Polymer Swelling Research Articles

Effect of polymer swell in extrusion foaming of low-density polyethylene

Insights into the effect of die swell on extrusion foam of thermoplastic polymers are presented. The die swell or Barus effect is the swelling of a viscoelastic material due to a fast elastic recovery after being subjected to stress. The elastic recovery is proportional to the energy stored in the material during the deformation that is released immediately when the material is free to expand. In extrusion foam, the elastic recovery happens at the die exit together with the foaming process (i.e., bubble nucleation and growth). Previous reports on extrusion have focused on modeling the die swell or foaming individually. We investigated the existence of a link between the die swell and foaming that is fundamental in designing the geometry of a die for extrusion foam. Simple and complex dies were used to measure the expansion ratio of a polyethylene blown with isobutane and CO2. It was found that the expansion ratio is anisotropic, the anisotropy in the expansion of the foam is due to the die swell strongly affecting the final shape of the product, and it cannot be neglected in standard application for extrusion foam. Surprisingly, it was found that the foam density changes at a high level of die swell because it is affected by the elastic recovery of the material.

Toward predictive permeabilities: Experimental measurements and multiscale simulation of methanol transport in Nafion

AbstractA polymer membrane's permeability to solutes determines its suitability for various applications: a permeability value is essential for predicting performance in diverse contexts. Using aqueous methanol permeation through Nafion as an example, we describe a methodology for determining membrane permeability that accounts for boundary layer effects and the possibility of swelling. For the materials and apparatus used herein, analysis of a permeance measurement and computational fluid dynamics simulations show that the mass transfer boundary layer is on the order of ones to tens of microns. The data are used to develop and validate a multiscale model describing solute permeation through a hydrated membrane as a series of physical mechanistic steps: reversible adsorption from solution at the membrane interface, diffusion driven by a concentration gradient within the membrane, and reversible desorption into solution at the opposite membrane interface. The validated model is used to predict methanol transport across a solar‐driven CO2 reduction device and to assess the impact of polymer changes on the measured value. The approach of combining experimental data, computational fluid dynamics, and the mechanistic multiscale model is expected to provide more accurate analysis of membrane permeation data in cases with polymer swelling or unusual device geometries, among others.

Mechanistic explanation of the (up to) 3 release phases of PLGA microparticles: Monolithic dispersions studied at lower temperatures

The aim of this study was to better understand the underlying drug release mechanisms in poly(lactic-co-glycolic acid) (PLGA) microparticles in which the drug is dispersed in the form of tiny particles (“monolithic dispersions”). Differently sized diprophylline-loaded microparticles were prepared using a solid-in-oil-in-water solvent extraction/evaporation technique. The microparticles were characterized before and after exposure to phosphate buffer pH 7.4 at 4, 20 and 37 °C. In vitro drug release was measured from ensembles and single microparticles. GPC, DSC, SEM, gravimetric analysis, drug solubility measurements and optical microscopy were used to elucidate the importance of polymer swelling & degradation, drug dissolution and diffusion. The diprophylline was initially homogeneously distributed throughout the microparticles in the form of tiny crystals. The burst release (1st phase) was strongly temperature-dependent and likely attributable to the dissolution of drug crystals with direct surface access (potentially via tiny pores). The about constant release rate during the 2nd phase also strongly depended on the temperature. It can probably be explained by the dissolution of drug crystals in surface near regions undergoing local swelling. During the observation period, the 3rd (again rapid) drug release phase was only observed at 37 °C, and seems to be caused by substantial PLGA swelling throughout the entire microparticles. This phase starts as soon as a critical polymer molecular weight of about 25 kDa is reached: Significant amounts of water penetrate into the systems, dissolving the remaining diprophylline crystals and substantially increasing the mobility of the dissolved drug molecules. Thus, this study provides additional experimental evidence (obtained at lower temperatures) confirming the hypothesized root causes for drug release from PLGA microparticles containing dispersed drug particles.

