bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular and mechanistic aspects of the functionalization of polyolefins with ester groups
Authors: Ciardelli Francesco , Aglietto Mauro , Passaglia Elisa , Ruggeri Giacomo 
Published: March 2011

AbstractIn the present paper the functionalization reaction of polyolefins in the melt with diethylmaleate (DEM) in the presence of peroxide is revisited. The process was analyzed on the basis of several experiments carried out in the Brabender mixer with 30 min residence time and at constant temperature, 190° C for EPR and 200° C for LLDPE samples, while varying the number of branching in the starting polyolefin, the amount of DEM and of dicumyl peroxide (DCP). For reference purposes similar experiments were also examined as performed with EPDM and isotactic polypropylene (PP).At the end of the reaction, the polymeric product was treated with boiling acetone to remove low molecular weight products. In general, the acetone insoluble polymer was soluble in heptane and the functionalization degree (FD) referred to this fraction was in the range 0.2–2.0% mol of DES groups per 100 moles of monomelic units.The contemporary occurrence of the degradation and chain extension, including crosslinking reactions, provides a reasonable explanation of the results obtained. The analysis of the process performed in the present work helps to select proper conditions for controlling the characteristics and FD of the polyolefin and keep undesired secondary reactions under control.
Developments in the synthesis of maleated polyolefins by reactive extrusion
Authors: Bray Tracey , Damiris Sam , Grace Andrew , Moad Graeme , O'Shea Michael , Rizzardo Ezio , van Diepen Gary 
Published: March 2011

AbstractThe maleation of conventional and metallocene linear low density polyethylenes by reactive extrusion has been explored with a view to defining the conditions necessary for a robust process that provides both high grafting efficiencies (>80%) and minimal degradation or cross‐linking. The dependence of grafting efficiency on various operating parameters (maleic anhydride level, maleic anhydride:initiator ratio, throughput rate, direction of screw rotation, temperature) has been established. Literature methods for characterization of the grafted product based on FTIR or 1H NMR analysis have been critically examined with respect to their ability to distinguish between single unit and oligomeric maleic anhydride grafts and found to yield ambiguous results.
13C NMR Study of the grafting of 13C labeled maleic anhydride onto PE, PP and EPM
Authors: Heinen Wouter , van Duin Martin , Rosenmöller Carola H. , Wenzel Cornelia B. , De Groot Huub J.M. , Lugtenburg Johan 
Published: March 2011

AbstractThe chemical structure of polyolefins grafted with maleic anhydride (MA) has been the subject of much speculation, but thorough experimental studies are rare. MA with 99% 13C in the double bond was synthesized and grafted onto PE, EPM and PP in the melt and solution. 1D INADEQUATE 13C NMR spectroscopy was used to characterize the products. Saturated, monomeric MA graft structures are formed. Only for grafted PE short MA oligomers are demonstrated. Grafting occurs on secondary and tertiary carbons depending on the composition of the polyolefin. For PP a new, unsaturated MA graft structure on the polymer chain terminus is identified. All graft structures are rationalized using a simple grafting mechanism.
Macromolecule — Metal complexes based on salts of unsaturated mono‐ and dicarboxylic acids: Synthesis and characterization
Authors: Dzhardimalieva Gulzhian I. , Pomogailo Anatolii D. 
Published: March 2011

AbstractThe radical polymerization and copolymerization of salts of unsaturated carboxylic acids were used for the production of metal‐containing polymers. The kinetic peculiarities and copolymerization parameters were estimated. The synthesis and structure of transition metal acrylates, maleates, fumarates, and itaconates are discussed. The influence of the metal atom on salt reactivities and reaction rates is observed.
(Co)polymerization of metal‐containing monomers as a way of MMC synthesis
Authors: Pomogailo Anatolii D. 
Published: March 2011

AbstractThe principal advances and problems of the synthesis, of poly‐, co‐ and graft‐ polymerization of metal‐containing monomers (MCM) are analysed. The MCMs are classified on the type of the metal bond with the organic part of the molecule, viz. MCM with σ‐, nv‐, and π‐bonds. The effect of a transition metal on both the polymerization and on the properties of the products formed is of special interest. The basic fields of application of metal‐containing polymers have been summed up.
Addition — Fragmentation type initiators for cationic polymerization
Authors: Yaǧci Yusuf , Reetz Ivo 
Published: March 2011

