A comparison of different approaches for depth profiling of films and coatings by confocal Raman microscopy

We compare and analyze different approaches to perform depth profiling of polymer films and coatings by confocal Raman microscopy (CRM). Data were generated using three methodologies: conventional metallurgical objectives, oil-immersion optics and numerical post processing of the as-measured intensity profiles, via an optimized deconvolution technique adapted to CRM. A series of bi- and multi-layered polymeric films were used as test systems. Strengths and weaknesses of each methodology are evaluated in terms of delivered depth resolution, signal throughput and flexibility. It is shown that the application of regularized deconvolution on data obtained from dry objectives yielded intensity profiles with a quality comparable, in some cases superior, to those obtained with immersion objectives, with the advantage of being totally non-invasive.     

Plasma deposition of adhesion-promoting polymer layers onto polypropylene for subsequent covering with thick fire retardant coatings

Melamine resins were used as 50-μm-thick fire retardant coatings for polypropylene (PP). Preceding deposition, low-pressure plasma polymer films of allyl alcohol were coated onto PP to improve the adhesion between PP and melamine resin coatings. The efficiency of such fire retardant coatings was confirmed by flame tests. The plasma-deposited polymer and the dip-coated melamine resin films were characterized by Fourier transform infrared-attenuated total reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS). The adhesion of coatings was measured using a 90° peel test with a doubled-faced adhesive tape. To detect the locus of failure, the peeled layer surfaces were inspected using optical microscopy and XPS. Thermal properties of PP thick melamine resin-coated films were analyzed by thermogravimetric analysis.     

Bio‐hybrid nanocomposite coatings from sonicated chitosan and nanoclay

Nanocomposite films and coatings with improved properties were produced from ultrasonic dispersed chitosan and hydrophilic bentonite nanoclay. Bio‐hybrid coatings were applied onto argon–plasma‐activated LDPE coated paper. The intercalation of chitosan in the silicate layers was confirmed by the decrease of diffraction angles as the chitosan/nanoclay ratio increased. Nanocomposite films and multilayer coatings had improved barrier properties against oxygen, water vapor, grease, and UV‐light transmission. Oxygen transmission was significantly reduced under all humidity conditions. In dry conditions, over 99% reduction and at 80% relative humidity almost 75% reduction in oxygen transmission rates was obtained. Hydrophilic chitosan was lacking the capability of preventing water vapor transmission, thus total barrier effect of nanoclay containing films was not more than 15% as compared with pure chitosan. Because to very thin coatings (≤1 μm), nanoclay containing chitosan did not have antimicrobial activity against test strains. All coating raw materials were “generally recognized as safe” (GRAS) and the calculated total migration was in all cases ≤6 mg/dm², thus the coatings met the requirements set by the packaging legislation. Processing of the developed bio‐hybrid nanocomposite coated materials was safe as the amounts of released particles under rubbing conditions were comparable with the particle concentrations in a normal office environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/chitosan blend material: synergistic effects on physical, chemical, thermal and biological properties

A new blend material was fabricated from poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] and chitosan through simple solvent casting method. In this investigation, the impact of different contents of chitosan and molar fractions of 4HB monomer towards the hybrid films was determined. The hydrophobic nature of the P(3HB-co-4HB) copolymer was modified by blending with a hydrophilic polymer—chitosan. Thus, the water-absorption capacity and solubility of the blend films were increased proportionally with the increasing content of chitosan. Miscibility of the blend films between the pure components was detected through Fourier transform infrared analysis. The thermal property was altered in terms of melting temperature, whereas the thermal stability of the blend films was greatly increased. Moreover, the scanning electron microscope images indicated that the surface of the blend films was homogenous and porous. Impregnation of chitosan enabled the blend films to exhibit antimicrobial activity against both Gram-negative and Gram-positive bacteria. The blend films with 20 wt% of chitosan were more hydrophilic, porous, biocidal and they have a wider opportunity in various applications such as wound dressing and tissue engineering than the native P(3HB-co-4HB) copolymer.     

