bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymerization of sarcosine‐NCA and l‐leucine‐NCA or l‐phenylalanine‐NCA
Authors: Kricheldorf Hans R. , Tönnes Kai‐Uwe 
Published: March 2011

AbstractCopolymerizations of sarcosine‐NCA (Sar‐NCA) with leucine‐NCA (Leu‐NCA) or phenylalanine NCA (Phe‐NCA) were conducted under five different reaction conditions. Benzylamine, triethylamine, pyridine and sodium methoxide (NaOMe) were used as initiators. Molar compositions of the resulting copolypeptides were determined by 1H or 13C NMR spectroscopy and reactivity ratios were calculated from copolymerizations stopped at low conversions. Sequence analyses of copolypeptides isolated at high conversions were conducted by means of 13C or 15N NMR spectroscopy. Blocky sequences were found due to a higher reactivity of Sar‐NCA under all reaction conditions. The secondary structure of the solid copolypeptides was characterized by 13C NMR CP/MAS spectroscopy and WAXS powder patterns. The secondary structures are kinetically controlled and change into thermodynamically stable ones upon reprecipitation.
Living and immortal polymerizations of epoxide and episulfide with zinc N‐substituted porphyrin
Authors: Inoue Shohei , Aida Takuzo , Watanabe Yoshihiko , Kawaguchi Ken‐Ichi 
Published: March 2011

AbstractZinc complexes of N‐methylated porphyrin are excellent initiators for the living and immortal polymerizations of epoxide and episulfide. A remarkable accelerating effect of visible light is observed in the polymerization of epoxide. Block copolymers from episulfide and epoxide with narrow molecular weight distributions can be synthesized.
Synthesis of primary hydroxyl functional poly(propylene oxide) of controlled molecular weight by direct polymerization
Authors: Yoo Y. , McGrath J. E. 
Published: March 2011

AbstractUtilization of aluminiumporphyrin catalyst/initiator structures was demonstrated to be highly capable of producing controlled molecular weight/narrow molecular weight distributions and in several cases good functionalities. Further extension of our studies to systems wherein benzyl alcohol is first reacted with the aluminiumporphyrin initiator have been conducted. The resulting aluminiumporphyrin benzyl alcohol alkoxide is capable of initiating propylene oxide in a controlled manner. After work‐up, the resulting material can be subjected to hydrogenolysis and this regenerates a very desirable primary hydroxyl group at the initiating site. Moreover, the hydrogenolysis disrupts the aromatic character of the porphyrin species and greatly diminishes any residual color which is usually attributed to the initiator fragments. Difunctional species can be generated by a coupling reaction with terephthaloyl chloride and star‐shaped macromolecules are possible via coupling with bisphenol‐A diglycidyl ether. Synthesis of these materials and characterization is discussed herein. In particular, fluorine‐19 NMR derivatization has been quite effective at distinguishing between the derived primary hydroxyl species and the usual secondary hydroxyl systems.
Development of an advanced process for manufacturing trioxane ethylene oxide copolymer
Authors: Masamoto J. , Iwaisako T. , Yoshida K. , Matsuzaki K. , Kagawa K. , Nagahara H. 
Published: March 2011

AbstractAn advanced process for manufacturing trioxane ethylene oxide copolymer has been developed.First, a new technology for production of highly concentrated aqueous formaldehyde was developed by oxidizing methylal. Whereas oxidation of methanol yields 1 mol of water per mole of formaldehyde, methylal oxidation produces only 1 mol of water for every 3 mol of formaldehyde.Thus the output from methylal oxidation is more than 70% formaldehyde, compared with 55% from methanol.The relatively high formaldehyde concentration enhances formation of trioxane.Purified trioxane is copolymerized with ethylene oxide in the presence of an end‐capping agent such as methylal producing an end‐capped polymer with high thermal stability.Two new intermediates in the initiation reaction of the copolymerization, 1,3,5,7‐tetraoxacyclononane (TOCN) and 1,3,5,7,10‐ pentaoxacyclododecane(POCD) were isolated and a new initiation mechanism was proposed.A commercial plant employing this process with a capacity of 15 000 tons/year is operating well.
Copolymers of trioxane with 2,3‐epoxypropyl acrylate: Thermally stable polyacetal copolymer networks
Authors: Pesce‐Rodriguez R. A. , Yang N. L. , Auerbach A. , Paul J. 
Published: March 2011

