Aggregation Behavior Of Block Copolymer PS-b-PMMA At The Air/Water Interface

Langmuir monolayers and Langmuir–Blodgett (LB) films of three diblock copolymers polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA, SMMA) with the same PS block length and different PMMA block lengths have been characterized by the Langmuir film balance technique and tapping mode atomic force microscopy (AFM), respectively. The effects of spreading condition (spreading solution volume and concentration), spreading solvent and subphase temperature on the Langmuir monolayers and LB films of SMMA were studied.The results showed that surface aggregates formed spontaneously after the evaporation of the solvent. When the spreading solution volumes were different, the morphologies of the LB films were, respectively, wormlike aggregates, isolated circular micelles, mixed morphology of circular and rod aggregates with the increase of spreading concentration and transfer pressure. When the spreading solution volumes were the same, the morphologies were, respectively, wormlike aggregates, network structure, and mixed morphology of circular and rod aggregates.In addition,the effects of solvent and subphase temperature on theπ-A isotherms of Langmuir monolayers of diblock SMMA were quite apparent. At low transfer pressure, LB films spread with selective solvent C7H8 and non-selective solvent CHCl3 were noodle morphology, mixed morphology of circular and rod, and isolated circular micelles with the increase of PMMA block length. With the increase of transfer pressure, the surface aggregates of the LB films of SMMA with short PMMA block length spread with selective solvent C7H8 changed from noodle morphology to planar structure. The samples spread with CHCl3 could dispersed evenly, but the samples spread with selective solvent C7H8 was not as good as those spread with CHCl3.