Facile fabrication of chitosan active film with xylan via direct immersion

Chitosan film was immersed in NaOH solution with xylan to simply prepare active chitosan/xylan film. FT-IR, XRD, FE-SEM, AFM and XPS were used to evaluate the effects of xylan on the structure and morphology of chitosan film, and a wide variety of material characteristics of the chitosan/xylan composite films were investigated. The results showed that the xylan chains entered into the gap of chitosan film and became nodules, leading to strong hydrogen bonds and electrostatic interactions between chitosan and xylan. Moreover, the introduction of xylan not only resulted in stronger crystallinity and a more compact structure of chitosan film, but also had an important effect on the properties of chitosan film. The tensile strength, breaking elongation and anti-ultraviolet performance of the chitosan/xylan films were improved greatly with the increasing concentration of xylan; the water vapor transmission rate, water absorption rate and oxygen barrier property of chitosan/xylan composite films were higher than those of chitosan film; chitosan/xylan composite films still showed hydrophobicity when the xylan concentration was more than 1 %. The chitosan/xylan composite film has more potential to be used as food packaging than pure chitosan film.     

Effect of the acrylic acid content on the permeability and water uptake of poly(styrene-co-butyl acrylate) latex films

In this contribution, a theoretical modeling of the latex film formation is presented and compared to experimental results: water vapor permeability and latex film capacitance are studied as a function of acrylic acid content in poly(styrene-co-butyl acrylate) latex films. It has been shown that both water uptake and water vapor permeability are mainly affected by film morphology which in turn is defined by intercolloidal interaction and drying rate.     

Glass transition and film formation of VeoVa/vinyl acetate latices; role of water and co-solvents

The physical forces causing deformation of latex particles during the film formation process have been witley studied. However, the forces resisting particle deformation are still poorly characterized. It is clear that the extent of particle deformation is dependent on the viscoelastic nature of the polymer. In an emulsion, the latex particles will normally contain water, surfactants and “free” monomers which lead to plasticization of the polymer. Although this effect has been recognized, so far it has been studied only on films that had been dried and then partially or completely swollen by water. In this work, plasticization of the emulsion polymers by water and co-solvent has been quantified via differential scanning calorimetry investigation directly on the aqueous latex dispersions. More specifically, the plasticizing effect of water on VeoVa/vinyl acetate copolymer latices and its influence on minimum film-forming temperature (MFFT) has been studied. A linear correlation has been found between T_g and MFFT for the wet latices. This new direct method should help to improve our understanding of the forces resisting latex film formation. Additionally, the homogeneous distribution of the hydrophobic and hydrophilic monomers (VeoVa and vinyl acetate respectively) in the latex particles was verified via a ¹³C-NMR (nuclear magnetic resonance) study performed directly on the latices. This study confirmed that no significant core/shell type of morphology had influenced latex film formation.     

The influence of polymer morphology on polymer film electrochemistry

The electrochemical behavior of functionalized polystyrene-coated electrodes shows a marked dependence on the nature of the electrolyte ions. Scanning electron microscope and surface profile measurements are presented which show that changes in polymer film volume and morphology accompany electrochemical oxidation. Changing polymer morphology by doping the films with soluble monomers during preparation is shown to produce large changes in electrochemical response. Diffusion coefficients were determined for a neutral organic dye dopant in each of the polymer films investigated, and these correlate very well with the oxidation overpotentials observed electrochemically. The nature of polymer film/solvent interactions and the mechanism by which counter ions penetrate the polymer phase is discussed and is related to other physical properties of amorphous polymers in terms of free volume concepts.     

Effect of pore former on the properties of casted film prepared from blends of Eudragit NE 30 D and Eudragit L 30 D-55

The casted films of aqueous dispersions of Eudragit NE30 D and Eudragit L30 D-55 containing pore former were prepared. The study investigated the influence of pore former on basic model drug clarithromycin release, water uptake and water vapor permeability from casted film prepared from the blends of neutral polymer dispersion of Eudragit NE30 D and enteric polymer dispersion of Eudragit L30 D-55. This study was concluded that pore former hydroxypropyl methyl cellulose, lactose, polyethylene glycol (PEG) and polyvinyl pyrrolidon (PVP) was released at the beginning of the release process, the rate and extent of water uptake of the polymeric films were much higher in phosphate buffer pH 6.8 than in pH 5.0 and the concentration of pore former have a significant influence on the permeability to water vapour.     

