bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereospecific polymerization of 1‐olefins and styrene in the presence of homogeneous catalysts
Authors: Zambelli Adolfo , Pellecchia Claudio , Oliva Leone 
Published: March 2011

AbstractThe behaviour of several catalytic systems promoting stereospecific polymerization of α‐olefins is briefly reviewed. Syndiotactic specific polymerization of styrene is also considered and possible structures are tentatively proposed for the syndiotactic specific catalytic complexes.
Recycling of polymeric materials by pyrolysis
Authors: Kaminsky W. 
Published: March 2011

AbstractAs most plastics are produced from oil and as they are discussed to be an environment problem, the recycling of plastic and rubber waste is of increasing importance. A recycling of plastic wastes is costly for mixtures of polymers or even impossible as in the case of composites. Next to combustion only pyrolysis is practicable as a recycling process. Systems for the pyrolysis of plastic waste with complete exclusion of oxygen use melting vessels, rotary kilns or fluidized bed processes. The fluidized bed pyrolysis has turned out to be particularly advantageous. Under the appropriate conditions these processes could be successful on the market.
Configurational and conformational effects in the thermal degradation of poly(vinyl chloride)
Authors: Millán J. , Martínez G. , Jimeno M.L. , Tiemblo P. , Mijangos C. , Gómez‐Elvira J.M. 
Published: March 2011

AbstractA series of works with the aim of clarifying the mechanisms of thermal and photochemical degradation of PVC are reviewed. They include studies on: i) degradation of PVC samples of various tacticities; ii) degradation of PVC after modification by stereoselective nucleophilic substitution; iii) influence of temperature on both kinetics of degradation and polyene distribution in degraded polymer; iv) changes in the highly resolved 13C NMR spectrum as the result of thermal degradation to low degrees; and v) degradation of PVC in blends with polymers of various degrees of compatibility. The results, yet partly unpublished, lead to the conclusion that the very labile structures are some normal local conformations, in particular the GTTG− of the isotactic triad, and allow to confirm some earlier approaches to the PVC mechanisms of degradation.
Interpolymer complexes as new materials for biomedical applications
Authors: Kabanov Victor A. 
Published: March 2011

AbstractPolymer networks which can be “de‐crosslinked” in a controlled way, i.e. at a given moment and under chosen experimental conditions, have a number of potential applications such as temporary protective coatings and erodable bio‐materials. If the de‐crosslinking occurs by scission of bonds which differ from those that form the branching points of the network, soluble star‐shaped polymers are formed, the analysis of which gives information about the functionality of the branching points.
De‐crosslinkable networks
Authors: Goethals E.J. , Trossaert G. , De Vos R. , De Clercq R. 
Published: March 2011

AbstractRecent extensive studies have distinguished a special class of polymers which are able to form thermotropic mesophases despite the absence of mesogenes in their chemical structure [1]. In the most striking form the tendency to form such mesophases is displayed by polymers with flexible inorganic backbone, such as poly(diethylsiloxane)/PDES/. In this presentation recent results concerning mechanical and thermomechanical behaviour of a series of PDES mesophase elastomers are considered. Three types of PDES elastomers were studied: crosslinked samples prepared by peroxide vulcanization [2,3], crosslinked samples vulcanized by a multifunctional siloxane resin [4] and block copolymers with ladder polysilsesquioxane as the hard block and PDES as the soft block [5].
Intermolecular interactions and properties of bulk polymers
Authors: Rutledge Gregory C. , Suter Ulrich W. 
Published: March 2011

AbstractInteraction of molecular self organization and molecular recognition leads to formation of functional supramolecular systems. They combine order and mobility, and their function is based on their organization1. These fascinating phenomena ‐ and the living cell is only the most perfect example ‐ can help to mimic biomembrane processes as well as to develop new synthetic materials.
New synthetic routes towards polyphosphazenes
Authors: Matyjaszewski Krzysztof , Cypryk Marek , Dauth Jochen , Montague Robert , White Michael 
Published: March 2011

AbstractTwo new methods for the synthesis of polyphosphazenes are described. The first is based on the catalyzed polycondensation of phosphoranimines using various catalysts and initiators. Certain mechanistic aspects of this process with reactive intermediates are discussed. Linear polymers are formed quantitatively at temperatures around 100 °C in a few hours (the thermal process requires a few days at 200 °C). The second method is based on the direct reaction between phosphonites and phosphinites with silyl azides. This reaction proceeds by phosphine azide intermediates and provides new polyphosphazenes.
New initiating systems for living cationic polymerization: Design and mechanism
Authors: Sawamoto Mitsuo , Higashimura Toshinobu 
Published: March 2011

