Recent Advances in The Polymer Dispersed Liquid Crystal Composite and Its Applications

Polymer dispersed liquid crystals (PDLCs) have kindled a spark of interest because of their unique characteristic of electrically controlled switching. However, some issues including high operating voltage, low contrast ratio and poor mechanical properties are hindering their practical applications. To overcome these drawbacks, some measures were taken such as molecular structure optimization of the monomers and liquid crystals, modification of PDLC and doping of nanoparticles and dyes. This review aims at detailing the recent advances in the process, preparations and applications of PDLCs over the past six years.     

Bifunctionalized Intrinsically Microporous Polyimides with Simultaneously Enhanced Gas Permeability and Selectivity

Two novel intrinsically microporous copolyimides synthesized by condensation reaction of 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3,3′,3′‐tetramethyl‐1,1′‐spirobisindane‐5,5′‐diamino‐6,6′‐diol, and 3,5‐diaminobenzoic acid with diamine ratios of 80/20 (Co‐80/20) and 50/50 (Co‐50/50) are reported. Unexpectedly, the Co‐80/20 not only demonstrates higher microporosity (300 m² g⁻¹) than the PIM‐6FDA‐OH homopolymer (190 m² g⁻¹) but also exhibits simultaneously enhanced CO₂ permeability (from 119 to 171 Barrer) and CO₂/CH₄ selectivity (from 35 to 41) after thermal annealing at 250 °C. This higher permeability originates from enhanced diffusivity (D _CO2) and the higher selectivity results from its increased diffusion selectivity (D _CO2/D _CH4). After crosslinking at 300 °C, the Co‐80/20 exhibits an even higher CO₂ permeability (261 Barrer) and almost unchanged CO₂/CH₄ selectivity.

     

Investigations on electrical properties of poly(vinyl alcohol) doped with 1-methyl-3-n-decyl-imidazolium bromide ionic liquid

Thin films of poly(vinyl alcohol) (PVA) that are 100–500 μm thick were prepared by solution casting method. Various ratios of 1-methyl-3-n-decyl-imidazolium bromide ionic liquid [MDIM]⁽⁺⁾Br^(?), were used as dopants (plasticizers) to control the conductivity of the PVA thin films. Fourier transform infrared spectroscopy (FTIR) was used to indicate the detailed interaction of PVA with proton of the dopant in the blends. Ac impedance spectroscopy was used to investigate the impedance of the films within a frequency range of 10–10⁶ Hz as a function of temperature between 298 and 425 K. Each film with a precise doping concentration was sandwiched between two stainless–steel electrodes. The results showed that the electrical conductivity can be engineered by controlling the [MDIM]⁽⁺⁾Br^(?) doping concentration. Therefore, those films have potential to be used in flexible and cheap organic device applications.     

Mathematical analysis of the dynamics of visceral leishmaniasis in the Sudan

In this paper we develop a mathematical model to study the dynamics of visceral leishmaniasis in the Sudan. To develop this model we consider the dynamics of the disease between three different populations, human, reservoir and vector populations. The model is analyzed at equilibrium and the stability of the equilibria is analyzed. The basic reproduction number is derived, and the threshold conditions for disease elimination established. Results show that the disease can be eliminated under certain conditions. Simulations of the model show that human treatment helps in disease control, and its synergy with vector control will more likely result in the elimination of the disease.     

A general method for the spectrophotometric determination of aromatic aldehydes

Analytical and Bioanalytical Chemistry - Aromatic aldehydes and some of their binary mixtures can be determined spectrophotometrically with diphenylamine in the presence of hydrochloric acid....     

An ion-exchange method for the detection of amides,imides and anilides

Ion-exchange resins are efficient catalysts for the acid hydrolysis of amides, imides and anilides; the ammonium ion or aniline so formed can be detected by the well-known specific tests for these species. In general, the proposed tests are simpler, faster and more selective than those already available. The amounts that can be detected are of the order of 0.05–5 μg depending on the compound.