Latex film morphology and electrical potential pattern dependence on serum components: a scanning probe microscopy study

Dry films formed by surfactant-stabilized, peroxide-initiated styrene-butyl acrylate latex were examined by atomic and electric force microscopy (AFM and EFM). The effects of latex serum components on the films were observed by subjecting the latex to extensive dialysis prior to film formation, and comparing the results to as-prepared latex. The films formed with the dialyzed latex are smoother (as evidenced by roughness and fractal dimension measurements) than the films from the as-prepared latex, but they display large electric force gradients between neighboring domains. The films made with the as-prepared latex have the highest electric uniformity, with a maximum potential variation lower than 80 mV, while this reaches 200 mV in the dialyzed latex film.     

Macroporous Morphology of the Titania Films Prepared by a Sol-Gel Dip-Coating Method from the System Containing Poly(ethylene glycol). IV. General Principle of Morphology Formation and Effect of Heat Treatment

The variation of macroscopic morphology of the titania (TiO₂) films has been studied at various dipping conditions for a sol-gel dip-coating system containing poly(ethylene glycol) (PEG). The variation of macroscopic morphology is understood consistently by considering both the volume fraction of solvent phase during the phase separation and the water to alkoxide ratio in the sol film. The gel film shrinks and the average pore diameter increases concurrently with the thermal decomposition of PEG while the morphology depends less on the crystallization of titania gel.     

Films based on chitosan polyelectrolyte complexes for skin drug delivery: Development and characterization

Novel chitosan based polyelectrolyte complexes (PEC) were developed and optimized in order to obtain films possessing the optimal functional properties (flexibility, resistance, water vapour transmission rate and bioadhesion) to be applied on skin. The development was based on the combination of chitosan and two polyacrylic acid (PAA) polymers with different crosslinkers and crosslinking densities. The interaction between the polymers was maximized controlling the pH, and by forming the films at a pH value close to the pK_a of the respective components as identified by potentiometric and turbidimetric titrations. The action of glycerol, PEG200, Hydrovance and trehalose upon the functional properties of the films was also evaluated. Glycerol was found to improve the film properties in terms of flexibility, resistance and water vapour transmission rate (WVTR) with a maximum effect at 30%. The application of a pressure sensitive adhesive (PSA) significantly improved bioadhesion with a negligible influence in the resistance and flexibility of the films.The optimized film, including adhesive, has shown very good properties for application in the skin and represents a very promising formulation for further incorporation of drugs for topical and transdermal administration.     

Preparation of chitosan–polyethylene glycol coated cotton membranes for wound dressings: preparation and characterization

Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze‐drying. The influence of PEG on the physical characteristics and the surface morphology was investigated. The scanning electron microscopy of the coated fabric revealed a porous structure. The porosity of the material was 54–70% and the pore size was in the range of 75–120µm. The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. The Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed that the CS and PEG have limited interaction. DSC suggested that addition of PEG to CS does not interfere with the crystallization behavior due to limited interaction with CS. The thermogravimetric analysis (TGA) showed that the membranes are thermally stable and PEG enhances the thermal stability of the CS coated membranes. The air and water permeability of the membranes tended to decrease with the increase in the PEG content. Copyright © 2008 John Wiley & Sons, Ltd.     

Film formation from monodisperse acrylic lattices 2. Influence of drying temperature on the film formation process

The influence of drying temperature on the properties of latex films was investigated by gravimetry, turbidimetry (i.e., analysis of transmission spectra and interference), atomic force microscopy and measurement of water vapor permeability. Several pitfalls in the determination of water content of dried films that absorb water after being submerged in it have been proposed, such as fading boundaries, remaining water after drying and change of particle sizes. At moderately higher temperatures film formation is improved. This improvement follows from the formation of smoother film surfaces (AFM), lower water vapor permeabilities and smaller values for delta lambda(min). On the other hand, defects as cracks and channels also are created, especially at high temperatures. It appears, however, that these channels do not run from the one surface of a film to the other.     

A novel polypropylene microporous film

The structure and properties of a polypropylene microporous film prepared by biaxial stretching of non-porous polypropylene film of high β-crystal content were investigated. The porosity of these films can be as high as 30–40%, and the average pore size was around 0.05 μm. The films were found to have the structure of a two-phase interpenetrating network; both the polypropylene and the pore regions were three-dimensionally continuous. The advantages of the biaxially stretched microporous films are the combination of high permeability to fluids with good mechanical properties and almost circular pore shape with narrow pore size distribution. The application of this microporous film for battery separators, filtration membranes and substrates of functional polymer composites is discussed.     

