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.
The specific interaction between a strongly hydrophobic but still water-soluble cellulose derivative, ethyl(hydroxyethy1)cellulose (EHEC), and a low molecular weight anionic surfactant, sodium dodecyl sulfate (SDS), is studied in dilute solution without added neutral electrolyte by means of hydrodynamic (viscosity) and thermodynamic (dialysis equilibrium) measurements. The dialysis equilibrium shows strong adsorption of SDS at concentrations far below the normal cmc for SDS. The dialysis equilibrium is sensitive to the polymer concentration at higher SDS concentrations where the adsorption seems to decrease. In the region of increasing adsorption of SDS to EHEC the hydrodynamic measurements reveal a drastic reconformation of the polymer in dilute solution leading to a 4-fold reduction in hydrodynamic volume. At higher polymer concentrations the viscosity passes through a very marked maximum when the SDS concentration is increased. The results are interpreted in terms of a clustering theory for the SDS adsorption.
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