bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of phase transitions on the rheology of polymers
Authors: Winter H. Henning 
Published: March 2011

AbstractPolymeric materials near phase transition conditions exhibit some common features in their linear viscoelastic relaxation patterns. This has been shown by comparing several recent experimental studies of our laboratory. A universal pattern seems to evolve in the case of liquid‐to‐solid transitions such as chemical gelation, crystallization of semi‐crystalline polymers, and nematic to smectic transition in thermotropic liquid crystalline polymers. They all exhibit the self‐similar CW‐spectrum at low frequencies (for ω→0) or long times. Phase separating di‐block copolymers and polymer blends also show this same type of relaxation time spectrum, however, it most likely does not extend to ω→0 and it does not seem to be restricted to the close vicinity of the transition.
Uncommon methods for spectroscopic analyses of polymers
Authors: Brame Edward G. 
Published: March 2011

AbstractThe commonly used spectroscopic analyses of polymers include infrared (IR), nuclear magnetic resonance (NMR), mass(MS), x‐ray(XR), and the rapidly growing near infrared(NIR). The uncommon methods that are not frequently used include nuclear quadrupole resonance(NQR), electron spin resonance, and combination techniques such as gas chromatography‐infrared, thermal‐infrared, gas chromatography‐mass spectroscopy, and even thermal‐gas chromatography‐infrared or mass spectroscopy. The use of two of these methods (thermal‐infrared(TGA‐IR) and NQR is described. Appropriate examples are shown to point out how useful they can be.
Conformation, ordering and mobility of macromolecules in aromatic polyesters as studied by IR and solid‐state NMR spectroscopy
Authors: Koltsov A. I. , Kapralova V. M. , Khachaturov A. S. , Medvedeva D. A. , Shilov S. V. , Purkina A. V. , Volchek B. Z. , Skorokhodov S. S. , Zuev V. V. 
Published: March 2011

AbstractThermotropic main‐chain LC polyesters have been studied with the aid of IR and NMR spectroscopy. Rigid mesogens and mesogens with a possibility of conformational isomerism were examined. The dependence of the order parameters of the mesogens and spacers on the chemical structure of the polymer has been determined. The IR spectroscopy data and the data of the calculation of the possible conformations of the mesogen and the spacer confirm the theoretical predictions about the straightening of macromolecules in the anisotropic melt. Solid‐state 2H NMR spectra show that p‐oxybenzoic rings adjacent to a flexible spacer are more mobile than inner terphthalic rings. In decamethylene spacer the contrary holds true: the mobility of inner methylene groups is more marked than that of the α‐methylene groups bound to the mesogen.
Novel chemistry of β‐lactones anionic polymerization
Authors: Jedliński Zbigniew 
Published: March 2011

AbstractSome examples of novel chemistry of lactones polymerization are presented. New evidences on β‐lactones polymerization by akali metal alkoxides and, also unusual in organic chemistry, C‐C bond scission in β‐lactones polymerization induced by alkali metal supramolecular complexes are discussed. Preparation of functional polyesters and various block polymers exhibiting “tailored” properties are also described.
Thermodynamics and kinetics of ring‐opening polymerization of cyclic alkylene phosphates
Authors: Penczek Stanislaw , Duda Andrzej , Kaluzynski Krzysztof , Lapienis Grzegorz , Nyk Andrzej , Szymanski Ryszard 
Published: March 2011

AbstractPolymerization of cyclic compounds containing phosphorus has been used to prepare models of chains of nucleic acids and teichoic acids. Polymers of high molecular weight (M̄n≥105) have been prepared in the past in this laboratory by ring‐opening polymerization. These processes have a number of particular features, related to the low ring strain of the involved monomers (the majority of six‐membered esters are strainless) and to the presence of the labile exocyclic groups. Results of the studies of these polymerizations contributed to the understanding of general phenomena of ring‐opening polymerizations related to these features. In this review paper the thermodynamics of strainless rings is discussed. It is shown that for the same monomer, polymerization can either be exothermic (δHSS<0, δSSS<0) or endothermic, driven by positive change of entropy (δHSS>0, δSSS>0). The presence of the labile exocyclic groups introduce a potential possibility of chain transfer. It is shown that in the cyclic, non‐strained six‐membered monomers kP/ktr is relatively low for cyclic triesters but much higher (≈300) in the polymerization of cyclic amides, since the alcoholate is a better leaving group then the amide group. The importance of these findings for other classes of monomers (cyclic amines, siloxanes, orthoesters) having also labile exocyclic groups is discussed.
Ring opening polymerization of cyclic organosilicon compounds: Recent progress
Authors: Boileau Sylvie 
Published: March 2011

