bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenges in polypropylene by chemical modification
Authors: Rätzsch Manfred , Bucka Hartmut , Hesse Achim , Reichelt Norbert , Borsig E.
Published: March 2011

Radical reactions of i‐PP are a well known technical process for the chemical degradation to increase the flowability of the i‐PP melt. By decreasing the temperature and increasing the life time of the PP‐radicals, a process to synthesize long chain branched i‐PP, was developed. The long chain branched‐i‐PP allows to introduce the i‐PP in processing technologies as blow moulding film technology or foaming technology. The mechanism will be discussed.

The radical grafting of Polypropylene (PP) becomes more important for the developing of PP‐alloys with extended properties. Methylmethacrylate and styrene were polymerized and grafted in PP at low temperatures in solid state. Grafting and polymerizing in solid state means solving the monomers in the PP‐powder directly from the reactor without contacting with oxygen (air). The reaction is started by the thermal decomposition of a peroxide. The reactivity of the primary radicals from the peroxide and the transfer reactions of the polymer radical of the PMMA or PS influences the amount of the grafted polymer. The solubility of the monomers and the peroxide in the amorphous i‐PP‐phase was measured. The grafting yield and the dispersity of the second polymer depends on the solubility and dispersity of peroxide and monomers in the PP‐powder particles.
Modification of propylene‐ethylene copolymers by reactive extrusion
Authors: Dionisi Rodolfo A. , Failla Marcelo D. , Villar Marcelo A. , Quinzani Lidia M. , Vallés Enrique M.
Published: March 2011

The rheological properties of commercial propylene‐ethylene copolymers were modified by reactive extrusion. A dialkyl peroxide was used as initiator of the controlled degradation reaction of the starting polymers. The experiments were carried out in a twin screw extruder at different peroxide concentrations, temperatures, and screw speeds. Gel permeation chromatography was used to estimate the molecular weight distribution of the original and modified copolymers. It has been observed that the estimated molecular weight of the copolymers tends to decrease with the increase in peroxide concentration at all extrusion conditions studied. The linear viscoelastic properties of all the polymers were evaluated at different temperatures and frequencies in a rotational rheometer. Both the viscous and the elastic properties decrease with augmenting peroxide concentration. The Theological behavior of the materials is strongly affected by the global ethylene content of the copolymers. The scanning electron microscopy study did not reveal a significant difference between the morphology of the unmodified and the modified blends for a given composition of the original copolymers. In all the cases the microstructure is composed of a finely dispersed phase of ethylene‐propylene copolymer within a continuous polypropylene phase.
The effect of crosslinking on mechanical properties of ldpe filled with organic fillers
Authors: Chodak Ivan , Nogellova Zuzana , Kokta Bohuslav V.
Published: March 2011

Mechanical properties of low density polyethylene filled with various organic fillers were investigated. Different effect of different fillers on the properties was observed and the effect of crosslinking of these materials is also different. Fine anisotropic fillers behave similarly as inorganic fillers. The effect of crosslinking is the highest for composites containing large particulate fillers like beech wood flour. The effects are discussed in terms of mechanical behaviour and crosslinking degree determined from extraction or equilibrium swelling data. A formation of covalent bonds between the filler surface and polymeric matrix is proposed as a result of crosslinking.
Behaviour of chlorosulfonated polyethylene under gamma irradiation
Authors: Ivan G. , Giurginca Maria , Zaharescu Traian
Published: March 2011

The behaviour of chlorosulfonated polyethylene on gamma irradiation was investigated over the range of total absorbed dose of 5 to 550 kGy. The structural modifications were followed by infrared spectroscopy and some main kinetic characteristics of the process were assessed. Determinations of gel content and evaluation of changes in sulphur and chlorine content were correlated with the evolved amounts of hydrochloric acid and with changes in unsaturation of polymers.
Synthetic resins as designable supports for metal‐based chemistry: The issue of their nanomorphology and molecular accessibility
Authors: Corain Benedetto , D'Archivio Angelo A. , Galantini Luciano , Lora Silvano , Panatta Alberto , Tettamanti Enzo
Published: March 2011

Macromolecular cross‐linked ligands containing pyridyl pendant groups are characterized by a combination of inverse steric exclusion chromatography, ESR and NMR spectrometries in water and methanol. On the basis of the relevant results, methanol is seen to be clearly the best swelling agent and it is chosen as medium for CuII coordination.
Metal ion effects in ionic copolymers
Authors: Eisenberg Adi , Bartels Carl
Published: March 2011

This paper presents a discussion of four areas in which the interaction between organic polymers and metal species is of importance. The first section discusses the effect of metal ions in random ionomers in bulk, where the presence of ions strongly influence the mechanical properties. The next topic covers the influence of metal ions on aqueous solutions of block copolymers, and describes the morphogenic effects seen in such systems. The third section deals with the use of metal ions in non‐aqueous solutions of block copolymers leading to the formation of microreactors with a high degree of size control. Finally, the attachment of organometallic species to the corona of block copolymer micelles in non‐aqueous solution is discussed in terms of the effect of the metal on the micelle dimensions.
Macrocyclic metal complexes as ladder polymers
Authors: Hanack Michael , Stihler Patrick
Published: March 2011

