物理化学学报 >> 1987, Vol. 3 >> Issue (01): 42-47.doi: 10.3866/PKU.WHXB19870108

研究论文 上一篇    下一篇

聚醚型表面活性剂在界面上的分子取向 Ⅱ. 环氧乙烷环氧丙烷共聚多元醇在水面上的表面膜

李外郎; 张宝音; 顾惕人   

  1. 北京大学物理化学研究所
  • 收稿日期:1985-07-06 修回日期:1986-04-05 发布日期:1987-02-15

THE MOLECULAR ORIENTATION OF POLYETHER-TYPE SURFACTANTS AT THE INTERFACES Ⅱ. THE SURFACE FILMS OF POLYOXYETHYLENE-POLYOXYPROPYLENE TYPE POLYOLS AT AIR/WATER INTERFACE

Li Wailang; Zhang Baoyin; Gu Tiren   

  1. The Institute of Physical Chemist; Peking University
  • Received:1985-07-06 Revised:1986-04-05 Published:1987-02-15

摘要: 测定了水面上六种环氧乙烷环氧丙烷共聚多元醇所成表面膜的π-A关系, 其中三种是Plaronie系列ABA型嵌段共聚物(分子量在2×10~3-8×10~3之间), 三种是无规共聚的超商分于(分子量约为2×10~6)。结果表明, 在水相中有46%NaNO_3时, 成膜分子中的聚氧乙烯(EO)链将以一部分留在界面上其众部分伸入水中的方式取向;π越大, 挤入水面下的EO链节越多。聚氧丙烯(PO)链的情形也相似, 但远不如EO链那样易于挤离水面。根据这一模型, 并假定EO链和PO链的行为是相互独立的, 即可将Triton型表面活性剂和聚丙二醇的表面膜的实验结果定量地与Pluronic共聚物和超高分子无规共聚物的表面膜性质联系起来。但当基底水相中无盐时, 成膜分于的EO链极易进入水相, 而且很可能拖带一部分PO链伸进水相; 也就是说, 这时EO链和PO链的行为不再是相互独立的了, 这可以解释实验的结果。

Abstract: The film pressure vs. area curves of the surface films of three PLURONIC polyoxyethylene-polypropylene polyols (with molecular weight in the range 2×10~3- 8×10~3) , three all heteric polyoxyethylene-polypropylene polyols (with molecular weight in the range 1.5×10~6-2.5×10~6), and two polypropylene glycols (with mo- lecular weight of 2025 and 2×10~6) have been determined on a saturated sodium nitrate (46%) aqueous solution substrate. Based on the analysis of experimental data, it is proposed that the polyoxyethylene-polyoxypropylene polyols molecule orients at the air/water interface with the EO chain partialy lies in the interface and partially immerses in the water phase. The fraction of the number of EO unit lain in the interface in creases progressively with film pressure, but independent of n_(EO), the ethylene oxide chain length. The same is ture for propylene oxide (PO) chain, except the fraction of the number of PO unit lain in the interface is much smaller than that of the number of EO unit lain in the interface at the same film pressure. With this model and the assumption that the fractions of the number of EO and PO units lain in the interface are independent each other, the surface film data of PLURONIC polyols and all heteric polyoxyethylene-polyoxypropylene polyols can be related with the results of polypropylene glycols and TRITON type surfactants quantitatively. Based on the experimental data of the surface films of three all heteric polyoxyethylene-polyoxypropylene polyols on a pure water surface, it is suggested that in this case the EO chain of the molecule not only is easily soluble in water, but also trends to tring part of PO chain to penetrate the water phase.