bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of components in the poly(vinyl chloride) pilled in polymerization stage
Authors: Yushkova S.M. , Tager A.A. 
Published: March 2011

AbstractThe enthalpies of the interaction between PVC or its copolymers and different fillers introduced into the polymerization mass were estimated by the microcalorimetric techniques. For highly filled compounds, the strength of the polymer ‐ filler interaction depends on the chemical nature of both components. The determination of the interaction enthalpy makes it possible to choose a polymeric cover providing for the best interaction and to calculate the lowest amount of the polymer covering entirely the filler surface.
The structure of the poly(vinyl chloride) chain. I. Conformation of 2,4‐dichloropentane
Authors: Burda J. , Lukáš R. 
Published: March 2011

AbstractUsing semiempirical quantum chemical CNDO/2 and MNDO methods, hindered rotations of the carbon chain of 2,4‐dichloropentane stereoisomers were studied. The results obtained confirm the experimental finding that the most important structures of the racemic and meso form of 2,4‐dichloropentane are TT‐racemo (TT‐syndio), GG‐racemo (GG‐syndio) and TG‐meso (TG‐iso) conformers. A more detailed analysis of non‐bonding interactions showed, however, that the energetically most advantageous structures are the partly geometrically shifted TT‐syndio and TG‐iso conformers. In the case of the TT‐syndio conformation MNDO predicts a rotation of the carbon chain by 13.254°, which for the poly(vinyl chloride) chain explains the helical structure of syndiotactic sequences.
Emulsion polymerization of vinyl chloride, potassium persulfate decomposition
Authors: Georgescu Cecilia‐Speranţa , Butucea Victor , Sarbu Adrians , Ionescu Adrians , Deaconescu Ion , Hagiopol Cornel 
Published: March 2011

AbstractDecomposition of potassium persulfate in sodium dodecyl sulfate solutions (of concentrations under and above CMC) and in the presence of poly(vinyl chloride) and vinyl chloride was studied. The decomposition rate has a maximum close to the CMC value of the final solutions. On the basis of experimental data a hemolytic mechanism in which a radical derived from dodecyl sulfate participates is proposed.
Dynamic ‐ mechanical properties of poly(oxypropylene)di‐amine‐diepoxide and poly(oxypropylene)triamine‐diepoxide networks and their relationship to the structure of elastically active network chains
Authors: Ilavský Michal , Hrouz Jaroslav , Šomvársky Ján , Dušek Karel 
Published: March 2011

AbstractThe effect of the initial mole ratio of reactive components on the shape and position of dynamic mechanical functions in the main transition and rubbery region was investigated for two series of networks made from poly(oxypropylene)diamine (D‐400)‐diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)‐triamine (T‐403)‐DGEBA. The networks were prepared with an excess of amine groups up to the highest conversion of epoxy groups; the ratio rH = 2 [ NH2 ]0/ [E]0 ranged from unity to 2,1 for networks from D‐400 and from unity to 3,5 for networks from T‐403. By using the theory of branching processes, structural parameters of these networks were calculated, in particular, the molecular weights of elastically active network chains (EANC's) including dangling chains, of backbone EANC's and of dangling chains. A comparison between theory and experiment led to the following conclusions: (a) the mechanical behaviour in the rubberlike region can be described either by using an affine deformation model (front factor A = 1), or by means of a phantom model (A = (fe‐2)/fe, fe being functionality of the crosslink) with the contribution of permanent interchain interactions; (b) the temperature and frequency position of viscoelastic functions in the main transition region is conclusively affected by the concentration of EANC's; (c) the shape of visco‐elastic functions, especially of retardation spectra in the main transition and rubbery region, depends on the detailed structure of EANC's, but it cannot be decided from the result which structural parameter has the strongest effect on the shape of the functions.
Calculation of network parameters of crosslinked markovian polymer chains
Authors: Miller Douglas R. 
Published: March 2011

AbstractLinear copolymer chains form in a chain‐addition reaction which includes initiation, homopropagation, crosspropagation, and termination by transfer, disproportionation, and combination. Chain growth obeys the Markov property. Multiple types of monomeric units are involved; some types have reactive sites, others do not. These chains are then crosslinked by a small monomer crosslinker which may have a polydispersed distribution of functionality and mass. The resulting network consists of soluble, pendant, and elastically effective fractions. Using classical Markov chain analysis techniques, various statistical properties of the polymer chains are computed. The gel point, weight fractions and other network properties can then be calculated. The effects of unequal rates of chain homopropagation and crosspropagation can be observed.
Siloxane network structures: Kinetics of gelation observed using nuclear magnetic resonance
Authors: Girard O. , Guillermo A. , Cohen‐Addad J. P. 
Published: March 2011