AbstractCationic copolymerization of trioxane with 2,3‐epoxypropyl acrylate gives thermally stable crosslinked copolymer in high yield. The structure of the crosslinked copolymer has been characterized by solid state 13C NMR spectroscopy. The comonomer acrylate group functions as a crosslinking agent in the polymerization process as well as a bound stabilizer in the resulting network. The crystallinity of the copolymer is unusually low compared to copolymers with comparable incorporation levels of the comonomers. The crosslinked acetal copolymer has the potential for further modification through its pendant acrylate group.
Anionic synthesis and characterization of poly(styrene‐block‐ethylene oxide) polymers with fluorescent probes at the block junctions
Authors: Quirk Roderic P. , Kim Jungahn , Rodrigues Klein , Mattice Wayne L. 
Published: March 2011

AbstractFluorescent‐labeling reactions of poly(styryl)lithium were effected with either 2‐(1‐phenylethenyl)naphthalene or 1‐phenyl‐1‐(1‐pyrenyl)ethylene followed by functionalization of the resulting 1‐phenyl‐1‐arylalkyllithium species with ethylene oxide. The resulting polymeric alkoxylithiums were used to initiate the anionic polymerization of ethylene oxide in a mixture of benzene and dimethyl sulfoxide. A series of block copolymers [Mn(PS)=5.1 × 103 g/mol); Mw/Mn=1.02] with 20–40wt% ethylene oxide were characterized by thin‐layer chromatography, size exclusion chromatography, 1H NMR and quantitative UV‐visible spectroscopy. Fluorescence measurements on the block copolymers were carried out in 1,2‐dichloroethane with varying amounts of methanol. No excimer formation was detected for either naphthalene‐ or pyrene‐labeled block copolymers. Energy transfer from the naphthalene‐ to the pyrene‐labeled polymers was observed at about 80 vol.% methanol. These results are discussed in relationship to the interfacial boundary distances in the block copolymer micelles as deduced by application of the “Spectroscopic Ruler”.
Activated monomer polymerization of oxiranes. Micro‐structure of polymers vs. kinetics and thermodynamics of propagation
Authors: Bednarek Melania , Biedron Tadeusz , Kubisa Przemyslaw , Penczek Stanislaw 
Published: March 2011

AbstractIn the Activated Monomer (AM) polymerization of substituted oxiranes (propylene oxide ‐ PO, epichlorohydrin ‐ ECH), the microstructure of the chain is governed exclusively by the kinetics of the propagation step. In the copolymerization of ECH with 5‐membered (tetrahydrofuran ‐ THF) or 6‐membered (1,4‐dioxane ‐ Diox) cyclic ethers, the distribution of comonomer units depends on both kinetic and thermodynamic factor, which allows preparation of oligodiols having regular (i.e. alternating) distribution of comonomer units in the chain.
Ring‐opening polymerization of oxetanes by cationic initiators: Polymerization of 3‐azidomethyl‐ 3 ‐ methyloxetane with bis(chlorodimethylsilyl)benzene/silver hexafluoroantimonate initiating system
Authors: Talukder M. A. H. 
Published: March 2011

AbstractQuasi‐living cationic polymerization of 3‐azidomethyl‐3‐methyloxetane (AMMO) was achieved with a bis(chlorodimethylsilyl)benzene/silver hexafluoroantimonate (BSB/AgSbF6) initiating system in methylene chloride at −78°C. The average molecular weight (Mn) increased linearly with an increasing monomer/ initiator ([M]/[I]) ratio and a linear Mn vs. [M]/[I] ratio plot passes through the origin. Mn's observed were higher than the calculated value. This indicates the initial loss of initiator or slow initiation during the polymerization of AMMO with BSB/AgSbF6 initiating system, or the combination of both. Theoretically, in a system where the initiation is slower than the propagation, a diblock copolymer will be formed. Similarly, impurities, such as water, will cause chain transfer to the propagating chains during polymerization and form a homopolymer and a diblock copolymer in addition to the desired triblock copolymer. In short, a perfect triblock copolymer will be formed for a difunctional cationic initiator when the system is pure and dry and the initiation of polymerization is faster than the propagation.
Novel synthetic approaches to poly(ε‐caprolactam)‐based materials
Authors: Russo Saverio , Biagini Emilio , Bonta Giorgio 
Published: March 2011

