bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of membranes having a saccharide side chain and their optical resolution properties for d‐/l‐ glucose mixtures
Authors: Nakagawa Tsutomu , Toyokawa Yoshida , Abe Motoji , Higuchi Akon 
Published: March 2011

AbstractThe objective of the present investigation is to synthesize new polymeric membranes having a saccharide in the side chain and to clarify the specific affinity of the saccharide chains. During this study chloromethylated polysulfone (CM‐PSF), poly(chloromethylated styrene) (P‐CM‐St), poly(methyl methacrylate) (PMMA), and chlororethylated poly(γ ‐methyl L‐glutamate) (CE‐PMLG) as synthetic polymers along with an equal mixture of α‐D‐2‐deoxy‐2‐aminoglucopyranosyl‐(1'→6) ‐D‐sorbitol and mannitol (AGP) as saccharides were used. PMMA+AGP and CE‐PMLG+AGP membranes showed the highest permeability of D‐glucose in sugars (molecular weight = 180.16), although the CM‐PSP+AGP and P‐CM‐St+AGP membranes showed less permeability. The reason for the high permeability of D‐glucose is the high partition coefficient of D‐glucose, which may come from an interaction between the AGP terminating D‐glucose structure and D‐glucose as the solute. The optical resolution could be done by the difference between the D‐ and L‐glucose permeation rates from an equimolar mixture of D‐glucose and L‐glucose.
Proton transfer reactions in aqueous solution of 2‐vinylquinoline copolymers
Authors: Morales Elena , Gómez‐Antón M. Rosa , Piérola Inés F. 
Published: March 2011

AbstractFluorescence spectra of atactic and isolaclic poly‐2‐vinylquinoline and copolymers of 2‐vinylquinoline and four non fluorescent comonomers have been measured as a function of pH. The homopolymers and the copolymers with pyrrolidone show two band fluorescence spectra; their intensity ratio changes with pH, polymer concentration and excitation wavelength. For the other copolymers the emission of the protonated heterocycle is only a shoulder of the emission of the neutral form. A kinetic scheme has been proposed to explain these results.
Optical effects in stratified colloidal particles near transparency
Authors: Alexander‐Katz Roberto , De La Rosa Aída , Rojas Fernando , Contreras Claudia , Cardoso Judith 
Published: March 2011

AbstractNon‐isotropic scattering patterns showing a minimum for small and almost transparent core‐shell particles are discussed. It is shown that for any particle size, close to transparency, a core‐shell particle behaves optically differently from a non‐structured particle due to the presence of a minimum in the scattering pattern. Transparency criteria are discussed in the light of the non‐isotropic character of the scattered light. Direct experimental evidence of the existence of this minimum is presented and compared with the theoretical predictions of the scattering by colloids having a distribution of particle composition.
Structure and thermodynamics of polystyrene‐block‐poly(ethylene/propene) micelles in selective solvents
Authors: Katime Issa , Villacampa Manuel , Quintana José R. 
Published: March 2011

AbstractThe concentration and temperature dependencies of micelle formation by a polystyrene‐block‐poly(ethylene/propene) copolymer in several ketones (2‐butanone, 3‐pentanone, 4‐methyl‐2‐pentanone, 4‐heptanone, 5‐methyl‐2‐hexanone and 5‐methyl‐3‐heptanone) were studied by static and dynamic light scattering, viscometry and size exclusion chromatography. No micelles were detected in solutions of 5‐methyl‐3‐heptanone. The standard Gibbs energy, ΔG°, the standard enthalpy, ΔH°, and the standard entropy, ΔS°, of micellization were estimated. The values of ΔG° and ΔH° were negative for all ketones studied and depended on the polar character of the ketone. The micelles showed larger association numbers and densities independent of the ketone. Micelle dimensions hardly depended on the ketone.
Blends of poly(n‐vinyl‐2‐pyrrolidone)/poly(monoitaconates) II. The coefficient of linear expansion
Authors: Opazo Alejandra , Gargallo Ligia , Radic Deodato 
Published: March 2011

AbstractBlends of poly(monoitaconates)b) containing different side chain structures with poly(N‐vinyl‐2‐pyrrolidone) (PVP) of three different weight‐average molecular weights (M̄w) were studied by thermomechanical analysis. Blends containing PVP of M̄w =10000 shows a monotonous variation of the coefficient of linear expansion α against composition but PVP samples of higher molecular weights present a minimum which is attributed to polymer‐polymer complex due to strong specific interactions.
Binary polymer blends involving multiple specific interaction sites: Poly(vinyl methyl ether) blends with an ethyl methacrylate‐co‐4‐vinyl phenol copolymer
Authors: Xu Yun , Bhagwagar Dorab E. , Painter Paul C. , Coleman Michael M. 
Published: March 2011

