bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calorimetric investigation of polymerization reactions. III. Curing reaction of epoxides with amines
Authors: Horie K. , Hiura H. , Sawada M. , Mita I. , Kambe H. 
Published: April 2003

AbstractThe curing reactions of epoxy resin with aliphatic diamines and the reaction of phenyl glycidyl ether with butylamine as a model for the curing reactions were investigated with a differential scanning calorimeter (DSC) operated isothermally. The heat of reaction of phenyl glycidyl ether with butylamine is equal to 24.5 ± 0.6 kcal/mole. The rate of reaction was followed over the whole range of conversion for both model and curing reactions. The reactions are accelerated by the hydrogen‐bond donor produced in the system. The rate constants based on the third‐order kinetics were determined and discussed for the model reaction and for the chemically controlled region of curing reactions. The activation energies for these rate constants are 13‐14 kcal/mole. At a later stage of conversion, the curing reactions become controlled by diffusion of functional groups. The final extent of conversion is short of completion for most isothermally cured and even for postcured samples because of crosslinking. It was quantitatively indicated that the final conversion of isothermal cure corresponds to the transition of the system from a viscous liquid to a glass on the basis of the theory of glass transition temperature of crosslinked polymer systems.
Reduction of pendent ester groups in polycarbonates by use of diborane
Authors: White R. E. , Gardlund Z. G. 
Published: April 2003

AbstractA series of polycarbonates with pendent ester groups have been synthesized. These ester groups have been converted to hydroxyl functionalities by reduction with diborane in tetrahydrofuran. The number of methylene groups in the pendent chain has a large effect on the reducibility of the ester.
Polymerization of vinyl chloride by alkyllithium compounds
Authors: Jíšová V. , Kolínský M. , Lím D. 
Published: April 2003

AbstractThe polymerization of vinyl chloride initiated by alkyllithium compounds was investigated. The effect of temperature, initiator concentration, and monomer concentration on the conversion and the properties of the resulting polymers were studied. The optimum temperature in the investigated range (between −20°C and +20°C) was +5°C. The conversion is directly proportional to the concentration of both the initiator and the monomer. The molecular weight is inversely proportional to the initiator concentration and directly proportional to the monomer concentration. Under optimum conditions the molecular weight of the polymers is as high as 140,000. These results differ by an order from hitherto published data on the nonradical polymerization of vinyl chloride. The proportion of isotactic and syndiotactic structures resulting from the presence of tert‐butyllithium does not differ from that obtained by radical polymerization, but the occurrence of anomalous structures is reduced to a minimum. The stability of the macromolecules is higher. A mechanism of the polymerization is suggested.
Reaction of poly(vinyl alcohol) with formaldehyde and polymer stereoregularity. Model compounds
Authors: Shibatani Kyoichiro , Fujii Kiyoshi 
Published: April 2003

AbstractThe reaction of stereoisomers of pentane‐2, 4‐diol and heptane‐2, 4, 6‐triol with formaldehyde was investigated as a model for the formalization reaction of poly(vinyl alcohol) in order to determine effect of the stereochemical configuration of the polyol molecules on the reaction. The isotactic (meso) diol portion reacted with formaldehyde to give cis‐formal several times faster than did the syndiotactic (dl) diol portion to give trans‐formal at 30–80°C. In the reaction of heterotactic (meso‐dl) triol which provides both the isotactic and syndiotactic diol portions in a molecule, the proportion of trans‐formal in the total formal decreased as the reaction proceeded. This shows that the formation of cis‐formal is also favored thermodynamically to a greater extent, and hence the intramolecular migration of trans‐formal to cis‐formal did occur during the reaction. The rates of hydrolysis of formals of the diols were compared with those of the triols in order to see the effect of a hydroxyl group adjacent to the formal ring on the reaction. No appreciable rate difference was observed between the dimer and trimer models both in cis‐ and trans‐ formals. Therefore it was deduced from these results that the increase of the rate of hydrolysis of poly(vinyl formal) with the increase of hydroxyl groups along the polymer chain is a characteristic of macromolecules that is not observed in the low molecular weight models.
Copolymerization with depropagation. V. Copolymerization of α‐methylstyrene and methyl methacrylate between their ceiling temperatures
Authors: Izu M. , O'Driscoll K. F. 
Published: April 2003

AbstractThe variation of copolymer composition with monomer feed has been studied for the system α‐methylstyrene‐methyl methacrylate at 60, 114 and 147°C. The compositions predicted by the diad model of Part III of this series accurately describe the data.
High‐resolution proton magnetic resonance and infrared spectra of poly(vinyl formal) and its model compounds
Authors: Shibatani Kyoichiro , Fujiwara Yuzuru , Fujii Kiyoshi 
Published: April 2003

