Total Polymer Concentration Research Articles

Soluble tubulin is significantly enriched at mitotic centrosomes.

During mitosis, the centrosome expands its capacity to nucleate microtubules. Understanding the mechanisms of centrosomal microtubule nucleation is, however, constrained by a lack of knowledge of the amount of soluble and polymeric tubulin at mitotic centrosomes. Here we combined light microscopy and serial-section electron tomography to measure the amount of dimeric and polymeric tubulin at mitotic centrosomes in early C. elegans embryos. We show that a C. elegans one-cell stage centrosome at metaphase contains >10,000 microtubules with a total polymer concentration of 230 µM. Centrosomes concentrate soluble α/β tubulin by about 10-fold over the cytoplasm, reaching peak values of 470 µM, giving a combined total monomer and polymer tubulin concentration at centrosomes of up to 660 µM. These findings support in vitro data suggesting that microtubule nucleation in C. elegans centrosomes is driven in part by concentrating soluble tubulin.

Valve leaflet‐inspired elastomeric scaffolds with tunable and anisotropic mechanical properties

Fibrous scaffolds, which can mimic the elastic and anisotropic mechanical properties of native tissues, hold great promise in recapitulating the native tissue microenvironment. We previously fabricated electrospun fibrous scaffolds made of hybrid synthetic elastomers (poly(1,3‐diamino‐2‐hydroxypropane‐co‐glycerol sebacate)‐co‐poly (ethylene glycol) (APS‐co‐PEG) and polycaprolactone (PCL)) to obtain uniaxial mechanical properties similar to those of human aortic valve leaflets. However, conventional electrospinning process often yields scaffolds with random alignment, which fails to recreate the anisotropic nature of most of the soft tissues such as native heart valves. Inspired by the structure of native valve leaflet, we designed a novel valve leaflet‐inspired ring‐shaped collector to modulate the electrospun fiber alignment and studied the effect of polymer formulation (PEG amount [mole %] in APS‐co‐PEG; ratio between APS‐co‐PEG and PCL; and total polymer concentration) in tuning the biaxial mechanical properties of the fibrous scaffolds. The fibrous scaffolds collected on the ring‐shaped collector displayed anisotropic biaxial mechanical properties, suggesting that their biaxial mechanical properties are closely associated with the fiber alignment in the scaffold. Additionally, the scaffold stiffness was easily tuned by changing the composition and concentration of the polymer blend. Human valvular interstitial cells (hVICs) cultured on these anisotropic scaffolds displayed aligned morphology as instructed by the fiber alignment. Overall, we generated a library of biologically relevant fibrous scaffolds with tunable mechanical properties, which will guide the cellular alignment.

Effect of Temperature and Ionic Strength on Micellar Aggregates of Oppositely Charged Thermoresponsive Block Copolymer Polyelectrolytes.

The self-assembly of two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly(N-isopropylacrylamide) (pNIPAAM) has been investigated. The effect of the mixing ratio and total polymer concentrations on the self-assembly of the components and on the phase stability of the mixtures was studied by dynamic light scattering, electrophoretic mobility, and turbidimetry measurements in water at 20 °C. The effect of the competing electrostatic and hydrophobic interactions on the nanostructure of negatively charged electrostatically self-assembled micelles bearing a pNIPAAM corona was investigated by small-angle X-ray scattering (SAXS). The electrostatic and hydrophobic interactions were controlled independently by tuning the ionic strength (from pure water to 50 mM NaCl) and the temperature (20-50 °C) of the investigated mixtures. The SAXS data could be fitted by a spherical micelle model, which has a smoothly decaying radial profile and a Gaussian star term that describes the internal structure of the micellar structures and possible attractive interactions between the polymer chains. At high temperature, a cluster structure factor was included for describing the formation of bulky clusters of the formed micelles. At low temperature and ionic strength, the formation of micelles with a coacervate core and hydrated pNIPAAM shell was observed. The structural evolution of the self-assembled micelles with increasing ionic strength and temperature could be followed, and finally at high ionic strength and temperature, the formation of inverted micelles with a hydrophobic core and polyelectrolyte shell could be identified.

