The dynamic process of intramolecular excimer formation in diastereoisomeric oligomers [dimers: meso (m)- and racemic (r)-4,6-diphenylnonane (PS2), trimers: mm-, mr- and rr-4, 6,8-triphenylundecane (PS3), and tetramers: mmm-, mmr-, mrm-, rrm-, and rrr-4, 6,8, 10-tetraphenyltridecane (PS4)], model compounds of polystyrene, was investigated by using a picosecond pulse radiolysis technique. Monomer fluorescence of all-racemic isomers (r PS2, rr PS3, rrr PS4) and rrm PS4 decays single-exponentially, while that of other isomers decays dual-exponentially. Multicomponent fluorescence decay curves are supposed to be mainly induced by conformational changes. The results suggest that the excimer in oligostyrenes (or polystyrene) is formed mainly in meso diad. It is proved that there exists singlet energy migration in styrene trimer and tetramer systems. The conformational change in PS3 and PS4 is concluded to occur by cooperative motions in backbone chains bond such as a crankshaft transition, but not by way of independent rotation around each carbon-carbon bond of the backbone chain.
|Number of pages||7|
|Journal||Radiation Physics and Chemistry|
|Publication status||Published - 1989 Dec 1|
|Event||Proceedings of an International Symposium on Fast Excitation Processes - Tokyo, Jpn|
Duration: 1988 Mar 21 → 1988 Mar 25
ASJC Scopus subject areas