Absence Of Polymer Research Articles

ω-Carboxyl terminated cellulose esters are effective crystallization inhibitors for challenging drugs

Polymeric additives are widely used to delay drug crystallization from supersaturated solutions, which is critical for enhancing oral bioavailability by amorphous solid dispersion (ASD). The efficacy of these polymers relies on their capacity to inhibit nucleation and subsequent crystal growth. Drug nucleation is pivotal to crystallization; therefore, effective polymers are essential for suppressing nucleation from supersaturated solutions. We studied the performance of cellulose ω-carboxyalkanoates designed as crystallization inhibitors by measuring their influence on nucleation induction times of poorly soluble drugs celecoxib, posaconazole, and enzalutamide, from supersaturated solutions. In the absence of polymers, crystallization occurred within 5 to 15 minutes for all three drugs. Polymer hydrophobicity strongly influenced effectiveness in crystallization inhibition. Hydrophobic polymers prolonged induction times for up to 8 hours, while hydrophilic polymers were less effective, except for cellulose acetate glutarate (CA1.18-GA1.21; degrees of substitution acetate 1.18, glutarate 1.21). The cellulose ω-carboxyalkanoates had glass transition temperatures well above 100 °C, outstanding for ASD stability requirements. We investigated the impact of these designed polymers on surface tension and found that it only weakly influenced crystallization inhibition. Among the nine crafted cellulose derivatives, water-soluble CA1.18-GA1.21 emerged as a highly promising ASD polymer, preventing crystallization for 2-8 hours for all fast-crystallizing model compounds.

Optimization on self-assembled ultra-micro foam system for carbon dioxide flooding

Given the problem that the conventional foam injection and salt resistance are poor, the oil displacement effect is not obvious, and it is difficult to enhance oil recovery in the ultra-low permeability and high salinity reservoirs of Yanchang Oilfield, it is imperative to study a new foam flooding agent. Based on the surfactant’s self-assembled properties, foaming agent, stabilizer and complexing agent were screened in the absence of polymer and non-alkali. Three sets of self-assembly worm-like micelle systems were screened, and then a set of carbon dioxide foaming system was selected through comparative analysis: 0.50 wt% EAPMAC-12 + 0.20 wt% SDS + 0.09 wt% TEOA + 0.08 wt% EDTA. Under this condition, its viscosity, foaming volume, foam half-life and foam composite index are 18.8 mpa·s, 531 mL, 25 min and 9956 mL·min, respectively. Under the condition of the ratio of gas to liquid 3:1, the ultra-micro foam was obtained by gas–liquid co-injection in the sand pack, and the foam was round rather than the traditional pentagonal or hexagonal shape and the size was 5–31 um, indicating that the foam had good injection. Oil displacement experiment showed the average enhanced recovery rate was 12.84 % in ultra-low permeability cores, indicating that the foam had good oil displacement effect in ultra-low permeability reservoirs.

Poly(glutamic acid)-Based Viscosity Reducers for Concentrated Formulations of a Monoclonal IgG Antibody.

Above a concentration threshold, the viscosity of solutions of proteins increases abruptly, which hampers the injectability of therapeutic formulations. Concentrations above 200 g/L are an ideal goal for subcutaneous application of antibodies. Molecular additives, such as amino acids (e.g., arginine) help decrease the viscosity, but they are used at concentrations as high as about 200 mmol/L. We addressed the question of whether poly(amino acids) could be more efficient than small molecular additives. We observed marked fluidification of a model therapeutic monoclonal antibody (mAb) solution by poly(d,l-glutamic acid) and poly(l-glutamic acid) derivatives added at concentrations of <6.5 g/L (i.e., a mAb/polymer chain molar ratio between 4:1 and 1:1 mol/mol). The bare poly(glutamate) parent chains were compared with polyethylene glycol-grafted chains as PEGylation is a common way to enhance stability. Viscosity could be decreased to ∼20 mPa s as compared to values of ∼100 mPa s in the absence of polymers at 200 g/L mAb. Formation of complexes between the mAb and the polyglutamates was characterized by capillary electrophoresis analysis in dilute solutions (1 g/L mAb) and by observation of phase separation at higher concentrations, suggesting tight association at about 2:1 mol/mol mAb/polymer. Altogether, these results show that polyglutamate derivatives hold an untapped potential as an excipient for fluidification of concentrated protein solutions.