Preparation and Evaluation of Eudragit® L100 Nanoparticles Loaded Impregnated with KT Tromethamine Loaded PVA -HEC Insertions for Ophthalmic Drug Delivery.

Purpose: The purpose of the present study was to improve the ocular delivery for ketorolac tromethamine (KT) used to treat inflammation of the eye. Methods: Eudragit nanoparticles loaded with KT were prepared and incorporated in polyvinyl alcohol (PVA) and hydroxyethyl cellulose (HEC) films. Nanoparticles were characterized by Fourier transform-infrared (FT-IR), scanning electron microscopy (SEM). Physicochemical properties and encapsulation effciency were investigated for nanoparticles. Also, the inserts were evaluated for their physiochemical parameters like percentage moisture absorption, percentage moisture loss, thickness and folding endurance. Results: Mean particle size and zeta potential were in range of 153.8-217 nm and (-10.8) - (-40.7) mV, respectively. The results show that the use of a surfactant has not led to any major change on drug loading. The loading increases with the amount of polymer. The insert had a thickness varying from 0.072 ± 0.0098 to 0.0865 ± 0.0035 mm. The thicknesses of the inserts and the folding endurance increased with the total polymer concentration. The physicochemical properties showed that the Eudragit® L-100 nanoparticles loaded PVA-HEC films could be an effective carrier for KT. Conclusion: For the first time, inserts of Eudragit nanoparticles were successfully prepared for ophthalmic drug delivery system to prevent frequent drug administration and enhance patient compliance.

Concentration Insensitive Supramolecular Polymerization Enabled by Kinetically Interlocking Multiple-Units Strategy

Concentration Insensitive Supramolecular Polymerization Enabled by Kinetically Interlocking Multiple-Units Strategy

Dual-Polymer Hydraulic-Fracturing Fluids: A Synergy Between Polysaccharides and Polyacrylamides

Summary As exploration for oil and gas continues, it becomes necessary to produce from deeper formations, and to meet the challenge of low permeability and higher temperatures. Unconventional shale formations are addressed with slickwater fracturing fluids, owing to the shale's unique geomechanical properties. On the other hand, conventional formations require crosslinked fracturing fluids to properly enhance productivity. Guar and its derivatives have a history of success in crosslinked hydraulic–fracturing fluids. However, they require higher polymer loading to withstand higher–temperature environments. This leads to an increase in mixing time and additive requirements. Most importantly, as a result of high polymer loading, they do not break completely and thus generate residual–polymer fragments that can plug the formation and significantly reduce fracture conductivity. In this work, a new hybrid dual–polymer hydraulic–fracturing fluid was developed. The fluid consists of a guar derivative and a polyacrylamide–based synthetic polymer. Compared with conventional fracturing fluids, this new system is easily hydrated, requires fewer additives, can be mixed “on the fly,” and is capable of maintaining excellent rheological performance at low polymer loadings. The polymer mixture solutions were prepared at a total polymer concentration of 20 to 40 lbm/1,000 gal at volume ratios of 2:1, 1:1, and 1:2. The fluids were crosslinked with a metallic crosslinker and broken with an oxidizer at 300°F. Testing focused on crosslinker/polymer–ratio analysis to effectively lower loading while maintaining sufficient performance to carry proppant at this temperature. A high–pressure/high–temperature (HP/HT) rheometer was used to measure viscosity, storage modulus, and fluid–breaking performance. An HP/HT aging cell and HP/HT see–through cell were used for proppant settling. Fourier–transform infrared (FTIR) spectroscopy, Cryo scanning electron microscopy (Cryo–SEM), and an HP/HT rheometer were also used to understand the interaction. Results indicated that the dual–polymer fracturing fluid was able to generate stable viscosity at 300°F and 100 s−1 as well as generate a higher viscosity compared with the individual–polymer fracturing fluid. Also, properly understanding and tuning the crosslinker to the polymer ratio generated excellent performance at 20 lbm/1,000 gal. The two polymers formed an improved crosslinking network that enhanced proppant–carrying properties. This fluid also demonstrated a clean and controlled breaking performance with an oxidizer. Extensive experiments were pursued to evaluate the new dual–polymer system for the first time. This system exhibited a positive interaction between the polysaccharide and polyacrylamide families and generated excellent rheological properties. The major benefit of using a mixed–polymer system is reduced polymer loading. Lower loading is highly desirable because it reduces material cost, eases field operation, and potentially lowers damage to the fracture face, proppant pack, and formation.