AbstractOur study has been focused on the fast anionic polymerization of ϵ‐caprolactam (CL) under isothermal conditions, both in bulk and in suspension, in the temperature range between 150 and 200°C.A careful choice of the reaction parameters (type and concentration of activator, polymerization temperature and rate, cooling rate after polymerization) enabled us to find experimental conditions suitable for minimizing the extent of side reactions and, consequently, the concentration of UV‐absorbing structures incorporated in the poly(ϵ‐caprolactam) (PCL) chain. In terms of structural regularity, the resultant PCL compares favorably to the corresponding polyamide synthesized by the hydrolytic process. Moreover, extension of this approach to the anionic polymerization of CL in suspension allowed us to obtain particulated PCL, characterized by controlled size and surface porosity. Several PCL‐based materials, formed by seeded suspension polymerization, have been obtained. Potentials of this new synthetic approach are outlined.
Model polyisoprenes with associating end‐groups
Authors: Hadjichristidis Nikos 
Published: March 2011

AbstractA series of narrow distribution ω‐functionalized linear polyisoprenes were prepared by converting the tertiary amine group of polyisoprene ‐ obtained by anionic polymerization of isoprene with 3‐(dimethylamino)propyl lithium ‐ to the highly polar sulfo‐zwitterion group by treatment with cyclopropane sultone. The dilute solution properties of these polymers were mainly examined in cyclohexane and cyclohexane/1‐heptanol mixtures. In cyclohexane the sulfo‐zwitterion polymers were highly aggregated. The degree of association generally decreases with increasing base chain length, due to excluded volume repulsions of the polymeric tails, except at very low molecular weights (2 400–4 800) where the different microstructure of these polymers may play a role. Depending on the molecular weight of the linear precursor, the aggregates may resemble star polymers or may exhibit a more extended core morphology. These findings, regarding the shape of the aggregates, are also supported by melt viscosity mesurements and x‐ray scattering studies.
Synthesis, structure and properties of a helical nylon‐3 derivative
Authors: Muñoz‐Guerra S. 
Published: March 2011

AbstractA review of the polyamide poly(α‐isobutyl‐L‐aspartate), embracing synthesis, crystal structure and properties, is reported. The interest in this nylon‐3 derivative arises from its ability to adopt conformations similar to the characteristic α‐helix of polypeptides. Two different synthetic approaches, both of them starting from L‐aspartic acid, have been followed for the preparation of this polyamide. Poly‐condensation in solution of α‐isobutyl‐L‐aspartate pentachlorophenyl ester yielded polymers with molecular weights up to near 80 000. About six times higher values were obtained by anionic polymerization of β‐lactam of α‐isobutyl‐L‐aspartate. Highly regular chains were attained in both cases. Two crystalline forms, hexagonal and tetragonal, made of helices with 3.25 and 4 residues per turn, respectively, were characterized by X‐rays and electron microscopy. Transitions between these two forms in the solid state were induced by heating, whereas a helix‐coil conversion promoted by acids was found to take place in solution. Liquid crystal properties have been observed for solutions of this polymer in helicogenic solvents, and films with cholesteric structure were spontaneously generated from them by casting. On the contrary, uniaxially oriented films could be obtained when cast under the effect of an electric field. A shear piezoelectric response of about 12–13 pC/N was measured for these films.
Mechanical aspects of polymer blending
Authors: Kausch H.H. 
Published: March 2011

Abstract“Improving through mixing” is a fundamental human concept; as applied to polymers, there are thermodynamic, processing related and mechanical obstacles. In this paper some mechanical consequences of structural heterogeneity on a molecular and microscopic level are discussed.The second aspect to be treated is that of the molecular mechanisms contributing to deformation and fracture, especially void formation, crazing, and shearbanding. To develop these ideas, reference to two systems will be made, a core‐shell particle modified polyamide and an epoxy resin.
Functional polypropylene blend compatibilizers
Authors: Mülhaupt Rolf , Duschek Thomas , Rieger Bernhard 
Published: March 2011

