Morphology And Structure Of The Mixed LB Films Of PS12K And SEOS69K

In this paper,the aggregation behavior of the mixed Langmuir monolayers and the morphology of the mixed Langmuir-Blodgett(LB)films of a hydrophobic homopolymer polystyrene(PS12K)and an amphiphilic triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene(SEOS69K)were characterized by the Langmuir monolayer technique and atomic force microscopy(AFM),respectively.Effects of temperature,blend composition,deposition pressure,and spreading solvent on the aggregation behavior of the Langmuir monolayers and the morphology of the LB films were studied.The surface pressure-area(?-A)isotherms of the mixed monolayers of PS12 K and SEOS69 K move to the left with the increase of the PS12 K content and a pseudo-plateau region occurs at about 10 mN/m when the PS12 K content is below 40 wt %.The widths of the transition plateau region become smaller and smaller with the increase of the PS12 K content.When the maximum pressure is 10 mN/m,there is no hysteresis for the mixed monolayers in the compression-expansion processes,however,when the maximum pressure reaches up to 30 mN/m,obvious hysteresis exist in all of the mixed Langmuir monolayers,and the higher the PS12 K content,the smaller the hysteresis is.When the spreading solvent is chloroform,all the mixed LB films of PS12K/SEOS69 K transferred at low pressure exhibit isolated circular micelles.Upon the further compression,the aggregates in the mixed LB films of PS12K-20 %,PS12K-40 % and PS12K-60 % become a little more dense,while those of PS12K-80% become totally close-packed which is similar to the LB films of the neat PS12 K.When the spreading solvent is toluene,the aggregates of the mixed LB films of PS12K-20 %,PS12K-40 % and PS12K-60 % transferred at different pressures all exhibit isolated circular micelles.For the PS12K-80 %,the LB film transferred at low pressure exhibits a necklace-network structure which is similar to that of PS12 K.Upon the further compression,the LB film becomes closepacked.