Morphology And Structure Of The Mixed LB Films Of SMMA34K And SMMA51K

In this paper,the Langmuir film balance technology and atomic force microscopy(AFM)were mainly used to characterize the Langmuir monolayers and the LB films of two kinds of polystyrene-block-poly(methyl methaceylate)(PS-b-PMMA,recorded as SMMA34 K and SMMA51K)and their blends,respectively.Effects of blend composition,deposition pressure,spreading method of solutions,and spreading solvent et al.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 SMMA34 K and SMMA51 K move to the left with the increase of the SMMA34 K content.From the hysteresis curves of SMMA34 K,SMMA51K,SMMA34K-20% and SMMA34K-80%,it can be seen that there are no hysteresis for the monolayers when the maximum pressure is 10 m N/m,but obvious hysteresis are observed when the maximum pressure is 30 m N/m.Furthermore,the final pressures after the compression-expansion process of all the Langmuir monolayers,no matter spread with nonselective solvent chloroform or selective solvent toluene,are higher than their corresponding initial values except that of SMMA34K-20% spread with chloroform is close to its initial value.All the LB films of SMMA34K-20%,SMMA34K-40% and SMMA51 K prepared with spreading solvent chloroform exhibit the isolated circular micelle structures.However,the mixed structures of circular and rod-like micelles are observed in the LB films of SMMA34K-60%,SMMA34K-80% and SMMA34 K.With the increase of transfer pressure,the average dimension of the micelles in the mixed LB films decreases resulting from the crack of the close-packed large micelles.When the spreading solvent is toluene,the LB films of SMMA34K-20%,and SMMA34 K transferred under low pressure exhibit isolated circular micelles,but the LB films of SMMA34K-40%,SMMA34K-60%,SMMA34K-80% and SMMA34 K exhibit the mixed structures of circular and long rod-like micelles.With the increase of transfer pressure,the LB films of SMMA34K-20% and SMMA34K-40% exhibit the mixed structures of circular and short rod-like micelles,that of SMMA34K-60% exhibits the mixed structure of circular and long rod-like micelles,and that of SMMA34 K and SMMA34K-80% exhibit planar structure.Moreover,there is little difference between the ?-A isotherms of the mixed monolayers spread with two methods:(1)spreading of a premixed solution and(2)separate spreading of each block copolymer solutions sequentially.However,large differences exist in the LB films prepared with the two methods due to the effects of sample addition sequence on the micelle formation process.