bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal and molecular structure of optically active poly‐D(–)‐β‐methyl‐ε‐caproamide
Authors: Coiro V. M. , De Santis P. , Mazzarella L. , Picozzi L. 
Published: April 2003

AbstractThe investigation of the crystal and molecular structure of optically active poly‐D(–)‐β‐methyl‐ε‐caproamide was carried out in two stages. The molecular conformation was first studied by means of Fourier transform methods and the crystal packing was later deduced by detailed structure factor calculations. The structure thus established bears some close resemblance to that characteristic of the γ modification of unsubstituted nylon 6. A marked shortening of the chain along its axis is produced by the presence of a methyl group in the β position. This causes the rotation about the skeleton bonds adjacent to the amide bonds, whereas the rest of the chain retains its trans planar stable conformation. The hydrogen bonds of normal length (2.85 A.) crosslink the molecules in parallel sheets in planes parallel to the (100) plane which are translated with respect to each other by 5/14 of the b axis in the P monoclinic space group.
Polymers of fluorocarbon ethers and sulfides. I. Trifluoromethyl trifluorovinyl ether and sulfide
Authors: Durrell William S. , Stump Eugene C. , Westmoreland Geraldine , Padgett Calvind D. 
Published: April 2003

AbstractTrifluoromethyl trifluorovinyl ether (I) and sulfide (II) were prepared by dehalogenation of the corresponding 1,2‐dichlorotrifluoroethyl compounds. These were prepared from the reactions of trifluoromethyl hypofluorite with 1,2‐dichlorodifluoroethylene and trifluoromethane sulfenyl chloride with chlorotrifluoroethylene, respectively. The polymerization behavior of these, along with the known trifluoroethyl trifluorovinyl ether (III) was examined. Only III gave a high molecular weight homopolymer, and, along with I, copolymers. II was quite unreactive in all polymerization reactions. High molecular weight copolymers of I and III were obtained with tetrafluoroethylene, vinylidene fluoride, vinylene fluoride, ethylene, and chlorotrifluoroethylene. Those with vinylidene fluoride and ethylene were elastomers in both cases as was the copolymer of III with tetrafluoroethylene, I and II were reacted with CF3NO slowly to give low polymers and volatile products, the corresponding 1,3‐disubstituted oxazetidines. III was reacted with nitrosyl chloride to give a nitroso compound.
Relaxation phenomena of polyoxymethylene obtained from solid‐state polymerization
Authors: Yamada Nobuo , Orito Zenich , Minami Shunsuke 
Published: April 2003

AbstractA highly oriented crystal of polyoxymethylene was prepared by solid‐state polymerization of trioxane single crystals. The relaxation phenomena of this sample were investigated by the dynamic viscoelastic and nuclear magnetic resonance methods from −180°C. to the melting point and were compared with those of single crystals obtained from a dilute solution in cyclohexanol and a bulk‐crystallized sample. The β absorption at about −70°C. completely disappeared, and a new absorption peak with a low intensity appeared at about −100°C. at a frequency of 138 cycles/sec. The crystalline absorption at about 150°C. also remarkably decreased in intensity. This viscoelastic behavior was confirmed by the results of a broad line NMR measurement.
Polymerization of aromatic nuclei. VIII. Molecular weight control in benzene polymerization
Authors: Kovacic Peter , Hsu Li‐Chen 
Published: April 2003

AbstractThe molecular weight of p‐polyphenyl prepared from benzene—aluminum chloride—cupric chloride, was affected by solvent, concentration, and temperature. Relative molecular weights were measured by polymer solubility in chloroform, and positions of the infrared para band and ultraviolet reflectance λmax. The order of effectiveness of the solvents in reducing molecular weight was: o‐C6H4Cl2 > 1,2,4‐C6H3Cl3 > SnCl4 ∼ CS2 > [C6H6]. Degradative oxidation revealed that o‐dichlorobenzene solvent was incorporated as an endgroup to only a minor extent. In general, the molecular weight of p‐polyphenyl decreased with increasing temperature and with decreasing concentration. The theoretical aspects are treated.
Kinetics of styrene homogeneous polymerization to atactic polypropylene
Authors: Wallace R. A. , Hadley K. L. 
Published: April 2003

