Secondary Structure in Nonpeptidic Supramolecular Block Copolymers

Area of Science:

• Polymer chemistry and materials science, focusing on synthetic macromolecules.
• Supramolecular chemistry and self-assembly principles.
• Biomimetic materials design and protein folding paradigms.

Background:

• Proteins exhibit complex secondary and tertiary structures that are challenging to replicate synthetically in polymers.
• Existing methods for creating protein-mimicking polymers often struggle with sequence control and dispersity.
• Incorporating polymers with inherent secondary structures (helices, sheets) into block copolymers offers a route to controlled 3D architecture.

Purpose of the Study:

• To develop a versatile strategy for synthesizing block copolymers that mimic protein secondary and tertiary structures.
• To utilize polymers with well-defined secondary structures (e.g., poly(p-phenylenevinylene) sheets, poly(isocyanide) helices) as building blocks.
• To achieve hierarchical assembly of these polymeric blocks through covalent and supramolecular interactions.

Main Methods:

• Ring-Opening Metathesis Polymerization (ROMP) of [2.2]paracyclophane-1,9-dienes (pCpd) to form poly(p-phenylenevinylene) (PPV) sheets.
• Synthesis of helical polymers (e.g., poly(isocyanide)s, poly(methacrylamide)s) with chiral side groups.
• Functionalization of polymer chain ends with molecular recognition units (MRUs) for supramolecular assembly.
• Utilizing reversible addition-fragmentation chain-transfer (RAFT) agents for controlled polymerization and functionalization.

Main Results:

• Demonstrated a "plug-and-play" approach to assemble block copolymers with defined secondary structures (sheets and helices).
• Successfully created triblock copolymers and complex architectures via covalent chain extension and orthogonal supramolecular assembly.
• Showcased folding in poly(p-phenylenevinylene) sheets, with preferential folding in multistranded structures, confirmed by single-molecule polarization spectroscopy.
• Maintained distinct polymer architectures throughout the complex assembly process.

Conclusions:

• The developed strategy provides an efficient route to well-characterized, higher-ordered protein-mimicking foldable polymers.
• The
• plug-and-play
• method allows for the combination of diverse polymeric secondary structures.
• This approach holds promise for extending to other polymeric folding systems and creating advanced hierarchical materials.