bluuebunny/crossref_metadata_2025_split huggingface dataset:
The nonlinear change in conformation of polyelectrolyte macromolecules in saltless water‐organic solvent
Authors: Klenin Stanislav I. , Baranovskaya Inga A. , Aseyev Vladimir O. 
Published: March 2011

AbstractHigh molecular weight polyelectrolyte: poly(dimethylaminoethyl methacrylate) [PDMAEMA] with molecular weights MW = 28.0×106, 20.0×106, 15.0×106 was investigated in dilute solution by light scattering, flow birefringence and viscometry (at different rate gradients) in a water‐acetone system by varying the weight fraction of acetone r in the mixture.At r=0.76 the polymer undergoes a reversible coil‐globule transition accompanied by a drastic decrease in intrinsic viscosity [n], mean‐square radius of gyration R2z1/2 and second virial coefficient A2, with no change in molecular weight. The coil asymmetry parameter p (p=2.5 at r=0.50) decreases with increasing r and attains unity (completely symmetrical particle) at the transition point (r=0.76).The anomalous behavior of the viscosity of PDMAEMA‐water‐acetone solutions, detected near the transition point (r=0.6+0.7), is interpreted by formation of local knots of compactization on the molecular chain under the influence of a hydrodynamic field.
Effect of the nature of the alkyl group on initiation and termination in R3Al/RLi initiation of methyl methacrylate
Authors: Haddleton David M. , And Kirsty H Hunt , Crossman Martin C. 
Published: March 2011

AbstractThe polymerisation of methyl methacrylate has been investigated with mixed aluminium and lithium alkyls. The use of sterically hindered aluminium alkyls such as triisobutyl aluminium in conjunction with tert‐butyl lithium leads to living polymerisation at 0°C with little complications from secondary initiation or premature termination. The use of less bulky alkyl groups on either aluminium or lithium leads to both secondary initiation, as observed by the formation of high molecular weight polymer by GPC‐LALLS and termination via cyclisation as observed by MALDI‐TOF‐MS. The initiator efficiencies, even when living polymerisation ensues, are considerably less than 100%.
Estimation of the surface energetic heterogeneity of fillers by inverse gas chromatography
Authors: Balard Henri , Saada Alain , Hartmann Jacques , And Omar Aouadj , Papirer Eugène 
Published: March 2011

AbstractThe surface properties of the fillers are determining for obtaining high performance filled polymers. Yet, their determination is most difficult. This paper proposes to use inverse gas chromatography, either at infinite dilution or finite concentration conditions, to estimate surface energy and nanomorphological characteristics, but also surface heterogeneity of different clays, talcs of various origins and ground muscovites.
Effect of filler‐matrix debonding on tensile behavior of glass beads filled polystyrene (PS)
Authors: Meddad A. , Fisa B. 
Published: March 2011

AbstractIn this work, the debonding process in filled plastics during constant strain rate tensile loading is analyzed both theoretically and experimentally. A model which combines concepts of damage mechanics and the time dependence of interfacial strength is proposed and compared with experimental results on glass bead filled polystyrene. The stress‐strain behavior and the debonding can be modeled using a Bartenev type relation for the destruction of the interfacial bond and by considering the gradual transformation on the initially well bonded composite into foam. A good agreement between calculated and experimental data was achieved.
Properties of solvent based polyurethane adhesives containing fumed silicas
Authors: Martín‐Martínez José M. , Maciá‐Agulló Trinidad G. , Fernández‐García Juan C. , Orgilés‐Barceló A. césar , Torró‐Palau Ana 
Published: March 2011

AbstractFive hydrophilic and two hydrophobic fumed silicas of different surface area and particle size were added to solvent based polyurethane adhesives. Silica addition produced a noticeable increase in the adhesive viscosity, imparted negative thixotropy, increased the storage modulus (G') and improved the green adhesion of chlorinated rubber/PU adhesive/chlorinated rubber joints. Those modifications were more pronounced in the adhesives which contain hydrophilic silicas.
Fast swelling/deswelling kinetics of comb‐type grafted poly(N‐isopropylacrylamide) hydrogels
Authors: Kaneko Yuzo , Sakai Kiyotaka , Kikuchi Akihiko , Sakurai Yasuhisa , Okano Teruo 
Published: March 2011