AbstractWe report the results of experimental infrared and thermal analysis studies of binary miscible blends of poly(vinyl methyl ether) (PVME) with an ethyl methacrylate‐co‐4‐vinyl phenol (EMAVPh) copolymer. This is a complex blend system, involving multiple specific interaction sites. Using the concept of competing equilibria we show that the equilibrium constant describing hydrogen bonding between the OH group of EMAVPh and the ether oxygen of PVME can be determined from quantitative infrared spectroscopic analysis of the fraction of hydrogen bonded carbonyl groups present in miscible binary blends.
Synthesis, structure, and swelling behavior of two‐component copolymer networks
Authors: Shiomi Tomoo , Tezuka Yasuyuki , Okada Koji , Imai Kiyokazu , Hayashi Hisao 
Published: March 2011

AbstractA two‐component copolymer network comprising polystyrene (PS) and poly(dimethylsiloxane) (PDMS) as copolymer components was prepared by cross‐linking PS with telechelic PDMS with a new method. The microphase structure of the dry PS/PDMS network was found to be irregular from DSC and small angle X‐ray scattering measurements. The swelling behavior was observed in three kinds of mixed solvents which were chosen so as to contrast with one another in respect of solubility of the component polymers. The observed swelling degree depended on the solvent composition in a manner peculiar to the respective mixed solvent systems. The Flory swelling equation extended to the two‐component polymer network qualitatively reproduced the experimental swelling behavior.
Kinetics of styrene uptake by a polyurethane network during the formation of interpenetrating polymer networks
Authors: Derrough Samir N. , Widmaier Jean‐Michel , Meyer Guy C. 
Published: March 2011

AbstractDue to insolubility of the components, formation of interpenetrating polymer networks (IPNs) requires particular ways of synthesis. Among others, IPNs can be prepared by the sequential technique where a network is swollen in a monomer and its crosslinker, which are then polymerized in situ. The simplest case is to swell at equilibrium; however this leads to IPNs of a given composition. For obtaining other compositions, swelling has to be stopped before equilibrium, or the swollen network (gel) has to be deswollen to a certain extent. Therefore, diffusivity of the monomer within the gel has to be known. The kinetics of monomer uptake was studied for a polyether urethane/styrene‐divinylbenzene system which gives transparent materials despite the difference in refractive indexes. This allows direct visual observations of the monomer progress within the network. The results are not fully in agreement with the theories of Tanaka and of Candau which both predict the progression of a solvent in a polymeric gel. Two regimes of swelling depending on the concentration distribution of the monomer within the gel were found.
Dynamics of cyclic poly(methylphenylsiloxane)
Authors: Maçanita Antonio L. , Horta Arturo , Piérola Inés F. 
Published: March 2011

AbstractFluorescence spectra of cyclic poly(methylphenylsiloxane)s having 3, 4.4 and 9.0 monomelic units, and of the monochromophoric analog methylphenyldimethoxysilane (MS), were measured as a function of temperature in the range 150 to 320 K. Both the low‐ and the high‐temperature limits were reached in this range. The crossover temperature between both limits was thus determined, as well as the activation energy for excimer formation and the excimer binding enthalpy. From measurements of the lifetime of MS as a function of temperature, the rate constant for excimer formation was also determined, and its relationship with the rate constant for rotation through backbone bonds was discussed.
Developments in the cationic polymerization of alkenes — A personal view
Authors: Plesch Peter H. 
Published: March 2011

AbstractIn this paper the author presents some of his contributions to the theory and practice of the cationic polymerization (C.P.) of alkenes since 1944. The first phase of his work at the University of Manchester comprises the discovery of co‐catalysis by water with TiCl4, the invention of the pseudo‐Dewar reaction vessel, the use of trichloroacetic acid as co‐catalyst, and the disproof of the alleged cationic isomerization of cis‐stilbene.
Salt and solvent effects in “living” carbocationic polymerization
Authors: Matyjaszewski Krzysztof , Lin Chih‐Hwa , Bon Angélique , Xiang Jason S. 
Published: March 2011

