Consecutive Complex Aggregation Pathway in Covalent Helical Polymer-Metal Complexes: Nanospheres with Controlled P/M...

Area of Science:

• Supramolecular Chemistry
• Polymer Science
• Chirality Studies

Background:

• Chiral polymers can form complex aggregates with unique properties.
• Controlling macroscopic chirality in self-assembled structures remains a challenge.
• Circularly polarized luminescence (CPL) is sensitive to chiral environments.

Purpose of the Study:

• To synthesize kinetically trapped and thermodynamic nanospheres with opposite chirality from a single helical polymer-metal complex.
• To investigate the influence of chirality and metal ions on aggregate formation.
• To characterize the stability and CPL properties of the resulting nanostructures.

Main Methods:

• Utilizing a chiral poly(diphenylacetylene) (PDPA) with a high helix inversion energy barrier.
• Employing Barium (Ba^2+) ions as crosslinking agents for the polymer.
• Analyzing aggregate formation under identical environmental conditions.
• Monitoring the evolution of aggregates over extended periods and temperatures.

Main Results:

• Successfully generated both kinetically trapped (M-chirality) and thermodynamic (P-chirality) nanospheres from the same poly-(L)-1/Ba^2+ complex.
• Demonstrated opposite macroscopic chirality and CPL in the distinct nanosphere types.
• Observed a slow kinetic evolution between aggregate forms (>75 days at room temperature), tunable by temperature.
• Confirmed the long-term stability of dispersed nanospheres for up to 8 months.

Conclusions:

• A single chiral polymer-metal complex can yield distinct nanospheres with opposite chirality and CPL.
• The high energy barrier of the polymer helix is crucial for isolating kinetic and thermodynamic aggregates.
• These findings offer new avenues for designing chiral materials with tunable optical properties.