DRUG RELEASE CONTROL AND ENHANCEMENT USING CARRIERS WITH DIFFERENT CONCENTRATIONS OF CAPMUL® MCM C8

Objective: The main aim of this study was to design a drug carrier capable to control and enhance the release of poorly water soluble drugs.
 Methods: Three polymeric formulations, based on poly (2-hydroxyethyl methacrylate) and loaded with different Capmul® MCM C8 concentrations (0, 10 and 20 % w/w), were prepared. Felodipine, which is a poorly soluble substance, was selected as a model drug. The effect of Capmul® MCM C8 on swelling behavior and in vitro release profile of the prepared polymer was investigated in PBS.
 Results: The swelling profiles of allformulationswere statistically similar, which indicated the non-significant effect of added Capmul® MCM C8 on polymer's swelling behavior. All formulations showed a delayed drug release. Formulation-F3, which is loaded with 20% w/wCapmul® MCM C8 displayed a significant higher release compared to the other formulations.
 Conclusion: Capmul® MCM products, which are widely used in food industries, can be used to improve the oral delivery of poorly soluble substances. The optimized formulation exhibited the ability to control and enhance the release of the model drug.

Migration from acrylonitrile butadiene styrene (ABS) polymer: swelling effect of food simulants compared to real foods

Materials and articles made of acrylonitrile–butadiene–styrene (ABS) intended for contact with food must comply with the requirements of the European Plastic Regulation (EU) 10/2011, which lays down the food simulants and the time/temperature conditions to be applied for migration testing. Previous studies indicated that high concentrations of ethanol at temperatures above ambient may lead to swelling of ABS polymers resulting in increased migration. In this study migration kinetic data for a set of model substances at different temperatures were obtained using both food simulants stipulated in EU regulations and real food (milk, cream and olive oil). At the same time, the extent of polymer swelling was gravimetrically characterized after contact with simulants and different foods tested at several conditions to cover the majority of foreseeable applications of ABS. The obtained results confirmed that the use of high concentrations of ethanol–water, especially at high temperatures, causes the swelling of ABS polymers and results in significantly higher migration values compared to the tested foods as well as Tenax®. None of the real foods studied cause significant swelling of ABS. The widely used simulant 95% (v/v) aqueous ethanol proves not be suitable for compliance testing of ABS under the recommended conditions of Regulation (EU) 10/2011. Swelling of the polymer results in artificially higher diffusion coefficients or lower activation energies of diffusion. Migration prediction using polymer-specific diffusion parameters should therefore be considered to avoid over-conservative risk assessment for food contact materials and articles made of ABS.

Simulation and optimization of working parameters of the rapid-dissolution device of hydrophobically associating polymer

To solve the dissolution problem of hydrophobically associating polymers during the application process, a rapid-dissolution device was developed and optimized. The relevant parameters of the device were simulated with a focus on the fluid-passing capacity, rotating speed, and device structure to study the dissolution effect using the Fluent software. The results indicated that under the condition that the fluid-passing capacity of a single rapid-dissolution device was 12 m3/h, the viscosity of the hydrophobically associating polymer solution allowed to pass through the device should not exceed 21 mPa s. When the rotating speed of the rotor was 1440 rpm, the polymer had uniform distribution when passing through the device and could achieve a good tensile dissolution effect. By installing a fan blade in the device, the retention problem of polymer swelling particles in the dissolution device was solved, and the dispersion and dissolution of the polymer are promoted. The rapid-dissolution device was suitable for the dissolution of hydrophobically associating polymers in the oil field and so as to promote the application of hydrophobically associating polymers.

Quantification of the ion transport mechanism in protective polymer coatings on lithium metal anodes.

Protective Polymer Coatings (PPCs) have been proposed to protect lithium metal anodes in rechargeable batteries to stabilize the Li/electrolyte interface and to extend the cycle life by reducing parasitic reactions and improving the lithium deposition morphology. However, the ion transport mechanism in PPCs remains unclear. Specifically, the degree of polymer swelling in the electrolyte and the influence of polymer/solvent/ion interactions are never quantified. Here we use poly(acrylonitrile-co-butadiene) (PAN–PBD) with controlled cross-link densities to quantify how the swelling ratio of the PPC affects conductivity, Li+ ion selectivity, activation energy, and rheological properties. The large difference in polarities between PAN (polar) and PBD (non-polar) segments allows the comparison of PPC properties when swollen in carbonate (high polarity) and ether (low polarity) electrolytes, which are the two most common classes of electrolytes. We find that a low swelling ratio of the PPC increases the transference number of Li+ ions while decreasing the conductivity. The activation energy only increases when the PPC is swollen in the carbonate electrolyte because of the strong ion–dipole interaction in the PAN phase, which is absent in the non-polar PBD phase. Theoretical models using Hansen solubility parameters and a percolation model have been shown to be effective in predicting the swelling behavior of PPCs in organic solvents and to estimate the conductivity. The trade-off between conductivity and the transference number is the primary challenge for PPCs. Our study provides general guidelines for PPC design, which favors the use of non-polar polymers with low polarity organic electrolytes.

