bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acidic peroxo salts. A new class of initiators for vinyl polymerization. I. Kinetics of polymerization of acrylonitrile initiated by potassium monopersulfate catalyzed by Ag(I)
Authors: Samal Rajani K. , Das R. R. , Nayak M. C. , Suryanarayana G. V. , Panda G. , Das D. P. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylonitrile initiated by KHSO5 and catalyzed by Ag(I) have been investigated in an aqueous medium over the temperature range of 35–50°C. The rates of polymerization Rp have been calculated and studied with respect to monomer and initiator. The catalytic activity of various metal ions on the initiator has been determined from a comparison of Rp values. The effects of monomer, catalyst, neutral salts, various amines, and inhibitor (hydroquinone) on the initial rate as well as maximum conversion have been studied. From the kinetics results a suitable reaction scheme has been proposed.
Energy transfer in connection with the photo‐oxidation of polystyrene and its blends with poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Jensen J. P. Tovborg , Kops J. 
Published: April 2003

AbstractBy fluorescence spectroscopy it is possible to investigate some of the photophysical processes, particularly the energy transfer, that occur during the photo‐oxidative degradation of polystyrene (PS), poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), and homogeneous blends of these. In connection with the irradiation, a part of the absorbed energy is transferred from excited phenyl groups in PS to PPO. The decrease in PS excimer fluorescence at 319 nm by admixture of PPO is greater than expected from the absorption of PPO at the excitation wavelength. A radiative energy transfer is suggested from PS to PPO which absorbs at 319 nm. Energy transfer also occurs to groups formed during photo‐oxidation. The quenching of PS excimer fluorescence during the process has been studied for both the homopolymer and the blends, and in all cases the reactions occurring during photo‐oxidation result in marked quenching at 319 nm.
Thermal degradation study of phenolphthalein polycarbonate
Authors: Lin M. S. , Bulkin B. J. , Pearce E. M. 
Published: April 2003

AbstractPhenolphthalein polycarbonate underwent complicated thermal degradation which included random scission, rearrangement, hydrolysis, Friedel‐Crafts acylation, and cross‐linking. The carbonate group and lactone ring were both susceptible to thermal deterioration. Kinetic parameters were determined from the dynamic TGA thermograms. During early stages of degradation the measured reaction order was nearly 1, which suggested a random chain scission mechanism. The measured activation energy was 42.6 kcal/mol, compared with 41.2 kcal/mol calculated from isothermal aging. The Arrhenius preexponential constant was 3.09 × 1011 min−1. Below 80% weight residue the plot of fractional weight against 1/T revealed that complicated reactions with different activation energies occurred simultaneously and resulted in a final overlap of TGA curves for different heating rates indicative of cross‐linking and a lower preexponential constant. The reaction order changed and kept increasing in the last stages of degradation. Pyrolysis of this polymer was performed at 350°C under vacuum, followed by GC‐mass spectroscopic identification of products. The volatile products (17.5%) contained CO2, CO, O2, H2O, phenol, fluorenone, diphenyl carbonate, xanthone, anthraquinone, 2‐hydroxylanthraquinone, 2‐benzoxyanthraquinone, phenolphthalein, and trace amounts of benzoxyphenol and hydroquinone; the other 82.5% of products was insoluble gel. Functional group changes were examined by Fourier transform infrared spectroscopy (FT‐IR). Lactone, carbonate, and aromatic absorptions decreased during degradation. Increasing absorptions at 1739, 1728, 1280–1200, and 1138–1075 cm−1 were believed to result from aromatic ester (1728 cm−1) and phenyl aromatic ester (1739 cm−1) cross‐linkages ortho to the aromatic ether group (increases at 1155 cm−1 and 1280–1200 cm−1). Existence of 2‐hydroxyanthraquinone and xanthone contained in the crosslinked polymer matrix were also detected. Mechanisms for random scission, rearrangement, Friedel‐Crafts acylation, hydrolysis, and cross‐linking were suggested.
Aromatic polyamides. III. Mechanistic studies on the role of substituent chlorine in flame retarding aromatic polyamides
Authors: Khanna Y. P. , Pearce E. M. 
Published: April 2003