Atomic Force Microscopy of Hydrolysed Polyacrylamide Adsorption onto Calcium Carbonate.

In this work, the interaction of hydrolysed polyacrylamide (HPAM) of two molecular weights (F3330, 11-13 MDa; F3530, 15-17 MDa) with calcium carbonate (CaCO3) was studied via atomic force microscopy (AFM). In the absence of polymers at 1.7 mM and 1 M NaCl, good agreement with DLVO theory was observed. At 1.7 mM NaCl, repulsive interaction during approach at approximately 20 nm and attractive adhesion of approximately 400 pN during retraction was measured, whilst, at 1 M NaCl, no repulsion during approach was found. Still, a significantly larger adhesion of approximately 1400 pN during retraction was observed. In the presence of polymers, results indicated that F3330 displayed higher average adhesion (450-625 pN) and interaction energy (43-145 aJ) with CaCO3 than F3530's average adhesion (85-88 pN) and interaction energy (8.4-11 aJ). On the other hand, F3530 exerted a longer steric repulsion distance (70-100 nm) than F3330 (30-70 nm). This was likely due to the lower molecular weight. F3330 adopted a flatter configuration on the calcite surface, creating more anchor points with the surface in the form of train segments. The adhesion and interaction energy of both HPAM with CaCO3 can be decreased by increasing the salt concentration. At 3% NaCl, the average adhesion and interaction energy of F3330 was 72-120 pN and 5.6-17 aJ, respectively, while the average adhesion and interaction energy of F3530 was 11.4-48 pN and 0.3-2.98 aJ, respectively. The reduction of adhesion and interaction energy was likely due to the screening of the COO- charged group of HPAM by salt cations, leading to a reduction of electrostatic attraction between the negatively charged HPAM and the positively charged CaCO3.

Structure of Cellulose Ether Affected by Ionic Surfactant and Solvent: A Small-Angle Neutron Scattering Investigation.

Polysaccharides and their derivatives are commonly used in pharmaceutical and agricultural formulations as rheology modifiers. Their performance is related to their conformation in solution, which in turn is affected by other ingredients present in the formulation. This study focuses on modulating the conformation of relatively rigid cellulose chains in aqueous solutions. In particular, we have investigated the nonionic cellulose derivative ethyl(hydroxyethyl)cellulose (EHEC) in water in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and/or ethanol acting as modulating agents. We have used small angle neutron scattering (SANS) with contrast variation to determine the EHEC chain conformation in the presence of (but not masked by) ethanol and SDS. In dilute and semidilute aqueous solutions, EHEC exhibits worm-like chain conformation due to the rigid cellulose backbone. Addition of ethanol does not impact the polymer conformation to a great extent. Addition of SDS alters the EHEC chain conformation, resulting in polyelectrolyte-like scattering behavior due to repulsive interactions between bound charged micelles which show similar structure as the free SDS micelles in solution (in the absence of polymers). Ethanol affects the polymer + surfactant system primarily by acting on the surfactant (bound on polymer) which, in turn, affects the polymer conformation. At higher ethanol concentrations (20 wt %), EHEC regains the worm-like chain conformation because of the detachment of the bound SDS micelles. To the best of our knowledge, this is the only study providing details on chain conformation of the rigid polymer EHEC in dilute or semidilute aqueous solutions in the presence of surfactant and alcohol and one of very few papers utilizing SANS for the characterization of polymer + surfactant + water + alcohol interactions. Such fundamental understanding of interactions and structure in multicomponent mixtures supports the design of industrial formulations.