Macrocyclic bis‐dienes and diendienophile were prepared in Diels‐Alder reactions starting from the bis‐dienophilic (hemiporphyrazinato)nickel complex 1. Compound 1 was reacted either with the tetraene 2 or with tetra‐phenylcyclopentadienone (4). By combination of macrocyclic bis‐dienes and bis‐dienophiles, ladder‐type oligomers (e.g. 9 or 10) were synthesized. The described oligomers are precursors for the corresponding conjugated oligomers, which are of interest as organic conductors. The preparation of the corresponding phthalocyanine compounds e.g. 13–16 and a method for obtaining the wanted “D2h” phthalocyanine 19 without using tedious methods are reported.
Unique behaviors of polymers having metalloporphyrin as their side chains
Authors: Kamachi Mikiharu
Published: March 2011

Several kinds of polymers having tetraphenylporphyrin (TPP) or some metallotetraphenylporphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) moieties as their side chains have been prepared by the radical polymerization of the corresponding vinyl monomers. Visible spectra of these polymers show the clear hypochromism in the Soret bands of the tetraphenylporphyrin moieties as compared with those of the corresponding monomers. Polymer effects were clearly observed in the magnetic behaviors and the oxygen adsorption of paramagnetic metalloporphyrin moieties. In addition, polymer effects on photophysical and photochemical behaviors of ZnTPP were found in the amphiphilic polymers covalently tethered with small amounts of ZnTPP and hydrophobic substituents above a critical content, which form hydrophobic domains due to aggregation of the hydrophobic groups in aqueous solution.
Metal‐catalyzed organosulfur cathodes for rechargeable lithium batteries
Authors: Oyama Noboru , Pope John M. , Tatsuma Tetsu , Hatozaki Osamu , Matsumoto Futoshi , Chi Qijin , Paulson Scott C. , Iwaku Masahiro
Published: March 2011

Extensive studies were carried out to apply composite materials composed of polyaniline (PAn) and 2,5‐dimercapto‐1,3,4‐thiadiazole (DMcT) to develop cathode materials which exhibit high energy densities. Previous results have established that composites of PAn and DMcT which are coated onto copper substrates exhibit greatly enhanced charge and discharge performance. It is shown that composite materials composed of DMcT, PAn, and Cu ion have the ability to be reversibly charged and discharged at ca. 260 A h per kg‐cathode (ca. 830 W h per kg‐cathode) for more than 80 cycles. These two results are explored in general in this contribution via investigation of the electron transfer reactions between the components using UV/Vis and investigation of the copper substrate/DMcT chemistry using electrochemical quartz crystal microbalance and phase modulated interferometric microscopy.
Enhanced carrier‐transfer in multi‐layered organic thin film: Application to electrochromism and electroluminescence
Authors: Toshima Naoki , Tominaga Tsuyoshi
Published: March 2011

Multi‐layered organic thin films were prepared by stepwise vapor deposition of planar molecules with delocalized π‐electrons on indium tin oxide (ITO) glass or KCl crystalline surface. The order of the deposition of π‐planar molecules with different redox potential can control enhancement or inhibition of the hole or electron transfer according to the concept of “sequential potential field”, or a potential cascade by the organization of redox components. This concept is here applied to electrochromic or electroluminescent devices composed of multi‐layered organic thin films.
An overview on the development of macromolecule‐metal complexes and brief sketch on their recent trends
Authors: Tsuchida Eishun
Published: March 2011

In early 1970s, there was growing tendency that the macromolecule‐metal complexes should have been understood as a molecular science among many international scientists. Y. Y. Jiang, Academia Scinica, firstly proposed an international symposium on this field and the first congress (MMC‐1) was held in 1985. From the 4th one, this series has been under the auspices of IUPAC and we have reached MMC‐7. The current interests in this field are, for example, photoinduced electron transfer, outer‐sphere process, chemical reactions in subnano‐geometrical space, multi‐electron transfer reaction. They are all linked to the high performances of advanced materials. The role of macromolecules in macromolecule‐metal complexes are summarized and recent topics of this area are described.
Development and some aspects of the present situation of macromolecule‐metal complexes
Authors: Wöhrle Dieter , Suvorova Olga
Published: March 2011

Macromolecule metal complexes (MMCs) — the combination between a macromolecule, a metal chelate/complex/ion or cluster — are dominating factors for different functions in living systems, and are becoming more and more important in different sciences and applications as artifical synthesized systems.
Quo vadis ionic polymerizations
Authors: Kennedy Joseph P.
Published: March 2011

This presentation concerns subjective comments in respect to the status and foreseeable future of ionic polymerizations, i.e., cationic‐, anionic‐, and ionic ring opening polymerizations.
Tandem transition metal catalyzed isomerization and cationic polymerization
Authors: Crivello James V. , Rajaraman Surésh K.
Published: March 2011

A wide variety of mono‐, di‐ and multifunctional allyl ethers and related compounds are readily polymerized using a newly discovered polymerization reaction which has been termed: a transition metal‐catalyzed tandem isomerization and cationic polymerization. Employing dicobalt octacarbonyl in combination with organosilanes, the polymerization of these monomers takes place rapidly to give high molecular weight polymers.
Design of new polymer architectures by combination of anionic and cationic living polymerization techniques
Authors: Deffieux Alain , Schappacher Michel
Published: March 2011

The grafting of polystyryl lithium onto poly(chloroethyl vinyl ether) chains has been investigated. The reaction proceeds cleanly and quantitatively thus allowing the synthesis of comblike polymers. Since the dimensions of the polystyrene branches and of the poly(chloroethyl vinyl ether) backbone can be controlled by living polymerizations, both the length and the number of branches of the graft copolymers can be tuned. The latter behave as star polymers. The possibility to initiate a new cationic polymerization of chloroethyl vinyl ether from polystyrene branches bearing acetal termini in order to prepare the corresponding stars with poly(chloroethyl vinyl ether‐b‐ styrene) branches is also examined.