Toward a Green and Sustainable Silver Conservation: Development and Validation of Chitosan-Based Protective Coatings

When exposed to air, silver artifacts undergo an unpleasant darkening and shiny loss, commonly known as tarnishing. At the present, the development of protective coatings by using eco-friendly and biocompatible materials, able to ensure high transparency and to hinder the degradation of silver objects, remains a huge challenge. In this study, chitosan was used for the first time to realize sustainable coatings for silver protection. Both pure and benzotriazole-containing chitosan coatings were prepared and applied on sterling silver disks. A commercial product based on acrylic resin was used as a reference. The aesthetic features and protective properties of these coatings were evaluated by performing two different types of aging treatments. In particular, the assessment of the protective efficacy was carried out by reproducing both highly aggressive polluted environments and real-like museums’ storage conditions. In the first case, chitosan-based coatings with benzotriazole performed better, whereas in storage conditions all the chitosan films showed comparable efficacy. Compositional, morphological and structural analyses were used to evaluate the protective properties of the coatings and to detect any physical or chemical modifications after the aging treatments. Our findings reveal that the two different testing methods provide complementary information. Moreover, chitosan coatings can achieve protective efficacy comparable with that of the commercial product but using non-toxic solvents and a renewable biopolymer. Chitosan coatings, designed for cultural heritage conservation, are thus promising for the protection of common sterling silver objects.     

Chitosan biopolymer as an antimicrobial agent in automotive electrocoatings: The effect of solid content

One of the common additives in water base coating formulation is antibacterial agents. By increasing environmental restrictions about toxic additive and materials, using sustainable materials in coatings formulations is strongly recommended. This research work introduces chitosan biopolymer as a biocompatible antibacterial additive in cathodic electrodeposition bath. The effect of chitosan concentration in electrocoating formulation was studied. Chitosan solutions in different solid content were prepared in lactic acid and were added to formula. The electrodeposition process and final films were investigated by optical microscopy and Pierce film growth model. It was found that chitosan concentration has a significant influence on the chitosan solution structure in bath and final electrodeposited films. The results show that 0.125% v/w concentration has a suitable antibacterial activity and make acceptable electrodeposited film.     

Physicochemical and biological properties of electrodeposited graphene oxide/chitosan films with drug-eluting capacity

In this study, novel graphene oxide/chitosan nanocomposite coatings with long term drug-eluting potential are presented. The coatings are fabricated by the facile and reproducible electrophoretic deposition technique. Analysis of the prepared films shows that the graphene oxide nanosheets are exfoliated in the chitosan matrix. Fourier-transform infrared spectrometry reveals polymer attachment to the carboxylic bonds of graphene oxide, providing a strong interaction and exfoliation of the nanolayers. In vitro viability assay by human osteosarcoma cells (MG-63) demonstrates that the nanocomposite films are highly biocompatible up to 30 wt% graphene oxide, but at higher concentrations a slight cytotoxicity is noticed. Alkaline phosphates enzyme assay also reveals that the presence of graphene oxide nanosheets moderately hampers osteogenesis of the cultured cells. It is shown that vancomycin-loaded nanocomposite coatings gradually release the drug macromolecules for relatively long period of time (up to 4 weeks). The electrodeposited films also exhibit a high bactericidal potential against Gram-positive Staphylococcus aureus. Effects of graphene oxide nanosheets on the physicochemical, biological, antimicrobial and drug-eluting properties of electrodeposited chitosan films are presented and discussed. It is shown that the GO/CS films support the initial attachment, proliferation and growth of osteoblast-like cells.     

Optimization of Multilayer Films Composed of Chitosan and Low-Methoxy Amidated Pectin as Multifunctional Biomaterials for Drug Delivery

Polyelectrolyte multilayers (PEMs) based on polyelectrolyte complex (PEC) structures are recognized as interesting materials for manufacturing functionalized coatings or drug delivery platforms. Difficulties in homogeneous PEC system development generated the idea of chitosan (CS)/low-methoxy amidated pectin (LM PC) multilayer film optimization with regard to the selected variables: the polymer ratio, PC type, and order of polymer mixing. Films were formulated by solvent casting method and then tested to characterize CS/LM PC PECs, using thermal analysis, Fourier transform infrared spectroscopy (FTIR), turbidity, and zeta potential measurements. The internal structure of the films was visualized by using scanning electron microscopy. Analysis of the mechanical and swelling properties enabled us to select the most promising formulations with high uniformity and mechanical strength. Films with confirmed multilayer architecture were indicated as a promising material for the multifunctional systems development for buccal drug delivery. They were also characterized by improved thermal stability as compared to the single polymers and their physical mixtures, most probably as a result of the CS–LM PC interactions. This also might indicate the potential protective effect on the active substances being incorporated in the PEC-based films.     

