Presence Of Polymeric Additives Research Articles

Melt Crystallization of Indomethacin Polymorphs in the Presence of Poly(ethylene oxide): Selective Enrichment of the Polymer at the Crystal-Liquid Interface.

Additives have been known to influence the crystallization behavior of amorphous pharmaceuticals. In this study, the semicrystalline polymer, poly(ethylene oxide) (PEO), exhibited a different impact on the crystal growth kinetics of indomethacin (IMC) polymorphs grown from the melt. Polarized light microscopy and Raman microscopy were employed to reveal the differences in phase separation occurring at the crystal-liquid interface of IMC polymorphs in the presence of PEO. It was found that at the same condition of melt crystallization PEO could be significantly enriched at the crystal growth front of IMC γ and α forms but not at that of the δ form. The local content of PEO at the growth front was proposed to correlate with the solubility of IMC polymorphs in the molten PEO. The distinct drug-polymer distribution at the crystal-liquid interface of IMC polymorphs could have different impacts on the thermodynamic and kinetic factors in the process of crystallization, resulting in different enhancements of crystal growth rates for the polymorphs. This study is beneficial to understanding the crystallization behavior of polymorphic drugs in the presence of polymeric additives, and more attention needs to be focused on the interfacial phenomena during crystal growth.

Insights to the action of additives for stabilization of ultrafine particles of Fenofibrate in aqueous suspensions produced by Sonoprecipitation

Sonoprecipitation of Fenofibrate (FNB) was carried out in the presence of polymeric additives and surfactants. The particle size and morphology was found to be significantly affected by the mixing conditions and the type of additives used. In order to understand the mechanism by which the additives affect FNB particle growth and morphology, intermolecular interactions between the additive and FNB crystal surfaces were modeled. Among the additives used, Tween 80 was found to be a great habit modifier. Hydrogen bonding interactions between Tween 80 and FNB molecules exposed on the (010) face of FNB particles leads to a needle-like morphology. The experimental and modelling studies indicate that hydroxyl propyl methyl cellulose (HPMC) and bovine serum albumin (BSA) show stronger crystal growth inhibition effect and provide better stabilization compared to polyvinyl pyrolidone (PVP) and Tween 80. FNB particles precipitated with ultrasound and additives were found to exhibit faster drug release profiles compared to the particles precipitated without ultrasound but in the presence of additives.

Silver decorated alpha-manganese oxide nanostructured electrocatalyst for rechargeable lithium–oxygen battery

Ag decorated α-MnO2 nanorods are studied as a cathode catalyst for rechargeable lithium–oxygen battery (LOB). The composites are synthesized by in-situ composite technique in the presence of polymeric additives and characterized by SEM, XPS, and FT-IR. The battery with Ag decorated α-MnO2 nanorod composite electrode shows an initial discharge capacity of 793mAhg−1(electrode), with reversible charge capacity of 778mAhg−1(electrode), while battery with only α-MnO2 has discharge capacity of 510mAhg−1(electrode) and charge capacity of 504mAhg−1(electrode). No Li2O or Li2O2 can be detected after discharge and Li2CO3 is the main discharge product, which suggests that the decomposition of organic carbonate electrolyte occurs during discharge.

Silver decorated beta-manganese oxide nanorods as an effective cathode electrocatalyst for rechargeable lithium–oxygen battery

Abstract In this paper, Ag nanoparticles decorated β-MnO2 nanorods are studied as cathode catalyst for rechargeable lithium–oxygen battery (LOB). β-MnO2 nanorods are prepared using a simple hydrothermal method based on MnO4− and the decoration of Ag nanoparticles is performed by in-situ composite technique in the presence of polymeric additives. The as-prepared materials are characterized by XRD, TEM, XPS, BET and Raman spectrum. Electrochemical charging and discharging capacity of β-MnO2 and Ag/β-MnO2 electrodes are investigated at the current density of 0.02 mA cm−2 in the voltage window of 2.0–4.0 V. LOB with Ag/β-MnO2 electrode shows an initial discharge capacity of 873 mA hg−1(electrode), with reversible charge capacity of 811 mA hg−1(electrode) while battery with only β-MnO2 has discharge capacity of 541 mA hg−1(electrode) and charge capacity of 445 mA hg−1(electrode). Ag/β-MnO2 nanocomposite electrode shows good rate capability and cycle stability. After 10 cycles, the capacity of 742 mA hg−1(electrode) is still retained at the current density of 0.02 mA cm−2 while only 219 mA hg−1(electrode) is retained at 0.5 mA cm−2. The capacity retention rate is 84.9% and 70.2% at 0.02 and 0.5 mA cm−2, respectively. During discharging, Li2O is the main discharge product and no Li2CO3 is formed. The results show that the electrochemical performance of β-MnO2 is greatly enhanced when Ag nanoparticles are introduced. And it is highly effective for decreasing the charging potential close to the theoretical value. Ag nanoparticles can enhance the electronic conductivity of the network. The study confirms that Ag/β-MnO2 catalyst is a promising effective catalyst for LOB.

