bluuebunny/crossref_metadata_2025_split huggingface dataset:
X‐Ray and thermal studies of nylon 5,7
Authors: Lin Ju‐Chui , Litt M. H. , Froyer Gerard 
Published: April 2003

AbstractThe unit cell and probable space group of Nylon 5,7 has been determined. The unit cell is monoclinic with the dimensions a = 0.483 nm, b = 0.935 nm, c = 1.662 nm, and γ = 58.9°. The space group is probably Pb which is noncentrosymmetric. Rolled, annealed samples show three‐dimensional orientation. The melting point peak of a rapidly cooled sample is about 213°C when it is heated at 20°C/min. Slow cooling, ≤°1°C/min generates a higher melting species, Tm = 228°C. Crystallinities are in the normal nylon range, up to 50% for a slow cooled sample.
Structure of chlorinated poly(vinyl chloride). X. Conclusions on the chlorination mechanism
Authors: Lukáš R. , Světlý J. , Kolínský M. 
Published: April 2003

AbstractThe chlorination of poly(vinyl chloride) (PVC) was investigated by using deuterated polymeric models of PVC, viz., α‐deuterated PVC (α‐d‐PVC) and β,β‐dideuterated PVC (β,β‐d2‐PVC). The chlorinated samples of PVC, α‐d‐PVC, and β,β‐d2‐PVC were examined by combining infrared (IR), 1H‐NMR, 13C‐NMR, and mass spectroscopy. The results obtained were used in a study of the reaction mechanism of PVC chlorination. The selectivity of chlorination and the extent of the substitution and elimination‐addition mechanism of chlorination are discussed with respect to the degree of chlorination and chlorination conditions.
Synthesis and optical properties of asymmetric polyamides derived from cyclopropyl diacids and diamines
Authors: Overberger C. G. , Nishiyama T. 
Published: April 2003

AbstractThe polyamides were prepared from the dicarbonyl chloride of (+) (S)‐ or (−)(R)‐trans‐1,2‐cyclopropanedicarboxylic acid (C3A) with either the dihydrochloride salt of (+)(S)‐ or (−)(R)‐trans‐1,2‐diaminocyclopropane (C3B) or the dihydrobromide salt of (+)(S)‐ or (−)(R)‐trans‐1,2‐bis(methylamino)cyclopropane (C3MB) by interfacial polycondensation. Several diamide model compounds composed of these monomers were also synthesized. The polyamides [poly(C3A‐C3B)] derived from C3A and C3B have the capability of hydrogen bonding, while the polyamides [poly‐(C3A‐C3MB)] derived from C3A and C3MB do not. Poly(C3A‐C3B) were insoluble in common organic solvents except strong acids. Poly(C3A‐C3MB) were soluble in common organic solvents. Poly(C3A‐C3B) had melting points higher than 300°C. Poly(C3A‐C3MB) melted at 180–235°C. The ORD and CD study has shown that poly(+)C3A(+)C3B in methane sulfonic acid (MSA), 2,2,2‐trifluoroethanol (TFE) (5 v % MSA), and tetramethylenesulfone (TMS) (5 v % MSA) exhibits a very strong Cotton effect or CD peak at 212–218 mμ, attributable to a component of the split π–π* transition of the amide chromophores. Poly(+)C3A(+)C3MB in MSA and TFE (5 v % MSA) shows a strong Cotton effect or CD peak at 217–223 mμ and an intermediate Cotton effect or CD trough at 202–204 mμ as well as an intermediate Cotton effect or CD trough at 220–222 mμ and an intermediate Cotton effect or CD peak at 202–204 mμ in TFE and TMS. These peaks and troughs may be assigned to splitting of the π–π* transition. The CD spectra of poly(+)C3A(+)C3MB in nonacidic media are quite different from those in acidic media: they are almost mirror images. The CD spectra in this transition induced by MSA suggests that a transition from a compact helix to another more extended helix with opposite handedness occurs similar to poly‐L‐proline I ⇄ II. This transition may be explained by electrostatic repulsion between protonated amide groups. Viscosity data have shown that the conformation is changed to a highly extended from in acidic media. The polyamides and diamides derived from enantiomers exhibit mirror image spectra. Poly(+)C3A(+)C3B and poly(+)C3A(+)C3MB in every solvent studied exhibit a marked enhancement of the rotatory strength of ORD and CD with respect to the corresponding diamide models.
Solid‐state polymerization of acrylamide and its derivatives complexed with lewis acids. I. Synthesis of complexes
Authors: Żurakowska‐Orszagh J. , Mirowski K. , Kaim A. 
Published: April 2003

