Design of Clickable Aromatic Donor-Acceptor Pairs for Easy Installation onto Polymers

Area of Science:

• Materials Science
• Organic Chemistry
• Polymer Science

Background:

• Designing novel aromatic donor-acceptor (D-A) systems is crucial for advanced materials.
• Traditional D-A pairs like naphthalene diimide (NDI) and 1,5-dialkoxy naphthalene (DAN) have limitations in derivatization.
• Simplifying the synthesis and functionalization of D-A units is essential for broader applications.

Purpose of the Study:

• To design and synthesize new intrinsically unsymmetric aromatic donors and acceptors.
• To investigate charge-transfer complex formation and quantitatively compare new D-A pairs with existing systems.
• To demonstrate the facile incorporation of these new D-A units into polymers via click chemistry for material property modulation.

Main Methods:

• Synthesis of desymmetrized naphthalene monoimide (NMI(NO2)2) and carbazole (CBZ(OMe)2) derivatives.
• Characterization of charge-transfer complex formation using NMR and UV-visible titrations.
• Computational analysis using density functional theory (DFT) to understand electronic properties (HOMO/LUMO, electrostatic potential).
• Polymer modification via azide-alkyne click chemistry with synthesized D-A units.
• Evaluation of mechanical properties of modified polymers using nanoindentation.

Main Results:

• Successfully synthesized novel unsymmetric aromatic donors and acceptors, including NMI(NO2)2 and CBZ(OMe)2.
• The new D-A pairs exhibited significant charge-transfer complex formation, with the NMI(NO2)2-CBZ(OMe)2 pair showing an association constant (Ka) of 50 M-1.
• This Ka is comparable to or better than the benchmark NDI-DAN pair, with enhanced ease of functionalization.
• Demonstrated successful click chemistry integration of D-A units into acrylate copolymers.
• Observed influence of charge-transfer interactions on the mechanical properties of the functionalized polymers.

Conclusions:

• Developed a versatile strategy for designing and synthesizing easily functionalizable aromatic D-A building blocks.
• The new D-A pairs offer advantages in terms of synthesis, scale-up, and derivatization for supramolecular chemistry.
• These D-A units can be readily incorporated into polymers, enabling the creation of novel functional materials with tunable properties.
• The study provides a pathway for efficient design of supramolecular materials and polymers through simplified D-A unit installation.