bluuebunny/crossref_metadata_2025 huggingface dataset:
Polypyrrole: Synthesis and electronic device application
Authors: Satoh Masaharu , Hasegawa Etsuo
Published: March 2011

A Ta solid electrolytic capacitor using conducting polypyrrole as a counter electrode has been developed by means of the direct film formation of electrochemical and chemical polymerization methods. Two‐step electrochemical polymerization at a rapid and gentle rate yields a polypyrrole film on the dielectric surface of the capacitor. On the other hand, the homogeneous mixture dissolving pyrrole and oxidant under −70 °C allows chemical polymerization at elevated temperature, which also produces polypyrrole film on the dielectric surface. The capacitors produced by these methods demonstrate the improved characteristics, i.e., a high capacitance, low inner resistance and small leakage current, that correspond to the high‐speed electronic devices.
Synthesis and mesomorphic properties of fishbonelike, liquid crystalline polysilsesquioxanes: 4. Pd‐coordinating, fishbone‐like imine‐based liquid crystalline polysilsesquioxane
Authors: Wan Youzhi , Huang Yaxuan , Xie Ping , Li Bo , Jin Shunzi , Cao Xinyu , Liu Dongsheng , Dai Daorong , Li Ze , Zhang Rongben
Published: March 2011

A new type of Pd‐coordinating, imine‐based, fishbone‐like liquid crystalline polysilsesquioxanes (Pd‐FBI) including μ‐acetato‐bridged Pd‐FBI [Pd(μ‐oAc)‐FBI] and μ‐chloro‐bridged Pd‐FBI [Pd(μ‐Cl)‐FBI] has been synthesized first by a hydrosilylation reaction to form fishbone‐like, imine‐based liquid crystalline polysilsesquioxane (H‐FBI and MH‐FBI respectively,) and then by an ortho‐palladation reaction with palladium acetates to obtain Pd(μ‐oAc)‐FBI. The latter was further subjected to ligand substitution reaction with NaCl to form Pd(μ‐Cl)‐FBI. Their mesomorphic properties investigated by differential scanning calorimetry (DSC) and optical polarization microscopy (OPM). show that the Pd‐FBI is a thermotropic liquid crystalline polymer and its clearing temperatures and mesophase range are much higher than those of the corresponding comb‐like imine liquid crystalline polysiloxanes (IMLCP) by about 100 °C. In this paper the influence of the palladium content on mesogenic behavior is discussed.
Ionomer‐surfactant self‐assembly in low‐polarity solvents
Authors: Bakeev Kirill N. , Chugunov Sergey A. , Larina Tat'yana A. , Macknight William J. , Zezin Alexander B. , Kabanov Viktor A.
Published: March 2011

A systematic study of complexation reactions of sulfonated polystyrene ionomers containing up to 5 molar percent of polar chain units with various oil‐soluble surfactants is carried out in low‐polarity organic solvents. Dipole‐dipole attractions of the components lead to the formation of complexes characterized by limiting compositions and an unusual polymer‐colloidal morphology of joint clusters and/or micelles. The limiting compositions (φ) for the complexes formed between ionomers and surfactant of the same charge (bis(2‐ethylhexyl)sulfosuccinate sodium salt), or nonionic surfactants (primarily aliphatic amines) are equal to 15–30 surfactant molecules per one ionomer salt/acid group on average, with φ depending on the hydrophilic‐lypophilic balance of the components, the initial aggregation state of surfactant and the nature of low‐polarity solvent. Ionomersurfactant complexation is accompanied by disruption of self‐contacts of ionomer salt/acid groups, leading to “unfastening” and expansion of the ionomer coils in dilute solution. The “driving force” of the ionomersurfactant complexation and the structure of the resultant complexes are discussed.
Self‐assembly in ω‐functionalized block copolymers of styrene and isoprene
Authors: Floudas G. , Fytas G. , Pispas S. , Hadjichristidis N. , Pakula T. , Khokhlov A. R.
Published: March 2011