Identifying the Thermal Storage Stability of Polymer‐Modified Asphalt with Carbon Nanotubes Based on Its Macroperformance and Micromorphology

The thermal storage stability of polymer‐modified asphalt (PMA) is the key to avoid performance attenuation during storage and transportation in pavement engineering. However, phase separation of PMA continuously occurs after long‐term thermal storage due to the overlooked influence of the phase interface. Two kinds of carbon nanotubes (CNTs) and styrene‐butadiene‐styrene triblock copolymer (SBS) were selected in this paper to address the aforementioned issue. The segregation test was used to simulate the long‐term storage process from 0 to 10 days. Macroperformance included the softening point difference (△SP), irrecoverable compliance (Jnr), recovery rate (R%), and complex modulus (G∗) measured by the softening point test, multistress creep recovery (MSCR) test, and small strain oscillatory rheological test. Microcharacteristics were obtained by the SBS characteristic peak index, SBS‐rich phase distribution, polymer swelling degree, and particle characteristics of the SBS‐rich phase. They were measured by Fourier‐transformed infrared spectroscopy (FT‐IR), fluorescence microscopy (FM), and atomic force microscopy (AFM), respectively. Results showed that the optimum CNT amount necessary to obtain an improved thermal storage stability of PMA was 0.5 wt.%. After 10 days of storage, the largest R% of SBS modified asphalt (SBSMA) decreased to 2.24% and the smallest Jnr increased to 0.069 1/kPa, while R% of SBSMA with CNTs was 62.15% and its Jnr was 0.013 1/kPa. R% and Jnr of SBSMA with CNTs showed almost no change after 6 days of storage, implying an effective antirutting performance. The results from the microperformance investigation showed that phase separation of SBS mainly occurred on day 4, while SBS degradation and base asphalt aging led to the worse macroperformance after 10 days of storage. Additional CNTs restrained the SBS‐rich phase from floating upward. Meanwhile, a small size of polymer‐rich phase and dense network of SBSMA with CNTs were observed in fluorescence microscopy and atomic force microscopy images, thereby exhibiting improved thermal storage stability. Adding CNTs would retard the segregation due to CNT entanglement with SBS.

In-situ investigation of wetting patterns in polymeric multibore membranes via magnetic resonance imaging

Wetting of the membrane to displace air or conditioning liquids is important to exploit the complex porosity of a filtration membrane. This study reveals the details of wetting in multibore membrane-based filtration modules. Using magnetic resonance imaging (MRI), we quantify the fluid distribution patterns during initial membrane wetting in dead-end permeation mode. The spatio-temporal evolution of aqueous copper sulfate solution wetting the membrane fibers was investigated as a function of the applied flux, packing density, and position along the membrane module length.Three initial wetting conditions were examined: delivery-state membranes, ethanol-washed and dried (air-filled) membranes, and ethanol-filled membranes. Significant changes in wetting patterns were observed due to interfacial and polymer swelling effects. This in-situ investigation reveals a slow wetting progression over six hours and more to obtain complete wetting, even at high fluxes of 200 LMH. However, an increased flux leads to faster wetting kinetics as the evolving wetting patterns are flux dependent. The packing density of the multibore fibers additionally impacts the wetting kinetics by shifting the prevalent pressure conditions. Although in dead-end mode, the wetting progression is non-uniform along the membrane module length.In addition to this parameter study, different pre-wetting agents’ effect on the displacement behavior was investigated in depth. This study helps to understand (a) complex wetting phenomena inside multibore membranes in dead-end filtration, (b) the membranes’ interaction with their surroundings due to neighboring membranes, and (c) the effect of the used fluid system for displacement on the resulting wetting patterns.

Demonstration of a Label-Free and Low-Cost Optical Cavity-Based Biosensor Using Streptavidin and C-Reactive Protein.