AbstractThe flammability of poly(1,3‐phenylene isophthalamide) and poly(chloro‐2,4‐phenylene isophthalamide) was measured by the oxygen index method. The chloro polyamide had reduced flammability shown by a 10–15 higher oxygen index. Analysis of the chars of the two polymers at 700°C by thermogravimetry (TGA) and elemental analysis showed that the chlorine caused a significant increase in the retention of C, H, N, and O in the pyrolysis residue. Most of the chlorine in the chloro polyamide, however, was lost by 700°C. Based on these results, we have suggested that the chlorine imparts flame retardancy by a combination of vapor‐ and condensed‐phase mechanisms. The origin of condensed‐phase activity is discussed.
Elementary radical formation and conversion processes in γ‐irradiated polyvinylchloride
Authors: Torikai Ayako , Adachi Tetsumi , Fueki Kenji 
Published: April 2003

AbstractElementary processes of γ‐irradiated polyvinylchloride (PVC) have been investigated by both electron spin resonance (ESR) and optical absorption measurements. On irradiating PVC film with γ rays at −196°C, alkyl‐type radicals are produced. When the PVC film is warmed to room temperature, the radicals convert to polyenyl type. γ Irradiation of PVC film containing biphenyl (Ph2) or pyrene (Py) at −196°C yields the corresponding radical cation. The relative ESR peak heights of the radicals decrease and the G values for the formation of cation radicals increase with increasing additive concentrations. These facts indicate that energy is transferred from the precursor of the radicals to the additive. In the case of PVC film containing Py, the Py cation radical decreases and the cyclohexadienyl‐type radical from Py is produced by thermal annealing. A possible mechanism for radical formation and conversion is proposed.
Synthesis of carbon‐carbon chain polymers by phase‐transfer‐catalyzed polycondensation of phenylacetonitrile with activated dichlorides
Authors: Imai Yoshio , Kameyama Atsushi , Nguyen Tien‐Quang , Ueda Mitsuru 
Published: April 2003

AbstractTwo‐phase polycondensation of phenylacetonitrile with α,α′‐dichloro‐p‐xylene and other activated dichlorides in an aromatic solvent‐aqueous sodium hydroxide system with various phase‐transfer catalysts produced carbon‐carbon chain polymers with inherent viscosities up to 0.6 dL/g. Reaction variables of the polycondensation are discussed in some detail. These polymers had melting temperatures below 220°C and were soluble in tetrahydrofuran and polar aprotic solvents that included dimethylformamide and dimethyl sulfoxide.
A carbazole‐based polymeric azodye
Authors: Biswas Mukul , Das Sukhendu K. 
Published: April 2003

AbstractA new polymeric azodye has been synthesized from carbazole by diazotization of its derivative N‐methylcarbazole‐3,6‐diamine and subsequent coupling reaction with 2,2‐bis(4‐hydroxyphenyl‐3‐sulfonate‐Na)‐propane prepared from bisphenol‐A. Its physico‐chemical, electrical, and thermal properties have been characterized; finally, its application to the preparation of colored semiconductive films from polyvinyl alcohol has been studied.
Radical capture efficiencies in emulsion polymerization
Authors: Hawkett Brian S. , Napper D. H. , Gilbert R. G. 
Published: April 2003

AbstractA theoretical procedure is developed that allows the importance of bimolecular termination in the aqueous phase of an emulsion polymerization to be determined. This shows that with sparinglysoluble and slowly propagating monomers like styrene, significant termination occurs in the aqueous phase at high initiator concentrations, as found experimentally. With more water soluble monomers, aqueous phase termination is likely to be small.
Branching kinetics in copolymerization of styrene with a chain‐transfer monomer
Authors: Tung L. H. 
Published: April 2003