Conetworks on the base of polystyrene with poly(methyl methacrylate) paired polymers

AbstractIt is found that forced (reactive) blending of polystyrene (PS) with polymethylmethacrylate (PMMA) involves the covalent binding of heterogeneous macromolecules to afford the paired polymers. For this purpose, the “anchor” N-H unsubstituted tetrazole or oxirane functional groups are preliminarily introduced in the structure of both polymers in a small amount that leads to a covalent binding of the heterogeneous macromolecules. The reaction between the modified PS and PMMA is carried out in dimethylformamide (DMF), toluene and dichloroethane (DCE) at a high total concentration of polymers (10-20 g dL-1). The process is accompanied by gel-formation to deliver cross-linked paired polymers It is established that the highest rate of the paired polymer is attained in the DCE medium, while the lowest rate is observed in DMF. For paired polymers synthesized in DMF, two glass transition temperatures (Tg) of 92°C and 104°C correspond to the original PS and PMMA, respectively. The products of forced blending of PS and PMMA in toluene have one averaged Tg value (99°C), whereas those obtained in DCE show no pronounced glass transition region at 90 ÷ 115°C. In toluene or DCE, the paired polymers are formed, which represent single-phase systems having one glass transition region.

Multiscale Porosity in Compressible Cryogenically 3D Printed Gels for Bone Tissue Engineering.

Three-dimensional (3D) printing technology has seen several refinements when introduced in the field of medical devices and regenerative medicines. However, it is still a challenge to 3D print gels for building complex constructs as per the desired shape and size. Here, we present a novel method to 3D print gelatin/carboxymethylchitin/hydroxyapatite composite gel constructs of a complex shape. The objective of this study is to fabricate a bioactive gel scaffold with a controlled hierarchical structure. The hierarchy ranges from 3D outer shape to macroporosity to microporosity and rough surface. The fabrication process developed here uses 3D printing in a local cryogenic atmosphere, followed by lyophilization and cross-linking. The gel instantly freezes after extrusion on the cold plate. The cooling action is not limited to the build plate, but the entire gel scaffold is cooled during the 3D printing process. This enables the construction of a stable self-sustaining large-sized 3D complex geometry. Further, lyophilization introduces bulk microporosity into the scaffolds. The outer shape and macroporosity were controlled with the 3D printer, whereas the microporous structure and desirable rough surface morphology were obtained through lyophilization. With cryogenic 3D printing, up to 90% microporosity could be incorporated into the scaffolds. The microporosity and pore size distribution were controlled by changing the cross-linker and total polymer concentration, which resulted in six times increase in surface open pores of size <20 μm on increasing the cross-linker concentration from 25 to 100 mg/mL. The introduction of bulk microporosity was shown to increase swelling by 1.8 times along with a significant increase in human umbilical cord mesenchymal stem cells and Saos-2 cell attachment (2×), proliferation (2.4×), Saos-2 cell alkaline phosphatase level (2×), and mineralization (3×). The scaffolds are spongy in nature in a wet state, thus making them potential implants for bone cavities with a small opening. The application of these cryogenically 3D printed compressible gel scaffolds with multiscale porosity extends to a small- as well as a large-sized open/partially open patient-specific bone defect.

