Effect Of Selective Solvent On The Aggregation Behavior Of Block Copolymer Langmuir Monolayers

The Langmuir film balance technology and AFM were respectively used to study the aggregation behavior of the Langmuir monolayers and the structure of the LB films of amphiphilic diblock copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO, SEO) and triblock copolymer polystyrene-b-poly(ethylene oxide)-polystyrene (PS-b-PEO-b-PS, SEOS). The effects of spreading concentration, subphase temperature and solvent on the Langmuir monolayers and the LB films were studied in detail.With the increase of solution concentration, the results showed that theπ-A isotherms move to the left and the mean molecular areas decrease steply. The effect of subphase temperature mainly appeared at the isotherm plateau regions and beyond which little effect appeared. With the increase of subphase temperature, the plateau pressure increased gradually. Conditions in the amount of such substances, the collapse pressure of the Langmuir film decrease gradually. With the increase of pressure, the height of the surface micelles decrease.In addition,there existed a large effect of solvent on theπ-A isotherms of the Langmuir monolayers and the structure of the LB films of the two kinds of block copolymers. The isotherms of the monlayers spread with chloroform moves to the right of that with toluene. The spread effect of the monolayers spread with selecticve solvent toluene was not so good as that with selecticve solvent CHCl3 and the former appeared uniformly. The isotherms of the LB films of diblock copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO, SEO) and triblock copolymer polystyrene-b-poly(ethylene oxide)-polystyrene (PS-b-PEO-b-PS, SEOS) at 25oC, the results showed that theπ-A isotherms of triblock copolymer polystyrene-b-poly(ethylene oxide)-polystyrene (PS-b-PEO-b-PS, SEOS69K) move to the left and the mean molecular areas decrease. But the SEO19K is the contrary. The SEOS69K’s collapse pressure is relatively large.