bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and solution properties of poly(2‐methylproline)
Authors: Overberger C. G. , Jon Y. S. 
Published: April 2003

AbstractThe resolution of 2‐methylproline and the assignment of absolute configuration to the stereoisomer has been carried out. The L‐enantiomer was obtained from the fractional crystallization of the quinine salt of (−)‐N‐carbobenzoxy‐2‐methylproline and the D‐enantiomer from the collected filtrates. The (−)‐2‐methylproline was assigned the L‐configuration by means of the Clough‐Lutz‐Jirgensons method. Polymers were obtained in bulk from the N‐carboxyanhydrides. Although polymers obtained from different solvents exhibited different solubility properties, subsequent spectral studies indicated that this effect was not due to a large conformational change as in the polyproline case. Spectral evidence suggests that poly(2‐methylproline) (P2MP) exists as a polyproline type II helix.
Alternating ethylene–alkyl acrylate copolymers. I. polymer preparation
Authors: Logothetis A. L. , McKenna J. M. 
Published: April 2003

AbstractHigh molecular weight alternating ethylene–ethyl acrylate copolymers were prepared by using boron trifluoride to complex the acrylate ester. The polymerizations were run under mild conditions (25–50°C, 6–20 atm ethylene) in dichloromethane or dichloroethane solution with free‐radical initiation. At lower ethylene pressures or at less than stoichiometric levels of BF3, the polymers are acrylate‐rich. This is due to ethyl acrylate homopolymerization competing with the copolymerization reaction. The effect of other polymerization variables is also discussed.
Zur kopolymerisation: Axiomatische formulierung eines mathematischen modells, das memory 3 programm—anwendungen
Authors: Mot̨oc Ioan , Holban Stefan , Ciubotariu Dan 
Published: April 2003

AbstractThis paper presents an axiomatic mathematical model for binary copolymerization reactions. The FØRTRAN program entitled MEMØRY 3 is described. This program implements the Monte Carlo version of the axiomatic model, computing the most probable sequence distribution. Finally, a concrete copolymerization process is studied and good results are presented.
Copolymerization of 2‐hydroxypropyl methacrylate with alkyl acrylate monomers
Authors: Gaddam N. B. , Xavioir S. F. , Goel T. C. 
Published: April 2003

Abstract2‐Hydroxypropyl methacrylate has been copolymerized with methyl acrylate, ethyl acrylate, n‐butyl acrylate, and methyl methacrylate in bulk at 60°C using benzoyl peroxide as initiator. The compositions of copolymers have been determined by the estimation of the hydroxyl group by acetylation process. The copolymerization parameters have been determined by conventional scheme of copolymerization.
Grafting onto wool. I. Ceric ion‐initiated grafting of poly(methyl acrylate) onto wool
Authors: Misra B. N. , Chandel P. S. 
Published: April 2003

AbstractPoly(methyl acrylate) has been grafted onto wool by using ceric ion as redox initiator in an aqueous medium. Initiation by ceric ammonium nitrate (CAN) was carried out in the presence of nitric acid of varying concentration at 35, 45, and 50°C for a period of 1.5 or 3 hr. Percent grafting was found to be dependent on concentrations of acid and monomer, reaction time, and temperature. Above 45°C, a considerable amount of homopolymer was formed; at 35°C, very little grafting of poly(methyl acrylate) was observed. Nitric acid catalyzed the reaction and a concentration of 0.17–0.19M HNO3 was found suitable.
Grafting onto wool. II. BPO‐initiated grafting of polystyrene
Authors: Chandel P. S. , Misra B. N. 
Published: April 2003

AbstractGrafting of polystyrene (PS) onto wool has been carried out in aqueous medium by use of benzoyl peroxide (BPO) as initiator in the presence of an acetic acid–pyridine mixture which acted as a pH modifier. Percent grafting was found to be dependent on concentration of acetic acid and pyridine, concentration of monomer, concentration of BPO, and reaction temperature. The role of pH modifier upon BPO‐initiated grafting is established by the observation that no grafting occurred when one of the components of the pH modifier was absent.
Preparation and properties of solvent‐soluble bridged polybiphenylenes and related copolymers
Authors: Hayama Shigeru , Niino Shogo , Sakamoto Akira 
Published: April 2003