AbstractAddition — fragmentation reactions are a versatile and exceptionally interesting tool in preparative polymer chemistry. With the aid of specially designed allyl‐onium salts (addition — fragmentation agent, AFA) in conjunction with conventional radical initiators it is possible to very efficiently initiate cationic polymerizations. The mechanism involves (a) the formation of radicals by heating or irradiating the radical initiator, (b) the addition of these radicals to an AFA molecule and (c) the fragmentation of the AFA. In step (c) radical cations are produced, which with high rates initiate the polymerization of cationically polymerizable monomers (e.g., cyclohexene oxide, CHO). In order to show good performance in initiation reactions, AFAs have to be equipped with functional groups or substituents which either promote radical addition or facilitate the fragmentation of reaction intermediates.
Anionic polymerization and copolymerization of macromonomers: Kinetics, structure control
Authors: Ederle Y. , Isel F. , Grutke S. , Lutz P. J. 
Published: March 2011

AbstractThe present paper discusses the ability of macromonomers to undergo polymerization and copolymerization with acrylic and vinylic monomers. These macromonomers have been synthesized by classical deactivation reactions. Special interest was devoted to macromonomers fitted with polymerizable methylmethacrylate end‐groups. The anionic homopolymerization of ω‐methacryloyloxy‐polystyrene macromonomers was studied in detail and the influence of the molar mass of the macromonomer on the apparent propagation constant was determined. The anionic homopolymerization of ω‐methacryloyloxy poly(ethylene oxide) macro‐monomers was also examined. In both cases, lithium chloride has to be added in order to reach a better control of the reaction. The dilute solution properties of these polystyrene polymacromonomers have been studied. Some preliminary attempts to apply that anionic homopolymerization of macromonomers to the preparation of “dumbbell” and “palmtree” polymers were presented.
Preparation of uniform stereoregular polymer, stereoblock polymer and copolymer of methacrylate, and their stereocomplex formation
Authors: Hatada Koichi , Kitayama Tatsuki , Ute Koichi , Nishiura Takafumi 
Published: March 2011

AbstractIsotactic (it‐) and syndiotactic (st‐) uniform poly(methyl methacrylate)s (PMMAs) were prepared by stereospecific living polymerizations followed by supercritical fluid chromatographic separation. The it‐and st‐uniform PMMAs were used to study the mechanism of stereo‐complex formation in solution with the aid of gel permeation chromatography and 1H NMR spectroscopy. The it‐ and st‐uniform PMMAs with hydroxy end‐group were prepared and reacted with sebacoyl dichloride to form uniform stereoblock PMMA. The stereoblock PMMA was found to form intra‐ and intermolecular stereocomplexes in acetone. A uniform stereoblock copolymer, it‐PMMA‐block‐st‐poly(ethyl methacrylate), was prepared and its stereocomplex formation was also studied.
Ionic polymerization in aqueous emulsion
Authors: De Gunzbourg Anémone , Maisonnier Sylvette , Favier Jean‐Claude , Maitre Catherine , Masure Michèle , Hémery Patrick 
Published: March 2011

AbstractA kinetic study of the anionic polymerization of octamethylcyclotetrasiloxane (D4) in aqueous emulsion has been carried out in the presence of ionic additives. The rate of polymerization of several cyclosiloxanes has been compared, leading to additional evidence for an interfacial mechanism of polymerization. The emulsion process has been applied to the cationic polymerization of D4 and of tetramethylcyclotetrasiloxane (DH4) initiated by dodecylbenzenesulfonic acid. Very efficient for the synthesis of linear polymethylhydrogenosiloxanes (PMHS), these conditions did not seem suitable for the polymerization of D4. The extension of the process to other heterocyclic monomers is discussed through the anionic polymerization of phenylglycidylether.
New adventures with divalent carbon intermediates
Authors: Marchand Alan P. , Rajagopal D. , Kumar Kaipenchery A. , Eckrich Ralf , Ramanaiah K. C. V. , Namboothiri I. N. N. , Alihodžić Sulejman , Dong Eric Zhiming , Shukla Rajesh , Bott Simon G. , Mlostoń Grzegorz , Galindo Alberto , Bartnik Romuald 
Published: March 2011

