INTERACTIONS BETWEEN POLYVINYLPYRROLIDONE AND CATIONIC GEMINI/CONVENTIONAL SURFACTANTS

The interactions of two gemini surfactants (16-s-16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) with polyvinylpyrrolidones (PVP K15 and PVP K90) were investigated using conductivity, steady-state fluorescence, and viscosity techniques. The results indicate that there is no PVP/CTAB complex formation if molecular weight of PVP < 15,000. Both PVP K15 and PVP K90 interact with gemini surfactants. The critical aggregation concentration (cac) and critical micelle concentration (cmc) increase with polymer concentration and do not depend on the polymer molecular weight. Fluorescence study shows that the addition of PVP results in a decrease of the aggregation number in all the systems investigated due to the adsorption of the PVP chain in the micelle palisade layer and the ensuing increase of micelle ionization. The viscosity results suggest that the interactions between the surfactants and the polymer affect both inter-polymer-polymer association and chain expansion.

[Supplementary materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resources: additional data tables and figures.]     

Spectroscopic analysis of Nd3+(4f3) absorption intensities in a plastic host (HEMA)

Spectroscopic and laser properties of Nd³⁺ embedded in a 2‐hydroxyethyl methacrylate (HEMA) solid plastic host are characterized. The Judd–Ofelt model has been applied to the room temperature absorption intensities of Nd³⁺(4f³) transitions in HEMA to determine the three phenomenological intensity parameters: Ω₂, Ω₄ and Ω₆. The intensity parameters are then utilized to determine the radiative decay rates (emission probabilities of transitions) and branching ratios of the Nd³⁺(4f³) transitions from the upper manifold state ⁴F_3/2 to the lower‐lying multiplet manifolds ⁴I_J′. The predicted decay rates and branching ratios of the Nd³⁺(4f³) inter‐manifold transitions in HEMA are compared with those in other laser host media. From the radiative decay rates, the radiative lifetime of the Nd³⁺⁴F_3/2 excited state is determined. Copyright © 2004 Society of Chemical Industry     

Synthesis and Characterization of Pindolol Imprinted Polymer

Molecularly imprinted polymers (MIPs) are capable of recognizing a particular molecule in presence of others due to the selective cavities on it and thus are known as plastic antibodies. Pindolol (PDL) is a synthetic beta-adrenergic receptor blocking agent and widely used for the treatment of hypertension, cardiac arrhythmia and angina pectoris. Using a combinatorial method PDL imprinted polymers were prepared with three functional monomers viz., itaconic acid, 4-vinylpyridine and methacrylic acid by thermal initiated bulk polymerization technique using ethylene glycol dimethacrylate, 2, 2′-azobisisobutyronitrile and acetonitrile as crosslinker, initiator and solvent respectively. Among the three, PDL-itaconic acid MIP shows the best binding capacity. The PDL imprinted polymer was characterized by FTIR spectra and morphology was studied by SEM images. The binding parameters of MIP and non-imprinted polymer (NIP) were compared by the Freundlich and Langmuir adsorption isotherms.     

Growth and characterization of pure and metal ions-doped l-Taurine: a third-order nonlinear optical crystal for photonic applications

Journal of Materials Science: Materials in Electronics - Pure and 1, 3, 5&nbsp;mol% of nickel- and cobalt-doped l-Taurine (LT) crystals were grown by a slow evaporation method. Diffraction...     

Analysis of thermal behavior of moving longitudinal porous fin wetted with water‐based SWCNTs and MWCNTs

In this study, the consequences of natural convection and radiation on longitudinal porous fin are scrutinized numerically. Here, the fin is moving and is wetted with nanoliquid containing single‐walled carbon nanotubes and multiwalled carbon nanotubes. Darcy's model is employed in modeling the present physical phenomenon. The derived steady‐state energy equation has been solved numerically via the Runge‐Kutta‐Fehlberg fourth‐fifth‐order method. The impact of significant parameters on the thermal performance of the wet fin has been illustrated through graphs for both types of carbon nanotubes. The comprehensive study of carbon nanotubes explores that better heat transfer from a wet fin can be achieved in the case of multiwalled carbon nanotubes.     

Morphological changes in epoxy resin (DGEBA/TETA) exposed to low temperatures

Abstract

Epoxy resin (DGEBA/TETA) is commonly used as an adhesive material. When this material is subjected to low temperatures for an extended period of time, it undergoes changes in inter/intramolecular vibrations which has been probed in this research through a combination of terahertz spectroscopy, differential scanning calorimetry and infrared spectroscopy. Distinctive morphological changes of the virgin material are observed for the exposed material at cold temperature which can be attributed to incomplete reversibility of segmental as well as entire molecular chain mobility.     

Optimisation of Inclusion Chemistry by Improved Steel Cleanliness and Optimum Calcium Treatment

SMSII, Bokaro Steel Plant produces ~ 2.0 million tons of low carbon aluminium killed (LCAK) steels per annum. Calcium treatment is done regularly at the end of ladle treatment to avoid clogging of submerged entry nozzles (SEN). With calcium consumption of 0.23 kg/t, inconsistent calcium in steel, SEN clogging and slide gate erosions were reported. Nozzle clogging during casting of LCAK steels was primarily caused by deposition of complex oxide and sulfide inclusions and slide gate erosion by excess calcium in steel. Optimum calcium in steel was essential to achieve desired inclusion composition conducive to smooth casting and eliminate slide gate or SEN erosion effectively. With calcium consumption of 0.12kg/ton optimum calcium content in steel could be achieved through i) improved steel cleanliness, ii) restricted CaS formation and iii) optimum aluminium content in steel. Process optimisation resulted in reduction in aluminium consumption by 1.0 kg/t and improvement in steel cleanliness with consistent total oxygen level of ≤ 42 ppm. Desired inclusion characteristics conducive to longer sequence length was achieved and evidenced through EPMA. Erosion of slide gate plates could be eliminated completely.     

Effect of simulated reclamation treatments on chemical properties and nitrogen mineralising characteristics of saline and alkali soils from West Pakistan

Nitrogen mineralisation and nitrification during incubation of alkali, saline-alkali, highly saline and moderately saline soils were studied in the laboratory before and after simulated reclamation treatment, in which water plus calcium sulphate were used for the two alkali soils and water alone for the two saline soils. The reclamation processes reduced exchangeable sodium and soluble salts to low levels. Mineral nitrogen accumulation during incubation of original and ‘reclaimed’ soils was accounted for entirely as nitrate. The ‘reclaimed’ soils showed a lag phase in mineral nitrogen accumulation. The moderately saline soil was the only one to show increased mineralisable nitrogen, whilst the alkali and saline-alkali soils, in particular, and the highly saline soil showed reduced mineralisable nitrogen after ‘reclamation’.     

Preparation and characterization of oriented III–V nitride thin films by nebulized spray pyrolysis

Thin films of GaN, InGaN, AlGaN and AlN on Si(1 0 0) as well as on Al₂O₃(0 0 0 1) single crystalline substrates have been deposited at 1123, 1023, 1173 and 1173 K, respectively, by employing the simple inexpensive technique of nebulized spray pyrolysis. GaN films deposited on Si are polycrystalline where as the films deposited on Al₂O₃ are epitaxial. GaN epitaxial films show cathodoluminescence characteristics. Photoluminescence studies show that all the films are of high quality.