Properties of films prepared from solutions of fibroin-cellulose blends in N-methylmorpholine N-oxide

The physicomechanical properties and thermal stability of films prepared from solutions of fibroin-cellulose blends in N-methylmorpholine N-oxide were studied.     

Surface plasmon resonance sensor for lysozyme based on molecularly imprinted thin films

Molecularly imprinted polymers (MIPs) selective for lysozyme were prepared on SPR sensor chips by radical co-polymerization with acrylic acid and N,N′-methylenebisacrylamide. Gold-coated SPR sensor chips were modified with N,N′-bis(acryloyl)cystamine, on which MIP thin films were covalently conjugated. The presence of NaCl during the polymerization and the re-binding tests affected the selectivity and the optimization of NaCl concentration in the pre-polymerization mixture and the re-binding buffer could enhance the selectivity in the target protein sensing. When the lysozyme-imprinted polymer thin films were prepared in the presence of 40 mM NaCl, the selectivity factor (target protein bound/reference protein bound) of MIP in the re-binding buffer containing 20 mM NaCl was 9.8, meanwhile, that of MIP in the re-binding buffer without NaCl was 1.2. A combination of SPR sensing technology with protein-imprinted thin films is a promising tool for the construction of selective protein sensors.     

Improving mechanical and electrical properties of poly(vinyl alcohol-<Emphasis Type="Italic">g</Emphasis>-acrylic acid) nanocomposite films by reinforcement of thermally reduced graphene oxide

Graphene has drawn an astounding research interest in recent years, owing to its exceptional properties. The scaled-up and trustworthy production of graphene derivatives, such as graphene oxide (GO) and thermally reduced graphene oxide (TRGO), offer wide variety of possibilities to synthesize graphene-based polymer materials for various applications. In the present work, poly(vinyl alcohol-g-acrylic acid) films were prepared by grafting polyacrylic acid chains onto polyvinyl alcohol backbone employing a free radical polymerization system in the presence of crosslinking agent, N,N′-methylenebisacrylamide (MBA). The graphene was homogeneously dispersed into the prepared polymer using thermal mechanical agitation technique. The so prepared nanocomposites were undertaken for structural and morphological characterization using FTIR, SEM, XRD, Raman Spectroscopy, DLS, Zetasizer and AFM analysis, respectively. The electrical conductive and mechanical properties of prepared nanocomposite films were also investigated.     

Self-fixing medicinal films based on copolymers of N-vinylsuccinimide with n-butyl acrylate

The information on properties of films based on copolymers of N-vinylsuccinimide with n-butyl acrylate that are recommended as wound coverings was summarized. Atraumatic, gel-forming, gas-permeable elastic films that self-fix on skin were made from these copolymers by the method of pouring from solutions. As a result, the materials displaying antibacterial (dioxidin, furacylin, lincomycin, rifampicin) and anesthetic (trimecain, pyromecain, anesthesin, novocain) influences were prepared and investigated.     

Structure and infrared emissivity of polyimide/mesoporous silica composite films

Polyimide/mesoporous silica composite films were prepared by direct mixing of polyamic acid solution and silylated mesoporous silica particles, or by condensation polymerization of dianhydride and diamine with silylated mesoporous silica particles in N,N-dimethylacetamide, followed with thermal imidization. Structure and glass transition temperatures of the composite films were measured with FTIR, SEM, EDX, XPS and DMTA. The results show that the silylated mesoporous silica particles in the composites tend to form the aggregation with a strip shape due to phase separation. The composite films exhibit higher glass transition temperature as comparing with that of pure polyimide. It is found that the composite films present lower infrared emissivity value than the pure polyimide and the magnitude of infrared emissivity value is related to the content of silylated mesoporous silica in the composite films. Inhibiting actions of silylated mesoporous silica on infrared emission of the composite films may be owing to presence of nanometer-scale pores in silylated mesoporous silica.     

