Steric ploy for alternating donor-acceptor co-assembly and cooperative supramolecular polymerization

Area of Science:

• Supramolecular chemistry
• Polymer science
• Organic chemistry

Background:

• Homo-assembly of monomers typically leads to homopolymers.
• Controlling supramolecular polymerization pathways is crucial for designing functional materials.
• Hydrogen bonding and charge-transfer interactions are key non-covalent forces in self-assembly.

Purpose of the Study:

• To investigate the effect of bulky peripheral groups on monomer assembly.
• To achieve alternating supramolecular copolymer formation.
• To control supramolecular polymerization pathways using temperature and additives.

Main Methods:

• Synthesis of amide-functionalized acceptor (A) and donor (D) monomers with varying peripheral groups.
• Spectroscopic techniques to study monomer interactions and complex formation.
• Temperature-dependent studies to determine critical assembly temperatures and polymerization mechanisms.

Main Results:

• A bulky wedge on monomer A destabilizes homo-assembly, enabling alternating copolymerization with monomer D via H-bonding and charge-transfer (CT) interactions (Ka = 31,000 M⁻¹).
• Replacing the bulky wedge with linear hydrocarbons results in H-bonding driven homopolymers of A and D.
• The supramolecular polymerization pathway of the NDI-monomer can be switched from isodesmic to cooperative using a small amount of DAN, inducing nucleation via D-A CT-complexes at higher temperatures.

Conclusions:

• Bulky peripheral groups are effective in directing alternating supramolecular copolymerization.
• Synergistic H-bonding and CT interactions lead to strong DA co-assembly.
• Temperature control and additives can precisely tune supramolecular polymerization pathways, enabling nucleation-elongation models.