AbstractA solvent‐soluble polybiphenylene with a single hetero atom in the chain (a bridged polybiphenylene) was prepared according to the synthetic procedure for a solvent‐soluble poly(4,4′‐biphenylene). In addition, a related copolymer was similarly prepared by the addition of the MMA monomer in the reaction system. The thermal properties and viscosity behavior of each product were influenced by the hetero atom, especially by the introduction of MMA component in the chain. Each viscosity curve (ηsp/c vs. c) shows an anomalous peak at a specific concentration (0.3–0.002 g/100 ml DMF), depending upon the atomic group. The ηsp/c value for each homopolymer was not over 0.1 except in the neighborhood of the anomalous peak, while those for copolymers became 3–4 times larger than values for corresponding homopolymers. It is obvious that the viscosity of each copolymer increases due to an increase in flexibility due to introduction of the MMA units in the chain, since little difference in molecular weights is found between homopolymers (16,000–15,000) and copolymers (10,000–12,000).
Reactivity ratios for acrylonitrile–phenyl acrylate copolymerization systems
Authors: Miller Andrzej , Szafko Jerzy 
Published: April 2003

AbstractReactivity ratios for various acrylonitrile–phenyl acrylate systems have been determined for radical copolymerization at 60°C in dimethylformamide. The values of the ratios calculated by the linear graphical method of Kelen and Tüdös were as follows: r1 = 0.46 ± 0.02 and r2 = 0.36 ± 0.04 for acrylonitrile–phenyl acrylate, r1 = 0.73 ± 0.02 and r2 = 0.80 ± 0.02 for acrylonitrile–p‐cresyl acrylate, r1 = 0.33 ± 0.03 and r2 = 0.9 ± 0.02 for acrylonitrile–p‐chlorophenyl acrylate, r1 = 0.82 ± 0.03 and r2 = 1.02 ± 0.03 for acrylonitrile–p‐bromophenyl acrylate, r1 = 1.12 ± 0.05 and r2 = 1.16 ± 0.05 for acrylonitryle–o‐chlorophenyl acrylate, and r1 = 1.26 ± 0.05 and r2 = 0.86 ± 0.05 for acrylonitrile–m‐chlorophenyl acrylate. The dependence of reactivities of the monomers upon their chemical structure was discussed.
Equilibrium cyclotrimerization of n‐butyraldehyde
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Kawase Sanshiro 
Published: April 2003

Abstractn‐Butyraldehyde was cyclotrimerized by using boron trifluoride etherate as an initiator at −10 to 25°C under various conditions, e.g., in methylene chloride, in toluene, and without adding solvent. An equilibrium between the monomer and its cyclic trimer was observed, the equilibrium constant being highly dependent on not only the reaction temperature and the kind of solvents, but also the initial monomer concentration. A consistent interpretation for the results was obtained by the thermodynamic treatment of the equilibrium system as a nonideal solution composed of the monomer, its cyclic trimer, and solvent, in consideration of the intermolecular interactions between any two components.
Study of energy transfer to solvent in radiation graft polymerization of styrene onto polyethylene
Authors: Rabie Abdelgawad , Odian George 
Published: April 2003

AbstractThe radiation‐initiated graft polymerization of styrene onto polyethylene was studied to determine whether energy transfer to diluent was responsible for the previously observed high orders of dependence of the grafting rate on monomer concentration. n‐Octane was used as the diluent instead of benzene. If energy transfer from excited polyethylene to benzene were present, it should not be with n‐octane. The percent swelling of polyethylene by various n‐octane–styrene mixtures was determined. The compositions of various n‐octane–styrene mixtures absorbed inside polyethylene were determined by ultraviolet and refractive index measurements and found to be richer in styrene than the corresponding mixtures in which the polyethylene had been placed. The graft polymerization rates were determined at 0.000761, 0.0371, and 0.213 Mrad/hr and plotted against the inside styrene concentrations on a log‐log scale to yield the kinetic orders of dependence of rate on monomer as 2,3, and 3, respectively. It was concluded that energy transfer to diluent was not responsible for the high‐order dependence observed.
Photodegradation of polyethylene in the presence of ferric chloride
Authors: Ogiwara Yoshitaka , Kimura Yuji , Osawa Zenjiro , Kubota Hitoshi 
Published: April 2003