Barrier properties and abrasion resistance of biopolymer‐based coatings on biodegradable poly(lactic acid) films

Coated polylactic acid (PLA) films consisting of crosslinked‐chitosan/beeswax layer were prepared to improve barrier properties and abrasion resistance of the base substrate. The effect of crosslinking the chitosan layer on durability and barrier properties of the coatings was investigated. Crosslinked samples exhibited lower degree of swelling compared to uncrosslinked samples and 50% reduction in water vapor transmission rate (WVTR) compared to neat PLA films. The beeswax coating decreased the WVTR of chitosan‐coated PLA films significantly (by 100%). However, it had a marginal effect on the oxygen transmission rate. Water vapor transmission was less affected by abrasion than oxygen transmission for both uncrosslinked and crosslinked samples. The WVTR of crosslinked samples were retained even after being subjected to abrasion, whereas WVTR of uncrosslinked samples dropped by 50%. Results obtained using the Taber test method also show that the weight loss of crosslinked coatings are about 75% less than that of uncrosslinked samples and can withstand a greater number of cycles before rupture. These translucent‐coated films retained good barrier and mechanical properties along with providing improved abrasion resistance after crosslinking. This approach provides exciting new possibilities for expanding the use of biodegradable polymers in packaging applications. POLYM. ENG. SCI., 59:1874–1881, 2019. © 2019 Society of Plastics Engineers     

Prediction and characterization of drug release in a multi-drug release system

A new drug delivery system (DDS) was prepared by electrospinning and multi-layered coating methods. Lactobacillus was used as a target drug for release in the large intestine. Lactobacillus was incorporated into polyvinyl alcohol-based electrospun fibers. Alginate and chitosan were then used to coat these fibers to protect and deliver lactobacillus to the large intestine. The multi-layered coating procedure was carried out at various coating times to determine the optimal coating amount in human digestion conditions. The drug-release experiment was conducted using an in vitro model of human digestion processes. Chitosan and alginate were released by dissolving in acid and neutral conditions, respectively. Lactobacillus was then released in a large intestine model by the hydrogel swelling effects of PVA-based electrospun fibers. The drug-release behavior was predicted by calculated equations for optimized coating times. Eventually, the lactobacillus was effectively delivered to the target large intestine by chitosan and alginate coating and was released by PVA hydrogel swelling.     

Thermal Modification and Study of the Structure of Chitosan Films

Using IR spectroscopy, elemental analysis, and potentiometric titration, it was confirmed that amidation and cross linking of the polymer take place in heat treatment of chitosan films in the S-form. It is shown that these processes also take place in hardening of films from formic acid solutions of chitosan by vaporization of the solvent at high temperature.     

Controlled Surface Initiated Polymerization of N-Isopropylacrylamide from Polycaprolactone Substrates for Regulating Cell Attachment and Detachment

Poly(ε-caprolactone) (PCL) substrates were modified with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brushes to direct and control cellular attachment and detachment. Prior to brush growth, the surface of PCL was activated by a diamine to allow for initiator coupling. Infrared spectra taken before and after cell culturing demonstrated the covalently attached nature of the PNIPAM brushes. PCL is a biocompatible polymer and to prove that the modifications described above did not change this characteristic property, a cell attachment/detachment study was carried out. The modified substrates showed a lower cell attachment when compared to PCL alone and to PCL films modified with the initiator. The possibility to detach the cells in the form of a sheet was proved using PNIPAM-modified PCL films by lowering the temperature to 25 °C. No relevant detachment was shown by the unmodified or by the initiator modified surfaces. This confirmed that the detachment was temperature dependent and not connected to other factors such as polymer swelling. These functionalized polymeric films can find applications as smart cell culture systems in regenerative medicine applications.     

Measurement of internal stresses in coatings using time resolved fluorescence

This paper describes a new nondestructive technique for detecting internal stresses in coatings using time resolved fluorescence. The measurement principle is based upon an experimental result that the decay time of fluorescence from poly(3-octylthiophene), P3OT, dispersed in uniaxially-stretched polymer films decreases with increasing tensile stress acting on the films. Internal stresses in the clear coat and in the base coat of a multilayer structure, which was composed of electrodeposited coat, surface coat, base coat, and clear coat, were estimated from the decay time of fluorescence from P3OT in both coats. The order of internal stresses in the clear coat and base coat of the multilayer system was 1 MPa. When the coatings were piled up, the internal stress decreased as the distance from a metal substrate was increased. It was found that moisture and temperature influenced internal stresses in the clear coat rather than in the base coat. Internal stress in the clear coat, which was one layer coated on a metal substrate, was measured by the traditional bimetallic method or by the time resolved fluorescence technique. Comparing both methods, it was concluded that the time resolved fluorescence technique gave reliable values for internal stresses in coatings.     