Identification of the Methanogenesis Inhibition Mechanism Using Comparative Analysis of Mathematical Models.

The application of cationic polymers to enhance membrane fluxes in anaerobic membrane bioreactors has been proposed by several authors. However, literature shows contradictory results on the influence of those chemicals on the biological activity. In this research, we studied the effect of a cationic polymer on the production of methane from acetate by acetoclastic methanogens. We assessed the effect of polymer concentration on the accumulated methane production (AMP) and the specific methanogenic activity (SMA) in batch tests. Batch tests results showed lower SMA values at higher concentrations of polymer and no effect on the final AMP. Different inhibition models were calibrated and compared to find the best fit and to hypothesize the prevailing inhibition mechanisms. The assessed inhibition models were: competitive (M1a), non-competitive (M2a), un-competitive (M3a), biocide-linear (M4a), and biocide-exponential (M5a). The parameters in the model related to the polymer characteristics were adjusted to fit the experimental data. M2a and M3a were the only models that fitted both experimental SMA and AMP. Although M1a and M4a adequately fitted the experimental SMA, M1a simulations slightly deviated from the experimental AMP, and M4a considerably underpredicted the AMP at concentrations of polymer above 0.23 gCOD L−1. M5a did not adequately fit either experimental SMA and AMP results. We compared models a (M1a to M5a), which consider the inhibition by the concentration of polymer in the bulk liquid, with models b (M1b to M5b) considering the inhibition being caused by the total concentration of polymer in the reactor. Results showed that the difference between a and b models' simulations were negligible for all kinetic models considered (M1, M2, M3, M4, and M5). Therefore, the models that better predicted the experimental data were the non-competitive (M2a and M2b) and un-competitive (M3a and M3b) inhibition models, which are biostatic inhibition models. Consequently, the decreased methanogenic activity caused by polymer additions is presumably a reversible process

Small and large amplitude oscillatory shear behavior of supramolecular gels based on dopamine-boronic acid interactions

Blends of polymer solutions of poly(N-isopropylacrylamide-co-dopamine methacrylamide) (NIDO) and poly(N-isopropylacrylamide-co-4-vinylphenylboronic acid) (NIBA) in aqueous solutions were studied rheologically at pH ≈ 9. The functional catechol group of NIDO and the boronic acid group of NIBA could form coordinative complexes, which are strong, yet could be broken by high deformation, while they could reconfigure quickly within 1 min on a macroscopic scale. The linear and nonlinear behaviors of these materials vary significantly for different component mixing ratios. At a total polymer concentration of 10 w/v %, the 1:1 mixture (wNIBA/wNIDO) of the two polymers yields the strongest gel compared with asymmetric blends. The nonlinearity intensities (In/I1) of the materials increase proportionately with strain γ0, but once a significant nonlinearity is reached, they show lower nonlinearity intensities, which is unlike regular nonassociative single phase polymer melts and solutions. Interaction of polymer NIDO and NIBA and the formed supramolecular gels' properties will be clarified by large amplitude oscillatory shear characterization.Blends of polymer solutions of poly(N-isopropylacrylamide-co-dopamine methacrylamide) (NIDO) and poly(N-isopropylacrylamide-co-4-vinylphenylboronic acid) (NIBA) in aqueous solutions were studied rheologically at pH ≈ 9. The functional catechol group of NIDO and the boronic acid group of NIBA could form coordinative complexes, which are strong, yet could be broken by high deformation, while they could reconfigure quickly within 1 min on a macroscopic scale. The linear and nonlinear behaviors of these materials vary significantly for different component mixing ratios. At a total polymer concentration of 10 w/v %, the 1:1 mixture (wNIBA/wNIDO) of the two polymers yields the strongest gel compared with asymmetric blends. The nonlinearity intensities (In/I1) of the materials increase proportionately with strain γ0, but once a significant nonlinearity is reached, they show lower nonlinearity intensities, which is unlike regular nonassociative single phase polymer melts and solutions. Interaction of polymer NIDO...