AbstractEffects of ferric chloride (FeCl3) on photodegradation of high‐density polyethylene (PE) were investigated by using ESR and infrared spectrometry. In the system with irradiation at light of λ > 220 nm, PE irradiated at 77°K yielded an 8‐line spectrum, the intensity of which was markedly weakened by using FeCl3 with the sample, indicating a distinct depression of radical formation. On the other hand, PE with the use of FeCl3 yielded radicals under irradiation only with light of λ > 300 nm, showing a singlet spectrum with a line width of 15 gauss. For photooxidized PE, almost the same effect of FeCl3 was observed. On irradiation at room temperature, PE samples with and without FeCl3 showed a singlet spectrum with line widths of 15 and 25 gauss, respectively. On the other hand, the unsaturated double bond contained in a small amount in PE sample was observed by infrared study to be decreased with photoirradiation; however, the decrease was sharply depressed with the addition of FeCl3 to the sample. The degradation of carbonyl group in a photooxidized sample was markedly affected by photoirradiation, and the decay was obviously reduced for the sample on addition of FeCl3. It is concluded that FeCl3 works upon photodegradation of PE to enhance the Norrish type II reaction and to accelerate the formation of unsaturated double bond in the chain.
Adsorption of polymers at the solution–solid interface. XIII. Adsorption and steric stabilization with styrene–2‐vinylpyridine copolymers
Authors: Howard G. J. , McGrath M. J. 
Published: April 2003

AbstractRandom and block copolymers of styrene and 2‐vinylpyridine, covering the full range of composition, have been synthesized. The adsorption of these polymers from trichloroethylene solution on to precipitated silica has been studied and their ability to impart colloidal stability to the silica dispersions also investigated. Estimates of the layer thickness of adsorbed copolymers have been made. Polystyrene is not adsorbed from trichloroethylene and does not stabilize dispersions of precipitated silica. A random copolymer having 1% 2‐vinylpyridine units is adsorbed but shows very little steric stabilization. Random copolymers of 2‐vinylpyridine content greater than 10% and AB block copolymers of more than 6% 2‐vinylpyridine behave very similarly in respect both of the quantity adsorbed and in their ability to stabilize silica suspensions. Layer thickness does not seem to depend on copolymer composition. Random copolymers with low to intermediate 2‐vinylpyridine contents are better steric stabilizers in trichloroethylene than are the corresponding copolymers of methyl methacrylate with styrene: this is attributed in part to the longer sequences of adsorbable units in the vinylpyridine copolymers.
Adsorption of polymers at the solution–solid interface. XIV. Adsorption and steric stabilization with styrene–acrylonitrile copolymers
Authors: Howard G. J. , McGrath M. J. 
Published: April 2003

AbstractThe adsorption of random copolymers of styrene and acrylonitrile of azeotropic composition from their trichloroethylene solutions onto precipitated silica exhibits a maximum at intermediate molecular weights. These copolymers are able to stabilize dispersions of some, but not all, grades of precipitated silica; here, too, a maximum effect is found at intermediate molecular weights. Copolymers are partially desorbed by ethyl cyanide, which destabilizes silica dispersions. Block copolymers of low acrylonitrile contents do not stabilize well but, when preadsorbed, affect the behavior of subsequently adsorbed random copolymers. In particular, high molecular weight random copolymers flocculate the pretreated silica; silica with grafted polyacrylonitrile chains may also be flocculated by these copolymers.
Light‐induced decay of free radicals in wool keratin
Authors: Shatkay A. , Weatherall I. L. 
Published: April 2003

AbstractThe kinetics of free radicals created by blue light in wool keratin are interpreted in terms of two decay processes: a first‐order decay occurring spontaneously even in the dark, and another first‐order decay directly proportional to the light intensity. This interpretation is supported by an analysis of previous experimental results and by more direct new experimental evidence.
Effect of pressure on free‐radical copolymerization kinetics. I. A concept of additivity of partial molar volumes of activation
Authors: Van der Meer R. , German A. L. , Heikens D. 
Published: April 2003