AbstractThe rate of polymerization of styrene initiated by hydroperoxidized atactic polypropylene in a homogeneous toluene solution has been measured at 60 and 70°C. The reaction is first‐order with respect to styrene concentration and independent of the polymeric hydroperoxide concentration above 2 × 10−5N hydroperoxide. The individual rate constants, length and frequency of the grafted polystyrene chains along the polypropylene backbone have been calculated and their significance discussed. The initiation rate constant compares closely with values reported for the analogous tert‐butyl hydroperoxide‐initiated polymerization. The rate constant for the chain transfer termination elementary step at 70°C., however, is 18 times the value reported for the tert‐butyl hydroperoxide‐initiated polymerization of styrene. This high constant accounts for the relatively low rates of polymerization observed and high termination rates. Chain deactivation is presumably accelerated by increased collisions between growing styrene chains and inactive propylene hydroperoxide and polystyrene molecules. Distribution of polystyrene grafts on polypropylene is estimated from knowledge of effects of styrene concentration, polymeric hydroperoxide concentration, and temperature upon the rate of polymerization.
Polymers and telomers of perfluoro‐1,4‐pentadiene
Authors: Fearn James E. , Brown Daniel W. , Wall Leo A. 
Published: April 2003

AbstractPerfluoro‐1,4‐pentadiene was prepared by pyrolysis of sodium 3,5,6‐trichloroperfluorohexanoate and subsequent dehalogenation. The monomer was polymerized under a number of conditions of temperature and pressure using various periods and various dose rates of γ‐ray initiation. The compound was found to undergo doublebond migration producing perfluoro‐1,3‐pentadiene. The polymer samples, some of them rubbery, others grainy, are assumed to be copolymers of the 1,4‐pentadiene and the 1,3 pentadiene, the 1,4‐diene polymerizing according to a cyclic mechanism and the 1,3‐diene undergoing the 1,4‐addition that is characteristic of butadienes under certain conditions. Infrared and nuclear magnetic resonance studies tend to support these assumptions. Under polymerization conditions the monomer also produced four distinct dimers and traces of two monomeric substances.
Relationship between the ionic nature of some organoaluminum—transition metal catalysts and the rate of polymerization
Authors: Bushick R. D. , Stearns R. S. 
Published: April 2003

AbstractThe electrical conductivity of several trialkylaluminum and alkyl‐aluminum halides was investigated in dry benzene at 25°C. within the concentration range of 10−1–10−3M. The equivalent conductance of the trialkylaluminum systems decreased in the following order: Al(n‐C6H13)3 > Al(n‐C10H19)3 > Al(n‐C4H9)3 > Al(i‐C4H9)3 > Al(n‐C3H7)3 > Al(C2H5)3. The conductance (1/R) of a given series was also examined and found to decrease as each alkyl group was successively replaced by a chlorine atom, thus: Al(C2H5)3 > Al(C2H5)2Cl > Al(C2H5)1.5Cl1.5 > Al(C2H5)Cl2 and Al(i‐C4H9)3 > Al(i‐C4H9)2Cl > Al(i‐C4H9)Cl2. The ion pair dissociation constants K were calculated and show in a qualitative manner the difference between various organoaluminum systems. The relative rate of olefin polymerization was related to the conductivity of various organoaluminum–transition metal catalyst systems used. The effect of Lewis bases such as monoglyme, diglyme, triglyme, and tetraglyme on triethylaluminum indicated that the first‐mentioned base forms a 1:1 type of complex as ordinary ethers do, whereas the remaining three bases utilize only two of their available oxygen atoms to coordinate with triethylaluminum. The effect of TiCl3 (in the presence of an ether) on the conductance was also determined.
Investigation by infrared absorption of the by‐products of the cyanoethylation of cotton cellulose
Authors: Chatterjee Pronoy K. , Conrad Carl M. 
Published: April 2003

AbstractThe soluble cyanoethyl ether of cellulose, prepared by reaction in the presence of NaOH catalyst to high degrees of substitution (DS = 2.95), can be precipitated by various organic media and contains more nitrogen than can be accounted for by simple addition of acrylonitrile at each cellulose hydroxyl group. Infrared absorption spectra of such samples and of the reacted residues show various types of vibrational absorption bands, characteristic of amino groups. At advanced stages of the reaction the characteristic broad unresolved band of cellulose extending from 1200–950 cm.−1 largely disappears, leaving only a few weaker bands which likely overlap those due to C–N stretching. Comparison is made of the spectra of the partially cyanoethylated cellulose and the polyacrylonitrile which forms in the stock acrylonitrile, to characterize the products. It is inferred that the highly cyanoethylated cellulose, partly dissolved in the acrylonitrile, further degrades and changes under a complex mechanism to various forms of amines. The yellow to orange color of the samples is assumed to be due to these by‐products. The thermogravimetric analysis reveals that these products are more heat‐resistant than the cyanoethylated cellulose.
Short‐chain branching in γ‐radiation‐induced polymerization of ethylene
Authors: Machi Sueo , Tamura Takashi , Hagiwara Miyuki , Gotoda Masao , Kagiya Tsutomu 
Published: April 2003