AbstractThis paper concerns the recent progress in our search for new initiating systems for living cationic polymerization and the mechanisms involved therein, specifically focusing on:(a) Protonic acid/Lewis acid initiating systems for vinyl ethers;(b) Initiating systems for living cationic polymerization of styrene;(c) Multi‐functional initiating systems.In area (a), the design of counteranions was discussed relative to the principles of living cationic polymerization; in area (b), the first truly living cationic polymerization of styrene is described; and in area (c), the multi‐functional initiating systems led to tri‐armed polymers of vinyl ethers and p‐alkoxystyrenes with amphiphilic arm chains of uniform lengths.
Cationic bulk polymerization of vinyl ethers in the liquid crystalline phase
Authors: Jonsson Haakan , Percec Virgil , Gedde Ulf W. , Hult Anders 
Published: March 2011

AbstractCationic bulk polymerization of liquid crystalline phenyl benzoate and biphenyl vinyl ethers was performed using either thermal or photochemical initiation by onium salts. High molecular mass polymers having narrow molecular mass distribution were produced in high yields at very high temperatures (i.e., ≤ 120°).Seemingly, the polymerization system could stabilize the growing species and thus reduce the amount of chain transfer reactions. Thin films of the monomers were oriented in their liquid crystalline state by the use of conventional ordering techniques used for low molar mass liquid crystals. On subsequent polymerization the orientation was preserved giving liquid crystalline thin films having a very high degree of order.
Synthesis and characterization of poly(alkyl vinyl ether)/poly(ϵ‐caprolactone) diblock copolymers
Authors: Verma A. , Glagola M. , Prasad A. , Marand H. , Riffle J. S. 
Published: March 2011

AbstractThis paper reports the synthesis and characterization of hydroxyl functionalized poly(butyl vinyl ether) oligomers, and block copolymers comprised of poly(butyl vinyl ether) and poly(ϵ‐caprolactone). Using the HI/ZnI2 initiating system in toluene at −20°C, monofunctional poly(butyl vinyl ether) oligomers of predicted molecular weights precisely terminated with aldehyde or primary hydroxyl endgroups have been prepared. Furthermore, the primary hydroxyl end functionality has been utilized to initiate ring opening polymerization of ϵ‐caprolactone in the presence of stannous octanoate as the catalyst. This ring opening reaction provides an entry into new poly[(butyl vinyl ether)‐block‐poly(ϵ‐caprolactone)] copolymers.
Kinetics, mechanisms, and synthesis studies of ring‐opening‐closing alternating copolymerization
Authors: Lundmark Stefan , Kobayashi Shiro 
Published: March 2011

AbstractThe present paper describes the ring‐opening‐closing alternating copolymerization of cyclic phosphonites (2‐phenyl‐1,3,2‐dioxaphosphelane (1a), 2‐phenyl‐1,3,2‐dioxaphosphorinane(1b), 2‐phenyl‐1,3,2‐dioxaphosphepane(1c), and 2‐phenyl‐4H‐1,3,2‐benzodioxa phosphorin‐4‐one(1d)) with muconic acid(2a), succinaldehyde(2b), glutaraldehyde(2c), adipinaldehyde(2d), o‐phthalaldehyde(2e), acrylic anhydride(2f), methacrylic anhydride(2g), N‐methyl diacrylamide(2h), and N‐methyldimethacrylamide(2i). The reaction of a 1:1 monomer feed ratio, explained by a mechanism of propagation via zwitterion intermediates, proceeds without any added catalyst to give an alternating copolymer 3 involving ring‐opening of 1 and ring‐closing of 2. The structure of copolymer 3 was determined by1 H,13 C NMR,31 P NMR and IR spectroscopies as well as elemental analysis.
Pd(0) and Ni(0) catalyzed polymerization reactions
Authors: Percec Virgil , Pugh Coleen , Cramer Edwin , Okita Shigeru , Weiss Robert 
Published: March 2011

AbstractThree novel metal catalyzed cross‐coupling polymerization reactions which result in carbon‐carbon bond formation are described and discussed in context with other metal catalyzed cross‐coupling polymerization reactions. Diarylacetylene monomers and dimers are prepared by the phase transfer Pd(0)/Cu(I) catalyzed coupling of aryl halides with 2‐methyl‐3‐butyn‐2‐ol. Aryl‐alkyl bond forming polymerization reactions are achieved by the phase transfer Pd(0) catalyzed coupling of B‐alkyl‐9‐borabicyclo[3.3.1]nonane derivatives with aryl halides. Soluble polyphenylenes are prepared by the Ni(0) catalyzed homocoupling of substituted phenylenebistriflates in the presence of zinc.
New palladium‐ and nickel‐catalyzed polycondensations for synthesis of carbon‐carbon chain polymers, polyamides, and related condensation polymers
Authors: Imai Yoshio 
Published: March 2011

