EVIDENCE OF SCREENING OF HYDRODYNAMIC AND EXCLUDED VOLUME INTERACTIONS IN SEMI-DILUTE POLYMER-SOLUTIONS BY INTRAMOLECULAR EXCIMERS

The preliminary results described in this work concern a poly(vinyl acetate) sample with a fraction w equals 0. 01 of pyrenyl substituents and molecular weight ca. 10**5. Under steady-state conditions the measured excimer and monomer quantum yields are quantities averaged over the quantum yield contributions of macromolecules with different reactive configurations. The description of the average rate constant k OVER BAR extracted from F//E/F//M would require the knowledge of the details of the distribution function of the reactive configurations, W(k). However, the authors have observed (6,7,16) that their system, with w equals 0. 01 and a fluorescence lifetime of ca. 200 ns, behaves as a quasiregular polymer.