Bi-axially aligned crystallites of a fluorene–bithiophene co-polymer

Werzer, Oliver; Porzio, William; Trimmel, Gregor; Plank, Harald; Resel, Roland

doi:10.1016/j.eurpolymj.2012.10.014

Cited by 8 publications

(8 citation statements)

References 32 publications

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“…Great efforts have been devoted to unravel the characteristics of the aggregated F8T2 in films. Thermal analysis indicated that F8T2 could transform between amorphous, crystal, and liquid-crystal phases after annealing. , Manipulation of molecular order and crystallinity could cause F8T2 transformation in aggregate microstructure and morphology and greatly influence the device performances. , Alignment of F8T2 chains could be achieved via directional induction. ,, Solution processing could result in the self-assembly of the F8T2 chains into highly ordered nanostructures. , In this work, we show that F8T2 could self-assemble to J-aggregate in films, which is featured by red-shifted absorption spectra and is confirmed by theoretical simulation. The aggregated behavior is monitored by UV–vis absorption spectra under different conditions of annealing temperature, solvents, and molecular weights.…”

Section: Introductionmentioning

confidence: 67%

J-Aggregate Behavior of Poly[(9,9- dioctyluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) in Crystal and Liquid Crystal Phases

Wang

Song

et al. 2019

J. Phys. Chem. C

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Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) in thermally annealed films exhibits red-shifted absorption spectra, which shows the typical feature of the J-aggregate and is confirmed by computational simulations. By controlling the annealing temperature, the aggregate behavior is explored in detail. It is found that the J-aggregate is formed only when the material is annealed at crystallization and liquid crystal temperatures. The microstructure and morphology of the aggregates show that the J-aggregates have tighter chain packing and a larger ordered domain. This work first demonstrates the J-aggregate behavior of the F8T2 material and establishes the relationship between optical spectra and the packing structure of F8T2.

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Section: Introductionmentioning

confidence: 67%

J-Aggregate Behavior of Poly[(9,9- dioctyluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) in Crystal and Liquid Crystal Phases

Wang

Song

et al. 2019

J. Phys. Chem. C

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“…F8T2 exhibits intrinsic polarity that can interact with EEF because of the existence of the electronegative sulfur atom in the thiophene units. Meanwhile, F8T2 presents excellent molecular ordering and spontaneous self-assembled structures, and it can sensitively respond to external conditions (i.e., annealing, orientation layer, laser, and solvent atmosphere). − Research studies have indicated that F8T2 microstructures in films had a decisive influence on their photovoltaic performance. − Thermal analysis (Figure S1) has shown that F8T2 occurs at a glass-transition temperature of 127 °C and crystallizes at 170 °C and the crystallized F8T2 melts at 260 °C and transforms into a nematic liquid-crystal state. Finally, isotropy emerges at 320 °C.…”

Section: Introductionmentioning

confidence: 99%

Effect of External Electric Field on Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(bithiophene)] Chain Orderness, Morphology, and Carrier Mobility in Different Condensation Processes

Song

Liu

et al. 2019

J. Phys. Chem. C

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Poly[(9,-alt-co-(bithiophene)] (F8T2) is a kind of crystal and liquid-crystal conjugated polymer (CP). In this research, the effect of external electric field (EEF) on F8T2 chain orderness, morphology, and carrier mobility in different condensation processes of annealing at 130 °C (above glass-transition temperature), 200 °C (crystallization temperature), and 280 °C (liquid-crystal temperature) was investigated by UV−vis absorption spectroscopy, photoluminescence spectroscopy, Xray diffraction, atomic force microscopy, polarizing optical microscopy, transmission electron microscopy (TEM), and current density−voltage (C−V) curves. It was found that EEF could enhance F8T2 chain orderness and manipulate F8T2 chain self-assembly in all the above three types of annealed films. However, the responses of F8T2 chains to EEF were different. After applying EEF, a preferred arrangement along the EEF direction with needle-like crystals was presented in 130 °C annealed films, and ordered nanorod structures were observed in 280 °C annealed films. Meanwhile, subcrystallization with an increased crystallite size of 14.6% was also discovered in the annealed film at 200 °C. As a result, the hole mobilities of these films were improved 127% (130 °C), 367% (200 °C), and 320% (280 °C). The mechanism for both microstructure changes and hole mobility enhancement was revealed. This research sheds a new light to improve carrier mobility by utilizing EEF to control the chain-condensed state structure and film orderness. This also enlightens us to consider the relationship between external forces and chain self-assembly of CPs based on intrinsic properties of CPs and basic theory of condensed matter physics.

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“…23,24 Higher temperatures mean that the unit cell thermally expands and that a system has more energy present, allowing an adaption into different confinements. Similarly, the usage of solvent annealing is a way to induce similar changes compared to temperature treatments.…”

Section: Introductionmentioning

confidence: 99%

Morphologies of Phenytoin Crystals at Silica Model Surfaces: Vapor Annealing versus Drop Casting

et al. 2014

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The controlled preparation of different crystal morphologies with varying preferential orientation with respect to the substrate is of crucial importance in many fields of applications. In this work, the controlled preparation of different phenytoin morphologies and the dependency of the preferential orientation of those crystallites is related with the preparation method (solvent annealing vs drop casting), as well as the physical–chemical interaction with the solvents in use. While solvent annealing induces the formation of particular structures that are partially dewetted, the drop casting technique from various solvent results in the formation of needle-like and elongated structures, with each having a distinct morphology. The morphologies are explained via the Hansen solubility parameters and correlated with the solvent vapor pressures. X-ray diffraction experiments reveal preferential orientations with respect to the solid substrate and indicate the surface-mediated stabilization of an unknown polymorph of phenytoin with an elongated unit cell in the b-axis.

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Bi-axially aligned crystallites of a fluorene–bithiophene co-polymer

Cited by 8 publications

References 32 publications

J-Aggregate Behavior of Poly[(9,9- dioctyluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) in Crystal and Liquid Crystal Phases

J-Aggregate Behavior of Poly[(9,9- dioctyluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) in Crystal and Liquid Crystal Phases

Effect of External Electric Field on Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(bithiophene)] Chain Orderness, Morphology, and Carrier Mobility in Different Condensation Processes

Morphologies of Phenytoin Crystals at Silica Model Surfaces: Vapor Annealing versus Drop Casting

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