bluuebunny/crossref_metadata_2025 huggingface dataset:
Topological nanoinhomogeneities in polymer networks
Authors: Dušek Karel , Šomvársky Ján
Published: March 2011

Small‐size topological inhomogeneities in polymer networks characterized by differences in composition are formed as a consequence of history‐determined covalent linking of units differing in some property into chemical clusters (topological inhomogeneities). This process is possibly assisted by physical association (segregation) of units of different types. Evolution of hard clusters in mixtures of long and short chains crosslinked with a common crosslinking agent and multicomponent polyurethane networks have been treated as examples of evolution of topological inhomogeneities. Simple mean‐field models based on the statistical theory of branching processes (TBP) have been developed for modelling of the topological inhomogeneities (molecular weight averages, functionality averages, percolation threshold, etc.) in dependence on initial composition, reactivities of the functional groups, or history of network formation. Such characterization was possible by distinguishing bonds between e.g. soft‐soft, soft‐hard, and hard‐hard units. More sophisticated models view inhomogeneities formation as a kinetic process where effective reactivity of functional groups in reactions, by which inhomogeneities are formed, depends on the size and composition of a given chemical cluster. This model is based on Monte‐Carlo simulations of the generalized Smoluchowski coagulation process.
Pseudo interpenetrating polymer networks and interpenetrating polymer networks of zeolite 13 X and polystyrene and poly(ethyl acrylate)
Authors: Frisch Harry L. , Xue Yong‐peng , Maaref Shahin , Beaucage Gregory , Pu Zhengcai , Mark James E.
Published: March 2011

Free‐radical polymerization of liquid styrene and ethyl acrylate with or without ethylene dimethacrylate crosslinker in the presence of zeolite 13 X produces interpenetrating polymer networks (IPN's) or pseudo IPN's in which polymer chains have grown and filled internal pores of the zeolite. A variety of methods of characterization including, solubility studies, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), 13C solid‐state nuclear magnetic resonance (NMR) and small‐angle X‐ray scattering (SAXS) provide supporting evidence for this. The polymer chains within the internal pores do not exhibit a bulk glass transition. This is part of a larger study of the glass transition of polymers confined to cavities or pores of various sizes.
Morphology and domain size of a model graft copolymer
Authors: Matsushita Yushu , Noda Ichiro
Published: March 2011

We prepared well‐defined styrene (S)‐2‐vinyl‐pyridine (P) graft copolymers of the ABB type or SPP graft copolymers, in which as block chain is grafted at the center of a block chain, as a model graft copolymer by anionic polymerization and coupling reaction. The composition dependence of morphology of SPP graft copolymers is qualitatively the same as that of SP diblock copolymers, but the composition range of each structure is shifted to the higher volume fraction of S block chain. The molecular weight dependence of lamellar domain size of SPP graft copolymers is almost the same as that of SP diblock copolymers, but the magnitudes are smaller. These experimental results are well explained by the difference in chain architectures.
Composites obtained via matrix and pseudo‐matrix processes (polymerization and new phase formation)
Authors: Papisov Ivan M. , Litmanovich Andrey A. , Bolyachevskaya Klavdiya I. , Yablokov Yuriy S. , Prokofev Aleksandr I. , Litmanovich Ol'ga Ye. , Markov Sergey V.
Published: March 2011

A variety of composites comprising complexes between macromolecules and growing species such as macromolecules or particles may be prepared using matrix or pseudo‐matrix processes. Matrix polycondensation of silica acid in the presence of poly(ethylene glycol) and other polymers in benzene resulting in formation of interpolymer complex (IPC) poly(silica acid)‐matrix or composites including the IPC is regarded as an example of matrix processes providing the possibility to synthesize an IPC or composite which cannot be (or hardly may be) obtained by other ways:

Theoretical aspects of pseudo‐matrix processes in which pseudo‐matrix macromolecule recognizes (i.e., forms a complex with) a particle of forming new phase and terminates its subsequent growth are discussed. Experimental data dealing with reduction of Ni(II) in polymer solutions and formation of nano‐composites ‘polymer ‐ metallic nickel’ including small particles (3–5 nm in diameter) with narrow size distribution are presented.
The topological structure of hypersurfaces of conformational energy levels and physical mechanisms of the internal mobility of proteins
Authors: Shaitan Konstantin V.
Published: March 2011

The interrelationship between the general characteristics of structure of biopolymer conformational energy hypersurface and possible mechanisms of conformational movements and elementary acts of functional processes is considered. The fundamental principle underlying regulation and control within biological systems at the macromolecular level are discussed. A new approach to modeling the dynamics of functional processes is proposed.
Effect of tertiary diamines on anionic polymerization of polar vinyl monomers
Authors: Marchal Jérǒme , And Yves Gnanou , Fontanille Michel
Published: March 2011

Tertiary diamines that exhibit chelating capability to lithium are shown to decrease the reactivity of growing species when used in classical anionic polymerization of methacrylic monomers. Out of the different diamines investigated, sparteine turns out to be the most efficient chelating agent. The beneficial effect of the latter additives on the overall reactivity of methacrylic anions was exploited to prepare poly(MMA) samples of controlled size at room temperature. The decrease in reactivity was also demonstrated from a kinetic point of view, upon measuring the actual rate constant of propagation using vinyl pyridine as model monomer.
The synthesis and cationic polymerization of novel monomers from renewable sources
Authors: Crivello James V. , Narayan Ramesh , Bratslavsky Svetlana A. , Yang Bo
Published: March 2011

