bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative explanation for a saturation phenomenon exhibited by poly‐4(5)‐vinylimidazole and an anionic ester
Authors: Okamoto Y. , Overberger C. G.
Published: April 2003

The hydrolysis of a negatively charged ester, sodium 3‐nitro‐4‐acetoxybenzenesulfonate (NABS), catalyzed by poly‐4(5)‐vinylimidazole (PVIm) was reinvestigated under the conditions in which the substrate concentration was in excess of the catalyst concentration. The reaction was carried out under the same reaction conditions as previous work (28.5 vol‐% ethanol–water, pH 7.1, μ = 0.02, 26°C). Careful studies on the initial rate with a stopped‐flow spectrophotometer revealed that the initial rate at high NABS concentration did not level off (saturate) as much as expected from the previous results. This difference was ascribed to two factors. One was that in the previous study, we treated up to 5% hydrolysis, but in the present work up to 1% in order to determine the initial rate. The other was the relatively slow deacylation reaction of the intermediate, partially acetylated PVIm, which resulted in less efficiency of the catalysis. The slow deacylation was confirmed by the kinetics of the hydrolysis of NABS and also independently by measuring the deacylation rate of the acetylated (or acylated) PVIm. The deacylation was an intramolecular catalysis and the rate constant was about 0.1 min—1 in 28.5 vol‐% ethanol–water at pH 7.1 at 26°C. The whole process of the hydrolysis could be explained by a two‐step pathway: an initial burst acylation followed by the slow deacylation. The electrostatic interaction between the cationically charged imidazole groups and NABS seemed not strong enough to form a stable complex. Thus, potassium p‐toluenesulfonate showed no effect as a competing agent (inhibitor) against NABS.
Interaction of poly(styrene sulfonate) with polycations carrying charges in the chain backbone
Authors: Tsuchida Eishun , Osada Yoshihito , Sanada Kei
Published: April 2003

The interaction between sodium poly(styrene sulfonate) (NaSS) and side‐chain charged polycation polymer (pendent type) or main‐chain charged polycation polymer (integral type) has been studied. It was found that the polyion complex (the reaction product of these polyelectrolytes) of pendent–pendent type has an equimolar composition at any mixing ratio of two component polymers. However, a polyion complex of integral–pendent type can form a water‐soluble complex with a ratio of [polycation]/[polyanion] = 1/3, in addition to a complex with a equimolar composition. The mechanism of formation of this specific complex is discussed.
Polyampholyte synthesis by cyclopolymerization
Authors: Panzik Harold L. , Mulvaney J. E.
Published: April 2003

The syntheses of N‐2‐phenylallylacrylamide (I) and N‐ethyl‐2‐phenallylacrylamide (II) are described. Both monomers can be polymerized with radical initiators to form cyclopolymers although complete cyclization does not occur. Lewis acids (ZnCl2 in the case of I, Et1.5AlCl1.5 in the case of II) result in the formation of higher molecular weight polymers in a shorter period of time. Polymers of I and II have been hydrolyzed to polyampholytes. The copolymerization of α‐methylstyrene–acrylamide in the presence of azobisisobutyronitrile (AIBN) and ZnCl2 leads to the formation of a 1:1 copolymer, whereas styrene–acrylamide under the same conditions give a copolymer slightly dependent upon the monomer feed composition. Attempted cyclopolymerization of N‐allylacrylamide (monomer I without the phenyl group) with ZnCl2–AlBN was not successful, only crosslinked polymer being obtained. An explanation is offered for the fact that I does not form a perfect cyclopolymer, although the α‐methylstyrene–acrylamide system forms a 1:1 copolymer.
Thermal degradation of a polyphenylimide‐quinoxaline in air and under vacuum
Authors: Augl Joseph M.
Published: April 2003

Three samples of poly{2,2′‐[N,N′‐bis(1,4‐phenylene)benzophenone‐3,3′,4,4′‐tetracarboxylimide‐6,6′‐bis(3‐phenyl‐quinoxaline)]} (PPIQ), were prepared, differing in molecular weights and polymer chain endings. Their thermal degradation in vacuo and in air was determined by isothermal weight loss measurements. As in the case of poly‐[2,2′‐(1,4‐phenylene)‐6,6′‐bis(3‐phenylquinoxaline)] (PPQ), the temperature coefficients of thermal degradation in air were independent of molecular weight. However, in contrast, the temperature coefficients were independent of the type of polymer endgroups. It is, therefore, concluded that, contrary to amino‐terminated PPQ's, polymer chain‐end unzipping of PPIQ is of minor importance during thermal‐oxidative degradation.
Application of dn/dc data for the determination of partial specific volumes of dissolved macromolecules. II. Partial specific volume of ovalbumin in aqueous solution
Authors: Heller Wilfried , Schwartz Ellen Shirley E.
Published: April 2003

