Helical conjugated polymers are of great interest for their potential as sources of circularly polarized luminescence for numerous electro-optical device applications including display technologies. Due to their relatively strong absorption cross sections and high emissivity in the visible wavelength range, these materials permit a detailed investigation of how the transition between helical and random coil forms are driven by polymer structural features such as chain length and chemical defects as well as environmental properties such as solvent and temperature. Bulk methods such as circular dichroism, absorption, and fluorescence as well as single-particle microscopy is used to probe the helix-to-coil phase transition in a model chiral polyfuran and to determine whether the conformations favored in solution are retained in the solid state. In addition, the transient dynamics and the effects of chemical doping on the electronic properties of the helix and coiled forms are explored.
Aggregation in conjugated polymers is a well-recognized driver of performance in organic opto-electronic devices. In particular, good device performance is correlated with processing methods that also minimize non-radiative traps that quench emission in thin films. Here we compare the efficacy of various solvent systems in producing weakly versus highly emissive aggregates in the well-studied polymer poly(3-hexylthiophene) or P3HT and show that many systems that appear highly quenched in bulk solution are strongly emissive in the solid state. Microscopy, transient dynamical measurements, and structural studies to probe the electronic and structural differences between weakly and highly emissive aggregates are described.
Helical conjugated polymers are of great interest for their potential as sources of circularly polarized luminescence for numerous electro-optical device applications including display technologies. Due to their relatively strong absorption cross sections and high emissivity in the visible wavelength range, these materials permit a detailed investigation of how the transition between helical and random coil forms are driven by polymer structural features such as chain length and chemical defects as well as environmental properties such as solvent and temperature. Bulk methods such as temperature dependent absorption, emission, and circular dichroism as well as single-particle microscopy are used to probe the helix-to-coil phase transition in a model chiral polyfuran and to determine whether the conformations favored in solution are retained in the solid state. In addition, the transient dynamics and the effects of chemical doping on the electronic properties of the helix and coiled forms are explored.
Helical conjugated polymers are of great interest for their potential as sources of circularly polarized luminescence and as magnetic field sensors. Due to their relatively strong absorption cross sections and high emissivity in the visible wavelength range, these materials permit a detailed investigation of how the transition between helical and random coil forms are driven by polymer structural features such as chain length and chemical defects as well as environmental properties such as solvent and temperature. Bulk methods such as circular dichroism, absorption, and fluorescence as well as single-particle microscopy is used to probe the helix-to-coil phase transition in a model chiral polyfuran and to determine whether the conformations favored in solution are retained in the solid state.
The integration of furan based repeat units into conjugated systems meant for optoelectronic applications has generally been limited by the photostability of the furan unit. This limitation is due to the susceptibility of furan towards reaction with singlet oxygen, which disrupts the conjugation of the system. Here, we present a family of helical, ester-functionalized polyfurans with dramatically enhanced photostability. Within this family, the emission intensity of P3HEF is essentially non-existent while a chiral branched variant, (S)-P3EHEF, is highly fluorescent. This discrepancy is due to the difference in the compactness of the helical structure of the two polymers. Interestingly, the emission wavelength of (S)-P3EHEF can be tuned through several different techniques such as deposition speed and solvation conditions. The mechanism behind the tunability was explored using fluorescence-based techniques.
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