Gastro‐resistant controlled release of OTC encapsulated in alginate/chitosan matrix coated with acryl‐EZE® MP in fluidized bed

A gastro‐resistant system of acryl‐EZE® MP coated alginate/chitosan microparticles was developed to improve the controlled release of oxytetracycline (OTC). Microparticles were obtained by complex coacervation and, thereafter, were coated using fluidized polymer dispersion with acryl‐EZE® MP solution. OTC distribution inside the microparticles was determined by multiphoton confocal microscopy, demonstrating the efficiency of encapsulation process. In vitro OTC release kinetic was performed in order to obtain the release profile in gastric and intestinal simulated fluids. A fast initial release, or burst effect, was observed with uncoated microparticles loaded with OTC in gastric conditions. When a 50% mass increase in acryl‐EZE® MP coating was achieved, OTC release in acidic medium was greatly reduced, resulting in the expected gastro‐resistant effect. Different mathematical models were applied to describe the drug diffusion across the polymer matrix. The Logistic model was the best tool to interpret the experimental data in most of the systems studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40444.     

Fabrication of flexible UV nanoimprint mold with fluorinated polymer-coated PET film

UV curing nanoimprint lithography is one of the most promising techniques for the fabrication of micro- to nano-sized patterns on various substrates with high throughput and a low production cost. The UV nanoimprint process requires a transparent template with micro- to nano-sized surface protrusions, having a low surface energy and good flexibility. Therefore, the development of low-cost, transparent, and flexible templates is essential. In this study, a flexible polyethylene terephthalate (PET) film coated with a fluorinated polymer material was used as an imprinting mold. Micro- and nano-sized surface protrusion patterns were formed on the fluorinated polymer layer by the hot embossing process from a Si master template. Then, the replicated pattern of the fluorinated polymer, coated on the flexible PET film, was used as a template for the UV nanoimprint process without any anti-stiction coating process. In this way, the micro- to nano-sized patterns of the original master Si template were replicated on various substrates, including a flat Si substrate and curved acryl substrate, with high fidelity using UV nanoimprint lithography.     

1-脱氧野尻霉素控释微丸的制备及其性能研究

以1-脱氧野尻霉素为原料,羟丙基甲基纤维素钛酸酯作为控释包衣材料,以微晶纤维素为芯材制备空白丸芯,羟丙基甲基纤维素作为黏合剂进行上药,采用流化床进行包衣制备了载药1-脱氧野尻霉素控释微丸。制备后的微丸装入胶囊中。SEM分析表明,制备的控释微丸呈近圆球状,表面光滑、均匀紧致,横切面丸芯、上药层与控释层清晰可见,厚度均匀一致,说明包衣工艺稳定。控释胶囊中1-脱氧野尻霉素含量均匀度好且杂质符合规定。在体外溶出试验中,分别在pH值1.2、4.5和6.8的溶出介质中,1-脱氧野尻霉素制备控释微丸与1-脱氧野尻霉素速释片溶出曲线有很大的差异,在1~12h呈现零级线性释放,控释效果良好。产品分别在高湿度92.5%、强光照（4500±500） lx和高温条件下存放30d,存放后产品稳定性良好。     

Preparation and Characterization of Asymmetric Composite Polymer Electrolytes for Lithium Metal Polymer Batteries

Summary An asymmetric composite polymer electrolyte composed of porous polymer matrix which micro-porous layer based on the polyethylene acts as a support and submicro-porous layer is introduced on one side of the micro-porous layer through a coating process and ethylene carbonate/dimethyl carbonate/LiPF₆ liquid solution occupying the pores has been prepared. The maximum ionic conductivity of this system was 7.0 × 10^-3 S/cm at the ambient temperature. The conductivity seems to be significantly affected by the uptake amount of liquid electrolyte within the matrix.     