AbstractComplexes of acrylamide, methacrylamide, and their homologs with zinc, cadmium, and mercury halides were prepared by various methods. Molecular compositions, the nature of the coordination, and some physicochemical properties (melting points and initial decomposition temperatures) were determined. The effect of the chemical structure of particular monomers, metal ion, and halide on the possibility of complex formation and on the properties of the complex compounds were observed. Most of these complexes have not been described in the scientific literature.
Functional polymers. IX. Polycarbonates and alternating copolycarbonates of bithionol
Authors: Deits W. , Vogl O. 
Published: April 2003

AbstractA number of polycarbonates, alternating copolycarbonates, polyurethanes, and terpolymers with carbonate and/or urethane linkages utilizing bithionol [2,2'‐thiobis(4,6‐dichlorophenol)] as the bisphenol component of the polymers have been synthesized. Bithionol has been demonstrated to give a polycarbonate with an inherent viscosity of about 0.5 dl/g. The polycarbonate is amorphous and has a glass transition temperatureTgof about 105°C. Alternating copolycarbonates and polyurethanes involving bithionol are most conveniently prepared from the bischloroformate of bithionol. An alternating copolycarbonate of bithionol and poly(ethylene glycol) of molecular weight 4000 has an inherent viscosity of more than 1.2 dl/g, is water soluble, and has characteristics similar to those of low‐density polyethylene. Alternating copolymers of bithionol and other hindered bisphenols have been synthesized and can be visualized as having an antibacterial agent and an antioxidant in the same polymer chain. These polymers have the potential to act as very useful materials for the controlled release of drugs while only forming carbon dioxide as the additional small molecule fragment on hydrolysis.
Crosslinking mechanism of an anhydride‐cured epoxy resin as studied by fourier transform infrared spectroscopy
Authors: Antoon M. K. , Koenig J. L. 
Published: April 2003

AbstractFourier transform infrared spectra, including absorbance difference spectra, are presented which indicate that the accepted mechanism of tertiary amine‐catalyzed copolymerization of cyclic anhydrides and epoxy resins requires modification. Results also show that the kinetic model is complicated by the lack of steady‐state concentrations of the active species. The effect of silica filler and silane coupling agents on the reaction are also examined.
Spontaneous copolymerization of 1,3‐cycloheptadiene with acrylonitrile in the presence of zinc chloride
Authors: Nagai Katsutoshi , Machida Shuji 
Published: April 2003

AbstractThe reaction of 1,3‐cycloheptadiene (1,3‐CHpD) with acrylonitrile (AN) in the presence of ZnCl2 leads spontaneously to the simultaneous formation of an alternating copolymer and a small amount of cycloadduct. The copolymer has a predominantly cis‐1,4‐structure. The formation of the charge—transfer complex between 1,3‐CHpD and (AN)c (AN coordinated to ZnCl2) in AN was detected by ultraviolet (UV) spectroscopy. The activation energies for the cycloaddition and for the copolymerization under the conditions used were determined to be 17.6 (in the presence of 1,1‐diphenyl‐2‐picrylhydrazyl) and 16.3 kcal/mole, respectively. The rate of copolymerization in AN was found to depend on the 1.5th power of the concentrations of (AN)c and of 1,3‐CHpD. Oxygen and UV irradiation causes an acceleration of the copolymerization only. On the basis of these results the mechanism of the spontaneous copolymerization is discussed and its relation to the cycloaddition in systems of 1,3‐cyclodienes and AN in the presence of ZnCl2 is mentioned.
Synthesis of polysulfone‐sulfides by polyadditions of dithiols to divinyl sulfones
Authors: Imai Yoshio , Asamidori Yasunobu , Inoue Tomihiro , Ueda Mitsuru 
Published: April 2003