Structure–property relationships of latex films: a special emphasis on viscoelastic behavior and water vapor permeability

The purpose of this work is to investigate the structure and related properties of polymer films obtained upon latex dehydration and coalescence of the particles. Coalesced latex films can be considered as cellular structures, in which the cell cores consist of the hydrophobic particle cores, while the array of interfacial membranes mainly contains hydrophilic species. The linear viscoelastic behavior of the films and their water vapor permeability properties are investigated using dynamic micromechanical analysis and vapor sorption, respectively. It is shown that both core and membrane have a strong effect on the film properties. The structure and viscoelastic behavior of polymer films obtained from sterically stabilized latexes are also studied and compared with that observed for films obtained from electrostatically stabilized ones.     

Controlled deposition of structured polymer films: chemical and rheological factors in chitosan film formation

The technique of "spread coating" has been used to create thin films from solutions of deacetylated and butyl-modified chitosan polymer, and the effect of deposition rate on film thickness has been characterized. Results show that films of controlled thickness can be reproducibly produced and that hydrophobic modification of the polymer can extend the range over which a linear response between film thickness and deposition rate is achieved. Viscometry and fluorescence spectroscopy were also employed to characterize the micellar characteristics of solutions of both deacetylated and butyl-modified chitosan polymer. Although both deacetylated and butyl-modified chitosan solutions were found to have inter- and intramolecular interactions, as well as hydrophobic domains able to incorporate fluorophores, deacetylated chitosan was found to be more interconnected via intermolecular interactions at higher concentrations. These results are important as having the ability to understand how the introduction of hydrophobic modification, a technique shown to introduce solution-based micelle structure and micellar aggregates that support enzyme immobilization, affects film thickness and morphology of spread coated thin films will aid the long-term development and deployment of chitosan-based biofuel cell electrodes.     

The gas barrier coating of 3-aminopropyltriethoxysilane on polypropylene film

Nonporous films were formed on polypropylene (PP) films using 3-aminopropyltriethoxysilane (APTEOS) as the only precursor. The PP film was modified by corona-plasma treatment to provide appropriate adhesion between coating layer and substrate. Gas permeation properties of coating films were evaluated, and the influences of water ratio and film storing time on the gas permeability were investigated. Structural and surface properties of coating layers were characterized by ²⁹Si-NMR, FT-IR, and contact angle analyzer. The APTEOS coating films exhibit much higher barrier properties than PP film. The permeability coefficient of APTEOS coating film with water ratio of 3 is 0.011Barrer for nitrogen, 0.044Barrer for oxygen, and 0.002Barrer for carbon dioxide, while each permeability coefficient of PP bare film is 0.233, 0.858, and 2.886Barrer, respectively. The gas permeability coefficient is increased slowly along with storage time. Although additionally formed siloxane network may lead to a higher inorganic network density, the enhancement of gas permeability during storing period is largely attributed to film-swelling effect by the water vapor from atmosphere.     

Permeation through homopolymer latex films

The helium permeabilities of homopolymer films cast from polymer solutions and latex dispersions have been measured as a function of time. The permeability coefficients of most polymer latex films started off at a value which was considerably higher than that of the corresponding solvent-cast film, but then dropped at a rate dependent on the polymer concerned. The permeability coefficients levelled off at a value which was closer to, but still higher than that of the equivalent solvent-cast film. Solvent-cast film permeabilities remained constant for the period of several months over which time they were examined. The reduction in the permeability of latex films is attributed to ageing processes occurring within the film after casting. The fact that latex film permeability coefficients are always higher than those of solvent-cast films suggests that latex films never become completely homogeneous. The effect on permeability of the latex type and characteristics, and preparation and storage conditions has been examined. The polymer molecular weight, particle size, and surface-change density did not appear to exert any influence, within experimental error. However, the time-dependent permeability behavior was affected by the film preparation and storage temperatures.     