An optical cavity-based biosensor (OCB) has been developed for point-of-care (POC) applications. This label-free biosensor employs low-cost components and simple fabrication processes to lower the overall cost while achieving high sensitivity using a differential detection method. To experimentally demonstrate its limit of detection (LOD), we conducted biosensing experiments with streptavidin and C-reactive protein (CRP). The optical cavity structure was optimized further for better sensitivity and easier fluid control. We utilized the polymer swelling property to fine-tune the optical cavity width, which significantly improved the success rate to produce measurable samples. Four different concentrations of streptavidin were tested in triplicate, and the LOD of the OCB was determined to be 1.35 nM. The OCB also successfully detected three different concentrations of human CRP using biotinylated CRP antibody. The LOD for CRP detection was 377 pM. All measurements were done using a small sample volume of 15 µL within 30 min. By reducing the sensing area, improving the functionalization and passivation processes, and increasing the sample volume, the LOD of the OCB are estimated to be reduced further to the femto-molar range. Overall, the demonstrated capability of the OCB in the present work shows great potential to be used as a promising POC biosensor.

Numerical simulation of pillars and electromagnetic mode coupling for nanoparticle sensors

Sensors based on the response of the photonic crystal in imprint polymers (hydrogels) have recently attracted considerable attention for visual medical diagnostics, pharmaceutical bioassays, environmental monitoring, and nanoparticle detection. These applications often use the variation of the wavelength as a function of the diameter of the air sphere (inverse opal hydrogels) according to the Bragg equation at a fixed incident angle. However, these promising materials mixed with fluorescent nanocrystals for the detection of targeted nanoparticles have never been explored so far with the finite differential time-domain (FDTD) method, electric field intensity map, and radiated power profile at far-field. In this paper, we have combined silicon nanopillars, nanoparticles, imprint polymers, and nanocrystal fluorescence. The sensitivity of the sensor we simulate depends on the nanocrystal fluorescence variation when the imprint polymer swells (polymer thickness variation). We have shown numerically that the electric field intensity at far-field is at a maximum in the pillar’s symmetrical axis when the dipole (representing the nanocrystal) polarization is perpendicular to the pillar. Also, we have shown that radiated power is increasing and monotone when the thickness of the imprint polymer evolves between 498 and 912 nm. The purpose of this numerical simulation is to develop a nanoparticle sensor with high sensitivity, high selectivity, and an efficient detection device.

Semi-Interpenetrating Polymer Networks Based on N-isopropylacrylamide and 2-acrylamido-2-methylpropane Sulfonic Acid for Intramolecular Force-Compensated Sensors

Stimulus-responsive hydrogels are swellable polymers that take up a specific volume depending on a measured variable present in solution. Hydrogel-based chemical sensors make use of this ability by converting the resulting swelling pressure, which depends on the measured variable, into an electrical value. Due to the tedious swelling processes, the measuring method of intramolecular force compensation is used to suppress these swelling processes and, thus, significantly increase the sensor’s response time. However, intramolecular force compensation requires a bisensitive hydrogel. In addition to the sensitivity of the measured variable the gel has to provide a second sensitivity for intrinsic compensation of the swelling pressure. At the same time, this hydrogel has to meet further requirements, e.g. high compressive strength. Until now, interpenetrating polymer networks (IPN) have been used for such a force-compensatory effective hydrogel, which are complex to manufacture. In order to significantly simplify the sensor design and production, a simpler synthesis of the bisensitive hydrogel is desirable. This paper presents a new bisensitive hydrogel based on semi-interpenetrating polymer networks. It is based on a copolymer network consisting of N-isopropylacrylamide (NiPAAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and long PAMPS strands that permeate it. Measurements show, that this hydrogel meets all essential requirements for intramolecular force compensation and is at the same time much easier to synthesize than previously used IPN hydrogels.

