Polymer Network Luquid Crystal

Polymer/liquid crystal composite film is a kind of specific optical film which has two display effects, frosted glass effect and transparent glass effect. In recent years, it has been caused the interest of many researchers and manufacturers. According to the liquid crystal proportion, it can be divided into polymer dispersed liquid crystal(PDLC) and polymer network liquid crystal(PNLC). Compared with the conventional LCD, the PDLC film has several advantages:without polarizing film and alignment layer, fast response, simple manufacturing process, energy saving and so on. Meanwhile, the reverse mode PDLC film, changed from transparent state to light scattering state by appling voltage, has more broad application prospects in display fields. It’s more suitable for display requirements that the devices maintain transparency at most time or most area. The general methods to make reverse mode PDLC film have been proposed by using cholesteric LC, dual frequency addressable LC, smetic A LC, ferroelectric LC and positive nematic LC to prepare parallel PNLC film. However, these type films are not used in real life for the lower contrast ratio.Herein, we report a new reverse mode by vertical alignment PNLC film, In this paper we designed and synthesized two monomers:2-methyl-1,4-phenylene-bis{4-[4-(acry-loyloxy) butoxy] benzoate}(Ml) with a flexible chain,4-[(4-propylphenyl) ethynyl] phenyl acrylate(M3) without a flexible chain. Monomers and negative liquid crystals can form a homogeneous solution. The polymer network formed by curing under UV light after pouring the mixture into the vertical alignment cell. The film is transparent for monomers and liquid crystal molecules still keep vertical arrangement.The monomers are both characterized by using 1HNMR、GC-MS、HPLC and DSC. The polymer monomers M1 and M3 have liquid crystal phase according to the DSC spectras and micro-texture. We observed the film microstructures by polarizing microscope and tested the photoelectric properties by 5016C photoelectric measuring instrμment. Based on the experimental results, we analyzed the effect of the monomer structure, curing time, curing temperature and monomer content on the PNLC film. In this paper, PNLC film prepared by M1 has excellent optical effect, the off state light transmittance is over 85% and on state light transmittance is low than 10%. The saturation voltage is 25 V. PNLC film prepared by monomer M3 that has only one double bond which can be polymerized has better thermal aging property.