Effects of polymer structure on singlet energy migration in poly(2-naphthylalkyl methacrylates)

Abstract

The effects of the pendant group structure on intramolecular singlet energy migration and excimer formation in poly(2-naphthylmethyl methacrylate) (PNMMA), poly[l-(2-naphthyl)ethyl methacrylate] (P-1-NEMA), poly[2-(2-naphthyl)ethyl methacrylate] (P-2-NEMA), and poly[3-(2-naphthyl)propyl methacrylate] (P-3-NPMA) were examined by fluorescence quenching experiments in deaerated 2-methyltetrahydrofuran. Introduction of steric hindrance near the naphthalene chromophore (P-1-NEMA) or of a polymethylene bridge between the polymer main chain and the naphthalene chromophore (P-2-NEMA and P-3-NPMA) was found to reduce excimer formation but retard energy migration as well, suggesting that more specific chromophore arrangement along the polymer chain is desirable for selective promotion of energy migration and suppression of excimer formation. In film, these polymers exhibited little monomer emission; extensive emission from excimer (PNMMA, P-2-NEMA, and P-3-NF'MA) or that from a second-excimer-like trap (P-1-NEMA) indicates efficient trapping of excitation energy at these trap sites. The formation of the higher energy trap in P-1-NEMA film is discussed in terms of the conformational constraints, Le., increased chromophore separation and chain rigidity, imposed by the pendant group structure.

Intramolecular Hydrogen Bonding in Isotactic Poly(methacrylamide)s and Its Implications for Control of Side-Chain Orientation

“…The chromophore interactions in the excited state, i.e., excitation energy transport and trapping, are affected by the stereoregularity and conformation of the main chain 3 as well as by the steric hindrance introduced in the side chain. 4 While it is not fully understood how these structural differences actually affect energy migration and excimer formation, one may be able to enhance the former and suppress the latter if one properly controls the orientation of the chromophores along the polymer chain. If this is possible, "a molecular wire" will be obtained which allows efficient one-dimensional transport of excitation energy along the polymer chain.…”

Poly(methyl methacrylate) copolymers containing pendant carbazole and oxadiazole moieties for applications in single‐layer organic light emitting devices

“…Close proximity of the chromophores can result in the formation of an excimer between excited and spatially adjacent ground‐state chromophores typically through a mixture of exciton and charge transfer states 36, 37. The mutual chromophore separation, orientation, and mobility are vital in controlling the photophysics of polymers with pendant π‐conjugated rings 24, 38. The similarity in spectral response between vinylcarbazole and MMAK suggests that the electronic characteristics of the carbazole unit are not significantly altered by the change in functional group attached to the ring.…”

“…36,37 The mutual chromophore separation, orientation, and mobility are vital in controlling the photophysics of polymers with pendant p-conjugated rings. 24,38 The similarity in spectral response between vinylcarbazole and MMAK suggests that the electronic characteristics of the carbazole unit are not significantly altered by the change in functional group attached to the ring. Nonetheless, solutions containing the homopolymers, PVK and PMMAK, exhibit significantly different spectra and are presented in Figure 6(b); both polymers are of similar molecular weight and are dissolved in THF at similar concentrations (1 mg/ mL).…”

“…5), would diminish the probability of parallel ring overlap for excimer formation. 24,38 The PL spectra of PMMAK in chlorobenzene at various concentrations are presented in Figure 7. In Figure 7(a), the inner-filter effect 40 is clearly demonstrated as there is significant enhancement of overall photoluminescence intensity with decreasing PMMAK concentration.…”

Designing fluoroprobes through Förster resonance energy transfer: surface modification of nanoparticles through “click” chemistry

“…58,59 Close proximity of the chromophores can result in the formation of an excimer between excited and spatially adjacent ground-state chromophores typically through a mixture of exciton and charge transfer states. 60,61 The mutual chromophore separation, orientation, and mobility are vital in controlling the photophysics of the pendant p-conjugated rings 62,63 since excimer emission in these carbazole-based systems requires excimer forming geometries to exist prior to being excited or to form during the monomeric excited state lifetime.…”