AbstractCarbocationic polymerization is strongly affected by medium and salt present in the system. The increase of solvent polarity enhances overall rates of cationic polymerization because it increases the proportion of carbocations in equilibrium with dormant covalent species. Higher solvent polarity might also increase molecular weights due to the reduction of transfer to counterions and may broaden polydispersity by slowing down an exchange between active and dormant species. Added salts may increase the proportion of ionic species by the ionic strength effect. The salts with common ions suppress free ions and lead to a monomodal molecular weight distribution by eliminating free ionic species with long lifetimes. The addition of tetrabutylammonium salts in the polymerization of styrene, initiated by 1‐phenylethyl chloride and catalyzed by tin tetrachloride is a typical example. The special salt effect based on exchange of counterions may enhance or reduce the proportion of ionic species and may accelerate the exchange between active and dormant species, affecting the polymerization rates and polydispersities.
New biomaterials by carbocationic processes
Authors: Kennedy J. P. 
Published: March 2011

AbstractWell‐defined macromolecular composites have been prepared by living carbocationic polymerization of isobutylene in combination with other conventional techniques. The products were designed for biomedical uses as 1) intervertebral disc replacement, 2) improved impact‐ and fatigue‐ resistant bone cements, 3) delayed drug release reservoirs, and 4) small diameter nonthrombogenic vascular grafts. The syntheses are out‐lined, and the novelty, main characteristics and properties of these unique materials are summarized. The era of designed biomaterials is upon us.
Direct and sensitized photoinitiated cationic polymerization using pyridinium salts
Authors: Yaǧci Yusuf , Schnabel Wolfram 
Published: March 2011

AbstractResults of polymerization and laser flash photolysis studies concerning the direct and indirect photoinitiation of cationic polymerizations using N‐alkoxy pyridinium and N‐alkoxy quinolinium salts are presented. The indirect action can be based on (a) the generation of carbocations via the oxidation of photochemically produced free radicals and (b) the generation of radical cations via the reaction of electronically excited sensitizers with pyridinium or quinolinium ions. With respect to (a) substituted vinyl bromides were found be an effective source of oxidizable free radicals (vinyl radicals), and regarding (b) singlet or triplet excited states of thioxanthone, anthracene, perylene and phenothiazine, which, in the ground state, strongly absorb light in the 300 to 400 nm range, were found to react rapidly with pyridinium salts.
Polyethers containing stable ionic end‐groups
Authors: Kubisd Przemyslaw , Tadeusz Biedron 
Published: March 2011

AbstractPolyethers of low and medium molecular weight containing at both ends stable ionic groups (phosphonium ions) were obtained by living cationic polymerization of tetrahydrofuran initiated by difunctional initiator, trifluoromethanesulfonic anhydride, followed by termination with triphenylphosphine. It was shown, that products contain significant quantities of low molecular weight diphosphonium salt; a plausible explanation is presented. Alternative approach to the synthesis of diionically terminated polyethers was based on the conversion of hydroxyl end‐groups of polyether diols, which can be obtained by cationic Activated Monomer (AM) polymerization of e.g. oxiranes, into phosphonium ion end‐groups. Using this approach, poly(ethylene oxide)'s with Mn ranging from 300 to 3400, terminated at both ends with stable ionic groups, were prepared and characterized. Measurements of NMR relaxation times and viscosity measurements provide the evidence for the aggregation of ionic end‐groups. The potential applications of inter‐ and intramolecular aggregation are discussed. It is shown, that intramolecular aggregation of ionic terminal groups in low molecular weight poly(ethylene oxide) leads to cyclic structures resembling crown ethers and showing comparable efficiency for complexing cations.
Stereoregular and conformationally regular oligomers and polymers
Authors: Vogl Otto , Simonsick William J. , Bartus Jan , Qin Meifang , Ute Koichi , Hatada Koichi 
Published: March 2011

AbstractConfigurationally and conformationally regular polymers can now be synthesized based on sterically restrictive considerations. Trihaloacetaldehyde polymerization provided a fertile field for the investigation of the factors for such polymer formations. The convenient ceiling temperature of trihaloacetaldehyde polymerizations allowed the study of the genesis of these polymerizations. Oligomers were prepared by alkoxide initiation, followed by the establishment of the oligomer alkoxide equilibrium and end‐capping. Stereoregularity and conformational regularity were observed in trichloroacetaldehyde (chloral) and tribromoacetaldehyde (bromal) polymerizations. This result was confirmed by solid state magic angle spinning NMR investigations of polychloral, of polybromal as well as of a copolymer of chloral and bromal. Solid state NMR techniques allowed also to investigate copolymers of chloral and aromatic isocyanates. Quantification of the solid state investigation suggests the possibility of a molecular weight estimation of chloral and other insoluble trihaloacetaldehyde polymers by end‐group analysis.
Interactions between ions and free or immobilized ligands. Application of the competition method
Authors: Smid Johannes 
Published: March 2011