An effect of N ion bombardment on the properties of CdTe thin films

E-beam evaporated CdTe thin films were processed with N⁺ ion bombardment as in situ process. The N⁺ ion glow was generated using simple Multipurpose Al probe instead of conventional plasma sources. The prepared films were identified as nano crystalline using XRD analysis. High N⁺ ion fluence helped to grow (3 1 1) oriented CdTe thin films instead of (2 2 0) and (1 1 1). The observed results revealed the effect of N⁺ ion fluence on the structural parameters like lattice parameter, d space value, crystalline size, dislocation density, micro strain etc. The observed optical band gap values lie in between 1.47 and 1.77 eV. The effect of N⁺ ion bombardment on optical properties was also reported. Noticeable change in electrical and surface properties was also observed. The observed value shows the reproducibility as <1% and it is suggested that the N⁺ ion plasma was effectively utilized to modify the structural, optical and surface properties as in situ.     

Preparation of the visible light responsive TiO2 thin film photocatalysts by the RF magnetron sputtering deposition method

TiO₂ thin film photocatalysts which could induce photoreactions under visible light irradiation were successfully developed in a single process by applying an ion engineering technique, i.e., the radio frequency (RF) magnetron sputtering deposition method. The TiO₂ thin films prepared at temperatures greater than 773 K showed the efficient absorption of visible light; on the other hand, the TiO₂ thin films prepared at around 573 K were highly transparent. This clearly means that the optical properties of TiO₂ thin films, which absorb not only UV but also visible light, can be controlled by the preparation temperatures of the RF magnetron sputtering deposition method. These visible light responsive TiO₂ thin films were found to exhibit effective photocatalytic reactivity under visible light irradiation (λ > 450 nm) at 275 K for the reductive decomposition of NO into N₂ and N₂O. From various characterizations, the orderly aligned columnar TiO₂ crystals could be observed only for the visible light responsive TiO₂ thin films. This unique structural factor is expected to modify the electronic properties of a TiO₂ semiconductor, enabling the efficient absorption of visible light.     

Electroactivity, electrochemical stability and electrical conductivity of multilayered films containing poly(3,4-ethylendioxythiophene) and poly(N-methylpyrrole)

Multilayered systems of poly(3,4-ethylendioxythiophene) and poly(N-methylpyrrole) have been prepared using a layer-by-layer electrodeposition technique. The electrochemical and electrical properties of films formed by 3, 5, 7 and 9 layers have been characterized and compared with those of pure polymers and copolymers prepared from mixtures of 3,4-ethylendioxythiophene and N-methylpyrrole with various concentration ratios. Results indicate that the electroactivity and electrical stability of the multilayered systems are higher than those of both poly(3,4-ethylendioxythiophene) and copolymers. Furthermore, these electrochemical properties improve when the number of layers increases. On the other hand, the electrical conductivity of the multilayered systems is slightly lower than that of pure poly(3,4-ethylendioxythiophene), and significantly higher than those of poly(N-methylpyrrole) and copolymers.     

Surface-enhanced spectroscopy of Langmuir—Blodgett films of N-octyl,N′-isobutyl-3,4:9,10-perylene-bis(dicarboximide)

The infrared, resonant Raman and surface-enhanced resonant Raman spectra of N-octyl, N′-isobutyl-3,4:9,10-perylene-bis(dicarboximide) (PBDC) were obtained and the aggregation of PBDC molecules was studied using surface-enhanced fluorescence. Langmuir—Blodgett (LB) films of the neat dye as well as mixed layers with arachidic acid, were prepared and transferred to glass slides and surface-enhanced active surfaces for spectroscopic characterization. A strong red shifted excimer emission was characteristic of LB layers of the neat material and of the thin solid films formed by dipping a glass slide into a solution containing the dye and a volatile solvent. However, using mixed LB monolayers of PBDC and arachidic acid, the surface-enhanced fluorescence of the monomer was observed. The surface-enhanced scattering was measured for both neat and mixed LB layers.     