AbstractPolyadditions of 1,6‐hexanedithiol and 1,10‐decanedithiol to divinyl sulfone (DVS) in hexamethylphosphoramide in the presence of triethylamine or potassium fluoride afforded polysulfone‐sulfides (IIIa and IIIb) with inherent viscosities as high as 0.8 dl/g. Polymerizations of other dithiols with DVS and distyryl sulfone (DSS) were also carried out, however, only low‐molecular‐weight polymers were obtained. A series of polymers derived from DVS were highly crystalline and soluble in hot dimethylacetamide and hot m‐cresol, whereas a polymer from DSS was quite amorphous and showed excellent solubility in a wide range of solvents. Polymers IIIa and IIIb had melting temperature below 150°C.
Reactions of 2‐methoxy‐ and 2‐substituted 4,6‐diamino‐s‐triazines with formaldehyde: Kinetics and adaptability of the rate constants to hammett and taft equations
Authors: Tashiro Tatsuo , Oiwa Masayoshi 
Published: April 2003

AbstractThe reactions of 2‐methoxy‐4,6‐diamino‐s‐triazine (MT) with formaldehyde (F) were studied in the pH region 2–11. In an alkaline medium the rate constants were proportional to the concentration of hydroxyl ion in the pH range 9.90–10.95; in a neutral medium they were approximately constant and in an acidic medium they achieved the maximum value at pH 3.50 (half‐neutralization point of MT). The hydroxymethylation mechanism of MT was similar to that of melamine. The hydroxymethylation rate constants of various 2‐substituted 4,6‐diamino‐s‐triazines(XT) were determined at pH 7.00, 10.26, and 4.00. Linear relationship was observed between the rate constants at pH 7.00 and pKb of XT, σm, and σ* but not at pH 10.26 and 4.00.
Peculiarities of polyacrylamide analysis by aqueous GPC
Authors: Klein Joachim , Westerkamp Aloys 
Published: April 2003

AbstractVarious commercially available stationary phases of gel permeation chromatography (GPC) were tested to determine their effectiveness in aqueous exclusion chromatography. It was found that controlled pore glass (GPG) is the most suitable material for the separation of polyacrylamides and poly(acry1amide‐co‐sodium acrylate), dextrans, and poly(sodium styrene–sulfonates) in 0.1M aqueous Na2S04 solutions of ionic strength 0.3. A calibration curve was established by using broad molecular weight distribution polyacrylamide standards in a trial and error procedure. To avoid artificial oscillations on the evaluated distribution curves a cubic B‐spline representation of the calibration curve was used instead of the conventional polynomials. By applying this system the solution instability of polyacrylamides was observed by GPC and is discussed because of its general importance to the applicability of indirect molecular weight determination methods for polyacrylamides. The effectiveness of aqueous GPC was demonstrated in an evaluation of thermal degradation measurements of polyacrylamides. Finally, the feasibility of universal calibration of aqueous GPC by means of poly(sodium styrene–sulfonates) was investigated. It is apparent that in spite of some problems concerning adsorption of the polymer universal calibration is a successful tool for calibrating aqueous GPC.
Condensation polymerization of pyromellitic dianhydride with aromatic diamine in aprotic solvent: A reaction mechanism
Authors: Kumar Devendra 
Published: April 2003

