Endowing single-crystal polymers with circularly polarized luminescence

Area of Science:

• Materials Science
• Polymer Chemistry
• Crystallography

Background:

• Single-crystal polymers with circularly polarized luminescence (CPL) are challenging to synthesize.
• Topochemical photopolymerization offers a route to ordered polymer structures.

Purpose of the Study:

• To develop a method for preparing single-crystal polymers with CPL.
• To investigate the transformation of CPL properties during polymerization.
• To create patterned CPL photonic heterojunctions.

Main Methods:

• Single-crystal-to-single-crystal (SCSC) topochemical photopolymerization of a chiral organic salt.
• In situ characterization using powder X-ray diffraction, single-crystal X-ray diffraction, optical microscopy, infrared, circular dichroism, and CPL spectroscopy.
• Mask-assisted photopolymerization for patterning.

Main Results:

• Monomer crystals exhibited yellow CPL (|g_lum| = 0.035, Φ = 49.7%).
• Photopolymerized crystals showed blue, inverted CPL (|g_lum| = 0.011, Φ = 14.2%).
• Patterned photonic heterojunctions with alternating CPL colors were successfully fabricated.

Conclusions:

• SCSC photopolymerization is an effective strategy for creating CPL-active crystalline polymers.
• The polymerization process leads to a significant change in CPL properties (color and handedness).
• This work opens avenues for photo-responsive chiral materials and advanced photonic devices.