AbstractA novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes in toluene, in the presence of the cryptand [211]. Suitable conditions have been found in which monomodal distributions of molecular weights of polysiloxanes are observed by GPC, even in the case of D4 and 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinyl cyclotetra siloxane (D4Vi) polymerizations. Moreover, kinetics of propagation and of formation of cyclosiloxanes can be followed by 29Si or 13C NMR spectroscopy on living polymer solutions. The rate of propagation of hexaethylcyclotrisiloxane is 120 times lower than that of the corresponding dimethylated analog D3, under the same conditions.
Effect of ammonium polyphosphate on combustion and thermal degradation of aliphatic polyamides
Authors: Levchik S. V. , Costa L. , Camino G. 
Published: March 2011

AbstractChain fragments with amide and imide groups are the most abundant degradation products of aliphatic polyamides (APA) which derive from scission of the N‐alkylamide bond (‐CH2‐NH‐). In the case of polyamide 6.6 (PA‐6.6), also carbodiimide structures and methyl chain ends are formed, which derive from scission of ‐CH2‐C(=O)‐ bond. Cyclic compounds can be formed besides chain fragments, depending on the type of APA.Ammonium polyphosphate (APP) reacts with APA on heating forming phosphoric esters which decompose giving products similar to those obtained from pure APA. APP increases the yield of carbodiimides from PA‐6.6 which trimerise to triazine structures. The fire retardant mechanism of APP is discussed on the basis of the thermal degradation of the mixtures.
Flame‐resistant polynaphthoylenbenzimidazoles
Authors: Rusanov A. L. , Serkov B. B. , Bulycheva E. G. , Kolosova T. N. , Lekae T. V. , Ponomarev I. I. , Matvelashvili N. G. 
Published: March 2011

AbstractPolynaphthoylenebenzimidazoles, copolynaphthoylenebenzimidazolophenylquinoxalines and copolynaphthoylenebenzimidazolonaphthylimides were obtained by high‐temperature catalytic polycyclocondensation in phenolic solvents. All polymers obtained demonstrate high oxygen index values depending on polymers structure and naphthoylenebenzimidazole rings content in copolymers.
Polymer blends based on epoxy resin and polyphenylene ether as a matrix material for high‐performance composites
Authors: Venderbosch R. W. , Nelissen J.G.L. , Meijer H.E.H. , Lemstra P. J. 
Published: March 2011

AbstractThe application of poly(2,6‐dimethyl‐1,4‐phenylene ether), PPE, as a matrix material for continuous carbon fibre reinforced composites has been studied. Due to the intractable nature of PPE melt impregnation is not feasible and a novel impregnation route, using epoxy resin as a reactive solvent, was developed. The introduction of epoxy resin results in enhanced flow and a reduced processing temperature, enabling the processing of PPE and the preparation of high quality composites. Upon curing, phase separation is initiated and epoxy resin is converted into a second phase. In composites, epoxy resin preferentially accumulates at the polar fibre surface, resulting in an epoxy layer around the fibres, providing a high level of interfacial adhesion. For a high fibre volume fraction (> 50%) this results in the ultimate morphology of epoxy coated fibres in a neat PPE matrix. Due to this unique morphology the composite materials reveal outstanding mechanical properties in terms of interlaminar toughness and impact performance.
Crosslinked polyolefins as matrices for two‐phase materials
Authors: Chodák Ivan , Chorváth Igor 
Published: March 2011

AbstractThis paper gives a review of the results of investigation of the effect of crosslinking on the properties of LDPE/PPa) blends and LDPE filled with particulate silica. Tensile and impact properties, crystallization behaviour, crosslinked portion formation and crack growth rate have been investigated.Crosslinking results in an increased compatibility of originally incompatible LDPE/PP blends apparently due to an in situ formation of a compatibilizer, leading to improved deformability and better impact resistance. Changes in the morphology as revealed by crystallization behaviour, and the increased number of tie molecules in amorphous region due to crosslinking result in better impact resistance of LDPE/silica mixtures, as well as to the improvement of other properties of two‐phase materials, so as resistance to grack growth.
Synthesis of bisoxazolines and their application as chain extender for poly(ethylene terephthalate)
Authors: Loontjens Ton , Belt Wil , Stanssens Dirk , Weerts Pierre 
Published: March 2011

