The Role of Intermolecular Interactions in Solid State Fluorescent Conjugated Polymer Chemosensors

Abstract

A functionalized fluorescent conjugated polymer, tolylterpyridine poly(p-phenyleneethynylene-thienyleneethynylene (ttp-PPETE), was designed and synthesized to detect trace amounts of toxic transition metal pollutants in ground water. Photophysical studies in tetrahydrofuran (THF) successfully demonstrated this polymer as a selective and sensitive chemosensor for Ni(2+) and Co(2+) in aqueous solution. Solid state composites of these chemosensors have now been prepared which can be modified to provide for inexpensive and portable field based chemical detection. A solid composite of ttp-PPETE, blended with poly (methyl methacrylate) shows UV-vis absorption and fluorescence emission spectra which are red- shifted when compared to solution phase spectra, suggesting an increase in conjugation in the solid state. An additional absorption peak, not present in solution, is also observed in the solid state. The presence of this new peak provides evidence of interacting FCP chains in the solid state. Concentration dependent experiments were done on the solid composite showing red-shifted emission peaks accompanied by a significant reduction in the fluorescent quantum yield. These observations are consistent with the formation of aggregated polymer species in the solid state. Intermolecular interactions of this type can be manipulated in the design of sensitive and selective solid state fluorescent conjugated polymer sensors.

Spectral Characteristics and Sensor Ability of a New 1,8-Naphthalimide and Its Copolymer with Styrene

“…The excitation spectrum maximum was at 451 nm, while the fluorescence peak was at 502 nm. The bathochromic shift of excitation and fluorescence maxima compared to those in the toluene solution can be explained by the solid fixation of NI3 into the polymer matrix and the inability to undergo conformational changes [ 40 , 41 ].…”

“…The excitation spectrum maximum was at 451 nm, while the fluorescence peak was at 502 nm. The bathochromic shift of excitation and fluorescence maxima compared to those in the toluene solution can be explained by the solid fixation of NI3 into the polymer matrix and the inability to undergo conformational changes [40,41]. The photophysical characteristics of the poly(St-co-N3) were also examined in the toluene solution, where the copolymer was well soluble and in a thin polymer film (60 µm).…”

Intramolecular charge transfer (ICT) of a chiroptically active conjugated polymer showing green colour

“…In addition, intramolecular and intermolecular interactions exert considerable influences on the properties. 12,13 Higher-order structures of organic materials are dependent on these interactions and molecular shapes. Precise molecular design can lead to desirable, highly-ordered structures for various applications.…”

Pentiptycene-Derived Fluorescence Turn-Off Polymer Chemosensor for Copper(II) Cation with High Selectivity and Sensitivity

“…A more practical approach is to transfer the FCPs from solution to a solid-state matrix, and incorporate them into a field-based chemical sensing device [23][24][25]. Previous studies in the Jones group and others have shown that the photophysical properties of the solid state chemosensors are significantly affected by intermolecular interactions among polymer chains [26]. This phenomenon has been shown to significantly reduce the quantum efficiency of light emitting diodes (LEDs) and sensor devices.…”