The spatial organization of end‐functionalized diblock copolymers of styrene and isoprene revealed two separate levels of microphase separation: one between the two blocks forming the microdomain and another between the polar and non‐polar material. The association produced by the latter process has a pronounced effect on the dynamics as revealed in rheology and dielectric spectroscopy. The introduction of a polar group into the different chain‐ends has a dramatic effect on the phase behavior of the diblock copolymers and provides new ways of controlling their miscibility.
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

High 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

The 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

The 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

In 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

Five 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

The 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

A 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

The 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

A 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

Specific 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

Flow 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

Liquid 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

The 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

Steady 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

Mechanical, 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

The 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

Several 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

New 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

By 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

Oligomers 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

Oxidation 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

Because 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

Gellan 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

Organo‐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.
Rheological and DSC studies of mixtures of gellan gum and konjac glucomannan
Authors: Miyoshi Emako , Takaya Tomohisa , Nishinari Katsuyoshi , Williams Peter A.
Published: March 2011

The interaction between gellan gum (GELL) and konjac glucomannan (KGM) with and without sodium chloride, potassium chloride, calcium chloride and magnesium chloride has been monitored using mechanical spectroscopy and differential scanning calorimetry (DSC). The rheological results indicated that the synergism occurred at sufficient low temperatures where individual helices of GELL molecules were sufficiently aggregated. With progressive addition of monovalent cations, storage shear modulus G' and loss shear modulus G” for mixtures gradually increased, and not only the helix‐coil transition temperature of GELL molecules in mixtures but also the sol‐gel transition temperature for mixtures shifted to higher temperatures with increasing concentration of salts. Moreover, in the presence of sufficient monovalent cations, mixtures formed an elastic gel with large thermal hysteresis. In the presence of divalent cations, the synergistic interaction was promoted up to a certain concentration, however, with more progressive addition of divalent cations, the main structure formed by aggregates of GELL helices would be smaller, so that mixtures could not form a gel in the presence of excessive divalent cations. DSC results indicated that the intermolecular binding complexes between GELL and KGM molecules would not occur, but KGM markedly influenced the disorder‐order transition of GELL molecules. We have suggested that KGM was attached to the surface of large aggregates of GELL helices, and since cations promote GELL self‐aggregation by a screening effect, the synergistic interaction between GELL and KGM was promoted with increasing concentration of salts. However, excessive divalent cations formed various aggregates of GELL helices with different thermal stabilities, so that the phase‐separation in GELL/KGM mixtures was promoted in the presence of excessive divalent cations.
Association behavior of living anionic lipophobic head‐groups in hydrocarbon mileau
Authors: Fetters L. J. , Huang J. S. , Stellbrink J. , Willner L. , Richter D.
Published: March 2011

The commercial applications of anionic polymerization have become wide‐spread with regard to the preparation of linear and star shaped homopolymers and block copolymers (Diene‐35TM, KratonTM, VectorTM, SolpreneTM, K ResinTM and ShellVisTM). Furthermore, randomized styrene/butadiene linear copolymers (SolpreneTM) and low molecular weight, 10K or less, polybutadienes (LithenesTM) of various microstructures are commercially available. Recently Liquid KratonsTM with OH functional units in place on one or both chain ends have become items of commerce. The lithium based systems yield materials of uniform composition and molecular weights with virtually monodisperse molecular weight distributions. Both molecular weight and composition are tunable via the simple expedient of manipulating the monomer/initiator ratio. Although the synthetic aspects of these anionic systems have been well‐mastered and exploited over the years the mechanistic features have remained controversial; issues which revolve around active center aggregation behavior and the reactivity (or its absence) of these self‐assembled anionic lipophobic head‐groups. Thus a study of these systems was undertaken using modern scattering techniques and data analysis procedures.