Investigation of the effect of ZnO nanoparticles on the thermomechanical and microbial properties of hyperbranched polyurethane‐urea hybrid composites

Hybrid coatings of hyperbranched polyurethane‐urea (HBPUU) containing ZnO nanoparticles were prepared by mixing the hyperbranched polyurethane with the nanoparticles. The films were stored at room temperature and laboratory humidity conditions for one week to yield completely cured hybrid films. The ZnO nanoparticles were found to be well dispersed in the polymer up to 3 wt%. The structure–property relationship of various HBPUU–ZnO hybrid coatings was analysed using a Fourier transform infrared peak deconvolution technique with a Gaussian curve‐fitting procedure, while their viscoelastic, thermomechanical and surface morphology were studied using X‐ray diffraction, dynamic mechanical thermal analysis, thermogravimetric analysis, a universal testing machine, scanning electron microscopy, atomic force microscopy and contact angle instruments. The thermal stability and mechanical properties of the hybrid composite films improved with increasing ZnO content, which was believed to be due to thermal insulation in the presence of nanoparticles. Water contact angle data suggested that the hydrophobic character of the hybrid composites increased with increasing nanoparticle concentration. The antimicrobial property of the HBPUU–ZnO hybrid coatings was studied using the disc diffusion method. HBPUU–ZnO hybrid coatings showed good antimicrobial properties compared to HBPUU. Copyright © 2012 Society of Chemical Industry     

Polymer–gold nanoparticle composite films for topical application: Evaluation of physical properties and antibacterial activity

The biocompatible polymer films show potential as an alternative to gels and patches used for topical delivery of therapeutics and cosmetics. The physical strength and antimicrobial activity of polymer films are important attributes for their topical applicability. Here, we have investigated the physical properties and antibacterial activity of six commonly used film forming polymers before and after formation of nanocomposites with gold nanoparticles (AuNP). The blank and AuNP loaded polymer films were prepared by solvent casting method and characterized for thickness, tensile strength, burst strength, skin adhesion strength, degree of swelling, and porosity. The antibacterial activity of the composite films was evaluated by zone‐of‐inhibition and spectrophotometric growth inhibition method against Staphylococcus aureus and Escherichia coli . The physical characterization showed that chitosan films casted using 1.5% w/w resulted in 76 MPa of tensile strength, while zein films required 40% w/w to show 23 MPa of tensile strength. The AuNP (250 μM; 35 nm) loaded polymer films showed significantly (p < 0.05) greater burst strength and skin adhesion strength compared with respective blank films. Among the polymers tested, only blank films of chitosan and zein showed antibacterial activity. On the other hand, all the AuNP loaded polymer films showed significantly (p < 0.05) greater antibacterial activity. The AuNP loaded chitosan film showed E. coli growth inhibition similar to tetracycline. Taken together, chitosan‐ and zein‐AuNP nanocomposite films showed better physical properties and antibacterial activity. POLYM. COMPOS., 38:2829–2840, 2017. © 2015 Society of Plastics Engineers     

Anticorrosive properties of polypyrrole films modified with zinc onto SAE 4140 steel

Polypyrrole (PPy) films modified with zinc were electrosynthesized onto SAE 4140 steel in presence of bis(2-ethylhexyl) sulfosuccinate (AOT). The Zn and PPy electrodeposition was realized by using cyclic voltammetry at different temperatures. The corrosion protection properties of the films were examined in chloride solution by open circuit measurements, linear polarization and electrochemical impedance spectroscopy (EIS). The obtained results indicate that the presence of Zn in the polymer matrix improves the anticorrosive performance of PPy films. The best anticorrosion efficiency was obtained for the coatings modified at 20 °C which provided anodic protection to the steel substrate for a long period of immersion in chloride solution. Cathodic protection was observed when the electrodeposition temperature was increased. Adherence and anticorrosive properties declined sharply for the coatings electrosynthesized at 5 °C.     