AbstractHigh‐resolution proton magnetic resonance and infrared spectra of poly(vinyl formal) were studied in comparison with those of the model formals obtained from stereoisomers of pentane‐2,4‐diol and heptane‐2,4,6‐triol in order to learn spectral changes due to differences of the steric structures of the polymer. In the NMR spectrum of transformal obtained from dl diol or dl,dl (syndiotactic) triol, all proton signals were well interpreted by assuming a rapid chair‐chair inversion of the formal ring. On the other hand, no such inversion was observed spectroscopically in cis‐formal obtained from the meso diol or meso,meso (isotactic) triol, and the cis‐formal ring was supposed to take a diequatorial form preferentially. Consequently, dioxymethylene protons gave a single peak (equivalent) in trans‐formal and an AB quartet (nonequivalent) in cis‐formal. In the spectra of poly(vinyl formal), the dioxymethylene signal was an overlap of the singlet and quartet in dimethylsulfoxide solution. Observations of the spectra of various poly(vinyl formals) obtained from poly(vinyl alcohols) of different tacticities and study of temperature dependence of the signal have shown that the singlet and quartet are attributed to trans‐ and cis‐ formals, respectively, in the polymer spectrum also. In the infrared spectra of poly(vinyl formals), the 800 and 785 cm‐1 bands were found to be related to cis‐ and trans‐formal rings respectively. A linear relationship was confirmed between D785/D800 and trans/cis ratios determined from the peak intensities of the dioxymethylene proton signals.
Termination rate constants in radical polymerization
Authors: Ito Katsukiyo 
Published: April 2003

AbstractA rate constant is generally derived by using Fick's equation corresponding to the spherical interdiffusion of particles. By using this rate constant, chain and primary radical termination rate constants can be approximated to rate constants for the bimolecular reactions between two radical chain ends, and primary radical and radical chain end, respectively. The former is given by ks = 8πNLDsLs exp { − Ls/Rs} × 10−3 1./mole‐sec. The latter is given by ksi = 4πNL(Ds + Di)Lsi exp { − Lsi/Rsi} × 10−3 1./mole‐sec. Here, NL is Avogadro's number; Ds and Di are the diffusion constants of radical chain end and primary radical, respectively; Ls and Lsi are, respectively, the distances between two radical chain ends and between a primary radical and a radical chain end at a thermal energy equal to the coulombic energy of interaction of the net charges; and Rs and Rsi are, respectively, the average distances between two radical chain ends and primary radical on a collision.
Electron spin resonance studies on graft copolymerization of gaseous styrene onto preirradiated polypropylene. I. Preirradiation in the presence of oxygen
Authors: Eda Bunzo , Nunome Keichi , Iwasaki Machio 
Published: April 2003

AbstractGraft copolymerization of gaseous styrene was carried out onto polypropylene preirradiated in the presence of oxygen at −78°C and at room temperature, respectively. The origin of the graft initiation activities of these polymers was investigated by means of electron spin resonance (ESR) of trapped radicals. More grafting was found for the polymers irradiated at −78°C than for those irradiated at room temperature. The difference of grafting between polymers irradiated at −78°C and those irradiated at room temperature was not explained by the total amounts of trapped radicals, and it was found that all radicals are not effective in the grafting reaction. ESR measurements showed that there exist two kinds of peroxy radicals, one has more effective ability of abstracting hydrogen atoms from the surrounding polymer chains to form carbon radicals, and another is less effective at the temperature of grafting reaction (40°C). Although the samples irradiated at −78°C contain the both types of radicals, those irradiated at room temperature do not contain the former type of radicals. It was shown that the carbon radicals produced by such a hydrogen abstraction reaction are actually the effective centers in the grafting reaction of polymers irradiated in the presence of oxygen.
Studies on monomer reactivity ratios. III. Comparison of various mathematical models
Authors: Hoyland James R. 
Published: April 2003

AbstractSeven mathematical models for the treatment of monomer reactivity ratios in free‐radical copolymerization are compared from the viewpoint of their relative simplicity, accuracy, and the number of parameters necessary for their use. It is concluded that the electronegativity and charge‐transfer models proposed in previous papers represent the best compromise for routine usage if quantitative accuracy is the primary concern.
High‐temperature pyrolysis of poly(vinyl chloride): Gas chromatographic‐mass spectrometric analysis of the pyrolysis products from PVC resin and plastisols
Authors: O'Mara Michael M. 
Published: April 2003

