Recombination luminescence of poly(arylene phthalide) films: 1. Electronic and optical features of poly(arylene phthalide)s

Features of the luminescence and absorption spectra of poly(biphenylene phthalide), poly(fluorenylene phthalide), and poly(terphenylene phthalide) films were analyzed. Experimental results obtained for these films by optical methods and thermally stimulated current spectroscopy were compared. Long-lasting afterglow emission from the films after photoexcitation was observed. Possible explanations for the observed optical and thermally stimulated processes in the poly(arylene phthalide)s were suggested in terms of reversible electronic phase transitions induced by external factors in unconjugated polymers.     

Sorption of Water Vapor by Keratin

The word “keratin” is usually applied to that group of fibrous proteins characterized by the presence of the amino acid cystine which enables the formation of disulfide bridges between neighboring polypeptide chains. In nature, the hardened form of keratin plays a protective role and appears in many forms of animal outer covering, such as wool, hair, nails, horn, feather, and quill, where a high degree of physical strength and chemical resistance are desirable. This variety provides a wide selection of geometrical forms and subtle differences in composition between keratins, which can be employed in the study of sorption mechanisms for this material. All forms of keratin contain hydrophilic amino acid residues and peptide groups which ensure significant adsorption of water vapor. Keratin differs from the soluble proteins because the presence of cross-links renders it insoluble in water; it is only soluble in reagents capable of rupturing the disulfide bridges. However, in common with other biopolymers and synthetic polymers having an affinity for water, keratin swells on adsorption over the entire humidity range.     

Thermal chemiluminescence of fibrous proteins

Thermal chemiluminescence (TCL) from the fibrous proteins wool and feather keratin, silk fibroin and Type I collagen is reported for the first time. The proteins all emit TCL when heated in the atmosphere of O₂ or N₂ in the range 40-220 °C. Plotting non-isothermal CL data in O₂ in Arrhenius format showed an increase in the activation energy at temperatures in the range 129-161 °C for each protein. This may indicate that a different free radical oxidation process operates when the mobility of the amorphous phase of the protein is increased above its T_g. Wool, silk and collagen exhibited a luminescence peak at 130 °C (with feather keratin at 145 °C) during non-isothermal CL experiments in N₂, similar to that observed in many synthetic polymers and characteristic of polymer hydroperoxides.     

Black and white – does melanin change the bulk carbon and nitrogen isotope values of feathers?

Bird feathers are employed in a wide range of carbon and nitrogen isotope studies relating to diet and migration. Feathers are chemically inert with respect to carbon and nitrogen, after synthesis. It has always been assumed that feathers show isotope values characteristic of keratin, a fibrous structural protein from which they are formed. Little attention has been paid to other components of feathers such as melanin or carotenoids. Melanin is synthesized from tyrosine, which is depleted in both ¹³C and ¹⁵N. We compared isotope values of coeval black and white feathers in four different species. Black feather parts were in all cases significantly depleted in ¹³C relative to white feather parts but in most species no clear trend was discernable for ¹⁵N. We suggest that additional evaluation may be required to characterize the carbon and nitrogen isotope contribution of feather pigments like carotenoids. Care should be taken in future stable isotope studies when comparing differently coloured feathers. Copyright © 2010 John Wiley & Sons, Ltd.     

Isolation,identification, and keratinolytic activity of several feather-degrading bacterial isolates

Several feather-degrading bacterial isolates were isolated from Egyptian soil. These isolates were able to degrade chicken feather, when grown on basal medium containing 1% native feather as a source of energy, carbon, and nitrogen. Feather waste, generated in large quantities as a byproduct of commercial poultry processing, is nearly pure keratin, which is not easily degradable by common proteolytic enzymes. The isolates were identified according to the morphological characteristics, biochemical tests, and API 50 CHBBacillus system. Proteolytic and keratinolytic activities of these isolates were monitored throughout the cultivation of the bacterial isolates on feather. Resulting soluble proteins, which were released as a result of the biodegradation of feather, were demonstrated by SDS-PAGE.     

