Depolymerization Products Research Articles

Oligomeric benzoin photoinitiators

AbstractNovel oligomeric photoinitiators were synthesised by reacting benzoin with isophorone diisocyanate‐terminated oligomers of dihydroxy‐terminated depolymerization products of polyethylene terephthalate (PET). PET was depolymerized by ethylene glycol (EG), hexylene glycol (HG), polyethylene glycol 10 000 (PEG), and α, ω‐dihydroxy poly(dimethyl siloxane)s (PDMS). Oligomeric photoinitiators were used as free radical initiators for polymerization of styrene and acrylonitrile. Formation of block copolymers was illustrated by several characterisation methods such as FTIR, 1H‐NMR, DSC, and GPC. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 500–508, 2002

Determination of the degree of polymerisation of carboxymethyl cellulose by size exclusion chromatography

A size exclusion chromatographic (SEC) system was developed in order to investigate the molecular weight distribution of depolymerisation products obtained by enzymatic degradation of carboxymethyl cellulose (CMC). The SEC system, which relies on a Superose 12 HR 10/30 column and an eluent containing sodium hydroxide (0.05 M), enabled an effective separation of CMC fragments. Cellulase was used for the degradation of CMC. Degradation was followed as a function of incubation time and cellulase dosage by viscosity measurements. The CMC hydrolysates separated by SEC were detected as total organic carbon (TOC) and reducing sugars. The degree of polymerisation (DP) of the hydrolysates was then determined by dividing the number of anhydroglucose units by the reducing sugar concentrations. The DP of the CMC fragments obtained after enzymatic hydrolysis ranged from 100 to 1, compared with a DP v of 170 for untreated CMC samples. The results obtained for a series of CMC fragments agreed with the DP values of standards of known molecular weight. The method is an absolute method; no external calibration was needed to calibrate the Superose 12 HR 10/30 column.

Degradation of lignin and lignin model compound under sulfate reducing condition

The release of depolymerization products of lignin during the degradation of lignocellulsic material under sulfate reducing condition was investigated. In addition, we investigated the fate of the most common (beta-O-4) link present in lignin under sulfate reducing condition, using a lignin model compound. The method of investigation was based on the selective inhibition of microbial uptake of released aromatic phenolic compounds, depolymerization product of lignin, by toluene. Eight different aromatic phenolic compounds were identified. Until day 17 only 3 phenolic compounds were regularly detected, thereafter 7 aromatic phenolic compounds could be regularly identified. The accumulation of identified phenolic acid was not linear with time. The lignin model compound was completely degraded within 13 days when either Avicel cellulose or newspaper was present as alternate source of carbon. On the other hand when lignin model compound was present as the sole source of carbon, it took more than 22 days for its complete degradation. But in either case complete degradation of lignin model compound was observed. Four degradation byproducts of lignin model compound were identified, but the two most significant compounds identified were vanillic acid and 3-methoxy-4-hydroxy benzene propionic acid. The GC/MS analysis of the degradation by products of lignin model compound indicated that beta-O-4 link was cleaved under sulfate reducing condition and the presence of additional carbon source enhanced this process.

Analysis of alkali-lignin in a paper mill effluent decolourised with two Streptomyces strains by gas chromatography–mass spectrometry after cupric oxide degradation

Alkali-lignin samples obtained from an untreated paper mill effluent and from the effluent decolourised by the strains Streptomyces avermitilis CECT 3339 and Streptomyces scabies UAH 51 were analysed by gas chromatography–mass spectrometry (GC–MS) after cupric oxide degradation. The analysis of the depolymerisation products of the alkali-lignin from the decolourised effluents showed a strain specific modification of the aromatic moiety of the alkali-lignin. Moreover, both strains were able to breakdown the aryl–alkyl ether linkages between the cinnamic acids and the lignin. Finally, GC–MS analysis showed that both strains oxidised the alkali-lignin regardless of its initial degree of oxidation.