AbstractA pyrolysis–gas chromatographic–mass spectrometric technique for analyzing the pyrolysis products from polymers in an inert atmosphere is described. Initial studies encompassing the pyrolysis of poly(vinyl chloride) homopolymer and a series of PVC plastisols (based on o‐phthalate esters) have provided a complete qualitative and semi‐quantitative analysis of the pyrolysis products from these materials. PVC resin yields a series of aliphatic and aromatic hydrocarbons when pyrolyzed at 600°C; the amount of aromatic products is greater than the amount of aliphatic products. Benzene is the major organic degradation product. A typical PVC plastisol [PVC/o‐dioctyl phthalate (100/60)] yields, upon pyrolysis, products that are characteristic of both the PVC matrix and the phthalate plasticizer. The pyrolysis products from the plasticizer dilute those from the PVC portion of the plastisol and are, in turn, the major degradation products. There are no degradation products resulting from an interaction of the PVC with the plastisol. The pyrograms resulting from pyrolysis of the various plastisols of PVC can be used for purposes of “fingerprinting.” Identification of the major peaks in a typical plastisol pyrogram provides information leading to a precise identification of the plasticizer. The pyrolysis data from this study were related to a special case of flammability and toxicity.
Polymerization of acrylonitrile catalyzed by methoxo‐β‐diketone nickel chelates
Authors: Shono T. , Mori M. , Shinra K. 
Published: April 2003

AbstractThe polymerization of acrylonitrile initiated by methoxo‐β‐diketone nickel chelates of the [Ni(L)(CH3O)(CH3OH)]n type and pyridine was studied. Chelating agents L employed included acetylacetone, ethylacetoacetate, and salicylaldehyde. These systems could initiate the polymerization of acrylonitrile at −40°C. The polymerization is thought to occur by an anionic coordination mechanism.
1,2‐dinitrile polymers. III. Number‐average molecular weight by pulsed NMR technique
Authors: Liepins R. , Crist B. , Olf H. G. 
Published: April 2003

AbstractIn studies of various polymers in the solid state by pulsed and wide‐line NMR, a relationship between the spin‐lattice relaxation time and the fraction of mobile protons in the polymer sample was observed. This effect has been used to determine the degree of polymerization of a series of fumaronitrile homopolymers. The technique should have wide applicability in the direct determination of the number‐average molecular weight M̄n, especially for polymers that may be insoluble and/or infusible though not crosslinked.
Ladder polymers from tetraaminodiquinoxalpyrene
Authors: Arnold F. E. 
Published: April 2003

AbstractA new fused aromatic heterocyclic tetraamine 2,3,11,12‐tetraaminodiquinoxal [2,3‐e,2′,3′‐1] pyrene has been prepared and polymerized with 1,4,5,8‐naphthalenetetracarboxylic acid and pyromellitic dianhydride. The resulting ladder polymers with inherent viscosities ranging from 0.5 to 1.0 dl/g in methanesulfonic acid exhibited thermal stabilities near 600°C in nitrogen and near 450°C in air.
Synthesis of spiro polymers,
Authors: Bailey William J. , Volpe Angelo A. 
Published: April 2003

AbstractSynthesis of the first totally organic spiro polymer was accomplished by the reaction of 1,4‐cyclohexanedione and pentaerythritol in benzene plus a trace of p‐toluenesulfonic acid to produce the polyspiroketal. The polymer did not melt, but began to decompose at 350°C. Although it was insoluble in most common solvents, it was found to be soluble in hexafluoroisopropanol. The x‐ray diffraction indicated the polymer was very highly crystalline. A series of lower molecular weight related polymers were prepared by carrying out a similar condensation with a mixture of 1,4‐cyclohexanedione containing 5–50 mole‐% of cyclohexanone. In order to prepare a material with greater solubility, a polyspiroketal was prepared from 1,10‐cyclooctadecanedione plus pentaerythritol. This polymer was soluble not only in hexafluoroisopropanol, but to a limited extent in dimethyl sulfoxide.
Cyclic amine initiation of polypivalolactone
Authors: Wilson D. R. , Beaman R. G. 
Published: April 2003