AbstractIn an earlier work it was shown that a random long‐chain branching structure can be incorporated in polystyrene by copolymerizing styrene with a small amount of monomer that contains a chain transfer group. The use of vinylbenzylthiol as the chain transfer monomer produced a polystyrene with low number‐average molecular weight and a degree of branching lower than expected. In this study polymerization kinetics were used to compute the theoretical molecular weight and degree of branching. The results show that if the chain‐transfer constant of the chain transfer monomer is as high as that for vinylbenzylthiol the expected molecular weight and degree of branching will indeed be as low as those found experimentally. The theory also predicts that if the chain transfer constant is near one a highly branched bushy structure will result.
Polymerization of coordinated monomers. XVIII. Sequence distribution in methyl acrylate–styrene copolymers prepared in the presence of zinc chloride
Authors: Tanabe Tsuneaki , Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

AbstractMethyl acrylate and styrene have been copolymerized in the presence of zinc chloride either by photoinitiation or spontaneously. The copolymerization mechanism is investigated by analyses of copolymers composition and monomer sequence distribution. The resulting copolymers are not always alternating, their composition being dependent especially on the monomer feed ratio. Appreciable deviation to higher methyl acrylate unit content from an equimolar composition occurs at monomer feed fractions of methyl acrylate over 0.7. The larger deviation is induced by higher temperature, by photoirradiation, and by greater dilution of the reaction mixture with toluene. The 13C‐NMR spectrum of the alternating copolymer shows a sharp singlet at the carbonyl region, whereas the spectra of random copolymers prepared by benzoyl peroxide initiation at 60°C show a triplet splitting at the carbonyl carbon region, irrespective of copolymer composition. The relative intensities of the triplet peaks for the random copolymers are in good correspondence to the contents of triad sequences calculated by means of conventional radical copolymerization theory. These results clearly indicate that the carbonyl splitting is caused predominantly by variation of the monomer sequence and not by variation of the stereosequence. The monomer sequence distribution in the copolymers is thus directly and quantitatively measured from the split carbonyl resonance. Although the same triplet splitting appears in the spectra of methyl acrylate–rich copolymers prepared in the presence of zinc chloride at high feed ratios (>0.7) of methyl acrylate, the relative intensities of the split peaks do not fit the sequence distributions of random copolymers calculated by means of the Lewis–Mayo equation. The copolymerization yielding these peculiar sequences and the alternating sequence in the presence of zinc chloride is fully comprehended by a copolymerization mechanism proceeding between two active coordinated monomers, i.e., the ternary molecular complex composed of zinc chloride, methyl methacrylate, and styrene, and the binary molecular complex composed of zinc chloride and methyl methacrylate.
Functional monomers and polymers. XCIV. Photochemical reactions on the synthetic polymers containing thymine bases in the presence of adenine derivatives
Authors: Kita Yasuo , Uno Taizo , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractPhotodimerization reactions of polyacrylate and polymethacrylate derivatives and the dimer model compound containing thymine bases were studied in the presence of adenine derivatives in dimethyl sulfoxide; N,N‐dimethylformamide; and dimethyl sulfoxide–ethylene glycol solutions. The photodimerization of thymine bases both in the polymers and in the dimer model compound was found to be quenched by the addition of adenine derivatives. Base‐base interaction in the ground state was also studied by ultraviolet (UV) spectroscopy in the three solvents. The quenching of the photodimerizationof thymine bases in the presence of adenine derivatives was discussed in terms of the specific interaction between adenine and thymine bases both in ground and excited states.
Studies of some bioactive N‐p‐methacrylamidobenzoic esters
Authors: Lu (C. X. Lu) Chengxun , Yang Jijin , Leng Liecheng , Feng (S. T. Voong) Xinde , Li Dechang 
Published: April 2003

AbstractPreparations of four typical bioactive esters of N‐p‐methacrylamidobenzoic monomers and their reactive polymers as immobilized trypsin carriers are described. N‐p‐methacrylamidobenzoic active ester monomers containing COONB, COOSu, COOObt, or COOBT group can react with an aliphatic amine such as benzylamine at room temperature to give an identical product, N‐benzyl‐p‐methacrylamidobenzamide. However, only monomers with COOObt or COOBT group can also react with an aromatic amine such as aniline to give N‐phenyl‐p‐methacrylamidobenzamide. These monmoers polymerized readily in solution with azobisisobutyronitrile as free‐radical initiator; the polymers were used to immobilize trypsin. Among the four different active esters for the immobilization of trypsin, thE HONB and HOSu active ester showed rather higher bioactivities than the HOObt or HOBT active ester under the same conditions. Both P(MABONB)‐trypsin and P(MABOSu)‐trypsin matrices possess higher biological activities by about four or three times that of P(MABOObt)‐trypsin or P(MABOBT)‐trypsin matrices, respectively. It is proposed that these rather high bioactivities may be attributed to the “specific” aminolysis of reactive polymer with COONB or COOSu active ester group by aliphatic amino substituents.
Time dependence of crack healing
Authors: Wool R. P. , O'Connor K. M. 
Published: April 2003