Preparation of Feather Keratin Hydrolyzate‐Gelatin Composites and Their Graft Copolymers

With the aim of utilizing the Keratinous waste material, poultry feather, which is up till now discarded as a waste, was hydrolyzed to form keratin hydrolyzate (FH). As FH does not form a film, it was mixed with gelatin (G) and FH‐G composite was prepared in film form. FH‐G was further graft co‐polymerized with 2‐hydroxyethyl methacrylate (HEMA) to achieve better physico‐chemical properties for the resultant hydrogels. Percentage grafting studies and IR studies confirmed the grafting of PHEMA onto FH‐G. FH‐G‐PHEMA exhibited better mechanical properties compared to FH‐G and FH‐PHEMA. TG studies clearly indicated the grafting of HEMA onto FH and FH‐G. SEM (Scanning Electron Microscopy) pictures of FH‐G and FH‐PHEMA films exhibited brittle nature on their surface, whereas continuity and A smooth surface was observed on for the FH‐G‐PHEMA films.     

Isolation and characterization of a novel feather-degrading bacterial strain

Feather waste, generated in large quantities as a byproduct of commercial poultry processing, is almost pure keratin, which is not easily degradable by common proteolytic enzymes. Feather-degrading bacteria were isolated from a Brazilian poultry industrial waste. Among these isolates, a strain identified as kr2 was the best feather-degrading organism when grown on basal medium containing 10 g/L of native feather as a source of energy, carbon, and nitrogen. The isolate was characterized according to morphological characteristics and biochemical tests belonging to the Vibrionaceae family. Keratinolytic activity of this isolate was monitored throughout the cultivation of the bacterium on raw feather at different temperatures. The optimum temperature for growth was about 30°C, at which maximum enzyme and soluble protein production were achieved. The enzyme had a pH and temperature optima of 8.0 and 55°C, respectively.     

Chemical origin of thermally stimulated discharge currents in polyacrylonitrile

Thermally stimulated discharge has been used in the past to diagnose and estimate the magnitude of electrical polarization in polymers. Nevertheless, molecular characterization of operative phenomena by this technique alone is often a difficult task. In the present work, infrared attenuated total reflection spectroscopy has been used to investigate the origin of thermally stimulated discharge currents near 200°C in externally unpolarized films of polyacrylonitrile (PAN). Spectroscopic analysis of thermally degraded films reveals some unsaturation of the PAN backbone and possibly the generation of cyanide ions. Opposite surfaces in a solvent-cast film give different spectra, indicating a gradient in chemical degradation products across the film thickness. Data suggest that nonuniform generation of charged species and unsaturated bonds gives rise to internal potentials in PAN. The origin of thermally stimulated currents in PAN near 200°C is thus believed to be associated with the onset of chemical degradation.     

Triptycene polymers

New, bifunctional, bridgehead-substituted triptycenes were synthesized and used to prepare a series of triptycene polymers, including polyesters, polyamides, polyurethanes, and a polyoxadiazole. Certain of these partially aliphatic polymers were thermally stable. Clear and colorless films were obtained in some instances.     

Siloxane/silane‐crosslinked systems from supercritical carbon dioxide: II. Pendant phenyl poly(carbosilane/siloxane)s

New silicone‐containing polymers with crosslinkable units have been synthesized by hydrosilation polymerization in both toluene and supercritical carbon dioxide (70°C, 3000 psi) catalyzed by platinum‐divinyltetramethyldisiloxane (Pt‐DVTMS). It was found that high molecular polymers were obtained in both toluene and supercritical carbon dioxide. The polymers were characterized by FTIR, NMR, GPC, TGA, and DSC. The molecular weights of these polymers ranged from 9000 to 39,000. With further hydrolysis and thermal curing, the molecular weight can be increased significantly. Comparison of the properties between reactions in toluene versus supercritical carbon dioxide indicated that the green solvent is a usable alternative for hydrosilation polymerization. The new polymers synthesized in either toluene or supercritical carbon dioxide are thermally stable, ranged from 350 to 488°C. Copyright © 2008 John Wiley & Sons, Ltd.     