Finally access to hyperbranched polymers of controlled architecture and dimensions by deactivation of a second amount of polystyryl lithium onto the last blocks of poly(chloroethyl vinyl ether) is also reported.
Star‐branched and hyperbranched polyisobutylenes
Authors: Puskas Judit E. , Grasmüller Martin
Published: March 2011

The synthesis of branched (star‐branched and hyperbranched) polyisobutylenes (PIBs) is described in this paper. Multiarm‐star and brush‐like structures were prepared by using a tert ‐hydroxy functionalized polystyrene macroinitiator (4‐(l‐hydroxy‐l‐methylethyl)styrene‐co‐styrene (HMESt‐co‐St). These polymers were characterized by SEC‐light scattering. The first successful synthesis of gel‐free high molecular weight hyperbranched PIBs was achieved by using HMESt as an inimer (initiator‐monomer) in conjunction of living isobutylene (IB) polymerization. Initial characterization of the structure of this polymer included SEC analysis and selective destruction of the HMESt‐junctions.
The roles of electron donors in the cationic polymerization
Authors: Guanying Wu , Yixian Wu , Wenli Guo , Guoying Rao
Published: March 2011

Electron donors (EDs) according to their different functions in cationic polymerization systems can be divided and summarized as follows: Initiators, adventitious impurities, aromatic solvents or polar diluents, monomers electron donor (ED) modifiers. Their behaviors and roles in the course of polymerization can be well explained in terms of complexation competition and equilibrium. In the present paper only initiators and ED modifiers are primarily investigated and discussed.
The anionic polymerization of dialkylaminoisoprenes‐5‐copolymerization with 1,3‐butadiene
Authors: Mannebach Gerd , Bieringer Ruth , Morschhäuser Roman , Stadler Reimund
Published: March 2011

The anionic copolymerization of 5‐(N,N‐dialkylamino)isoprenes and 1,3 ‐butadiene was investigated in hexane. We found that basicity and increasing amount of the polar monomer has a strong influence on the microstructure of polybutadiene. All tested 5‐(N,N‐dialkylamino)isoprenes were incorporated much faster into the copolymer than butadiene. Depending on the alkyl substituents the resulting copolymer is either a nearly perfect diblock or shows a considerable tapered structure.
New σ‐μ ligands for the anionic polymerization of methacrylates in apolar medium
Authors: Marchal Jérǒme , Fontanille Michel , Gnanou Yves
Published: March 2011

Poly(methyl methacrylate) (PMMA) has been anionically synthesized at high temperature and in apolar media, using diphenylhexyllithium (DPHLi) as initiator and a novel σ‐μ chelating ligand to curb the side reactions. It has been indeed found that lithium 2‐(dimethylamino‐)ethoxide is a very efficient σ‐μ ligand that prevents the anionic polymerization of methyl methacrylate (MMA) from being disrupted by significant secondary termination reactions. Ligand/initiator molar ratio, solvent polarity, temperature, monomer and active center concentrations are proved to be key parameters in the control of the polymerization process.
Ligated anionic polymerization: An innovative elf‐atochem technology for the polymerization of (meth)acrylates
Authors: Navarro Christophe , Marcarian Xavier , Vuillemin Bruno
Published: March 2011

Admittedly performing materials, (meth)acrylic polymers, used in a wide variety of applications, are traditionally produced by radical polymerization processes. The extension of living polymerization, originally developed for dienes and vinyl‐aromatics, to (meth)acrylic polymers, would be an interesting opening to a variety of products with a large scope of properties and applications. However, this method suffers from chemical and technical limitations when applied to (meth)acrylates under the usual conditions of solvent and temperature. We report how alkoxy alkoxides‐based systems combined with a recent Elf Atochem process offer attractive conditions for ultra‐fast anionic polymerization of (meth)acrylates at high solid content. Applications to cost effective syndiotactic poly(methyl methacrylate) and block copolymers syntheses are described.
Polymer synthesis using functionalized alkyllithium initiators: Telechelic, heterotelechelic and functionalized star‐branched polymers
Authors: Quirk Roderic P. , Jang Sung H. , Yang Huimin , Lee Youngjoon
Published: March 2011

Alkyllithium initiators with hydroxyl groups protected with either t‐butoxy or t‐butyldimethylsiloxy groups have been used to prepare α‐functionalized polymers, α,ω‐telechelic, α,ω‐heterotelechelic and multifunctional star‐branched polymers.
Cationic equilibrium ring‐opening polymerization of bicyclic monomers and its application to chemical recycling
Authors: Endo Takeshi , Sanda Fumio
Published: March 2011