AbstractTransverse nuclear magnetization properties of protons are investigated during the gelation of short poly(dimethylsiloxane) chains. Both the kinetics of the reaction and the amount of the gel fraction are characterized. The sol and gel fractions are distinguished “in situ” during the whole process by performing pseudo‐solid spin‐echoes and through a simple analysis of the relaxation shape.
Synthesis and properties of model ‐ micronetworks
Authors: Antonietti Markus , Bremser Wolfgang , Fölsch Karl J. , Sillescu Hans 
Published: March 2011

AbstractMicrogels are small network particles with overall dimensions in the 100nm‐region. Some experiments concerning the behaviour of cross‐linked matter can be more easily performed using the molecular nature of μ‐gels. In this publication, the synthesis and characterization by light and neutron scattering and dynamic‐mechanical shear experiments of two different types of μ‐gels are presented.
Showing a rheological effect of gelation on epoxy‐amine systems
Authors: Senhaji A. C. , Harran D. 
Published: March 2011

AbstractThe effect of gelation was studied on the rheological curves, during hardening of a resin subjected to sinusoidal shearing between parallel plates. The epoxy‐amine system was chosen for the moderate value of its maximum glass transition temperature Tg, ∞ which means that it is possible to avoid vitrification by operating at T > Tg, ∞. The shape of the variation curve of the storage modulus G' does not depend on temperature; G' obeys a single percolation law as a function of the reduced variable t/tgel. On the other hand, gelation leads to a fall in the growth rate of the loss modulus G” after the gel point. This effect increases with temperature and can become considerable at very high temperatures: in this case a minimum of G” between the gel point and the rubbery plateau can be observed. We have verified that this effect is indeed a rheological effect of gelation as it begins practically at the gel point determined on the storage modulus curves. Several qualitative conclusions are drawn, and the nature of this effect is discussed.
An alternative approach to rubber elasticity theory based on a lattice model
Authors: Schwarz Jürgen 
Published: March 2011

AbstractAn alternative rubber elasticity theory for bulk elastomers has been developed. It is based on the model of a cubic lattice which is filled completely with long flexible chains. The dependence of the configurational entropy on the orientation factor of Hermans has been derived for a uniaxial homogeneous orientation of the system. With the assumption of a constant stress‐optical coefficient, the dependence of the true stress Γ on the deformation λ = L/L0, with L the length of the sample, can be described approximately as τ ∝︁ in λ both for uniaxial extension and compression, which agrees quite well with experimental results on bulk elastomers.
Modelling and simulation of synthesis, microstructure and properties of emulsion copolymers
Authors: Guillot J. 
Published: March 2011

AbstractAccurate investigations of batch homopolymerization and copolymerization allow to derive mechanisms for emulsion polymerization; if they are not actually general, they are assumed to be valid for a given co‐monomer system, at least. A lot of approaches have been devoted to the mathematical modelling of emulsion polymerization, with the objective to take into account all of the experimental parameters or only some of them. Many of these approaches are quite complex and assume that a huge number of parameters are known.
Excited state processes in photoinitiators of polymerization in microheterogeneous media
Authors: Lougnot Daniel‐Joseph , Fouassier Jean‐Pierre 
Published: March 2011

AbstractA comprehensive investigation of the photopolymerization in microheterogeneous structure is carried out with a view to elucidate the role played by the excited states in the initiation process.The radical initiation of methyl methacrylate in either anionic or cationic micelles or of acrylamide in reverse microemulsion is thus examined by UV spectroscopy, steady state photolysis and time resolved laser spectroscopy. The question of the localization of the initiator is dealt with special attention. Moreover, the influence of several parameters is also considered (concentration of reactants, incident light intensity, temperature or presence of external magnetic field).This contribution demonstrates the importance of a general approach involving a thorough knowledge of the elementary steps of initiation in the understanding of any polymerization conducted in a microheterogeneous medium.
Kinetic and thermodynamic aspects of miniemulsion copolymerization
Authors: Delgado Joaquin , El‐Aasser Mohamed S. 
Published: March 2011

