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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.

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(a) Chemical structures of C60 derivatives 1a–1c containing linear alkyl chains. Scanning electron microscopy (SEM) images of fibrous structures of 1a assembled from 1-propanol (b), a nanodisk of 1a formed from 1,4-dioxane (c) and a conical object of 1a assembled from a 1:1 tetrahydrofuran (THF)/H2O mixture (d). Reprinted from [26]. SEM images of disk-like sheets of 1b formed from a 2:1 2-propanol/toluene mixture (e), SEM images of self-aggregated particles of 1b obtained from a 1:2 THF/H2O mixture (f), globular aggregates of 1(c) with coarse surfaces formed from a 2:1 2-propanol/toluene mixture (g) and SEM and transmission electron microscopy (TEM) (inset) images of vesicular-spherical objects of 1c assembled from a 1:2 THF/H2O mixture (h). Parts (e)–(h) reprinted from T Nakanishi et al 2008 Thin Solid Films516 2401, © 2008 with permission from Elsevier.
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Figure 1: (a) Chemical structures of C60 derivatives 1a–1c containing linear alkyl chains. Scanning electron microscopy (SEM) images of fibrous structures of 1a assembled from 1-propanol (b), a nanodisk of 1a formed from 1,4-dioxane (c) and a conical object of 1a assembled from a 1:1 tetrahydrofuran (THF)/H2O mixture (d). Reprinted from [26]. SEM images of disk-like sheets of 1b formed from a 2:1 2-propanol/toluene mixture (e), SEM images of self-aggregated particles of 1b obtained from a 1:2 THF/H2O mixture (f), globular aggregates of 1(c) with coarse surfaces formed from a 2:1 2-propanol/toluene mixture (g) and SEM and transmission electron microscopy (TEM) (inset) images of vesicular-spherical objects of 1c assembled from a 1:2 THF/H2O mixture (h). Parts (e)–(h) reprinted from T Nakanishi et al 2008 Thin Solid Films516 2401, © 2008 with permission from Elsevier.

Mentions: Our group has reported a series of linear alkyl chain-attached C60 derivatives 1a–1c (figure 1(a)), which self-assembled into diverse well-defined 1D, 2D and 3D architectures in different organic solvents. The self-assembly of 1a appended with 3,4,5-trishexadecyloxyl chains, prepared simply by cooling a solvent mixture from 60 °C to 20 °C, gave rise to a variety of self-assembled architectures under different solvent conditions. 1D nanofibers (figure 1(b)), 2D nanodisks (figure 1(c)) and 3D cones (figure 1(d)) were obtained in 1-propanol, 1,4-dioxane and a 1:1 tetrahydrofuran (THF)/H2O mixture, respectively [26]. Similarly, with identical preparation procedures, 3,4-bishexadecyloxyl chains attached 1b formed 2D disk-like sheets in a 2:1 2-propanol/toluene mixture (figure 1(e)) and rather random 3D self-aggregated particles in a 1:2 THF/H2O mixture (figure 1(f)). The 4-hexadecyloxyl chain modified 1c created 3D globular aggregates in a 2:1 2-propanol/toluene mixture (figure 1(g)) and 3D vesicular-spherical objects in 1:2 THF/H2O mixtures (figure 1(h)) [27].


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
(a) Chemical structures of C60 derivatives 1a–1c containing linear alkyl chains. Scanning electron microscopy (SEM) images of fibrous structures of 1a assembled from 1-propanol (b), a nanodisk of 1a formed from 1,4-dioxane (c) and a conical object of 1a assembled from a 1:1 tetrahydrofuran (THF)/H2O mixture (d). Reprinted from [26]. SEM images of disk-like sheets of 1b formed from a 2:1 2-propanol/toluene mixture (e), SEM images of self-aggregated particles of 1b obtained from a 1:2 THF/H2O mixture (f), globular aggregates of 1(c) with coarse surfaces formed from a 2:1 2-propanol/toluene mixture (g) and SEM and transmission electron microscopy (TEM) (inset) images of vesicular-spherical objects of 1c assembled from a 1:2 THF/H2O mixture (h). Parts (e)–(h) reprinted from T Nakanishi et al 2008 Thin Solid Films516 2401, © 2008 with permission from Elsevier.
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Related In: Results  -  Collection

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Figure 1: (a) Chemical structures of C60 derivatives 1a–1c containing linear alkyl chains. Scanning electron microscopy (SEM) images of fibrous structures of 1a assembled from 1-propanol (b), a nanodisk of 1a formed from 1,4-dioxane (c) and a conical object of 1a assembled from a 1:1 tetrahydrofuran (THF)/H2O mixture (d). Reprinted from [26]. SEM images of disk-like sheets of 1b formed from a 2:1 2-propanol/toluene mixture (e), SEM images of self-aggregated particles of 1b obtained from a 1:2 THF/H2O mixture (f), globular aggregates of 1(c) with coarse surfaces formed from a 2:1 2-propanol/toluene mixture (g) and SEM and transmission electron microscopy (TEM) (inset) images of vesicular-spherical objects of 1c assembled from a 1:2 THF/H2O mixture (h). Parts (e)–(h) reprinted from T Nakanishi et al 2008 Thin Solid Films516 2401, © 2008 with permission from Elsevier.
Mentions: Our group has reported a series of linear alkyl chain-attached C60 derivatives 1a–1c (figure 1(a)), which self-assembled into diverse well-defined 1D, 2D and 3D architectures in different organic solvents. The self-assembly of 1a appended with 3,4,5-trishexadecyloxyl chains, prepared simply by cooling a solvent mixture from 60 °C to 20 °C, gave rise to a variety of self-assembled architectures under different solvent conditions. 1D nanofibers (figure 1(b)), 2D nanodisks (figure 1(c)) and 3D cones (figure 1(d)) were obtained in 1-propanol, 1,4-dioxane and a 1:1 tetrahydrofuran (THF)/H2O mixture, respectively [26]. Similarly, with identical preparation procedures, 3,4-bishexadecyloxyl chains attached 1b formed 2D disk-like sheets in a 2:1 2-propanol/toluene mixture (figure 1(e)) and rather random 3D self-aggregated particles in a 1:2 THF/H2O mixture (figure 1(f)). The 4-hexadecyloxyl chain modified 1c created 3D globular aggregates in a 2:1 2-propanol/toluene mixture (figure 1(g)) and 3D vesicular-spherical objects in 1:2 THF/H2O mixtures (figure 1(h)) [27].

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.


Related in: MedlinePlus