Effect of polymer/surfactant complexation on diffusiophoresis of colloids in surfactant concentration gradients

HypothesisA concentration gradient of surfactants in the presence of polymers that non-covalently associate with surfactants will exhibit a continually varying distribution of complexes with different composition, charge, and size. Since diffusiophoresis of colloids suspended in a solute concentration gradient depends on the relaxation of the gradient and on the interactions between solutes and particles, polymer/surfactant complexation will alter the rate of diffusiophoresis driven by surfactant gradients relative to that observed in the same concentration gradient in the absence of polymers. ExperimentsA microfluidic device was used to measure diffusiophoresis of colloids suspended in solutions containing a gradient of sodium dodecylsulfate (SDS) in the presence or absence of a uniform concentration of Pluronic P123 poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) nonionic triblock copolymers. To interpret the effect of P123 on the rate of colloid diffusiophoresis, electrophoretic mobility and dynamic light scattering measurements of the colloid/solute systems were performed, and a numerical model was constructed to account for the effects of complexation on diffusiophoresis. FindingsPolymer/surfactant complexation in solute gradients significantly enhanced diffusiophoretic transport of colloids. Large P123/SDS complexes formed at low SDS concentrations yielded low collective solute diffusion coefficients that prolonged the existence of strong concentration gradients relative to those without P123 to drive diffusiophoresis.

Study on the Role of Polymers in Preventing the Crystallization of Roxadustat in an Aqueous Environment

The use of polymers is an increasingly common approach to prevent crystallization from the supersaturated solutions for enhanced bioavailability of poorly water-soluble drugs. In this study, roxadustat (RST), a water-insoluble drug, was selected as a model substance. We quantified the effectiveness of three polymers with different types of hydrogen bonding moieties, polyvinylpyrrolidone (PVP), poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA), and hydroxypropyl methylcellulose (HPMC), on nuclear inhibition of RST and found that the inhibitory effect was HPMC > PVPVA > PVP. In the absence of polymers, the induction time of RST in the RST supersaturated solution was 1.5 min, while in the presence of HPMC, the induction time of RST was as long as 84.5 min. Simulation by Material Studio suggested that the compatibility and bonding energy between the polymers and RST showed a strongly positive correlation with the effectiveness of polymers. The combined inhibitory effect of hydrogen bonding and hydrophobic interaction between RST and polymers were revealed by FTIR, 1H NMR spectroscopy, and nuclear Overhauser effect spectroscopy. Moreover, the obtained amorphous-state RST in RST–polymer amorphous solid dispersions achieved improved solubility than that of crystalline RST, and the dissolved amorphous RST maintained the supersaturation for 6 h in the dissolution test without the decrease in concentration due to nucleation and crystal growth.

Investigation of Cell Adhesion and Cell Viability of the Endothelial and Fibroblast Cells on Electrospun PCL, PLGA and Coaxial Scaffolds for Production of Tissue Engineered Blood Vessel.

Endothelialization of artificial scaffolds is considered an effective strategy for increasing the efficiency of vascular transplantation. This study aimed to compare the biophysical/biocompatible properties of three different biodegradable fibrous scaffolds: Poly (ɛ-caprolactone) (PCL) alone, Poly Lactic-co-Glycolic Acid (PLGA) alone (both processed using Spraybase® electrospinning machine), and Coaxial scaffold where the fiber core and sheath was made of PCL and PLGA, respectively. Scaffold structural morphology was assessed by scanning electron microscope and tensile testing was used to investigate the scaffold tension resistance over time. Biocompatibility studies were carried out with human umbilical vein endothelial cells (HUVEC) and human vascular fibroblasts (HVF) for which cell viability (and cell proliferation over a 4-day period) and cell adhesion to the scaffolds were assessed by cytotoxicity assays and confocal microscopy, respectively. Our results showed that all biodegradable polymeric scaffolds are a reliable host to adhere and promote proliferation in HUVEC and HVF cells. In particular, PLGA membranes performed much better adhesion and enhanced cell proliferation compared to control in the absence of polymers. In addition, we demonstrate here that these biodegradable membranes present improved mechanical properties to construct potential tissue-engineered vascular graft.