AbstractMiniemulsion polymerization involves initiation of polymerization in preformed stable monomer emulsion droplets with average droplet diameter of 50–500 nm. At the end of the polymerization, only a fraction of the initial number of monomer droplets become polymer particles. The emulsifier system used for the preparation of such emulsions comprises a mixture of ionic surfactant and a fatty alcohol or long chain alkane (termed cosurfactant). The cosurfactant is essential for the formation of stable emulsion droplets and in addition it plays an important role in the interparticle monomer transport.Kinetic results are presented on conventional emulsion and miniemulsion copolymerization of different pairs of monomers, showing the main differences for both processes. These differences were related to the particle formation mechanism and the influence of the cosurfactant in the miniemulsion process.A theoretical model was developed, based on mass balances and equilibrium thermodynamics, which was found to describe accurately the experimentally generated data on comonomer distribution during the course of the copolymerization process and the interdroplet mass transport process.
Non‐seeded semi‐continuous emulsion polymerization
Authors: Šňupárek Jaromír , Skoupil Jan , Podzimek Štêpán , Kaštánek Alois 
Published: March 2011

AbstractSemi‐continuous emulsion polymerization of acrylic monomers was investigated from the point of view of the particle growth. In the process no seed latex was used and the monomers were fed in an emulsion form. Oscillations of surface tension and particle number indicated a periodical generation and flocculation of particles during the polymerization. Investigation of particle size and molecular weight changes in the first tens of seconds of polymerization has shown that the coagulation process proceeds even in the earliest stage of the polymerization. Initial emulsifier concentration in the reactor strongly affects the particle growth and the final particle number.
Emulsion polymerization in the presence of polymerizable emulsifiers and surface active initiators
Authors: Tauer Klaus , Goebel Karl‐Heinz , Kosmella Sabine , Stähler Katrin , Neelsen Jens 
Published: March 2011

AbstractA survey is given of recent developments in emulsion polymerization regarding improved auxiliary materials, e.g. vinyl tensides and surface active initiators. Results of the emulsion polymerization of styrene are presented with 3‐(alkyloxycarbonyl‐acryloyloxy)propanesulfonates (2) as polymerizable emulsifiers and with surface active azo initiators. The results show, that the content of water soluble surface active compounds in the latexes can be reduced. Investigations of the molecular weight of the polymers show the great importance of the initiator‐emulsifier system. Azo initiators leading to higher molecular weights than persulfate. Under the same conditions the highest molecular weights were obtained with a surface active azo initiator.
Grafting of polyethylene powder by vinyl monomers in heterogeneous systems
Authors: Bartuš Ján , Beniska Jozef , Macho Vendelín 
Published: March 2011

AbstractPolyethylene powder bearing hydroperoxide groups was used for grafting of different monomers in aqueous and nonaqueous media. Polymerization of methyl methacrylate in the matrix of photooxidized polyethylene proved to be a sensitive method for detection of early stages of photodegradation. A new redox‐initiation system was developed for grafting of vinyl chloride onto hydroperoxidized polyethylene powder.
Polymerization in inverse microemulsion
Authors: Vašková Viera , Juraničová Viera , Bartoň Jaroslav 
Published: March 2011

AbstractHomopolymerization of acrylamide as well as that of methyl methacrylate and the copolymerization of acrylamide with methyl methacrylate and/or styrene in inverse microemulsion toluene/water 10: 1 by weight have been studied. Water‐soluble ammonium peroxodisulfate, partially water‐soluble 2,2′‐azobisisobutyronitrile, and oil‐soluble dibenzoyl peroxide were used for initiation of these polymerizations at 60°C. Redox initiation system consisting of ammonium peroxodisulfate and tetramethylethylenediamine has been used for an effective initiation of the reactions studied at 30°C. Polymerizations in inverse microemulsions were found start in the interlayer oil macrophase/water microphase. The initial rates of copolymerizations reactions studied depended only on the comonomer mixture composition. The type of the initiator used affected only the exhibited inhibition period.
Polymerization of micelles under irradiation with UV light
Authors: Arai Kenichiro 
Published: March 2011