Biological Pretreatment of Chicken Feather and Biogas Production from Total Broth

Chicken feathers are available in large quantities around the world causing environmental challenges. The feathers are composed of keratin that is a recalcitrant protein and is hard to degrade. In this work, chicken feathers were aerobically pretreated for 2–8 days at total solid concentrations of 5, 10, and 20 % by Bacillus sp. C₄, a bacterium that produces both α- and β-keratinases. Then, the liquid fraction (feather hydrolysate) as well as the total broth (liquid and solid fraction of pretreated feathers) was used as substrates for biogas production using anaerobic sludge or bacteria granules as inoculum. The biological pretreatment of feather waste was productive; about 75 % of feather was converted to soluble crude protein after 8 days of degradation at initial feather concentration of 5 %. Bacteria granules performed better during anaerobic digestion of untreated feathers, resulting in approximately two times more methane yield (i.e., 199 mlCH₄/gVS compared to 105 mlCH₄/gVS when sludge was used). Pretreatment improved methane yield by 292 and 105 % when sludge and granules were used on the hydrolysate. Bacteria granules worked effectively on the total broth, yielded 445 mlCH₄/gVS methane, which is 124 % more than that obtained with the same type of inoculum from untreated feather.     

Labile hyperbranched polymers used as nanopore-forming agents in polymeric dielectrica

Hyperbranched polyesters containing labile triazene units in the main chain have been synthesized and characterized. These structure decompose photochemically upon UV irradiation and thermally above 160°C. Homogeneous incorporation of these globular, functional polymers in thermostabile polymer matrices (polyimides and BCB polymers) was possible. Smooth films from blends of thermolabile matrix and up to 50% hyperbranched polymers could be prepared and have been studied as insulating material in microelectronic multilayer applications.     

Polybenzimidazoles,new thermally stable polymeres

Wholly aromatic polybenzimidazoles were synthesized from aromatic tetraamines and difunctional aromatic acids and characterized as new thermally stable polymers. The melt polycondensation of aromatic tetraamines and the diphenyl esters of aromatic dicarboxylic acids was developed as a general procedure of wide applicability. Polybenzimidazoles containing mixed aromatic units in the chain backbone were prepared from 3,3′-diaminobenzidine, 1,2,4,5-tetraaminobenzene and a variety of aromatic diphenyl dicarboxylates. Phenyl 3,4-diaminobenzoate could also be polymerized by melt condensation to give poly-2,5(6)-benzimidazole. The polymers were characterized by a high degree of stability, showing great resistance to treatment with hydrolytic media and an ability to withstand continued exposure to elevated temperatures. Most of the polymers were infusible, but some had melting points above about 400°C. Many of the polymers exhibited no change in properties on being heated to 550°C, and showed a weight loss of less than 5% when heated under nitrogen for several hours to 600°C. The polymers were soluble in concentrated sulfuric acid and formic acid, producing stable solutions. Many of the polymers were soluble in dimethyl sulfoxide and some also in dimethylformamide. The inherent viscosities of a number of polymers in 0.5% dimethyl sulfoxide solution ranged from approximately 0.4 to 1.1. The higher polymers could be cast into stiff and tough films from formic acid and dimethyl sulfoxide solutions.     

