bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotational diffusion of 9,10‐diphenylanthracene in di‐n‐butyl phthalate solutions of polystyrenes by the fluorescence polarization method: Dependence on polymer concentration and molecular weight
Authors: Hostettler John D. , Schrag John L. 
Published: April 2003

AbstractA versatile double‐beam polarization fluorimeter has been constructed for measuring the polarization of fluorescence from polymer solutions, melts, and glasses. Polarizations can be determined over a range of temperatures from −20 to +80°C in a controlled atmosphere with a precision of ±0.001 to ±0.005 for the studies reported herein. Data collected at different temperatures for 1.5 × 10−5M solutions of 9,10‐diphenylanthracene (PA) in di‐n‐butyl phthalate (BP) fit a relation of the Perrin type, 1/P = (1/P0) + (ST/η1), where P is the polarization, T is the absolute temperature, and η1 is the solvent viscosity. The constants P0 and S were 0.400 ± 0.005 and (7.4 ± 0.3) × 10−3 P/°K, respectively. Polarizations were also determined at 25.0 ± 0.1°C for BP solutions containing 1.5 × 10−5M PA and polystyrenes at various weight fractions w2 and molecular weights M. Rotational friction coefficients ζr deduced from these data showed no dependence on M from 5.1 × 104 to 8.6 × 105 g/mole, and a gradual increase as w2 was varied from 0 to 0.1. It is concluded from these results that PA is an especially attractive emitter for rotational diffusion studies in nonaqueous systems, and that the abrupt changes in ζr with w2 and M observed for some other emitter–polymer systems and attributed to onset of coil overlap are not universal characteristics of such systems.
Interactions of counterions with dextran sulfate in aqueous solutions
Authors: Satake Iwao , Fukuda Masao , Ohta Tomohisa , Nakamura Kōzaburo , Fujita Noboru , Yamauchi Akira , Kimizuka Hideo 
Published: April 2003

AbstractCounterion activity coefficients in solutions of dextran sulfate with and without added salts were determined potentiometrically by using a cation‐exchange membrane and a sodium glass electrode. Dextran sulfate was shown to interact with monovalent cations in the order of preference: K+ > Cs+ > Na+ > Li+, whereas no specificity was found for bivalent cations. On the basis of light‐scattering measurements, the expansion of the dextran sulfate polyion in solutions of alkali metal salts was found to fall in the same order as the counterion activity coefficients in salt‐free solutions. It was also shown that the dextran sulfate polyion assumes a more extended conformation in magnesium chloride solution than in calcium chloride. These results were substantiated by measurements of solution viscosities.
Plastic deformation of polyethylene crystals on copper and NaCl crystal substrates
Authors: Wu W. , Argon A. S. , Turner A. P. L. 
Published: April 2003

AbstractPolyethylene single crystals deformed on copper and NaCl single‐crystal substrates by the method of Gleiter and Argon were examined in transmission electron microscopy attached to carbon film carriers constraining them to their deformed state and also after they have been removed from the deformed substrates and were allowed to relax. It was observed that the imposed shear strains can be accommodated by the polyethylene crystals by a combination of debonding from the substrate, elastic flexing, extensive inplane twinning and martensitic shear transformations, buckling, and tearing. No contrast effects suggestive of slip lines could be observed in dark field studies, and the gold droplet decoration technique failed to detect any unambiguous slip lines. From this it is concluded that the critical shear stress for slip is always higher than that for twinning and martensitic shear transformations, and that crystals will deform preferentially by these latter modes.
Polymerization of N‐vinylcarbazole by chlorides and oxychlorides of some group V elements. II. Kinetics and mechanism of the polymerization initiated by arsenic trichloride
Authors: Biswas Mukul , Chakravarty Devapriya 
Published: April 2003

AbstractThe polymerization of N‐vinylcarbazole (NVC) initiated by AsCl3 in benzene and nitrobenzene solvents was studied at 33°C. Rp is proportional to the first power of the initiator concentration. Rp varies in a first‐order manner with NVC concentration up to a certain optimum concentration of the latter, after which it falls and ultimately levels off. The rate and the molecular weight are depressed by the addition of various amines, preformed poly‐NVC, and water. HCl does not have any cocatalytic effect on the system. Rate and the molecular weight are increased in nitrobenzene. The degree of polymerization stays independent of the initiator and NVC concentration and also of increasing conversion. These results suggest a conventional cationic mechanism, and overrule the possibility of a cation radical initiation. A suitable kinetic scheme has been proposed in conformity with the findings.
Emulsifying effect of graft copolymer for the homopolymer
Authors: Ikada Yoshito , Horii Fumitaka , Sakurada Ichiro 
Published: April 2003