AbstractSolid phase dispersants, often referred to as blend compatibilizers, are the key components of high‐value‐in‐use polypropylene blends with unusual property combinations. In multiphase polypropylene blends, functional blend compatibilizers enhance the dispersion of incompatible polymeric blend components, in particular of polar polymers, fibers or fillers, and improve the interfacial adhesion between polymer matrix and dispersed phases. Some of the major synthetic routes to functional polypropylene blend compatibilizers are discussed. A novel range of monofunctional polypropylenes containing a variety of functional endgroups, e.g., anhydrides, esters, amines, carboxylic acids, silanes, boranes, alcohols, and thiols, has been derived from mono‐olefin‐terminated polypropylenes. These olefinic polypropylene intermediates have been prepared with soluble metallocene catalysts which give excellent control of polypropylene molecular weight, molecular weight distribution, microstructure, and olefinic endgroups. Thiol‐terminated isotactic polypropylenes have been used as polymeric chain transfer agents in styrene and styrene/acrylonitrile polymerization to form novel polypropylene‐block‐polystyrene and polypropylene‐block‐poly(styrene‐co‐acrylonitrile) block copolymers. In the case of poly(styrene‐co‐acrylonitrile) blends with polypropylene morphological studies demonstrate the efficiency of propylene block copolymer blend compatibilizers.
Stereospecific polymerizations with metallocene catalysts: Products and technological aspects
Authors: Antberg M. , Dolle V. , Haftka S. , Rohrmann J. , Spaleck W. , Winter A. , Zimmermann H.J. 
Published: March 2011

AbstractPolypropylene homopolymers made by three different stereorigid metallocene catalysts (two isospecific, one syndiospecific) are compared with each other and with commercial samples made by a heterogeneous catalyst. The comparison includes mechanical properties, DSC‐, 13‐C NMR‐ and WAXS‐data. The correlation between microscopic data and macroscopic properties is discussed.A novel particle‐forming process in propylene bulk polymerization with stereorigid metallocene catalysts is demonstrated and discussed.
Molecular arrangements and conformations of chain molecules near impenetrable surfaces
Authors: Vacatello Michele , Yoon Do Y. 
Published: March 2011

AbstractThe Monte Carlo method has been used to model liquids of chain molecules confined between two impenetrable surfaces (walls). Two kinds of chains have been simulated in two separate calculations: short n‐alkane (n‐tridecane) chains represented at the atomic level in the first case and long polymer chains represented as necklaces of beads in the second case. Molecules located far from the walls are in remarkable agreement with ideal unperturbed chains in both calculations. The shapes and orientations of chain segments located near the walls are substancially different from those in the bulk. Starting from the walls, n‐tridecane exhibit progressively less dense and less ordered segmental layers of ca. 0.4 nm thickness, with most of the units in the first segmental layer belonging to nearly two‐dimensional chains. Long chains with center of mass close to the walls assume open, practically two‐dimensional conformations comprised mainly of surface trains and loops. The interface corresponds then to a region where the conformations of the chains evolve from these nearly two‐dimensional structures near the walls to the unperturbed, three‐dimensional Gaussian conformations in the bulk.
Polymer interfaces and ultrathin films characterized by optical evanescent wave techniques
Authors: Knoll Wolfgang , Hickel Werner , Sawodny Michael , Stumpe Joachim , Schmitt Franz‐Josef , Knobloch Harald 
Published: March 2011

AbstractPolymer surfaces and ultrathin films are characterized by novel optical techniques based on evanescent waves. We first describe photo‐ablation studies with polysilane films investigated by surface plasmon microscopy, a technique which is particularly well‐suited for ultrathin samples. Thicker films that are homogeneous enough to carry optical waveguide modes can be characterized with high lateral resolution by the recently developed waveguide microscopy. The next example concerns the application of surface plasmon microscopes to the investigation of a biopolymer adsorption from an aqueous phase to a functionalized membrane interface: We present a quantitative kinetic analysis of the specific recognition reaction between streptavidin and biotin. Finally, we report on surface plasmon field‐enhanced Raman‐spectroscopic and imaging investigations of ultrathin Langmuir‐Blodgett‐Kuhn‐layers of cadmium arachidate.
Cationic polymerization of alkenes and heterocyclics. More similarities than differences
Authors: Matyjaszewski Krzysztof 
Published: March 2011

AbstractThe cationic polymerization of alkenes and heterocyclics is compared in a critical way. After a brief introduction to the polymerizability of various monomers and efficiency of initiators, various active sites involved in propagation are discussed. They include covalent species, onium ions and carbenium ions of different degrees of association. Proportions and reactivities of these active sites are discussed for different monomers. Structure‐reactivity correlations for both systems are described. The construction of a general unifying theory of cationic polymerization is attempted, with peculiarities typical for each system pointed out.
Synthesis and polymerization of imines and azadienes: New polymerizable monomers
Authors: Hall H. K. 
Published: March 2011