AbstractApplication of a competition method to determine affinities of ligands for ionic species in low polarity media is described. A soluble ligand, L, and a network‐immobilized ligand, N, are allowed to interact with the counterion of an ionic chromophore A” according to the reaction NM+A− + L → LM+A− + N (K). K values were determined in toluene and in ether‐type solvents for linear and macrocyclic polyethers and polyamines, as well as for other cation‐complexing agents, by varying either N or L. In solvents such as dioxane, binding constants of M+A− to N can be determined directly. Combined with K values they yield the complex formation constant, KL, of the reaction M+A− + L → LM+A−.
Synthesis of macrocyclic polystyrene‐polydimethylsiloxane block copolymers
Authors: Yin Rui , Amis Eric J. , Hogen‐Esch Thieo E. 
Published: March 2011

AbstractA series of macrocyclic polystyrene (PS)‐polydimethylsiloxane (PDMS) block copolymers and similar block copolymers was synthesized by sequential polymerization of styrene and hexamethyl cyclotrisiloxane (D3) initiated by a difunctional anionic initiator in THF at −78° followed by coupling with Cl2SiMe2 in very dilute (10−5 – 10−6 M) solutions. Total molecular weights ranged from about 2–85 × 103. The formation of monodisperse macrocyclic block copolymers was indicated by the lower (15–30%) hydrodynamic volume of the rings compared to that of the linear block copolymers. Carbon‐13 and 29Si NMR likewise supported the absence of linear polymer in the macrocyclic block copolymer. The behavior of second virial coefficient A2 of the rings and the linears versus temperature was examined by static light scattering in cyclohexane. Below 20° the A2 for the linear polymer goes negative while that for the cycle remains positive. Dynamic light scattering (DLS) as a function of temperature also reflects that the cyclic polymers remain well solvated even down to 12°C. The DLS autocorrelation functions for the linear triblock however demonstrate the onset of aggregation and phase separation as the temperature is reduced below 20°C.
Role of bimetallic active centres in anionic polymerization of hydrocarbon monomers
Authors: Arest‐Yakubovich Alexander A. 
Published: March 2011

AbstractPolymerization of hydrocarbon monomers initiated by organometallic compounds of alkali and alkaline earth metals modified by derivatives of other metals of Groups I‐III is reviewed. Various mixed initiators, such as RLi‐RONa, RLi‐RNa, R2Ba‐R3Al, RNa‐R3Al, are discussed in details. It is shown that the presence of a second metal greatly affects the kinetics of elementary steps of chain propagation and chain transfer and also the structure and molecular weight of polymer formed. Active centres in all the systems are complexes containing two or more metal atoms linked by a bridge bond; the addition of a monomer occurs by an insertion either into the “usual” metal‐carbon bond which is external with respect to the polymetal nucleus of the complex or directly into Mt1‐R‐Mt2 bridge bond.
Preparation and properties of isotactic and syndiotactic poly(methyl methacrylate)s, uniform with respect to molecular weight
Authors: Hatada Koichi , Ute Koichi , Kitayama Tatsuki , Nishiura Takafumi , Miyatake Nobuo 
Published: March 2011

AbstractHighly isotactic (it‐) and highly syndiotactic (st‐) poly(methyl methacrylate)s (PMMAs) uniform with respect to molecular weight (stereoregular, uniform PMMAs) were isolated up to the 100mer from it‐ and st‐PMMAs by supercritical fluid chromatography (SFC) and characterized by NMR and mass spectroscopies. Glass transition temperatures (Tg's) of the uniform it‐ and st‐PMMAs were higher than those of the corresponding PMMAs with MWD and with similar molecular weight on average. The Tg values of the uniform it‐and st‐PMMAs series obeyed the relationship, Tg = Tg∞ ‐ K/M, where M and Tg∞ denote molecular weight and Tg at infinite M, respectively. The reciprocal melting points (1/Tm) of uniform it‐PMMA (degree of polymerization, DP = 28–44), obtained from methanol solutions by evaporating the solvent, increased linearly with increasing 1/DP. Extrapolation of the linear relation to 1/DP = 0 gave the Tm of it‐PMMA with infinite DP; Tm∞ = 171.1°C. Thermal degradation behavior was studied by thermogravimetry and by SFC analysis of degradation products. In gel‐permeation chromatography (GPC) measurements, the it‐50mer eluted faster than the st‐50mer. Calibration curves for it‐ and st‐PMMAs could be obtained using series of the uniform PMMAs. The instrumental spreading factor determined using it‐25mer, it‐50mer, st‐25mer and st‐50mer for our GPC chromatograph was 0.070 ml when the volume of the sample solution was 0.003ml. GPC analysis of a mixture of the it‐ and st‐50mers in tetrahydrofuran indicated formation of a stereocomplex in the solution, and was found quite useful to elucidate the minimum sequence length required for complex formation.
1H and 13C NMR of PMMA macromonomers and oligomers ‐ end groups and tacticity
Authors: Mccord Elizabeth F. , Anton Waifong L. , Wilczek Lech , Ittel Steven D. , Nelson Lissa T. J. , Raffell Keith D. , Hansen Joan E. , Berge Charles 
Published: March 2011

