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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 C60 derivatives 3b–3c. SEM images of the assemblies of 3b–3c formed by cooling their 1,4-dioxane solution from 70 °C to 20 °C (b); (c) Plate-Rich giant particles of 3b; (d) sheet structures of 3c. Reprinted from [40].
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Figure 6: (a) Chemical structure of C60 derivatives 3b–3c. SEM images of the assemblies of 3b–3c formed by cooling their 1,4-dioxane solution from 70 °C to 20 °C (b); (c) Plate-Rich giant particles of 3b; (d) sheet structures of 3c. Reprinted from [40].

Mentions: In addition to the solvent effect on the self-assembly of 1a–1c, which was briefly described in figure 1, the chain substitution pattern also had significant influence on the control of organized architectures. Through the same self-assembly procedures and same temperature history within the same solvent, alkylated-C60 derivatives, 3a–3c, bearing different eicosyloxy chain numbers (figures 4(a), 6(a)), formed different self-assembled structures [40]. Specifically, compound 3a appended with 3,4,5-triseicosyloxyl chains formed globular microparticles with a nanoflaked outer surface (figure 4(b)). While 3b bearing 3,4-biseicosyloxyl chains generated plate-rich giant particles (figures 6(b)–(c)). The 4-monoeicosyloxyl chain-substituted 3c, on the other hand, gave rise to sheet structures (figure 6(d)). The distinctive morphologies can be attributed to the competing π–π interactions of neighboring C60 moieties with the vdW interactions of the alkyl chains. With fewer alkyl chains, the π–π interaction of C60 moeties is richer and therefore induces plate-rich architectures due to the lower flexibility of the molecular organizations. On the other hand, with more alkyl chains, the π–π interaction of C60 moieties is constrained, resulting in a suppressed planar arrangement of C60 moeties and thus favoring globular objects with wrinkled nanoflaked outer surfaces.


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
(a) Chemical structure of C60 derivatives 3b–3c. SEM images of the assemblies of 3b–3c formed by cooling their 1,4-dioxane solution from 70 °C to 20 °C (b); (c) Plate-Rich giant particles of 3b; (d) sheet structures of 3c. Reprinted from [40].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: (a) Chemical structure of C60 derivatives 3b–3c. SEM images of the assemblies of 3b–3c formed by cooling their 1,4-dioxane solution from 70 °C to 20 °C (b); (c) Plate-Rich giant particles of 3b; (d) sheet structures of 3c. Reprinted from [40].
Mentions: In addition to the solvent effect on the self-assembly of 1a–1c, which was briefly described in figure 1, the chain substitution pattern also had significant influence on the control of organized architectures. Through the same self-assembly procedures and same temperature history within the same solvent, alkylated-C60 derivatives, 3a–3c, bearing different eicosyloxy chain numbers (figures 4(a), 6(a)), formed different self-assembled structures [40]. Specifically, compound 3a appended with 3,4,5-triseicosyloxyl chains formed globular microparticles with a nanoflaked outer surface (figure 4(b)). While 3b bearing 3,4-biseicosyloxyl chains generated plate-rich giant particles (figures 6(b)–(c)). The 4-monoeicosyloxyl chain-substituted 3c, on the other hand, gave rise to sheet structures (figure 6(d)). The distinctive morphologies can be attributed to the competing π–π interactions of neighboring C60 moieties with the vdW interactions of the alkyl chains. With fewer alkyl chains, the π–π interaction of C60 moeties is richer and therefore induces plate-rich architectures due to the lower flexibility of the molecular organizations. On the other hand, with more alkyl chains, the π–π interaction of C60 moieties is constrained, resulting in a suppressed planar arrangement of C60 moeties and thus favoring globular objects with wrinkled nanoflaked outer surfaces.

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.