AbstractWe have begun an exploratory program on the synthesis of imines and azadienes (α, β‐unsaturated imines) to find the best structures for monomers which will form high polymers. Imines display a very wide range of stability from existing only in the gas phase or at liquid nitrogen temperatures to complete stability depending on the substituents on the nitrogen and carbon. Among the simple imines, benzylidene cyanamide gave oligomers of DP‐8 with either free radical or anionic initiators. Tricyanomethanimine, C4N4, could only be obtained in solution and spontaneously homopolymerized and copolymerized with paramethoxystyrene. Among the l‐azabutadienes, 1‐phenyl‐l‐aza‐1,3‐butadiene polymerized to reasonably high molecular weight polymers using anionic initiators. Cationic initiation was less successful and free radical initiators gave no polymers. Similarly, N‐carboethoxy‐3‐methyl‐l‐aza‐l,3‐butadiene gave moderate yields of polymers with modest molecular weights. Our conclusions at this stage of our investigations are that simple imines are a quite restricted class of monomers. On the other hand, owing to ease of synthesis and ability to polymerize the l‐azadienes represent a new class of reactive monomers.
Palladium catalyzed routes to polyimides
Authors: Perry Robert J. , Turner S. Richard 
Published: March 2011

AbstractSeveral polyimides were prepared by the palladium catalyzed carbonylation and condensation of tetraiodoaromatic compounds and diamines. This new reaction for preparing polyimides was found in model compound work to be an efficient, high yield route to cyclic imides. Since fully imidized groups are formed during the polymerization, it was necessary to limit the diamines to those that would impart solubility to the polymer. In contrast to the model compound work, the polymerization reaction yielded an appreciable concentration of amide functional groups due to incomplete cyclization and/or branching reactions. Mixed haloaromatic compounds were also examined as monomers in this reaction. Model reactions between o‐bromoiodobenzene and aniline indicated that amide formation through the iodide was preferred and that imide formation through the bromide occurred later. Extension of this chemistry to dibromodiiodobenzene and diaminophenylindane DPI, gave low molecular weight oligomers at low phosphine levels and branched material at higher levels.
Aromatic biphenylene polymers: Synthesis via nickel coupling of aryl dichlorides
Authors: Kwiatkowski G. T. , Colon I. , El‐Hibri M. J. , Matzner M. 
Published: March 2011

AbstractA new method for the formation of high molecular weight aromatic biphenylene polymers via the nickel coupling of aromatic dichlorides is described. Aromatic biphenylene polymers display a number of highly attractive features which are discussed. The novel reaction is performed in a dry aprotic solvent (e.g., in DMAC) using catalytic amounts of zero‐valent nickel, triphenylphosphine ligand and excess zinc metal. The reactions must be performed under an inert atmosphere and in the absence of water. In order to obtain high polymer, one must use low amounts of nickel, high triphenylphosphine/nickel ratios, excess zinc metal, and moderate temperatures (70 °C). Variables such as the choice of ligand or co‐ligand, salt addition, ligand and zinc concentration, etc … allow for optimization of the reaction efficiency. The method is general and allows for the preparation of an almost infinite variety of polymers. Polymerizations and copolymerizations involving aryl dichlorides possessing dissimilar chloro‐moieties are particularly intriguing since a number of sequence distributions are possible. The two prerequisites for a successful preparation of high molecular weight product are solubility of the monomer, and more particularly of the obtained polymer, in the reaction medium; and the necessity that any functional groups present in the monomer(s) (and in the resulting polymer) be inert toward the zinc/nickel system.Critical features of the polymerization mechanism are also reviewed.
A germylene and stannylene as polymerization comonomer and initiator
Authors: Kobayashi Shiro , Iwata Satoru , Abe Mitsunori , Yajima Kazuo , Kim Hyun Joon , Shoda Shin‐ichiro 
Published: March 2011

AbstractNovel polymerization reactions utilizing a divalent germanium or tin species, germylene or stannylene, have been developed. Copolymers having a germanium(IV) or tin(IV) unit in the main chain have been prepared by the reaction of oxidant monomers (Mox) and reductant monomers (Mred, germylene or stannylene). Oxidant monomers employed are p‐benzoquinones, N‐phenyl‐p‐quinoneimines, cyclic α, β‐ unsaturated ketones, and cyclic sulfides. A new aspect of these divalent chemical species as an initiator for vinyl monomers has also been investigated.