The Impact of Water-Soluble Chitosan on the Inhibition of Crystal Nucleation of Alpha-Mangostin from Supersaturated Solutions.

The use of an amorphous drugs system to generate supersaturated solutions is generally developed to improve the solubility and dissolution of poorly soluble drugs. This is because the drug in the supersaturation system has a high energy state with a tendency to precipitate. In the amorphous solid dispersion (ASD) formulation, it was discovered that polymer plays a critical role in inhibiting nucleation or crystal growth of the drugs. Therefore, this study aimed to evaluate the crystallization inhibition of water-soluble chitosan (WSC) on nucleation as well as crystal growth from alpha-mangostin (AM) and elucidate its inhibition mechanism in the supersaturated solutions. During the experiment, WSC was used as a polymer to evaluate its ability to inhibit AM nucleation. The interaction between WSC and AM was also estimated using FT-IR, NMR, and in silico study. The result showed that in the absence of polymer, the concentration of AM rapidly decreased due to the precipitation in one minute. Meanwhile, the addition of WSC effectively inhibited AM crystallization and maintained a supersaturated state for the long term. FT-IR measurement also revealed that the shift in the amine primer of WSC occurred because of the interaction between WSC and AM. In the 1H NMR spectra, the proton peaks of WSC showed an upfield shift with the presence of AM, indicating the intermolecular interactions between AM and WSC. Moreover, in silico study revealed the hydrogen bond interaction between the carbonyl group of AM with hydrocarbon groups of WSC. This indicated that WSC interacted with AM in the supersaturated solution and suppressed their molecular mobility, thereby inhibiting the formation of the crystal nucleus. Based on these results, it can be concluded that the interaction between drug polymers contributed to the maintenance of the drug supersaturation by inhibiting both nucleation and growth.

Elucidation of the mechanistic aspects of chemical EOR in viscous oil systems

Chemical enhanced oil recovery techniques have been suggested as efficient alternatives to thermal methods in many thin/small viscous oil reservoirs in western Canada. These acidic oil reservoirs have been screened as good candidates for alkaline (A) and surfactant (S) floods. In this study, sand-pack core flooding experiments and pore-scale microfluidic tests were designed to give some new insights on the mechanisms of AS floods augmented with polymer (P) solutions in viscous oil systems.Viscous oil samples from Luseland field (14,850 mPa s at 25 °C) was used in all the experiments. The most efficient chemical generates ultralow interfacial tension, 0.002 mN/m, producing low viscosity type II (+) emulsion (740 mPa s, which is much lower than the viscosity of originating oil). The two pore volumes injection of this cocktail results in around 20% OOIP incremental oil recovery, which is almost doubled after injecting two pore volumes of extended water. The core effluents were all low viscosity oil in water emulsions, consistent with observations in batch mixing experiments. The incremental oil recovery to ASP flood is almost twice the recovery obtained in the polymer flood with nearly 4.5 times larger pressure build-up across the core. These observations suggest that the main mechanism is emulsification and oil entrainment rather than improvement in sweep efficiency.These speculated mechanisms based on the core scale observations were verified through the results of the microfluidic experiments. ASP solution can efficiently penetrate the residual ganglia or the edge of the water channels from which oil can be efficiently stripped. This oil is easily entrained in the form of low viscosity oil in water emulsions. Our results emphasize the critical role of polymer in the cocktail. In the absence of polymer, AS cannot efficiently penetrate the residual viscous oil leading to only a minuscule improvement in oil recovery.

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Impact of chemically reactive species on heat and mass transfer of polymeric fluid with Soret and Dufour effects

The article studies the impact of chemically reactive species on the transportation of heat and mass in a polymer-added liquid past a linearly stretching surface inserted in a porous medium taking Soret and Dufour effects into consideration. The Oldroyd-B model is opted to examine polymer insertion in the base liquid. Polymer concentration is represented by , where represents the absence of polymers. Rapid changes in boundary layer locality cause polymers to elongate, which adds an extra term in the momentum equation. Problem defining partial differential equations are converted to a set of ordinary differential equations by introducing suitable similarity variables. Drag force, mass transfer rate (MTR) and heat transfer rate (HTR) at the wall are studied and numerical solutions are attained by applying the shooting scheme with the fourth-order Runge–Kutta method. Diminution in drag force and heat transfer while expansion in mass transportation at surface is noticed and the polymer insertion is found to be the significant reason for this. The influence of chemically reactive species on MTR and HTR is also investigated when Dufour and Soret effects are also taken into consideration.