AbstractA synthetic method was found to prepare 1,2‐bis‐(2‐oxazolinyl‐2)ethane (BOXE) from succinonitrile and ethanolamine. Succinonitrile is a vicinal dinitrile, which forms with ethanolamine succinimidine. This imidine can be converted in good yield into the corresponding BOXE by heating it while stripping off the excess of ethanolamine.Bisoxazolines react with the carboxylic endgroups of PET, giving a strong increase in viscosity. The efficiency of this chain extension reaction depends on the structure of the bisoxazoline. BOXE gives a sharp rise in the viscosity of PET after 2.5 min at 270 °C. After prolonged heating the viscosity decreases again, even under the level of the blank. A mechanism is given which describes this unusual behaviour. It is proposed that chain scission takes places in the newly formed esteramide bridge.
Entanglements in amorphous polymer networks
Authors: Erman Burak 
Published: March 2011

AbstractThis paper consists of two parts. In the first part, the strain dependence of entanglements or constraints acting along the contour of a Gaussian chain is derived. The functional form of the elastic free energy resulting from constraints along the chain contour is identical to that obtained in the Flory constrained junction model. In the second part, the effective number of constraints acting along the contour of a chain is discussed. The choice of this number results from postulates imposed by various authors and cannot be derived by rigorous theory. The paper compares the predictions based on these assumptions with experimental data from model networks.
Dynamic light scattering by permanent gels: Partial heterodyne and nonergodic medium methods for data evaluation
Authors: Fang Liqi , Brown Wyn 
Published: March 2011

AbstractFour relationships between the intensity and field correlation functions have been used in the analysis of the measured intensity correlation function in dynamic light scattering for four different polymer gel samples. The evaluation of diffusion coefficients was performed using inverse Laplace transformation (ILT) and the cumulante method, respectively. The diffusion coefficients derived from the nonergodic medium method are almost the same as those from the partial heterodyne method when ILT is used. ILT can give similar results by all four procedures even when large baselines for the nonergodic medium method exist. The cumulants method leads to incorrect diffusion coefficients from the correlation functions derived using the nonergodic medium method.
Neutron scattering in polymer gels at the theta temperature
Authors: Hecht Anne‐Marie , Horkay Ferenc , Mallam Simon , Geissler Erik 
Published: March 2011

AbstractSmall angle elastic neutron scattering was performed on three polystyrene networks swollen to equilibrium in cyclohexane at the theta temperature. Comparison of the SANS spectra with similar measurements in uncross‐linked solutions reveals that in the intermediate Q region the gels behave like solutions of lower concentration than the equivalent solutions. We assume that the gel spectra are composed of a static component plus a dynamic, or solution‐like part. By a suitable fitting procedure, the former can be estimated, yielding the mean square static concentration fluctuation <Δφ2> generated by cross‐linking contraints in the gel. Independent measurement of the swelling pressure of these gels permits an estimate to be made of the scattering intensity I(Q=0) of the dynamic part of the spectrum. Plausible agreement is found between the macroscopic and microscopic estimations of the osmotic compressibility if allowance is made for the concentration polydispersity in the gels.
Relaxation during stress‐strain cycles of networks in the glass transition range and its description with an onsager approach
Authors: Kraus Volker , Kilian Hanns‐Georg 
Published: March 2011

AbstractTemperature and strain rate dependence of large cyclic deformations are investigated. The quasi‐static stress‐strain behaviour is described in terms of the van der Waals theory for polymer networks. Within the framework of irreversible thermodynamics, the Gibbs function is extended by hidden variables which represent a set of orthogonal relaxation modes of the Onsager type. These modes are linearly coupled to the quasi static reference state of the network (relaxation mode coupling model). This results in a time dependent expression for the nominal force, where the mode independent relaxation time spectrum plays a dominant role. For high temperatures or low strain rates, the temperature dependence of the spectrum obeys the WLF equation. Approaching the glass transition region, a limitation of the WLF equation is considered. The transition between isothermal and non isothermal deformation is determined.
Determination of the ratio of the shear modulus over the longitudinal modulus for swollen networks
Authors: Zrínyi Miklós , Horkay Ferenc , Rosta János 
Published: March 2011