AbstractWe propose that crack healing in polymers occurs by the stages of surface rearrangement, surface approach, wetting, diffusion, and randomization. The stages of wetting and diffusion are responsible for the majority of the mechanical property recovery or healing, and control the intrinsic healing function Rh(t). However, the observed macroscopic recovery R is a convolution product of Rh(t) and a wetting distribution function Φ(t). Each Rh(t) function contains a wetting and diffusion component. Experiments were designed to investigate intrinsic healing functions for fracture stress, strain, and energy; the results were found to be in excellent agreement with theory.
Synthesis of carbonate‐containing high temperature poly(arylene‐siloxanylenes)
Authors: Rosenberg Harold , Tsai Tsu‐Tzu , Ngo Ngoc Kim 
Published: April 2003

AbstractA method for the first synthesis of high molecular weight carbonate‐containing siloxanylene polymers was successfully developed. The procedure covered the preparation and polymerization of pure carbonate‐containing bis‐silanols which included bis(4‐hydroxydimethylsilylphenyl)‐carbonate, bis[4‐(1‐hydroxy‐1,1,3,3‐tetramethyldisiloxanyl)‐phenyl] carbonate, and their meta analogs. Because conventional siloxane polymerization methods, such as the heterocondensation of bis‐silanols with diaminosilanes or homocondensation reactions catalyzed by alkali reagents, decomposed carbonate linkages, a new polymerization technique that involved the use of phosgene was used. The procedure was both facile and effective in the polymerization of other arylene bis‐silanols.
Kinetic approach to radiation‐induced grafting in the polyethylene‐styrene system. V. The behavior of initiator radicals
Authors: Imai Masahiko 
Published: April 2003

AbstractWith high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) films the grafting reactions were performed by the preirradiation method. By holding the total absorption dose constant irradiation time was varied. The initial rate of grafting decreased with irradiation time. The relative concentration of alkyl radical in the polyethylene film also decreased with irradiation time, but the relative concentration of allyl increased. The differences in the ESR spectrum before and after the introduction of styrene indicate that the allyl‐type radical reacted with styrene. To elucidate these results the allyl radical in the amorphous region was considered.
Kinetics of isothermal degradation of poly vinyl bromide (PVBr). A typical case of “autocatalytic” thermal degradation
Authors: Mazón‐Arechederra J. M. , Quíntero M. P. Delgado , Barrales‐Rienda J. M. 
Published: April 2003

AbstractThe kinetics of thermal degradation of a sample of 46.0% isotactic polyvinyl bromide (PVBr) was studied in a static procedure. An integrated analytical method is presented for the estimation of rate constants. Reaction curves for the formation of hydrogen bromide (HBr) can be interpreted in terms of two concurrent first‐order reactions; namely,
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with activation energies of 29.7 and 40.6 kcal/mol, respectively. The mathematical derivation does not involve an approximation; thus the accuracy of the procedure depends only on the experimentation. Good agreement between calculated and experimentally determined values of a series of characteristic kinetical parameters was obtained. The formation of HBr from PVBr was studied kinetically by a thermogravimetric programmed procedure at room temperature to 700°C. By this method it is possible to determine the activation energy of the stripping process of the main chain without knowing the form of the kinetic equation. The activation energy of 40.1 kcal/mol for the overall process was evaluated by the MacCallum and Tanner method. This dynamic heating developed two distinct temperature regions in which maximum rate loss occurred at characteristic temperatures. The first temperature region was associated with the quantitative evolution of 100% HBr molecules.
New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). XIII. Influence of lewis acid strength and counteranion stability on the synthesis of telechelic polyisobutylenes
Authors: Wondraczek Reinhard H. , Kennedy Joseph P. , Storey Robson F. 
Published: April 2003