Synergistic effect of Polymer-Augmented low salinity flooding for oil recovery efficiency in Illite-Sand porous media

Low salinity water (LSW) flooding is a novel and emerging technique for oil recovery and has received significant attention recently by petroleum industries as an efficient, economical, and environmentally friendly method compared to other secondary and tertiary oil recovery methods. Although LSW flooding has been proven to be a promising technique, its conjunction with the traditional polymer flooding process (called low salinity polymer, LSP flooding) to control flood front mobility of LSW could be a game-changer. A very few studies have investigated the effectiveness of LSP flooding in terms of oil recovery efficiency. But the effect of clay minerals such as illite present in the hydrocarbon reservoir has remained to be investigated. Herein, this work reports the injection of the partially hydrolyzed polyacrylamide (HPAM) polymer augmented LSW flooding into an oil-saturated sandpack consisting of sand (98%) and illite (2%). HPAM characterization and effect of polymer concentration (1000–5000 ppm), salinity (0–60000 ppm), and temperature (26℃ − 70℃) on the rheological behaviour of the HPAM solution has been investigated. The possible mechanisms have also been discussed to understand the interaction between illite and LSP slug in the sandpack. The sandpack flooding experiments reveal that the LSP flooding recovered more additional oil (42.7%) than high salinity polymer (HSP) flooding (35.4%), with an ultimate oil recovery of 67.7% and 60.4 %, respectively. However, in the absence of polymer, oil recovery was limited to only 25% of the original oil in place (OOIP). The findings of this study can help to understand the synergistic effect of LSW and variety of polymeric solutions on oil recovery in the presence of different clay minerals.

Hybrid polymer-oxide materials formed by non-stationary electrolysis as catalysts for hydrogen peroxide decomposition

ABSTRACT Hybrid polymer-oxide materials based on transition metal oxides and polyvinylpyrrolidone have been obtained by non-stationary electrolysis on the surface of steel support. The elemental and phase compositions of the developed hybrid polymer-oxide materials have been investigated by XRF and XRD. The main phases are MoO3, MoO2, Mo18O52, Fe2O3, FeMoO4, NiMoO4, and CoMoO4. Using FT-IR spectroscopy, the incorporation of cobalt, nickel, iron, and molybdenum oxides into the structure of the polymer matrix has been proved. The surface morphology and surface height of the obtained hybrid polymer-oxide materials were reconstructed by electron microscopy and optical profilometry. Their thermal behavior was studied by comparing the DSC–TG curves of pure polyvinylpyrrolidone and the obtained hybrid polymer-oxide materials. The study of the catalytic activity in the hydrogen peroxide decomposition model reaction by the gasometric method showed that the developed hybrid polymer-oxide materials have high catalytic activity, and the presence of a polymer matrix leads to an increase in the catalytic activity of oxide phases in comparison with an oxide material of a similar composition in the absence of polymer. The study of the antibacterial activity of the obtained hybrid polymer-oxide materials showed their high efficiency against Staphylococcus aureus and Escherichia coli.

