Organosilicon polymer materials play an important role in certain applications due to characteristics of much lower glass transition temperatures (T_g), viscosities, surface energy, as well as good mechanical, thermal stabilities, and insulation performance stemming from the higher bond energy and the larger bond angles of the adjacent silicon-oxygen bond. This critical review highlights developments in the synthesis, structure, and phase transition behaviors of polysiloxane-based side chain liquid crystal polymers (PSCLCPs) of linear and cyclic polysiloxanes containing homopolymers and copolymers. Detailed synthetic strategies are elaborated, and the relationship between molecular structures and liquid crystalline phase transition behaviors is systematically discussed, providing theoretical guidance on the molecular design of the materials.

Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

In this work, we prepared polymer-dispersed liquid crystal (PDLC) films with good mechanical properties, high contrast ratio (CR), and low driving voltage (V_dr). These PDLC films included two different monomers, which were hydroxyl methacrylate monomers and fluorinated methacrylate monomers. The electro-optical properties, micro-structures and mechanical properties of these films were also characterised. It was found that the hydroxyl methacrylate monomers could improve the adhesion force of the PDLC film, while fluorinated methacrylate monomers could reduce the driving voltage. In this way, the PDLC films with excellent comprehensive performance could be obtained. Compared with the original sample, the adhesion force was improved approximately 200% to 180 N/cm². The driving voltage threshold was reduced about 140% to 18.5 V. The contrast ratio was increased about 150% to 51.9. This work enlightened a novel way to improve the mechanical properties of PDLC films and promised a broader application of PDLC. Graphical Abstract

In the present paper, influence of the functionality of thiol monomers and acrylate crosslinkers, as well as crosslinker chain length on the polymer morphologies and electro-optical properties of the PDLC films, were systematically investigated. Results revealed that increasing the functionality of thiol monomers, both threshold voltage (V_th) and saturation voltage (V_sat) were increased due to the dense microstructures resulting from higher reactivity of thiol monomers. However, with increasing the functionality of acrylate monomers, V_th was increased evidently, but a relatively small rise of V_sat was found with moderate functionality monomer. Additionally, the increase in the chain length of flexible crosslinker resulted in an increase in the average size of LC droplets with a corresponding decrease in V_th and V_sat. On the whole, polymer morphology and electro-optical properties of the PDLC films can be artificially manipulated by adjusting the molecular structure of polymer matrix. A PDLC film exhibiting low driving voltage (24.0 V), moderately high contrast ratio (97.0) and fast response time (<8.0 ms), was found by employing the Pentaerythritol tetrakis (2-mercaptoacetate) (4SH), trimethylolpropane triacrylate (TMPTA) and polyethylene glycol diacrylate (PEGD 600).

In this study, a polymer dispersed cholesteric liquid crystal (PDChLC) film obtained via a one-step fabrication technique based on photopolymerization of a thiol-acrylate reaction system was prepared and characterized for the first time. The effects of the chiral dopant, the influence of thiol monomer functionality and content on the morphology and subsequent performance of the PDChLC films were systematically investigated. It was demonstrated that the addition of a small amount of chiral dopant slightly increased the driving voltage, but decreased the off-state transmittance significantly. Furthermore, scanning electron micrographs (SEM) shown that the liquid crystal (LC) droplet size decreased at first and then increased with the increasing amount of thiol monomer functionality, while increasing the thiol content increased the LC droplet size. Correspondingly, the electro-optical switching behavior was directly dependent on LC droplet size. By tuning the raw material composition, PDChLC film with optimized electro-optical performance was prepared.

In the harsh application environment, improving the mechanical properties of liquid crystal materials is a fundamental and important problem in the design of anti-counterfeit materials. In this paper, by a stepwise polymerization of first, photo-polymerization and subsequently thermal-polymerization, a coexistent polymer dispersed network was first constructed in cholesteric liquid crystal materials containing a photo-polymerizable system of urethane acrylate and a thermo-polymerizable system of isocyanate. Results revealed that the coexistent polymer dispersed network exhibited largely enhanced mechanical performance, and the networks obtained by different methods had different contributions to the enhancement of the peel strength and toughness of the composite films. Then an angular photochromic anti-fake label based on a coexistent polymer dispersed network with enhanced mechanical and apparent angular discoloration characteristics, suitable for practical applications, was successfully achieved.