Spiro orthoesters give poly(cyclic orthoester)s by single ring‐opening polymerization in the presence of acid catalysts, and this process undergoes the equilibrium polymerization. We have applied the function of equilibrium polymerization to chemical recycling of polymeric materials. Crosslinked poly(cyclic orthoester)s, prepared by radical additions of poly(cyclic orthoester)s possessing exomethylene groups and dithiols, efficiently decrosslinked to bifunctional spiro orthoesters in the presence of CF3CO2H in CH2Cl2. The dithiol‐linked bifunctional spiro orthoester monomers, prepared by the radical additions of spiro orthoester possessing exomethylene group and dithiols, afforded the corresponding crosslinked polymers in the presence of CF3CO2H as a catalyst in bulk. The decrosslinking of the obtained crosslinked polymer proceeded quantitatively to obtain the corresponding bifunctional monomer at room temperature in CH2Cl2. Further, an acid‐catalyzed reversible crosslinking‐decrosslinking of a polymer having a spiro orthoester group in the side chain was carried out. The copolymer obtained by the radical copolymerization of 2‐methylene‐1,4,6‐trioxaspiro[4.6]undecane with acrylonitrile was treated with CF3CO2H at −10 °C in CH2Cl2 to afford the crosslinked polymer quantitatively. The crosslinked polymer was then treated with CF3CO2H at room temperature at a low concentration in CH2Cl2 to recover the original polymer.
Regioselective ring‐opening anionic polymerization of β‐lactones
Authors: Jedliński Zbigniew
Published: March 2011

New aspects of anionic polymerization of 4‐membered lactones are presented, attention being paid to regioselectivity of ß‐lactones ring‐opening reactions. It has been demonstrated that supramolecular complexes of alkali metal alkoxides used as initiators enable control of lactones polymerization, and due to anion activation yield polymers with specific molecular architecture. Synthesis of the analogue of natural polymer poly(3‐hydroxybutyrate) via anionic polymerization of ß‐butyrolactone is discussed.
Synthesis of novel polymeric materials based on aliphatic polyesters by combination of different controlled polymerization methods
Authors: Jérǒme Robert , Mecerreyes David , Tian Dong , Dubois Philippe , Hawker C. J. , Trollsas M. , Hedrick J. L.
Published: March 2011

Combination of the living ring‐opening polymerization (ROP) of ε‐CL and lactides with the “controlled” free radical polymerization of styrene and methacrylic monomers is a versatile strategy for the synthesis of well‐defined block and graft copolymers. In this respect, the dual “living” polymerization strategy in which two different functional groups on a single molecule used to initiate the two controlled mechanisms is particularly efficient. Combination of ROP and step‐growth polymerization is another versatile methodology for the preparation of a large variety of new materials, e.g. polyimide nanofoams, polyester/silica hybrid materials and star and branched polyesters by dendritic initiation.
Selectivity of siloxane‐siloxane copolymer synthesis by ring opening polymerization
Authors: Kaźmierski Krzysztof , Cypryk Marek , Chojnowski Julian
Published: March 2011

Anionic ring‐opening polymerization of 1,1‐diphenyl‐2,2,3,3‐tetramethylcyclotetrasiloxane was studied as a model polymerization of cyclic siloxane with mixed siloxane units. Sequencing of siloxane units was investigated by 29Si NMR. Various initiator‐promoter‐solvent systems were used. In most cases reaction was highly chemoselective, as sequencing were not affected by back biting, chain transfer and terminal unit exchange processes. Reactions showed, however, low regioselectivity in monomer ring opening. The coordination of the metal counter‐ion to monomer plays a considerable role in propagation and affects sequencing of the polymer.
Specific phenomena during the copolymerization of trioxane and ethylene oxide
Authors: Masamoto Junzo , Matsuzaki Kazuhiko
Published: March 2011

We, at Asahi Chemical in Japan, have industrialized three types of polyacetal resins, that is, the acetal homopolymer, copolymer and block copolymer using anionic, cationic and anionic polymerization techniques, respectively. During this industrialization, we observed various phenomena, which were not previously reported. First, the authors outline the three technologies for producing each type of polyoxymethylene from an industrial viewpoint. Next, the authors discuss a newly found reaction during the induction period of the trioxane and ethylene oxide copolymerization. Experimental proof of direct ring expansion between the reaction of trioxane and ethylene oxide is discussed and various novel cyclic compounds are also shown. To the best of our knowledge, this reaction may be the world's first experimental proof of direct ring expansion of the reaction of a cyclic monomer. Third, the authors also discuss the newly founded morphospecific polymer from the copolymerization of trioxane and ethylene oxide using boron trifluoride dibutyl ether as an initiator.
Mechanism of particle formation and kinetics of the dispersion polymerization of cyclic esters
Authors: Slomkowski Stanislaw , Gadzinowski Mariusz , Sosnowski Stanislaw
Published: March 2011

Pseudoanionic and anionic polymerizations of ε‐caprolactone and lactides in 1,4‐dioxane:heptane mixtures containing poly(dodecyl acrylate)‐g‐poly(ε‐caprolactone) yield polyesters in form of microspheres. Monitoring partition of active centers between solution and microspheres revealed that particles are formed during initial period, when macromolecules reach their critical masses (ca. 1 000) and became insoluble. Then, propagation proceeds inside of microspheres into which monomer diffuses from solution. Monitoring of variation of the number of particles in a unit volume of reaction mixture with time indicated that after a primary nucleation the delayed nucleation and aggregation are absent. In effect, microspheres with narrow diameter distribution are obtained. Kinetic measurements revealed that in the dispersion pseudoanionic (initiator (CH3CH2)2AlOCH2CH3) and anionic (initiator (CH3)3SiONa) polymerizations of ε‐caprolactone the overall rates of monomer conversion are from 10 to 30 times higher than for the corresponding polymerizations in solution (THF solvent). Analysis of kinetic equations indicated that the observed faster monomer conversions in polymerizations in dispersed systems are due to the high local concentrations of active centers and monomer in growing microspheres.
Carbenoids, nitrenoids, oxenoids: Very electrophilic „anions”︁
Authors: Boche Gernot
Published: March 2011