AbstractPrecipitation of poly(methyl methacrylate) (PMMA) from dimethyl sulfoxide solution by addition of water as a precipitant was studied in the presence of a well‐characterized graft copolymer of poly(vinyl alcohol) (PVA). The graft copolymer which had been prepared by a radiation method and freed from PMMA and PVA homopolymers had one PMMA branch whose length was nearly equal to that of the PVA backbone. Even when such an amount of water was added to PMMA solution as to cause all the PMMA to precipitate from the solution, the precipitation was prevented by the presence of relatively small amounts of the graft copolymer. With decreasing molecular weight of PMMA, the effect of protection became more pronounced. When the precipitation was prevented, the solution was transformed into a stable emulsion. The mechanism of protection against precipitation was discussed on the basis of the results obtained and electron microscopic photographs of the emulsion particles. It was concluded that the particles of the precipitated homopolymer were covered by a monolayer of the graft copolymer, resulting in prevention of coagulation.
Telechelic diene prepolymers. VII. Polymerization temperature study of polyisoprenes and polychloroprenes
Authors: Reed Samuel F. 
Published: April 2003

AbstractA study of the free‐radical polymerization of isoprene and chloroprene leading to the preparation of telechelic prepolymers containing hydroxyl and carboxyl terminal groups has been carried out. The polymerization temperature was found to have a pronounced affect on the molecular weight distribution of the polyisoprenes, heterogeneity index values below 1.3 generally being found for prepolymers prepared at 60°C or below and index values higher than 1.3 being found for prepolymers prepared at higher temperatures. This change in heterogeneity index values with polymerization temperature was not observed with the polychloroprenes.
Bridged polyaromatics: Synthesis and isomorphous properties of polymers and oligomers containing O, S, CH2bridges
Authors: Montaudo G. , Bruno G. , Maravigna P. , Finocchiaro P. , Centineo G. 
Published: April 2003

AbstractA study of the isomorphous relationships existing among five crystalline polyaromatic polymers containing O, S, CH2bridges, i.e.,magnified imagewhere Ph is phenyl, is reported. Appropriate series of oligomers corresponding to these polymers have also been prepared in order to investigate how the solid‐state properties of the oligomers correlate with those of the polymers. A preliminary x‐ray analysis is reported showing that the polymers are actually isostructural.
Estimation of carboxy‐terminated polybutadiene functionality distribution via fractionation on silica gel
Authors: Law Ronald D. 
Published: April 2003

AbstractSeparations of carboxyl‐terminated polybutadiene (CTPB) liquid polymer according to functionality have been effected by using stepwise elution from silica gel. Recoveries in the 90–95% range have been achieved by deactivating the silica gel and recycling the unfractionated portion through progressively more active silica gel. Subjection of the fractions obtained from the silica‐gel separation to analysis via gel‐permeation chromatography and infrared spectroscopy yields not only functionality distribution data, but also provides an estimation of the relationship between molecular weight distribution and functional type. Repetitive analyses indicate a precision of ±7% (or less) of the amount of each functionality type present. An evaluation has been made of the accuracy of the data by fractionating saturated and methyl ester derivatives of CTPB under test conditions different from those employed in fractionating the original polymer. Within the known experimental error of the techniques employed, these studies have confirmed the data generated for CTPB polymer as received. Analytical techniques and interpretation of data are discussed.
Donor–acceptor complexes in copolymerization. XLIII. Cyclization of alternating and random styrene–(meth)acrylic ester copolymers
Authors: Gaylord Norman G. , Patnaik Birendra K. , Janovic Zvonimir 
Published: April 2003

AbstractEquimolar alternating copolymers of styrene and methyl methacrylate (prepared with Et1.5AlCl1.5, SnCl4, and ZnCl2) as well as equimolar random copolymer were treated with polyphosphoric acid at 135°C. The extent of cyclization of the alternating copolymers was about 40%, independent of the cotacticity of the copolymer, and there was little or no crosslinking. The random copolymer underwent only 10% cyclization and considerable crosslinking. The extent of cyclization of the alternating copolymer of styrene and methyl acrylate (prepared with Et1.5AlCl1.5) was the same as that of the random copolymer and was lower than that of the corresponding methyl methacrylate copolymer. Both alternating and random copolymers underwent extensive crosslinking.
High‐field NMR of ethylene—sulfur dioxide copolymers
Authors: Ovenall D. W. , Sudol R. S. , Cabat G. A. 
Published: April 2003

