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Alkyl- π engineering in state control toward versatile optoelectronic soft materials

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ABSTRACT

Organic π-conjugated molecules with extremely rich and tailorable electronic and optical properties are frequently utilized for the fabrication of optoelectronic devices. To achieve high solubility for facile solution processing and desirable softness for flexible device fabrication, the rigid π units were in most cases attached by alkyl chains through chemical modification. Considerable numbers of alkylated-π molecular systems with versatile applications have been reported. However, a profound understanding of the molecular state control through proper alkyl chain substitution is still highly demanded because effective applications of these molecules are closely related to their physical states. To explore the underlying rule, we review a large number of alkylated-π molecules with emphasis on the interplay of van der Waals interactions (vdW) of the alkyl chains and π–π interactions of the π moieties. Based on our comprehensive investigations of the two interactions’ impacts on the physical states of the molecules, a clear guidance for state control by alkyl-π engineering is proposed. Specifically, either with proper alkyl chain substitution or favorable additives, the vdW and π–π interactions can be adjusted, resulting in modulation of the physical states and optoelectronic properties of the molecules. We believe the strategy summarized here will significantly benefit the alkyl-π chemistry toward wide-spread applications in optoelectronic devices.

No MeSH data available.


Chemical structure of an azobenzene derivative 28.
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Figure 21: Chemical structure of an azobenzene derivative 28.

Mentions: Our group synthesized a liquid azobenzene through substitution of a branched 2-octyldodecyl (2-C8C12) chain (vide infra) [17]. Quite recently, Masutani et al [93] reported a similar liquid azobenzene 28 (figure 21) attached with a 2-ethylhexyl (2-C2C6) chain and explored its application as solar thermal fuel, a material in which light energy could be converted to chemical bond energy and concequently discharged as heat upon external stimuli. As a popular molecular photo-switch, trans-azobenzene is a hot candidate for solar thermal fuels because the photon energy can be stored in the photochemical generated cis isomer in the form of molecular strain energy and can be released as heat through cis-to-trans thermal isomerization. Conventional photoisomerization of azobenzene always occurs in a dilute solution, resulting in a remarkable decrease of the total volumetric energy density. Nevertheless, the azobenzene liquid, 28, overcame this problem by facile photoisomerization even in a neat state, with a trans-to-cis rate comparable to those observed in a solution state. With such an excellent performance, liquid 28 could be promising for solar thermal storages.


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
Chemical structure of an azobenzene derivative 28.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036497&req=5

Figure 21: Chemical structure of an azobenzene derivative 28.
Mentions: Our group synthesized a liquid azobenzene through substitution of a branched 2-octyldodecyl (2-C8C12) chain (vide infra) [17]. Quite recently, Masutani et al [93] reported a similar liquid azobenzene 28 (figure 21) attached with a 2-ethylhexyl (2-C2C6) chain and explored its application as solar thermal fuel, a material in which light energy could be converted to chemical bond energy and concequently discharged as heat upon external stimuli. As a popular molecular photo-switch, trans-azobenzene is a hot candidate for solar thermal fuels because the photon energy can be stored in the photochemical generated cis isomer in the form of molecular strain energy and can be released as heat through cis-to-trans thermal isomerization. Conventional photoisomerization of azobenzene always occurs in a dilute solution, resulting in a remarkable decrease of the total volumetric energy density. Nevertheless, the azobenzene liquid, 28, overcame this problem by facile photoisomerization even in a neat state, with a trans-to-cis rate comparable to those observed in a solution state. With such an excellent performance, liquid 28 could be promising for solar thermal storages.

View Article: PubMed Central - PubMed

ABSTRACT

Organic π-conjugated molecules with extremely rich and tailorable electronic and optical properties are frequently utilized for the fabrication of optoelectronic devices. To achieve high solubility for facile solution processing and desirable softness for flexible device fabrication, the rigid π units were in most cases attached by alkyl chains through chemical modification. Considerable numbers of alkylated-π molecular systems with versatile applications have been reported. However, a profound understanding of the molecular state control through proper alkyl chain substitution is still highly demanded because effective applications of these molecules are closely related to their physical states. To explore the underlying rule, we review a large number of alkylated-π molecules with emphasis on the interplay of van der Waals interactions (vdW) of the alkyl chains and π–π interactions of the π moieties. Based on our comprehensive investigations of the two interactions’ impacts on the physical states of the molecules, a clear guidance for state control by alkyl-π engineering is proposed. Specifically, either with proper alkyl chain substitution or favorable additives, the vdW and π–π interactions can be adjusted, resulting in modulation of the physical states and optoelectronic properties of the molecules. We believe the strategy summarized here will significantly benefit the alkyl-π chemistry toward wide-spread applications in optoelectronic devices.

No MeSH data available.