Broadband reflection in polymer stabilized cholesteric liquid crystal films with stepwise photo-polymerization

Area of Science:

• Materials Science
• Polymer Chemistry
• Optics

Background:

• Polymer stabilized cholesteric liquid crystals (PSCLCs) are advanced materials with tunable optical properties.
• Controlling the pitch distribution in PSCLCs is crucial for tailoring their reflection characteristics.
• Existing fabrication methods often lack precise control over non-uniform pitch distributions.

Purpose of the Study:

• To introduce a novel fabrication method for PSCLC films with non-uniform pitch distribution.
• To investigate the impact of polymerization conditions on the optical and morphological properties of PSCLCs.
• To establish a correlation between fabrication parameters, polymer network morphology, and reflective properties.

Main Methods:

• Utilized two sequential photo-induced polymerization processes.
• Leveraged the temperature dependence of a chiral dopant's helical twisting power (HTP).
• Employed scanning electron microscopy (SEM) to analyze polymer network morphology.

Main Results:

• Successfully fabricated PSCLC films with non-uniform pitch distribution.
• Demonstrated that ultraviolet (UV) light intensity and irradiation time precisely control reflection band location and bandwidth.
• Observed a clear correlation between polymerization conditions, SEM-analyzed network morphology, and the resulting reflective region.

Conclusions:

• The proposed photo-induced polymerization method offers effective control over PSCLC optical properties.
• Fabrication parameters significantly influence both the morphology of the polymer network and the material's reflectance.
• This study provides a pathway for designing advanced PSCLC materials with tailored spectral characteristics.