AbstractIn an attempt to elucidate the mechanism of chain‐branch formation in the polymerization of ethylene, the effect of reaction conditions on short‐chain branching in γ‐radiationinduced polymerization of ethylene was investigated by using infrared spectroscopy. The concentration of methyl groups, i.e., the frequency of short‐chain branching, increases with temperature and pressure and is independent of ethylene conversion to polymer and radiation intensity. The number of methyl groups per polymer molecule increases almost proportionally with the degree of polymerization. These facts indicate that short‐chain branching occurs mainly by the mechanism of intramolecular hydrogen transfer. The effect of pressure on the rate of chain branching can be postulated by considering the transition state to be six‐membered rings in hydrogen transfer reactions. The activation energy of chain branching is found to exceed that of propagation by 6 kcal./mole.
Solution properties of cellulose triacetate. I. Fractional precipitation
Authors: Howard P. , Parikh R. S. 
Published: April 2003

AbstractUsing petroleum ether as a precipitant and chloroform–acetone mixture as solvent, six fractions of cellulose triacetate were obtained by fractional precipitation. The molecular weight of each fraction was obtained from osmotic pressure measurements carried out on chloroform solutions. It was shown that virtual nonfractionability of cellulose triacetate with regard to molecular weight occurred in this system. This behavior was also observed in attempts to fractionate it from tetrachloroethane or acetic acid solutions. These results are explained by the hypothesis that specific polymer–solvent interaction takes place due to hydrogen bonding.
Degradation of polymers in high speed rotary homogenizers: A hydrodynamic interpretation
Authors: Harrington Rodney E. 
Published: April 2003

AbstractDilute solutions of DNA in neutral phosphate buffer and of polystyrene in toluene are degraded to limiting molecular weights by high speed stirring in a Virtis homogenizer equipped with special thin, highly sharpened blades. Results are interpreted and justified in terms of the hydrodynamic theory of laminar boundary layers. Estimates of critical stress values for chain scission are obtained at various limiting molecular weights for the two polymer systems, and the treatment is used to rationalize the dependence of degradation upon homogenizer speed. The agreement between the hydrodynamic theory and experimental data implies that limiting molecular degradation occurs entirely in the boundary layer region extending a distance equal to approximately the molecular contour length from the leading edge of the blade tip and that laminar flow conditions prevail in this region. It therefore seems likely that polymer molecules subjected to a critical shearing stress are essentially completely extended in the streamlines of flow. The hydrodynamic theory is finally used to explain the peculiar kinetics of molecular degradation in high speed rotary homogenizers.
Interfacial anodic polymers from benzene in hydrogen fluoride
Authors: Shepard A. F. , Dannels B. F. 
Published: April 2003

AbstractBenzene–HF mixtures containing two liquid phases exhibit unusual electrical conductivity characteristics on the addition of small amounts of H2O or KF. Maximum conductivity is obtained with the anode contacting the interface between the phases and the cathode either contacting the interface or situated in the HF layer. On electrolysis, with the anode contacting the interface, polymer forms as a flat horizontal plate extending out from the anode at interface level; hydrogen is evolved at the cathode. The polymer is swollen by the cell liquid, and this composite appears to conduct electricity by a nonionic mechanism, and shows directional variation of conductivity. After removal of cell liquid from the polymer deposit, the remaining polymer is infusible, insoluble, and possesses excellent heat and chemical and electrical resistance. Elementary analyses of dry polymers from water bearing systems show loss of more than 2H per C6H6 molecule and introduction of variable amounts of F and O. Organic anionic complexes appear to be involved in the polymerization.
Triad distributions of 1,1‐diphenylethylene–methyl acrylate copolymer determined from NMR study
Authors: Ito Koichi , Yamashita Yuya 
Published: April 2003

AbstractThe triad distributions of 1,1‐diphenylethylene (D)–methyl acrylate (M) copolymers have been determined from NMR measurements and examined according to the terminal and penultimate models of copolymerization theory. As expected from the diamagnetic shielding by the phenyl rings of the nearest D units, the methoxy proton resonances were found to appear as three resolved peaks at 6.4–6.6 τ, 6.7–7.0 τ, and 7.2 τ, and have been assigned to the central M units of the triads MMM, MMD or DMM and DMD, respectively. The copolymer composition and the triad distributions observed are shown to agree better with the terminal model with the methyl acrylate reactivity ratio of 0.092 ± 0.010 than with the penultimate model.
Fluorine NMR spectra of poly(vinyl trifluoroacetate)
Authors: Pritchard J. G. , Vollmer R. L. , Lawrence W. C. , Black W. B. 
Published: April 2003