The 4 Å X-Ray Structure of a Tubulin:Stathmin-like Domain Complex

Phosphoproteins of the stathmin family interact with the αβ tubulin heterodimer (tubulin) and hence interfere with microtubule dynamics. The structure of the complex of GDP-tubulin with the stathmin-like domain of the neural protein RB3 reveals a head-to-tail assembly of two tubulins with a 91-residue RB3 α helix in which each copy of an internal duplicated sequence interacts with a different tubulin. As a result of the relative orientations adopted by tubulins and by their α and β subunits, the tubulin:RB3 complex forms a curved structure. The RB3 helix thus most likely prevents incorporation of tubulin into microtubules by holding it in an assembly with a curvature very similar to that of the depolymerization products of microtubules.

Photobleaching studies on azabenzoporphyrins and related systems: a comparison of the photobleaching of the zinc(II) complexes of the tetrabenzoporphyrin, 5-azadibenzo[b,g]porphyrin and phthalocyanine systems

The kinetics of photobleaching of zinc(II) tetra-t-butyltetrabenzoporphyrin 1, zinc(II) 13,17-diethyl-12,18-dimethyl-5-azadibenzo[b,g]porphyrin 2 and zinc(II) tetra-t-butylphthalocyanine 3 are studied. In methanol containing ca 0.1% pyridine, complex 1 undergoes photoaggregation, 2 is relatively photostable, while 3 undergoes a smooth true photobleaching process with loss of intensity across the visible region. Where appropriate, apparent first-order rate constants for the photodiminution of the α band in the spectra are reported, and the effects of solvent variation and of additives are measured. It has not been possible to provide an overall rationalization of the solvent effects, but the effects of additives support the view that the photo-oxidative processes involve singlet oxygen. Experiments with potassium superoxide do not support superoxide involvement. Preparative experiments in methanol have been carried out with 1 and 3. 1 leads to a large recovery of the starting material, indicating that the photoaggregation does not involve the formation of new covalent bonds. 3 gives rise to at least five products (besides the starting material). Two of these, isolated in low yields (<5%), are identified as a fragmentation (depolymerization) product, 4-t-butylphthalonitrile, and the expected oxidative product, 4-t-butylphthalimide. The results are discussed and conclusions drawn.

Block copolymers of styrene containing oligomeric esters of terephthalic acids

A new generation of block copolymers were synthesized starting with depolymerized PET by glycolysis with some oligomeric diols. α,ω-Dihydroxy poly(dimethyl siloxane)s, hexylene glycol, poly(ethylene oxide)glycols, and ethylene glycol were used as diols. The dihydroxy-terminated depolymerization products containing a terephthalyl group and oligomeric diols were used to prepare a diradicalic macroinitiator (MI). These MIs were used to polymerize the styrene monomer. The new block copolymers obtained were characterized by physical and chemical methods and mechanical and thermal analyses.

Low molecular mass products of depolymerization of purified mucin--attempts at isolation and characterization.

Samples of crude mucin were incubated at room temperature for 48 and 96 h in a sodium azide containing buffer, pH 7.0. Then each sample was purified, reduced and alkylated with iodo[14C]acetamide. Electrophoretic analysis demonstrated that radioactivity was incorporated into the mucin subunits and proteins of 100 and 140 kDa. The results of our experiments suggest that the released proteins can be a part of mucin molecule, cleaved by proteolysis and reduction of disulfide bridges.

Ozonolytic depolymerization of polysaccharides in aqueous solution

The selective oxidation of β- d-glycosidic linkages of polysaccharides by ozone has great utility as a general method for depolymerization of polysaccharides. Here we describe a ‘one-step’ method whereby polysaccharides dissolved in water or basic solutions are depolymerized by ozonolysis. The oxidation of glycosidic linkages of unprotected carbohydrates by ozone is complicated by several side reactions. We describe here optimized conditions for carrying out ozonolysis degradation. We also characterize the major pathways for unwanted degradation by various side reactions. In the preferred oxidation pathway, the aldosidic linkage is oxidized to an aldonic ester function that hydrolyzes under the basic conditions employed to give a free aldonate, with cleavage of the polysaccharide chain. Nonselective degradation pathways include oxidative degradation by radical species that oxidize glycosyl residues to formic, acetic, and oxalic acids. The nonselective degradation caused by acids is minimized by basic buffers. The products of polysaccharide depolymerization form a size distribution around a nominal molecular weight, and the average molecular weight of the products can be controlled by the rate or amount of ozone passed through the reaction mixture. The ozonolysis method described herein provides a convenient, inexpensive, and controllable means for generating small polysaccharides or large oligosaccharide fragments.