This communication describes recent developments in this laboratory directed towards the design of cationically polymerizable monomers from biorenewable sources. Three classes of ubiquitous biorenewable substrates were explored, namely: lipids, carbohydrates and terpenes. Considered in the synthesis and design were the cost and availability of the substrates, and the practicality and environmental acceptability of the chemical methodology. The polymerizations of the monomers were carried out using photoinitiated cationic polymerization.
Modelling carbocationic polymerizations: Kinetics of the reactions of carbocations with alkenes
Authors: Mayr Herbert , Patz Matthias
Published: March 2011

Reactions of carbocations with olefins and related π‐nucleophiles follow second order kinetics, first order with respect to carbocation and first order with respect to olefin. The rate constants are equal for paired and non‐paired ions and independent of the nature of the negative counter‐ions. Rate constants k < 107‐108 L mol−1 s−1 can be calculated by lg k(20 °C) = s (N+E), where E represents the strengths of the electrophiles, while nucleophiles are characterized by the slope parameter s and the nucleophilicity parameter N. These parameters can be used for selecting initiators for carbocationic polymerizations and for designing copolymers.
Design of latent catalysts and their application to polymer synthesis
Authors: Endo Takeshi , Sanda Fumio
Published: March 2011

Design of latent catalysts such as benzyl sulfonium, benzyl ammonium, benzyl pyridinium, benzyl phosphonium, and hydrazinium salts, and their application to polymer synthesis have been described. They have been demonstrated as excellent thermal or photolatent catalysts for polymerizations of cyclic monomers such as epoxides, bicyclo orthoesters, spiro orthocarbonates, and vinyl monomers such as styrene and vinyl ethers.
Well defined polymer structures by ionic ring‐opening polymerization of cyclic monomers comprising the respective structure
Authors: Keul Helmut , Melchiors Martin , Neffgen Stephan , Gotsche Michael , Höcker Hartwig
Published: March 2011

Ring‐opening polymerization of cyclic monomers is the method of choice when tailor‐made polymers and copolymers with heteroatoms in the main chain are to be prepared. Triblock copolymers comprising a poly(ethylene oxide) block [poly(EO)] and two poly(2,2‐dimethyltrimethylene carbonate) blocks [poly(DTC)] were prepared using a telechelic poly(EO) as initiator for the DTC polymerization. These block copolymers dissolve suitable salts leading to solid polymeric electrolytes. The thermal properties and the ionic conductivity of these materials are presented. Block copolymers comprising a poly(tetrahydrofuran) block [poly(THF)] and a poly(trimethylene urethane) block [poly(TU)] were obtained by sequential cationic polymerization of THF and TU with methyl trifluoromethane‐sulfonate as initiator. Mechanistic and kinetic aspects of the TU polymerization are discussed. To achieve the synthesis of block copolymers with a poly(L‐lactide) block [poly(LLA)] and a poly(α‐amino acid) block [poly(AA)] amino‐terminated poly(LLA) was prepared which served as initiator for the polymerization of α‐amino acid N‐carboxyanhydrides.
Use of polyiminophosphazene bases for ring‐opening polymerizations
Authors: Eßwein Beate , Molenberg Aart , Möller Martin
Published: March 2011

The polyiminophosphazene bases Et‐P2 and t‐Bu‐P4 were used as a promoter for ethylene oxide and siloxane polymerizations. Initiation by an alcohol in combination with t‐Bu‐P4 lead to an extremely rapid polymerization reaction of octamethylcyclotetrasiloxane. In the case of ethylene oxide, well‐defined polymers were obtained, however the rate of polymerization decreased during the polymerization reaction due to decomposition of the counterion. In combination with organolithium compounds, the phosphazene bases lead to well‐defined polymers in the case of cyclotrisiloxanes as well as in the case of ethylene oxide.
Polymers and european union research funding
Authors: Quivoron Claude
Published: March 2011

The 4th Framework Programme for Research and Technological Development (4th FPRTD) of the European Union was adopted in April 1994. It has a duration of five years (1994‐1998) and a global budget of at least 12,300 MECU. The 4th FPRTD contains 15 sectorialized specific programmes (First Activity) and 3 interdisciplinary ones (Second, Third and Fourth Activities). Polymer Science has no specific programme but can be partially found in some of them. It will be given, in this paper, the main lines of the specific programmes where polymers are involved.
Some peculiarities of the surface chemical modification of the high‐dispersed silica fillers
Authors: Tertykh Valentin A.
Published: March 2011

Advantageous routes of preparation of dense hydrophobic coverings on the silica surface are discussed. An analysis of the experimental data allows to realize the optimum choice of modifying reagents and catalysts for the surface reactions. Possibilities of the use of solid‐phase hydrosilylation reactions for this purpose are examined.
Rheology of highly filled polypropylene compounds: Measurement and applications
Authors: Gahleitner Markus , Bernreitner Klaus , Knogler Bernhard , Neißl Wolfgang
Published: March 2011

It is common knowledge among rheologists as well as polymer engineers that compounds of thermoplastics with a high volume content of mineral fillers show a viscoelastic behaviour which is significantly different from homogeneous systems. A strong nonlinearity is combined with the development of a second plateau region of the dynamic moduli at lower frequencies. This for one makes the rheological characterization of these materials more complicated, as could be shown in a round robin test, including a PP‐compound with talc. The linearity criterion has to be handled carefully to achieve comparable and representative results. However, the viscoelasticity gives access to a quick characterization method regarding dispersion quality in compounds. This can be shown for the case of PP‐talc‐compounds, where correlations between relaxation spectrum and impact strength could be developed.
Particle filled polyolefins with high stiffness and toughness, as used for load bearing components
Authors: Savadori Aurelio , Scapin Marco , Walter Rolf
Published: March 2011

Mineral fillers have been used very often in the past for improving elastic modulus and temperature resistance of polyolefines, also to the detriment of impact resistance. Very recently it has been pointed out that good fracture toughness can be achieved if an appropriate mechanism is stimulated and a good bonding of the filler particles to the matrix is guarantied.