AbstractThe synthesis and characterization of comb‐type grafted thermo‐sensitive hydrogels is presented. These hydrogels were synthesized by polymerization of N‐isopropylacrylamide (IPAAm) with a PIPAAm macromonomer. This process leads to a crosslinked IPAAm backbone polymer, copolymerized with highly mobile comb‐type PIPAAm chains. These new thermo‐responsive copolymers displayed higher equilibrium swellings at lower temperatures and rapid deswelling kinetics at elevated temperatures. The swelling/deswelling for comb‐type gels is dependent on the graft chain lengths, in contrast to normal PIPAAm gel lacking the graft chains. As the temperature is increased above the critical temperature, the dehydrated graft chains aggregated due to hydrophobic attraction. Rapid and reversible kinetics of the graft‐type gel were observed in response to stepwise temperature changes within short time cycles: phenomena not observed in normal crosslinked thermo‐sensitive gels. The influence of freely mobile graft chains on both the equilibrium and dynamic properties of comb‐type PIPAAm gel is demonstrated. Possible application of graft‐type gel is discussed for actuator systems.
A new form of controlled growth free radical polymerization
Authors: Krstina Julia , Moad Catherine L. , Moad Graeme , Rizzardo Ezio , Berge Charles T. , Fryd Michael 
Published: March 2011

AbstractA new form of controlled growth free radical polymerization leading to narrow polydispersity polymers and/or block copolymers is described. The process is based on the polymerization of monomers in the presence of macromonomers of general structure CH2=C(Z)CH2(A)n [(A)n= radical leaving group, Z = activating group] and displays many of the characteristics of living polymerizations. The process is most suited to methacrylic monomers but with the appropriate choice of reaction conditions (high temperatures and/or low conversions) it can also be applied to acrylic and styrenic monomers. The macromonomers are conveniently prepared by catalytic chain transfer to alkyl cobalt(III) complexes or by addition‐fragmentation chain transfer. The factors which determine the efficiency of cobalt complexes for molecular weight reduction in free radical emulsion and solution polymerization of methyl methacrylate are also discussed.
Influence of molecular structure on the free radical initiated network polymerization of dimethacrylates
Authors: Shobha H. K. , Sankarapandian M. , Shultz A. R. , McGrath J. E. , Kalachandra S. , Taylor D. F. 
Published: March 2011

AbstractThe free radical polymerization of several new dimethacrylates initiated by azobisisobutyronitrile (AIBN) at various temperatures was investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FT‐IR), and solid state NMR. The new monomers contained features, such as fluoroalkyl and/or pendant methyl or hydrogen instead of hydroxyl groups, which promoted both low viscosity and low monomer glass transition temperatures. The percent conversion was significantly improved, relative to a well‐studied control dimethacrylate as measured by both DSC and FT‐IR. Increasing the reaction temperature and the initiator concentration also led to enhanced conversion behavior and the apparent activation energies for the polymerization are reported. The results suggests that the new crosslinked material systems could show several advantages relative to the control bisphenol‐A based diglycidyl methacrylate.
Semi‐suspension polymerization process
Authors: Mahabadi Hadi K. , Wright Denise 
Published: March 2011

AbstractA novel heterogeneous polymerization process for synthesizing particulate with a wide range of properties has been developed. This process, which is called semi ‐ suspension polymerization (SSP), consists of two steps. In the first step a mixture of monomer, polymer, initiator, and other required ingredients is prepared by means of a non‐ suspension polymerization process. In the second step, this mixture is suspended in the continuous phase and is polymerized to complete conversion. The properties of the semi‐polymerized mixture prepared in the first step as well as the rate of polymerization in the second step can be used to control inter‐droplet and/or intra‐particle mass transfer. This unique capability allows control of the mass transfer between and within particles during the suspension polymerization, thereby enabling synthesis of particulate with a wide range of molecular properties and morphologies unattainable by conventional suspension polymerization. The characteristics of this process and its advantages/limitations will be discussed.
Preferential sorption of monomers and molecular weight effects in radical copolymerization
Authors: Semchikov Y U. D. 
Published: March 2011

