聚苯乙烯-聚(4-乙烯基吡啶)嵌段共聚物LB膜结构形态的研究

采用氯仿作为铺展溶剂,将嵌段共聚物聚苯乙烯-聚(4-乙烯基吡啶)(PS-b-P4VP)稀溶液铺展于空气与水界面上,利用Langmuir-Blodgett(LB)膜技术转移至固体基底.研究了不同的嵌段比、表面压和小分子1-芘丁酸(PBA)的加入对嵌段共聚物气液界面聚集组装的影响.研究发现随着亲水段(P4VP)的增加,聚集组装结构由纳米片状、带状转变成纳米条状、纳米点状结构.表面压对纯PS-b-P4VP聚集组装产生影响,表面压增大,组装体排列紧密;随着表面压的继续增大,单层聚集结构遭到破坏,发生堆叠.加入PBA小分子后,PBA与PS-b-P4VP形成氢键,形态发生明显变化,原来的片状结构转变为条状或点状结构.

Studies on Morphology of Polystyrene-b-Poly(4-vinyl pyridine) Block Copolymer LB Film

The aggregation and assembly behavior of the amphiphilic block copolymer,polystyrene-bpoly(4-vinyl pyridine) (PS-b-P4VP),on water-air interface was investigated.With chloroform as the solvent,the dilute solution of PS-b-P4VP was spread on water surface.After chloroform evaporation,surface pressure-area isotherms of PS-b-P4VP at the air/water interface were drawn.Langmuir-Blodgett (LB) technique was applied to prepare films by transferring PS-b-P4VP monolayer from the air-water interface to a solid substrate.Atomic force microscopy (AFM) was used to characterize the morphologies of the films.Effect of the segment ratio of the block copolymer,surface pressure,and small molecule addition on the morphologies of the PS-b-P4VP film was studied.Three morphologies were obtained depending on the block ratio,termed planner,nanostrands and nanodots regimes.As size of the hydrophilic block (P4VP) increased,the film morphologies changed from nanoplate to nanostrands,and then to nanodots.With increasing P4VP block content,LB film thickness decreased and Langmuir isotherms moved to higher molecular areas.Understanding and controlling the compression processes of the monolayers at air-water interface is a key issue for producing determined patterns and dimensions with well-defined order.Surface pressure is another controlling factor.Based on investigations of LB films of PS-b-P4VP,morphology involved a change in packing order.Under different surface pressures,diverse morphologies of LB films were discovered by AFM.With an increase of the surface pressure,pattem density increased.Meanwhile,molecular arrangement became closer and the film thickness became much thicker.At high pressure,monolayer may collapse at the water-air interface,forming bilayer or multilayer structures,so film thickness is increased.Pyrenebutyric acid (PBA) is a fluorescent probe molecule.PBA molecules form hydrogen-bonding with P4VP between its carboxylic acid group and the pyridine ring of P4VP.After adding PBA,it is equivalent to an increase in the ratio of the hydrophilic segment P4VP,and the morphology transition of the film shows the trends like increasing the volume fraction of the hydrophilic segment.