AbstractA short review of the effect of pressure on copolymerization kinetics shows the necessity of simple models for a better understanding of activation volumes. Therefore, a simple concept, possibly generally valid for free‐radical polymerization, is proposed, based on the assumption that molar volumes of activation can be expressed as an addition of a characteristic radical and a monomer contribution, regardless of the combination involved. The scheme may facilitate the visualization of the transition state and contribute to the understanding of reaction mechanisms of radical polymerizations. Ethylene–vinyl acetate copolymerization at 62°C with tert‐butyl alcohol as solvent agrees with the proposed scheme, appearing from the pressure independence of the product of reactivity ratios at the different levels (35,600, and 1200 kg/cm2). Implicitly it can be shown that an ethylene monomer contributes about 2 cm3/mole more to the activation volumes of the propagation reactions than does the vinyl acetate monomer, whereas for the radicals the difference of the respective contributions to the activation volumes is opposite in sign.
Polymérisation anionique des diènes. VI. Microstructure des polybutadiène et polyisoprène par résonance magnétique protonique à 250 MHz et mécanismes de propagation
Authors: Salle Robert , Pham Quang‐Tho 
Published: April 2003

AbstractAnalysis by 250‐MHz proton magnetic resonance (PMR) allows more precise examination of the microstructure of anionic polyisoprenes and polybutadienes obtained in the presence of organo‐alkali metals. Besides vinyl addition, the propagation of contact ion pairs in dioxane solvent gives a mixture of cis and trans products with isoprene, whereas only trans product is obtained with butadiene. The presence of 1,4‐trans‐polyisoprene appears to be inconsistent with the cis configuration of the polyisoprenyllithium living end in dioxane or tetrahydrofurane media. In taking into account the existence of complexation phenomena, it was suggested that propagation mechanisms should involve a transition state which should begin with the trans configuration before isomerization into the more stable cis configuration. For the free ions, the living end of the carbanion should be entirely trans.
ESR studies of the radiation‐induced multiple graft polymerization
Authors: Omichi Hideki , Araki Kunio 
Published: April 2003

AbstractThe radiation‐induced multiple‐graft polymerization was studied by an ESR method. When methyl methacrylate vapor was introduced onto preirradiated polyethylene already grafted with styrene, the second step of grafting of methyl methacrylate occurred mainly in the polyethylene portion. The kinetic treatment proved that the termination rate constant kt of methyl methacrylate decreased with the amount of styrene grafted in advance. On the other hand, when styrene vapor was introduced onto polyethylene grafted with methyl methacrylate, only radicals of poly(methyl methacrylate) decreased. In this case, the second step of grafting of styrene occurred in the poly‐(methyl methacrylate) portion which covered the whole surface of the polyethylene powder. When monomer vapors were alternately introduced onto preirradiated polyethylene powder, the second step of grafting occurred at the growing chain end of the first monomer.
Synthesis of oligoesters and polyesters from oxalic acid and ethylene glycol
Authors: Alksnis A. , Deme Dz. , Surna J. 
Published: April 2003

AbstractHigh molecular weight poly(ethylene oxalate) with fiber‐forming properties was obtained from oxalic acid and ethylene glycol. The process was carried out on two stages in the melt. A new method was used for aliphatic oligoester synthesis in the melt, because the decomposition of oxalic acid takes place in the presence of glycol. The process was carried out at low temperatures with azeotropic water removal. Investigations of the polycondensation of oxalic acid and ethylene glycol with a compound forming a heteroazeotrope with water showed that the process is subject to the general laws of the polycondensation in melt: it depends on the ratio of initial components, presence of accelerating compounds, etc. However, the reaction time of polycondensation was dependent on the stirring intensity. High molecular weight poly(ethylene oxalate) was obtained by oligomer polycondensation in the melt. Thorium carbonate and tin dichloride were used as catalysts.
High‐conversion polymerization. II. Influence of chain transfer on the gel effect
Authors: Cardenas J. N. , O'Driscoll K. F. 
Published: April 2003

AbstractKinetic equations are presented which describe the course of a free‐radical polymerization carried to high conversion when chain transfer to monomer or to other low molecular weight agents is important. Calculations are presented which show that the influence of chain transfer to monomer can greatly affect the rate of polymerization and the molecular weight averages when a polymerization is subject to autoacceleration because of the gel effect.
Regular copolyamides. IV. Characterization of membrane morphology
Authors: Tirrell D. , Vogl O. 
Published: April 2003