AbstractSpecific thermodynamic properties of monomer mixtures as a solvent for copolymers lead to preferential sorption of one of the monomers by the polymer coils and preferential solvation of growing chains. The dependence of the preferential sorption coefficient upon the molecular weight of the copolymers results in the dependence of copolymer composition and monomer reactivity ratios upon the molecular weight of the copolymers and in gradient chemical heterogeneity of the copolymers. “Non‐classical” copolymerizations can be represented by both terminal and penultimate models.
Analysis of mixing efficiency in polymer processing equipment
Authors: Manas‐Zloczower Ica , Cheng Hongfei 
Published: March 2011

AbstractFlow patterns In various processing equipment were obtained based on 3D isothermal flow simulations. These flow patterns were further processed for mixing efficiency analysis. The dynamics of the mixing process was studied numerically by means of tracers and their trajectories In the processing equipment. Dispersive mixing efficiency was studied in terms of shear stresses and elongational flow components distributions. Distributive mixing efficiency was characterized using length stretch distributions and average values. Features of chaotic flow were also analyzed. The framework developed to analyze mixing efficiency opens the way for an unambiguous evaluation of equipment performance and for process optimization.
Phase transitions in polymer brushes
Authors: Birshtein Tatiana M. , Amoskov Victor M. , Mercurieva Anna A. , Pryamitsyn Victor A. 
Published: March 2011

AbstractLiquid crystalline ordering in planar polymer brushes is investigated theoretically by numerical calculations within a self‐consistent field approximation. The brushes are formed by macromolecules with mesogenic groups in main chain and immersed in a solvent. Existence of a microphase segregated brush (MSB) regime with a collapsed orientationally ordered intrinsic sublayer and a swollen external sublayer is shown. At small grafting density, the transition from a conventional brush state to the microphase segregated state is a jump‐wise first order phase transition for a finite chain length (N). The magnitudes of the jumps in the average characteristics of the brush tend to zero in the limit N → ∞ since this transition occurs only in a vanishingly small part (∝ N−1/2) of the brush. High compressibility of MSB brush is demonstrated. The origin of phase transition in planar brushes is discussed.
Sorption studies that reflect sequential physical changes in polymer‐liquid systems from saturation to virtual dryness in a glassy state
Authors: Errede Louis. A. 
Published: March 2011

AbstractThe changes in macromolecular architecture that occur sequentially when a polymer is allowed to swell to saturation in a test‐liquid and then evaporated from its gel‐saturated state through its rubbery transition and finally down to a glassy state at virtual dryness are described in detail. The influence of molecular structure of the sorbed liquid and temperature on the kinetics of evaporation during each part of the above cycle is discussed. The relevance of these results with respect to the models proposed by polymer physicists to describe thermoreversible gelation and polymer relaxation in the glassy state is also discussed.
Rheology of ethyl cellulose solutions
Authors: Santamaría Antonio , Lizaso M. Isabel , Muñoz M. Eugenia 
Published: March 2011

AbstractSteady state flow and dynamic viscoelastic measurements of ethyl cellulose / m‐Cresol solutions reveal the existence of an isotropic and anisotropic phase, as well as a biphasic interval. The effect of the applied shear rate is to shift the anisotropic phase to lower concentrations. The anisotropic phase, which is found from 20 wt.‐% polymer concentration, is characterized by the following features: A) Three flow regions, pseudoplastic, Newtonian and pseudoplastic, respectively, are observed in \documentclass{article}\pagestyle{empty}\begin{document}$ \eta - \dot \gamma _{21} $\end{document} plots but not in η* ‐ ω plots, b) “Grainy” and “thread” textures correspond to regions I and II respectively, c) Activation energies of flow are similar to that of the pure solvent, d) Both dynamic viscoelastic functions G′ and G″ scale with frecuency as ω0.75, a dependence already observed in complex liquids, like heterogeneous block copolymers.On the other hand, dynamic viscoelastic measurements performed with isotropic systems allow to determine the entanglement modulus and the associated molecular weight between entanglement couplings, Me0=7830.
Correlation between static mechanical properties of starch‐glycerol materials and low‐temperature relaxation
Authors: Lourdin Denis , Bizot Hervé , Colonna Paul 
Published: March 2011

