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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 structure of an ionic C60 derivative 7. (b) SEM image of flake-like microparticles of 7 precipitated by slowly adding excess methanol (MeOH) to a concentrated CH2Cl2 solution of 7; inset, a water droplet on the surface of a thin film made from the microparticles of 7. SEM images of the self-organized structures of 7 formed on Si substrates by evaporating a 0.5 mM solution in a MeOH/CH2Cl2 mixed solvent with a MeOH volume content of 0 (c), 10% (d) and 30% (e). (f) AFM image of a film obtained by spin-coating a 10 μM CH2Cl2 solution of 7 on HOPG; inset, a schematic of lamellar form of 7 on HOPG. Reprinted with permission from H Li et al 2011 Langmuir27 7493, © 2011 American Chemical Society.
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Figure 9: (a) Chemical structure of an ionic C60 derivative 7. (b) SEM image of flake-like microparticles of 7 precipitated by slowly adding excess methanol (MeOH) to a concentrated CH2Cl2 solution of 7; inset, a water droplet on the surface of a thin film made from the microparticles of 7. SEM images of the self-organized structures of 7 formed on Si substrates by evaporating a 0.5 mM solution in a MeOH/CH2Cl2 mixed solvent with a MeOH volume content of 0 (c), 10% (d) and 30% (e). (f) AFM image of a film obtained by spin-coating a 10 μM CH2Cl2 solution of 7 on HOPG; inset, a schematic of lamellar form of 7 on HOPG. Reprinted with permission from H Li et al 2011 Langmuir27 7493, © 2011 American Chemical Society.

Mentions: Our group has designed an ionic alkylated C60 derivative, 7 (figure 9(a)), which exhibited multiple morphologies with different processing methods [59]. Through liquid-liquid interfacial precipitation with the addition of a poor solvent, methanol (MeOH), on the top of a concentrated dichloromethane (CH2Cl2) solution of 7, self-organized flake-like microparticles with high roughness were produced (figure 9(b)). However, through drop-casting of a stock solution of 7 with CH2Cl2, CH2Cl2/MeOH = 9:1 and CH2Cl2/MeOH < 7:3 as solvents on a Si substrate, film with some cracks (figure 9(c)), closely packed flower-like objects (figure 9(d)) and doughnut-shaped micro-objects (figure 9(e)) with rough surfaces were generated, respectively. On the other hand, the diluted CH2Cl2 solution of 7 (10 μM), once spin-coated on HOPG, could form perfectly straight C60 nanowires in which the length of nanowires exceeded 1 μm (figure 9(f)).


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
(a) Chemical structure of an ionic C60 derivative 7. (b) SEM image of flake-like microparticles of 7 precipitated by slowly adding excess methanol (MeOH) to a concentrated CH2Cl2 solution of 7; inset, a water droplet on the surface of a thin film made from the microparticles of 7. SEM images of the self-organized structures of 7 formed on Si substrates by evaporating a 0.5 mM solution in a MeOH/CH2Cl2 mixed solvent with a MeOH volume content of 0 (c), 10% (d) and 30% (e). (f) AFM image of a film obtained by spin-coating a 10 μM CH2Cl2 solution of 7 on HOPG; inset, a schematic of lamellar form of 7 on HOPG. Reprinted with permission from H Li et al 2011 Langmuir27 7493, © 2011 American Chemical Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 9: (a) Chemical structure of an ionic C60 derivative 7. (b) SEM image of flake-like microparticles of 7 precipitated by slowly adding excess methanol (MeOH) to a concentrated CH2Cl2 solution of 7; inset, a water droplet on the surface of a thin film made from the microparticles of 7. SEM images of the self-organized structures of 7 formed on Si substrates by evaporating a 0.5 mM solution in a MeOH/CH2Cl2 mixed solvent with a MeOH volume content of 0 (c), 10% (d) and 30% (e). (f) AFM image of a film obtained by spin-coating a 10 μM CH2Cl2 solution of 7 on HOPG; inset, a schematic of lamellar form of 7 on HOPG. Reprinted with permission from H Li et al 2011 Langmuir27 7493, © 2011 American Chemical Society.
Mentions: Our group has designed an ionic alkylated C60 derivative, 7 (figure 9(a)), which exhibited multiple morphologies with different processing methods [59]. Through liquid-liquid interfacial precipitation with the addition of a poor solvent, methanol (MeOH), on the top of a concentrated dichloromethane (CH2Cl2) solution of 7, self-organized flake-like microparticles with high roughness were produced (figure 9(b)). However, through drop-casting of a stock solution of 7 with CH2Cl2, CH2Cl2/MeOH = 9:1 and CH2Cl2/MeOH < 7:3 as solvents on a Si substrate, film with some cracks (figure 9(c)), closely packed flower-like objects (figure 9(d)) and doughnut-shaped micro-objects (figure 9(e)) with rough surfaces were generated, respectively. On the other hand, the diluted CH2Cl2 solution of 7 (10 μM), once spin-coated on HOPG, could form perfectly straight C60 nanowires in which the length of nanowires exceeded 1 μm (figure 9(f)).

View Article: PubMed Central - PubMed

ABSTRACT

Organic &pi;-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 &pi; units were in most cases attached by alkyl chains through chemical modification. Considerable numbers of alkylated-&pi; 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-&pi; molecules with emphasis on the interplay of van der Waals interactions (vdW) of the alkyl chains and &pi;&ndash;&pi; interactions of the &pi; moieties. Based on our comprehensive investigations of the two interactions&rsquo; impacts on the physical states of the molecules, a clear guidance for state control by alkyl-&pi; engineering is proposed. Specifically, either with proper alkyl chain substitution or favorable additives, the vdW and &pi;&ndash;&pi; 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-&pi; chemistry toward wide-spread applications in optoelectronic devices.

No MeSH data available.


Related in: MedlinePlus