Interplay Between J‐ and H‐Type Coupling in Aggregates of π‐Conjugated Polymers: A Single‐Molecule Perspective

Abstract

Strong dipole–dipole coupling within and between π‐conjugated segments shifts electronic transitions, and modifies vibronic coupling and excited‐state lifetimes. Since J‐type coupling between monomers along the conjugated‐polymer (CP) chain and H‐type coupling of chromophores between chains of a CP compete, a superposition of the spectral modifications arising from each type of coupling emerges, making the two couplings hard to discern in the ensemble. We introduce a single‐molecule H‐type aggregate of fixed spacing and variable length of up to 10 nm. HJ‐type aggregate formation is visualized intuitively in the scatter of single‐molecule spectra.

Self‐Amplified Photon Guiding in the Luminescent Organic Semiconductor Nanowires

“…The vibronic 0–1 transition has a higher intensity than the electronic 0–0 transition, which is the characteristic of H‐type aggregate. [ 27 ] With the same PIC monomer, we could also obtain J‐type aggregate, which shows distinct spectral feature and crystal morphology (Figure S8, Supporting Information). Further, we also notice that the polarization dependency mainly originates from the vibronic transitions (0–1 and 0–2), while the electronic transition (0–0) is less sensitive to the detection polarization.…”

Precise Stepwise Synthesis of Donor-Acceptor Conjugated Polymer Brushes Grafted from Surfaces

“…In consequence, they induce contradictory changes in UV-Vis spectra: J-aggregates lead to a batochromic shift, while H-aggregates move the absorption maximum towards a shorter wavelength. Despite an opposite influence on the spectroscopic behavior of the coating, these two types of interactions are not competitive—they may be both enhanced by the extended, planar conformation of the chains [ 24 ]. Thus, the observed widening of the band and changes in intensity ratio could be assigned to the existence of both effects indicating the presence of ordered densely packed polymer brushes.…”

“…As a result, conductive PB were shown to exhibit, e.g., three orders of magnitude higher current density [ 20 ] and enhanced stability [ 23 ] in comparison to the same polymers obtained in solutions. A well-defined arrangement of polymer chains within the layer also contributes to strengthening inter and intramolecular interactions, as they are both dependent on the macromolecular organization [ 24 ]. That is why a lot of effort has been put into investigating conformational changes in grafted macromolecules, which can be induced by external stimuli [ 25 ].…”

An Azobenzene-Clamped Bichromophore

“…As we showed in earlier work, the dependence of the PL spectra and PL lifetime on the interchromophore distance can be described in the framework of H-type electronic coupling of molecular aggregates. 13 , 29 As the chromophore separation decreases, the PL spectrum is shifted to lower photon energies and the oscillator strength of the radiative transition decreases. The comparison with the 0.7 nm-spaced rigid clamp reference 2 in Figure 2 indicates a slightly increased chromophore spacing of the azobenzene bichromophore 1 , and hence the PL spectrum of 1 is blue-shifted and the PL lifetime is slightly lowered to τ 2 = 648 ps with respect to 2 .…”