The theory of an interferometric method for determining partial specific volumes of macromolecules is briefly reviewed. The experimental technique developed in this laboratory is described. Detailed results are given on the partial specific volume of ovalbumin in aqueous solution and its dependence on pH and KCl concentration. The results are compared, as far as possible, with dilatometric results obtained in another laboratory. The contribution of a change in partial specific volume of the macromolecules and in the partial specific volume of the water associated with them to the results is analyzed, and the scope of a possible complication due to changes in molecular polarizability is pointed out.
Delayed yielding in glassy polymers
Authors: Matz David J. , Guldemond William G. , Cooper Stuart L.
Published: April 2003

A theoretical description of the ductile transition of glassy polymers in tensile creep is given. It predicts the delay time for plastic yield as a function of stress. The model assumes first‐order rate expressions for the rate of change of loadbearing elements. The rate constants are given by a modification of the absolute reaction rate concepts of Eyring, where the energy barrier for breakdown of the bonding elements is asymmetric. This leads to an equation for the yield delay time as a function of the height of the energy barrier in the unstressed state, an activation volume, and a critical stress required to overcome the initial barrier asymmetry. The model has been compared to creep delay time experiments on polysulfone, polycarbonate, and poly(methyl methacrylate). It is able to predict the stress dependence for the onset of ductility in these materials with greater accuracy than previously reported equations.
Stress—strain behavior of a polyurethane rubber in combined torsion and tension or compression
Authors: Mancke Ralph G. , Landel Robert F.
Published: April 2003

The biaxial response, in combined torsion and tension or compression, of a highly crosslinked polyurethane elastomer has been measured at room temperature under equilibrium conditions with the Becker‐Landel torsion‐tension tester. Cylindrical specimens of four different aspect ratios were studied. Axial strains ranged from −33% to + 17%, and twists from 0 to 0.83 radians/cm. End effects were avoided by measuring both strains in the gage length at the center of the specimen. A small error in the twist parameter, probably arising from slight misalignment of the instrument, was unresolved. Within this error the normal forces and moments of all the specimens conformed to the neohookean (Mooney‐Rivlin with C2 = 0) stored energy function for incompressible materials, and the moduli measured in extension and compression were equal.
Etching of crystalline poly(ethylene terephthalate) by hydrolysis
Authors: Miyagi Arata , Wunderlich Bernhard
Published: April 2003

Conditions have been found for the etching of poly(ethylene terephthalate) with water so that the crystalline portions alone remain. Initial sample and hydrolysis products are analyzed by extraction of low molecular weight products; density, viscosity molecular weight, and endgroup determination; heating‐rate‐dependent thermal analysis; low‐angle and wide‐angle x‐ray analysis; and electron microscopy. On hydrolysis of a 67% crystalline polymer at 180°C for about 300 min, almost fully crystalline extended‐chain oligomers can be obtained with about 65% yield. The morphology of melt‐crystallized poly(ethylene terephthalate) and the melting behavior of oligomer lamellae are discussed.
Investigation of molecular orientation distributions by polarized raman scattering and polarized fluorescence
Authors: Bower D. I.
Published: April 2003

It is assumed that the intensity of the vibrational Raman scattering from each of the structural units (molecular segments or crystallites) in an oriented polymer solid is determined by a symmetric second‐rank tensor. The distribution of orientations of the principle axes of the tensors is expanded in a series of generalized spherical harmonics, Zlmn(θ)e−imψe−inϕ, and it is shown that relations among the coefficients in this expansion can be obtained from suitable intensity measurements using polarized radiation. If the orientation of the tensor axes within the structural unit is known (in the general case, for several Raman lines), then the coefficients Mlmn of a similar expansion for axes fixed in the units can be obtained for l, m, and n even and l ≤ 4. The limitation to even m follows from the assumption that the solid has at least orthotropic statistical symmetry but the limitations on n and l arise from the nature of the Raman effect. Some simple special cases are considered and some orientation‐independent intensity sums are derived. It is shown that, with the simplifying assumption usually made, the theory of the polarized fluorescence method for determining molecular orientations is a special case of the theory for the Raman method.
Chain‐backbone motion in glassy polycarbonate studied by polarized infrared spectroscopy
Authors: Lunn A. C. , Yannas I. V.
Published: April 2003

