bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyphosphate chains by addition of oxiranes to phosphoric acid
Authors: Biela Tadeusz , Nyk Andrzej , Kubisa Przemyslaw 
Published: March 2011

AbstractAddition of diepoxides to the acids of phosphorus provides a new, attractive route to polyphosphates. In order to understand better the mechanism of this reaction and the structure of the products, the model reactions, namely additions of simple oxiranes to the acids of phosphorus, have been studied. It was shown that this reaction is catalysed by the P‐OH groups of the acids. Activation of the oxirane molecule occurs predominantly by formation of the hydrogen bonded species while ionized form of acid plays only a minor role at the studied conditions (1,4‐dioxane solution, 25°C). Reactivity of subsequent P‐OH groups in phosphoric acid increases with increasing degree of substitution by ‐OCH2CH2OH groups. The ratio of the rate constants of formation of mono‐, di‐, and triesters of phosphoric acid is equal to 1/2/4. This has been attributed to the formation of internal hydrogen bonds, involving substituents and the P‐OH groups. The observed order of the rate constants shows that reaction can not be stopped at the diester stage (linear units) and triester species (branched units) are formed fast. However, due to the large difference in the rate of hydrolysis, especially pronounced at basic conditions, triesters of phosphoric acid can easily be converted into the corresponding diesters by simple hydrolysis. Thus, the addition of diepoxides to phosphoric acid, followed by hydrolysis, leads to essentially linear polyphosphate chains.
Zwitterionic chain polymerizations of cyanoacrylates
Authors: Pepper D. C. 
Published: March 2011

AbstractThe lecture reviews recent studies on vinyl and vinylidene compounds, chiefly alkyl cyanoacrylates. It emphasizes the kinetics, especially the distinctive SINT (slow‐initiation‐no‐termination) pattern, and the composite mechanism of initiation by tertiary amines. The need for corroboration of interpretations, clarification of ambiguities and extensions is emphasized.
Model theory of relaxation properties of macromolecules in the nematic LC state
Authors: Gotlib Yuli , Medvedev Grigori , Fridrikh Sergei 
Published: March 2011

AbstractThe continuous and lattice dynamic models of the macromolecules in the LC state are considered. The relaxation properties of polymer chain in the nematic LC state may depend on both the variation of the conformation in the ordered state and on the activation barrier of the molecular field. The calculation and comparison of the longitudinal and transversal relaxation spectra for the continuous and discrete rotameric mechanism of the mobility are performed. For the simplest model of the heterogeneous polymer chain for continuous dynamic models the complicated relaxational behavior with two longitudinal and two transversal branches is manifested. The dynamic properties of the lattice dynamic model with spacer consisting of several bonds are considered.
Zirconocenium cation catalysis of propene polymerization
Authors: Chien James C. W. , Tsai Woei‐Min 
Published: March 2011

Abstractrac‐Ethylenebis(1‐η5‐indenyl)dimethylzirconium (1) was reacted with triphenylcarbenium tetrakis(pentafluorophenyl)borate (2) to produce in situ the rac‐ethylenebis(indenyl)methylzirconium cation (3). This aluminium‐free catalyst showed propene polymerization activity (A) and stereoselectivity which both increase with the decrease of polymerization temperature (Tp). At very low Tp, 3 behaved as a “single‐site” catalyst. An efficient way to produce such cation is to react ansa‐zirconocene dichloride with 2 in the presence of TEA (=triethylaluminium). A superior cationic catalyst was obtained from rac‐dimethylsilylenebis(1‐η5‐indenyl)dichlorozirconium, 2, and TEA, which polymerizes propene at −20°C(−55°C) with activity of 2×109 (3×108) g polypropene per (mol Zr η mol C3H6 η h) to polypropenes which are 93.8% (99.4%) isotactic with melting temperature Tm = 152.6°C (159.9°C) and viscosity‐average molecular weight Mv = 1.4×105 (2.2×105). The addition of methylaluminoxane lowers the A of the cationic catalyst especially at low Tp. Rigorously speaking, the cation derived from 1 or 3 behaves as a “single site” catalyst only at very low Tp. The use of TEA significantly and unexpectedly enhances the efficiency of the zirconocenium catalyst system.
A theory for concentrated fiber suspensions with strong fiber‐fiber interactions
Authors: Sandstrom Chad R. , Tucker Charles L. 
Published: March 2011