Oxidation and biodegradation of polyethylene films containing pro-oxidant additives: Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation

Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation on the oxidation and biodegradation of linear low density poly(ethylene) PE-LLD films containing pro-oxidant were examined. To achieve oxidation and degradation, films were first exposed to the sunlight for 93 days during the summer months followed by their incubation with fungal strains previously isolated from the soil based on the ability to grow on the oxidized PE-LLD as a sole carbon source. Some films were also thermally aged at temperatures ranging between 45°C and 65 °C, either before or after fungal degradation. Films with pro-oxidant additives exhibited a higher level of oxidation as revealed by increase in their carbonyl index (COi). In addition to increase in the COi, films showed a slight increase in crystallinity and melting temperature (T_m), considerably lower onset degradation temperatures, and a concomitant increase in the % weight of the residues. The level of oxidation observed in thermally aged films was directly proportional to the aging temperature. The PE-LLD films with pro-oxidant exposed to sunlight followed by thermal aging showed even higher rate and extent of oxidation when subsequently subjected to fungal biodegradation. The higher oxidation rate also correlated well with the CO₂ production in the fungal biodegradation tests. Similar films oxidized and aged but not exposed to fungal biodegradation showed much less degradation. Microscopic examination showed a profuse growth and colonization of fungal mycelia on the oxidized films by one strain, while another spore-producing strain grew around the film edges. Data presented here suggest that abiotic oxidation of polymer's carbon backbone produced metabolites which supported metabolic activities in fungal cells leading to further biotically-mediated polymer degradation. Thus, a combined impact of abiotic and biotic factors promoted the oxidation/biodegradation of PE-LLD films containing pro-oxidants.     

Photo-induced chemiluminescence from fibrous polymers and proteins

A commercial thermal chemiluminescence (TCL) instrument was modified to allow in situ sample irradiation at wavelengths in the range 320-700 nm under a controlled atmosphere at constant temperature. Weak photo-induced chemiluminescence (PICL) emission was observed from commercial poly(ethylene terephthalate), polyacrylonitrile, and polyamide 6 fabrics, cotton fabric and from the fibrous proteins wool and feather keratin, silk fibroin and bovine skin collagen (Type 1) after exposure to UVA (320-400 nm) or visible light in nitrogen, followed by a change of the atmosphere to oxygen. Collagen emits PICL of similar intensity to keratin, which demonstrates that tryptophan is not essential for PICL emission from proteins. In all cases the decay of PICL with time is complex and does not follow simple first- or second-order kinetics. The effects of experimental variables, including wavelength of radiation and exposure time, sample temperature and fabric pH on the PICL intensity and decay profile are reported for wool keratin.     

Synthesis and characterization of new,soluble polyazomethines bearing fluorene and carbazole units in the backbone and solubility‐improving moieties in the side group

A series of novel, soluble polyazomethines bearing fluorene and carbazole moieties in the main chain and solubility‐improving moieties in the side group (dibutyl, ethylhexyl, thienylethyloxy, furyl, and fluorenyl) were synthesized. Good‐quality films of these polymers were prepared through the conventional solution‐casting and drying processes. Depending on the polymer structure, some polymers showed a glass‐transition temperature (107–167 °C) and others showed a melting temperature (285–341 °C). The temperature of 5% weight loss under nitrogen atmosphere of the polymers ranged from 370 to 464 °C. The results indicated that the side groups incorporated into the polyazomethine structure in this work improved the polymer solubility without sacrificing thermal stability. Depending on the polymer structure, some of the polymers were crystalline whereas others were amorphous. All the polyazomethines were solution‐processable and thermally stable, making them potential candidate materials for applications in microelectronics and aerospace. Moreover, the features in the UV–visible spectra of the polyazomethines were redshifted as compared with those of the monomers from which the polymers were synthesized, indicating that these polymers, if combined with an appropriate doping agent to improve the light‐emitting and conducting abilities, may be good candidate materials for optoelectronic devices. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 825–834, 2004     

Efficient direct electron transfer with enzyme on a nanostructured carbon film fabricated with a maskless top-down UV/ozone process

