Effects of the Hydrogen Bonding on the Fluorescence of Ketone-Substituted Poly(phenylene)s in Solutions and Solid State

The fluorescence intensities of poly(2-benzoyl-1,4-phenylene) (PBP) and poly(2-trifluoroacetyl-1,4-phenylene) (PTFAP) in chloroform and dioxane solutions were found to decrease on addition of phenols. The fluorescence intensity diminishes in proportion to the acidity of phenols. Similar phenomena were observed on addition of acetic acid and a fluorinated alcohol. However, when the poly(p-vinylphenol) (PVPh) was added to these polymer solutions, the fluorescence intensity increased with an increasing amount of PVPh. These results suggest that hydrogen bonding between the carbonyl group of PBP or PTFAP and the OH group of phenols has opposite effects on fluorescence in the two cases. The strong hydrogen bonding with small phenol compounds in the excited state may increase the restriction of the bond rotation between the phenyl rings of the polymer and result in decreasing of π-electron conjugation and the fluorescence intensity. On PVPh addition to the polymer solution, the PVPh chain may wrap around PBP or PTFAP via hydrogen-bonding formation and reduce polymer chain associations, thereby mitigating the concentration quenching effect and conferring a large position contribution to the fluorescence intensity. PTFAP−PVPh blend films were prepared. Among these blends, 1 wt % of PTFAP in PVPh showed the highest fluorescence emission intensity 80 times larger than that of the pure PTFAP film. This suggests that the PTFAP chains are dispersed molecularly, or nearly so, in a matrix of PVPh in the 1 wt % blend; consequently, each polymer chain contributes additively to the emission intensity with a minimal deleterious impact due to aggregation.