Chain‐backbone motion in glassy polycarbonate has been investigated both under isothermal stress, and also under zero stress during isothermal annealing of freely contracting film specimens. In both types of experiment, backbone motion was detected by measuring the change in infrared dichroism. The dichroism of absorption bands at 1364 and 2971 cm−1, which have transition moment vectors directly related to the chain‐backbone orientation, was studied. Under tensile stress in the homogeneous region of deformation, changes of up to 2.2° in the mean chain‐backbone orientation angle were measured at 23°C. With the onset of cold drawing a total orientation change of some 8° was observed. For the isothermal annealing experiments, a film specimen holder employing conductive heating with radiative losses was employed. It enables infrared measurements to be made while the temperature of the contracting specimen is maintained constant to ± 0.5°C. Oriented specimens were prepared by isothermal stretching of polycarbonate films to strains of the order of 100%. Changes in the mean chain‐backbone orientation angle were observed during annealing of these oriented films at temperatures between 80°C and the glass transition (149°C). Chain motion proceeded during annealing, and chain segments were observed to move cooperatively. The temperature at which the polymer is prestretched has a pronounced effect on its subsequent relaxation during annealing: when the sample was stretched at 23°C. motions were detected during annealing at temperatures as low as 81°C, while, if it was stretched at 154°C, no motion was detected at annealing temperatures below 127°C. The data are discussed in comparison with theories of the glassy state that predict the absence of chain‐backbone motion at temperatures significantly below the glass transition. A shift in frequency of the νa (CH3) absorption peak in stretched polycarbonate was measured by using polarized radiation. The effect was interpreted in terms of changes in the intermolecular bonding structure of the oriented polymer.
Photoelectric effects in poly(ethylene terephthalate) and polyethylene
Authors: Comins J. D. , Wintle H. J.
Published: April 2003

Photocurrents induced by ultraviolet illumination of poly(ethylene terephthalate) (Mylar) and polyethylene specimens supplied with aluminum electrodes in a sandwich configuration have been studied in the wavelength range 380–180 nm. A description is given of the precautions taken to ensure that artefacts such as photoelectric emission external to the specimen do not influence the measurements. In both materials, a fast and a slow transient are present. Measurements on polyethylene show that the magnitude of the response is linearly dependent on the light intensity and is essentially thickness independent. This behavior leads to difficulties in interpretation in terms of known conduction processes. In Mylar it is shown that hole injection from the positive electrode into the polymer is responsible for the observed currents, and evidence to associate a similar process with the effects in polyethylene is presented.
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

A 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

Counterion 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.
On counting theorems for self‐avoiding walks
Authors: Chay Teresa Ree
Published: April 2003

Certain differences are pointed out between two recently published counting theorems for self‐avoiding walks on a lattice.
Plastic deformation of polyethylene crystals on copper and NaCl crystal substrates
Authors: Wu W. , Argon A. S. , Turner A. P. L.
Published: April 2003

Polyethylene 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

The 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

Precipitation 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

A 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

A 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

Separations 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

Equimolar 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

Copolymers 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

An 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

Bifunctional 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

The 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

ESR 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

In 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

Polymerization 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

Poly(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

Thermal 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

5‐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

The 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

The 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

Rate 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.
13C nuclear magnetic resonance studies on the stereochemical configurations of 2,4‐dimethoxypentane and poly(alkyl vinyl ethers)
Authors: Matsuzaki Kei , Ito Hiroshi , Kawamura Tokiji , Uryu Toshiyuki
Published: April 2003

13C nuclear magnetic resonance (CMR) spectra were obtained for 2,4‐dimethoxypentane, which is a model compound of poly(methyl vinyl ether), and the effects of the solvent and temperature on the chemical shifts were investigated. CMR spectra of poly‐(alkyl vinyl ethers) were also determined and analyzed. The diad tacticities were obtained from β‐methylene carbon resonances of poly(methyl vinyl ether), poly(ethyl vinyl ether), and poly(isobutyl vinyl ether), but not from those of poly(isopropyl vinyl ether) and poly(tert‐butyl vinyl ether). The methoxyl carbon resonance of poly(methyl vinyl ether) and the ethoxyl methylene carbon resonance of poly(ethyl vinyl ether) showed splittings corresponding to pentad and triad sequences, respectively. The α‐methine and quaternary carbon resonances of poly(tert‐butyl vinyl ether) showed splittings corresponding to pentad and triad sequences, respectively.
Stereospecific bulk polymerization of methyl methacrylate initiated by its tactic polymers
Authors: Buter R. , Tan Y. Y. , Challa G.
Published: April 2003

