Transparent hydrophobic and superhydrophobic coatings fabricated using polyamide 12–SiO2 nanocomposite

Optically transparent hydrophobic and superhydrophobic coatings have been prepared using polyamide 12–SiO₂ nanocomposite (NC) on glass substrates by the spin‐coating method. The coatings have been optimized for their hydrophobicity and transparency. The transformation from hydrophobic to superhydrophobic is achieved with increase in roughness (R_a) which increases with SiO₂ content. These coatings are highly transparent in the entire visible region (400–800 nm). The influence of layer thickness on water contact angle (WCA) and optical transmittance of the coatings has been studied. Field emission scanning electron micrograph (FESEM) shows the presence of SiO₂ nanoparticles covered with polyamide homogenously on the surface and the particles are aggregated to form a rough structure. X‐ray diffraction (XRD) patterns show that the polyamide losses its crystalline structure in the composite. The preparation procedure reported here is simple and eco‐friendly. The dual nature of the coatings, that is, high transparency and superhydrophobicity in the entire visible region suggests for its potential usage in self‐cleanings, wind screen and optoelectronic applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Multi Fuzzy Fractal Theorems in Fuzzy Metric Spaces

The Hutchinson-Barnsley (HB) operators are studied for multi iterated function system in a general setting. Some existence and uniqueness results are obtained in fuzzy fractal and multi fuzzy fractal spaces. From them, we obtain our results, which generalize some recent results in the literature.     

Rovibrational spectra of bounded diatomic molecules

Spectra of a bounded diatomic molecule is studied numerically. Shifted Deng–Fan oscillator potential has been used to model the molecule. The accurate five‐point finite difference method has been used to solve the Schrödinger equation for rovibrational motion of the molecule. The energies of the bound states as well as free states of the molecule have been calculated. In addition, radial matrix elements like , n = 1, 2, and 3 have been calculated. These have been used to calculate the ‐pole static polarizabilities. The variation of bound state energies, matrix elements and ‐pole static polarizabilities with the boundary radius has also been studied. The Stark effect in case of this bounded system has also been investigated.     

Synthesis and characterization of novel benzoxazine-based arylidinyl succinimide derivatives

1,4-Benzoxazine skeleton holds substantial promise for further exploration owing to its immense pharmacological potential. In this pursuit, a series of 20 novel benzoxazine-based arylidinyl succinimide derivatives (23–42) were synthesized in moderate to good yields by the reaction of ethyl 2-(7-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl)acetate (22) with various aromatic aldehydes under Wittig reaction conditions in the presence of triphenylphosphine and ethanol. All these synthesized compounds were fully characterized from their spectral data (¹H, ¹³C, and ²D NMR, IR, UV, high-resolution mass spectroscopy (HRMS)) and further confirmed by X-ray crystallographic analysis of a representative compound (32). Antibacterial activity of obtained arylidinyl succinimide derivatives was evaluated against both Gram-positive and Gram-negative bacterial strains and were found to exhibit insignificant activity as compared to the reference.     

Quality-by-design-based development and validation of a stability-indicating UPLC method for quantification of teriflunomide in the presence of degradation products and its application to in-vitro dissolution

A systematic design-of-experiments was performed by applying quality-by-design concepts to determine design space for rapid quantification of teriflunomide by the ultraperformance liquid chromatography (UPLC) method in the presence of degradation products. Response surface and central composite quadratic were used for statistical evaluation of experimental data using a Design-Expert software. The response variables such as resolution, retention time, and peak tailing were analyzed statistically for the screening of suitable chromatographic conditions. During this process, various plots such as perturbation, contour, 3D, and design space were studied. The method was developed through UPLC BEH C18 2.1?×?100?mm, 1.7-µ column, mobile phase comprised of buffer (5?mM K₂HPO₄ containing 0.1% triethylamine, pH 6.8), and acetonitrile (40:60 v/v), the flow rate of 0.5?mL?min^?1 and UV detection at 250?nm. The method was developed with a short run time of 1?min. Forced degradation studies revealed that the method was stability-indicating, suitable for both assay and in-vitro dissolution of a drug product. The method was found to be linear in the range of 28–84?µg?mL^?1, 2.8–22.7?µg?mL^?1 with a correlation coefficient of 0.9999 and 1.000 for assay and dissolution, respectively. The recovery values were found in the range of 100.1–101.7%. The method was validated according to ICH guidelines.     

