X型与线型嵌段聚醚在空气/水和正庚烷/水界面上聚集行为的比较研究

Comparative Study on the Aggregation Behaviors of X-Shaped and Linear Block Polyethers at the Air/Water and n-Heptane/Water Interfaces

通过阴离子聚合方法合成了环氧乙烷(EO)含量和分子量均相同的线型聚氧丙烯(PEO)-聚氧乙烯(PPO)(LPE)和X型聚氧丙烯-聚氧乙烯(TPE)嵌段聚醚,考察了它们在空气/水及正庚烷/水界面上聚集行为的差异.界面活性的研究结果表明,TPE降低水、正庚烷界面张力的效率和效能均低于LPE的.聚醚分子在正庚烷/水界面达到吸附平衡的时间比在空气/水表面短.由于正庚烷分子插入到聚醚吸附层中,聚醚分子可以在正庚烷/水界面上采取更为直立的状态,因此聚醚分子在正庚烷/水界面扩散较快.聚醚在正庚烷/水界面的扩张弹性高于空气/水表面的.

Linear block polyethers, i.e., poly（ethylene oxide） （PEO）-poly（propylene oxide） （PPO）-PEO （LPE）, and X-shaped block polyethers, i.e., PEO-PPO-PEO （TPE）, with same EO/PO ratios and molecular masses were synthesized by anionic polymerization. The aggregation behaviors at air/water and n-hep- tane/water interfaces were systematically studied. The results show that LPE is more efficient at decreas- ing the surface tension of water and n-heptane than TPE is. The dynamic interfacial tension curves indicate that the lag-time of the adsorption of the block polyethers at the n-heptanelwater interface is smaller than that at the air/water surface, implying that immersion of the PO groups in the oil phase is more energetically favorable than immersion in the air phase. The oil molecules can insert into the adsorption layer, and hydro- phobic interactions between oil molecules and PO moieties lead to a relatively ordered arrangement of ad- sorbed polyether molecules. At the n-heptane/water interface, diffusion of the block polyethers is faster than that at the air/water surface. The dilatational elasticity at the n-heptane/water interface is much higher than that at the air/water surface.