AbstractMicelle formation behavior of sodium salts of fatty acids containing double bond at the chain end, sodium 10‐undecenoate (Na‐10‐U) and sodium 8‐nonenoate (Na‐8‐N), was examined with measurement of electric conductivity of their aqueous solutions, and the plot of the electric conductivity against the concentration for each fatty acid was found to show two break points; at 0,044 and 0,12mol/1 for Na‐10‐U and at 0,16 and 0,44 mol/1 for Na‐8‐N. The similar behaviors of the aqueous solutions were also found with the measurements of the maximum amount of solubilized benzene into the aqueous solution and of the solution viscosity, and the concentrations corresponding to the break points were assumed to be first and second critical micelle concentrations (CMC's), respectively. Polymerization of the sodium salts under irradiation with UV light was investigated. For each fatty acid, the amount of the obtained polymer was very small at very low concentrations of the fatty acid, but it increased rapidly with increasing concentration of the monomer at concentrations higher than the first CMC and then mildly at the concentrations higher than the second CMC. Number‐average degrees of polymerization of the polymers obtained were measured with a gel permeation chromatography technique and found to be up to 13 for Na‐10‐U and 8,5 for Na‐8‐N.
Chain transfer reactions in emulsion polymerization of butadiene/styrene
Authors: Wendler Karin , Nghiep Phan Hong 
Published: March 2011

AbstractCalculation of regulating index r from M̄W values determined by experiments is proposed. The calculation is based on the assumption that the M̄W values only depend on the conversion and the regulating index in emulsion polymerization. On this basis the calculation of regulator concentration in the latex particles was also possible. M̄W values calculated in this way and experimental M̄W values show good agreement.
One‐shot block copolymerization
Authors: Saegusa Takeo , Chujo Yoshiki , Aoi Keigo , Miyamoto Masatoshi 
Published: March 2011

AbstractThis paper describes a new method of the preparation of block copolymer, in which a mixture of two monomers is subjected to polymerization (simultaneous feeding) by the aid of an initiator. The new method is performed with the polymerization of a family of 2‐oxazolines, which proceeds via electrophilic propagating species, cation or covalent bond having electrophilic reactivity. The key to the block copolymer formation with one‐shot feeding of monomers is the difference of reactivity of polymerization (nucleophilicity) between the two monomers. First the monomer of higher reactivity is polymerized to completion, and then the monomer of decreased reactivity is polymerized starting from the propagating species of the first polymerization. For the high selectivity of the production of block copolymer, each of two propagations should be of “living mechanism”. Two combinations of monomers, i.e., 2‐methyl‐2‐oxazoline/2‐(heptafluoro‐n‐propyl)‐2‐oxazoline and 2‐phenyl‐2‐oxazoline/2‐(pentafluoroethyl)‐2‐oxazoline, together with an initiator of methyl tosylate were found to follow the pattern of the new process. Block copolymer of the former monomers' combination was water‐soluble, and its aqueous solution showed an excellent value of surface tension.
Homogeneous and multiphase poly(methyl methacrylate) graft polymers via the macromonomer method
Authors: Desimone J. M. , Hellstern A. M. , Siochi E. J. , Smith S. D. , Ward T. C. , McGrath J. E. , Gallagher P. M. , Krukonis V. J. 
Published: March 2011

AbstractAnionic and group transfer polymerization processes were used to synthesize controlled molecular weight methacryloyloxy functionalized poly(dimethylsiloxane) and poly(methyl methacrylate) macromonomers having a narrow molecular weight distribution and high percent functionality. These macromonomers were anionically copolymerized with methyl methacrylate (MMA) to afford poly(methyl methacrylate)‐graft‐poly(methyl methacrylate) (PMMA‐g‐PMMA) and poly(methyl methacrylate)‐graft‐poly(dimethylsiloxane) (PMMA‐g‐PDMS) polymers having not only narrow molecular weight distribution graft parts but also backbone parts. The PMMA‐g‐PDMS system was fractionated using supercritical chlorodifluoromethane to determine its chemical composition distribution (CCD). The CCD for the PMMA‐g‐PDMS copolymerized in a living manner was substantially more narrow than the free radically copolymerized material. The PMMA‐g‐PMMA system was used to study the dilute solution properties of branched homopolymers. The appropriateness of the universal calibration gel permeation chromatography (GPC) method for branched systems exhibiting long chain branching was reaffirmed.
Anionic synthesis of chain‐end functionalized polymers
Authors: Quirk Roderic P. , Yin Jian , Guo Shao‐Hua , Hu Xiao‐Wei , Summers Gabriel , Kim Jungahn , Zhu Lin‐Fang , Schock Laurel E. 
Published: March 2011