Effect of Solution Composition Variables on Electrospun Alginate Nanofibers: Response Surface Analysis.

Alginate is a promising biocompatible and biodegradable polymer for production of nanofibers for drug delivery and tissue engineering. However, alginate is difficult to electrospin due to its polyelectrolyte nature. The aim was to improve the ‘electrospinability’ of alginate with addition of exceptionally high molecular weight poly(ethylene oxide) (PEO) as a co-polymer. The compositions of the polymer-blend solutions for electrospinning were varied for PEO molecular weight, total (alginate plus PEO) polymer concentration, and PEO proportion in the dry alginate–PEO polymer mix used. These were tested for rheology (viscosity, complex viscosity, storage and loss moduli) and conductivity, and the electrospun nanofibers were characterized by scanning electron microscopy. One-parameter-at-a-time approach and response surface methodology (RSM) were used to optimize the polymer-blend solution composition to obtain defined nanofibers. Both approaches revealed that the major influence on nanofiber formation and diameter were total polymer concentration and PEO proportion. These polymer-blend solutions of appropriate conductivity and viscosity enabled fine-tuning of nanofiber diameter. PEO molecular weight of 2–4 million Da greatly improved the electrospinnability of alginate, producing nanofibers with >85% alginate. This study shows that RSM can be used to design nanofibers with optimal alginate and co-polymer contents to provide efficient scaffold material for regenerative medicine.

Optimisation of the microencapsulation of lavender oil by spray drying

Background: Lavender oil consists of around 100 components and is susceptible to volatilisation and degradation reactions.Aim: Microencapsulate lavender oil by spray drying using a biocompatible polymeric blend of gum acacia and maltodextrin to protect the oil components. Effect of total polymer content, oil loading, gum acacia, and maltodextrin proportions on the size, yield, loading, and encapsulation efficiency of the microparticles was investigated.Methods: Morphology and oil localisation within microparticles were assessed by confocal laser scanning electron microscope. Structural preservation and compatibility were assessed using Fourier transform infra-red spectroscopy, differential scanning calorimetry, and gas chromatography–mass spectrometry.Results: Lavender microparticles of size 12.42 ± 1.79 µm prepared at 30 w/w% polymer concentration, 16.67 w/w% oil loading, and 25w/w% gum acacia showed maximum oil protection at high loading (12 mg w/w%), and encapsulation efficiency (77.89 w/w%).Conclusion: Lavender oil was successfully microencapsulated into stable microparticles by spray drying using gum acacia/maltodextrin polymeric blend.

Concentration-dependent switch between chain association and dissociation of oppositely charged weak polyelectrolytes in solution

Joint solutions of oppositely charged weak polyelectrolytes are considerably less studied than their strong counterparts; as a result, their thermodynamic understanding is still unsatisfactory. This shortcoming hampers the development of a general picture about the physical properties of these mixtures, which further hampers their use to design new materials. To close this gap, we investigate the ternary system ethanol/polyacid/polybase (polyacid: methacrylic acid containing copolymer; polybase: N,N-dimethylaminoethyl methacrylate containing terpolymer) with respect to its demixing and viscometric behavior. Complete homogeneity can only be reached if the total polymer concentration remains below 0.005 g dL−1. The locations of the tie lines in the phase diagram reveal that the interpolymer contacts are favorable at low polymer concentrations but unfavorable at high concentrations; viscosity measurements corroborate these findings. Adding either acid or base to the solvent extends the region of homogeneity, where low concentrations of HCl split the two-phase region into two separate parts. This phenomenon is rationalized in terms of concentration-dependent changes in the degree of ionization of the polybase.