Swelling of biodegradable polymers for the production of nanocapsules and films with the incorporation of essential oils

Many researchers work with essential oils for several applications, such as their impregnation in polymeric films and for obtaining micro-/nanocapsules by using polymers as shell material. Polymer swelling/liquid dissolution is an extremely important property for controlled release of essential oils. Therefore, this work proposes a comparative study of swelling/dissolution interaction of polymer films immersed in different essential oils. Six polymers were used for this study: polycaprolactone (PCL) and poly(lactic acid) (PLA), gum arabic, sodium alginate, gelatin, and carboxymethyl cellulose. Polymer films were obtained by applying the casting method. In addition, PCL and PLA were molded by compression. Six different essential oils were used: Mentha piperita, Cymbopogon nardus, Mentha arvensis, Syzygium aromaticum, Lavandula hybrida, and Eucalyptus globulus. Each film was kept at room temperature immersed in sufficient quantity to cover the polymer film at intervals of 1, 3, 5, 7, 14, 28, 56, and 112 days. The same procedure was repeated at 4 °C and 35 °C at intervals of 1, 3, 5, and 7 days. PCL and PLA films were completely dissolved in Syzygium aromaticum essential oils for 24 h at the three temperatures tested. For all other polymers, weight gain occurred during the first 7 days and remained constant during the following days. The highest weight gains were 15.519% and 10.463% for polycaprolactone with Mentha piperita and gum arabic with Eucalyptus globulus, respectively.

A cosolvent surfactant mechanism affects polymer collapse in miscible good solvents

The coil–globule transition of aqueous polymers is of profound significance in understanding the structure and function of responsive soft matter. In particular, the remarkable effect of amphiphilic cosolvents (e.g., alcohols) that leads to both swelling and collapse of stimuli-responsive polymers has been hotly debated in the literature, often with contradictory mechanisms proposed. Using molecular dynamics simulations, we herein demonstrate that alcohols reduce the free energy cost of creating a repulsive polymer–solvent interface via a surfactant-like mechanism which surprisingly drives polymer collapse at low alcohol concentrations. This hitherto neglected role of interfacial solvation thermodynamics is common to all coil–globule transitions, and rationalizes the experimentally observed effects of higher alcohols and polymer molecular weight on the coil-to-globule transition of thermoresponsive polymers. Polymer–(co)solvent attractive interactions reinforce or compensate this mechanism and it is this interplay which drives polymer swelling or collapse.

Formulation and evaluation of gastro-retentive floating bilayer tablet for the treatment of hypertension

The paper aimed to progress an ideal gastro retentive drug delivery system intended for directing Losartan and Hydrochlorothiazide as a fixed-dose combination for anti-hypertensive therapy. The bilayer tablets were primed through direct compression method. Losartan was formulated by means of a floating layer expending hydrophilic swellable polymer Hydroxy Propyl Methyl Cellulose K4M, ethyl cellulose (4cps) as a buoyancy enhancer, sodium bicarbonate as a gas spawning agent. The amount of polymer blends remains optimized using 23 full factorial designs. The clout of experimental factors such as swelling agent concentration, buoyancy enhancer and gas generating agent on floating lag time, total floating time, T50% and % drug release remain investigated to get optimized formulation. The responses remain analyzed using Analysis of variance, and polynomial equation stood created for every retort using Multiple linear regression analysis. Entirely preparations floated for more than 12 h. The release pattern of losartan stood fitted to diverse models based on the coefficient of correlation (r). All the formulations, except F2, showed the Korsemeyer-Peppas model as the best fit model. Formulation F2 showed the zero-order model. Diffusion exponents (n) remained indomitable designed for entirely formulations (0.45–0.89), accordingly the chief drug discharge mechanism was non-fickian (anamolous) transport. Formulation F4 containing 20% w/w Hydroxy Propyl Methyl Cellulose K4M, 15% Sodium bicarbonate and 5% ethyl cellulose (4cps) was the best formulation as per the range of drug release remain institute to be more than 95 % in 12h and floating lag time was 20.15 s. The immediate-release layer stood optimized using crospovidone and Indion 414 as a super disintegrant. Formulation A8 containing 2% Indion 414 was considered as optimized formulation as it released 99% drug within 35 min and possessed less disintegration time. Optimized formulation F4 from the controlled-release layer and A8 from immediate-release layer was used to formulate bilayer tablet. The optimized formulation was imperilled to stability reading for three months at 40○C/75% relative humidity. The stability revision exhibited no substantial alteration in the appearance of tablets, floating characteristics, drug content and in-vitro drug dissolution. Consequently, a biphasic drug release design was effectively accomplished over the formulation of floating bilayer tablets.

Hydration Water Structure, Hydration Forces, and Mechanical Properties of Polysaccharide Films.

