Enhancement of dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal mixture by dispersing nano-sized copper oxide

ABSTRACT

Here, we present the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal (FLC) mixture, namely W302. The FLC mixture, comprising of pyrimidine compounds, was characterised through dielectric spectroscopy, differential scanning calorimetry (DSC), polarising optical microscopy (POM) and other electro-optical methods. The material parameters such as spontaneous polarisation, rotational viscosity, response time and tilt angle of W302 were found to be 14 nC/cm², 240 mPa.s, 150 µs and 28^?, respectively. The phase transition temperatures of W302 were observed through DSC and further confirmed by the dependence of dielectric loss factor in homogeneously aligned FLC sample with temperature. We also demonstrate the observance of a low-frequency dielectric relaxation mode due to the unwinding of the helix, called as partially unwound helical mode (p-UHM) along with Goldstone mode. The behaviour of p-UHM has been systematically studied with temperature and applied bias field. Further, dispersion of nCuO into host W302 has shown a significant increase in dielectric permittivity. Also, the p-UHM relaxation peak in the dielectric regime has disappeared with the incorporation of nCuO. These studies would be useful to fabricate better electro-optical devices for display, switching and beam steering applications. The formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W302 composed of pyrimidine compounds is presented. Then, we observed the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared and characterized FLC mixture.     

An efficient method for the synthesis of acylals from aldehydes using silica-supported perchloric acid (HClO4-SiO2)

The synthesis of acylals from structurally diverse aldehydes has been performed in excellent yields under solvent-free conditions using HClO₄-SiO₂ as a mild, convenient, reusable, and heterogeneous catalyst. The procedure is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the catalyst can be recovered simply and reused efficiently a number of times without appreciable loss of activity.     

Beaded reactive polymers 3 effect of triacrylates as crosslinkers on the physical properties of glycidyl methacrylate copolymers and immobilization of penicillin G acylase

Various glycidyl methacrylate (GMA) copolymers were synthesized by suspension polymerization, using pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TRIM) as crosslinking comonomers. These copolymers were evaluated for the immobilization of penicillin G acylase. Broad pore-size distribution that was observed was in the range 5-300 nm. Both surface area and pore volume increased with increase in the mole fraction of crosslinking comonomer (increasing crosslink density). The pore volume of the copolymers was more than doubled by including lauryl alcohol as porogen. Binding of penicillin G acylase (PGA) was quantitative on highly crosslinked copolymers. The expression of bound PGA was better on the relatively more hydrophilic GMA-TMPTA and GMA-PETA copolymer supports compared to the GMA-TRIM copolymers. Among the different copolymers studied, GMA-TMPTA copolymer 7411 exhibited highest activity of immobilized penicillin G acylase (167.4 IU/g) with 35.1% expression.     

Polymerized Lightweight Fibrous Composites

Industrial, agricultural, and naturally occurring waste materials in conjunction with liquid epoxy resin, asbestos, and silica have been employed to make lightweight engineering composite materials. To bring down the cost of epoxy resin, phenol formaldehyde was used as a binding material. Various physicomechanical properties of these composites were investigated. This study advocates elegant, economical, and lighter alternative materials for structural applications, reducing the deadweight of the structure and thereby resulting in lighter foundations. Furthermore, an attempt has been made to find a suitable fibrous material as an alternative substitute for asbestos to meet hygienic requirements.     

Lightweight Polymer Composites from Waste Materials: A Solution to Environmental Pollution

Several new lightweight polymer concretes derived from industrial, agricultural, and naturally occurring waste materials were investigated. Various physicomechanical properties of these materials were studied. Such inexpensive and lightweight polymer composites, which have properties superior to ordinary reinforced cement concrete, may find wide applications in building technology and related areas and may serve as better substitutes for cement. Furthermore, recycling of such wastes from various sources may help to solve the present environmental pollution problems.     

MK-10 Clay–Catalyzed Synthesis of 2-(2′,5′-Disubstituted-1′H-indol-3′-yl)-1H-benzo[d]imidazoles under Conventional and Microwave Irradiation

The synthesis of benzimidazoles has been achieved in a one-pot reaction in excellent yield using a newly developed methodology. 2,5-Disubstituted-3-cyanoacetyl indoles were directly condensed with substituted orthophenylenediamine via microwave irradiation under neat, solid support, and conventional conditions in a short time to afford the corresponding products in good yields. Structures of the products thus obtained were confirmed by their melting points, infrared, ¹H NMR, ¹³C NMR, and mass spectral data.

Synthesis and biological evaluation of novel triazole-biscoumarin conjugates as potential antitubercular and anti-oxidant agents

Research on Chemical Intermediates - The synthesis of a new series of triazole-biscoumarin conjugates by using a molecular hybridization approach is described. The newly synthesized compounds...     

Sodium Bisulfite as an Efficient and Inexpensive Catalyst for the One-pot Synthesis of 2,4,5-Triaryl-1<Emphasis Type="Italic">H</Emphasis>-imidazoles from Benzil or Benzoin and Aromatic Aldehydes

Summary. 2,4,5-Triaryl-1H-imidazoles were efficiently synthesized from benzoin or benzil, ammonium acetate, and aromatic or heteroaromatic aldehydes in the presence of sodium bisulfite as catalyst. The present protocol offers significant improvements for the synthesis of 2,4,5-triaryl-1H-imidazoles with regard to yield of products, simplicity in operation, and cheap catalyst.     

Acetalization of glycerol using mesoporous MoO3/SiO2 solid acid catalyst

Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO₃/SiO₂ as a solid acid catalyst. A series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%) were prepared by sol–gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively. The sol–gel derived samples were calcined at 500 °C and characterized using various physicochemical characterization techniques. The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO₃ loading and at higher loading of crystalline α-MoO₃ on amorphous silica support. TEM analyses of the materials showed the uniform distribution of MoO₃ nanoparticles on amorphous silica support. Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of α-MoO₃ and polymolybdate species at high Mo loadings. Moreover the Raman spectra of intermediate loading samples also suggest the presence of β-MoO₃. Acetalization of glycerol with benzaldehyde was carried out using series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%). Among the series, MoO₃/SiO₂ with 20 mol% MoO₃ loadings was found to be the most active catalyst in acetalization under mild conditions. Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 °C with 60% selectivity for the six-membered acetal using 20% MoO₃/SiO₂. Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals. These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process.