This work shows some interesting results obtained in this field with HDPE (high density polyethylene) and kaolin. In particular the effect of filler content and of adhesion between matrix and filler is considered. A comparison is also made with literature data concerning filled polyolefines (HDPE and PP).
Comparison of electrically conductive fillers in polymer systems
Authors: Kozlowski Marek , Kozlowska Anna
Published: March 2011

A comparative evaluation of different carbon black grades was performed for polymer composites whose matrices were composed of a single polymer, or polymer blend. The electrical resistivity, rheological properties, tensile strength and morphology were evaluated. The highest conductivity level was measured for the composites with Ketjenblack EC 600 JD from Akzo Nobel.
A qualitative study to the influence of molar mass on retention in gradient polymer elution chromatography (GPEC)
Authors: Klumperman Bert , Cools Paul , Philipsen Harry , Staal Wim
Published: March 2011

Gradient Polymer Elution Chromatography (GPEC) appears to be a powerful method for the determination of chemical composition distributions (CCD) of high molar mass copolymers. In order to perform these experiments, molar mass dependence of the retention time must be minimized. It is shown that variation in solvent and non‐solvent strength is a powerful method for adjusting the molar mass dependence. There appears to be a relation between molar mass dependence of retention behavior in GPEC on one hand and solubility under critical solvent conditions on the other hand. This phenomenon can be explained qualitatively from the important precipitation/redissolution mechanism in GPEC.
Crystaf: Crystallization analysis fractionation. A new approach to the composition analysis of semicrystalline polymers
Authors: Monrabal Benjamin
Published: March 2011

Crystallization Analysis Fractionation is a new technique for the analysis of composition distribution in semicrystalline polymers; more specifically for the analysis of branching distribution in Polyethylene and tacticity in Polypropylene type resins. CRYSTAF as well as TREF (Temperature Rising Elution Fractionation) are separation techniques which fractionate species of differing crystallizability by slow cooling of a polymer solution. TREF however, demands in addition to the crystallization step a second temperature cycle, elution step, to obtain the polymer composition. CRYSTAF, on the other hand, extracts the information in the crystallization cycle by monitoring the solution concentration depression as temperature goes down; thus reducing significantly the analysis time and simplifying the hardware needs. CRYSTAF principles are discussed and various applications are described.
Inverse size exclusion chromatography and universal calibration
Authors: Potschka Martin
Published: March 2011

The mechanism of size‐exclusion chromatography (SEC) is reciprocal in respect to the properties of the porous material and of the solutes immersed. The porosimetric interpretation (inverse SEC) yields information about the morphology of porous solids. It depends on a number of assumptions and in particular on the steric properties of the probing macromolecules whose ‘Universal Calibration’ remains disputed to this day. The central question concerns the equilibrium distribution of molecules in confined spaces of complex geometry, and is, as such, not limited to the particulars of chromatographic technique. This survey hopes to help focus future research activities in this field of analytical chemistry and material science.
New aspects of determination of polymer heterogeneity by 2‐Dimensional orthogonal liquid chromatography and maldi‐tof‐ MS
Authors: Krüger Ralph‐Peter , Much Helmut , Schulz Günter , Wachsen Olaf
Published: March 2011

Liquid Adsorption Chromatography at Critical Conditions (LACCC) of polymers in combination with Matrix‐Assisted Laser Desorption / Ionization Time‐Of‐Flight Mass Spectrometry (MALDI‐TOF‐MS) and different types of detectors is a very convenient method for the characterization of polymer heterogeneities. A pathway for working out these methods is given. Additionally to the coupling of different chromatographic modes a device for post‐column reaction detection is described and applied. Examples of applications are given for aliphatic and aromatic polyesters. MALDI‐TOF‐MS, reaction detection and relations between “critical” solvent composition and structure of polyesters are discussed. Conclusions concerning the mechanism of thermal degradation of polylactides are shown.
Characterization of polyethers using different methods: SFC, LAC and SEC with different detectors, and MALDI‐TOF‐MS
Authors: Trathnigg Bernd , Maier Bernhard , Schulz Günther , Krüger Ralph‐Peter , Just Ulrich
Published: March 2011

Polyethylene glycol 300 (PEG 300) and polypropylene glycol 425 (PPG 425) were analyzed using size exclusion chromatography (SEC) in different solvents, normal and reversed phase liquid chromatography (NPLC and RPLC), supercritical fluid chromatography (SFC), and matrix‐assisted laserdesorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). In liquid chromatography, different detectors were used: density, refractive index (RI) and evaporative light scattering detector (ELSD).
First‐principles prediction and interpretation of propagation and transfer rate coefficients
Authors: Heuts Johan P. A. , Sudarko  , Gilbert Robert G.
Published: March 2011