Small angle neutron scattering (SANS) in combination with dynamic and static light scattering, DLS and SLS, has been used to evaluate the association behavior of the styryl‐ and dienyllithium head‐groups in benzene and cyclohexane solutions. Both types of lipophobic active centers were found to aggregate as dimers which in turn can self‐assemble to yield large‐scale wormlike micelles (prolate ellipsoids). These systems thus emulate the behavior of diblock copolymers and surfactants in their capacity to form flexible cylindrical micelles. It was also found for all head‐groups that the combination of long chain lengths and high polymer concentrations favored the presence of the dimer structure. This commonality of aggregation state is in consonance with results given in 1964.
The short time regime of segmental dynamics of glass‐forming polymers
Authors: Colmenero Juan , Arbe Arantxa
Published: March 2011

The short time regime (10−13 s ≤ t ≤ 10−11 s) of the segmental dynamics of several glass‐forming polymers with different chemical microstructure and glass‐transition temperature has been investigated by means of time of flight (TOF) neutron scattering techniques. In this paper we present a summary of the main results obtained as well as the theoretical framework proposed by us to interpret these results. The main conclusion is that the segmental dynamics of glass‐forming polymers display in the very short time range (t = 2 ps) a crossover from a simple exponential behaviour towards a non‐exponential regime. The first exponential decay, which is controlled by C‐C rotational barriers, can be understood as a trace of the behaviour of the system in absence of the effects (correlations, cooperativity, memory effects…) which characterise the dense supercooled liquid like state against the normal liquid state. The non‐exponential regime at t > 2 ps corresponds to what is usually understood as α and β relaxations. Some implications of these results are also discussed.
Nonlinear dynamics of melted polymer layers
Authors: Semenov A. N. , Subbotin A. V. , Hadziioannou G. , Ten Brinke G. , Manias E. , Doi M.
Published: March 2011

A theory for non‐linear rheology of molten polymer layers between solid surfaces in the Rouse regime is discussed. It is shown that the effect of finite extensibility of polymer chains leads to the characteristic 1/3 power law for the shear stress vs. shear velocity in the regime of high velocities. It is also shown that bridging polymer fragments connecting the two surfaces play an important role for the rheology if the effective monomer friction in the immediate vicinity of the surfaces is much higher than far from the surfaces. In particular we predict that shear stress is decreasing with shear velocity u in a limited range between u1 and u, min. This effect results in a possibility of stick‐slip periodical dynamics of the layer under a constant imposed velocity.
Brownian configuration fields: A new method for simulating viscoelastic fluid flow
Authors: Brule Ben Van Den , van Heel Ton , Hulsen Martien
Published: March 2011

In this paper a new method for calculating viscoelastic fluid flows is presented. The polymer stress is not calculated from a closed form constitutive equation but from a microscopic model. Instead of considering the motion of individual molecules we calculate the evolution of an ensemble of configuration fields, representing the internal degrees of freedom of a model molecule. The configuration fields are deformed and convected by the flow and are exposed to thermal motion. The field description is incorporated in a finite element calculation of the flow field where the stress in the fluid is now obtained from an average taken over all the configuration fields. The results for flow past a cylinder for a Hookean dumbbell suspension will be compared with the results obtained from a fully macroscopic calculation of the equivalent Oldroyd‐B model. Excellent agreement is obtained.
New organo‐soluble polyimides for optical, microelectronic and fiber applications
Authors: Harris Frank W. , Li Fuming , Lin Sheng‐Hsien , Chen Jyh‐Chien , Cheng Stephen Z. D.
Published: March 2011

A novel class of organo‐soluble polyimides has been developed based on monomers containing twisted‐biphenyl structures. Thus, 2, 2'‐disubstituted‐4, 4'‐diaminobiphenyls and 2, 2'‐disubstituted‐4, 4', 5, 5'‐biphenyltetracarboxylic dianhydrides have been prepared and polymerized in refluxing phenolic solvents. The polyimides, some of which are soluble in ketone and ether solvents, can be readily solution cast into colorless thin films. The rigid polymer chains align parallel to the substrate surface (in‐plane orientation) during the casting process, which results in anisotropy in the film properties. The anisotropy in the refractive index has been used in the development of compensation layers for liquid crystal displays. The polymers have also been dry jet‐wet spun from phenolic solutions to afford fibers that display tensile strengths of 3.5 GPa and moduli of 130 GPa.
Quantum semiempirical study of the reactivity of monomers in the synthesis of aromatic polyamides and polyimides
Authors: Lozano Angel E. , De Abajo Javier , De La Campa José G.
Published: March 2011

