Mujtaba Ellahi

The UV polymerisation temperature dependence of polymer-dispersed liquid crystals based on epoxies/acrylates hybrid polymer matrix components

Hybrid polymers, which form a combination of monomers with different reactive groups and curing mechanisms, synergistically combine the properties of the two constituent homopolymers. In this paper, polymer-dispersed liquid crystal (PDLC) films using epoxies / acrylates as hybrid polymer matrix components were prepared. The UV polymerisation temperature dependence of the microstructure and the electro-optical properties of PDLC films based on epoxies / acrylates hybrid polymer matrix had been studied. The electro-optical properties of PDLC films depend strongly on the liquid crystal (LC) domain size and morphology of PDLC films, which could be controlled by the polymerisation rate of the curable monomers and the diffusion rate of the LC molecules during the film preparation process. The polymerisation rate of the curable monomers and the diffusion rate of the LC molecules depend exponentially on the UV polymerisation temperature. Therefore, this research reports an example of methods to prepare PDLC films based on a hybrid polymer matrix and obtain PDLC films which possess good electro-optical properties.

Study of polymer-dispersed liquid crystal systems using epoxies / acrylates as hybrid polymer matrix components

Hybrid polymers, which form a combination of monomers with different reactive groups and curing mechanisms, synergistically combine the properties of the two constituent homopolymers. It will be of interest to use these monomers together, with the aim of forming polymer-dispersed liquid crystal (PDLC) systems based on a hybrid polymer network. In this paper, PDLC systems using epoxies / acrylates as hybrid polymer matrix components were prepared. The effects of the ratio of epoxy monomers and acrylate monomers on morphology and the electro-optical properties of PDLC systems were investigated. It was found that the liquid crystal domain size of the polymer network could be regulated by adjusting the ratio of epoxy monomers and acrylate monomers, and that the electro-optical properties of PDLC systems could then be optimised.

Characterization and Morphology of Polymer-Dispersed Liquid Crystal Films

The electro-optical properties and reducing morphologies of the PDLC films were strongly influenced by the chemical structure of curable diglycidyl ether (DGEBA), and tri-functional trimethylol propane triglycidyl ether (TMPTGE) significantly. Higher driven voltage and contrast ratio were achieved when the PDLC films showed a reducing morphology with suitably distributed small holes of LC droplet size. The detailed characterization and morphology of polymer network of PDLC films were analyzed by employing liquid crystal device (LCD) parameters tester, UV-VIS-NIR spectrophotometer, an Abbe Refractometer, and scanning electron microscopy (SEM). Meanwhile, for PDLCs with a certain amount of LC; the microstructure and the refractive index of polymer networks could be influenced by decreasing the composition ratio of monomers ethylene glycol diglycidyl ether (EGDE) and polyethylene glycol diglycidyl ether (PEGDE).

Controlled synthesis, phase formation, growth mechanism, and magnetic properties of 3-D CoNi alloy microstructures composed of nanorods

3-D flower like CoNi alloys nanostructures composed of nanorods have been synthesized by template free hydrothermal method at relatively low temperature (120 °C). The detailed characterizations confirm the formation of good crystalline fcc CoNi alloy, average crystallite size of 18.8 ± 1.0 nm, lattice parameter of 3.531 ± 0.01 A, and the nearly equiatomic composition (Co50Ni50). Highly uniform flower like nano structures are built up with nanorod of diameter about 100 nm and length in range of 200–400 nm. The nanorods (building blocks of flower) have single crystalline nature with [111] preferred growth direction. The concentration of NaOH plays a vital role in formation of alloys and high concentration promotes the formation of CoNi alloy at low temperature. The concentration of NaOH also affects the morphology remarkably by changing the growth/reaction rate of CoNi nanostructures and results in hollow spheres to nanoplate flower of CoNi alloys. Based on the evolution of the morphology of the products, a step wise growth mechanism is rationally proposed for flower like nanostructures by considering the effects of kinetic parameters on growth. Magnetic measurements show Co50Ni50 flower like nanostructure have high saturation magnetization, coercivity, remanent magnetization, and high effective anisotropy constant of value 101.3 emu g−1, 210.5 Oe, 16.2 emu g−1, and 4.457 × 104 J m−3 respectively. The enhancements of coercivity and effective anisotropy constant are attributed to nanoscale effects such as shape/surface anisotropy.

Electro-optical properties of PDLC films using diethylenetriamine (DETA) hardener

ABSTRACT The authors results obtained today and in previous works are summarized. The present work has been performed to investigate the effects of the structure and electro-optical (E-O) properties of epoxy resin based polymer dispersed liquid crystal (PDLC) films smart glass using Diethylenetriamine (DETA) as hardener with 4-cyano-4′-penthylbiphenyl (5CB) liquid crystal. In this study we have been prepared PDLC films by the thermal polymerization-induced phase separation (PIPS) method, with a thickness of 10.0 ± 1.0 μm controlled by a polyethylene terephathalate (PET) spacer and optimal preparation condition were 25% and 30% 5CB LC, respectively, with a curing time 7 hours at 70°c temperature. In addition, PDLC films were prepared with different amounts of DETA to investigate the best ratio of the hardener. Results showed that when the weight ratio of LC 5CB was 30% in PDLC and mol 3% of DETA hardener, then dispersed state of LC were well proportioned, and the variation of transmittance reached the highest value. The optical characterization of the PDLC film indicates an improvement of the angular transmission of visible light. Meanwhile, it is examined that by adjusting the mol% of hardener and LC 5CB content possesses good E-O properties with a low energy efficient method for preparing PDLC smart glass display technology.