The interaction of polysaccharides with water has a critical impact on their biological function as well as their technological applications. We performed ellipsometry experiments at different relative humidities (RH) to measure the equilibrium swelling of ultrathin films of different polysaccharides: native and modified phytoglycogen (PG) nanoparticles, dextran, and hyaluronic acid. For RH > 70%, the swelling of hydrophilic polymers with increases in RH is described by hydration forces that are characterized by an exponential decay length λ. Our analysis of the high RH swelling regime allowed us to determine λ and the bulk modulus K of the films of different polysaccharides. We also probed the high RH swelling regime using attenuated total reflection infrared (ATR-IR) spectroscopy, which allowed us to determine the degree of hydrogen bonding of the hydration water within the polysaccharide films. Combining the ellipsometry and ATR-IR spectroscopy results, we find that increases in the order of the hydrogen bond network of the hydration water, as specified by the ATR-IR parameter Rnetwork, lead to linear increases in K and corresponding inverse changes in λ. These measurements help to elucidate the intimate relationships between the degree of ordering of hydration water, hydration forces, and the mechanical stiffness of polysaccharides. For phytoglycogen, the addition of chemical groups, both cationic and anionic, produced significant increases in its water holding capacity and mechanical properties, suggesting that chemical modification can be used to tune the properties of phytoglycogen for different applications.

High resolution photopolymer for 3D printing of personalised microneedle for transdermal delivery of anti-wrinkle small peptide

Acetyl-hexapeptide 3 (AHP-3) has good efficacy and safety profile as an anti-wrinkle small peptide. However, its skin permeation is poor due to its hydrophilicity and large molecular weight. 3D printing of personalised microneedles (MN), that contour to the skin surface, offers an attractive alternative for delivery for AHP-3. However, commercially available photocurable resin for 3D printing are not suitable for fabrication of drug loaded delivery systems. In this study, two liquid monomers, namely, polyethylene glycol diacrylate (PEGDA) and vinyl pyrrolidone (VP), were investigated at various proportions, for critical parameters such as mechanical strength of final polymer, rate of polymerisation, rate of swelling of final polymer, 3D printing resolution and safety profile of final polymer. The optimal resin, based on the above parameters, was that of ratio 7 VP: 3 PEGDA in weight. Drug loading into the optimal resin demonstrated that AHP-3 remained stable throughout the fabrication process and there was no effect on the physical properties of final polymer. Using a 3D scanned face model, a personalised MN patch was designed using computer aided design (CAD) software and subsequently fabricated using a Digital Light Processing (DLP) 3D printer, with the optimal resin. In vitro characterisation of fabricated MN patch demonstrated the ability to penetrate human cadaver dermatomed skin and the MN remained intact after compression. The final polymer also had minimal cytotoxicity to human dermal fibroblast. Therefore, personalised MN patch fabricated using the photopolymer can potentially be a novel approach to augment transdermal delivery of AHP-3 for effective wrinkle management.

The Formulation and Evaluation of Gastro-Bilayer Floating Tablets of Losartan Potassium as Immediate Release Layer and Ramipril Hydrochloride as Sustained Release Floating Layer

Objectives: A sustained release Gastro-bilayer floating tablets with reduced dosing frequency and increased drug bioavailability is developed. The dosage form is suitable for the release of two drugs simultaneously in a single dosage unit i.e. Losartan Potassium and Ramipril Hydrochloride. The SeDeM system for selection of powder blend for direct compression gave the parameter index value of ≥0.5 which is considered as best in terms of compression properties. The prepared dosage form provided sustained effect of the drug for 12 hr by Non-Fickian, controlled diffusion and swollen matrix. Peppa’s release model is best suited for the final formulation of batches. Optimized formulation exhibited floating time of 12 hr and floating lag time of less than 1 min. In-vitro dissolution studies shows 96% of the both the drugs release. The swelling and erosion of polymers is studied by Scanning Electron Microscopy. The data obtained from Analysis of variance demonstrated the significance of the model with a P-value of less than 0.05. Methods: SeDeM system was adopted on powder blend before direct compression for preparation of tablet, the hydroxyl propyl methyl cellulose was used as a rate-controlling polymer and a mixture of citric acid and Sodium bicarbonate formed the floating layer. Results: Radius values through SeDeM diagram was plotted and index values are calculated and resulted in an index value of ≥0.5. The pre-compression and post compressional parameters are as per Indian Pharmacopeia specifications. The best formulation for gastric bilayer tablet had a combination of Hydroxy propyl methyl cellulose K15M and Sodium Carboxy methyl cellulose which gave 99.57% drug dissolution within 12 hr. Conclusion: Gastro-Bilayer Floating Tablets of Losartan as Immediate Release layer and Ramipril as sustained-release floating layer are successfully developed. The problem of poor solubility of drugs can be solved by optimization of blend through SeDeM expert System. Hydroxy propyl methyl cellulose K15M, K4M and Carbopol 934 are helpful in achieving the sustained effect of the drug for 12 hr by Non-Fickian, controlled diffusion and swollen matrix. Peppa’s release model is best suited for the final formulation batches based on the drug release mechanisms.

