(Super)gelators derived from push-pull chromophores: synthesis, gelling properties and second harmonic generation

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Nonlinear Optics

Background:

• Organogelation is a self-assembly process that can structure molecules.
• Second Harmonic Generation (SHG) active chromophores are important for nonlinear optical applications.
• Controlling the organization of chromophores is key to developing efficient SHG materials.

Purpose of the Study:

• To utilize organogelation for the spontaneous organization of SHG-active push-pull chromophores.
• To investigate the influence of solvent properties on chromophore self-assembly and gelation.
• To prepare and characterize SHG-active xerogel materials derived from organogels.

Main Methods:

• Synthesis and characterization of three push-pull chromophores with dodecyl urea chains.
• Evaluation of organogelating properties in various solvents.
• Application of Hansen solubility parameters to correlate solvent properties with gelation behavior.
• Preparation of xerogels by solvent evaporation and characterization using optical microscopy, electron microscopy, and SHG microscopy.

Main Results:

• The synthesized chromophores exhibited diverse gelling properties, ranging from supergelation to no gelling ability.
• Hansen solubility parameters revealed clear relationships between gelled solvents and critical gelation concentrations.
• Microscopy studies demonstrated that the solvent plays a critical role in structuring the final xerogel materials.
• The resulting xerogels exhibited SHG activity, confirming successful organization of the chromophores.

Conclusions:

• Organogelation is an effective strategy for the spontaneous organization of push-pull chromophores into SHG-active materials.
• Solvent selection is paramount for controlling the self-assembly process and the resulting material's structure and properties.
• This approach provides a general method for creating functional nonlinear optical materials.