AbstractThis article reviews our current work on the palladium‐ and nickel‐catalyzed polycondensations for the synthesis of various types of condensation polymers. We succeeded for the first time in the synthesis of carbon‐carbon coupling polymers, that is polycinnamamides, by the palladium‐catalyzed cross‐coupling polycondensation of aromatic diiodides with divinylic compounds. We further developed a new promising method of the synthesis of aramids and related condensation polymers by the palladium‐catalyzed carbonylation polycondensation starting from aromatic dibromides, bifunctional nucleophilic monomers such as aromatic diamines, and carbon monoxide.
Novel platinum initiators for ring‐opening polymerizations
Authors: Crivello James V. , Fan Mingxin 
Published: March 2011

AbstractPlatinum complexes together with compounds containing silicon‐hydrogen bonds comprise a novel class of initiators for the ring‐opening polymerization of a wide variety of heterocyclic compounds including; epoxides, oxetanes and 1,3,5‐trioxane. This paper reports on a preliminary survey of the scope and limitations of these new initiator systems with special emphasis on the ring‐opening polymerization of epoxides. Considerable effort has been directed towards the elucidation of the mechanism of the polymerizations initiated by these systems. The best current evidence suggests that polymerization proceeds by a cationic mechanism. Data is also presented which suggests that platinum metal colloids may function as the active initiating species.
Regioselective ring‐opening polymerizations and hydrosilations catalyzed by transition metals
Authors: Crivello James V. , Fan Mingxin 
Published: March 2011

AbstractOrganometallic rhodium complexes were found to be catalysts for the ring‐opening polymerization of epoxides and other heterocyclic compounds. A cocatalyst, consisting of a compound or polymer containing silicon‐hydrogen bonds is also required. These same catalyst‐cocatalyst mixtures are also highly active for hydrosilation reactions. Rhodium phosphine complexes have been discovered which, while active for hydrosilation, are not catalysts for epoxide polymerizations. These rhodium phosphine complexes permit the synthesis of epoxy‐functional silanes and siloxanes in high yields without competing ring‐opening polymerization.
Mechanisms of the aromatic polyetherification reactions
Authors: Percec Virgil , Wang James H. , Clough Robert S. 
Published: March 2011

AbstractThe mechanisms of aromatic nucleophilic substitutions are briefly reviewed with emphasis on those which have been used for the synthesis of aromatic polyethers and aromatic polythioethers, i.e. the SNAr, the SRN1, and a variant of SRN1 (the SRN1′) mechanisms. The synthesis of poly(ether ketone)s by the SNAr mechanism is discussed in terms of polar versus the single electron transfer (SET) pathways. The synthesis of poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) by the phase transfer catalyzed (PTC) anion‐radical mechanism (i.e. the SRN1′ mechanism) is discussed in comparison with the synthesis of PPE by the conventional radical‐radical mechanism. Various examples of the PTC copolymerization of 4‐bromo‐2,6‐dimethylphenol with a phenol comonomer are provided. These PTC copolymerization experiments led to the synthesis of PPE with well‐defined chain end functionalities and controlled molecular weights. The PTC depolymerization of high molecular weight PPE terminated with a 2,6‐dimethylphenol chain end in the presence of a phenol is discussed. The depolymerization proceeds by an anion‐radical mechanism.
New activating groups for poly(aryl ether) synthesis
Authors: Labadie J. W. , Hedrick J. L. 
Published: March 2011

AbstractWe have investigated new activating groups for poly(aryl ether) synthesis and have demonstrated that quinoxaline, benzazole, amide, and perfluoroalkyl groups activate fluoro‐ and, in some cases, nitro‐displacements from aromatic rings. The quinoxaline‐activated aryl ether synthesis involved activation by the electron deficient pyrazine ring of the 6‐position on the fused benzo ring. Thiophenoxides displaced 6‐chloro and 6‐nitro groups from quinoxalines under milder conditions than required for the ether synthesis. Pendent benzoxazole, benzothiazole, and amide groups activated displacement of a para fluoro group in high yield and selectivity. Perfluoroalkyl groups activated 2‐ and 4‐fluoro or nitro groups towards displacement, presumably by stabilization of the transition state through hyperconjugation. The new transformations were utilized for the synthesis of high molecular weight heterocyclic, amide and perfluoroalkyl‐based poly(aryl ethers). The resulting polymers were amorphous and displayed distinct glass transition temperatures, as well as improved solution and melt processability.
Synthesis of aromatic polyethers by cation‐radical polymerization
Authors: Percec Virgil , Wang James H. 
Published: March 2011

