COIL SIZE AND LONG-RANGE EXCIMERS .2. GOOD SOLVENT NONSOLVENT MIXTURES

This paper presents results of steady state fluorescence spectra measu rements on polyindene (PIN) and polyacenaphthylene (PAN) samples of di fferent molecular weights, in dilute solution at constant temperature, 25 degrees C. Solvents were prepared by mixing a solvent and a precip itant in different proportions. Large changes in the size of the parti cles in solution (determined by turbidimetric methods) caused by incip ient phase separation were necessary to produce significant changes of the excimer to monomer fluorescence ratio for both PIN and PAN. A lin ear relationship between the excimer to monomer fluorescence ratio and the volume of the polymer aggregates is found. Such a relationship is solvent viscosity independent. Several conclusions are drawn about th e phase separation process in very dilute polymer solutions.