The rather interesting question why the „anionic”︁ carbenoids 1a, nitrenoids 1b and oxenoids 1c react so easily with nucleophiles is answered by experimental investigations of their structure and by means of quantumchemical calculations. It turns out that the bond to the leaving group (C(N,O)‐X is weakened (elongated), and that the energy of the σ*C(N,O)‐X orbital is lowered. This allows for a more facile substitution of X by a nucleophile. The substitution of X− is further supported by the metal cation M+.
Polymer catalysts for important photoelectron transfer reactions
Authors: Guillet James E. , Burke Nicholas A. D. , Nowakowska Maria , Paone Sergio
Published: March 2011

Photozymes are novel water‐soluble polymers made by the copolymerization of mixtures of hydrophobic and hydrophilic monomers, some of which contain chromophores capable of absorbing light and transmitting the excitation energy to selected traps by means of the antenna effect. The interactions between these groups and water force the polymer to adopt a hypercoiled conformation with hydrophobic pockets similar to those in the catalytic sites of natural enzymes. Hydrophobic organic compounds in the water solution will seek out and localize themselves in these regions, where they are subjected to electronic energy transfer from the light‐excited antenna chromophores. The chemical reactions which occur are often different and more specific than in the case of photoreactions in common organic solvents. In a number of cases the reactions appear to proceed by an electron transfer mechanism. This paper summarizes recent results on the dechlorination of chlorinated aromatic and aliphatic compounds, and laser studies of multiphoton processes in aromatic compounds such as 9‐(acetoxymethyl)phenanthrene (AMP).
Novel electron transfer polymerization processes with alkali metal supramolecular complex as catalyst
Authors: Jedliński Zbigniew
Published: March 2011

Single electron transfer SET induced usually by organometallic complexes of transition metals or alkali metal complexes of arenes e.g. naphthalene is common in organic reactions. In this paper unusual two‐electron transfer to suitable acceptor molecule mediated by recently discovered alkali metal supramolecular complexes in aprotic etheral solvents is presented. The capability of these solutions of transferring two electrons to a suitable organic substrate and formation of corresponding carbanions opens new door in synthetic chemistry. The carbanions are interesting synthons in the many organic reactions and catalysts in anionic polymerization processes. Reactions of some vinyl compounds, alkyl and silyl halides, as well as ring‐opening polymerization of β‐lactones and oxiranes are discussed.
Mechanistic aspects of the olefin polymerization with metallocene catalysts
Authors: Kaminsky W.
Published: March 2011

With C1‐, C2‐ or Cs‐symmetric metallocenes, different intermediates and types of copolymers can be obtained from randomly distributed to alternating structures. Substitution of the Cp‐ring in [Me2C‐(tert‐Bu Cp)(Flu)]ZrCl2 yields ethene/norbornene copolymers with an alternating structure, because the rigid norbornene can only be inserted from the open side of the metallocene. By variation of the polymerization parameters, copolymers with glass transition temperatures above 180°C and molecular weights > 100 000 are synthesized. By supporting different metallocenes on a silica/methylaluminoxane (MAO) carrier the deactivation reaction under electron and hydrogen transfer can be suppressed. This is proved for different Al/Zr ratios when trimethylaluminum (TMA) is used as cocatalyst by the lack of methane evolution by metallocenes and by near independence of the polymerization activity on the prereaction time, after reaching maximum activity. Aluminumalkyls and MAO leach Cp2ZrCl2 from the carrier, the leached metallocene is only active in polymerization by adding MAO.
Electron transfer in some nucleophilic reactions
Authors: Lund Henning , Daasbjerg Kim , Lund Torben , Pedersen Steen U.
Published: March 2011

Using kinetic, steric and thermodynamic results it is argued that the rate‐determining step in some aliphatic, nucleophilic substitutions is the transfer of an electron.
Scission of C‐C σ‐bonds via electron transfer processes
Authors: Maercker Adalbert , Daub Volker E. E. , Deskowski Andrea , Klein Klaus‐Dieter , Oeffner Kristian S. , Schutz Heiko
Published: March 2011

Certain hydrocarbons, preferrable strained ones, can be cleaved via electron transfer processes whereby lithium dust or lithium 4,4′‐di‐tert‐butylbiphenylide (LiDBB) have been used as electron transfer reagents. For the scission of a C‐C σ‐bond the presence of a π‐system in the neighborhood (α or β) is an absolute prerequisite.
Electron photoejection and its application in studies of electron transfers
Authors: Szwarc Michael
Published: March 2011

The principle of electron photoejection technique is explained. This approach leads to the formation of transient spectra of unstable intermediates, allowing their recording and providing their extinction coefficients. Moreover, it permits determination of their electron affinities and the rates of their reactions, whether spontaneous or with some added substrates. Application of this technique to studies of disproportionation of radical anions have been most profitable. It led to the determination of the forward and backward rate constants of disproportionation of a variety of radical anions, and to discovery and quantification of some subtle features of these reactions. Electron photoejection technique provided the data characterizing the electron transfer initiation of anionic polymerization and clarified some of its features. Other opportunities provided by the electron photoejection in studies on electron transfer processes are suggested.
A chemical scale for evaluating the electron transfer ability of alkylcopper reagents
Authors: Yamamoto Yoshinori , Chounan Yukiyasu
Published: March 2011