The amidation and imidation reactions have been studied by quantum semiempirical methods, determining the influence of different types of substituents on the geometries and electronic parameters of diamines, either unsilylated or silylated, diacyl chlorides and dianhydrides. It was confirmed that the energy of the frontier orbitals, ELUMO in the electrophiles and EHOMO in the nucleophiles, is the main parameter that controls the reactivity of the different monomers.
New phytoactive polymers prepared by polycondensation
Authors: Manolova Nevena , Ignatova Milena , Rashkov Iliya , Sepulchre Maurice , Spassky Nicolas
Published: March 2011

Some new poly(ether‐ester)s (PEEs) and poly(ether‐amide)s (PEAs) with polyether sequences linked by tartrate units have been synthesized. Derivatives bearing residues from the synthetic plant‐growth regulator 1‐naphthylacetic acid (NAA) as pendent groups and end‐groups have been prepared by esterification of PEEs and PEAs with NAA. Polymers bearing residues from pyridine‐2, 6‐dicarboxylic acid (a herbicide) in the main chain have been prepared. The hydrolysis has been found to depend on the structure of the polymer carrier, on pH of the medium and on the ability of the polymers to form complexes with polyacids. The phytosanitary activity of the new polymers has been related to the particular features of their hydrolysis behaviour.
Atomic force microscopy and enzymatic degradation of oyster shell protein and poly(aspartate)
Authors: Steven Sikes C. , Martin Frances , Wierzbicki Andrzej , Wheeler A. P.
Published: March 2011

Oyster shell protein (OSP), an aspartate‐enriched regulator of crystallization, was readily observed in its natural condition by atomic force microscopy (AFM) of fragments of oyster shell. The fragments of shell consisted of layers of calcite mineral, termed folia, to which arrays of protein molecules are attached. Modification and removal of the OSP following treatment with several proteolytic enzymes such as subtilisin, carboxypeptidase B, and endoproteinase Glu‐C were also observed by AFM. Similarly, poly (aspartate), a polypeptide analog of the OSP, was visualized by AFM on both calcite and mica. Images of poly(aspartate) before and after treatment with lipase demonstrated the potential utility of AFM in degradation studies. The mechanism of hydrolysis is not clear in that lipase normally is considered to be an esterase and not a peptidase.
The concept of cohesional entanglement
Authors: Qian Renyuan
Published: March 2011

A concept of cohesional entanglement through local nematic interaction of neighboring chain segments has been introduced in addition to the usual topological entanglement of chains. As topological entanglement is important to properties of the polymer in the rubbery and flowing states at temperatures well above its Tg, the cohesional entanglement is important to properties at temperatures around and below Tg. Evidences for the existence of cohesional entanglements are presented. From the point of view of cohesional entanglement the DSC curves of glass transition and the effect of sub‐Tg annealing are discussed. Finally the stress peak on yielding during uni‐axial drawing, rejuvenation of sub‐Tg annealed polymer by drawing and anti‐plasticization of plastics are discussed based on the concept of cohesional entanglement.
Electroluminescence in polymers
Authors: Yang Zhou , Hu Bin , Karasz Frank
Published: March 2011

Polymeric materials containing chromophores are promising for electroluminescent (EL) device applications including displays and lighting. We report EL for a series of copolymers containing uniform conjugated chromophores and nonconjugated spacers. The emission color of the copolymers can be varied by adjusting the molecular structure to alter the energy gap between the HOMO and LUMO of the chromophore. The design can also be used to tailor other properties of the polymer, such as the glass transition temperature, by varying the length of the nonconjugated spacers.
Metal induced photoluminescence quenching of a phenylene vinylene oligomer and its recovery
Authors: Choong Vi‐En , Park Yongsup , Gao Yongli , Hsieh Bing R. , Tang Ching W.
Published: March 2011