Synthesis of Au (III) polyacrylates and study of their tumoricidal activity

Aurumacryl is an incomplete metal salt of poly(acrylic acid) that exhibits hemostatic activity and inhibits the growth of transplantable carcinomas in vivo. The samples of aurumacryl synthesized following the original technique are insufficiently soluble, which complicates the study of the mechanisms involved in their synthesis and underlying their cytotoxic effect. The aim of this work was to study the impact of the following factors on aurumacryl properties: the molecular weight of the polyacrylate polymer in a range between 2 and 1,000 kDa, the presence of a counterion H+ or Na+, the molar ratio of AuCl– to the polyacrylate polymer (1 : 5 and 1 : 10), the total concentration of the polyacrylate polymer during synthesis (0.1 and 3%), and the type of drying (lyophilization). By comparing the cytotoxicity of aurumacryl samples with significantly different molar ratio of gold ions to the polyacrylate polymer against human breast carcinoma cells (MCF-7), we established that the proportion of the polymer and its molecular weight in the sample do not affect the biological properties of the synthesized substance. Using UV spectroscopy, we revealed that the concentration of Au (III) ions in aurumacryl determines its cytotoxicity.

Development and functional characterization of composite freeze dried wafers for potential delivery of low dose aspirin for elderly people with dysphagia

The impact of demographic ageing is likely to be of major significance in the coming decades due to low birth rates and higher life expectancy. Older people generally require more prescribed medicines due to the presence of multiple conditions such as dysphagia which can make swallowing medicines challenging. This study involves the development, characterization and optimization of composite wafers for potential oral and buccal delivery of low dose aspirin to prevent thrombosis in elderly patients with dysphagia. Blank (BLK) wafers (no loaded drug) were initially formulated by dissolving combinations of metolose (MET) with carrageenan (CAR) and MET with low molecular weight chitosan (CS) in different weight ratios in water, to identify optimum polymer combinations. However, drug loaded (DL) wafers were prepared using 45% v/v ethanol to help complete solubilization of the aspirin. The formulations were characterized using texture analyzer (hardness, mucoadhesion), scanning electron microscopy (SEM), X-ray diffractometry (XRD), attenuated total reflectance – Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and swelling capacity. Wafers with higher total polymer concentration were more resistant to penetration (MET:CAR 1:1 samples B2, C2) and MET:CS 1:1 (sample E2) and MET:CS 3:1 (sample F2) and also depended on the ratios between the polymers used. From the characterization, samples C2, B2, E2 and F2 showed the most ideal characteristics. XRD showed that BLK wafers were amorphous, whilst the DL wafers were crystalline due to the presence of aspirin. SEM confirmed the presence of pores within the polymer matrix of the BLK wafers, whilst DL wafers showed a more compact polymeric matrix with aspirin dispersed over the surface. The DL wafers showed a good flexibility required for transportation and patient handling and showed higher swelling capacity and adhesion values with phosphate buffer saline (PBS) than with simulated saliva (SS). Drug dissolution studies showed that aspirin was rapidly released in the first 20 min and then continuously over 1 h. FTIR confirmed the interaction of aspirin with the polymers evidenced by peak shifts around 1750 cm−1 and the broad peak between 2500 and 3300 cm−1. Lyophilized CAR: CS 1:3 (sample DL13), MET:CS 1:3 (sample DL8) and MET:CAR 3:1 (sample DL1) wafers seem to be a very promising system for the administration of low dose aspirin for older patients with dysphagia.

Fully-Zwitterionic Polymer-Supported Ionogel Electrolytes Featuring a Hydrophobic Ionic Liquid.