AbstractSamples of poly(vinyl trifluoroacetate) with differing stereosequences have been prepared. The NMR signals at 56.4 Mc./sec. corresponding to the three types of triadstereosequences of the trifluoroacetate groups (isotactic, heterotactic, and syndiotactic) can be resolved. The results for specific polymers are discussed.
Diffusion of water vapor through a hydrophilic polymer film
Authors: Gillespie Thomas , Williams Bill M. 
Published: April 2003

AbstractMultifilm techniques have been used to measure the diffusion coefficient of water vapor in cellophane, and the data have been compared with the integral diffusion coefficient obtained in previous work with single films. The multifilm techniques lead to a much sharper resolution of the effect of concentration on diffusion, and the maximum integral diffusion coefficient. The diffusion coefficient for water vapor in cellophane peaks at a moisture content corresponding to about 70% R. H., which is presumably the “critical concentration” discussed in previous work on the thermodynamics of water sorption by cellophane.
Grafting vinyl monomers to starch by ceric ion. I. Acrylonitrile and acrylamide
Authors: Reyes Zoila , Rist C. E. , Russell C. R. 
Published: April 2003

AbstractStudies were carried out on the grafting of acrylonitrile (AN) and acrylamide (AA) to starch by ceric ion. The variables affecting the grafting of AN and AA were investigated with granular wheat starch dispersed in aqueous N,N‐dimethylformamide and ceric ammonium nitrate as catalyst. Results showed that the concentrations of monomer and catalyst are the major factors influencing the grafting of AN; thus the monomer content of the grafts can be regulated by these variables. The grafting of AA is also influenced by these variables, but to a much less degree. Increasing concentrations of monomer promote homopolymerization and increasing concentration of catalyst inhibit grafting. The extent of grafting of this monomer can best be controlled by reaction time. Under the most favorable conditions, maximum grafting efficiency (ratio of amount of grafted monomer to total amount of monomer converted to polymer) was 87% for AN and 43.8% for AA. Although the monomer content of the AN grafts was higher than that of AA grafts prepared under identical conditions, the number of branches in the grafts was almost the same; only the length of the branches was different. The AN‐starch grafts have branches of higher molecular weight.
Anionic heterogeneous polymerization of methacrylonitrile by n‐butyllithium
Authors: Feit Ben‐Ami , Heller Eri , Zilkha Albert 
Published: April 2003

AbstractThe anionic heterogeneous polymerization of methacrylonitrile by butyllithium in petroleum ether was investigated. The polymerization was of the “living” type, as seen from the linear dependence of the molecular weights on [MAN]/[BuLi]. This behavior was further supported by block polymerization experiments in which the monomer was added in two portions and the molecular weights obtained were directly proportional to the total monomer concentration. The initiator efficiency was low, and initiator consumption was only about 2%. This fact, together with the results of the block polymerizations showed that there was preferential addition of monomer to the growing chain ends rather than to the initiator. The molecular weights were independent of the rate of monomer addition. This as well as the “living” behavior of the polymerization of methacrylonitrile on a wide range of monomer and catalyst concentrations and the absence of chain transfer to monomer was essentially different from that of the similar heterogeneous polymerization of acrylonitrile by butyllithium previously investigated. This is due to the absence of an α‐acidic hydrogen in methacrylonitrile.
Polymerization of olefin oxides and of olefin sulfides
Authors: Lal Joginder 
Published: April 2003