Tuning the Structure and Performance of Bulk and Porous Vapor Sensors Based on Co-continuous Carbon Nanotube-Filled Blends of Poly(vinylidene fluoride) and Polycarbonates by Varying Melt Viscosity.

This work describes a new concept of porous vapor sensor materials based on co-continuous polycarbonate/poly(vinylidene fluoride)/multiwalled carbon nanotube (PC/PVDF/MWCNT) blend composites. The blend composites were fabricated by melt mixing in a one-step mixing process, and the MWCNT containing component (here PC) was extracted, leaving a MWCNT network on the continuous surface of the remaining component (here PVDF). First, by selecting three PCs with different molecular weights, the blend viscosity ratio and blend fineness and interfacial area were varied. At the chosen blend composition of 40/60 wt %, the desired co-continuous structure was achieved with MWCNTs selectively localized in PC. The conductive polymer composites (CPCs) with low-viscosity PC had the highest conductivity due to a combination of the best MWCNT dispersion and the coarsest blend morphology. The vapor sensing of CPC sensor materials with 1 wt % MWCNT was tested using saturated vapors of dichloromethane, acetone, tetrahydrofuran, and ethyl acetate, showing good interaction with PC. The compact compression molded CPC materials with low-viscosity PC showed the lowest relative resistance changes (Rrel) during the cyclic sensing tests, but a better recovery compared to corresponding CPCs with medium and high viscosity PC. The porous CPC sensors showed remarkable vapor sensing performance compared to the corresponding compact sensors with better sensing stability, reproducibility, and reversibility. Scanning electron microscopy (SEM) confirmed that a fraction of the nanotubes remained on the surface of the continuous, nonsoluble PVDF after PC extraction. The porous sensor material from which the low-viscosity PC was extracted showed the highest Rrel (e.g., around 1300% after 100 s immersion in acetone vapor) compared to all other organic vapors investigated. The difference in vapor measurement between compact and porous sensor materials was attributed to the different sensing mechanisms of polymer swelling for the compact and vapor absorption on the free CNT networks for the porous samples.

Approaches to Understanding the Solution-State Organization of Spray-Dried Dispersion Feed Solutions and Its Translation to the Solid State

It is well established that polymers adopt a range of conformations and solution-state organization in response to varying solution environments, although very little work has been done to understand how these effects might impact the physical stability and bioavailability of spray-dried amorphous dispersions (SDDs). Potentially relevant solution-state polymer-solvent/cosolute interactions include preferential solvation, hydrodynamic size (i.e., polymer swelling or collapse), and solvent quality effects (i.e., attractive or repulsive self-interactions). Of particular interest is the investigation of preferential solvation, defined as the relative attraction or rejection of a cosolvent and/or cosolute from the local environment of a solvated macromolecule, which often occurs in multicomponent macromolecular solutions. As spray drying and other solvent-based dispersion processing necessitates the use of complex media consisting of at least three or more components (drug, polymer, solvent(s), and other possible excipients), the prevalence of this phenomenon is likely. This work characterizes largely unexplored solution-state properties in model spray-dried dispersion feed solutions using light scattering and viscometric techniques to add greater context and guidance in studying these information-rich materials. These systems are found to exhibit complex non-intuitive behavior, which serves to highlight the potential utility of preferential solvation in spray-dried dispersion processing and stability. It is hypothesized that solution-state organization of the liquid feed can be engineered and translated to the solid-state for the optimization of SDD properties.