AbstractA theory is presented for the flow‐induced fiber orientation and stress in fiber‐reinforced polymer composites with planar fiber orientation. The rate of change of fiber orientation is given as a function of the strain rate in the continuum and the probabilistic effects of physical inter‐fiber contacts. The continuum stress is calculated from the stress in the fluid and fibers, where fiber stress is a result of the local disturbance in the fluid velocity field and of the inter‐fiber contact forces. Fiber orientation is described via a probability density function whose transport equation has the form of a standard advection‐diffusion equation with an orientation‐dependent rotary diffusion. This equation is solved using a finite difference scheme and the results are presented.
Supramolecular chemistry — Molecular information and the design of supramolecular materials
Authors: Lehn Jean‐Marie 
Published: March 2011

AbstractMolecular information expressed through molecular recognition events provides means for directing the spontaneous formation of supramolecular species from complementary components. It may allow the design and engineering of supramolecular materials, in particular of liquid crystalline and of polymeric nature. Thus, supramolecular mesophases have been obtained from molecular recognition‐induced association of suitable subunits. The self‐assembly of complementary ditopic components generates liquid crystalline “polymers” of supramolecular nature; it takes place by a progressive growth revealed by electron microscopy: from nuclei, to filaments, to tree‐like species, to strings and fibers that present helicity induced by the chirality of the subunits. A rich variety of structures and properties may be expected to result from the blending of supramolecular chemistry with polymer chemistry and materials science.
Nitrogen based flame retardants for nitrogen containing polymers
Authors: Horacek H. , Grabner W. 
Published: March 2011

AbstractThe future aspects of Nitrogen based flame retardants in Nitrogen containing polymers are promising, as they contain no other chemical element than already present in the polymers. Sucessful applications are:* Melamine in Combustion Modified High Resilient Foam* Melamine in B‐1 rigid foam* Melamine Cyanurate in Polyamides* Melamine and Melamine salts in intumescent paints* Melamine Cyanurate in thermoplastic Polyurethanes.
What is a ‘gel’?
Authors: Almdal Kristoffer , Dyre Jeppe , Hvidt Søren , Kramer Ole 
Published: March 2011

AbstractSome of the existing definitions of the term ‘gel’ are discussed and shortcomings are identified. A purely phenomenological definition is proposed: a gel is a soft, solid or solid‐like material consisting of two or more components one of which is a liquid, present in substantial quantity. ‘Solid‐like gels’ are further defined in terms of the dynamic mechanical properties.
Synthesis of soluble, liquid crystalline aramids via transition metal π‐Complexation
Authors: Dembek Alexa A. , Burch Robert R. , Feiring Andrew E. 
Published: March 2011

AbstractAn organo‐soluble, liquid crystalline organometallic polymer, (p‐phenyleneterephthalamide)Cr(CO)3 [(PPTA)Cr(CO)3], is prepared by polycondensation of (p‐phenylenediamine)Cr(CO)3 with terephthaloyl chloride. Polarizing optical microscopy of this high molecular weight metallo‐aramid shows a nematic liquid crystalline texture in N, N‐dimethylacetamide (DMAc), demonstrating that metal π‐complexation maintains the lyotropic, rigid‐rod character of PPTA. A PPTA copolymer with 50% of the diamine rings Cr(CO)3 π‐complexed is also soluble and lyotropic in DMAc. Tensile properties of films of the 100% Cr(CO)3 complexed aramid are isotropic in the plane of the film, while those of the 50% complexed analog are highly anisotropic. The organometallic substituent is a site for polymer functionalization: exchange of a carbonyl for a trimethylphosphine ligand, and subsequent polymerization affords the phosphine‐functionalized (PPTA)Cr(CO)2P(CH3)3, which has a much higher critical concentration for liquid crystal formation. Oxidative decomplexation of the Cr(CO)3 group yields the parent PPTA, demonstrating the reversibility of the organometallic modification approach.
Macromolecular metal complexes an overview
Authors: Wöhrle Dieter 
Published: March 2011

