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

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.


SEM (a) and atomic force microscopy (AFM) (b) images of nanodisks formed by cooling a 1,4-dioxane solution of 1a from 60 °C to 20 °C. SEM (c) image of square-shaped objects loosely rolled up in each corner formed by rapid cooling of 1,4-dioxane solution of 1a from 60 °C to 5 °C. SEM images (d), (e) of the further rolled up objects of crumpled structures at the four corners. SEM (f) and TEM (g) images of final flower-shaped assemblies of 1a precipitated by slow aging at 5 °C. Reprinted with permission from T Nakanishi et al 2007 Small3 2019, © 2007 John Wiley & Sons.
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Figure 3: SEM (a) and atomic force microscopy (AFM) (b) images of nanodisks formed by cooling a 1,4-dioxane solution of 1a from 60 °C to 20 °C. SEM (c) image of square-shaped objects loosely rolled up in each corner formed by rapid cooling of 1,4-dioxane solution of 1a from 60 °C to 5 °C. SEM images (d), (e) of the further rolled up objects of crumpled structures at the four corners. SEM (f) and TEM (g) images of final flower-shaped assemblies of 1a precipitated by slow aging at 5 °C. Reprinted with permission from T Nakanishi et al 2007 Small3 2019, © 2007 John Wiley & Sons.

Mentions: In addition to the solvent effect, temperature also plays a significant role in the self-assembly behaviors. Upon heating at 60 °C, the mixture of 1a in 1,4-dioxane (1.0 mM) transformed into a transparent light-brown solution, which formed aggregates composed of nanodisks after subsequent aging at 20 °C for 24 h (figure 3(a)). The nanodisks have 0.2–1.5 μm diameters and a thickness of 4.4 nm, which is in good agreement with the thickness of the alkyl chain-interdigitated bilayers (figure 3(b)) [26]. Interestingly, further cooling of the mixture from 20 °C to 5 °C and keeping at 5 °C for 12 h resulted in precipitates comprising flower-shaped assemblies several micrometers in size (3–10 μm) with crumpled sheet- or flake-like nanostructures several tens of nanometers in thickness (figures 3(f)–(g)) [29].


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
SEM (a) and atomic force microscopy (AFM) (b) images of nanodisks formed by cooling a 1,4-dioxane solution of 1a from 60 °C to 20 °C. SEM (c) image of square-shaped objects loosely rolled up in each corner formed by rapid cooling of 1,4-dioxane solution of 1a from 60 °C to 5 °C. SEM images (d), (e) of the further rolled up objects of crumpled structures at the four corners. SEM (f) and TEM (g) images of final flower-shaped assemblies of 1a precipitated by slow aging at 5 °C. Reprinted with permission from T Nakanishi et al 2007 Small3 2019, © 2007 John Wiley & Sons.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: SEM (a) and atomic force microscopy (AFM) (b) images of nanodisks formed by cooling a 1,4-dioxane solution of 1a from 60 °C to 20 °C. SEM (c) image of square-shaped objects loosely rolled up in each corner formed by rapid cooling of 1,4-dioxane solution of 1a from 60 °C to 5 °C. SEM images (d), (e) of the further rolled up objects of crumpled structures at the four corners. SEM (f) and TEM (g) images of final flower-shaped assemblies of 1a precipitated by slow aging at 5 °C. Reprinted with permission from T Nakanishi et al 2007 Small3 2019, © 2007 John Wiley & Sons.
Mentions: In addition to the solvent effect, temperature also plays a significant role in the self-assembly behaviors. Upon heating at 60 °C, the mixture of 1a in 1,4-dioxane (1.0 mM) transformed into a transparent light-brown solution, which formed aggregates composed of nanodisks after subsequent aging at 20 °C for 24 h (figure 3(a)). The nanodisks have 0.2–1.5 μm diameters and a thickness of 4.4 nm, which is in good agreement with the thickness of the alkyl chain-interdigitated bilayers (figure 3(b)) [26]. Interestingly, further cooling of the mixture from 20 °C to 5 °C and keeping at 5 °C for 12 h resulted in precipitates comprising flower-shaped assemblies several micrometers in size (3–10 μm) with crumpled sheet- or flake-like nanostructures several tens of nanometers in thickness (figures 3(f)–(g)) [29].

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.