Nacre‐Inspired, Efficient, and Multifunctional Soft Magnetic Composites by Cold Sintering Design

Nacre‐mimetics hold great promise as integration of structure and function. Various techniques have been proposed to prepare nacre‐inspired materials, but in most cases, organic materials are usually used that decrease high‐temperature stability. Factually, efficient synthesis of nacre‐like high‐performance soft magnetic composites (SMCs) with good thermal stability is still challenging. Herein, a novel and simple strategy is reported on designing nacre‐like SMCs by cold sintering of ferrite‐coated alloy flakes with the absence of polymers. By selecting NH4HCO3 aqueous solution as transport solvent, a highly ordered nacre‐like structure and enhanced densification with large electrical resistivities and strong interfacial bonding are successfully achieved, which are superior to the cold‐sintered composites using water as transport solvent as well as the hot‐pressed composites based on alloy flakes and epoxy resin. The resultant composites illustrate large density (≈6.286 g cm−3) and electrical resistivity (≈3.9 × 105 Ω cm), allowing remarkable flexural strength (≈46.5 MPa), high permeability (μ′ = ≈107.3 at f = 10 MHz), together with low tanδ μ (≈0.09 at f = 10 MHz) and P cv (≈183.6 kW m−3 at 50 mT/100 kHz), which show great potential in high‐frequency power electronic and electrical systems. The synthesis strategy sheds light on designing other nacre‐like materials or developing new metal−ceramic composites.

Effects of polyvinylpyrrolidone and poly (ethylene glycol) on preparation of ibuprofen pharmaceutical cocrystal

In this study, we investigated the effects of polymers on the pharmaceutical cocrystal formation process. Ibuprofen (IBU) was selected as the active pharmaceutical ingredient (API), nicotinamide (NIC) and saccharin (SAC) as the cocrystal coformer (CCF), ethanol/water as the solvent, polyvinylpyrrolidone (PVP) and poly (ethylene glycol) (PEG) as the representative polymers. We prepared IBU-NIC and IBU-SAC cocrystals in ethanol-water cosolvent in the absence or presence of polymers. Cocrystal screening products were characterized by FTIR, DSC, PXRD, and HPLC. The results showed that the mixture of IBU and IBU-NIC cocrystal can be prepared in ethanol-water cosolvent without polymers. The addition of PVP facilitates the formation of pure IBU-NIC cocrystal; however, no cocrystal was formed in PEG solutions. SAC could not cocrystallize with IBU in the ethanol-water solvent in the absence of polymers. Neither PVP nor PEG could facilitate the formation of the IBU-SAC cocrystal.

Hydrogel composed of potassium acrylate, acrylamide, and mineral as soil conditioner under saline conditions

Hydrogels have potential as soil conditioners due to their high capacity to retain water and mitigate soil salinity. However, investigations under saline conditions are necessary because there are losses in both water absorption and salinity mitigation depending on the composition of hydrogel and ions involved in salinity. In this work, we studied a commercial hydrogel in two experiments. The first experiment was conducted in the laboratory to evaluate the absorption by the hydrogel of water with electrical conductivity (EC) of 0.5, 1.5, 3.0, and 4.5 dS m–1, promoted by NaCl. The second experiment was conducted in a greenhouse in a 2 × 4 factorial scheme (with and without hydrogel × EC of the first experiment). Although salinity reduced water absorption by hydrogel by 84 %, the polymer applied in a sandy soil under saline conditions reduced water losses by 58 %. However, hydrogel did not increase the final soil moisture (~ 0.10 g g–1). The polymer reduced Na+ concentration in leachate from 1,499 to 1,219 mg L–1 at the highest salinity level (4.5 dS m–1), but it increased Na+ soil availability by 0.1 mg kg–1 in comparison with polymer absence. Hydrogel application increased Na+ content in plants from 9 to 13 mg kg–1 at the highest salinity, while K+ content was 10 to 16 mg kg–1 lower than that observed without a polymer. Hydrogel 0.07 % (w/w) reduced maize biomass, indicating damage by monovalent ions, compromising the polymer potential under salinity.