Surface modification of coil coatings with thin plasma polymer films structure and stability

Plasma deposition of a thin top layer with tailored properties is an effective strategy of modification of the organic coating surface. Thin plasma polymer layers are candidates and can provide superior hardness, scratch resistance, modified surface hydrophobicity and easy to clean properties.The present work studies the stability of thin plasma polymer films deposited as top layer on polyurethane coil coating systems. Microwave, hollow cathode and radio frequency plasma polymerization reactors were employed in order to deposit a thin SiO_x based plasma polymer layer.The plasma film stability was studied using surface analysis techniques, ex situ and in situ atomic force microscopy and scanning electron microscopy. Energy dispersive spectroscopy, FTIR spectroscopy and optical measurements confirm the composition and plasma layer properties. The structure of the plasma layers was investigated by means of transmission electron microscopy.The surface morphology together with composition evolution allows the study of the stability of the different coatings. The structure examination of the formed plasma polymer film offers good clarification for coating failure. Decrease of the operating pressure during plasma polymerization and oxygen concentration in precursor mixture lead to formation of compacter layer with higher stability. Introduction of fluorine-containing precursor also increases the anti-weathering performance of the plasma polymer films.     

Reinforcement of polymers with carbon nanotubes. The role of an ordered polymer interfacial region. Experiment and modeling

Significant increases in the Young's modulus of nanotube–polymer composites have been associated with the formation of an ordered polymer layer coating the nanotubes. Polyvinyl alcohol (PVA) is known to display nanotube-induced ordering. It is used here as a model matrix to investigate how the polymer coating influences the mechanical reinforcement of the composite material. Young's modulus and calorimetry measurements were carried out on films of PVA-based composites reinforced with different types of nanotubes. An unmistakable correlation between polymer ordering and reinforcement was found. This is supported by the introduction of a model capable of establishing, on quantitative grounds, how the ordered phase affects the increase in the Young's modulus. Rather than acting as intrinsically stiffer reinforcing agents, our results suggest that the major role played by the nanotubes in improving the mechanical properties of composites is to nucleate an ordered polymer coating. It is the presence of this stiff ordered phase that dominates the reinforcement mechanism.     

Spectroscopic studies of spin-coated dye-in-polymer films. On the relationship between compatibility and aggregation of small molecules in polymer matrices

Dye-in-polymer (DIP) films of various concentrations of I (a p-N,N-dialkyl-aminobenzylidenemalononitrile derivative) in four polymers of different dye-polymer compatibilities have been prepared by spin-coating technique using a wide range of coating speeds (600–8000 rpm). The aggregation of dye molecules in polymer matrix was studied by electronic spectroscopy. The dye-polymer compatibility of various DIP systems was examined by d.s.c. Our results indicate that there exists a staturated concentration of I in each polymer and this saturated concentration decreases as the dye-polymer compatibility decreases, e.g. it decreases from ～20% in poly(vinyl acetate) and in poly(isobutyl methacrylate) to ～10% in styrene/isobutyl methacrylate (8:2) copolymer to ～5% in polystyrene. At dye concentrations lower than this saturated concentration, the degree of dye aggregation is not sensitive to varying spin-coating speeds. At dye concentrations higher than this saturated concentration, the degree of dye aggregation depends on the degree of dye-polymer incompatibility and on the spin-coating speed. The significance of the present work in solvent coating technology of small molecule/polymer systems, in general, will be discussed. Finally, the T_g's of various DIP systems were found not to correlate with the dye concentration (by weight). This is attributable to the strong dye-dye interaction of I inside the polymer matrix.     

Optimization of preparation of matrix pellets containing ethylcellulose

The aim of this study was to investigate the effects of the parameters of the spheronization and the nature of the wetting liquid on the properties of matrix pellets prepared by extrusion and spheronization. Ethylcellulose was used as a matrix former, microcrystalline cellulose as a filler, atenolol as a model active agent, and water and a water–ethanol mixture as liquids. The formation of the pellets and the interactions of the components were evaluated via mechanical, dissolution and morphological studies on the pellets. A factorial design was used to determine the effects of the evaluated factors. It was concluded that significant effects were exerted not only by the operational parameters, but also by the nature of the liquid. The breaking hardness and the dissolution revealed that the ethanol in the liquid caused changes in the wettability of the components and consequently in the matrix structure. This was explained by a comparison of the relative importance of the factors. The alterations induced by ethanol were preferable in the dissolution, because the possibility of the burst effect in the first phase of dissolution can then be avoided. However, it is not favourable as concerns the sphericity and the mechanical properties of the pellets.     