Metal/polymer interfaces play an important role in polymeric light emitting diodes (LEDs). In typical organic light‐emitting devices, metallic electrodes are used to inject charged carriers into the organic electroluminescent (EL) medium. However, what other effects the metals have on the organic medium is not well known. In this work, we report severe photoluminescence (PL) quenching of organic thin films comprising of one of the most useful materials, namely 1,4‐bis[4‐(3,5‐di‐tert‐butylstyryl)styryl]benzene (4PV), upon sub‐monolayer deposition of Al, Ag, and Ca in an ultra high vacuum environment. The severity of the luminescence quenching may greatly affect the EL device performance. Gap states at the Ca/4PV interface are shown to be responsible for the PL quenching. The oxidation of Ca resulted in the removal of the gap states and the recovery of the quenched PL.
The interaction of cationic polymers with human hair
Authors: Pfau Andreas , Hössel Peter , Vogt Sabine , Sander Ralf , Schrepp Wolfgang
Published: March 2011

We present a combination of electrochemical methods, i.e. polyelectrolyte titration and streaming potential measurement, and AFM to characterise the adsorption and desorption behaviour and the morphology of a set of polyquaternium polymers on human hair. Specific charge density and molar mass are correlated to the amount of adsorbed polymer and the ease of desorption. Results are in line with a simple model of coulombic interaction between hair and polymer and are interpreted on this basis.
Crystallization and melting behaviour of poly(ferrocenylsilanes)
Authors: Hempenius Mark A. , Lammertink Rob G. H. , Julius Vancso G.
Published: March 2011

A series of poly(ferrocenyldimethylsilanes) was prepared anionically in order to study their melting behaviour. The DSC traces of these polymers displayed multiple endotherms that could be assigned to melting of lamellae with varying thicknesses. Upon heating, thinner lamellae are converted into thicker ones in a continuous melting‐recrystallization process.
Novel styrene‐butadiene block copolymers by sequential and statistical copolymerization of corresponding macromonomers
Authors: Grande Daniel , Six Jean‐Luc , Héroguez Valérie , Gnanou Yves , Fontanille Michel
Published: March 2011

This paper concerns the synthesis of two different structures of styrene‐butadiene block copolymers that were respectively obtained via sequential and statistical ring‐opening metathesis copolymerization of norbornene‐terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene‐butadiene copolymers originates from the observation that phase‐separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (χ), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two types of copolymers ‐prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively‐ exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.
Synthesis of novel block copolymers through electron transfer system by smi2
Authors: Nomura Ryoji , Endo Takeshi
Published: March 2011

This paper summarizes our recent efforts to offer block copolymers through the transformation reactions of a cationic growing center into an anionic one by the utilization of divalent samarium complexes. Four types of transformation reactions are described, and their scope and limitations are discussed. Several applications of these transformation reactions are also presented.
Intelligent networks based on poly(oxyethylene)
Authors: Tsvetanov Christo B. , Stamenova Rayna , Dotcheva Dobrinka , Doytcheva Maria , Belcheva Nadya , Smid Johannes
Published: March 2011

Films of PEO and PEO blends were efficiently crosslinked by exposure to ultraviolet radiation with high‐pressure mercury lamp. Photochemical crosslinking proceeded in the presence of photoinitiator such as benzophenone or pentaerythritol triacrylate. PEO networks obtained by UV irradiation in the presence of potassium salts (thiocyanate, perchlorate and triflate) as templates showed enhanced cation binding ability for Li+ and Na+ cations. Cationic networks were prepared from crosslinked PEO modified with ethyl methacrylate dimethyl dodecyl ammonium bromide. Stimuli‐sensitive hydrogels (pH and temperature) were prepared from combinations of PEO and poly‐N‐isopropyl acryl amide, polyvinyl methyl ether, polyvinyl acetate and poly‐2‐vinyl pyridine subjected to UV irradiation.
Novel polyolefin materials via catalysis and reactive processing
Authors: Suhm Jürgen , Heinemann Johannes , Wörner Christof , Müller Philipp , Stricker Florian , Kressler Jörg , Okuda Jun , Mülhaupt Rolf
Published: March 2011