Propagation and transfer rate coefficients in free‐radical polymerizations are calculated from first principles, using quantum calculations (both ab initio and semi‐empirical) to determine geometries, frequencies, torsional potentials and energies of reactants and transition state, after which transition state theory yields the Arrhenius parameters. While activation energies can only be calculated for small species and with large computational resources, acceptable frequency factors (A) are obtained with relative ease provided that lower frequencies corresponding to torsions are treated as hindered rotors, not harmonic oscillators; this entails finding the torsional potential and exact evaluation of the corresponding partition function. Simple theory can be used to find A because this involves a ratio of partition functions of reactant and transition state, and because torsions (which are dominated by geometrical considerations) dominate A. A is determined by three modes in the transition state: rotation of the monomer about the forming bond, rotation of a “propylene”‐group about the terminal C–C bond in the radical, and simultaneous bending of the two angles associated with the forming bond. Calculations on ethylene and acrolein give agreement with experiment. These studies explain some experimental observations. (i) Changing the penultimate unit gives a small but significant change in the torsion of two of the three modes dominating A, leading to a penultimate‐unit effect of ca. a factor of 1–10. (ii) Deuteration affects the moments of inertia of the torsions, leading to changes in A in accord with experiment. (iii) A, but not the activation energy, changes predictably along a homologous series (e.g., methyl, butyl methacrylate). (iv) For a given monomer, A's for transfer to monomer and propagation are similar.
Applications of esr techniques to the study of free radical processes and kinetics in acrylic polymerizations
Authors: Chang Hsiu‐Rong , Lau Willie , Parker Hsing‐Yeh , Westmoreland David G.
Published: March 2011

Electron spin resonance (ESR) techniques have been applied to a detailed study of batch and semicontinuous emulsion polymerization of methyl methacrylate; butyl acrylate and styrene have been briefly studied. Quenching of samples from the polymerization reactor followed by ESR analysis are useful, but we have developed continuous flow techniques which are preferable in many cases. ESR techniques can provide valuable information relating to the nature of free radical reactions, the concentration of propagating free radicals, and the kinetic processes in these reactions. Direct ESR analysis is most valuable but is not applicable to all systems. Spin trapping techniques can be useful for systems not accessible by direct analysis.
Studies in free radical initiation
Authors: García‐Rubio L. H.
Published: March 2011

In this paper, the consequences of the standard assumptions made in free radical initiation are explored to explain effects that could be attributed to the kinetics of initiation. Experimental results based on end‐group analysis through the course of bulk and suspension polymerizations demonstrate the importance of reactions involving initiator molecules. Studies on the combined effects of mixing and initiator decomposition, and oxidation reduction systems further demonstrate the importance of an adequate description of free radical initiation mechanisms.
Molecular modeling of phase behavior of polymer blends
Authors: Freed Karl F. , Dudowicz Jacek
Published: March 2011

Recent advances in the lattice cluster theory are applied to describe polymer blend miscibilities and variations with pressure. Extensive comparisons are made with experiment.
Estimating interactions in blends of polyamides, polyesters and polycarbonate using copolymers
Authors: Ellis Thomas S.
Published: March 2011

A binary interaction model (BIM), formulated in terms of elementary chemical species, e.g., ‐ CH2 ‐, ‐COO‐, is applied to blends of homopolymers and copolymers composed of polyamides, polyesters and polycarbonate. By establishing interactional “null” points it is shown how estimates of the interactions, both favorable and unfavorable, between the blend constituents can be obtained. The predictive potential of the parameters derived is examined in various situations, such as blends of PA‐66/PET.
Morphology resulting from coupling of phase separation and glass transition in polymer blends
Authors: Danchinov S. K. , Shibanov Yu. D. , Godovsky Yu. K.
Published: March 2011

At temperatures near glass transition temperature, off‐critical binary polystyrene/polybutadiene (PS/PB) mixtures were found to experience phase separation through the mechanism of slow hydrodynamic coarsening. A bicontinuous phase structure was produced on quenching the PS/PB‐blends under cloud point curve. Different coarsening regimes of this percolation structure depending on degrees of supersaturation were found. At late stages of coarsening, secondary phase separation was observed.
Numerical simulation of distributive mixing in 3‐D flows
Authors: Avalosse Thierry
Published: March 2011

A numerical simulation is performed for analysing the mixing of the stirring tank. The influence of the stirring tank geometry and of the Reynolds number is investigated. Statistical tools are used for predicting the evolution of quantities such as area stretch and global mixing efficiency.
Studies on the compatibilization between polyamide and poly(arylether sulfone)
Authors: Mäder Dietmar , Kressler Jörg , Weber Martin
Published: March 2011

The influence of functionalized poly(arylether sulfone)s on the adhesion of a poly(arylether sulfone) and a polyamide was studied using a fracture test of sandwich specimens. All reactive compatibilizers used improve the interfacial adhesion. The chemical reaction at the interface between a maleic anhydride grafted polysulfone and a polyamide was analyzed by X‐ray photoelectron spectroscopy. Differing crack propagation mechanisms at the interface were observed by optical microscopy during the fracture test for the reactive and non‐reactive systems. Furthermore, the fracture surfaces were studied by optical and atomic force microscopy. Using transmission electron microscopy on ultrathin sections taken across the interface, it could then be shown that the interface was reinforced by the chemical reaction of maleic anhydride grafted polysulfone with the polyamide. The non‐reactive system fails at the weak interface, whereas strongly reinforced samples show cohesive failure in the polyamide bulk phase.
Small‐angle X‐ray scattering studies on plastically deformed rubber‐modified polystyrene
Authors: Magalhães Arminda M. L. , Borggreve Rein J. M.
Published: March 2011

