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| 2. |
- Schwartz, Erik, et al.
(författare)
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"Helter-Skelter-Like" Perylene Polyisocyanopeptides
- 2009
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Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 15:11, s. 2536-2547
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Tidskriftsartikel (refereegranskat)abstract
- We report on a combined experimental and computational investigation on the synthesis and thorough characterization of the structure of perylene-functionalized polyisocyanides. Spectroscopic analyses and extensive molecular dynamics studies revealed a well defined 4, helix in which the perylene molecules form four "helter skelter-like" overlapping pathways along which excitons and electrons can rapidly migrate. The well-defined polymer scaffold stabilized by hydrogen bonding, to which the chromophores are attached, accounts for the precise architectural definition, and molecular stiffness observed for these molecules. Molecular-dynamics studies showed that the chirality present in these polymers is expressed in the formation of stable right-handed helices. The formation of chiral supramolecular structures is further supported by the measured and calculated bisignated Cotton effect. The structural definition of the chromophores aligned in one direction along the backbone is highlighted by the extremely efficient exciton migration rates and charge densities measured with Transient Absorption Spectroscopy.
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| 3. |
- Westenhoff, Sebastian, et al.
(författare)
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Anomalous energy transfer dynamics due to torsional relaxation in a conjugated polymer
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 97:16
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Tidskriftsartikel (refereegranskat)abstract
- In isolated conjugated polymers two explanations are in discussion for the redshift of the emission on a picosecond time scale-exciton energy transfer (EET) between conjugated segments along the chains and conformational changes of these segments themselves, i.e., torsional relaxation. In order to resolve this question we perform femtosecond time-resolved transient absorption measurements of the energy relaxation of poly[3-(2,5-dioctylphenyl) thiophene] in toluene solution. We show that torsional relaxation can be distinguished from EET by site-selectively exciting low-energy conjugated segments. We present a unified model that integrates EET and torsional dynamics. In particular, comparison to ultrafast depolarization measurements shows that torsional dynamics cannot be neglected when analyzing EET dynamics and furthermore reveals that the exciton extends itself by about 2 monomer units during torsional relaxation.
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| 4. |
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| 5. |
- Westenhoff, Sebastian, 1978, et al.
(författare)
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Probing the morphology and energy landscape of blends of conjugated polymers with sub-10 nm resolution.
- 2008
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Ingår i: Physical review letters. - 0031-9007. ; 101:1
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the charge generation dynamics in intimately mixed blends of polyfluorene copolymers optimized for photocurrent generation. Using femtosecond transient absorption spectroscopy, we find that the charge generation time is limited by exciton diffusion to the interface. Combined with the kinetics of exciton energy migration, the data reveal the blend morphology on a length scale of sub-10 nm. Furthermore, we demonstrate that excitons are guided efficiently to the interface, which is consistent with an accumulation of low energy sites at the heterojunction.
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