Recent advances in transition metal catalyzed olefin polymerization and melt processing stimulate the production of new polymers derived from old monomers. Modern polyolefin processes do not require polymer purification and give excellent control of molecular and supermolecular polyolefin architectures. Progress in catalyst design and preparation of tailor‐made homo‐and copolymers is highlighted for isotactic, syndiotactic, atactic and stereo‐block polypropylene (PP), novel 1‐olefin copolymers, and ethylene copolymers with polar monomers, e.g., CO and acrylics. Today polyethylene short‐and long‐chain‐branching is controlled either by uniform ethylene copolymerization with 1‐olefins using single‐site” metallocene catalysts, or by migratory polyinsertion of ethylene, respectively. Stiff cycloaliphatic polymers expand the frontiers of polyolefins into engineering applications. New families of polyethylenes and EPM with pendent polypropylene chains are obtained via copolymerization of PP macromonomers or polymer‐analoguous coupling of functionalized PP during melt processing.
Surface modification of polyolefins by photografting of acrylic monomers
Authors: Decker C. , Zahouily K.
Published: March 2011

High‐speed surface modification of polypropylene (PP) and polyethylene (PE) films has been achieved by liquid phase photograft polymerisation of acrylic acid (AA) and hydroxypropyl acrylate (HPA). Benzophenone was used as photoinitiator to generate polymer radicals at the surface of the polyolefin film. The grafting reaction was carried out in aqueous solution or with the neat monomer, which was laminated between two PP films, in the presence of air. Under the intense illumination of a UV‐curing line, acrylic acid was grafted within seconds to polypropylene films or fabrics, which were thus made hydrophilic. Direct evidence of surface grafting was obtained through infrared spectroscopy analysis and surface energy measurements. This continuous photografting process proved to be very efficient to improve the adhesion of UV‐cured acrylate coatings on polyolefin‐made materials.
The role of pyridine derivatives in living carbocationic polymerization: Lewis base or nucleophile?
Authors: Bae Young Cheol , Faust Rudolf
Published: March 2011

The living cationic polymerization of isobutylene induced by the 2‐chloro‐2,4,4‐trimethylpentane/TiCl4/hexane:methyl chloride (60:40, v:v)/‐80°C system was studied in the presence of pyridine derivatives. Protic initiation, substantial in the absence of these additives, was virtually eliminated in their presence, and polyisobutylenes with controlled molecular weight and narrow molecular weight distribution were obtained. With some additives, however, proton elimination occurs, resulting in the exclusive formation of the exo olefin. The rate of elimination is independent of monomer concentration, i.e., it occurs during and after the polymerization. Results suggest that the proton elimination is due to the presence of an uncomplexed base, especially when complex formation with TiCl4 is hindered by steric compression, but its approach of the polymer cation is not fully blocked.
Alkyl chloride‐boron trichloride initiated polymerizations of isobutylene: Detailed analysis of the initial propagation steps
Authors: Mayr Herbert , Roth Michael
Published: March 2011

Living oligomerizations of isobutylene initiated either by cumyl chloride, the [1:1]‐adduct of cumyl chloride to isobutylene (P), the [1:2]‐adduct of cumyl chloride to isobutylene (P2), diisobutylene hydrochloride (P1'), or triisobutylene hydrochloride (P2') have been studied in presence of BCl3 and benzyltriethylammonium tetrachloroborate. In contrast to common opinion, the gross propagation rates of the various telechelics depended significantly on the degree of polymerization with krel = 0.07, 1.8, 2.3, 1.3, 1.1, 1.0, 1.0 for Ph‐C(CH3)2‐[CH2‐C(CH3)2]n‐Cl with n = 1, 2, 3, 4, 5, 6, 7, respectively. These results are compared with the initiation efficiencies of (CH3)3C‐(CH2‐C(CH3)2]n‐Cl (Krel = 0.3 and 0.8 for n = 1 and 2, respectively). The consequences for the synthesis of telechelics with very narrow molecular weight distribution are discussed.