AbstractAsymmetric copolyoxamide films prepared via a solution‐casting/gelation process have been characterized by scanning electron microscopy, small‐angle light scattering, and measurements of surface area and hydrophilicity. The polymer selected for study is a regular copolyamide prepared from N,N‐bis(2‐aminoethyl) oxamide and isophthaloyl chloride, and shows promise as a membrane material for desalination by reverse osmosis. Scanning electron microscopy reveals a unique capillary structure in films cast from N,N‐dimethylacetamide‐LiCl mixtures, plus a variety of structures in trifluoroacetic acid‐cast membranes. Light‐scattering experiments on water‐swollen films have substantiated microscopic observations of desiccated samples; the gel structures of the copolyoxamide films do not appear to suffer severe collapse on dehydration. Measurements of surface area and water sorption have been conducted in an attempt to assess membrane‐water interaction.
The growth of polymer colloids
Authors: Lichti Gottfried , Gilbert Robert G. , Napper Donald H. 
Published: April 2003

AbstractThe traditional theoretical approach to emulsion polymerization is extended to include effects due to the size of each polymer latex particle. Specific account can thus be taken of the particle size distribution in considering the growth of the colloid. Coupled partial differential equations are derived to describe the system and shown to reduce to the conventional Smith‐Ewart equations under certain limits. Solutions are presented for simple models for the emulsion polymerization of styrene and vinyl acetate.
Permeability to oxygen of poly(methyl methacrylate) films containing silane‐treated glass flakes
Authors: Higashide F. , Omata K. , Nozawa Y. , Yoshioka H. 
Published: April 2003

AbstractPermeability to oxygen of poly(methyl methacrylate) (PMMA) films containing glass flakes (GF) was investigated. The glass flakes were treated with five kinds of silanes and K2Cr2O7‐H2SO4 solution to improve the affinity with PMMA. The permeability curves were classified into five representative types, which depend on the pretreatment of the glass flakes and the type of silane used as a coupling agent. The factors which influence permeability were studied from the point of view of permeative retardation with the aid of several methods, such as determination of the apparent density of the glass flakes treated with the silanes, the shearing and tensile strength of the PMMA films containing the glass flakes, ESR spectra of films irradiated by γ‐rays, and x‐ray diffraction patterns of the films. It was found that the three very effective methods to retard the permeability are (a) pretreatment of the glass flakes with NaOH, (b) treatment with γ‐methacryloxypropyltrimethoxysilane or ditrimethylsiloxymethylsilane, and (c) heat pressing of the films. The lowest permeability constant which was attained in this study was about one‐eighth that with PMMA alone.
Substrate–polymer interactions in liquid exclusion chromatography (GPC) in N,N‐dimethylformamide
Authors: Dubin Paul L. , Koontz Steven , Wright Kenneth L. 
Published: April 2003

AbstractThe importance of nonexclusion effects in the GPC behavior of several stationary phases was investigated with DMF, 0.01M LiBr, as the mobile phase. Various low MW solutes and narrow MWD polymers, encompassing a wide range of polarities, were studied. The elution of the polymers was examined in terms of “universal calibration” behavior. Styragel and silanized glass both exhibit affinity for apolar polymers in DMF; for the former substrate this effect shows a strong inverse dependence on MW. As a consequence, application of polystyrene calibration curves to GPC analysis of more polar polymers with these substrates leads to overestimations of MW parameters. These errors are not corrected when universal calibration procedures are used. Ideal exclusion chromatography is exhibited by a number of polymers on untreated porous glass substrates. However, polymers with strong hydrogen‐bonding functionality appear to be susceptible to marked adsorption in this system.
High‐conversion polymerization. III. Kinetic behavior of ethyl methacrylate
Authors: Cardenas J. N. , O'Driscoll K. F. 
Published: April 2003

AbstractThe kinetics of free‐radical polymerization of ethyl methacrylate (EMA) have been experimentally studied in bulk and in 50% solution in DMF over the temperature range from 60 to 90°C. At low conversion, the kinetic parameters have been determined, including constants for chain transfer to monomer and solvent. These parameters have then been used to model the kinetic behavior at high conversion using previously derived equations. The results indicate that the equations satisfactorily predict the conversion and molecular weight averages and distributions as a function of time from zero to ca. 95% conversion.