AbstractThis paper discusses the synthesis of aromatic polyethers including poly(ether sulfone)s, poly(ether ether ketone)s, fully aromatic polyethers and polyarylenes by the cation‐radical polymerization (Scholl reaction) of bisaryl monomers. The polymerizability of various monomers is discussed with respect to the effects of the monomer structure on the reactivity of both the monomers and of the cation‐radical growing species. Examples are provided for the synthesis of polymers of unique structure by the cation‐radical polymerization reactions. The cation‐radical polymerization reactions have been studied under a variety of experimental conditions. The oxidants used as initiators include various Lewis acids and their combinations such as FeCl3, AlCl3/CuCl2, AlCl3/CuCl/O2, AlCl3/FeCl3, FeCl3:tris(3,6‐dioxaheptyl)amine complex, and organic electron‐acceptor compounds such as 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ). This polymerization proceeds in electrophilic solvents such as nitrobenzene, methylene chloride, etc. The cation‐radical polymerization initiated by a catalytic amount of oxidant is demonstrated by using vanadyl acetylacetonate as oxidant. An example in which the polymerization proceeds by both a cation‐radical reaction and an electrophilic transalkylation reaction is provided by the polymerization of 2,2‐bis[4‐(1‐naphthoxy)phenyl]propane initiated with FeCl3.
Polyphthalazines and polyisoquinolines with rigid‐rod‐like structures
Authors: Singh Rina , Hay Allan S. 
Published: March 2011

AbstractThe synthesis of new classes of N‐heterocyclic polymers, the polyisoquinolines and polyphthalazines are described from intramolecular ring closure reactions of a novel aromatic polyketone. The polyketone was synthesized by the nickel‐catalyzed coupling reaction of 1,2‐bis(4‐chlorobenzoyl)‐3,6‐diphenylbenzene. The thermal and mechanical properties of the N‐heterocyclics synthesized from the polyketone are compared to analogous N‐heterocyclics containing flexible linkages synthesized from poly(ether ketone)s containing ortho‐dibenzoylbenzene moieties.
Polycondensation of silylated monomers
Authors: Kricheldorf Hans R. 
Published: March 2011

AbstractVarious polycondensations of silylated aromatic monomers, such as aminophenols, diphenols, hydroxy acids, dicarboxylic acids or acetoxybenzoic acids are reported. Reaction mechanisms and preparative usefulness of their polycondensations are discussed. In this connection also structure/property relationships of aromatic polyethers, liquid‐crystalline polyesters and poly‐(ester‐anhydride)s are mentioned.
New step growth polymers via reissert compound chemistry
Authors: Gibson Harry W. , Pandya Ashish , Rasco Melvin L. , Guilani Bardia , Hermann Christine K. F. , Leblanc Jean‐Pierre , Jois Yajnanarayana H. R. 
Published: March 2011

AbstractReissert compounds are the result of the formal addition of acyl cyanides across the CH=N bonds of aromatic heterocyclic compounds or acyclic imines. The chemistry of this class of compounds is primarily based upon the acidity of the CH(CN)‐NCOR moiety and the nucleophilic reactivity of the conjugate base. Three methodologies for application of this chemistry to the synthesis of polymers are summarized: 1) formation of polyamides by the “Reissert reaction” of suitable difunctional imines and diacid chlorides, 2) condensation of the anions of difunctional Reissert compounds with dielectrophiles such as dihaloalkanes and dialdehydes and 3) use of Reissert compound chemistry to construct novel monomers for use in traditional condensation polymerizations. All three methodologies are proven to be effective in the production of nitrogen containing polymers.
Poly(enaminonitriles) containing biphenyl and terphenyl units in the main chain
Authors: Moore J. A. , Kim Sang Youl 
Published: March 2011