AbstractPart I: Reactions of 3‐substituted 1‐azabicyclo[1.1.0]butanes (1a and 1b) with dichlorocarbene proceed in each case via nitrogen ylide intermediates with concomitant ring opening to afford the corresponding dihaloimines (2a and 2b, respectively). Part II: Vinylidènecarbene‐cycloalkyne equilibria have been studied in three polycarbocyclic systems, i.e., 10a‐10b, 20a‐20b, and 27a‐27b. In all three systems, only the vinylidenecarbene intermediate can be trapped in situ by cyclohexene. The results of site‐specific 13C labeling studies that employ 9‐C(8)‐13CBr2 (enriched with 4 atom‐% 13C), 19‐C(4)‐13CBr2 (enriched with 5 atom‐% 13C), and 23‐C(4)‐13CBr2 (enriched with 10 atom‐% 13C) also support this conclusion and suggest that cycloalkyne intermediates, if formed in these systems, must rearrange very rapidly to the corresponding (thermodynamically favored) vinylidenecarbenes. Part III: Base‐promoted reactions of N‐tosyl‐ and N‐benzhydrylazetidin‐3‐ones (i.e., 30a and 30b, respectively) with diethyl diazomethylphosphonate (DAMP), when performed in the presence of cyclohexene, in each case afford exclusively the product that results via in situ trapping of the corresponding vinylidenecarbene.
Inner sphere and outer sphere electron transfer reactions in atom transfer radical polymerization
Authors: Matyjaszewski Krzysztof 
Published: March 2011

AbstractThe participation of electron transfer (ET) processes in atom transfer radical polymerization (ATRP) is discussed. Inner sphere electron transfer process (atom transfer) is the inherent part of ATRP. It includes the homolytic cleavage of C‐halogen bond in dormant macromolecular alkyl halides species by the Cu(I) activator with the rate constant kact≈︁100±1 M−1s−1. This process is reversible and the deactivation of growing radicals by X‐Cu(II) species is very fast with the rate constant of deactivation kact≈︁107±1 M−1s−1. However, in addition to the atom transfer process (inner sphere ET), outer sphere ET may also occur. Growing radicals can either be oxidized by Cu(II) species to carbocations or reduced by Cu(I) species to carbanions. These reactions were observed in the polymerization of p‐methoxystyrene and initiation with 2‐bromomalonates, respectively. In order to avoid these side reactions the catalyst structure should be fine tuned for the particular monomer and the range of targeted molecular weights. In addition, some side reactions can be avoided by slow addition of initiator (e.g. for benzhydryl halides), catalyst (for malonates and CCl4 as initiators) and by reducing polymerization temperature.
„Bonding”︁ electropolymerization: A new electron‐transfer strategy for the tailoring of performant polymer‐based composites
Authors: Baute Noëlle , Calberg Cédric , Dubois Philippe , Jérǒme Christine , Jérdme Robert , Martinot Lucien , Mertens Marc , Teyssié Philippe 
Published: March 2011

AbstractCareful control of experimental conditions in the cathodic electropolymerization of acrylonitrile allows the grafting of thin polymer films, on conducting surfaces offering electrons easily mobilized at a relatively low potential. Matching relative polarity and donicity of solvent and monomer expands the applicability of this methodology to the whole class of (meth)acrylic monomers, paving the way to many new and useful multiphase materials
Recycling technology of poly(ethylene terephthalate) materials
Authors: Lin Chen Chong 
Published: March 2011