AbstractBased on nuclear magnetic resonance (NMR) studies, a probable reaction mechanism was proposed for the condensation polymerization of pyromellitic dianhydride with aromatic diamines in aprotic solvent, N,N‐dimethylacetamide (DMAc), to yield aromatic polyimides. The mechanism shows the essential role played by the solvent during polymerization reaction and in imidization. It explains the formation of polyamic acid and that of its high molecular weight buildup under the conditions in which solid dianhydride was added to the solution of diamine in DMAc. A prepolymer complex formation was observed, along with the main polyamic acid, when solid diamine was added to the solution of dianhydride in DMAc. The structure of the prepolymer was derived on the basis of NMR and its formation explained in the mechanism. The nature of the prepolymer was such that on treatment with anhydride it goes to polyamic acid.
Styrene emulsion polymerization: Particle‐size distributions
Authors: Lichti Gottfried , Hawkett Brian S. , Gilbert Robert G. , Napper Donald H. , Sangster David F. 
Published: April 2003

AbstractData are presented on the time evolution of particle‐size distributions (PSDs) in seeded and ab initio styrene emulsion polymerization systems. Initiation was by chemical reagent (potassium persulfate) or γ‐radiation. The unswollen PSDs at various times during interval II of the polymerization were obtained by direct measurement of calibrated electron micrographs. Experimental results were fitted with the equations that describe the time evolution of an initial PSD. Analytic solutions to these equations that allow for entry, exit, and propagation of free radicals were obtained. The values of the rate coefficients for these processes used to fit the experimental data were in excellent agreement with those obtained from dilatometric kinetics experiments.
Theory of emulsion copolymerization kinetics
Authors: Ballard Mathew J. , Napper Donald H. , Gilbert Robert G. 
Published: April 2003

AbstractAn extended Smith–Ewart theory is presented which provides a description for kinetic properties of an emulsion copolymerization system during intevals II and III (i.e., after completion of latex particle formation). Differential equations are derived specifying the time evolution of the copolymer compositions and of the copolymer sequence distributions in terms of the rate coefficients for free radical entry, exit, homopropagation, cross propagation, cross transfer, and cross termination. Solutions to these equations show how an emulsion copolymer system may be designed to give formed polymer with desired composition and/or sequence distribution functions.
Polymerization of aromatic nuclei. XXVII. ESR studies on polymers and oligomers from reaction of benzenoid and naphthalene monomers with lewis acid catalyst–oxidant systems
Authors: Hsing Chih‐Fen , Jones Martin B. , Kovacic Peter 
Published: April 2003

AbstractChlorobenzene and toluene were polymerized with aluminum chloride–cupric chloride to produce materials that consist mainly of poly(o‐phenylene) structures. These species exhibited radical cation concentrations comparable to that of poly(p‐phenylene). Polymerization of naphthalene and 1‐chloronaphthalene with aluminum chloride–cupric chloride or ferric chloride–water also resulted in products with high radical cation concentrations. Polynuclear structures may be responsible for the paramagnetic character; alternatively, p‐quinoidal moieties may be present in naphthalenes. The depth of color in the samples is directly related to the concentration of radical cations.
Kinetics and mechanism of the polymerization of styrene–acrylonitrile in the presence of polybutadiene
Authors: Hayes Robert A. , Futamura S. 
Published: April 2003

AbstractThe mechanism of free radical grafting of styrene–acrylonitrile with polybutadiene was studied. By assuming a copolymerization mechanism an equation that related the amount of homopolymer formed and its molecular weight to a reactivity ratio and the charged ratio of monomer to polydiene was derived. Polymerizations that contained a variety of ratios of monomer to polybutadiene, two different catalysts, and variable amounts of a mercaptan modifier were studied. The weight fraction of homopolymer and its molecular weight were determined by high‐speed GPC. The results were analyzed by the new equation and all showed a constant value of the reactivity ratio, which strongly suggests that the mechanism of the grafting reaction is copolymerization. Evidence that suggests that none of the grafting is a result of a hydrogen abstraction mechanism is also presented.
Radiation‐induced cationic dimerization and polymerization of styrene in methylene chloride solution. I
Authors: Gotoh Tetsuya , Yamamoto Masahide , Nishijima Yasunori 
Published: April 2003

