Accession Number : ADA330183

Title :   Photoluminescence in Pyridine-Based Polymers: Role of Aggregates

Descriptive Note : Technical rept.

Corporate Author : OHIO STATE UNIV COLUMBUS DEPT OF PHYSICS

Personal Author(s) : Blatchford, J. W. ; Jessen, S. W. ; Lin, L. B. ; Gustafson, T. L. ; Epstein, A. J.

PDF Url : ADA330183

Report Date : 20 SEP 1997

Pagination or Media Count : 12

Abstract : We present a study of the morphology dependence of the photoluminescence (PL) properties of the pyridine-based polymers poly(p-pyridine), and poly(p-pyridyl) vinylene p-phenylene vinylene) (PPyVPV). The photoluminescence of solution samples is characterized by high quantum efficiency (> 70% in PPyVPV), weak coupling to vibrational modes (Huang-Rhys parameter ^0.5) and a single-exponential decay (radiative lifetime ^1 ns). On the other hand, film samples display strongly redshifted, featureless emission with low quantum yield (<20%) and highly nonexponential decay dynamics. Through consideration of absorption and excitation spectra, the 'site-selectivity' of the PL, and the concentration dependence of the PL spectrum, we demonstrate that the redshifted film spectra are a result of the formation of low-energy aggregate sites due to strong interchain interactions. Time-resolved measurements suggest a longer radiative lifetime for the aggregate vs. solution, leading to the lower efficiency. Aggregate formation is found to be morphology dependent, and is minimal in 'powder' samples which are precipitated after polymerization.

Descriptors :   *PHOTOLUMINESCENCE, REPRINTS, POWDERS, POLYMERIZATION, MORPHOLOGY, FILMS, AGGREGATES(MATERIALS), QUANTUM EFFICIENCY, PYRIDINES, PHASE CONJUGATION.

Subject Categories : Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE