In this study the morphology of spin-casted films of polymers blended with [6,6]-phenyl C61-butyric acid methyl ester (PCBM) has been studied. It was found that the lateral structure formation in the films
is favored by rapid solvent evaporation and strong polymer−PCBM repulsion. The formation of homogeneous
films is favored by slow evaporation and weak polymer−PCBM repulsion. The effect of solvent evaporation rate
is the opposite of what is found for spin-casting polymer−polymer blends. The results can be explained by the
kinetics of phase separation and the phase behavior involving limited solubility and crystallization of PCBM.
Topography and composition images of model thin films of deuterated polystyrene (dPS) and polyisoprene with different blend compositions were analyzed with an extension of integral-geometry approach. Surface patterns, formed in the course of spin-casting from toluene onto self-assembled monolayers (SAM), were recorded with scanning force microscopy. Their relation with lateral phase domain structures was demonstrated by dynamic secondary ion mass spectrometry, yielding maps of dPS distribution. Morphological measures, which cannot be provided by Fourier transform analysis (FTA), characterize individual images, compositional series of the surface patterns and individual features of the patterns. Different morphologies (nucleation-and spinodal-type and hole-and island-dominated ones) are consistently characterized by the Minkowski measures and related parameters. For instance, the latter can measure circular character of the individual features and estimate dominant lateral length (determined rigorously with FTA). Lateral morphologies are hardly affected when CH3-terminated SAM is exchanged for SAM with COOH end groups.
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