AbstractRadiation‐induced polymerization of styrene in methylene chloride solution or bulk system was investigated to explain the initiation mechanism of cationic polymerization. It was found that high energy radiation produces polymers and dimers. The main dimers were identified as trans‐1,2‐diphenylcyclobutane, 1‐phenyl‐1,2,3,4‐tetrahydronaphthalene, and 1‐phenyl‐1,2‐dihydronaphthalene. The dimerization procedure was cationic in a pattern similar to that obtained in photoexcited EDA systems. It was shown clearly by product analysis that the bonded dimer cation radical intermediate, which was assumed to be an initiating species of the cationic polymerization, was produced in a radiation‐induced polymerization system. The observed polymerization was composed of two types; cationic and radical, the latter initiated by radical species.
Synthesis of polyamides from active diacyl derivatives of 3‐hydroxy‐1,2‐benzisoxazole and diamines under mild conditions
Authors: Ueda Mitsuru , Harada Toshiaki , Aoyama Shigeto , Imai Yoshio 
Published: April 2003

AbstractNew active diesters and diamides derived from 3‐hydroxy‐1,2‐benzisoxazole were prepared for use in polyamide synthesis. The active esters and amides reacted readily with amines to give quantitative yields of amides. The high reactivity to these active esters and amides was discussed in relation to the electon‐withdrawing effect of the leaving group and intramolecular general‐base catalysis. Solution polycondensation of new active diesters and diamides with aliphatic and aromatic diamines proceeded slowly under mild conditions to produce polyamides with inherent viscosities up to 1.5.
Photocrosslinking and thermal behavior of the polyesters containing conjugated diacetylenes
Authors: Patil A. O. , Deshpande D. D. , Talwar S. S. , Biswas A. B. 
Published: April 2003

AbstractA series of polyesters containing conjugated diacetylenic groups in the polymer backbone were synthesized by interfacial condensation of 3,5‐hexadiyne‐1,6‐diol and diacid chlorides of succinic, glutaric, adipic, azealic, sebacic, terephthalic, and isophthalic acids. The polyesters were characterized by their infrared and ultraviolet absorption spectra, elemental analysis, and viscosity measurements. Powder x‐ray patterns indicated high degress of crystallinity. The polyesters were found to be highly photoreactive. The relative photoreactivities of the polyester films were determined by the adhesion method. Only small differences in the reactivity have been observed despite structural changes in the R group in the polymer backbone. Differential thermal analysis behavior of all polymers in the temperature range ambient to 300°C and isothermal behavior of HGI at two different temperatures have been studied.
Structure study of the furan–maleic anhydride copolymer
Authors: Ragab Yousif A. , Butler George B. 
Published: April 2003