Methyl methacrylate (MMA) was polymerized by radical initiation at 90°C by its own preformed tactic polymers, i.e., conventional (c‐PMMA), isotactic (i‐PMMA), and syndiotactic (s‐PMMA) PMMA, and also by a preformed 1:1 stereocomplex of i‐PMMA and s‐PMMA. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR spectra and viscometry. Higher polymerization rates were obtained in the presence of stereo‐regular PMMA than in the presence of c‐PMMA. Moreover, it appeared that i‐PMMA promoted the formation of s‐PMMA, and conversely s‐PMMA the formation of i‐PMMA, especially in the initial stages of the reaction. A higher M̄v of the preformed polymer yielded a higher rate and a higher stereospecificity of the polymerization. No polymerization took place in the absence of performed PMMA. The results support a replica mechanism proposed by Szwarc, in which polymerization is preceded by a specific arrangement of monomeric units along the polymeric chain into a distinctive pattern. Such arrangement coupled with a strong tendency of the isotactic and syndiotactic species to associate may lead to the present stereospecific replica polymerization. This association is demonstrated by rapid gelation during polymerization and by lowering of reduced viscosity in very dilute mixtures of i‐PMMA and s‐PMMA in MMA.
Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). II. Syndiotactic PMMA as matrix
Authors: Buter R. , Tan Y. Y. , Challa G.
Published: April 2003

Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed syndiotactic PMMA (sMA) with about 90% syndiotactic triads and of different M̄v, viz., sMA‐1, 1.6 × 105; sMA‐2, 3.0 × 105; and sMA‐3, 8.7 × 105. The MMA:sMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. In all cases isotactic PMMA (i‐PMMA) was produced, especially in the initial reaction stages, which associated with the syndiotactic substrate to form acetone‐insoluble 1:2 i/s‐stereocomplexes. The isotacticity decreased with conversion and was highest in the presence of sMA‐3. Characterization of the acetone‐soluble fractions indicated that i,s‐stereoblock polymers were also produced. From these results it is concluded that this reaction can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i‐PMMA and s‐PMMA to associate. With sMA of M̄v below about 1.2 × 105, no i‐PMMA is formed; in other words, no replica polymerization occurs. For polymerizations in the presence of sMA‐2, the critical M̄v of propagating chains, with has to be exceeded before stereoassociation is strong enough to effectuate replica polymerization, has been estimated to be 0.6 × 105.
Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). III. Influence of temperature
Authors: Buter R. , Tan Y. Y. , Challa G.
Published: April 2003

Methyl methacrylate (MMA) was polymerized by radical initiation at 0, 25, 50, 75 and 100°C in DMF in the presence of preformed isotactic PMMA (iMA) or preformed syndiotactic PMMA (sMA) with different M̄v and also without preformed PMMA (“blank” polymerizations). From the tacticities of the formed polymers it is concluded that blank polymerization does not conform to simple Bernoulli statistics, but follows at least first‐order Markov statistics. The formation of long syndiotactic sequences in the presence of iMA and long isotactic sequences in the presence of sMA denotes still higher‐order Markov statistics. The stereoregulating action is improved by higher M̄v of the preformed polymer (matrix) and lower reaction temperature. These influences can be explained by assuming an equilibrium between polymer growth on the matrix and in the “free” solution. For polymerizations in the presence of iMA or sMA below 300°K, the differences in activation enthalpies (ΔHs/i‡ – ΔHi/s‡) are practically equal to that for the blank polymerization, ca. 900 cal/mole, whereas the differences in activation entropies (ΔSs/i‡ – ΔSi/s‡) differ considerably. (ΔSs/i‡ – ΔSi/s‡) values are highly negative in the presence of iMA and highly positive in the presence of sMA. From these results it is concluded that the isotactic and syndiotactic polymer matrices exert a steric influence on the monomer addition process, thus promoting so‐called stereospecific replica polymerization.
Oxidative coupling as a potential route to polymers of group IV acetylenes
Authors: Parnell D. Ray , Macaione Domenic P.
Published: April 2003

