posted on 2002-04-16, 00:00authored byKurt A. Alberty, Eric Tillman, Stephane Carlotti, Kevin King, Stephen E. Bradforth, Thieo E. Hogen-Esch, David Parker, W. James Feast
Macrocyclic polystyrene (PS) was synthesized by initiation of styrene by naphthalide anion
or benzylic dianions in the presence of Li or K ions followed by reaction of the resulting PS dianions with
dibromomethane (DBM) or 1,4-bis(bromomethylbenzene) (DBX) in THF at −78 °C under high dilution
conditions. MALDI and NMR studies of the DBM cycles showed the presence of 1,2-diphenyl linkages.
Fluorescence studies on the DBM cycles show strongly enhanced and anomalous structured emission
bands between 300 and 320 nm attributable to linear chains containing styrenic chain end impurities.
This indicates rapid metal bromine exchange to give chain end benzyl bromides that eliminate with
polystyryl anion to give small (<1.0%) fractions of styrene type chain end structures. In comparison, the
cycles obtained with DBX show only the PS monomer and excimer bands at 285 and 330 nm, respectively,
and appear to be substantially free of such side reactions. These DBX coupled cycles show up to a 2-fold
enhancement in the monomer fluorescence at low MW compared with matching linear polystyrenes that
show essentially no MW dependence. This may be due to the increased rigidity of the cycles as molecular
weights decrease and appears to be a general feature for cyclic vinyl aromatic polymers.