AbstractMechanical, calorimetric, dynamic mechanical and dielectric properties were measured in starch and amylose films plasticized by different glycerol contents. Low‐temperature relaxation was found to be highly dependent on plasticizer level and related to unusual mechanical properties.
The photooxidative degradation and stabilisation of water‐borne acrylic coating systems
Authors: Allen N.S. 
Published: March 2011

AbstractThe influence of manufacturing and processing parameters on the photooxidative stability of aqueous acrylic based latices is examined by FTIR and hydroperoxide analysis. These are based on emulsion polymerised formulations of methyl methacrylate and butyl acrylate. Here acrylic latices based on different formulations are chosen as homo‐polymers and copolymers. The nature of impurities and oxidation products generated during their manufacture are characterised and inter‐related to their influence on subsequent photooxidative degradation. This involves the use of reflectance FT‐IR spectroscopy to show functional group changes together with colourmetric U.V. analysis to determine the photochemical generation of hydroperoxides. The early chemical changes and their subsequent influence on the physical and chemical properties of the latices during the later stages of photooxidation are found to exhibit a close inter‐relationship. To date the nature of the surfactant and the composition of the latex in terms of end group modification are important parameters. De‐esterification and hydroperoxide formation are found to be important processes during latex photooxidation while the addition of low levels of co‐monomer to the emulsion give latices with improved photostability. While co‐reactive hindered piperidine stabilisers are found to be effective the incorporation of simple terminal dialkyl acrylamide/methacrylamide groups are equally as effective. Oxygen scavenging via the formation of alkylamino radicals is disussed.
Nucleic acid analogues: Synthesis and biomimetic reactions
Authors: Han Man Jung , Chang Ji Young 
Published: March 2011

AbstractSeveral nucleic acid analogues as shown in Scheme 1 were synthesized by alternating copolymerization of nucleoside analogues with maleic anhydride or acrylic anhydride. These polymers showed similar physicochemical properties to those of the natural polymers, such as base‐pairing and base‐stacking. Polymer 3U, for example, formed 1:1 complex with poly(adenylic acid) by base‐pairing. Polymer 4A showed 33% of hypochromicity compared with the UV‐absorption of adenosine due to the base‐stacking. Polymer 5 catalyzed the cleavage of DNA and the hydrolysis of phosphodiester with a rate acceleration of 103 compared with the uncatalyzed reaction.
Synthesis and property of shish‐kebab type liquid crystalline polymers with chiral carbons
Authors: Zhou Qi‐Feng , Xie Ren , Zhu Yan‐Tao 
Published: March 2011

AbstractNew polymers with chiral carbons and with rod‐like mesogenic units being stringed at waist (as the “kebabs”) by the main‐chain (as the “shish” or “skewer”) were synthesized and studied. All the chiral polymers are optically highly active and have strong tendency of nematic phase formation.
Intermacromolecular complexation in solution and complex blends
Authors: Jiang Ming 
Published: March 2011

AbstractBy progressively increasing the hydrogen bonding interaction, otherwise immiscible polymer blends composed of modified polystyrene and poly(alkyl methacrylate) can achieve miscibility and complexation successively. The differences in chain arrangement between the states of mere miscibility and complex can be detected by a modified NRET fluorescence technique. Immiscibility‐miscibility‐complexation transitions have been proved to be of generality for polymer blends with controllable hydrogen bonding.
Novel polymers containing carbazole chromophores for nonlinear optics: Photorefractive application
Authors: Wada Tatsuo , Zhang Yadong , Wang Liming , Sasabe Hiroyuki 
Published: March 2011

