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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.


(a) Chemical structure of molecule 4. (b) SEM image of self-assembled microwires from a solution of 4 in a 2:3 CHCl3/ethanol (EtOH) mixture by evaporating the solvents slowly. SEM images of self-assembled 4 precipitated by cooling of its hot homogeneous solution at different temperatures: 15 °C (c), 20 °C (d), 25 °C (e), 30 °C (f) and 35 °C (g). Reprinted with permission from H-B Chen et al 2009 Langmuir25 5459, © 2009 American Chemical Society.
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Figure 5: (a) Chemical structure of molecule 4. (b) SEM image of self-assembled microwires from a solution of 4 in a 2:3 CHCl3/ethanol (EtOH) mixture by evaporating the solvents slowly. SEM images of self-assembled 4 precipitated by cooling of its hot homogeneous solution at different temperatures: 15 °C (c), 20 °C (d), 25 °C (e), 30 °C (f) and 35 °C (g). Reprinted with permission from H-B Chen et al 2009 Langmuir25 5459, © 2009 American Chemical Society.

Mentions: With the same temperature-regulating self-assembly strategy, the Pei group also obtained 3D flower-shaped micro-objects using a benzothiophene derivative appended with n-dodecyl chains [38]. In addition, the same group reported the morphology tuning of chiral microtwists through temperature control [39]. By slowly evaporating a solution of an achiral compound 4 (figure 5(a)) in a 2:3 CHCl3/ethanol (EtOH) mixture (1 mg mL−1), perfectly twisted chiral structures with uniform pitch were obtained (figure 5(b)). Interestingly, with different precipitation temperatures, the pitch of the microtwist could be easily tuned (figures 5(c)–(g)). Basically, a higher temperature led to a slower precipitation process and thus a larger pitch. This phenomenon was explained by special crystal growth kinetics, according to which the driving force for twisting derived from the imbalance of the growth rate between the center and the edge of the self-assembled nanobelts.


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
(a) Chemical structure of molecule 4. (b) SEM image of self-assembled microwires from a solution of 4 in a 2:3 CHCl3/ethanol (EtOH) mixture by evaporating the solvents slowly. SEM images of self-assembled 4 precipitated by cooling of its hot homogeneous solution at different temperatures: 15 °C (c), 20 °C (d), 25 °C (e), 30 °C (f) and 35 °C (g). Reprinted with permission from H-B Chen et al 2009 Langmuir25 5459, © 2009 American Chemical Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: (a) Chemical structure of molecule 4. (b) SEM image of self-assembled microwires from a solution of 4 in a 2:3 CHCl3/ethanol (EtOH) mixture by evaporating the solvents slowly. SEM images of self-assembled 4 precipitated by cooling of its hot homogeneous solution at different temperatures: 15 °C (c), 20 °C (d), 25 °C (e), 30 °C (f) and 35 °C (g). Reprinted with permission from H-B Chen et al 2009 Langmuir25 5459, © 2009 American Chemical Society.
Mentions: With the same temperature-regulating self-assembly strategy, the Pei group also obtained 3D flower-shaped micro-objects using a benzothiophene derivative appended with n-dodecyl chains [38]. In addition, the same group reported the morphology tuning of chiral microtwists through temperature control [39]. By slowly evaporating a solution of an achiral compound 4 (figure 5(a)) in a 2:3 CHCl3/ethanol (EtOH) mixture (1 mg mL−1), perfectly twisted chiral structures with uniform pitch were obtained (figure 5(b)). Interestingly, with different precipitation temperatures, the pitch of the microtwist could be easily tuned (figures 5(c)–(g)). Basically, a higher temperature led to a slower precipitation process and thus a larger pitch. This phenomenon was explained by special crystal growth kinetics, according to which the driving force for twisting derived from the imbalance of the growth rate between the center and the edge of the self-assembled nanobelts.

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.