AbstractPoly(ethylene terephthalate) (PET) has become one of major post consumer plastics wastes, in addition to polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly(vinyl chloride) (PVC). The challenge to large‐volume plastics companies is to learn how to collect, separate, reprocess and market their low‐cost products and make a profit, too. The effort of PET recycling, however, is the most successful story in the plastic recycling technology, including both reclaim and upgrade of PET waste. Beverage bottles made of PET are recycled more than 20% of the total production. The technology of today can reclaim the post‐consumer PET bottles to produce high‐quality granulated PET with better than 99% purity. A practical reclaim process for recycling PET bottles (including bottle, HDPE base cup, aluminum cap, liner, label and adhesive) is available by the Center for Plastics Recycling Research in USA. PET recycling process, like for other plastics, can be divided into three categories: incineration, physical recycling, and chemical recycling. To make the plastic recycling business pay requires more than simple recovery and marketing. Greatest profit potential is in upgraded and value‐added reclaim products. Upgrading involves compounding with additives to make material more processable, adding reinforcement, or producing extrusions or finished parts from reclaim resins. For instance, a modified injection‐moldable resin made from PET bottle scrap is claimed to provide high impact and processability at less cost than competitive materials. It is foreseen that chemical recycling of waste PET bottle becomes feasible if the price of raw material goes up. Three economical processes are involved in this technology: pyrolysis, hydrocracking, and hydrolysis. The hydrolysis process is presently employed to recover the raw material for unsaturated polyester resin manufacture or polyols for the production of polyurethane resin. It is reported in this presentation that polymer concrete could be a huge potential market for chemical reclaim of PET materials, especially for green or mixed‐color PET, which are priced lower than colorless PET reclaim materials.
New trends in chemical recycling of poly(ethylene terephthalate)
Authors: Spychaj Tadeusz , Paszun Daniel 
Published: March 2011

AbstractChemical recycling of poly(ethylene terephthalate) (PET) by nonconventional transesterification and ammonolysis/aminolysis methods are discussed on the basis of literature and own experimental data. The obtained products of deep PET degradation using allylamine (N,N′‐diallylterephthaldiamide), triethanolamine and other alkanolamines were prepared and characterized by DSC and elemental analysis.
The role of additives in the recycling of polymers
Authors: La Mantia Francesco Paolo 
Published: March 2011

AbstractThe main problems in post‐consumer plastics recycling are due to the degradation undergone by the polymers during processing steps and by the products during their lifetime and, for heterogeneous recycling, to the incompatibility of different polymers. To reduce the negative effects of the recycling steps, two main ways can be adopted for homogeneous materials: restabilization during the recycling to avoid or at least to slow the degradation and addition of fillers and modifiers capable of improving the performance of thermoplastic polymers without increasing the final cost of the secondary material. In the case of mixed plastics, compatibilization is the necessary step to obtain secondary materials with acceptable properties.
The influence of recycling on the properties of wood fibre — Plastic composites
Authors: Balatinecz John J. , Sain Mohini M. 
Published: March 2011

AbstractThe manufacture of composites offers the greatest flexibility to convert and utilize waste plastics, paper and wood into high‐value products. This paper reports on two studies regarding the recycling of these materials. In one study, recycling was simulated by regrinding and injection‐moulding composites of polypropylene (PP), polyethylene (PE) and old newsprint (ONP) eight times. The results indicated that reprocessing had only minor deleterious effect on the mechanical properties (tensile and flexural). The viscosity of neat PP decreased with repeated recycling indicating some thermo‐oxidative degradation. The overall rheological character of PP composites did not change much. PE composites, on the other hand, showed increasing melt flow with reprocessing. The second study examined the effects of various coupling agents on the properties of multicomponent PP composites. Maleated polypropylene (MAPP) was the most effective coupling agent.
Polyelectrolytes bearing azobenzenes for the functionalization of multilayers
Authors: Fischer Peter , Laschewsky André , Wischerhoff Erik , Arys Xavier , Jonas Alain , Legras Roger 
Published: March 2011

AbstractThin polymeric films are assembled by the alternating adsorption of oppositely charged polyelectrolytes. The polyions are functionalized by azobenzenes, typically carrying donor‐acceptor substituents. The azobenzene chromophores are exploited as versatile analytical tools, to study the assembling process, and to control the film quality. A high concentration of ionic groups does not seem to be advantageous per se for good film growth, but rather the matching of the charge densities of the polyelectrolyte pair used seems to be important. Also, the influence of the strongly interacting, form‐anisotropic character of the azobenzenes on the internal film structure was investigated. Although even high concentrations of azobenzenes and of other mesogens do not induce particular ordering, a few polymer pairs allowed the construction of real multilayer films, exhibiting e.g. Bragg peaks.
Molecular hybrids of azobenzene polymer and liquid crystal molecule. A new approach for understanding the command surface system
Authors: Ubukata Takashi , Seki Takahiro , Ichimura Kunihiro 
Published: March 2011