AbstractAn introduction to the 5th International Symposium on Macromolecule Metal Complexes (MMC V) is given. Macromolecule metal complexes are classified in two different types of structural arrangements. Examples are exemplarily given from the research in the authors laboratory. Some properties and potential applications are mentioned. Outstanding results described in 24 contributions of main lectures are related to the increasing importance of the field of macromolecular metal complexes.
Thermoreversible gelation with junctions of variable multiplicity
Authors: Tanaka Fumihiko , Stockmayer Walter H. 
Published: March 2011

AbstractEffect of junction multiplicity on the phase behavior of physical gels is studied with special attention to the interference phenomena between gelation and phase separation. Three important models of the junction multiplicity are detailed, each representing cross‐linking by hydrogen bond, microcrystallization and dipole aggregation. Singularities accompanying the gelation transition are found to be analogous to those of the Bose‐Einstein condensation.
Electrical conductivity of iodine doped pseudo interpenetrating polymer networks
Authors: Frisch H. L. , Chen Z. J. , Chen X. 
Published: March 2011

AbstractThe iodine doped pseudo interpenetrating polymer networks (PIPN's) of both conjugated and non‐conjugated linear polymers in less conducting crosslinked polymer networks may possess modest DC conductivities, σ, of the order of the iodine doped bulk polymers. There is evidence that critical percolation occurs in PIPN's and that these materials possess a quasi‐one dimensional character unlike the iodine doped bulk polymers, e.g. the σ of the iodine doped PIPN's increases from about 120 K to 4 K with decreasing temperature. We provide a simple partial (near and somewhat below room temperature) theory and summarize conductivity and resonance Raman spectroscopic studies.
Polymer chains at the interface of two different phases
Authors: Kosmas M. , Kosmas A. 
Published: March 2011

AbstractWe describe the macroscopic behaviour of polymers at the interface of two different phases in terms of the two average lengths which the chain units obtain at the two phases. The possibility for the units of the same chain to have different average lengths changes the spatial monomeric distribution and all the other macroscopic properties of the polymers compared to those of similar systems in a single phase.
Surface analysis of polymer materials by secondary ion mass spectrometry
Authors: Benninghoven Alfred , Rading Derk 
Published: March 2011

AbstractAtomic as well as molecular secondary ions are emitted from the uppermost monolayer of a solid during ion bombardment. Mass analysis of these positive and negative secondary ions supplies detailed information on the chemical composition of the bombarded surface. High mass range (> 10,000 u), high mass resolution (m/Δm > 10,000), accurate mass determination (ppm range) and high sensitivity (ppm of a monolayer) are achieved by applying time‐of‐flight (TOF) mass analyzers. TOF‐SIMS has been successfully applied to a wide variety of polymer materials, including polymer blends, chemically or plasma modified surfaces, and plasma polymerization layers. Detailed information on the composition of repeat units, endgroups, oligomer distributions, additives, as well as surface contaminants can be obtained. Basic concepts of TOF‐SIMS will be described and typical analytical examples for the characterization of polymer materials will be presented.
Recent product developments and process monitoring in the field of reactive polymer compounding
Authors: Fritz Hans Gerhard , Cai Quiongying , Bölz Uwe , Anderlik Rainer 
Published: March 2011

AbstractThis contribution aims at the illustration of the potential of reactive blending, hold up polypropylene modification as an example. Formulation rules and process technology to create PP/PA‐alloys and thermoplastic elastomers based on PP/EP(D)M, as well as the property profiles of the resulting products will be described. A separate chapter is dedicated to functionalization of polypropylene by mainchain‐grafting of selected linkage molecules, to widen the range of application of this low‐cost polymer.
Reactive blending of poly(ethylene terephthalate) with ethylene‐propylene rubber
Authors: Yokoyama Koichi , Fujita Yuji , Higashida Noboru , Inoue Takashi 
Published: March 2011

AbstractA gram‐scale miniature reactor designed for reactive blendind was introduced. A brief review was given on the light scattering method for morphology characterization and the ellipsometric analysis on polymer‐polymer interface. These methods were applied for the reactive blending of poly(ethylene terephthalate) with ethylene‐propylene rubber (70/30 PET/EPR). Compared with non‐reactive system, the reactive one yielded finer dispersion of rubber particles. It showed better stability of particle dispersion during static annealing. The reactive system with thick interface showed higher impact strength than the non‐reactive one having same particle size but thinner interface, suggesting that the thick interface may be a prerequisite to the rubber toughening.
Fundamentals of texturing: Crystallization by heat transfer and flow
Authors: Janeschitz‐Kriegl H. 
Published: March 2011