Mechanical properties of films from polymer latices

The mechanical behavior of latex films is governed by their macromolecular nature as well as by their origin from particles dispersed in an aqueous medium. When monomers of different polarity are copolymerized in emulsion copolymerization, a heterogeneous distribution of the polar groups in the latex and the film can occur, owing to the different water solubilities of the comonomers. Films from these latices in many cases show a two-phase morphology, first, consisting of the main polymer within the particles and, second, a phase which is concentrated in the interphase between the original particles and which has a strong influence on the mechanical properties of the films. Films from latices with crosslinked particles behave like homogeneous networks in the linear viscoelastic range, i.e. at small strains. Structured networks are found when latex films are interparticularly crosslinked during or after film formation, e.g. by polar bifunctional monomers or metal salts. Tensile tests of films show that the mechanical strength of latex films develops in the last stage of film formation by interdiffusion and entaglement formation across particle boundaries.     

The effect of composition and draw-down ratio on morphology and oxygen permeability of polypropylene nanocomposite blown films

Polypropylene nanocomposite blown films containing organoclay were prepared by melt extrusion followed by film blowing. The effect of quantity of organically modified montmorillonite, and the compatibilizer (polypropylene-g-maleic anhydride, PP-g-MA), also the draw-down ratio on the morphology and oxygen permeability of nanocomposite films were investigated. Various characterization instruments were employed to identify the morphology, crystallinity, and dynamic mechanical properties of nanocomposite films. The oxygen permeability coefficient was evaluated based on ASTM D1434.X-Ray diffractometry pattern for the most impermeable sample shows that the morphology of nanocomposite film is a coexistence of intercalated tactoids and exfoliated layers which is confirmed by transmission electron microscope micrographs. The results show that the oxygen permeability coefficient is influenced by the quantity of organoclay and compatibilizer, also the morphology and orientation of layered silicate.     

Solubility and diffusivity of water and of salts in an aromatic polyamide film

The solubility and the diffusivity for water and NaCl in a fully aromatic polyamide (PA) film have been determined. From these the “intrinsic permeability characteristics” of this polymer have been calculated and its suitability for desalination by reverse osmosis is compared with that of the commonly used cellulose acetate (CA). It has been found that, although the solubility of NaCl in the PA film is higher than that in a CA film, PA membranes will reject salt better than CA membranes having identical structure and morphology. This is because the diffusivity of NaCl through the PA film is substantially lower, and the permeability of water through it (as well as the solubility and the diffusivity of water in it) are higher than the comparable values for CA films.     

Multilayer film assembled from charged derivatives of chitosan: physical characteristics and biological responses

Polyelectrolyte multilayer films were successfully assembled from each of the three charged derivatives of chitosan; N-[(2-hydroxyl-3-trimethylammonium)propyl]chitosan chloride (HTACC), N-succinyl chitosan (SCC) and N-sulfofurfuryl chitosan (SFC), paired with one of the two oppositely charged polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) on surface-treated poly(ethylene terephthalate) (treated PET) substrates by alternate layer-by-layer adsorption. Surface coverage and wettability of the multilayer films were determined by AFM and water contact angle measurements, respectively. Analysis by quartz crystal balance with dissipation (QCM-D) has suggested that all multilayer films are relatively rigid and have a high water content associated within their structures, accounting for up to 85-90% (w/w) for films having 7-10 layers. In vitro cytocompatibility tests for the fibroblast-like L929 cell line revealed a slight dependency for cell adhesion and proliferation on the outermost layer. The multilayer film containing HTACC exhibited moderate antibacterial activity against E. coli and S. aureus. Bearing negative charges, the multilayer films terminating with SFC and having at least 10 layers were capable of suppressing the adsorption of plasma proteins and platelet adhesion at a comparable level to the multilayer film assembled from heparin, a well-known antithrombogenic polymer.     

Preparation and characterization of collagen/chitosan poly (ethylene glycol)/nanohydroxyapatite composite scaffolds

Porous three‐dimensional collagen/chitosan scaffolds combined with poly (ethylene glycol) (PEG) and hydroxyapatite were obtained through a freeze‐drying method. Physical cross‐linking was examined by dehydrothermal treatment. The prepared materials were characterized by different analyses, eg, scanning electron microscopy (SEM), measurements of porosity and swelling, mechanical properties, and resistance to enzymatic degradation. The porosity of scaffolds and their swelling ratio decreased with the addition of hydroxyapatite. Moreover, after exposure to collagenase, the collagen/chitosan matrices containing PEG showed much faster degradation rate than matrices with the addition of hydroxyapatite. The results indicated that the addition of hydroxyapatite led to improvement of stiffness. The highest degree of porosity and swelling were demonstrated by collagen/chitosan/PEG matrices without hydroxyapatite.