In this report, fully-zwitterionic (ZI) copolymer scaffolds for ionogel electrolytes have been synthesized via in situ photopolymerization using various molar ratios of 2-methacryloyloxyethyl phosphorylcholine (MPC) and sulfobetaine vinylimidazole (SBVI) within the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI). Depending on the chemical composition of the ZI scaffold, ionogel room temperature ionic conductivities are found to vary between 2.5 and 6.7 mS cm-1 at a fixed 20 mol % total polymer content. Compressive elastic moduli also exhibit a strong dependence on the co-monomer ratio, with values between 23 kPa and 11 MPa observed because of different degrees of ZI physical cross-linking. These results, together with NMR chemical shift analysis, suggest that the phosphorylcholine ZI group of MPC interacts more strongly with EMI TFSI, while SBVI prefers to self-aggregate and form dipole-dipole cross-links in the ionic liquid (IL). Self-diffusivity measurements of the EMI+ cations and TFSI- anions in both ionogel and ZI solution samples confirm that slower ion diffusion in MPC-containing systems is due to attractive zwitterion/IL interactions, and not merely reduced mobility in the presence of a polymeric scaffold. This work highlights the importance of relative zwitterion/IL and ZI dipole-dipole interactions on the properties of a novel class of fully-ZI polymer-supported ionogel electrolytes containing a hydrophobic IL suitable for future electrical energy storage applications.

Formulation and In vitro Evaluation of Unfolding Type Expandable Gastroretentive Film of Enalapril Maleate

The present work was based on the development and characterization of unfolding type gastroretentive dosage form appropriate for controlled release of enalapril maleate. Drug loaded films were prepared by solid dispersion technique using methocel K15 and eudragit RSPO and eudragit RLPO as polymers and polyethylene glycol 400 (PEG 400) as the plasticizer. The film folded in a capsule shell was shown to unfold in the gastric juice and provide drug release up to 12 h in the acidic medium. Formulations provided satisfactory unfolding characteristics allowing expansion to remain in the stomach. Formulation containing above 60% content of eudragit RSPO and eudgrait RLPO combination of total polymer content provided satisfactory film integrity over 12 hours. The result revealed that formulation F1 showed a minimum percentage of drug release of 63.41% followed by formulation F2, F3, F4 and F5 with 66.76%, 80.21%, 83.26% and 86.92% release in 8 hour respectively. Formulation with high proportion of eudragit RLPO and RSPO combination in total polymer content was found to be slow in drug release and lower the release from the polymeric film over time. As the concentration of HPMC K 15 in total polymer content increased the release rate of enalapril maleate as well as % release from the polymeric film also increased over time. Most of the formulation followed Higuchi release kinetics followed by Korsmeyer release kinetics. The drug release mechanism from the film follows Fickian and Non Fickian release kinetics. The films were evaluated for mechanical properties, in vitro drug release and unfolding behavior based on the mechanical shape memory of polymers. Absence of drug polymer interaction and uniform drug dispersion in the polymeric layers was revealed by DSC, FT-IR and SEM studies.Bangladesh Pharmaceutical Journal 20(2): 148-154, 2017

Decoupling the Ionic Conductivity and Elastic Modulus of Gel Electrolytes: Fully Zwitterionic Copolymer Scaffolds in Lithium Salt/Ionic Liquid Solutions

AbstractA critical barrier to overcome in the development of solid‐state electrolytes for lithium batteries is the trade‐off between sacrificing ionic conductivity for enhancement of mechanical stiffness. Here, a physically cross‐linked, polymer‐supported gel electrolyte consisting of a lithium salt/ionic liquid solution featuring a fully zwitterionic (ZI) copolymer network is introduced for rechargeable lithium‐based batteries. The ZI scaffold is synthesized using a 3:1 molar ratio of 2‐methacryloyloxyethyl phosphorylcholine and sulfobetaine vinylimidazole, and the total polymer content is varied between 1.1 and 12.5 wt%. Room‐temperature ionic conductivity values comparable to the base liquid electrolyte (≈1 mS cm−1) are achieved in ZI copolymer‐supported gels that display compressive elastic moduli as large as 14.3 MPa due to ZI dipole–dipole cross‐links. Spectroscopic characterization suggests a change in the Li+coordination shell upon addition of the zwitterions, indicative of strong Li+···ZI group interactions. Li+transference number measurements reveal an increase in Li+conductivity within a ZI gel electrolyte (nearly doubles). ZI gels display enhanced stability against Li metal, dendrite suppression, and suitable charge–discharge performance in a graphite|lithium nickel cobalt manganese oxide cell. Fully ZI polymer networks in nonvolatile, ionic liquid‐based electrolytes represent a promising approach toward realizing highly conductive, mechanically rigid gels for lithium battery technologies.