AbstractCopolymers of ethylene and sulfur dioxide containing 40–60 wt‐% sulfur dioxide have been analyzed by using 220 MHz high‐resolution NMR, and it has been shown that they contain structures of the form, SO2(CH2CH2)nSO2, where n is 1, 2, 3, 4, … The relative numbers of structures with n = 1, 2, 3, or 4 and above can be calculated from the NMR spectra. The fraction of ethylenes in longer blocks and the sulfur dioxide contents of the polymers can also be determined from the NMR data. The NMR results indicate that the distribution of ethylenes among the different structures is not that expected for a random copolymerization of ethylene and sulfur dioxide but that the arrangement of these structures within the copolymer is random.
Kinetics of donor–acceptor complex polymerization. IV. Limiting yield in the butadiene–acrylonitrile copolymerization
Authors: Rybicky J. , Tanner J. , Funt B. L. 
Published: April 2003

AbstractAn analysis of the kinetic equation proposed for donor–acceptor systems indicated that the polymer yield at a given time should attain limiting value with increase in rate of initiation. It was essential that the equilibria not be shifted by temperature variation, and the change in rate of initiation was achieved by controlled current passage through the solution. A definite plateau in the yield of polymer was obtained. This was shown not to be due to diffusion control of the rate of initiation.
Oxidative carbon–carbon coupling. III. Oxidative polymerization of bifunctional arylcyanoacetic esters
Authors: De Jongh H. A. P. , De Jonge C. R. H. I. , Sinnige H. J. M. , Magré E. P. , Mijs W. J. 
Published: April 2003

AbstractBifunctional arylcyanoacetic esters were oxidatively coupled to high molecular weight, colorless, amorphous polymers, soluble in common organic solvents. Brittle films were obtained by casting or compression molding. Thermal stability of the polymers is poor due to the weak CC bond formed by oxidative coupling. Radical dissociation‐recombination of this bond (evidenced by ESR) results in meso‐dl equilibration, lowering the Tg of the polymers.
Effect of solvents upon the copolymerization of acrylamide and styrene
Authors: Minsk L. M. , Kotlarchik C. , Darlak R. S. 
Published: April 2003

AbstractThe effect of solvents on the copolymerization of acrylamide and styrene has been studied. Copolymerization to low conversions were run in a variety of solvents which would affect the acrylamide monomer in different ways, i.e., by hydrogen bonding, by dipole–dipole interaction only, or by a combination of both. The effect upon the acrylamide was measured by the shift in the infrared spectra of the amide carbonyl and NH groups. Essentially, both hydrogen bridging and dipole–dipole interaction affect acrylamide in the same way, as manifested by a shift in the amide carbonyl and NH towards the longer wavelength. From the standpoint of acrylamide–styrene copolymerization, the greater the shift in the NH absorption, the smaller is the amount of acrylamide that is found in the copolymer. Thus, by the proper choice of solvent, it is possible to obtain copolymers from the same monomer feed ranging in combined acrylamide from very low to very high, and reactivity ratios for acrylamide also ranging from very low to very high. Conversely, for styrene, activity ratios will range from high to low.
ESR study on radical conversions in irradiated low‐density polyethylene
Authors: Tsuji Kozo 
Published: April 2003

AbstractESR studies were carried out on radical conversions by thermal and photochemical mechanisms in low‐density polyethylene irradiated mainly with electron beams at −196°C both in vacuum and in the presence of CO. According to the spectral change, the following radical conversions were elucidated for the samples irradiated in vacuo [eqs. (1) and (1′)] and in the presence of CO [eqs. (2) and (2′)].
magnified image
From the resemblance of the ESR spectrum observed after direct photolysis of polyethylene to that observed after photo‐induced radical conversions of the allylic radicals, it is concluded that an eight‐line ESR spectrum observed immediately after photolysis of polyethylene at −196°C could be attributed more reasonably to the alkyl radicals CH2CHCH3 than to CH2CH2 and CH2CHCH2.
Synthesis and radiation behavior of perfluoroaromatic polysiloxanes
Authors: Giori C. , Zerlaut G. A. 
Published: April 2003