The deformation process of blends of polystyrene (PS) and rubbery block copolymers based on polystyrene and hydrogenated polybutadiene (SEBS, Shell Kraton G1651)was studied by Transmission Electron Microscopy (TEM) and Small‐angle X‐ray Scattering (SAXS) on deformed tensile samples, under loaded conditions. When the rubber concentration is increased the impact toughness as well as the elongation at break Increases while the SAXS studies show that the amount of crazing decreases. TEM studies suggest that the main deformation mechanism in these materials is cavitation‐induced shearing. When a crazing agent is incorporated in the disperse phase of rubber‐modified PS the amount of crazing increases more than four times, but the toughness decreases dramatically.
In‐situ preparation of graft copolymers
Authors: Hellmann G. P. , Walter M. , Dietz M. , Steurer A.
Published: March 2011

Graft copolymers are closer to supermolecular structures than any other class of polymers. Most grafting reactions proceed in demixed blends or lead in situ to such blends The competition of chemical chain coupling and physical phase separation generates complex phase morphologies that cannot (or not so directly) be produced otherwise. To demonstrate potential and problems of graft copolymer systems, high‐impact thermoplastics, block‐graft copolymers and reactive blending are discussed.
Roles of polymer‐solvent complexes in conformational ordering of polymer molecules dispersed in gels
Authors: Kobayashi Masamichi
Published: March 2011

On gelation of crystallizable stereoregular polystyrenes (isotactic IPS and syndiotactic SPS), highly ordered skeletal conformations of particular types characteristic of the respective polymer are formed. The conformational orderliness is evaluated in the absolute scale through quantitative analysis of infrared absorption bands due to the respective ordered conformation. The kinetic and/or thermodynamic behaviors of gelation process and the accompanied conformational ordering are strongly influenced by solvent. Solvent effect on the aggregation state formed in SPS gels has been investigated by means of small angle neutron scattering and discussed in relation to the gelation rate. In some solvents, two different ordering processes, gelation and crystallization, proceed in a competitive way. On the basis of these experimental facts, the roles of specific polymer‐solvent interactions in gels are considered from the viewpoint of molecular‐level structure.
Multi‐functional coordination crosslinks in poly(vinylamine) complexes with cobalt chloride
Authors: Belfiore Laurence A. , Indra Erik , Das Pronab
Published: March 2011

Poly(vinylamme) complexes with cobalt chloride hexahydrate exhibit the largest glass transition temperature enhancements that have been measured in this laboratory. Tg increases from 56°C in the undiluted polymer to 193°C when the molar concentration of cobalt is only 3%, based on the moles of polymeric repeat units. This translates to a 45°C enhancement in Tg per mol% cobalt. Higher glass transition temperatures have been measured for other polymeric complexes with d‐block salts, but this study reports the largest ΔTg=Tg(complex)‐Tg(undiluted polymer) when transition‐metal catalyzed chemical crosslinking reactions do not occur. A plausible explanation for this effect is based on the fact that cobalt chloride hexahydrate maintains pseudo‐octahedral symmetry in the undiluted crystalline state and in an amorphous glassy complex with the polymer. The lone pair on nitrogen in the amino sidegroup is a strong base and, most likely, displaces all four waters of hydration that coordinate directly to the metal center. In fact, estimates of the ligand field splitting and the ligand field stabilization energy for octahedral cobalt complexes that contain methyl amine (CH3NH2) model ligands suggest that five or six amino sidegroups from several different chains might coordinate to each metal center, drastically reducing the mobility of the polymer. Both chloride anions remain near each divalent Co2+ center, but either one or two Cl− might not reside in the first‐shell coordination sphere of the transition metal. This bonding picture suggests that octahedral cobalt acts as a multi‐functional bridge between five or six amino sidegroups. Empirical ligand field stabilization calculations support the concept that octahedral Co2+ is a multi‐functional coordination crosslinking agent, and the inorganic literature provides experimental verification that similar small‐molecule complexes (i.e., [Co(NH3)6]2+) exist. It is proposed that the onset of Tg occurs when sufficient thermal energy is supplied to remove either x or (x‐1) amino sidegroup ligands from the coordination sphere of cobalt, where x is either 5 or 6. This is an endothermic process based on bond energies, as well as calculations which focus on the relative energies of the metal d‐electrons.
Lamellar structure of poly(ethylene oxide) molecular complexes
Authors: Dosière M.
Published: March 2011