Self‐Assembly of Bolaamphiphilic Molecules

The current buzzword in science and technology is self‐assembly and molecular self‐assembly is one of the most prominent fields as far as research in chemical and biological sciences is concerned. Generally, self‐assembly of molecules occurs through weak non‐covalent interactions like hydrogen bonding, π–π stacking, hydrophobic effects, etc. Inspired by many natural systems consisting of self‐assembled structures, scientists have been trying to understand their formation and mimic such processes in the laboratory to create functional “smart” materials, which respond to temperature, light, pH, electromagnetic field, mechanical stress, and/or chemical stimuli. These responses are usually manifested as remarkable changes from the molecular (e. g., conformational state, hierarchical order) to the macroscopic level (e. g., shape, surface properties). Many molecules such as peptides, viruses, and surfactants are known to self‐assemble into different structures. Among them, glycolipids are the new entries in the area of molecules that are being investigated for their self‐assembly characteristics. Among the different classes of glycolipids like rhamnolipids and trehalose lipids, owing to their biological preparations and their structural novelty, sophorolipids (SLs) are evoking greater interest among researchers. Sophorolipids are a class of asymmetric bolas bearing COOH groups at one end and sophorose (dimeric glucose linked by an unusual β(1→2) linkage). The extreme membrane stability of Archaea, attributed to the membrane‐spanning bolas (tetraether glycolipids), has inspired chemists to unravel the molecular designs that underpin the self‐assembly of bolaamphiphilic molecules. Apart from these self‐assembled structures, bolaamphiphiles find applications in many fields such as drug delivery, membrane mimicking, siRNA therapies, etc. The first part of this Personal Account presents some possible self‐assembled structures of bolaamphiphiles and their mechanism of formation. The later part covers our work on one of the typical bolaamphiphiles known as sophorolipids.     

Nonequilibrium liquid crystalline layered phase stabilized by light

The ability of light to alter/stabilize a particular thermodynamic phase is a power tool to investigate condensed matter from a new dimension. This field of photoinduced phase transitions is currently an important area of research. Being elastically soft and having subtle changes between its many phases a liquid crystal material is an attractive medium to investigate such light-driven phase transitions. The attraction is partly due to the large birefringence changes accompanying these transitions that are useful in developing photonic devices. In all of the cases reported to date, the photoinduced transition always leads to a phase that in any case exists in the thermal cycle. Recently we reported the first exception to such an established phenomenon (Adv. Mater. 2005, 17, 2086). The guest-host ternary mixture consisting of the photoactive azobenzene guest molecules does not exhibit smectic A phase in the absence of UV radiation. However, the smectic A phase is induced and stabilized only in the presence of UV light. In this paper, we map out hitherto unexplored temperature versus UV intensity phase diagrams for various mixtures, which illustrate that light mimics, in a limited sense, the role of a thermodynamic parameter such as, for example, pressure. The threshold UV intensity required to photodrive the appearance of the smectic A phase is seen to have a strong concentration dependence. Our studies also suggest the possibility of observing a double critical point by employing the UV intensity as a fine-tuning parameter.     

Monodispersive linear supermolecules stabilizing unusual fluid layered phases

The first examples of monodisperse liquid crystalline pentamers, synthesized by covalently linking five mesogenic segments through four flexible spacers, exhibiting mono-/partially bilayered phases with unusual textures, as established by optical, calorimetric, and X-ray diffraction studies, are reported. Importantly, the two types of multifunctional pentamers, namely, unsymmetric and C2 symmetric are soluble in organic solvents and exhibit analogous electrochemical features.     

Spinodal decomposition in a model colloid-polymer mixture in microgravity

We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.     

Intra-Specific Variation of Precocene I in the Wild Population of Ageratum conyzoides L. from the Western Himalayas

JPC – Journal of Planar Chromatography – Modern TLC -