AbstractIn a study aimed at the development of a polymeric material stable to the space radiation environment, the synthesis and properties of two new perfluoroaromatic polysiloxanes have been investigated. Di(pentafluorophenyl)diethoxysilane and pentafluorophenyltriethoxysilane have been prepared via Grignard synthesis from pentafluorobromobenzene and tetraethoxysilane. By hydrolytic polymerization of these intermediates, polydi(pentafluorophenyl)siloxane and polypentafluorophenylsilsesquioxane have been synthesized. The effect of ultraviolet and low‐energy proton (solar wind) irradiation in high vacuum has been determined in a space‐environment‐simulation facility. These polymers possess excellent resistance to low‐energy proton irradiation but are less stable to ultraviolet irradiation. It is suggested that the enhanced polarization of the carbon–silicon bond due to the strong inductive effect of the pentafluorophenyl groups is responsible for the relatively low ultraviolet and thermal stability of the perfluoroaromatic polysiloxanes.
Catalytic action of metallic salts in autoxidation and polymerization. IX. Polymerization of methyl methacrylate with sodium hexanitrocobaltate(III) in mixed solvent of acetone and water
Authors: Osawa Zenjiro , Sorimachi Masami , Kanazawa Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractPolymerization of methyl methacrylate with some cobalt (III) complexes was carried out in various solvents and in mixed solvents of acetone and water or alcohols. Sodium hexanitrocobaltate(III) was found to be an effective initiator in mixed solvent of water and acetone. The kinetic study on the polymerization of methyl methacrylate with Na3[Co(NO2)6] in a water‐acetone mixed solvent gave the following over‐all rate equation: Rp = 8.04 × 104 exp{ −13,500/RT} [I]1/2[M]2 (mol/1.−sec). The effects of various additives on polymerization rate and the copolymerization curve with styrene suggest that polymerization proceeds via a radical mechanism. The dependence of the polymerization rate on the square of monomer concentration and the spectroscopic data were indicative of the formation of a complex between initiator and monomer.
Sulfur‐containing polymers. VIII. Preparation and properties of poly(carbamoyl disulfides)
Authors: Kobayashi Norio , Osawa Akiko , Fujisawa Tamotsu 
Published: April 2003

AbstractPoly(carbamoyl disulfides) have been prepared for the first time by the stepwise condensation of chlorocarbonylsulfenyl chloride with dithiols and diamines. The polymers obtained in high yields had inherent viscosities up to 1.86. The properties of the polymers depended primarily on the kind of diamines used. Some of the polymers gave transparent, tough films from chloroform solution. The polymer films decomposed by ultraviolet irradiation with liberation of carbonyl sulfide. All the polymers gradually became brittle during storage for 6–8 months under diffused light.
Thermal degradation of linear polyurethanes and model biscarbamates
Authors: Matuszak Michael L. , Frisch K. C. 
Published: April 2003

AbstractThermal degradation of model biscarbamates, polyurethanes and poly(urethane‐ureas) has been investigated by pyrolysis at atmospheric pressure. The biscarbamates were prepared from phenyl, benzyl, and cyclohexyl isocyanate and ethylene glycol. The polyurethanes and poly(urethane‐ureas) were prepared from tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4′‐dicyclohexylmethane diisocyanate (H12‐MDI) and poly(oxyethylene glycols) of various molecular weights. Rate constants for thermal degradation were obtained by measuring carbon dioxide evolution. The thermal degradation of all materials showed that the stability increased in the following manner: aromatic < aralkyl < cycloaliphatic. The separation and identification of the products of the thermal degradation gave an insight into the mechanisms involved in the pyrolysis of aromatic, aralkyl, and cycloaliphatic biscarbamates and the influence of temperature on these mechanisms.
Studies in ring‐opening polymerization. III. 5‐methyl‐5‐propyl and 5‐methyl‐5‐isopropyl‐1,3,2‐dioxathiolan‐4‐one 2‐oxide
Authors: Pedley D. G. , Tighe B. J. 
Published: April 2003