Structure-property relationships for novel wholly aromatic polyamide-hydrazides containing various proportions of para-phenylene and meta-phenylene units: I. Synthesis and characterization

A series of novel wholly aromatic polyamide-hydrazides was synthesized by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl chloride (TCl), isophthaloyl chloride (ICl), or mixtures of various molar ratios of TCl and ICl in anhydrous N,N-dimethylacetamide (DMAc) as a solvent. Polymer structures were identified by elemental analysis and infrared spectroscopy. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. The content of para- and meta-phenylene moieties was varied within this series so that the changes in the latter were 10 mol % from polymer to polymer, starting from an overall content of 0-100 mol %. The prepared polymers were characterized for their properties in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as solubility, intrinsic viscosity, moisture regain, mechanical properties and thermal as well as thermo-oxidative stability. The polymers were readily soluble in several organic polar solvents such as DMAc, N,N-dimethylformamide, dimethyl sulphoxide, N-methyl-2-pyrrolidone and hexamethyl phosphoramide and could be cast into flexible films. Their solubilities were found to increase remarkably with introduction of meta-phenylene moieties into the polymer chains. Their intrinsic viscosities ranged from 0.73 to 4.83 dl g⁻¹ in DMAc at 30 °C and increased with the increase of para-phenylene units content. Mechanical properties of the films produced from these polymers are improved markedly by substitution of para-phenylene units for meta-phenylene units. Thermogravimetric studies revealed that the completely para-oriented type of polymer has better thermal and thermo-oxidative stability relative to that of the other polymers. Moreover, the results reveal that the prepared polymers have a great affinity to water sorption. The hydrophilic character increases as a function of meta-oriented phenylene rings incorporated into the polymer chains.     

Synthesis, characterization and surface properties of amphiphilic polystyrene-b-polypropylene glycol block copolymers

The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 and 2000, having hydrophilic character, were synthesized and polymerized with styrene to prepare PS-b-PPG block copolymers. Cast films and e-spun films were prepared and contact angles of these films with water drop were measured to examine hydrophilic/hydrophobic behavior of the copolymers. Each e-spun film with average fiber diameters from 0.25 to 2.20 μm was prepared in N,N-dimethylformamide (DMF) under controlled electrospinning process parameters such as polymer concentration, applied voltage and tip-to-collector distance. Scanning electron microscope (SEM) images of the electrospun films were taken to determine the fiber diameters. Surface compositions of the block copolymers were also determined by using an electron spectrometer with Mg Kα X-rays. NMR, and FT-IR spectroscopic, and GPC measurements were employed to characterize and determine the PPG contents (6-43%). From the results, electrospinning process increased the hydrophilic properties of the block copolymers obtained, compared their cast film forms. Our results suggest that these polymers are favorable in biological applications in cases where high ratio of the surface to volume and hydrophilicity are required simultaneously. Both chemical structure and topology of the films are important in wetting and hydrophobicity.     

Thermal and fire stability of cotton fabrics coated with hybrid phosphorus-doped silica films

Hybrid phosphorus-doped silica films have been prepared through sol?Cgel processes to enhance the thermal and fire stability of cotton. To this aim, 3-aminopropyltriethoxysilane and N,N,N??,N??,N??,N??-hexakis-methoxymethyl-[1,3,5]triazine-2,4,6-triamine have been reacted with diethylphosphatoethyltriethoxysilane. FT-IR spectroscopy was exploited for assessing the formation of the silica skeleton on the cotton surface and for evaluating the interactions between the cellulosic fibres and the doped film. The effect of the concurrent presence of Si, P and N on cotton has been investigated by thermogravimetric analyses and the flammability behaviour has been assessed by vertical flammability tests, as well. The sol?Cgel treatments in the presence of phosphorus and nitrogen turned out to play a protective role on the degradation of the cotton fibres, hindering the formation of volatile species that fuel the further degradation and favouring the formation of a carbonaceous structure.     