In order to evaluate the electron transfer ability of organocopper reagents, the reactions of appropriate Michael acceptors with methyl and butylcopper reagents were investigated. The ratio of the conjugate adduct and reduction product was used as a chemical scale for evaluating the electron transfer ability of the alkylcopper reagents. Consequently, the electron transfer ability of methyl and butylcopper reagents is in the following order; Me3CuLi2 > Me2CuLi >> Me2Cu(CN)Li2 > MeCu > MeCu(CN)Li; Bu2CuLi > BuCu(CN)Li ‐ Bu2Cu(CN)Li2 > BuCu.
Co‐pyrolysis of waste polymers with coal
Authors: Straka P. , Buchtele J. , Kovářová J.
Published: March 2011

Co‐pyrolysis of coal with waste polymers in a stationary quartz reactor was performed. Mass balance of the process was evaluated and properties of products were characterized. The main product (solid carbonaceous residue) exhibits low ash and sulfur contents and, from the point of view of application, satisfactory surface properties. Therefore, the solid residue is suitable as a smokeless fuel or as an industrial sorbent. The by‐products were tar and gas. The tar may be used as a source of chemicals or a low‐sulfur heating oil, the gas was highly calorific, therefore it may serve as a heating gas for energetical purposes.
Technical methods in plastics pyrolysis
Authors: Buekens Alfons G. , Schoeters Jos G.
Published: March 2011

Plastics pyrolysis is based on thermal and sometimes catalytic breakdown of the polymer structure. The target product may be monomer (from PMMA, PTFE, PS), oil fractions ranging from petrol (C5‐C10) and kerosene (C10‐C15) to waxy fractions (≥C20), aromatics, synthesis raw materials formed by hydrogenation or synthesis gas (H2, CO). The desired product determines the operating conditions required and hence the technology used. A survey is given of laboratory, pilot and industrial scale reactors, pyrolytic extruders, stirred tanks and single‐ or double‐bed fluidized systems. Moreover, the use of plastics in oil refinery‐based processes, such as fluid catalytic cracking, hydrocracking, viscosity breaking and delayed coking, and also (coal‐derived) hydrogenation and gasification are briefly covered. The product distribution in a pyrolysis process has to be derived experimentally, with the operating temperature, heating rate, catalytic effects, residence time of feed material and reaction products, reaction pressure, possible supply of reactive gases (such as oxygen, hydrogen) and, of course, the chemical constitution and structure of the original plastics as major factors. Pyrolysis involves the breaking of chemical bonds and is normally endothermic. The required heat of reaction can be supplied indirectly through the reactor walls, by a circulating heat carrier, which may be the polymer content of the reactor or the sand in a dual fluid‐bed system, or by partial oxidation. The reactor technology is generally determined by the temperature level required, heating method, necessary residence time and possibly the presence of a catalyst, required to rearrange linear structures to high‐octane‐number branched ones, to eliminate heteroatoms (Cl, N, O, S), etc. Some potential operating problems are addressed in an EU‐funded project with acronym Cycleplast, a joint project of five teams from Central and Western Europe, the aims of which are briefly described.
Polymer cracking — New hydrocarbons from old plastics
Authors: Hardman Stephen , Wilson David C.
Published: March 2011

The management of packaging waste is a significant issue covered by European Union legislation which sets demanding targets for the recycling of all materials, including plastics. Significant progress has been made by an industry consortium, led by BP Chemicals, in developing technology to help meet the recycling targets.
New chemical recycling methodologies: Hydrous pyrolysis to recover monomers from polyolefins
Authors: Audisio Guido , Bertini Fabio , Beltrame Pier Luigi , Bergamasco Laura , Castelli Antonella
Published: March 2011

Thermal degradation of polystyrene has been investigated in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were carried out in closed systems under inert atmosphere, in the temperature range 300–350 °C, at pressures up to 180 atm, for 1–120 h. The results showed that the presence of water increases the yields of volatile products, mainly in the first steps of the pyrolytic process, with a high selectivity in the monomer. In order to improve the phase contact between water and polymer during the pyrolysis, some runs have been carried out on silica‐supported polystyrene and using a stirred reactor. Under these conditions, the above effects appeared to be greatly enhanced. The best recovery of styrene, close to 71%, has been achieved at 320 °C and 8 h.
Quality assurance of recycled engineering plastics using blend technology
Authors: Klason Carl , Bertilsson Hans , Xiaodong Liu
Published: March 2011

The automotive, electrical and electronic sectors account for over 12% of all plastics consumed. A large fraction of these polymers are engineering plastics representing a value considerably higher than that of commodity thermoplastics; hence, mechanical recycling including upgrading efforts appears economically attractive. This paper shows some methods of upgrading the property profile of ABS from dismantled automobiles using polymer blend technology. The results for blends of ABS with PC or PA are reported. The aim of blending of the waste materials is twofold: to reduce the number of plastic materials to be recycled in car dismantling plants, and to improve properties of the ABS scrap, which is the main engineering plastic in the waste stream from automobiles.
Biodegradable materials — Present situation and future perspectives
Authors: Bastioli Catia
Published: March 2011

Biodegradable polymers constitute a loosely defined family of polymers that are designed to degrade through the action of living organisms. They offer a possible alternative to traditional nonbiodegradable polymers if recycling is impractical or not economical. The main driving force behind this technology is the solid waste problem, particularly with regard to the decreasing availability of landfills, the litter problem and the pollution of marine environment by non‐biodegradable plastics. Technologies like composting used for the disposal of food and yard waste are the most suitable for the disposal of biodegradable materials.