Application of hot-melt coating for controlled release of propranolol hydrochloride pellets

Waxes are available in various lyophilicity, and they can be used to regulate the release from multiunit-controlled release pellets. In this study, the application of saturated polyglycolysed glyceride (Gelucire® 50/02) and glycerol palmitostearate (Precirol® ATO5) as drug release regulators for propranolol pellets and the kinetics of release were investigated. Propranolol pellets containing 60% microcrystalline cellulose (Avicel® PH101) were prepared by using direct pelletization technique in a fluidized-bed rotary granulator (Glatt GPCG1). The pellets of 16:18 mesh size were collected and coated with the molten wax(es) at various ratios and thicknesses in a fluidized-bed top spray coater (Glatt GPCG1). The dissolution was determined using test method for Propranolol Extended Release Capsules USP 24 and was found to be very rapid with the uncoated pellets. The dissolution of coated pellet was decreased with the increases in Precirol ATO5 proportion and coating thickness. Plot of log % drug release vs. reciprocal of time showed a good linear relationship. The k value derived from the slope of the plot and designated as a “diffusive resistance constant” linearly increased with the coating level. The findings indicated that drug release could be adjusted by varying the ratio of Precirol® ATO5 to Gelucire® 50/02 as well as the thickness of the coat.     

Development of a novel smart carrier for drug delivery: Ciprofloxacin loaded vaterite/reduced graphene oxide/PCL composite coating on TiO2 nanotube coated titanium

In the field of orthopaedic implants, post-surgery infections and biocompatibility are the most challenging obstacles. Sustained and controlled antibiotic release is a key factor in novel drug delivery systems. A novel drug delivery system combined with vaterite microsphere, graphite oxide (GO), reduced graphene oxide (rGO) incorporated in a polycaprolactone (PCL) matrix on TiO₂ nanotube coated Ti (TNT-Ti) is established. Anodization was employed to develop TiO₂ nanotubular arrays on Ti. Ciprofloxacin hydrochloride (CPF–HCl) loaded vaterite microspheres were synthesized by in situ precipitation method. Deposition of vaterite/PCL, vaterite-GO/PCL and vaterite-rGO/PCL composite coating on TNT-Ti was carried out by dip coating method. The composite coatings were characterized for their phase content, morphological features and functional groups. Among the three types of composite coatings, vaterite-rGO/PCL composite coating is found to be capable of encapsulating CPF-HCl to a level of 75.14 μg. The drug release profile of CPF-HCl from the vaterite-rGO/PCL composite coating exhibits a controlled release amounting to only 35.02 % of release at the end of 120 h. The vaterite-rGO/PCL composite coating exhibits a low dissolution rate and possesses adequate bioactivity in HBSS and SBF solutions at 37 °C for 14 and 10 days, respectively. The in situ loaded CPF-HCL drug on vaterite microspheres, PCL polymer matrix and GO/rGO nanofillers does not affect the cytocompatibility and all the composite coatings supported cell viability and proliferation. The ability of vaterite-rGO/PCL composite coating to provide a slow and steady release of antibiotics with sufficient bioactivity and biocompatibility at the tissue implant interface makes it a promising for osteomyelitis infection of bone tissue implant materials.     

Synthesis and electrochemical evaluation of polypyrrole coatings electrodeposited onto AA-2024 alloy

Polypyrrole coating was successfully deposited on anodized 2024 unclad aluminum alloy showing that the presence of the anodic film is the key factor to ensure better adhesion to the polymer coating. Corrosion resistance of the conductive polymer layers grown for three and five cycles were evaluated in a 3 wt.% NaCl solution using polarization curves and impedance spectroscopy. It was found that the thermally treated polymer coating with higher thickness (five cycles) exhibited the best corrosion performance. This best coating shifts the corrosion potential towards nobler values, about 650 mV, and the exchange current density decreases two orders of magnitude regarding the anodic layer. The partial reduction of the structure of the polymer promoted by the thermal treatment plays a key role in the corrosion resistance of the coating allowing to the thermally treated polymer layer to act as a physical barrier against corrosion.     

Electrochemical synthesis and characterization of carbon nanotube/modified polypyrrole hybrids using a cavity microelectrode

A cavity microelectrode (CME) was used to perform an electrochemical synthesis of hybrid materials made of carbon nanotubes (CNTs) and conducting polymers. The confinement of the CME is used to produce a uniform nanometric coating of an electronically conducting polymer such as poly(N-methylpyrrole) (Pmpy) on multiwalled carbon nanotubes. The CME also allows easy characterization of the presence of the polymer layer on the surface of the CNTs by cyclic voltammetry. Transmission electron microscopy allowed us to measure the thickness and confirm the homogeneity of the Pmpy coating around the CNTs. Finally Raman spectroscopy brings additional information on the electrogenerated hybrid materials.     