Physico-Mechanical and Degradation Properties of Urea-Modified Chitosan Film Photocured with 1-Vinyl-2 Pyrrolidone

Chitosan and urea modified chitosan films were prepared by solution casting. To improve the physico-mechanical properties of the chitosan/urea films, four formulations were prepared using 1-vinyl-2-pyrrolidon (NVP) (varied from 10–80% by weight) in methanol along with photo-initiator. The films were soaked (1–4 minutes) in the prepared formulations and photo-cured under UV-light at different intensities (5–35 pass). The physico-mechanical properties, polymer loading, gel content, water uptake and simulating weathering test of the NVP grafted photocured chitosan/urea film were carried out. Degradation of the chitosan/urea film was also observed. The scanning electron micrographs of the photo-cured chitosan/urea film showed smooth surface, compact and homogeneous structure.     

壳聚糖表面胰蛋白酶分子印迹聚合物的制备及性能的研究

在壳聚糖表面通过希夫碱反应嫁接一层戊二醛,形成核-壳结构微球。然后在这个核-壳微球上,以胰蛋白酶为模板分子,3-氨基苯硼酸为功能单体,制备了胰蛋白酶分子印迹聚合物,通过静态吸附法,研究了聚合物的吸附性能。结果表明,印迹聚合物对模板分子有较高吸附容量和特异选择性。为从蛋白质混和溶液中分离富集胰蛋白酶提供了新的材料和方法。     

Surface tailoring of an ethylene propylene diene elastomeric terpolymer via plasma‐polymerized coating of tetramethyldisiloxane

In the research presented here, we explore the use of a low‐energy plasma to deposit thin silicone polymer films using tetramethyldisiloxane (TMDSO) (H(CH₃)₂? Si? O? Si? (CH₃)₂H) on the surface of an ethylene propylene diene elastomeric terpolymer (EPDM) in order to enhance the surface hydrophobicity, lower the surface energy and improve the degradation/wear characteristics. The processing conditions were varied over a wide range of treatment times and discharge powers to control the physical characteristics, thickness, morphology and chemical structure of the plasma polymer films. Scanning electron microscopy (SEM) shows that pore‐free homogeneous plasma polymer thin films of granular microstructure composed of small grains are formed and that the morphology of the granular structure depends on the plasma processing conditions, such as plasma power and time of deposition. The thicknesses of the coatings were determined using SEM, which confirmed that the thicknesses of the deposited plasma‐polymer films could be precisely controlled by the plasma parameters. The kinetics of plasma‐polymer film deposition were also evaluated. Contact angle measurements of different solvent droplets on the coatings were used to calculate the surface energies of the coatings. These coatings appeared to be hydrophobic and had low surface energies. X‐ray photoelectron spectroscopy (XPS) and photoacoustic Fourier‐transform infrared (PA‐FT‐IR) spectroscopy were used to investigate the detailed chemical structures of the deposited films. The optimum plasma processing conditions to achieve the desired thin plasma polymer coatings are discussed in the light of the chemistry that takes place at the interfaces. Copyright © 2004 Society of Chemical Industry     

Preliminary investigation of the impact of polymer composition on electrochemical properties of coatings as determined by electrochemical impedance spectroscopy

The influence of structural and systematic compositional variations in glycidyl carbamate (GC) functional polymers on the electrochemical properties of their coatings was studied. There are few reports which focus on the correlation of structural and compositional variations in polymer films with their electrochemical barrier properties, diffusion properties with regards to water and aqueous electrolytes, and corrosion performance. To begin to fill this knowledge gap, two sets of GC functional polymers were studied. The polymer compositions were designed to vary the extent of polar hydrophilic groups, non-polar hydrophobic groups, and reactive epoxy groups in the final coatings. Impedance responses of the coatings were found to be closely related to the structural and compositional variations of these GC polymer films. In addition, single frequency EIS experiments were used in an attempt to understand the water uptake behavior of these polymer films using NaCl solution and ionic liquid under immersed condition. The resulting transport property data of the films was correlated to their polymer structure and composition. Moreover, a novel attempt at ranking the stability of coating using capacitance measurement during a cyclic wetting–drying condition was also attempted. The information obtained from this work can potentially be used to optimize the polymer for the specific performance properties needed in the protective coating applications, saving significant time and effort in the research and development stage.