AbstractThe textures which are obtained in crystallizing materials, are strongly dependent on the processes of casting (flow and heat transfer). It is very important to discern between two extreme limiting cases, viz. the heat conduction controlled processes (occurring with fast crystallizing materials and thick samples) and the nucleation rate controlled processes (occurring with slowly crystallizing materials and thin samples). Clearly, polymer processing must be classified near the latter limiting case. In principle, the mathematical problems were solved by W. Schneider et al. in the course of an Austrian National Working Party. But, the evaluation of the physical data is a cumbersome task. A brief report is given of the (partial) unravelling of the crystallization kinetics of isotactic PP under the influence of shear flow.
Recent advances in molecuar and supermolecuar characterization of cellulose and cellulose derivatives
Authors: Kamide Kenji , Saito Masatoshi 
Published: March 2011

AbstractRecent advances between 1985 and early 1993 in the following topics of the characterization of molecular structure and molecular properties of cellulose and its derivates (CD) made in the authors' laboratories are briefly reviewed: (1) A theoretical basis of the assignment of carbonyl carbon peaks of 13C NMR spectra on cellulose acetate (CA) was given, especially when the total degree of substitution <<f>> is below 3. (2) Molar fractions of 8 kinds of unsubstituted and partially or fully substituted anhydroglucopyranose units were successfully determined for CA and sodium cellulose sulfate (NaCS). (3) The sequence distribution of substituted and unsubstituted anhydroglucopyranose units along a water–soluble CA chain was evaluated. (4) C6‐substituted (i.e., 6‐O‐acetyl) CA and C2‐ and C6‐substituted CA were synthesized, and the full assignment of the 13C NMR spetrum of the former was given and a new method for evaluating the degree of substitution at C6 position was proposed. (5) By destructing the intramolecular hydrogen bonding, cellulose becomes soluble in aq. sodium hydroxide. The specific supermolecular structure of aq. sodium hydroxide, dissolving mechanism, dissolved state and molecular parameters of cellulose in aq. sodium hydroxide were discussed. (6) The solubility behavior of CA with a wide range of total degree of substitution in solvents including water, acetone/water and acetone is controlled by the distribution of substitution and the supermolecular structure. (7) The existence of O3‐H … O'5 intramolecular hydrogen bonds in a water‐in soluble cellulose derivative with hydrophilic substituent (NaCEC) was confirmed by CP/MAS 13C NMR and deuteration IR method. At a relatively low degree of substitution the solubility of the derivative in water or aqueous alkali was mainly governed by considerable destruction of the intramolecular hydrogen bonds. (8) The persistence length q, evaluated directly by small‐angle X‐ray scattering (SAXS) on CA with different total degree of substitution <<f>> ranging from 0,8 to 2,9 confirmed definitely the conclusion drawn before by Kamide and Saito on the molecular rigidity of CD, especially the effect of <<f>> on q. (9) C6‐substituted CA shows different solubility towards dimethylacetamide and water at 20°C, as compared with C2‐ and C3‐subsituted CA and C2‐, C3‐ and C6‐ substituted CA, whose <<f>> is ca. 0,6.
Polymerization of acetylenes with rare earth coordination catalysts
Authors: Shen Zhiquan 
Published: March 2011

AbstractThe polymerization of acetylene and its derivatives by rare earth coordination catalysts and the characterization of the polymers so obtained in our laboratory are reviewed.Because of the metallic conductivity possessed by doped polyacetylene and the unique properties such as conductivity (semiconductivity), paramagnetism, migration and transfer of energy and chemical reactivity and complex formation ability often shown by acetylenic polymers, which seem promising as specialty polymers, there has been considerable interest in the polymers of acetylene and its derivatives. A wide variety of catalyst systems have been developed for the polymerization of acetylenes. But there has been no information concerning the use of rare earth compounds as catalysts in the polymerization of acetylene and its derivatives. We for the first time in 1981 have succeeded in the polymerization of acetylene with rare earth coordination catalysts, which in turn is a development based upon earlier work on the diene polymerization using rare earth coordination catalysts(Ref. 1). Using rare earth catalysts, acetylene can be polymerized conveniently into high cis polyacetylene films with metallic sheen at room temperature and phenylacetylene can also be polymerized into high molecular weight, high cis polyphenylacetylene films at ambient temperature. Thus new varieties of polyacetylenes have been developed and a novel family of coordination catalysts consisting of a rare earth compound plus trialkyl aluminum for the polymerization of acetylenes has been exploited. This article reviews our studies on the polymerization of acetylene and its derivatives with rare earth coordination catalysts and on the characterization of the polyacetylenes prepared.
Design of functional polymers based on organic synthesis ‐ novel polymerizations of allene and propargyl derivatives
Authors: Endo Takeshi , Tomita Ikuyoshi 
Published: March 2011