European Standardisation Committee (CEN), Organic Reclamation and Composting Association (ORCA) and German Institute for Standardisation (DIN) have already defined, at a draft level, the basic requirements for a product to be declared compostable. They are based on: complete biodegradability of the product in a time period compatible with composting, measured through respirometric tests (ASTM D5338‐9, ISO/CD14855, etc); disintegration of the material during the fermentation phase; no negative effects on compost quality; checking of laboratory‐scale results on pilot/full‐scale composting plants. These requirements set forth a common base for a universal marking system to readily identify products to be composted.

Thermoplastic starch‐based polymers and aliphatic polyesters are the two classes of biodegradable materials with the greatest near‐term potential. This paper reviews a great variety of properties, structures and biodegradation behaviour of thermoplastic starch in combination with poly(vinyl alcohol) or some aliphatic polyesters like poly(hydroxybutyrate‐co‐hydroxyvalerate), poly(lactic acid), poly(ϵ‐caprolactone) and poly(butanediyl succinate).
Conversion of polymers and biomass to chemical intermediates with supercritical water
Authors: Arai Kunio
Published: March 2011

Recent results are described on conversion of polymers and biomass to chemical intermediates and monomers by using subcritical and supercritical water as the reaction solvent. Reactions of cellulose in supercritical water are rapid (<50 ms) and proceed to 100% conversion with no char formation. They show a remarkable increase in hydrolysis products and lower pyrolysis products when compared with reactions in subcritical water. Further, there is a jump in the reaction rate of cellulose at the critical temperature of water. If the methods used for cellulose are applied to synthetic polymers, such as PET, nylon or others, high liquid yields can be achieved although the reactions require about 10 min for complete conversion. The reason is the heterogeneous nature of the reaction system. For polyethylene, higher yields of short‐chain hydrocarbons, higher alkene/alkane ratios and higher conversions were obtained in supercritical water than those obtained by pyrolysis.
Degradability of biodegradable plastic under controlled composting conditions
Authors: Nakasaki Kiyohiko
Published: March 2011

Biodegradability of poly(ß‐propiolactone) (PPL), one of biodegradable plastics, was tested in a bench‐scale composting reactor under controlled conditions, with uniform temperature, moisture content, and aerobiosis maintained. The composting raw mixture was prepared by mixing commercial dog food instead of real organic waste, saw dust as a bulking agent, commercial inoculum sold for acceleration of composting, and PPL in the ratio of 10:9:1:10 on dry weight basis. The degree and rate of PPL degradation were determined by comparing the difference in the CO2 evolution for composting with and without addition of PPL. The influence of temperature on the degradability of PPL was investigated at 40, 50, and 60 °C and the optimum temperature was found to be around 40‐50°C where ca. 40 wt.‐% of PPL was decomposed in 8 days. The effect of inoculum on the degradability of PPL during 50 °C composting was then examined, a considerable difference (100%) being observed in the biodegradability using two different inocula.
Ecological and economical aspects of polymer recycling
Authors: Brandrup Johannes
Published: March 2011

Recycling is considered to play an essential role in developing a sustainable economy. A restrictive environmental legislation has forced German economy into extensive recycling activities. Meanwhile, German society and German industry have more than six years of practical experience with recycling of postconsumer plastic waste from household packaging due to this legislative situation. It is time to critically evaluate the situation. This paper summarizes the development in Germany and tries to show ecological impacts based on a life‐cycle analysis and correlates these data with economical consequences.
Chlorinated products of plastic pyrolysis
Authors: Blazsó Marianne
Published: March 2011

The formation of various chlorinated products in pyrolysis of polymers and plastics additives was studied. Formation of chlorobenzenes (in addition to the monomers) from poly(chlorostyrene) and poly(vinylbenzyl chloride) was observed. Hydrogen chloride is only produced from these polymers at above 600 °C when the chlorine atoms are cleaved off and abstract hydrogen. A similar process takes place in aromatic chlorine‐containing dyes, in which the strong aromatic molecular structure prevents the thermal cleavage of chloroaromatic volatile products. We have observed that cupric and ferric chlorides chlorinate phenolic thermal decomposition products of plastic materials which originate either from the polymer or from the stabilizer. The highest yields of chlorophenols are obtained in pyrolysis at around 700 °C.
Rubber recycling
Authors: Schnecko H.
Published: March 2011

The report summarizes the present situation on elastomer recycling with emphasis on tires. In the introduction it outlines the differences to other polymers and gives a global breakdown of present scrap tire volumes. It then specifies the various areas and possibilities of recycling, viz, reduction, reuse (retreading), rubber crumb manufacture and use, reclaim, recover, i.e. pyrolysis, hydrogenation and conversion to energy. Finally, landfills and biodegradation are touched on.
Study of cooperative effects of silanols on modified silica by dielectric relaxation method
Authors: Alekseev A. N. , Zaitsev V. N. , Alekseev S. A. , Pecheny A. B.
Published: March 2011