Polymeric precipitation inhibitor differently affects cocrystal surface and bulk solution phase transformations

During the dissolution of cocrystal particles, solution-mediated phase transformation (SMPT) can occur either on the particle surface (PS-SMPT) or in the bulk phase solution (BP-SMPT). In this study, we compared the effect of various polymers on PS-SMPT and BP-SMPT for the first time using carbamazepine saccharine cocrystal (CBZ-SAC) as a model drug. Polyethylene glycol 6000 (PEG), polyvinylpyrrolidone K-30 (PVP), hydroxypropyl methylcellulose (HPMC), hydroxypropyl methylcellulose acetate succinate (HPMC-AS), amino methacrylate copolymer (EPO), and methacrylic acid copolymers (L100-55) were used as polymeric precipitation inhibitors. In the non-sink dissolution test, CBZ-SAC rapidly transforms to CBZ dihydrate (CBZ DH) via PS-SMPT in the absence of polymers. The polymers enhanced the dissolution rate and subsequent supersaturated CBZ concentration in the order of HPMC-AS > HPMC > EPO ≫ PVP ≈ L100-55 ≈ PEG. On the other hand, in the solvent-shift precipitation test, these polymers inhibited the precipitation of CBZ DH in a different order (EPO > HPMC > HPMC-AS ≫ L100-55 ≈ PVP ≫ PEG). The polymers affected the crystal habit of CBZ DH differently between PS-SMPT and BP-SMPT. Direct PS-SMPT observation by real-time polarized light microscopy (RT-PLM) showed that PS-SMPT was significantly inhibited by HPMC-AS, HPMC, and EPO, but less by PVP, L100-55, and PEG. Differences in solid surface pH and heterogeneous nucleation were discussed as the reason for the difference in the inhibitory effect between polymers in PS-SMPT and BP-SMPT. In conclusion, the inhibitory effect of polymers can differ between PS-SMPT and BP-SMPT. For the successful development of a cocrystal formulation, it is important to select a potent inhibitor of PS-SMPT.

A comparative study between the effect of swirl flow and axial flow on the rate of diffusion controlled corrosion in a double tube heat exchanger

ABSTRACT The rate of diffusion-controlled corrosion of an annulus under swirl flow was studied by measuring the limiting current of the cathodic reduction of potassium ferricyanide depolarizer in the presence and absence of polyox WSR-301 drag-reducing polymer. It was found that the rate of diffusion-controlled corrosion of the inner cylinder of the annulus increases with increasing swirl flow solution velocity and decreases with increasing the active height of the cylinder. The data in the absence of polymer (blank solution) under swirl flow were fitted by a dimensionless equation. The importance of this equation in predicting the rate of diffusion-controlled corrosion and the corrosion allowance during the design of the swirl flow equipment was highlighted. For a given set of conditions, the rate of accelerated swirl flow corrosion was much higher than that of axial flow. Drag reducing polymer was found to inhibit the rate of diffusion-controlled corrosion by a maximum of 23%, if other benefits of the polymer are considered such as the decrease in the shear stress and the associated decrease in the erosion-corrosion tendency besides the decrease in pressure drop and pumping power requirement it may be concluded that the use of drag-reducing polymers in industry is worthwhile.

Celecoxib Crystallized from Hydrophilic Polymeric Solutions Showed Modified Crystalline Behavior with an Improved Dissolution Profile

The crystallization technique has been established as a cost-effective and simple approach to improve the dissolution rate and oral bioavailability of poorly soluble drugs. This study was carried out to study the effect of some selected hydrophilic polymers such as methyl cellulose, hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol, and carboxymethyl cellulose on the crystal behavior and dissolution properties of celecoxib (CLX), a common nonsteroidal anti-inflammatory drug. Structural and spectral characteristics of crystallized CLX have been studied by Fourier transform infrared (FTIR) spectroscopy, diffraction scanning calorimetry (DSC), and X-ray diffraction (XRD) analysis. From FTIR and DSC analysis, no significant shifting of peaks or appearance of any new peaks (for polymers) were observed, which indicated the absence of any major interaction between drug and polymers as well as the absence of polymers in the final crystallized product of CLX. The XRD analysis showed a change in crystalline morphology to some extent. The dissolution rate of crystallized CLX in the presence of polymers (particularly with HPMC) was significantly improved compared with plain CLX. The improved dissolution profile of the experimental CLX crystal products could be an indication of improved bioavailability of CLX for better clinical outcome.