AbstractThis paper describes our recent work dealing with novel polymerization methods of allene and propargyl derivatives. By the radical, cationic, and living coordination polymerizations, polymers bearing exomethylene moieties in the side chain could be obtained. The polymers obtained could undergo the cationic crosslinking reaction. As step‐growth polymerizations, spontaneous copolymerizations, polyadditions with dithiols, and coupling polymerizations using palladium catalyst are also described.
Polymer dispersed liquid crystal display device for projection high definition television application
Authors: Chang S. J. , Chiao S. , Lai W. J. , Lin C. M. , Fuh Andy Y. G. 
Published: March 2011

AbstractPolymer dispersed liquid crystal (PDLC) is a light scattering material that operates on the principle of electrically modulating the refractive index of the liquid crystal in an optical isotropic, transparent solid. The principle of operation of the PDLC device, the interface requirements between PDLC material and its driving circuit are studied. For high definition television (HDTV) application, a detailed comparison of PDLC vs. twisted nematic/super twisted nematic (TN/STN) display devices will be discussed. It was found that single crystal metal oxide semiconductor field effect transistor (MOSFET) is better than conventionally used thin film transistor (TFT) in driving these PDLC light valves.
Use of noncovalent interactions to form novel liquid crystalline polymeric materials
Authors: Geraldine Bazuin C. , Brandys Frank A. , Eve Tegan M. , Plante Michel 
Published: March 2011

AbstractA novel concept in polymeric liquid crystalline (LC) materials, via electrostatic grafting or complexation of functionalized mesogens and appropriate polymers, is described. It is applied to three specific systems characterized by side‐chain LC architecture, two of which involve hydrogen‐bonding interactions, the third ionic interactions. In these systems, complexation tends to create greater order in the mesophases present. In the hydrogen‐bonded systems, the transition temperature from the isotropic state tends to decrease compared to that of the functionalized mesogen; in the ionically‐bonded system, the reverse is true. At low concentrations, the mesogens act as plasticizers.
Characterization and flow properties of lyotropic ultrahigh‐molar‐mass polysaccharide mesophases
Authors: Jacobs Alexandra , Kulicke Werner‐Michael 
Published: March 2011

AbstractThe occurrence of lyotropic mesophases in solutions of various polysaccharides, such as non‐ionic schizophyllan and anionic xanthan, was demonstrated by means of polarizing microscopy. In contrast to synthetic polymers where the formation of liquid‐crystalline phases has been attributed to the presence of mesogenic groups in the main‐ or side‐chain, here a helical structure is a prerequisite for the formation of mesophases. It was then shown that the stability of the helix is dependent on the chemical structure and the arrangement of the side groups. Apart from their optical anisotropy, some lyotropic mesophases are distinguished by extraordinary viscous and elastic properties (e.g. maximum behaviour of viscosity). The viscoelastic material functions were determined by rheological methods. A precise characterization of the chemical and steric microstructure should provide information on the ability of polysaccharides to form mesophases. Determination of the chemical microstructure (quaternary polymer) was carried out by 1H NMR spectroscopy after ultrasonic degradation. Low‐ and multi‐angle laser light scattering were employed for the determination of the steric microstructure which indicates an expanded semi‐flexible structure. The experimental results were compared with those from molecular modelling.
New concept for molecular composites
Authors: Ogata Naoya 
Published: March 2011

AbstractNew concept for molecular composites was proposed by in‐situ polymerization of rigid monomers in matrix polymer solutions. When the monomers and the matrix polymers had some affinity interactions such as hydrogen‐bonding or acid‐base interactions, resulting composite materials showed a homogeneously mixed blending to reach molecular composites. Polyimide composites were discussed based on this concept.