Solid-solution formation and phase segregation in binary systems of homologous extended-chain perfluorinated alkanes

Using differential scanning calorimetry (DSC) and X-ray analysis it is show n that binary systems of perfluorinated alkanes form solid solutions or exh ibit eutectic phase behaviour, depending on their difference in chain lengt h. A simple model, which successfully correlated experimental results for t his aspect of phase behaviour of binary n-alkane systems, is demonstrated t o quantitatively describe the behaviour of perfluorinated alkanes as well. From the model parameters and experimental observations, it appears that, a t equal number of carbon atoms, binary perfluorinated alkane systems allow for a larger chain difference than their hydrogenated analogues, before eut ectic phase behaviour sets in. (C) 1999 Elsevier Science Ltd. All rights re served.