Mikroparakristalle in der Physik

Hösemann, R.

doi:10.1002/phbl.19780341103

Cited by 7 publications

(2 citation statements)

References 13 publications

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“…1). 14–18 In this contribution, we show how accounting for this structural complexity of neat polymers can help to explain an unresolved question: the origin and yield of long‐lived photogenerated charges in neat conjugated polymer films.…”

Section: Introductionmentioning

confidence: 99%

The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers

Reid

Malik

Latini

et al. 2011

J Polym Sci B Polym Phys

109

170

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The influence of solid-state microstructure on the optoelectronic properties of conjugated polymers is widely recognized, but still poorly understood. Here, we show how the microstructure of conjugated polymers controls the yield and decay dynamics of long-lived photogenerated charge in neat films. Poly(3-hexylthiophene) was used as a model system. By varying the molecular weight, we drive a transition in the polymer microstructure from nonentangled, chain-extended, paraffinic-like to entangled, semicrystalline (M W ¼ 5.5-347 kg/mol). The molecular weight range at which this transition occurs (M W ¼ 40-50 kg/mol) can be deduced from the drastic change in elongation at break found in tensile tests. Linear absorption measurements of free-exciton bandwidth and time-resolved microwave conductivity (TRMC) measurements of transient photoconductance track the concomitant evolution in optoelectronic properties of the polymer as a function of M W . TRMC measurements show that the yield of free photogenerated charge increases with increasing molecular weight in the paraffinic regime and saturates at the transition into the entangled, semicrystalline regime. This transition in carrier yield correlates with a sharp transition in free-exciton bandwidth and decay dynamics at a similar molecular weight. We propose that the transition in microstructure controls the yield and decay dynamics of long-lived photogenerated charge. The evolution of a semicrystalline structure with well-defined interfaces between amorphous and crystalline domains of the polymer is required for spatial separation of the electron and hole. This structural characteristic not only largely controls the yield of free charges, but also serves as a recombination center, where mobile holes encounter a bath of dark electrons resident in the amorphous phase and recombine with quasi first-order kinetics.

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Section: Introductionmentioning

confidence: 99%

The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers

Reid

Malik

Latini

et al. 2011

J Polym Sci B Polym Phys

109

170

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“…It indicated that the T cc observed from DSC thermograms in Figure 2 was only the apparent value, which could not reflect the microstructure changes in the PET films. At T a = 107 °C, the WAXD peaks located at 2 θ = 16.6° and 22.3° were broadening because of the small size of the PET crystal 42,43 . These two diffraction peaks were split into two and became sharper when T a was increased from 110 to 250°C, which meant the PET crystals grew larger and became more perfect.…”

Section: Resultsmentioning

confidence: 97%

The investigation of the growth and perfection of the poly(ethylene terephthalate) crystalline region from amorphous state during annealing using a controlled temperature gradient

Wang

Bin

2021

Polymer Crystallization

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The growth and perfection of the crystalline region during the annealing of amorphous poly(ethylene terephthalate) (PET) was studied systematically using a homemade temperature gradient (T‐gradient) ranging from 50 to 250°C. Double melting peaks were observed from the differential scanning calorimetry (DSC) thermograms when PET film was annealed at the temperatures (Ta) above the PET crystallization temperature (Tc ≈ 120°C) with a constant primary melting peak at around 256°C and an increased secondary melting peak on the range of 120 and 250°C. The profound broadening of the wide angle X‐ray diffraction (WAXD) peaks in both transmission and reflection modes indicated that there were a lot of tiny crystals when PET films were annealed between 120 and 200°C, and the shift of the WAXD peaks revealed the presence of the paracrystals in the PET films. The growth and perfection of crystalline region of PET in condition of amorphous and annealed (Ta = 128°C) PET samples were investigated on the basis of Fourier transform infrared spectra and simultaneous WAXD‐DSC measurement. It was found that the conformational transition of the soft ethylene glycol moiety and rigid phenylene moiety in amorphous PET began at around 120 and 200°C, respectively. The microcrystal sizes in the PET film annealed at 128°C exhibited no change at the time that the secondary melting peak showed up, which meant the secondary melting peak might be attributed to the melting of the paracrystals inside or on the surface of the microcrystals.

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Dipolare Spin‐Gitter‐Relaxation in Polyethylen niederer Dichte

Ludwigs

Geschke

1981

Annalen der Physik

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Herrn Prof. D r . A . Msche zum 60. Geburtstag gewidmetInhaltsiibersicht. Durch die Untersuchung der Spin-Gitter-Relaxation der dipolaren Energie ist es moglich, langsame Bewegungen in den verschiedenen morphologischen Bereichen des Polyethylens getrennt zu erfassen. Die Ergebnisse werden mit Hilfe eines Dreibereichsmodells diskiiticrt . Dipolar Spin-Lattice Relaxation in Low-Density PolyethyleneAbstract. The investigation of the spin-lattice relaxation of the dipolar energy enables one to consider separately slow motions in the different morphological domains of polyethylene. The results are discussed by means of a three-phase-model.

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Mikroparakristalle in der Physik

Cited by 7 publications

References 13 publications

The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers

The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers

The investigation of the growth and perfection of the poly(ethylene terephthalate) crystalline region from amorphous state during annealing using a controlled temperature gradient

Dipolare Spin‐Gitter‐Relaxation in Polyethylen niederer Dichte

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