Impact of polymers on the precipitation behavior of highly supersaturated aqueous danazol solutions.

The phase behavior of supersaturated solutions of a relatively hydrophobic drug, danazol, was studied in the absence and presence of polymeric additives. To differentiate between phase separation to a noncrystalline phase and phase separation to a crystalline phase, an environmentally sensitive fluorescent probe was employed. Induction times for crystallization in the presence and absence of polymeric additives were studied using a combination of ultraviolet and fluorescence spectroscopy. It was found that, when danazol was added to aqueous media at concentrations above the amorphous solubility, liquid-liquid phase separation was briefly observed prior to crystallization, resulting in a short-lived, drug-rich noncrystalline danazol phase with an initial size of around 500 nm. The addition of polymers was found to greatly extend the lifetime of the supersaturated two phase system, delaying the onset of crystallization from a few minutes to a few hours. Below a certain threshold danazol concentration, found to represent the amorphous solubility, only crystallization was observed. Thus, although the addition of polymers was unable to prevent danazol from precipitating once a threshold concentration was exceeded, they did inhibit crystallization, leading to a solution with prolonged supersaturation. This observation highlights the need to determine the structure of the precipitating phase, since it is linked to the resultant solution concentration time profile.

Filler engineering for papermaking: Comparison with fiber engineering and some important research topics

Fibers and fillers are important raw materials for the preparation of paper products. Similar to fiber engineering, filler engineering for papermaking has become an active research area. There are similarities as well as differences between engineering involving each of these classes of materials. There are differences in such aspects as the nature of materials to be engineered, applicable engineering methods, and engineerablity of the material surfaces. The co-development of fiber engineering and filler engineering can potentially provide many benefits to the papermaking industry. For filler engineering, the relevant research topics broadly can include fibrous filler engineering, hollow/porous filler engineering, acid-stabilization of calcium carbonate fillers, surface encapsulation of naturally occurring polymers or their derivatives, preflocculation, precoagulation, cationic modification, filler/size hybrid formation, organic filler engineering, using combinations of different types of available fillers, multilayer deposition modification, modification with polymer latexes or dispersants, physical modification, mechanical modification, surface functionalization, fines-filler composite/hybrids or fiber-filler composite/ hybrid formation, in-situ polymerization modification, surface grafting, physical treatment in the presence of polymeric additives, filler precipitation, and core-shell composite filler engineering.

Effect of water-soluble polymeric additives on energy expenditure in transportation of water-oil systems in turbulent mode

New installation of the circulation type was used to perform a joint analysis of rheological and energy parameters of turbulent flows of water and water-oil media in the presence of polymeric additives of anionic copolymers of acrylamide. Copolymers with varied molecular mass were produced by ultrasonic destruction of a starting high-molecular-weight sample of the polymer under mild conditions. The effect of the molecular mass of the polymer additive on the specific energy expenditure in the case of circulation of water-oil media in the turbulent mode was analyzed.