Two types of chemically modified silica gels with covalently bonded hydrophobic (alkyl, SiO2‐C8) and hydrophilic (aminoalkyl, SiO2‐NH2) groups were studied by dielectric relaxation method. For SiO2‐C8 two relaxation maxima were detected at 140 and 238K. From comparison with bulk silica the lower temperature maximum was assigned to cooperative re‐orientation of residual silanols and higher one to melting of physically adsorbed water. Both maxima are much weaker for SiO2‐C8 then for bulk silica. In Arrhenius coordinates relaxation at 238K exhibits similar behavior as OH groups in polyvinyl alcohol and so it was assigned to mobility of orientation defects in mono‐dimensional chain of physically adsorbed water. For SiO2‐NH2 no low temperature relaxation effect was observed. Intensive relaxation was measured at 248 K only. Strong interaction between supramolecules of silanol groups, bonded aminogroups and adsorbed water was assumed.
Observation and simulation of PbS nonocrystal formation at the initial steps
Authors: Gurin Valerij S.
Published: March 2011

Ultrafine lead sulfide clusters are produced by the reaction of long‐chain thiols with lead ions in non‐aqueous medium, and according to X‐ray diffraction (XRD) data reveal the different steps of he bulk‐like rocksalt lattice growth. XRD pattern is simulated by the Debye formula for four model clusters (27, 75, 125, 729 atoms) and the correspondence of model and experimental clusters is shown that allows to estimate their size. Ab initio MOLCAO calculations result in energetical parameters and charge distribution for the clusters with 27 atoms. The value of energy gap indicates the true tendency of variation for the clusters of different size but left yet higher than maxima in the optical absorption at the fixed steps.
Formation of langmuir‐blodgett films containing two‐dimensional monoatomic arrays of rare‐earth cations
Authors: Khomutov Gennady B.
Published: March 2011

The work is focused on the preparation and characterisation of rare‐earth containing stearic acid Langmuir‐Blodgett (LB) films. Stearic acid monolayer behavior on the rare‐earth containing aqueous subphase have been analyzed by thermodynamic measurements. The compression isotherm shape changed substantially under varying the anion type at the constant rare‐earth cation content in aqueous subphase. The structure of formed multilayer rare‐earth containing LB films was studied using small angle X‐rays diffraction. The considerable structural defects in multilayer films were found when rare‐earth chloride solution was exploited as aqueous subphase, caused presumably by electrostatic interactions at the monolayer surface under high binding of rare‐earth cations. The use of monodentate complexones like acetic acid was proposed to form bulk phase quasi‐neutral rare‐earth complexes. The electroneutral ligand exchange reactions of such complexes with stearic acid monolayer allowed to neutralise monolayer surface under rare‐earth cations binding and to form condenced monolayer below the triple‐point temperature. The compression of such monolayer to the state of minimal compressibility and subsequent monolayer deposition resulted in the formation of high ordered LB films with high content of adsorbed multivalent rare‐earth cations arranged in two‐dimensional monoatomic arrays.
Stoichiometry effects in gaAs epitaxy for ballistic tunneling semiconductor devices
Authors: Nishizawa Jun‐Ichi , Kurabayashi Toru
Published: March 2011

The effect of stoichiometry on various features of III‐V compounds are investigated. It is shown experimentally that the optimum vapor pressure of V elements minimizes the deviation from the stoichiometric composition. Vapor pressure control technology is applied not only to the liquid phase epitaxy and bulk crystal growth but also to the surface reaction in molecular layer epitaxy.

The surface reaction and kinetic phenomena of GaAs mono‐molecular layer growth by using chemical adsorption of Ga(CH3)3 (trimethyl gallium: TMG) and arsine (AsH3) was investigated. The growth feature was strongly influenced by the surface stoichiometry of arsenic during growth. For example, the diffusion of the doped impurity is affected by the AsH3 amount of supply, the diffusion was prevented by controlling the stoichiometry. The control of stoichiometry was examined systematically and was applied for the device fabrication such as ballistic transistor.
Thiol‐stabilized CdSe and CdTe nanocrystals in the size quantization regime: Synthesis, optical and structural properties
Authors: Rogach Andrey L. , Eychmüller Alexander , Kornowski Andreas , Weller Horst
Published: March 2011

We report on the recently developed method for the synthesis, optical, and structural properties of CdSe and CdTe nanocrystals. They were formed in aqueous solutions at moderate temperatures by a wet chemical route in the presence of thiol molecules as effective stabilizing agents. The size‐selective precipitation technique was applied for the post‐preparative nanoparticle fractionation into a series of CdSe and CdTe nanocrystals with extremely narrow size distributions exhibiting mean cluster sizes in the range of 2 to 4 nm. The nature of stabilizing agent (mercaptoalcohols and mercaptoacids) had an important influence on the particle size and determines largely the photoluminescence properties. The nanocrystals were characterized by means of UV‐vis absorption and photoluminescence spectroscopy, X‐ray diffraction, and high resolution transmission electron microscopy (HRTEM).
Evaluation of bonded layer disorder from thermodynamic behavior of methylaminopropyl groups immobilized on sio2
Authors: Zaitsev V. N. , Oleynik V. D. , Budarin V. L.
Published: March 2011

Thermodynamic characteristics of reaction between proton and methylaminopropyl groups that are covalently bonded to silica gel surface were calculated. First evidence of short‐distance interaction between neighboring bonded amines was obtained. Addition of the first proton does not destroy such interaction. Second proton promotes significant geometry changing.