Electrode kinetics of electroactive electropolymerized polymers deposited on graphite electrode surfaces

A kinetic examination of the charge-transport processes (i.e. (i) heterogeneous electron-transfer process of electrode/film interfaces and (ii) homogeneous charge-transport process within films) at electroactive electropolymerized film-coated electrodes was conducted by normal pulse voltammetry. The films employed were of poly(o-phenylenediamine), Poly(N-methylaniline) and poly(N-ethylaniline), which were prepared on electrodes as coating films by electrooxidative polymerization of the corresponding monomers in an acidic solution. It was found that process (i) obeys the conventional Butler-Volmer equation and that process (ii) can be treated as a Fickian diffusion process. In addition, the kinetic parameters characterizing processes (i) and (ii) (i.e. the standard rate constant (k°) and transfer coefficient (α) for process (i), and the apparent diffusion coefficient (D_app for process (ii)) were estimated: D_app = ca (1–4)×10⁻⁸ cm² s⁻¹ s⁻¹, k° = ca. (4–6)×10⁻⁴ cm s⁻¹, α_a (for anodic process) = 0.83–0.86 and α_c (for cathodic process)=0.13–0.23. The are compared with the data reported previously for other electroactive polymer films.     

Optical parameters of thin calixarene films and their response to benzene,toluene and chloroform adsorption

Ellipsometry and surface plasmon-polariton resonance were used to measure both the thickness, d, and refractive index, N, of tert-butylcalix[n]arene (n = 4, 6 and 8) films, as well as the effect of the adsorption of benzene, toluene and chloroform on these parameters. The refractive index values were found to lie in the range 1.56–1.58. Exposure to benzene (chloroform) vapour increased N by 0.01–0.02, while toluene adsorption led to calixarene film swelling (up to 10–12%). Warming the films in air at 160 °C restored the former values of both d and N. Some mechanisms of interaction between the adsorbate molecules and calixarene films are proposed.     

Preparation and Physico-Chemical Characteristics of N-Maleoyl Chitosan Films

N-Maleoyl chitosan (N-MC), a water-soluble derivative of chitosan, was synthesized by N-carboxyacylation of chitosan and maleic anhydride. N-MC films were prepared by solvent casting and kept in a desiccator for different time intervals in order to obtain N-MC films with different degrees of cross-linking. The swelling characteristic of N-MC films was investigated. When the ageing time increased from 5 to 30 d, the swelling of the N-MC films decreased from ∼475 to ∼160% and the weight loss decreased from ∼25 to ∼8%, corresponding to the increase in the cross-linking density from 0.86 × 10⁻⁶ to 8.97 × 10⁻⁶ mol · cm⁻³. Additionally, the swelling behavior of the N-MC films was influenced by changes in either the pH or the ionic strength of the media.     

Chiral helical polyacetylene�Cvinyl polymer core/shell nanoparticles: preparation and application to optically active composite films

Optically active core/shell nanoparticles (NPs) were prepared by combining aqueous catalytic microemulsion polymerization of a monosubstituted N-propargylsulfamide monomer and free-radical polymerization of two vinyl monomers (MMA and BA) in one specific system. In such novel NPs, poly(N-propargylsulfamide) forming the cores took helical conformations of a predominant handedness, endowing the NPs with interesting optical activities. The use of two vinyl monomers simultaneously in one system led to NPs with desirable dispersity and morphology. From the NP emulsions, optically active composite films were prepared with poly(vinyl alcohol) as supporting material, attesting to the potential applications of the optically active core/shell NPs. Following the strategy, other novel core/shell NPs and advanced materials can be anticipated. The current investigations provide large possibilities to realize practical applications of highly interesting helical polyacetylenes.     