Nanostructured Hydrogels by Blend Electrospinning of Polycaprolactone/Gelatin Nanofibers.

Nanofibrous membranes based on polycaprolactone (PCL) have a large potential for use in biomedical applications but are limited by the hydrophobicity of PCL. Blend electrospinning of PCL with other biomedical suited materials, such as gelatin (Gt) allows for the design of better and new materials. This study investigates the possibility of blend electrospinning PCL/Gt nanofibrous membranes which can be used to design a range of novel materials better suited for biomedical applications. The electrospinnability and stability of PCL/Gt blend nanofibers from a non-toxic acid solvent system are investigated. The solvent system developed in this work allows good electrospinnable emulsions for the whole PCL/Gt composition range. Uniform bead-free nanofibers can easily be produced, and the resulting fiber diameter can be tuned by altering the total polymer concentration. Addition of small amounts of water stabilizes the electrospinning emulsions, allowing the electrospinning of large and homogeneous nanofibrous structures over a prolonged period. The resulting blend nanofibrous membranes are analyzed for their composition, morphology, and homogeneity. Cold-gelling experiments on these novel membranes show the possibility of obtaining water-stable PCL/Gt nanofibrous membranes, as well as nanostructured hydrogels reinforced with nanofibers. Both material classes provide a high potential for designing new material applications.

(Keynote) Preparation and Structural Investigation of Linear and 4-Arm Poly(ethylene glycol) (2 x 4 PEG) Gels

Gel is a 3D polymer network holding solvent molecules inside its network. There are two major heterogeneities in gels. One is spatial heterogeneity, and the other is topological heterogeneity. The spatial heterogeneity is introduced by random cross-linking, so the network structure has both sparse and dense region. The spatial heterogeneity is observed as excess scattering in a light, X-ray, or neutron scattering experiment. On the other hand, the topological heterogeneity is related to the presence of dangling chains, loop structure, and entanglements inside the network, and is investigated by viscoelasticity and/or swelling experiments, or by other means, such as NMR. Because of these inhomogeneities, gels have seldom been applied to structural materials because of their poor mechanical properties. Hence, realization of ideal model networks free from heterogeneities has been strongly anticipated. Sakai et al. succeeded in fabrication of near ideal polymer networks called “Tetra-PEG gel”.[1] A Tetra-PEG gel is synthesized from two complementary end-functionalized poly(ethylene glycol) (PEG) which is able to react each other. It is pointed out that the Tetra-PEG gel has insignificant small spatial homogeneity and negligible topological heterogeneity, respectively by small angle scattering[2] and mechanical test.[3] Recently, we extended the above-mentioned method and succeeded in fabrication of multiple model network gels consisting of alternating tetra-functional poly(ethylene glycol)s (PEGs) and bis-functional linear PEGs (2 x 4 gels), where the molecular weight of linear PEG was varied from 200 Da to 20000 Da while that of tetra-functional PEG component was fixed to be 20000 Da.[4] The same level of homogeneities in the network structure as those of Tetra-PEG gels has been confirmed by dynamic light scattering (DLS) and dynamic viscoelastic measurements. Advantages of 2 x 4 gels are that one can independently tune the cross-link density (by the concentration of tetra-functional PEG) and the total polymer concentration. By using a series of 2 x 4 gels, we examined the concentration/cross-link density dependence of the correlation blob, the elastic blob, and geometric blob. We will discuss the scaling rules of these blob sizes as a function of polymer/cross-linker concentrations. Sakai, T. et al, Macromolecules 2008, 41, 5379.Matsunaga, T. et al, Macromolecules 2009, 42, 1344.Akagi, Y. et al, Macromolecules 2010, 43, 488.Tsuji, Y. et al., Gels 2018, 4, 50.