Vibrational Characterization and Fluorescence Optimization of Polycyclic Polymers

Abstract

A systematic series of polycyclic novel polymers was studied by Raman spectroscopy. The effect of the sequential introduction of polycyclic aromatic ring substituents into the delocalized backbone was examined in relation to the variation of the relative ring breathing and stretching as well as the vinyl stretch frequencies. Replacement of the phenyl units by higher order acene moieties such as naphthyl and anthryl results in a shift of the characteristic stretching frequencies, and analysis of the vinyl stretch leads to the confirmation that higher order acene substitution into the delocalized backbone substantially weakens the vinyl bond. Semiquantitative integrated Raman analysis shows a well-defined variation of the vibrational characteristics with structure. The structural variation of the integrated Raman intensity elucidates the effect of the electronic and vibrational decoupling introduced by the continual systematic acene substitution and points toward the ability to tailor the vibrational characteristic of the polymeric systems much the same as the electronic characteristics are manipulated. Relative fluorescence yields calculated for absorption and fluorescence spectroscopy can be seen to be well-correlated with integrated Raman intensities, implying that the reduction of the vibrational intensity limits the avenues of nonradiation, hence optimizing the fluorescence yield.