Preparation and characterization of new poly(amide–imide) reinforced layer silicate nanocomposite containing N,N′-pyrromellitoyl-bis-l-phenyl acetic acid

Two new samples of poly(amide–imide)/montmorillonite reinforced nanocomposites containing N,N′-pyrromellitoyl-bis-l-phenyl acetic acid moiety in the main chain were synthesized by a convenient solution intercalation technique. Poly(amide–imide) (PAI) 3 as a source of polymer matrix was synthesized by the direct polycondensation reaction of N,N′-pyrromelitoyl-bis-l-phenyl acetic acid 1 with 4,4′-diamino diphenyl ether 2 in the presence of triphenyl phosphite (TPP), CaCl₂, pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PAI-nanocomposite films 4a and 4b with 10% and 20% silicate particles were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposite films were investigated by using UV–vis spectroscopy, thermogravimetric analysis (TGA) and water uptake measurements.     

Photovoltaic properties of lead telluride thin film

Polycrystalline PbTe thin film is prepared on glass substrate at 200 °C. PbTe thin film isN-type and the carriers are electrons. The incident energy of photons, 3.4 eV, generates more electron carriers as the distance decreases which give rise to photoelectric current. The density of donorsN _d was determined to be 1.1×10²⁰ cm^?3 which is consistent with theN-type conduction of PbTe. The activation energies ofN-type PbTe thin films are 0.139, 0.139 and 0.126 eV below 60 °C which change toP-type above 60 °C. This may be due to generation of Pb vacancies in the lattice. The piezoresistivity is measured, the increase of conductivity may be due to displacements of lattice defects under applied stress.     

Copolyamides and copolyesters containing the phenoxasilin ring

Copolyamides and copolyesters containing the phenoxasilin ring were prepared from 2,8-dichloroformyl-10,10-diphenylphenoxasilin, isophthaloyl chloride and m-phenylenediamine or bisphenol A by interfacial polycondensation in chloroform-aqueous alkali mixture. They were obtained in yields of 80% or above and at relatively high viscosities up to 1.30 dl/g. The copolymers with high phenoxasilin content were freely soluble in dimethylacetamide, dimethylformamide and N-methyl-2-pyrrolidone, but decreasing phenoxasilin content led to copolymers with slight solubilities in these solvents; the copolyesters also dissolved in chloroform, m-cresol and phenol-sym tetrachloroethane (60:40 in wt%). Flexible transparent films were obtained from chloroform solutions of the copolyesters, but the films cast from DMF solutions of the copolyamides became brittle as the phenoxasilin content decreased. The phenoxasilin-containing copolymers hardly degraded below 400° and had good thermal stability. Introduction of the phenoxasilin ring into the polymer backbones by copolycondensation did not reduce thermal stability.     

Polyimide-polydimethylsiloxane copolymers containing nitrile groups

A novel series of nitrile-containing polyimide-polydimethylsiloxane copolymers was prepared by polycondensation reaction of 4,4′-oxydiphthalic anhydride with a mixture of an aromatic diamine, namely 2,6-bis(3-aminophenoxy)benzonitrile, and bis(aminopropyl)oligodimethylsiloxane of controlled molecular weight, in different ratios. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidone, N,N-dimethylformamide as well as in less polar solvents such as chloroform, and can be cast from solution into thin flexible films. The inherent viscosity was in the range of 0.43-0.55 dL/g. The polymers showed good thermal stability, the decomposition temperature being above 430 °C. They exhibited a glass transition temperature in the range of 149-219 °C, with reasonable interval between glass transition temperature and decomposition temperature. The surface morphology was investigated by scanning electron microscopy. The water dynamic contact angles were measured by tensiometric method. The free surface energy was evaluated based on Owens and Wendt equation. A composite film based on a polyimide-polydimethylsiloxane copolymer and pyrite ash powder has been prepared and its nanoactuation has been investigated.