Bis tert‐butyl‐, trimethylsilyl‐ and trimethylgermyl‐diacetylenes were prepared from the corresponding ethynyl Group IV compounds via oxidative coupling. Bis(trimethylstannyl)diacetylene could not be prepared by oxidative coupling, but was prepared via another technique. Coupling of diethynyldimethylsilane did not lead to the expected polymer, as cleavage of the silicon–ethynyl bond occurred. However, coupling of 1,3‐bis(dimethylethynyl)disiloxane did lead to polymer containing alternating diacetylene and disiloxane units.
Effect of ultrasound on free‐radical polymerization in a continuous stirred tank reactor
Authors: O'Driscoll K. F. , Sridharan A. U.
Published: April 2003

Methyl methacrylate has been continuously polymerized in toluene solution with AIBN as an initiator at 60°C in a jacketed steel vessel of 890 ml volume with holding times of several hours. Provision was made for good mixing and introduction of a steady stream of monomer, solvent, and initiator. The effluent stream was analyzed for polymer content and molecular weight distribution by gel‐permeation chromatography. After the reactor had been operating for three holding times, an ultrasonic probe in the reactor was turned on, and the effect of the ultrasound on the steady‐state operation of the reactor was observed. The ultrasound caused a rapid increase in the conversion level. A small, concomitant increase in the degree of polymerization was also noted. It is proposed that the ultrasound breaks polymer chains, giving polymeric free radicals which increase in size while increasing the rate of polymerization. Simulation of the polymerization in the stirred tank reactor has been achieved by using a digital computer, and a quantitative treatment of the effect of ultrasound has been developed.
Free‐radical polymerization of methyl methacrylate in presence of the Cr(C5H7O2)3–Al(i‐C4H9)3 catalyst system
Authors: Deshpande A. B. , Kale S. M. , Kapur S. L.
Published: April 2003

Polymerization of methyl methacrylate has been studied with the chromium acetylacetonate–triisobutyl aluminum catalyst system in benzene medium at 40°C. These studies have been carried out at an Al/Cr ratio of 12 to compare the behavior with the previously studied chromium acetyl acetonate–triethyl aluminum catalyst system. The enhanced yield and gelling of polymer suggests a free‐radical mechanism of polymerization. Further, the kinetics of polymerization and the heterotactic structure of polymer as determined by NMR examination have led to confirmation of the freeradical mechanism of polymerization of methyl methacrylate by an excess of triisobutylaluminum in the presence of catalyst complex.
Thermally stable sulfone‐containing poly(amide‐imides)
Authors: Adduci J. M. , Sikka S. K. , Miqueles L. E. , Ramirez R. S.
Published: April 2003

Novel sulfone containing poly(amide‐imides) have been prepared by reacting 3,4‐dicarboxy‐4′‐(chloroformyl)‐diphenylsulfone dianhydride with various aromatic diamines. Relatively high molecular weight polymers were obtained by using a two‐step procedure. Transparent poly(amide‐imide) films, varying in color from dark yellow to colorless, were formed by thermally treating polyamic acid solutions. All films showed good thermal stability.
High‐resolution small‐angle x‐ray investigations on poly‐o‐bromostyrene in benzene solutions
Authors: Durchschlag H. , Kratky O. , Olaj O. F. , Breitenbach J. W.
Published: April 2003

Small‐angle x‐ray investigations on poly‐o‐bromostyrene in benzene solution at extremely high resolution (corresponding to a Bragg's value of 3200 Å) proved to be able to link together the ranges covered by small‐angle x‐ray scattering and light scattering. On the other hand, there are problems encountered in molecular weight determination of chain molecules, since both methods at extremely small angles and at finite concentrations reach the limits of particle scattering. The differing results obtained by means of the two methods for the molecular weight of a rather high molecular weight sample of poly‐o‐bromostyrene are ascribed to entangelements stabilized by dipole–dipole interactions. These, due to the differing Bragg's angles and concentration ranges in the two methods, affect the experimental results to a different degree.
Semiconducting polymers based on charge‐transfer complexes. I. Synthesis of electron‐donor‐containing poly‐N‐acylethylnimines
Authors: Litt Morton H. , Summers James W.
Published: April 2003

Polymers were made which contained 10‐methyl, 3‐phenothiazinyl, and 4‐(methylthio)phenoxy electron‐donating groups on side chains. N‐Acyl‐substituted poly‐ethylenimines were chosen because the repeat distance along the polymer chain is the same as the repeat distance in most aromatic charge‐transfer complexes (about 6.4 Å) and the side chains do not interfere with each other. This paper describes synthetic routes for preparation of these electron‐donor‐containing polymers. Synthesis of a polyacrylate donor is also described.