Abstract5‐Methyl‐5‐propyl‐1,3,2‐dioxathiolan‐4‐one 2‐oxide (MPAS) and 5‐methyl‐5‐isopropyl‐1,3,2‐dioxathiolan‐4‐one 2‐oxide (MiPAS), which are isomers of the previously studied 5,5‐diethyl‐1,3,2‐dioxathiolan‐4‐one 2‐oxide (DEAS), have been synthesized and their polymerizability compared with that of the last compound. The two unsymmetrically substituted monomers polymerize by a mechanism which is substantially identical to that of their symmetrically substituted counterpart. In dry nonhydroxylic solvents the rate‐determining process is the primary scission of the ring, which takes place with elimination of sulfur dioxide and concurrent ring contraction to form an α‐lactone intermediate. In this reaction, the parent acid, produced by reaction of the monomer with adventitious traces of moisture, acts as the initiating species. The resultant polymers are all hydroxyl/carboxyl‐terminated, but, whereas those derived from the two unsymmetrically substituted monomers are amorphous and readily soluble in a variety of organic solvents, those derived from the diethyl‐substituted ring have been shown to be highly crystalline materials which dissolve in very few solvents. The relative polymerization rates are illustrated by the first‐order rate constants for decomposition in nitrobenzene at 90°C: DEAS, 20.1 × 10−5 sec−1; MiPAS, 11.0 × 10−5 sec−1; MPAS, 9.7 × 10−5 sec−1. The role of the substituents in determining the magnitude of these constants is discussed in terms of both the Thorpe‐Ingold effect and electron donation at C‐5.
Block copolymerization. VII. Kinetic studies on the polymerization of pivalolactone with polystyrene dicarboxylates and polyacrylonitrile dicarboxylates
Authors: Yamashita Yuya , Nakamura Yoichi , Kojima Shiro 
Published: April 2003

AbstractThe rate of anionic polymerization of pivalolactone with polystyrene dicarboxylates decreased with conversion, suggesting deactivation of the propagating chain end by precipitation of the polymer during polymerization. The presence of unreacted initiator was explained by slow initiation for formation of a living polymer of pivalolactone. Various factors affecting block efficiency were discussed, and high efficiency was obtained for the preparation of block copolymers containing a long pivalolactone segment by using more nucleophilic polystyrene dicarboxylates. Block copolymer of acrylonitrile and pivalolactone was prepared from polyacrylonitrile dicarboxylates.
Photolysis of cellulose and related compounds by 253.7 nm light. I. Rates of gas production from hydrocellulose
Authors: Bos A. , Buchanan A. S. 
Published: April 2003

AbstractThe initial stages of the photolysis of cellulose under vacuum can be followed by the gas production. A photolysis cell is described which allows a rigorous temperature control and gives a reproducible photolysis surface of the solid carbohydrate sample. A mass spectrometer was used to analyze the gases. To measure accurately the small amounts produced in a small volume requires careful calibration of this instrument, together with a fixed routine for the experimental procedure. Using this apparatus, we have photolyzed hydrocellulose under vacuum with 253.7 nm light. Only H2, CO, and CO2 were evolved, the rate of H2 production increasing to a constant value, that of CO increasing more slowly without becoming constant, and that of CO2 decreasing rapidly to a constant value. No induction periods were observed. The gas evolution was not caused by residual O2 or CO2 adsorbed on the polymer, but the rates were altered by leaving the photolyzed sample under vacuum overnight or heating the unphotolyzed sample under vacuum at 100°C. The rates of gas production increased markedly when the light filter was changed to allow a combined photolysis by 253.7 and 184.9 nm light. The results illustrate that stringent precautions must be taken to filter off the latter line in polymer photolyses with Hg arc light if the results are to be meaningfully interpreted in terms of 253.7 nm light photolysis. On photolyzing hydrocellulose previously boiled in NaOH solution, a larger H2 production rate and a smaller CO2 rate (compared with untreated hydrocellulose) were observed. It is suggested that this standard alkali treatment is the reason for the differences between our results and the results of the photolysis of cellulose reported in the literature.
Kinetics of Ziegler propylene polymerization
Authors: Buls V. W. , Higgins T. L. 
Published: April 2003

AbstractRate studies were done on the polymerization of propylene with the TiCl3–diethyl aluminum chloride catalyst system. The polymerization is initially first‐order with respect to propylene concentration. There is a rapid rate decline in the initial period, during which time the reaction becomes functionally second‐order. A physical explanation for this behavior has been adapted from the Avrami equation for crystal growth kinetics. A yield equation was developed which fits experimental data closely. Rate correlations show that the initial rate is exponentially related to the TiCl3/alkyl ratio. Water and other active hydrogen compounds reduce rate; hydrogen increases rate. A “bimetallic” mechanism is proposed which views catalyst activation as consisting of three equilibria, followed by a propagation step where an alkyl group is transferred to the growing chain, and a realkylation of the hydride that remains after the propagation step.