Color-shifting Crystalline Colloidal Arrays from Polymers With Upper Critical Solution Temperature

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Crystalline colloidal arrays (CCAs) with thermoresponsive structural iridescence are valuable for various applications.
• Existing research primarily focuses on lower critical solution temperature (LCST) materials, leaving upper critical solution temperature (UCST) counterparts unexplored.

Purpose of the Study:

• To synthesize and characterize novel core-shell microspheres utilizing a UCST polymer for thermoresponsive CCAs.
• To investigate the tunable iridescence and temperature-sensing capabilities of these UCST-based CCAs.

Main Methods:

• Synthesis of core-shell microspheres using poly(N-acryloyl glycinamide) (PNAGA), a UCST homopolymer, and copolymerization with acrylamide (AM) for soft shells.
• Assembly of microspheres into CCAs and characterization of their structural iridescence governed by Bragg's law.
• Evaluation of the thermoresponsive behavior and temperature-sensing properties of the CCAs around 14°C.

Main Results:

• Successfully synthesized core-shell microspheres with soft shells capable of forming iridescent CCAs.
• Demonstrated that diffraction wavelength is dependent on concentration, observation angle, and temperature due to UCST properties and Bragg's law.
• Observed significant red shift and increased diffraction peak intensity upon heating, indicating shell swelling and transition to a soft state.

Conclusions:

• The study introduces the first use of UCST polymers for thermoresponsive CCAs, expanding their application potential.
• The developed CCAs exhibit tunable iridescence and a distinct thermoresponsive transition around 14°C.
• These findings highlight the potential of UCST-based CCAs as intelligent temperature-sensing materials.