Low-voltage-driven and highly-diffractive holographic polymer dispersed liquid crystals with spherical morphology

It is a constant pursuit to form highly-diffractive and low-voltage-driven holographic polymer dispersed liquid crystals (HPDLCs) for meeting the requirements of practical applications. Nevertheless, the highvoltage-driven characteristic is usually given while improving the diffraction efficiency of HPDLCs, and it remains a challenge to form HPDLCs with concurrent features of high diffraction and low driving voltage via a simple method. In this work, we synthesize a non-room-temperature LC, 4-butyloxy-4'-cyanobiphenyl (4OCB), and mix it with a room-temperature nematic LC mixture named P0616A. These new LC mixtures are then homogeneously mixed with monomers and a photoinitibitor composed of 3,3'-carbonylbis(7-diethylaminocoumarin) (KCD) and N-phenylglycine (NPG), followed by patterning via laser interference, generating well-structured HPDLCs. The introduction of 4OCB into the standard formulation is found to be able to optimize the morphology and electro-optical properties of the resulting HPDLC transmission gratings. By doping 5 wt% of 4OCB into the HPDLCs, a high diffraction efficiency of 92 +/- 3% is obtained; meanwhile, the threshold and saturated voltages significantly decrease by 80.8% (i.e., from 12.0 +/- 0.8 to 2.3 +/- 0.9 V mu m(-1)) and 73.2% (i.e., from 19.0 +/- 0.6 to 5.1 +/- 0.7 V mu m(-1)), respectively, in comparison with the pristine. The enhanced performance is believed to be ascribed to the formed larger LC droplets (70 +/- 20 nm) and lower interface anchoring strength (0.7 mu N m(-1)) of the polymer network on LCs.