The phase diagrams of some binary systems such as poly(ethy lene oxide)‐p‐dihalogenobenzene, poly(ethylene oxide)‐resorcinol and poly(ethylene oxide)‐p‐nitrophenol show the existence of molecular complexes with a well definite stoichiometry. The crystal structure of these molecular complexes has been determined by wide‐angle X‐ray diffraction. The morphology of these molecular complexes crystallized from the melt is investigated by differential scanning calorimetry and small angle X‐ray scattering. PEO‐p‐dichlorobenzene and PEO‐resorcinol complexes crystallize from the melt as extended chains (EC) or integral folded chain (IFC) lamellar crystals. As observed for PEO oligomers, the fraction of EC crystals of PEO‐resorcinol increases with the crystallization temperature. However EC crystals are present in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO‐p‐nitrophenol complex crystallizes over all the studied crystallization temperature range as stable non integral folded chain (NIFC) crystals. Explanations related to the crystal structure of these complexes and to their mode of growth are invoked to explain these two deeply different lamellar morphologies.
Local microstructure dependence of PVC interaction with solvents. A FTIR verification
Authors: Gómez‐Elvira J.M. , Tiemblo P. , Martínez G. , Millán J.
Published: March 2011

The occurrence of local configuration based PVC‐solvent interactions, specifically, is demonstrated by studying, first, the changes in FTIR frequency of both the solvent carbonyl band and the PVC C‐Cl stretching bands with the composition of PVC‐solvent mixtures; and, secondly, the FTIR dichroic behaviour of the same bands upon stretching PVC films containing traces of solvent. The latter turns out to be an original path to investigate polymer interactions.
Drawing behaviour of syndiotactic polystyrene (sPS)
Authors: Daniel C. , Guadagno L. , Vittoria V.
Published: March 2011

The drawing behaviour of amorphous and solvated structure of syndiotactic polystyrene has been analysed. By means of X‐ray analysis and infra‐red spectrometry we have studied the conformational transitions induced by the drawing processing.
Order ‐ disorder transitions in comb‐like polymer‐surfactant systems involving hydrogen bonds
Authors: ten Brinke Gerrit , Huh June , Ruokolainen Janne , Torkkeli Mika , Serimaa Ritva , Ikkala Olli
Published: March 2011

Conditions to obtain micro‐phase separated morphologies in polymer‐surfactant systems involving hydrogen bonds have been investigated using poly(4‐vinyl pyridine) (P4VP) and surfactants capable of forming hydrogen bonds of different strength with the basic nitrogen of P4VP. Depending on the tail length, the hydrogen bonding strength, the amount of surfactant and the temperature, four different regimes have been identified: I. Micro‐phase separated state, II. Homogeneous state exhibiting a distinct Small Angle X‐ray Scattering (SAXS) peak, III. Homogeneous state without a SAXS peak and, IV. Macro‐phase separated state. Time‐resolved SAXS / W(ide) A(angle) X(ray) S(cattering) / D(ifferential) S(canning) C(alorimetry) as well as rheological measurements are used to identify the different regimes. A simplified model description together with preliminary computer simulation results are presented.
PVC photo‐oxidative degradation: Identification of volatiles
Authors: Krzymien Marek E.
Published: March 2011

Volatile products present in poly(vinyl chloride), PVC, after outdoor weathering have been compared with volatiles from laboratory, UV exposed PVC surfaces. Compounds both present in the photo‐degraded polymer surface layer and directly emitted from the polymer were measured in the laboratory experiments. The hydrocarbons, oxygenated compounds and chloro‐organic species were measured and identified by capillary gas chromatography with a mass spectrometer detector.
Highlights in chemistry and physics of polymer stabilization
Authors: Pospíšil Jan , Nešpůrek Stanislav
Published: March 2011

Deactivation of free radicals, hydroperoxides and harmful solar radiation are the principal mechanisms increasing stability of commodity and engineering polymers. The stabilization process is accompanied by transformations of individual additives. New compounds influence specifically the integral protecting mechanism. Products contributing to the stability are most beneficial. Mechanistic data are used for optimisation of the inherent chemical efficiency and physical persistence and for explanation of deactivation of stabilizers.
Charge transfer states in the photophysics and photochemistry of polyimides and related phthalimides
Authors: Creed David , Hoyle Charles E. , Jordan John W. , Pandey Chandra A. , Nagarajan Rajamani , Pankasem Surapol , Peeler Alline M. , Subramanian Petharnan
Published: March 2011

Polyimides such as 6F‐6F and 6F‐ODA and model N‐arylphthalimides are stabilized against photooxidative degradation by their electron donor (D) – acceptor (A) character. We have investigated the precise origin(s) of this effect using D and A substituents on the N‐aryl groups of these compounds. The lowest excited singlet state (S1) of N‐arylphthalimides is an intramolecular charge transfer (ICT) state. A nominally twisted compound, N‐(2‐t‐butylphenyl)phthalimide, shows greatly diminished CT absorption and blue‐shifted fluorescence with reduced quantum yield when compared to the 4‐t‐butyl isomer with an identical N‐aryl donor group. It therefore seems unnecessary to claim that the ICT state of phthalimides is a so‐called TICT state. Quantum yield and fluorescence lifetime measurements lead to the conclusion that enhanced internal conversion from the ICT state (S1) to the ground state makes a significant contribution to photostabilization of these compounds by suppressing formation of the reactive triplet state. Further stabilization of polymer films may be afforded by triplet state self‐quenching which is enhanced for 6F‐ODA in increasingly poor solvents. N‐alkylarylphthalimides in which the aryl and phthalimide groups are not formally conjugated but, rather, joined by flexible methylene ‘spacers’, exhibit a different kind of fluorescent intramolecular CT singlet state whose formation can also stabilize these compounds by suppressing triplet state formation.
Nematic and smectic liquid single crystal elastomers: Influence of external stress parallel and perpendicular to the director
Authors: Kundler Isabel , Nishikawa Etsushi , Finkelmann Heino
Published: March 2011