AbstractOligomers and polymers containing carbazole chromophores in the main chain and/or side chain have been designed and synthesized as a model compound of monolithic photorefractive materials. Nonlinear optical properties of these compounds and image processing application have been studied.
Oxidation and aging of cellulose
Authors: Lewin Menachem 
Published: March 2011

AbstractOxidation of cellulose by chlorine, bromine, hydrogen peroxide and ozone and the functional groups formed are reviewed. The roles of the pH and of the nature of the oxidant in the formation of carboxy‐ and keto‐celluloses are discussed. The relationships between the functional groups, degradation and stability of the celluloses enable to predict the aging and storage behavior of the polymer. The “active” carbonyls are responsible for the peeling reaction and the formation of the yellow chromophore in alkaline solutions as well as for the reversion in color on aging. The nature of the yellow chromophore, its spectra at several pH values, its use for the characterization of cellulose, e.g. the rapid determination of the degree of polymerization and for the estimation of the primary and secondary degradation of the polymer and its stability on storage and aging are discussed. The parallelism between the yellowing and the reversion in color is reviewed.
Particularities in the structure of amylopectin, amylose and some of their derivatives in solution
Authors: Aberle Thomas , Burchard Walther , Hanselmann Ralf , Michel Eduard , Klingler Rudolf W. , Galinsky Gabriela 
Published: March 2011

AbstractBecause of a well defined supramolecular architecture of the native starch granules the preparation of molecularly dispersed starch solutions is achieved only after autoclaving at temperatures of 135 to 160 C. A detailed analysis of static light scattering data allowed the determination of the molecular parameters of both the amylopectin and amylose. The results were confirmed by (1) measurements in the iron sodium tartrate complex FeTNa, (2) by extrapolation of the data obtained with degraded starches to no degradation and (3) by sedimentation field‐flow‐fractionation sFFF. Above the overlap concentration strong aggregation due to H‐bonding commenced and eventually led to gelation. The process is promoted by the amylose content and could be followed by static and dynamic light scattering. Cationic starches and cationic amyloses display remarkably different behavior. The branched amylopectin expanded uniformly when the ionic strength was lowered but the corresponding amylose exhibited an unusual helix‐disorder transition.
Structural characteristics of crosslinking domain in gellan gum gel
Authors: Yuguchi Yoshiaki , Urakawa Hiroshi , Kajiwara Kanji 
Published: March 2011

AbstractGellan gum samples having different counterions of TMA+ (tetramethyl‐ammonium ion), Na+, K+ and Cs+ were prepared, and the small‐angle X‐ray scattering was observed from the aqueous solutions of those samples. A sharp peak appears in the SAXS profile at low temperature, indicating the electrostatic interaction between the domains composed of multiple gellan gum chains. The SAXS profile revealed a rigid rod‐like characteristics of gellan gum chain. The cross‐sectional radius of gyration was evaluated from the scattering profiles, and the gelation mechanism was discussed from the change of the cross‐sectional radius of gyration upon gel‐sol transition. Taking the difference of the scattering power of counter ions into account, the ion condensation due to gelation was evaluated from the excess scattering of Cs+ gellan gum with respect to K+ gellan gum in respective aqueous solutions.
Cellulose‐p‐toluenesulfonates: A valuable intermediate in cellulose chemistry
Authors: Heinze Thomas , Rahn Kerstin 
Published: March 2011

AbstractOrgano‐soluble cellulose‐p‐toluenesulfonates (tosylates) with an insignificant incorporation of chlorodeoxy functions were prepared by reacting cellulose dissolved in N,N‐dimethyl acetamide/LiCl and used as intermediates in the design of cellulosics with new, unusual molecular structures. Thus, the remaining OH groups were acylated and sulfated yielding products with controlled lipophily and amphiphily which are promising polymers for self‐organizing systems. The polarity reversal by tosylation was used for C‐substitution reactions. The molecular structures of the products were proved by FTIR, 1H‐ and 13C‐NMR spectroscopy.