PEO-PPO聚醚嵌段共聚物的表面活性及其在溶液界面的结构

利用和频振动光谱及表面张力测定技术对两亲性聚氧乙烯-聚氧丙烯（PEO-PPO）表面活性剂的表面活性及溶液界面结构进行了研究。结果表明：疏水PPO链段在溶液界面吸附并紧密排列是溶液表面张力降低的主要原因。增加溶液浓度、增大共聚物链内PPO与PEO聚合度比值可增加高分子链在界面的吸附，并使PPO在界面紧密排列，侧基（甲基）有序取向。另外，PPO在分子链中的位置也对这一行为产生影响，PPO位于分子链两端时的结构更有利于PPO在表面紧密堆积，降低界面高分子链间相互作用，减小溶液表面张力。

Surface Activity of Polyether Block Copolymer (PEO-PPO) and Their Structure at the Air/Solution Interface

Surface tension of polyether surfactant (PEO-PPO) with various chain structures was measured by surface tension measurement,and the local structure at the air/solution interface was investigated by the Sum Frequency Generation vibrational spectroscopy(SFG).The relationships between the locally interfacial structure and the surface activity of PEO-PPO surfactant were elucidated.The closely packing of PPO segments and well-ordered orientation of methyl group at the air/solution interface are responsible for the surface tension reduction of polymer solution.With the increasing of solution concentration and the molar ratio of PPO and PEO blocks(n_PPO/n_PEO),more PPO segments were segregated onto the surface and closely packed,and the methyl groups in PPO units orientated more orderly.Meanwhile,the copolymer with PPO block at the chain ends is easier to enrich to the surface,and thus is more efficient to reduce the surface tension.