Microbial system for polysaccharide depolymerization: enzymatic route for xanthan depolymerization by Bacillus sp. strain GL1.

An enzymatic route for the depolymerization of a heteropolysaccharide (xanthan) in Bacillus sp. strain GL1, which was closely related to Brevibacillus thermoruber, was determined by analyzing the structures of xanthan depolymerization products. The bacterium produces extracellular xanthan lyase catalyzing the cleavage of the glycosidic bond between pyruvylated mannosyl and glucuronyl residues in xanthan side chains (W. Hashimoto et al., Appl. Environ. Microbiol. 64:3765-3768, 1998). The modified xanthan after the lyase reaction was then depolymerized by extracellular beta-D-glucanase to a tetrasaccharide, without the terminal mannosyl residue of the side chain in a pentasaccharide, a repeating unit of xanthan. The tetrasaccharide was taken into cells and converted to a trisaccharide (unsaturated glucuronyl-acetylated mannosyl-glucose) by beta-D-glucosidase. The trisaccharide was then converted to the unsaturated glucuronic acid and a disaccharide (mannosyl-glucose) by unsaturated glucuronyl hydrolase. Finally, the disaccharide was hydrolyzed to mannose and glucose by alpha-D-mannosidase. This is the first complete report on xanthan depolymerization by bacteria. Novel beta-D-glucanase, one of the five enzymes involved in the depolymerization route, was purified from the culture fluid. This enzyme was a homodimer with a subunit molecular mass of 173 kDa and was most active at pH 6.0 and 45 degrees C. The enzyme specifically acted on xanthan after treatment with xanthan lyase and released the tetrasaccharide.

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen-containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s-b-polyacrylonitrile, poly(ethylene glycol)s-b-poly(acrylonitrile-co-vinyl acetate), poly(ethylene glycol)s-b-polyacrylamide, poly(ethylene glycol)s-b-poly(acrylamide-co-vinyl acetate), poly(1-chloromethyl ethylene glycol)-bpoly(acrylonitrile-co-vinyl acetate), and bis[poly(ethylene glycol terephthalate)]-b-poly(acrylonitrile-co-vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999

Variability of Suberin Composition of Reproduction Cork from Quercus suber Throughout Industrial Processing

Summary The chemical composition of suberin was studied in cork planks from three different trees of Spanish Quercus suber at four different stages of the industrial processing of first transformation: stripping (a), first rest (b), boiling followed by open air rest (c1) and boiling followed by store-room rest (c2). The monomeric composition was determined by gas chromatography/mass spectrometry in the product of depolymerization of the free of extractives cork with sodium methoxide-methanol. The average concentrations of the main monomers were: 1-alkanols (C20–C26) 4.17 %; alkanoic acids (C20–C26) 5.99%; α, ω-alkanedioic acids (C16–C24) 6.20%; ω-hydroxy-alkanoic acids (C20–C26) 29.41%; erythro and threo-9,10-dihydroxyoctadecanedioic acids 6.76%, erythro- and threo-9,10,18-trihydroxyoctadecanoic acids 9.50%, 9,10-epoxy-18-hydroxyoctadecanoic acid 2.72% and 9,10-epoxy-octadecanedioic acid 2.93% and ferulic acid 5.05%. Significant differences were observed between samples taken at the stripping and after boiling with store room rest, and both groups of samples differed from those picked after the other two processing stages. Ten components were selected as providing the greatest discrimination among stages: 9-octadecenedioic, 18-hydroxy-9-octadecenoic, eicosanedioic and 9,10-epoxy-18-hydroxy-octadecanoic acids, tetracosanol, and five unidentified components.