AbstractThe ratio of the shear modulus over the longitudinal osmotic modulus has been determined by different experimental methods. Osmotic deswelling, swelling kinetics as well as deswelling induced by unidirectional compression were performed. For the experiments chemically cross‐linked poly(vinyl acetate) gels swollen in toluene and acetone (good solvents) and iso‐propyl alcohol (poor solvent) have been used. The results are in agreement with the theoretical predictions.
The influence of interphases on properties of epoxy resin composites
Authors: Kosfeld Robert , Brostow Witold , Hess Michael , Marzi Thomas , Schroeder Ulrich 
Published: March 2011

AbstractWater sorption was determined and dynamic‐mechanical measurements made on dry and water‐containing systems. Different types of surface treatments of the glass fiber were studied. Immobilization of polymer chains in the interphase is determined by the nature of the curing system, annealing conditions, and surface treatment of glass fibers. Penetrating water can be found at three kinds of locations in the composite; water in the interphase has different properties than water in the polymer matrix and in microvoids. This fact can be used as a microscopic probe in epoxy‐containing composites. Water content depends on the density of polar groups and the density of the network. At higher temperatures water causes crazes, at lower it mainly acts as a plasticizer. Water in crazes does not affect the glass transition temperature Tg, but it decreases (tan δ) and weakens the material. As long as water mainly goes into swelling, energy transfer between the resin and the matrix is not affected. The reinforcement then works as it should. The results demonstrate the importance of interphase properties on the behavior of the composite.
Supramolecular structure and properties of specially designed two‐phase macromolecular systems
Authors: Eisenbach C. D. , Heinemann T. , Ribbe A. , Stadler E. 
Published: March 2011

AbstractMultiphase polymer systems with special phase structures and properties can be achieved by the proper design of the polymer constitution and the appropriate sample treatment. Multiblock copolymers consisting of molecularly uniform polyurethane segments of various molecularly engineered structures and connected by highly flexible polyether segments have been synthesized. The segregation of the hard segments and the size, shape and perfection of the hard domains can be controlled by the hard segment's architecture in that either extended chain crystallization or chain folding occurs. The same superstructure and properties as of the above multiblock copolymers can be mimicked by specially designed graft copolymers with polyether backbone and polyurethane branches, again uniform and molecularly engineered. This study has shown that the morphology and superstructure of macromolecular systems can be precisely controlled by the molecularly designed chain architecture and the sample history, and is correlated with special material properties.
Effect of headgroup on the supramolecular morphology of diacetylenic aldonamides
Authors: Frankel David A. , O'Brien David F. 
Published: March 2011

AbstractThis report describes the initial characterization of supramolecular morphology of diacetylenic aldonamides where the headgroup has been systematically varied from hexose, pentose, to tetrose. The electron‐dense diacetylenes allow direct electron microscopic imaging of the assembly morphology without the aid of staining reagents. The electron micrographs reveal a dramatic change in supramolecular morphology upon the simple changing the headgroup from D‐galactose to L‐arabinose. Possible reasons for the change in morphology are discussed.
Semi‐interpenetrating polymer networks with controllable morphology ‐ arrest of demixing by thermoreversible gelation
Authors: De Graaf Leontine A. , Möller Martin 
Published: March 2011

AbstractSemi‐interpenetrating polymer networks with well defined morphologies were obtained using a three‐step process, separating morphology formation and polymerization/crosslinking. Different phase textures were formed when (spinodal) liquid/liquid demixing of a solution of atactic polystyrene in methacrylate monomers was arrested by thermoreversible gelation (vitrification) of the polymer‐rich phase at a desired stage. Subsequent UV‐polymerization of the methacrylate allowed to study the morphology by transmission electron microscopy. Phase diagrams of polymer solutions with low and high viscosities are reported. Depending on the initial solution viscosities and the applied cooling conditions, morphologies both with a dispersed as well with a continuous polystyrene phase could be obtained at PS concentrations already below 10 %. Mechanical measurements indicated only partial demixing in the semi‐IPN's.
Design, preparation, and characterization of hydrogen bonded supramolecular aggregates based on the cyanuric acid‐melamine lattice
Authors: Mathias John P , Simanek Eric E , Seto Christopher T , Whitesides George M 
Published: March 2011

