Forming Kinetically-Trapped Liquid Crystalline Spherical Nanoparticles During Polymerization-Induced Self-Assembly

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Liquid crystalline nanoparticles (LC NPs) possess anisotropic structures, but their mass production and precise control over morphology and size remain challenging.
• Polymerization-induced self-assembly (PISA) is a scalable technique for synthesizing nanoparticles with diverse morphologies.
• Kinetic trapping in PISA can limit morphological transitions but also enables the creation of specific nano-objects.

Purpose of the Study:

• To synthesize kinetically-trapped diblock copolymer LC NPs using a liquid crystalline polymer (LCP) as the core-forming block.
• To investigate the effect of incorporating benzyl methacrylate (BzMA) on the birefringence of these LC NPs.
• To elucidate kinetic trapping effects during nanoparticle formation through morphological transition studies.

Main Methods:

• Synthesis of poly(2-(dimethylamino)ethyl methacrylate)-poly(6-((4-cyano-4'-biphenyl)oxy)hexyl methacrylate) (PDMA-PMA6CB) diblock copolymers via PISA.
• Characterization using small-angle X-ray scattering (SAXS) to verify polymer chain conformation.
• Polarized optical microscopy (POM) to observe birefringence and lyotropic liquid crystal behavior.

Main Results:

• PDMA-PMA6CB spherical micelles exhibited birefringence, confirming lyotropic liquid crystal behavior due to straight PMA6CB core-forming block conformation.
• Introduction of BzMA into triblock or statistical copolymers (PDMA-PMA6CB-PBzMA or PDMA-P(MA6CB-co-BzMA)) reduced or eliminated birefringence.
• SAXS data indicated disrupted radial orientation of the PMA6CB block in the core of modified nanoparticles, correlating with reduced birefringence.

Conclusions:

• This work presents an efficient PISA-based method for fabricating LC NPs with tunable birefringence.
• Control over the core-forming block's composition and orientation is crucial for achieving desired liquid crystalline properties in nanoparticles.
• The findings offer valuable insights into controlling LC NP characteristics for advanced material applications.