AbstractLangmuir‐Blodgett (LB) films consisting of the hybrid of a polymer having the azobenzene (Az) side chain and 4î‐pentyl‐4‐cyanobiphenyl (5CB) are prepared. Microscopic observations and spectroscopic data both indicate that the Az side chain and 5CB are homogeneously mixed at a molecular level without phase separation in the layer. This provides a satisfactory model of the command surface system. Time course accumulation of spectroscopic data for multilayered hybrid films reveals the cooperative nature of the photo‐motivated molecular motions.
Physical processes in azobenzene polymers on irradiation with polarized light
Authors: Holme N. C. R. , Nikolova L. , Norris T. B. , Hvilsted S. , Pedersen M. , Berg R. H. , Rasmussen P. H. , Ramanujam P. S. 
Published: March 2011

AbstractAzobenzenes can serve as model compounds for the study of transcis isomerization in more complex molecules. We have performed time‐resolved spectroscopy in solutions containing free azobenzene chromophores and diols with a view to obtaining the energy levels and lifetimes of the excited states. A transition route based on experimental results for the theoretically calculated energy level scheme is proposed. Physical observations of surface relief in thin films of azobenzene polymers when irradiated with polarized light are reported. These include two beam polarization holographic observations and single beam transmission measurements through a mask, followed by atomic force microscope and profiler investigations. It is concluded that none of the prevalent theories can explain all the observed facts.
Water vapor sorption and diffusion in glassy polymers
Authors: Paul D. R. 
Published: March 2011

AbstractBy establishing relationships between polymer structure and gas permeation behavior, significant advances have been made in designing materials for membrane separation of gas mixtures. However, the situation is not so well understood when water vapor is one of the components since water molecules may interact with the polymer (plasticization) or each other (clustering) in ways that complicate the structure‐property relationships. In addition, accurate measurement of water sorption, diffusion, and permeation is more complicated than for gases because of the unique hydrogen bonding capability of water, e.g., its tendency to strongly adsorb on high‐energy surfaces and high heat of vaporization. A progress report on a broad program to understand water sorption and diffusion in glassy polymers that may be of interest for membrane applications is outlined; specific strategies include studies of structurally related polymers and miscible blends of hydrophobic/hydrophilic polymer pairs.
The surface tension of polymer liquids
Authors: Dee Gregory T. , Sauer Bryan B. 
Published: March 2011

AbstractA brief review of the surface tension of polymer liquids is presented. A strong emphasis is placed on recent measurements of surface tensions of homologous liquid series up to high‐molecular‐weight polymers, and the thermodynamic liquid properties of these same homologous series obtained from sources such as pressure‐volume‐temperature (PVT) data. The accuracy and limitations of the thermodynamic information which are used as input to many of the theories applied to the surface properties of polymer molecules are discussed. By scaling the surface tension data using a true measure of the cohesive energy density of the liquid state, we can clearly observe the entropic contribution to the surface tension caused by the conformational restriction of a large molecule at the liquid‐vapor interface. The scaling implies the existence of a corresponding states principle for both polymer liquids and for low‐molecular‐weight liquids. The ramifications of the existence of a corresponding states principle for the surface tension of polymer melts are discussed. One consequence of the corresponding states principle is that it allows us to use surface tension measurements to compute the cohesive energy density of polymer melts using PVT data.
X‐ray and molecular modeling studies on the structure‐function correlations of polysaccharides
Authors: Chandrasekaran Rengaswami 
Published: March 2011

AbstractX‐Ray fiber diffraction analysis and computer molecular modeling have revealed the three‐dimensional structures of several important industrially useful polysaccharides such as algin, carrageenan, galactomannan, gellan, pectin, welan, xanthan and xanthan:guaran complex. Consistent with their chemical structures, their molecular morphologies, which include single and double helices, are quite distinct. The helix‐helix associations are promoted by cations and/or water molecules and the patterns are not always the same. The polymer‐dependent structural details can be correlated with, and used to understand the molecular basis of, the observed physical properties.