We have developed a new carbon film electrode material with thornlike surface nanostructures to realize efficient direct electron transfer (DET) with enzymes, which is very important for various enzyme biosensors and for anodes or cathodes used in biofuel cells. The nanostructures were fabricated using UV/ozone treatment without a mask, and the obtained nanostructures were typically 2-3.5 nm high as confirmed by atomic force microscopy measurements. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that these nanostructures could be formed by employing significantly different etching rates depending on nanometer-order differences in the local sp(3) content of the nanocarbon film, which we fabricated with the electron cyclotron resonance sputtering method. These structures could not be realized using other carbon films such as boron-doped diamond, glassy carbon, pyrolyzed polymers based on spin-coated polyimide or vacuum-deposited phthalocyanine films, or diamond-like carbon films because those carbon films have relatively homogeneous structures or micrometer-order crystalline structures. With physically adsorbed bilirubin oxidase on the nanostructured carbon surface, the DET catalytic current amplification was 30 times greater than that obtained with the original carbon film with a flat surface. This efficient DET of an enzyme could not be achieved by changing the hydrophilicity of the flat carbon surface, suggesting that DET was accelerated by the formation of nanostructures with a hydrophilic surface. Efficient DET was also observed using cytochrome c.     

Thermal and structural characterization of poly(ethylene-oxide)/keratin blend films

Blends of poly(ethylene oxide) (PEO) and keratin were prepared with the aim of obtaining bio-compatible materials suitable for film and fibre production. Aqueous keratin solutions, prepared by keratin extraction from wool with urea, m-bisulphite and sodium dodecyl sulphates (SDS), filtration and dialysis, were added with different amounts of PEO and solid films were prepared by casting. The addition of SDS prevents protein aggregation. Morphological, thermal and spectroscopic analysis of the films pointed out that keratin hinders the PEO crystallization process, since a progressive decrease in the size of PEO spherulites is observed and the melting point and the related enthalpy decrease with increasing the keratin content. On the other hand, according to thermal and spectroscopic investigations. PEO seems to interfere with the keratin self-assembling giving the protein a different thermal behaviour.     

Liquid-crystalline polymer composites with CdS nanorods: structure and optical properties

We report on the structure, uniaxial orientation, and photoluminescent properties of CdS nanorods that form stable nanocomposites with smectic C hydrogen-bonded polymers from the family of poly(4-(n-acryloyloxyalkoxy)benzoic acids. TEM analysis of microtomed films of nanocomposites reveals that CdS nanorods form small domains that are homogeneously distributed in the LC polymer matrix. They undergo long-range orientation with the formation of one-dimensional aggregates of rods when the composite films are uniaxially deformed. The Stokes photoluminescence was observed from CdS NRs/LC polymer composites with emission peak located almost at the same wavelength as that of NRs solution in heptane. An anti-Stokes photoluminescence (ASPL) in polymer nanocomposites was found under the excitation below the nanoparticles ground state. The mechanism of ASPL was interpreted in terms of thermally populated states that are involved in the excitation process. These nanocomposites represent an unusual material in which the optical properties of anisotropic semiconductor nanostructures can be controlled by mechanical deformation of liquid-crystalline matrix.     

Preparation and biodegradation of electrospun PLLA/keratin nonwoven fibrous membrane

As a kind of natural protein, wool keratin was used to improve the cell affinity of poly(l-lactic acid) (PLLA). After small keratin particles were prepared from keratin solution by spray-drying process, they were blended with PLLA solution. PLLA/keratin nonwoven fibrous membrane was produced by electrospinning the blend solutions. The release rate of keratin from the composite membrane was detected by Fourier transform infrared (FTIR) after PLLA/keratin membranes were degraded in PBS up to 4 weeks. The chemical compositions of the PLLA/keratin surface were examined by X-ray photoelectron spectroscope. Although more than half of the keratin was removed from PLLA/keratin membrane during the first few hours of degradation, some keratin particles were still embedded in the PLLA fibers. Osteoblast cells were used to evaluate the cellular behaviors of the composite membrane. After 7 days culturing, more cells were observed on PLLA/keratin membranes than on pure PLLA membranes. MTT assay and alkaline phosphatase (ALP) activity results suggested that keratin could improve the interactions between osteoblast cells and the polymeric membranes.