Use of reversed polarity and a pressure gradient in the analysis of disaccharide composition of heparin by capillary electrophoresis

A capillary electrophoresis method with reversed polarity, combining both the application of a voltage and a pressure gradient between the buffer vials, was developed for the analysis of eight heparin-derived Δ-disaccharides obtained by enzymatic depolymerization. A 60 m M formic acid buffer at pH 3.40 was selected as running electrolyte, with an applied voltage of −15 kV and an overimposed pressure gradient (3.45·10 −3 MPa) for 6 min from inlet to outlet starting at 20 min. Figures of merit such as run-to-run and day-to-day precision, and limits of detection were established. The electrophoretic method was applied to the analysis of depolymerization products of different kinds of heparins. The composition of the depolymerization buffer was selected in order to reduce baseline distortions in the electrophoretic separation, thus a buffer solution containing 20 m M Tris, 50 m M sodium chloride, and 3 m M calcium chloride at pH 7.10 was used. Percentages of molar disaccharide compositions for unfractionated heparins from porcine, bovine and ovine intestinal mucosa, and bovine lung were determined. In addition, low-molecular-mass heparins from bovine and porcine intestinal mucosa were analysed as well.

Determination of furanic compounds in insulating oil by high performance liquid chromatography/mass spectrometry using atmospheric pressure chemical ionization

A method has been developed to determine furanic compounds in insulating oil matrix using liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. The examined samples were provided from model experiments and also from several high voltage functioning transformers. To increase sensitivity of the method six furanic compounds (determined by model experiments) were quantified by selected ion monitoring, and quantitation was based on the marker peaks. Oil samples were prepared using solid phase extraction. The results are suitable for evaluation of model experiments and also to solve problems of calibration. From extracts of oil samples taken from functioning transformers cellulose depolymerization products have been identified, and their amounts were found to be valuable in assessing the condition of the transformer (fault diagnosis). © 1998 John Wiley & Sons, Ltd.

Glycolysis of poly(ethylene terephthalate) wastes in xylene

To reclaim the monomers or prepare intermediates suitable for other polymers zinc acetate catalayzed glycolysis of waste poly(ethylene terephthalate) (PET) was carried out with ethylene or propylene glycol, with PET/glycol molar ratios of1 : 0.5–1 : 3, in xylene at 170–245°C. During the multiphase reaction, depolymerization products transferred to the xylene medium from the dispersed PET/glycol droplets, shifting the equilibrium to glycolysis. Best results were obtained from the ethylene glycol (EG) reaction at 220°C, which yielded 80 mol % bis-2-hydroxyethyl terephthalate monomer and 20 mol % dimer fractions in quite pure crystalline form. Other advantages of employment of xylene in glycolysis of PET were improvement of mixing at high PET/EG ratios and recycling possibility of excess glycol, which separates from the xylene phase at low temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2311–2319, 1998

Glycolysis of poly(ethylene terephthalate) wastes in xylene

To reclaim the monomers or prepare intermediates suitable for other polymers zinc acetate catalayzed glycolysis of waste poly(ethylene terephthalate) (PET) was carried out with ethylene or propylene glycol, with PET/glycol molar ratios of1 : 0.5–1 : 3, in xylene at 170–245°C. During the multiphase reaction, depolymerization products transferred to the xylene medium from the dispersed PET/glycol droplets, shifting the equilibrium to glycolysis. Best results were obtained from the ethylene glycol (EG) reaction at 220°C, which yielded 80 mol % bis-2-hydroxyethyl terephthalate monomer and 20 mol % dimer fractions in quite pure crystalline form. Other advantages of employment of xylene in glycolysis of PET were improvement of mixing at high PET/EG ratios and recycling possibility of excess glycol, which separates from the xylene phase at low temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2311–2319, 1998

Liquefaction of Cellulosic Wastes VI. Oxygen Compounds in Pyrolytic Oil and Water Fractions

Liquid hydrocarbon oil and water have been produced from the liquefaction of cellulosic matter present in municipal solid wastes. The produced pyrolytic oil and water fraction seemed to be contaminated with considerable amounts of oxygen compounds as compared with fuels derived from a petroleum origin. The oxygen compounds included organic acids (fatty and naphthenic acids), phenols, and carbonyl compounds. These classes of oxygen compounds were extracted selectively from the pyrolytic oils and water using chemical extraction methods. Methyl esters of fatty acids and 2,4-dinitrophenylhydrazones of carbonyl compounds were identified by gas chromatography and thin layer chromatography, respectively. It was suggested that the identified oxygen compounds could be produced from the pyrolysis of volatiles (e.g., levoglucosane, which is the primary product of cellulose depolymerization) via different mechanistic pathways.