AbstractCertain monocyclic and polycyclic tertiary amines initiate polymerization of, and copolymerize with, pivalolactone. These comprise three‐, four‐, and five‐membered monocyclic amines and 1‐azapolycyclic amines. The polymerization proceeds in three steps: (a) initiation to form a cyclic amine/pivalate betaine, (b) propagation to yield a polylactone zwitterion by an anionic mechanism, and (c) interlinking by a carboxylate end attacking a cyclic amine end to incorporate amine as a comonomer in the chain. When polymerization is carried out at low temperatures, the more stable cyclic amine ring systems yield isolatable step b polymers. These polymeric zwitterions undergo step c by heating, even in the solid state. The mechanism suggests that, for the more labile cyclic amines, a lactone could be the initiator for polyamine formation by a cationic mechanism. Interlinking would lead to incorporation of lactone initiator. In intermediate cases, block copolymers would result. With a proper balance of reactivities, 1:1 alternating copolymers would be possible.
Block copolymer from α,ω‐dihydroxyl polystyrene and polyethylene glycol
Authors: Shimura Yukio , Lin Wen‐Shi 
Published: April 2003

Abstractα,ω‐Dihydroxyl polystyrene was synthesized by the addition of styrene oxide to polystyryl dianion initiated with sodium naphthalene. Diglyme was found to be an unsuitable solvent for the preparation of low molecular weight compounds. Block copolymerization of the α,ω‐dihydroxyl polystyrenes (M̄n = 2250, 3140, and 6200) with poly(ethylene glycols) (M̄n = 404, 1960, and 5650) was pursued by introducing urethane linkages with 4,4′‐diphenylmethane diisocyanate. The mechanical, thermal, and viscoelastic properties, solution viscosity, molecular weight distribution, and moisture absorption of the block copolymers obtained were examined. Incorporation of styrene blocks was found to disturb the crystallization and fusion of poly(ethylene glycol) blocks. Films cast from benzene solution were soft and elastic and absorbed up to 5.8% moisture.
Hydrocarbon ladder aromatics from a Diels‐Alder reaction
Authors: Stille J. K. , Noren G. K. , Green L. 
Published: April 2003

AbstractThe Diels‐Alder homopolycycloaddition of 2,5‐diphenyl‐3,4‐(5,6‐acenaphthylenylene)‐cyclopentadienone (VIII) affords a low molecular weight soluble ladder polymer having reduced specific viscosities between 0.17 and 0.25 dl/g in benzene and an insoluble fraction of higher molecular weight. The ladder polymers exhibited a major TGA break at 450°C in an air atmosphere and lost approximately 30% of their weight at 700°C in a nitrogen atmosphere.
Synthesis of inherently dissymmetric polyamides,
Authors: Overberger C. G. , Yoshimura T. , Ohnishi A. , Gomes A. S. 
Published: April 2003

AbstractThe preparation of polyamides from derivatives of optically active biphenic acid is described. The diacid chlorides chosen were 2,2′‐dinitro‐6,6′‐dimethylbiphenyl‐4,4′‐dicarbonyl chloride and 2,2′‐dichloro‐6,6′‐dimethylbiphenyl‐4,4′‐dicarbonyl chloride, the diamines were phenyldiamines (o‐, m‐, p‐) piperazine, trans‐2,5‐dimethylpiperazine, and 1,2‐piperaazolidine. Polymerization was carried out by the method of interfacial polycondensation. The polymers of aromatic diamines were insoluble in common organic solvents but soluble in dimethylformamide containing 5% lithium chloride, triesters of phosphoric acid, and methanesulfonic acid. The polymers of aliphatic diamines were also insoluble in common organic solvents but soluble in trifluoroethanol. All polymers had melting points higher than 280°C.
Transformations of chloroethylenes in the presence of aprotonic acids
Authors: Zilberman E. N. , Kulikova A. E. , Pinchuk N. M. , Taikova N. K. , Okladnov N. A. 
Published: April 2003

AbstractThe cationic polymerization of vinyl chloride, vinylidene chloride, and cis‐ and trans‐ 1,2‐dichloroethylenes with the use of Lewis acid‐type catalysts has been studied. Vinylidene chloride is smoothly polymerized in the presence of ZnCl2 at 40°C to form the dimer, 1,1,3,3‐tetrachlorobutene‐1, and poly(vinylidene chloride) having somewhat increased crystallinity (45%). Vinyl chloride is polymerized very slowly in the presence of AlCl3 and TiCl4 to give dimeric, trimeric, tetrameric, and low molecular weight polymer products. The polymerization is followed by carbonium ion isomerization that leads to reaction products of branched structure. The cis‐ and trans‐1,2‐dichloroethylenes react in the presence of AlCl3 only at 50–60°C, and their polymerization is terminated at the stage of dimer and cyclic trimer formation. A mechanism of carbonium ion‐initiated polymerization of chloroethylenes is proposed, and the causes which lead to early termination of polymerization are discussed.
Photochromic polypeptides
Authors: Vandewyer P. H. , Smets G. 
Published: April 2003

