bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of new polymer architectures by combination of anionic and cationic living polymerization techniques
Authors: Deffieux Alain , Schappacher Michel 
Published: March 2011

AbstractThe 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

AbstractThe 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

AbstractElectron 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

AbstractThe 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

AbstractPoly(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

AbstractAdmittedly 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

AbstractAlkyllithium 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

AbstractSpiro 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

AbstractNew 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

AbstractCombination 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

AbstractAnionic 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

AbstractWe, 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

AbstractPseudoanionic 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

AbstractThe 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

AbstractPhotozymes 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

AbstractSingle 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

AbstractWith 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.
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

AbstractCertain 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

AbstractThe 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

AbstractIn 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

AbstractCo‐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

AbstractPlastics 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.
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

AbstractThermal 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

AbstractThe 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.