Reaction phase diagram of pseudo four components Li-Ni-Co-Ti oxides by combinatorial technology

The control of crystal growth and morphology of crystal is considerable importance in industrial crystallization and biomineralization. The formation of scales which is affected by temperature, stirring and supersaturation, reduce the heat transfer efficiency of the evaporation process leading to increased energy consumption and losses in production time. The removal of these scales is not only costly but also time consuming because of the tenacious nature of the scales. So, by using polymeric additives it is possible to overcome these industrial problems. In this study, the effects of polyethyleneglycol methacrylate-co-vinylsulfonic acid graft copolymers and vinylsulfonic acid homopolymer additives on the crystallization of calcium oxalate monohydarate have been investigated at different temperatures. Calcium oxalate (CaOx) crystals with different morphologies and phase structures were prepared by precipitation reaction of sodium oxalate with calcium chloride in the absence and presence of polymeric additives. The effect of polymers on the rate of precipitation of calcium oxalate has been determined by recording the decrease of solution conductivity as a function of time. Addition of vinylsulfonic acid homopolymer in a CaOx crystallization system promoted the formation of COD (calcium oxalate dihydrate) respectively, graft copolymers and homopolymer modified the crystal size of COM and COD, the extent of which was dependent on the concentrations of polymeric additives. .

Architectural Control of Hierarchical Nanobelt Superstructures in Catanionic Reverse Micelles

BaXO4 (X = Mo, W) nanobelts and a variety of hierarchical superstructures assembled from the nanobelts have been synthesized in a catanionic reverse-micelle system. The effects of various factors, such as the mixing ratio (r) between the anionic and cationic surfactants, the temperature, and the presence of polymeric additives, on the formation of the nanobelts and their hierarchical assembly have been examined in detail. In particular, r has been shown to be powerful in modulating the formation and assembly of the BaMoO4 and BaWO4 nanobelts. Architectural control of the penniform nanobelt superstructures has been readily achieved by changing the experimental parameters. A plausible two-stage growth mechanism has been proposed for the formation of penniform BaXO4 nanobelt superstructures in catanionic reverse micelles.

In Situ Monitoring of Calcium Carbonate Polymorphs during Batch Crystallization in the Presence of Polymeric Additives Using Raman Spectroscopy

Polycarboxylic acids are well-known to affect calcium carbonate crystallization. Agarwal et al. (Ind. Eng. Chem. Res. 2003, in press) reported previously the synthesis of polymaleimide by a variety of techniques and initiators. In the present work, the effect of these polymers on calcium carbonate crystallization was studied by a variety of techniques. Crystallization experiments were carried out in a 1-L LABMAX automated batch reactor, and the concentration of calcium in solution was determined in real time. Raman spectroscopy was used to determine the relative amount of various calcium carbonate polymorphs as the crystallization occurred. However, Raman spectroscopy is a scattering technique, which may make it surface selective, and therefore results from solids may not be representative of bulk of sample. X-ray diffraction (XRD) was used to compare the results obtained by Raman spectroscopy. Peak intensity ratios were used for both Raman spectroscopy and XRD for calibration and measurement purposes. Th...

Morphological evolution of barium titanate synthesized in water in the presence of polymeric species

The synthesis of barium titanate (BaTiO3) was investigated in water at 90 °C in the presence of polymeric additives. Homopolymers (polyacrylic acid) and block copolymers (polyethylene oxide-block-polymethacrylic acid) were added during synthesis to influence particle morphology and size distribution. The polymers affected the morphological evolution of the forming powder by adsorbing preferentially on specific planes. The polymeric species additionally slowed the formation of barium titanate. The barium concentration also changed the morphology, particle size, and other powder characteristics.

Attrition Grinding of Coal in the Presence of Polymeric Additives

Abstract The effect of poly(acrylic acid), poly(acrylamide), and poly (vinyl alcohol) on the attrition grinding of Illinois No. 6 coal was examined. The grinding efficiency was significantly increased by poly(acrylic acid), slightly decreased by poly(acrylamide), and unaffected by poly(vinyl alcohol). The beneficial effect of poly(acrylic acid) was most pronounced when it was used as an additive in a 55% solids slurry. The beneficial effect decreased with increasing grinding time and was most effective at lower pH values where the poly(acrylic acid) existed in the acid or partially neutralized form. When the mixture of coal slurry plus poly(acrylic acid) was neutralized with alkali to pH 6.62, the beneficial effect disappeared. Subsequent froth flotation, using kerosene and MIBC, of coal ground with poly(acrylic acid) was essentially unaffected by the presence of the additive. Some potential economic advantages of using poly(acrylic acid) as a grinding aid are pointed out.