Abstract1H NMR and 13C NMR have been used to study the end groups and tacticity in PMMA macromonomers and oligomers. These macromonomers are terminated almost exclusively in one vinylidene group per chain. The end group signals from the macromonomers are identified in both the 13C and 1H NMR spectra. The spectra of the purified oligomers (n = 1‐4) were used to aid in assignment. The macromonomers are predominantly syndiotactic, and the tacticity measured is consistent with Bernoullian statistics. The tetramer is a mixture of r and m isomers in a 4:1 ratio. It is shown that T1 experiments can provide a useful method of distinguishing resonances due to low molecular weight impurities from those due to stereochemical or isomeric effects in macromonomers. The absence of internal double bonds was confirmed by isomerizing the vinylidene group of several oligomers and of the macromonomer, and verifying the absence of the isomerized signals in the NMR spectra of the original materials.
NMR spectroscopy of poly(vinyl chloride) defects. 2. 1H and 13C NMR analysis of the terminal vinyl end group, 1,3‐dichlorobutyl end group and chloromethyl branch
Authors: Benedikt George M. , Goodall Brian L. , Rhodes Larry F. , Kemball Alan C 
Published: March 2011

AbstractWe have been able to obtain the 1H NMR subspectra of most of the major saturated end groups in PVC. In order to assign the terminal vinyl (TV) group, CH2CH‐CHCl‐, we synthesized and analyzed the symmetrical model compound 3,5‐dichloro‐1,6‐heptadiene (4) containing a racemic (r) and a meso (m) isomer. They exhibit distinct NMR signals for the vinyl protons, which allowed us to subsequently assign the r diad and the previously unreported m diad terminal vinyl resonances present in very small amounts in commercial PVC. The study of the solvent induced chemical shifts of the vinyl protons in an experimental PVC sample containing an unusually high level of this end group allowed us to further assign it in terms of the terminal rr, rm, mm and mr triads.
Solution and solid‐state NMR analysis of phenolic resin cure kinetics
Authors: Neiss Thomas G. , Vanderheiden Egbertus J. 
Published: March 2011

AbstractPhenolic condensate resins, produced from the reaction of phenol with formaldehyde, are important components in the chemical industry and have a wide variety of applications. Resins of this type are used in the aerospace industry to produce rocket motor components with strength and rigidity. While methods currently exist (e.g., DMA, DEA, calorimetry) for the examination of phenolic‐based systems during the curing process, none are available to directly measure the functionality and chemical degree of resin advancement during this process. Solution and solid‐state 13C NMR spectroscopy can be implemented to examine the functional group content of the resin. Reactant and product moieties are spectrally resolved in both techniques and can be monitored during resin cure. 1H wide‐line solid‐state NMR can be used to measure the rate of sample curing in situ by monitoring the sample T2 relaxation time as a function of sample heating time. Comparison of these results with the 13C NMR data will establish the degree of resin cure on a functional group basis.
Solid‐state characterization of polysilanes containing the sih bond
Authors: Schilling Frederic C. , Weidman Timothy W. , Joshi Ajey M. 
Published: March 2011

AbstractOrganosilicon hydride polymers show promise for high performance photoresist, dielectric, and optical coating applications. In this report we describe the solid‐state characterization of these silicon‐based polymers prepared by reductive condensation and plasma polymerization methods. The combination of high resolution solid‐state NMR, infrared, and Rutherford backscattering spectroscopies provides a quantitative description of the polymer microstructure. As a result of these studies the effects of polymerization conditions on polymer microstructure can be more readily determined and optimized.