AbstractThe use of living, alkyllithium‐initated anionic polymerization to prepare chain‐end functionalization reactions is discussed. The scope and limitations of termination reactions with a variety of electrophilic species is illustrated for carbonation, hydroxyethylation, amination, and sulfonation. The methodology of using substituted 1,1‐diphenylethylenes to provide a general, quantitative functionalization method is outlined and illustrated with examples of phenol end‐functionalization and amination.
Group transfer and anionic polymerization: A critical comparison
Authors: Müller Axel H. E. 
Published: March 2011

AbstractThe mechanism of group transfer polymerization (GTP) of methacrylates in THF is investigated by using data on kinetics of homo‐ and copolymerization, polymer microstructure and molecular weight distribution. By comparison with corresponding data on anionic polymerization it is concluded that the mechanisms of monomer addition to the active chain end is very similar for both anionic and group transfer polymerization and that GTP is ionic in character. On the other hand, GTP uniquely is characterized by the existence of a catalyst exchange equilibrium. The position of this equilibrium determines the rates of polymerization, and the dynamics determine the molecular weight distribution.
On the nature of active species in cationic ring‐opening polymerization of cyclodimethylsiloxanes
Authors: Sigwalt Pierre , Stannett Vivian 
Published: March 2011

AbstractContrarily to cationic ring‐opening polymerization of cyclic ethers and of some other cyclic monomers, for which direct identification of the various types of active centres has been made in a few cases, the nature of the species active in the polymerization of cyclo‐dimethylsiloxanes is not yet known. However, some provisional conclusions about the possible mechanisms may be deduced from the wide variation in the types of products and in the kinetics observed according to either the size of the cyclic monomer (D3, D4, D5, D6) and to the type of initiation (chemically, or radiation induced).For polymerizations with either protonic or non‐protonic initiators, made in CH2Cl2 near room temperature, the smaller cycle D3 behaves quite differently from D4, D5 and D6. D3 is more reactive in both homo‐ and copolymerizations. It gives small cycles of other types and the effect of water on the reaction may be quite different. A discussion of the data leads to the conclusion that polymer growth for most cyclosiloxanes involves activated esters, while it may occur for D3 on different sites such as oxonium or silanol groups.Polymerization of D3, D4 and D5 initiated in bulk at 90°C by high energy radiation, in high purity conditions, has also been shown to be cationic but the active centres concentration is much lower, and the propagation rate constants much higher, than in chemically initiated polymerizations. The global rates, the monomer reactivities in copolymerization and the types of cycles are similar for D3, D4 and D5, which is attributed to propagation occurring on very reactive silicenium ions, either free or in the same solvation state.
Living polymerizations of acrylic monomers with aluminioporphyrin
Authors: Inoues Shohei , Aida Takuzo , Kuroki Masakatsu , Hosokawa Yasunori 
Published: March 2011

AbstractAluminioporphyrin was found to be an excellent initiator for the living polymerizations of methacrylates, acrylates, and methacrylonitrile. Porphinatoaluminium thiolate and enolate were effective in the dark, different from methylporphinatoaluminium which requires irradiation by visible light. The addition of pyridine was necessary for the polymerization of methacrylonitrile, which was accelerated by visible light. By using the living polymer of methyl methacrylate as initiator, block copolymers from acrylic monomers could be synthesized. A system composed of aluminioporphyrin and trialkylaluminium was found highly active for the polymerization of methacrylates.
The features of cationic polymerization of lactones under the action of onium salts
Authors: Rozenberg Boris 
Published: March 2011

AbstractResults on the kinetics of polymerization of ϵ ‐caprolactone (ϵ ‐CL) under the action of quaternary onium salts with complex counterions are reported. The structure and molecular weight distribution (MWD) of polymerization products, and of the catalysts and active propagating centers were studied by gel permeation and gas chromatography, IR and UV spectroscopy, chemical and X‐ray analysis. The role of photochemical transformations at ϵ ‐CL polymerization in the presence of onium salts with counterion FeCl4 was revealed. The mechanism of polymerization is discussed.