Influence of partial matrix fluorination on morphology and performance of HPDLC transmission gratings

The morphology and the electro-optical performance characteristics were investigated in holographic polymer-dispersed liquid crystal (HPDLC) transmission gratings with partially fluorinated polymer matrices. HPDLC transmission gratings were prepared using standard UV curable monomer mixtures along with mono-functional fluorinated acrylate monomers and a nematic liquid crystal, TL203. Partial fluorination of the host polymer matrices by incorporating hexafluoroisopropyl acrylate (HFIPA) or trifluoroethyl acrylate (TFEA) in the standard formulation has been found to influence the morphological and the electro-optical properties of the resulting HPDLC transmission gratings. Significant decrease in switching voltages and higher relaxation times were observed in fluorinated HPDLCs. Conversely, an addition of methyl acrylate (MA), a non-fluorinated monomer with a similar structure in the standard formulation, resulted in an increase in the switching voltage and produced no significant change in the relaxation time in the HPDLC gratings. Presence of fluorine atoms at the polymer-liquid crystal (LC) interface not only decreased the surface anchoring strength but also influenced the orientation of LC droplet directors. (C) 2002 Elsevier Science Ltd. All rights reserved.