Oligo(p-phenylene-ethynylene)-derived super-π-gelators with tunable emission and self-assembled polymorphic...

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Electronics

Background:

• Linear π-conjugated oligomers are known to self-assemble into organogels via noncovalent interactions.
• The properties of these organogels are tunable based on molecular structure and assembly conditions.

Purpose of the Study:

• To investigate the influence of π-conjugation length on the gelation and morphological characteristics of oligo(p-phenylene-ethynylene)s (OPEs).
• To explore the role of molecule-molecule and molecule-substrate interactions in dictating self-assembly behavior.

Main Methods:

• Synthesis and characterization of OPE3, OPE5, and OPE7 with varying conjugation lengths.
• Gelation studies in nonpolar solvents to determine critical gel concentrations.
• Morphological analysis using techniques sensitive to substrate interactions (e.g., mica, silicon wafer).

Main Results:

• All OPEs formed fluorescent gels in nonpolar solvents at low concentrations, exhibiting distinct colors (blue for OPE3, green for OPE5, greenish yellow for OPE7).
• Substrate type significantly affected morphology: mica promoted interactions, leading to vesicular, fibrous, and spiral assemblies, while silicon wafers suppressed them.
• Increasing conjugation length enhanced polymorphism, with OPE7 exhibiting diverse structures controlled by substrate, concentration, and humidity.

Conclusions:

• Conjugation length is a critical factor governing the self-assembly and gelation properties of OPEs.
• The interplay between molecular structure, solvent, substrate, and environmental conditions allows for control over the formation of various supramolecular architectures.
• OPEs represent a versatile class of compounds for developing functional fluorescent organogels with tunable morphologies.