AbstractA structural study of furan–maleic anhydride copolymer (F–MAH) was undertaken to confirm its alternating nature and to determine its microstructure. The spectral properties of a model compound representing the alternating repeat unit, 2‐(2‐tetrahydrofuranyl)succinic anhydride, were compared with those of F–MAH. Their infrared (IR), 1H, and 13C nuclear magnetic resonance (NMR) spectra (after compensating for the absence of the olefinic double bond) were in good agreement with those of the copolymer. Furthermore, the observed splitting in the 1H‐ and 13C‐NMR spectra of F–MAH were assigned to cis–trans linkages on both the F and MAH units, with cis linkage being favored on both units, especially the former. The structure of 2,5‐dimethylfuran (DMeF)–MAH copolymer is similar to that of F–MAH copolymer, except that the preference of cis linkages is less pronounced. The structure of 2‐methylfuran (MF)–MAH copolymer is a complex structure with numerous 2,3‐furandiyl units. A mechanistic study was undertaken to elucidate the roles of F–MAH Diels–Alder adduct, and the charge‐transfer (CT) complex in the radical initiated copolymerization. The adduct reverted substantially to monomers under the reaction conditions; but, the amount of adduct remaining at equilibrium was quite appreciable; therefore, its participation could be ruled out on this basis alone. However, on polymerizing the adduct in the presence of F‐d4, the latter was incorporated into the copolymer to an extent indicative of free monomer exchange. Therefore, the adduct cannot be directly involved in the polymerization.
Use of 13C‐NMR in the study of reactions on crosslinked resins
Authors: Hodgkin J. H. , Willing R. I. , Eibl R. 
Published: April 2003

AbstractCrosslinked poly(3,4‐pyrrolidinediylethylene)s with functional side chains that contain acid and ester groups were synthesized by a number of different methods and the structures of the various resins were compared by 13C‐NMR studies. The advantages and problems of this technique for structural determination of crosslinked polymers are compared with those methods normally used; for example, infrared (IR) and elemental analysis. Preliminary selective metal chelating abilities of the resins were determined.
13C‐NMR sequence analysis of polyesters from pentaerythritol and caprolactone
Authors: Newmark Richard A. , Runge Michael L. , Chermack Julie A. 
Published: April 2003

AbstractReaction of pentaerythritol (1) or dipentaerythritol with caprolactone yields prepolymers of the general structure

for i = 1, 2, 3, and 4 (2)‐(5). The 13C chemical shifts of the quaternary carbons in (1)‐(5) differ by more than 0.5 ppm. Conditions were determined to obtain quantitative intensity ratios of these carbons. The relative intensities give the distribution of the various branched structures and permit calculations of the average number of caprolactones per branch. Results are reported for caprolactone/polyol mole ratics of 3‐66.
Asymmetric selective polymerization of racemic methacrylates with the cyclohexylmagnesium bromide‐(−)‐sparteine system
Authors: Okamoto Yoshio , Urakawa Kazuhiko , Yuki Heimei 
Published: April 2003

AbstractAsymmetric selective (or stereoelective) polymerization of various racemic methacrylates with cyclohexylmagnesium bromide (c‐HexMgBr)‐(‐)sparteine (1/1.2) catalyst was studied in toluene at −78°C. The methacrylates of α‐ethylbenzyl (EBMA), α‐isopropylbenzyl (i‐PBMA), α‐tert‐butylbenzyl (t‐BBMA), sec‐butyl (s‐BuMA), 1‐methylallyl (1‐MAMA), 2,3‐epoxypropyl (2,3‐EPMA), 2‐phenylpropyl (2‐PPMA), and menthyl (MentMA) alcohols were used as racemic monomers. In the polymerization of EBMA and i‐PBMA (S) enantiomers were consumed preferentially and the optical purity of initially polymerized i‐PBMA was as high as 97%. Optically pure (R) monomers were recovered at about 60% conversion for i‐PBMA and 80% for EBMA. In t‐BBMA, however, the (R) monomer was consumed preferentially over the (S) isomer. In the polymerization of s‐BuMA and 1‐MAMA (S) monomers were consumed in excess and the optical purity of the polymers formed in the early stage was about 30%. In 2,3‐EPMA and 2‐PPMA, which have asymmetric centers at the β position from the ester oxygen, (R) antipodes were more reactive. MentMA did not polymerize at −78°C. Enantiomer selectivity ratios rS and rR were determined in the polymerization of EBMA, i‐PBMA, and 1‐MAMA. All polymers except poly(t‐BBMA) were highly isotactic, but the tacticity of poly(t‐BBMA) could not be estimated. Circular dichroism spectra of optically active polymers of α‐substituted benzyl esters were measured.