The influence of uniaxial mechanical stress applied parallel or perpendicular to the director axis (optical axis) of nematic and smectic‐A elastomers having a permanent macroscopically ordered monodomain structure is investigated. Due to the different phase structures applying an external mechanical stress leads to completely different responses with respect to the young moduli and reorientation processes of the director. Nematic elastomers exhibit a weak anisotropy of the moduli parallel (μ11and perpendicular (μ) to the optical axis with μ11/ μ = 1.5. The moduli are mainly determined by the rubber elasticity of the poly(siloxane) network. Applying the mechanical stress perpendicular to the initial director axis causes a rotation of the director axis that is connected with a periodic pattern formation and a ‘soft elastic’ response. For smectic‐A elastomers μ11/μ is in the order of 102. While μ reflects a rubber elastic response similar to that of the nematic system, μ11indicates an enthalpy‐elastic behaviour of the one‐dimensional long range order of the smectic layers. In this direction reorientation of the phase structure with a deformation of the smectic layers occurs above a threshold elongation. In contrast to the nematic networks, a deformation perpendicular to the optical axis causes no director reorientation, displaying the liquid‐like properties within the smectic layers.
Photo‐controlled diffusion in reacting liquid crystals: A new tool for the creation of complex molecular architectures
Authors: Broer D.J. , Lub J. , Mol G.N.
Published: March 2011

Diffusion enforced photo‐assembling during polymerization of a chiralnematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross‐section of the film. The polarization selective reflection band of cholesterics can be made much wider than those of single pitch materials and may expand over the whole visible wavelength. The paper discusses the photo‐controlled diffusion process in thin films, the important process parameters and some of the properties of the molecular architectures obtained.
Ellipsoidal core‐shell cylindrical microphases in PS‐b‐PB‐b‐PCL triblock copolymers with a crystallizable matrix
Authors: Balsamo Vittoria , Stadler Reimund
Published: March 2011

Polystyrene‐block‐polybutadiene‐block‐poly(ϵ‐caprolactone) SBC triblock copolymers with a PCL matrix exhibit microphase separation into three different phases within the spherulitic superstructures. Mixing of the PS‐block can occur upon melting of the PCL‐block if the molecular weight is low enough. Even though the crystallization takes place well below the PS‐glass transition, a deformation of the amorphous microphases into ellipsoidal core‐shell cylindrical microdomains is observed by TEM. These copolymers have mechanical properties which are dominated by the PCL (poly(ϵ‐caprolactone)) matrix with an influence of the amorphous blocks.
Microphase separation in block CO‐ and terpolymers of novel macromolecular architectures
Authors: Sioula Stella , Tselikas Yiannis , Hadjichristidis Nikos
Published: March 2011

The synthesis of model miktoarm stars of the A2B, A3B, (AB)2(BA)2 and ABC (A:polyisoprene, B: polystyrene C: poly (methyl methacrylate)) was achieved by using anionic polymerization techniques and controlled chlorosilane chemistry. The microphase separation was studied by TEM, SAXS and image simulation. In the case of A2B and A3B miktoarm star copolymers, the morphology results are in agreement with the newly and after the experimental results developed theory of Milner. One of the symmetric in composition inverse block copolymers ((AB)2(BA)2) shows the OBDD morphology due to the special spatial arrangements of the arms. The first morphological results of ABC miktoarm star terpolymer show interesting future.
Mineralization of gold in block copolymer micelles
Authors: Möller Martin , Spatz Joachim P. , Roescher Arno , Mößmer Stefan , Selvan S. Tamil , Klok Harm‐Anton
Published: March 2011

Ultrasmall gold particles have been prepared inside the micelles of polystyrene‐block‐poly(ethylene oxide) and polystyrene‐block‐poly(2‐vinylpyridine) in toluene. Starting point was the formation of a thermodynamically stable dispersion of HAuCl4 or LiAuCl4 in the inverse micelles of the block copolymer which were treated with hydrazine or pyrrole. Analysis of the effect of the reduction agent on the stability of the micelles yielded a simple model for the transformation process involving coagulation of the swelling micelles. Kinetic control of the different steps, i.e., reduction, mineralization, coagulation, film formation, allowed to prepare thin films in which highly uniform gold particles were arranged in yet unknown order. When pyrrole was employed for the reduction, the gold monocrystals got embedded in a shell of polypyrrole.
Design of new macromolecular architectures by using quasi‐equivalent monodendrons as building blocks
Authors: Percec Virgil , Ahn Cheol‐Hee , Cho Wook‐Dong , Johansson Gary , Schlueter Douglas
Published: March 2011

Quasi‐equivalent building blocks are chemically identical subunits which self‐control their shape by switching between different conformational states. Classic biological examples are the flat‐tapered and conical protein coats which jacket nucleic acids during the self‐assembly of rod‐like and icosahedral viruses, respectively. This paper advances the hypothesis that monodendrons can act as synthetic quasi‐equivalent building blocks. The rational design of flat‐tapered and cone shaped quasi‐equivalent monodendrons and their use in the construction of three dimensional supramolecular and macromolecular rod‐like and spherical systems demonstrates the above hypothesis. Mechanisms which interconvert the spherical systems into rod‐like ones by using the same monodendron building blocks, thus demonstrating their quasi‐equivalence, will be exemplified.
Progress in the syndiotactic polymerization of styrene with metallocene/mao catalysts
Authors: Kaminsky Walter , Lenk Stephan
Published: March 2011

Metallocene/MAO catalysts are useful for the production of syndiotactic polystyrene ‐ a new class of high performance polymers. The melting point of the obtained syndiotactic polystyrene depends on the metallocene used and can reach up to 275 °C. In the past, the most active catalysts in polymerization have been half‐sandwich titanocenes such as CpTiCl3 and Cp*TiCl3. If the chlorinated compounds are changed into the fluorinated compounds as CpTiF3 and Cp*TiF3, the activity increases by a factor of 5 to 100. The fluorinated titanocenes are more stable at higher temperatures and need a lower MAO excess in order to obtain optimal activities.