AbstractTwo new monomers, 4,4′‐bis(1‐chloro‐2,2‐dicyanovinyl)biphenyl and 4,4″‐bis(1‐chloro‐2,2‐dicyanovinyl)‐p‐terphenyl, have been synthesized and polymerized with several diamines by vinylic nucleophilic substitution producing poly(enaminonitriles) with molecular weight varying from low to moderately high, depending on the diamines used. The polymers were soluble in polar, aprotic solvents before thermal curing, but became insoluble at high temperatures without the evolution of volatile byproducts. These new polymers exhibit excellent thermal stability, particularly when they contain para‐linked aromatic rings. Dielectric measurements of some of the polymers revealed dielectric constants of at least 4.
Self‐assembling synthetic supramolecular polymers
Authors: Ashton Peter R. , Philp Douglas , Spencer Neil , Stoddart J. Fraser 
Published: March 2011

AbstractThe solid state structure of a [2]catenane, composed of macrocyclic rings containing π‐electron rich hydroquinol rings and π‐electron deficient bipyridinium units has revealed an approach to the elaboration of supramolecular polymers with a double helical tertiary structure. Neutral molecules containing up to five hydroquinol rings, separated by trioxaundecane spacers and terminated by benzyl ether functions, have been shown by 1H NMR spectroscopy to form superstructures with possible double helical character as a result of π‐π stacking and other non‐covalent bonding interactions with polycations containing up to four bipyridinium units separated by p‐xylyl spacers and terminated also by benzyl functions.
Design of novel structurally defined ladder‐type polymers
Authors: Fahnenstich U. , Koch K.‐H. , Pollmann M. , Scherf U. , Wagner M. , Wegener S. , Müllen K. 
Published: March 2011

AbstractTwo different approaches for the synthesis of structurally defined ladder‐type polymers are described. Repetitive Diels‐Alder reaction as well as polymer analogous cyclization of suitable open‐chain precursors are used for generating novel band‐type structures. Polymeric [2.2]‐cyclophanes and ethene‐bridged polyacene precursors are prepared via [4 + 2] cycloaddition reactions. Ladder‐type poly(p‐phenylene) and oligo(perinaphthylenes) as planar π‐systems are obtained by Friedel‐Crafts‐ rsp. by alkali‐metal induced electrocyclic ring‐closure reactions.
Hypercrosslinked rigid‐rod polymers
Authors: Webster O. W. , Gentry F. P. , Farlee R. D. , Smart B. E. 
Published: March 2011

AbstractIn a search for new types of polymer architecture, we have examined systems where one couples rigid‐rod monomers with multifunctional tie‐point monomers. High surface area (400–1000 m2/g) polymeric carbinols result from reaction of 4,4′‐dilithiobiphenyl, as well as other multi‐lithiated aromatic compounds with dimethyl carbonate.
Polymers tailored for redox‐ and photoactivity
Authors: Bartz Thomas , Böhm Arno , Klapper Markus , Müllen Klaus , Weitzel Hans‐Peter 
Published: March 2011

AbstractThe synthesis of polymers tailored for a specific redox‐ and photoactivity is described.The title compounds can generally be depicted as consisting of electrophoric or chromophoric building blocks which are linked by variable bridging groups.Their properties depend on the nature of both units in the polymer chain. The bridging group between the electrophoric units can be saturated or conjugated and can be incorporated directly upon polymer formation. However, in other polymers such bridging groups are already present, which allow one to switch between an unsaturated and saturated linking.With the “reductive polymerization”, a new method to link e.g. anthracene and isopyrene units is proposed. A Heck‐type reaction and the boronic acid coupling according to Suzuki are used for generating conjugated polymers.In the case of polymers containing 2,2′‐distyrylbiphenyl units it is possible to interrupt π‐conjugation via electron‐transfer or UV‐irradiation. With a thermal ring‐opening reaction of cyclobutene units, a method is shown to create conjugation between π‐systems. By hydrogen elimination in a polymethide structure highly conjugated polymers can be created.
Enzymatic polymerization: The first in vitro synthesis of cellulose via nonbiosynthetic path catalyzed by cellulase
Authors: Kobayashi Shiro , Kashiwa Keita , Shimada Junji , Kawasaki Tatsuya , Shoda Shin‐ichiro 
Published: March 2011

AbstractThe in vitro synthesis of cellulose via a nonbiosynthetic path has been achieved for the first time by condensation of β‐D‐cellobiosyl fluoride as substrate for cellulase in a mixed solvent of acetonitrile/acetate buffer (pH 5,5:1) (enzymatic polymerization). Under reaction condition of a higher substrate concentration or higher acetonitrile concentration, cellooligosaccharides were produced predominantly. The present method of using a glycosyl fluoride as substrate for a hydrolytic enzyme in an organic/water mixed solvent has successfully been applied to synthesis of maltooligosaccharides and unnatural oligosaccharides.