响

Effect of Sodium Dodecyl Sulfate to Molecular Size of Polyethylene Glycol in Solution

为了考察溶液中小分子与高分子的相互作用,采用粘度法研究了十二烷基硫酸钠(SDS)对溶液中聚乙二醇(PEG)分子尺寸的影响,并计算了混合溶液中PEG分子链的无扰均方末端距随SDS加入的变化。结果表明:在溶液中SDS与PEG之间形成复合物,SDS以小胶束簇的形式结合在PEG高分子链上。由于复合物上的SDS小胶束簇的电离,使得胶束簇与胶束簇之间产生静电排斥作用,从而使高分子链扩张,体系的粘度增大。当m(SDS)/m(PEG)<2.0时,PEG分子链的分子尺寸与纯PEG溶液中的PEG分子链的尺寸相比无太大差别,当m(SDS)/m(PEG)>4.09时,SDS小胶束簇在PEG分子链上吸附达到饱和以后,PEG分子链的扩张达到最大分子尺寸,不再受SDS小分子浓度增加的影响。

In order to investigate the interaction between small molecule and macromolecule in solution, the viscosimetry was used to determine the effect of sodium dodecyl sulfate (SDS) on the molecular size of polyethylene glycol (PEG) in solution. The vary of the unperturbed mean square end-to-end distance of PEG molecule with the added SDS was calculated. The results showed that a complex of SDS and PEG was formed with the binding of SDS on PEG molecular chain in a micelle form. The electrostatic repulsion existing in the ionized SDS micelles resulted in the expansion of PEG micro-molecular chains and the increase of viscosity of the SDS and PEG mixing solution. Compared with the molecular size of PEG molecular chain in PEG solution, in the SDS and PEG mixing solution, when the m(SDS)/m(PEG)4.09, the PEG molecular chain became saturated with SDS micelles, and the expansion PEG molecular chain extend to a limit size at this ratio and no longer increase with the increase of SDS concentration.