A new method for characterizing the release of drugs from single agglomerates

The purpose of this article is twofold; firstly, to introduce a new method for characterizing the release of drugs from single agglomerates and, secondly, to use the proposed method to investigate drug release from pellets made of microcrystalline cellulose, containing either sodium chloride or salicylic acid as model drug. The proposed experimental setup utilizes a recirculating flow-through system for the dissolution medium, and uses conductivity measurements to monitor its drug concentration. Pellets of two different porosities are investigated, and two different dissolution-medium flow rates are used. The mean dissolution time was used as a model-independent measure of the overall release rate. Analysis of variance was performed with two levels for each of the three factors drug solubility, pellet porosity, and dissolution-medium flow rate. Drug solubility and pellet porosity had highly significant effects on the drug release (p<0.001), whereas flow rate had no significant effect. It was also possible to extract physicochemical parameters characterizing the release process (effective diffusion coefficients, drug solubilities and dissolution rates), which in general showed good agreement with expected results. The proposed method yielded single-pellet release data of sufficient quality for meaningful conclusions to be drawn, even though the drug content of each pellet was as low as g.     

Resistance of paint coatings to multiple solid particle impact: effect of coating thickness and substrate material

A novel technique has been developed to determine the resistance of paint coatings to multiple solid particle impact (i.e. solid particle erosion). The effect of paint layer thickness on erosion resistance was evaluated for two acrylic automotive topcoats. These coatings displayed a two-stage response to erosion. Initially, their thickness was reduced progressively, but once a critical thickness was reached the remaining coating was removed by individual impacts. A simple model is proposed to describe this behaviour. A new measure, specific erosion resistance, which takes account of the coating thickness, is defined to allow coatings with different thicknesses to be compared and has been applied to several industrially sprayed automotive clearcoats on both steel and polymer (TPO) substrates. The clearcoats exhibited significantly higher specific erosion resistance when applied to polymer substrates.     

Dynamic mechanical studies of a highly filled composite structure: A lightweight coated paper

A composite sandwich structure, consisting of a paper sheet as a middle layer and two porous coating layers of a highly filled acrylate–styrene–butadiene copolymer, has been studied by means of a dynamic mechanical test in torsion. Stiffness and mechanical damping, tan δ, were recorded over the temperature region where the latex polymer exhibits a glass transition. The mechanical damping decreases with increasing filler content in the coating. Variations in the thickness of the coating layers did not influence the mechanical damping. The glass transition temperature of the latex polymer increases with increasing volume fraction of filler at high filler contents as an effect of filler–matrix interaction. The outer layers partly penetrate into the middle layer, as indicated by thickness measurements on the coated paper. A theoretical comparison of the peak heights of the mechanical damping using lamination theory shows a discrepancy in the experimental results. If penetration of the outer layer is allowed for, i.e., if using a thicker outer layer of the composite in the calculations, a favorable correlation between the theoretical and the experimental results is obtained. © 1993 John Wiley & Sons, Inc.     

In situ atomic force microscopy investigation of copper behaviour and polypyrrole deposition from salicylate medium

The morphological modifications accompanying the electrochemical behaviour of copper in aqueous salicylate solution, have been investigated by in situ atomic force microscopy (AFM), with the purpose of elucidating the role of salicylate ions during polypyrrole electrodeposition onto this oxidisable metal.The surface changes revealed by in situ AFM images, are in agreement with previous attributed electrochemical processes, namely the formation of a non-uniform passivating layer, which does not completely block the copper surface. The presence of such layer prevents a strong anodic copper dissolution without hinder the pyrrrole oxidation. Pyrrole electropolymerization process has been also followed in real-time by AFM, and occurs through the formation of a first polymer layer, which follows the initial copper surfaces irregularities and is characterized by polypyrrole round nodules of different sizes, whereas for thick polymer films the influence of substrate defects is not detected.     