Thermal Ring‐Opening Polymerization of Hydrocarbon‐Bridged [2]Ferrocenophanes: Synthesis and Properties of Poly(ferrocenylethylene)s and Their Charge‐Transfer Polymer Salts with Tetracyanoethylene

AbstractThe poly(ferrocenylethylene)s [Fe(η‐C5H3RCH2)2]n 5a and 5b (a: R = H, b: R = Me) have been prepared by thermal ring‐opening polymerization of the corresponding strained hydrocarbon‐bridged [2]ferrocenophanes [Fe(η‐C5‐H3RCH2)2] (4a and 4b). An X‐ray diffraction study of 4a indicated significant strain. Polymer 5a was crystalline and insoluble in common organic solvents and was characterized by solid‐state 13C NMR. Polymer 5b, which was soluble in organic solvents, was characterized by 1H and 13C NMR, UV/visible spectroscopy and elemental analysis. Its molecular weight distribution was bimodal (gel permeation chromatography: Mw = 9.6 × 104, Mn = 8.6 × 104 for the high molecular weight fraction, Mw = 4.8 × 103, Mn = 3.5 × 103 for the oligomeric fraction), suggesting two polymerization mechanisms. The UV/visible spectrum implied a localized structure for the polymer backbone. Cyclic voltammetry revealed that 5b undergoes two reversible oxidations in CH2Cl2 solution at–0.25 and–0.16V. The redox coupling is indicative of only a small degree of interaction between the iron centres. Thermogravimetric analysis indicated that 5a and 5b are thermally stable to ca. 300–350°C under N2. At higher temperatures they yield ferromagnetic iron carbide ceramics 6a and 6b (ca. 50% and 32%, respectively, at 600°C) together with molecular depolymerization products. The reaction of 5b with tetracyanoethylene (TCNE) yielded insoluble and soluble oxidized products 11 and 12, which differed in the degree of oligomerization of the TCNEy‐x counterions. These products were characterized by IR, elemental analysis, ESR spectroscopy, and magnetic susceptibility measurements. The last revealed the presence of significant antiferromagnetic interactions in 12.

Acid-catalyzed cracking of polystyrene

The effects of catalyst acidity and the restricted reaction volume afforded by HZSM-5 on the volatile cracking products derived from poly(styrene) are investigated. Three catalysts: silica/alumina, HZSM-5, and sulfated zirconia, were employed as cracking catalysts. Styrene, which is the principal radical depolymerization product from poly(styrene), is a minor catalytic cracking product. The most abundant volatile product generated by catalytic cracking is benzene. Alkyl benzenes and indanes are also detected in significant yields. Various thermal analysis techniques are employed to obtain volatilization activation energies for polymer-catalyst samples and to elucidate probable reaction pathways. Detected products are explained by reaction mechanisms that begin with protonation of poly(styrene) aromatic rings. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1287–1298, 1997

Biodegradation of crosslinked acrylic polymers by a white-rot fungus

Two synthetic superabsorbent crosslinked acrylic polymers were mineralized by the white-rot fungus Phanerochaete chrysosporium. The amount of polymer converted to CO(2) increased as the amount of polymer added to the cultures increased. In the presence of sufficiently large amounts of the superabsorbents, such that all of the culture fluid was absorbed and a gelatinous matrix was formed, the fungus still grew and mineralization was observed. Neither the polymers, nor their degradation products were toxic to the fungus. While the rates of mineralization were low, all of the polymers incubated in the liquid fungal cultures were completely depolymerized to water soluble products within 15-18 days. The depolymerization of the polymers was observed only in nitrogen limited cultures of the fungus which secrete the lignin degradation system, however, the water soluble products of depolymerization were mineralized in both nutrient limited and sufficient cultures of the fungus. The rate of mineralization of the depolymerized metabolites was more than two times greater in nutrient sufficient cultures. Following longer incubation periods, most (> 80 %) of the radioactivity was recovered in the fungal mycelial mat suggesting that carbon of the polymer had been converted to fungal metabolites.