Polymers obtained with the unsubstituted CpTiF3 show melting points which are 17 °C lower than those synthesized by pentamethylcyclopentadienyltitaniumtrifluoride. Especially Cp*TiF3 shows a much higher activity and, compared with the chlorinated compound, gives polymers with a higher molecular weight. Substituted cyclopentadienyltitanocenes have even higher activities. Ethene/styrene copolymers can be obtained by catalysis with zirconocene compounds.
Structures and properties of block copolymers in solution
Authors: Chu Benjamin , Liu Tianbo , Wu Chunhung , Zhou Zukang , Mark Nace V.
Published: March 2011

Structures and properties of block copolymers in solution depend on the total block length, the block length ratio, the block sequence and the solvent quality. The supramolecular structures formed by core/shell or flower‐like micelles in the concentrated solution region are examined by dynamic light scattering to ascertain some of the conditions which can enhance the formation of open associated structures using a triblock copolymer in a selective solvent for the middle block.
Toughened carbon fiber composites with morphology gradient
Authors: Kim Yu Seung , Kim Sung Chul
Published: March 2011

The morphology and fracture behavior of polyimide modified carbon fiber/dicyanate composites were analyzed. Composites having morphology gradient were prepared by inserting a polyimide film between prepregs of carbon fabric impregnated by dicyanate alone, and controlling the relative rate of dissolution of polyimide and the polymerization of dicyanate by adding zinc stearate catalyst. The composites having morphology gradient showed Gic and Giic values of 2.2 kJ/m2 and 1.4 kJ/m2 respectively, which showed 3–5 times of those values of unmodified carbon fiber/dicyanate composites.
Membrane microfiltration of oily water
Authors: Kim Jae‐Jin , Chinen A. , Ohya H.
Published: March 2011

Separation of oil in water emulsion was carried out by crossflow microfiltration using 3 types of microporous glass tubular membrane with different pore size of 0.27, 0.75, and 1.47 μm. The effect of pore size on permeate flux and oil rejection was investigated and the filtration mechanisms were analyzed based on various types of filtration models.
Measurement of anisotropic refractive indices of free‐standing polymer film
Authors: Lee Seung Won , Kwon Seon Young , Lee Hoosung
Published: March 2011

A new technique has been developed to measure the optical refractive indices in the parallel and perpendicular directions to the film surfaces and applied to measure the refractive indices of free‐standing polymer films. The refractive indices were obtained by measuring the reflectivity as a function of the incident angle. The angle dependence of the reflectivity which results from the interference of the light beam reflected from the front and rear interfaces of the film was analysed by means of the Fresnel equation. This technique can be used to measure the refractive indices in three major axes, i.e. one out‐of plane axis and two in‐plane axes of the sample. This technique gives values for the refractive indices and the thickness simultaneously with an accuracy comparable to that measured by optical wave‐guide technique. The validity of the technique has been tested with polymer films of known refractive indices such as poly(methyl methacrylate) and polyimide (PMDA‐ODA).
Thermosensitive hydrogel coatings: Synthesis and heparin release
Authors: Gutowska Anna , Kim Sung Wan
Published: March 2011

The synthesis and drug release properties of crosslinked N‐isopropylacrylamide (NiPAAm) copolymer coatings on the surface of a hydrophobic poly(ester‐urethane) tubing were examined. A method was designed to coat hydrophobic polymer surface with a thermosensitive gel layer. Crosslinked NiPAAm copolymer coatings were synthesized using UV‐initiated polymerization. The feasibility of using NiPAAm based gels as heparin releasing thermosensitive coatings was investigated. Heparin, a high molecular weight hydrophilic solute, was loaded into hydrogels using a simple solution sorption technique. The release of heparin from NiPAAm copolymer gel coatings was compared to that of crosslinked NiPAAm copolymers. The gel coatings demonstrated a more gradual and prolonged heparin release as compared to gel disks of the same composition.
Morphology and degradation behavior of aliphatic/aromatic copolyesters
Authors: Yoo Eui Sang , Im Seung Soon , Yoo Youngtai
Published: March 2011

Random and segmented block copolymers of Poly(tetramethylene succinate) (PTMS) and Poly(tetramethylene terephthalate) (PTMT) were synthesized and characterized regarding sequence distribution and crystalline parameters. Biodegradation behaviors of the copolyesters were examined in activated sludge and enzyme solution in terms of CO2 evolution. It was found that the initial degradation was strongly dependent on the crystallinity in the random copolymer. However, the chemical compositions become a dominant factor at the later stage of degradation. In the case of block copolymers, the biodegradation rate was most significantly affected by size and degree of perfectness of PTMS crystallites.