Sensory responses in solution vs solid state: A fluorescence quenching study of poly(iptycenebutadiynylene)s

A new series of poly(p-phenylenebutadiynylene)s has been synthesized with unique polymer structural features. In these systems each of the p-phenylene units in the conjugated backbone is the core of a rigid three-dimensional iptycene scaffold. The fluorescence quenching properties of these polymers in response to a series of electron-deficient aromatic compounds have been investigated in both solution and the solid state. It was found that in solution these polymers displayed higher quenching sensitivity toward studied quenchers compared to a more open-structure iptycene-containing poly(p-phenyleneethynylene). The quenching behaviors of the conjugated polymer were shown to be strongly influenced by the configuration of the incorporated iptycences. The thin films investigations revealed differences in both the fluorescence quenching and the recovery processes. Distinct behaviors indicated that the fluorescence quenching in the solid state is dictated by different factors than those in solution. Our results further suggest that poly(p-phenylenebutadiynylene)s containing large iptycene scaffolds that introduce porosity have the ability to efficiently sequester the quencher molecules within thin films as these materials display slow fluorescence recoveries.