AbstractTwo photochromic polypeptides were synthesized by reaction of 1‐(4‐iodobutyl)‐3,3‐ dimethylindolindolino‐6′‐nitrobenzospiropyran with poly‐L‐tyrosine; their molar contents on photochromic units were 27.3 and 44.7%. The spectra of the photo‐induced merocyanines and their decoloration kinetics were compared with these of the monomeric model compound, obtained by reaction of the same N‐(4‐iodobutyl)‐indolinospiropyran derivative with N‐acetyltyrosine methyl ester. Different types of solvents have been examined, mainly dimethylformamide and pyridine, acetone and tetrahydrofuran, and methanol and ethylene glycol. The polypeptides showed a much less pronounced solvatochromism than their model; on the other hand, their absorption spectra presented two absorption maxima instead of one for the model. These differences in photochromic behavior were interpreted on the basis of the solvatation of the polymeric chain. Inverse photochromism was observed for polypeptide P2 as well as for the model in ethylene glycol solution; this effect is due to a higher merocyanine content at the thermal equilibrium spiropyran ⇌ merocyanine in high polar solvent.
Kinetics of thermal and acidic degradation of poly‐1,3‐dioxolane
Authors: Kumpanenko E. N. , Varshavskaya A. I. , Karmilova L. V. , Enikolopyan N. S. 
Published: April 2003

AbstractThe kinetics and parameters of thermal and acidic degradation of poly‐1,3‐dioxolane were investigated in order to elucidate the mechanism of degradation and to obtain information on the nature of active centers. Both homolytic and heterolytic breaking of a macromolecule were shown to be random and occur at the acetal bond. Thermal degradation was found to proceed in two stages, depending on temperature and involving active centers of a different nature, i.e., macroions and macroradicals. The rate‐determining step of thermal degradation appears to be one involving the radical component, similarly to thermal degradation of olefin polyoxides. Acidic degradation occurs solely by the depolymerization mechanism, as in the case of polyaldehydes. It was concluded that the degradation mechanism depends not only on the chain structure and the thermodynamic properties of the system, but also on the nature of active centers.
Polymerization of coordinated monomers. V. Polymerization of methyl methacrylate–Lewis acid complexes
Authors: Hirai Hidefumi , Ikegami Tadashi 
Published: April 2003

AbstractThe polymerization of the complex of methyl methacrylate with stannic chloride, aluminum trichloride, or boron trifluoride was carried out in toluene solution at several temperatures in the range of 60° to −78°C by initiation of α,α′‐azobisisobutyronicrile or by irradiation with ultraviolet rays. The tacticities of the resulting polymers were determined by NMR spectroscopy. Both the 1:1 and the 2:1 methyl methacrylate–SnCl4 complexes gave polymers with similar tacticities at the polymerization temperatures above −60°C. With decreasing temperature below −60°C, the isotacticity was more favored for the 2:1 complex, whereas the tacticities did not change for the 1:1 complex. On the ESR spectroscopy of the polymerization solution under the irradiation of ultraviolet rays at −120°C, the 1:1 SnCl4 complex gave a quintet, while the 2:1 SnCl4 complex gave both a quintet and a sextet. The sextet became weaker with increasing temperature and disappeared at −60°C. This behavior of the sextet corresponds to the change of the tacticities of polymer for the 2:1 SnCl4 complex. An intra–intercomplex addition was suggested for the polymerization of the 2:1 complex, which took a cis‐configuration on the basis of its infrared spectra. The sextet can be ascribed to the radical formed by the intracomplex addition reaction, while the quintet can correspond to that formed by the intercomplex addition reaction. The proportion of the intracomplex reaction was estimated to be about 0.25 at −75°C, and the calculated value of the probability of isotactic diad addition of the intracomplex reaction was found to be almost unity.
Synthesis and properties of some linear oligobenzyls and polybenzyls
Authors: Montaudo G. , Bottino F. , Caccamese S. , Finocchiaro P. , Bruno G. 
Published: April 2003

AbstractProperties of some linear oligobenzyls corresponding to polybenzyl, poly(2,5‐dimethylbenzyl), and poly(2,3,5,6‐tetramethyl‐benzyl) systems are correlated to those of relative polymers. From infrared and x‐ray diffraction data, evidence is found that
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oligomers tend to assume the same crystal structure of the polymer as early as teh tetramer or pentamer stage. Syntheses of oligomers are described. Linear, crystalline polymers, necessary for comparison with oligomers, have been prepared and characterized. Polymerization conditions have been explored to some extent; relevant data are tabulated and discussed.