AbstractTwo new catalyst systems, sulfur–diethylzinc and 98% hydrogen peroxide–diethylzinc, have been investigated for polymerizing propylene oxide. The sulfur–diethylzinc catalyst system has a broad range of sulfur/zinc atomic ratio for polymerizing propylene oxide heterogeneously to high molecular weight materials in high yields. The highest polymer yield is obtained at the sulfur/zinc atomic ratio of 3–3.5. Like the water–diethylzinc system, the hydrogen peroxide–diethylzinc system has a narrow range of hydrogen peroxide/diethylzinc molar ratio in the vicinity of 0.57 for optimum polymer yield. Crystallinity measurements by x‐ray diffraction of a few polymers prepared with these three catalyst systems showed that they are fairly similar in the extent of their crystallinity. A plot of the per cent of polymer insoluble in acetone against inherent viscosity of the original polymer also showed that the polymers prepared with sulfur–diethylzinc and hydrogen peroxide–diethylzinc catalyst systems have similar amounts of crystallinity. Data are given for the polymerizability of ethylene oxide, 1,2‐butene oxide, styrene oxide, propylene sulfide, 1,2‐butene sulfide, and a vulcanizable copolymer of propylene oxide and allyl glycidyl ether with the sulfur–diethylzinc catalyst system. The polymers from the olefin sulfides had lower inherent viscosities than the polymers from the corresponding olefin oxides. Aging of the sulfur–diethylzinc catalyst (S/Zn atomic ratio = 3.5) improved the yield of poly(propylene oxide). The yield was essentially unchanged when propylene oxide was polymerized in six different solvents. The formation of C2H5SxZnSC2H5 and C2H5SxZnSyC2H5 (x and y are integers between 2 and 8) and possibly C2H5SxZnC2H5 as the catalytically active species is postulated during the reaction of sulfur and diethylzinc.
Untersuchung der Bildung von Polyesteramiden aus Dicarbonsäure‐anhydriden und Oxazolidinonen‐2
Authors: Burckhardt S. , Reichert K.‐H. , Hamann K. 
Published: April 2003

AbstractThe well‐known reaction of dicarboxylic acid anhydrides with epoxides, catalyzed by bases and yielding linear polyesters, has been extended by a variation of the reactants. The reactions of succinic and phthalic anhydrides with N‐substituted oxazolidinones‐2, which by their tendency to split off CO2 may be regarded as ethyleneimine derivatives, give in the presence of a few mole percent of LiCl at 200–220°C. within 5–10 hr. polyester amides of molecular weights up to 3.500 in nearly quantitative yield. The polymer yield corresponds to the CO2 evolution indicating an equal consumption of oxazolidinone and anhydride in the reaction. The experimental activation energies of 22.8 and 20.2 kcal./mole for the reaction of 3‐phenyl oxazolidinone‐2 with succinic and phthalic anhydrides, respectively, fairly agree with earlier values reported for the corresponding reactions of the cyclic carbonates.
Polymerization of 1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose and 1,2‐O‐isopropylidene‐α‐D‐glucofuranose
Authors: Whistler Roy L. , Seib Paul A. 
Published: April 2003

AbstractA new method for preparing D‐glucose polymers is described. Isopropylidene derivatives of D‐glucofuranose, particularly the 1,2‐mono‐O‐derivative, are treated with Lewis acids, such as boron trifluoride, to eliminate acetone and produce a highly branched polymer with a molecular weight of 12,700. Approximately one isopropylidene unit remains, possibly on the potential reducing end of the glucan. Up to 95% of the polymer units are D‐glucopyranoside units indicating that ring expansion occurs during the condensation.
Polymerization of α‐halogenated p‐xylenes with base
Authors: Gilch H. G. , Wheelwright W. L. 
Published: April 2003

AbstractVarious α‐halo‐p‐xylenes have been polymerized with base yielding p‐xylylene polymers. The reaction involves a 1,6‐dehydrohalogenation to give a xylylene which then polymerizes. α,α′‐Dichloro‐p‐xylene forms poly‐α‐chloro‐p‐xylylene and polymers containing stilbene units; α,α,α′,α′‐tetrachloro‐p‐xylene gives poly‐α,α,α′‐trichloro‐p‐xylylene; alkyl, aryl, and halogen ring‐substituted α‐chloro‐p‐xylenes give the corresponding ring‐substituted poly‐p‐xylylenes. The more halogens in the α positions (up to five), the weaker the base necessary for dehydrohalogenation. Sodium hydroxide in methanol will polymerize tetrachloro‐p‐xylene, while potassium tert‐butoxide in refluxing p‐xylene is necessary to polymerize α‐chloro‐p‐xylenes. Stilbenes are formed when α‐halo‐p‐xylenes are reacted with potassium tert‐butoxide in polar solvents such as dimethyl sulfoxide.
Chemistry of polybutadiene—iron carbonyl systems
Authors: Berger M. , Manuel T. A. 
Published: April 2003

AbstractThe treatment of polybutadienes with iron carbonyls results in formation of polymers containing tricarbonyl(conjugated diene)iron units [C8H12Fe(CO)3] and also results in geometrical isomerization of free double bonds. Heating of the iron carbonyl‐containing polymers gives ferromagnetic products with enhanced thermal stability. The incorporation of iron carbonyl groups into the polymer is favored by basic solvents and high temperatures, the geometrical isomerization by acidic solvents and low temperatures. Steric factors are powerful in determining the rate of isomerization.