Mixed powder coating film using thermoplastic polyester and its alkaline resistance

To improve alkaline resistance, a newly mixed powder coating film using thermoplastic polyethylene terephthalate (PET) was investigated. Two kinds of polyvinyl butyral (PVB) and two kinds of polyamide (PA) were chosen as the secondary polymer. The melting temperatures (T _ms) of these materials were lower than that of primary PET polymer so the mixed powder coating was able to form a dual phase film through a fluidized bed coating process. Microscope and Fourier transform infrared spectroscopy (FTIR) observations revealed that the dual phase structure was indeed successfully formed and there was a secondary layer over the entire surface area of the film. This mixed powder coating film significantly enhanced the alkaline resistance to an environment filled with NaOH solution at 40°C in which a secondary material would be effective in protecting the film. With regard to both alkaline resistance and film formability, PET/PVB was superior to the PET/PA mixture.     

Failure mechanism of thin Al2O3 coatings grown by atomic layer deposition for corrosion protection of carbon steel

Combined analysis by electrochemical impedance spectroscopy (EIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) of the corrosion protection provided to carbon steel by thin (50 nm) Al₂O₃ coatings grown by atomic layer deposition (ALD) and its failure mechanism is reported. In spite of excellent sealing properties, the results show an average dissolution rate of the alumina coating of ∼7 nm h⁻¹ in neutral 0.2 M NaCl and increasing porosity of the remaining layers with increasing immersion time. Alumina dissolution is triggered by the penetration of the solution via cracks/pinholes through the coating to the substrate surface where oxygen reduction takes place, raising the pH. At defective substrate surface sites of high aspect ratio and concentrated residual mechanical stress (along scratches) presumably exposing a higher steel surface fraction, localized dissolution of the coating is promoted by a more facile access of the solution to the substrate surface enhancing oxygen reduction. De-adhesion of the coating is also promoted in these sites by the ingress of the anodic dissolution trenching the steel surface. Localized corrosion of the alloy (i.e. pitting) is triggered prior to complete dissolution of the alumina film on the elsewhere still coated surface matrix.     

Densification of Alumina-Silicon Carbide Powder Composites: I, Effects of a Polymer Coating on Silicon Carbide Particles

One possible approach to improving the densification of powder composites containing a major crystalline phase which densifies (e.g., Al₂O₃) and a difficult-to-sinter phase (e.g., SiC) is to accommodate the matrix volume shrinkage with a "disappearing" polymer coating. A polymer coating prevents contact between the nonsinterable particles and the surrounding matrix. The coating can be burned off before sintering, allowing the matrix phase to "shrink-fit" around the nonsinterable particles during sintering. The effects of a polymer coating on the densification of a two-phase particle system were tested using SiC powder dispersed in an Al₂O₃ matrix. The composites processed with a polymer coating showed more densification during equivalent firing cycles than did those processed without a polymer coating. Densification during sintering was approximately proportional to the amount of polymer adsorbed on SiC, suggesting that the Al₂O₃ matrix did shrink-fit into the gaps between the SiC particles and the surrounding Al₂O₃ matrix. Differences in the pore-size distributions of polymercoated green compacts and uncoated compacts indicated a perturbation of the green microstructure by the gaps. The estimated average thickness of the gap is approximately 20 nm, ∼8% of the average radius of the SiC powder used in this study.     

Developing Interfacial Carbon-Boron-Silicon Coatings for Silicon Nitride-Fiber-Reinforced Composites for Improved Oxidation Resistance

C-B-Si coatings were formed on a Si₃N₄ fiber using chemical vapor deposition and embedded in a Si-N-C matrix using polymer impregnation and pyrolysis. The boron-containing layer was anticipated to form borosilicate glass and seal oxygen-diffusion passes. Two types of C-B-Si coatings were tested on the fiber–matrix interface, and they improved the oxidation resistance of the composite. The first coating was multilayered: a crystalline sublayer composed of B-Si-C was sandwiched between two graphitelike carbon sublayers. The second coating was a graphitelike carbon layer containing a small amount of boron and silicon. The carbon (sub)layer of both coatings weakened the fiber–matrix bonding, giving the composites a high flexural strength (1.1 GPa). The composites retained 60%–70% of their initial strength, even after oxidation at 1523 K for 100 h. The mechanism for improved oxidation resistance was discussed through the microstructure of the interface, morphology of the fracture surface, and oxygen distribution on a cross section of the oxidized composite.