AbstractMolecular self‐assembly is described as a strategy for synthesizing large hydrogen‐bonded supramolecular aggregates that are based on the planar lattice formed of equimolar portions of cyanuric acid and melamine. The aggregates described in this paper contain four to ten individual molecules, are stabilized by networks of 18 to 54 hydrogen bonds, and have molecular weights in the range 2.7 to 6.5 kDa. Each of these aggregates has been characterized using 1H NMR. spectroscopy, gel permeation chromatography, and vapor pressure osmometry. Physical‐organic chemistry is used to (i) improve our criteria for the design of self‐assembling structures and (ii) develop techniques for characterizing non‐covalently bound aggregates in organic solution.
Supramolecular membranes for optical resolutions and molecular recognitions
Authors: Ogata Naoya 
Published: March 2011

AbstractPoly(L‐glutamate) having amphiphilic side chains was designed as membrane materials for optical resolution of α ‐amino acids. Solvent‐ cast films of the poly(L‐glutamate) had a self‐ordered structure containing α‐helix of the poly(L‐glutamate). Optical resolutions of various amino acids were carried out through the thin membranes of the amphiphilic poly(L‐glutamate).Racemic mixtures of Tryptophan were completely separated through the membrane. Mechanism of the optical resolutions was investigated in terms of molecular recognitions of racemic Tryptophan by the ordered structure of the mambrane.
Metal‐directed assembly of coordination oligomers
Authors: Constable Edwin C. , Thompson Alexander M.W. Cargill , Tocher Derek A. 
Published: March 2011

AbstractBridging ligands containing two spatially separated 2,2′:6′,2′‐terpyridinyl metal‐binding domains have been prepared and used for the controlled assembly of coordination oligomers incorporating ruthenium(II) and other metal ions. Two such bridging ligands have been structurally characterised. The systematic synthesis of a range of homo‐ and heterometallic polynuclear complexes incorporating these bridging ligands and a variety of terminator 2,2′:6′,2′‐ terpyridines is described.
Precise architecture of 1:1 alternating copolymers between germylenes and p‐benzoquinone derivatives: First clear‐ cut evidence of biradical mechanism in polymerization chemistry
Authors: Kobayashi Shiro , Iwata Satoru , Shoda Shin‐Ichiro 
Published: March 2011

AbstractGermylenes bearing a bulky amide substituent have been copolymerized with various p‐benzoquinone derivatives without any added catalyst to give novel class of germanium‐containing polymers having a tetravalent germanium unit and a p‐hydroquinone unit alternatingly in the main chain (“oxidation‐reduction alternating copolymerization”). The resulting copolymers have high molecular weight (Mw>5.5×104) and are soluble in common organic solvents. A novel biradical mechanism involving a germyl radical and a semiquinone radical is proposed on the basis of ESR analysis of the propagating polymer end as well as trapping experiments using a disulfide or TEMPO radical.
Modular construction for the programmed assembly of molecular crystals and liquid crystals
Authors: Moore Jeffrey S. , Zhang Jinshan , Wu Ziyan , Venkataraman Dhandapani , Lee Stephen 
Published: March 2011

AbstractThis research aims to develop schemes for the programmed assembly of molecular materials. The underlying premise guiding this work is that structural information stored in the molecular constituents dictates their condensed phase organization (i.e. through the sum of all non‐covalent interactions). The challenge then is to design molecular building blocks that encode this information in a decipherable manner. Our approach has relied on the use of organic nanoarchitectures, which we believe will serve as “modular units” for programmed assembly. Large molecules of well defined constitution and geometry offer the advantage that a high level of information can be incorporated into a single unit. The design and synthesis of nanoscale macrocyclics and macrobicyclics for this purpose has been achieved. Studies on the solution aggregation of the macrocyclics have provided a unique opportunity to glimpse some of the interactions which may influence solid state ordering. These building blocks are being used for the rational design of novel materials such as porous organic crystals and tubular mesophases.