AbstractEfforts have been made to prepare perfect terminally functional linear telechelic polyisobutylenes with various Lewis acid coinitiators, BCl3, AlCl3, TiCl4, SnCl4, VCl4, and SbCl5. However, the expected desirable results (F̄n = 2.0, M̄w/M̄n = 1.5) were obtained only with BCl3. Moreover, the concentration of BCl3 affects the molecular weight of telechelic polyisobutylenes prepared by the inifer technique. The Kennedy–Smith inifer mechanism is insufficient to explain these observations. Extending this model by the concept of counteranion stability, of Heublein et al.,5 and assuming the participation of free ions and ion pairs in propagation and termination, led to a satisfactory mechanistic model. The exceptional utility of the BCl3/BCl⊖ system is due to the high Lewis acid strength of BCl3 and low counteranion stability of BCl⊖.
Polymerization photoinitiated by carbonyl compounds. IV. α‐diketones and α‐substituted alkanones
Authors: Encina M. V. , Lissi E. A. , Koch V. , Elorza E. 
Published: April 2003

AbstractThe photoinitiation efficiency of the free‐radical polymerization of methyl methacrylate and styrene by several carbonly compounds has been determined. The compounds considered were α‐substituted ketones and α‐dicarbonyl compounds. For the ketones, the initiation efficiency employing methyl methacrylate depends on the α substitution; the values obtained change from less than 10−3 (acetone) to 0.65 (3‐hydroxy‐3‐methyl‐2‐butanone). All ketones are more efficient towards methyl methacrylate than styrene. This result can be explained in terms of triplet quenching by the last monomer. The results obtained employing α‐dicarbonyl compounds do not conform to a simple pattern. In particular, benzil shows a considerably larger efficiency towards styrene than for methyl methacrylate. Since benzil is efficiently quenched by styrene, the initiation must involve the interaction of an excited benzil molecule and the monomer.
Preparation of polyamides via the phosphorylation reaction. Poly‐4,4′‐benzanilides
Authors: Asrar J. , Preston J. , Krigbaum W. R. 
Published: April 2003

Abstract4,4′‐Diaminobenzanilide (DAB) was reacted with diacids via the Yamazaki phosphorylation reaction to yield simple polyamides and random copolyamides. The use of DAB was found to promote polycondensation because DAB contains a preformed amide linkage which minimizes the amounts of by‐products formed. It also maximizes polymer solubility since the monomer is unsymmetrical. The order of the inherent viscosity values of the polymers obtained from DAB by reaction with different diacids, isophthalic > aliphatic > terephthalic, was found to parallel polymer solubility in the reaction medium. The inherent viscosity of the polyamide based on terephthalic acid, DAB‐T, was increased greatly by copolymerization, isophthalic acid being more effective than an aliphatic diacid in this regard. None of the polymers formed a thermotropic nematic phase, but the copolymer having an equimolar ratio of terephthalic and adipic acid formed anisotropic solutions in 100% sulfuric acid at polymer concentrations exceeding 40%. Strong films were cast from such solutions.
Polymerization of acrylamide initiated by the Ce4+/thiourea redox system
Authors: Misra G. S. , Bhattacharya S. N. 
Published: April 2003

AbstractThe polymerization of acrylamide (M) initiated by the Ce4+/thiourea (TU) redox system has been studied in an aqueous sulfuric acid medium at 35 ± 0.2°C under nitrogen atmosphere. The rate of polymerization is governed by the expression

The activation energy is 5.9 kcal deg−1 mol−1 in the investigated temperature range 30–50°C. The molecular weight is directly proportional to the concentration of monomer and inversely proportional to the catalyst concentration. With increasing concentration of DMF molecular weight decreases. The range of concentrations for which these observations hold at sulfuric acid concentration of 2.5 × 10−2 mol/L are [monomer] = 5.0 × 10−2–3.0 × 10−1, [catalyst] = (5.0–15.0) × 10−4, and [activator] = (1.0–6.0) × 10−3 mol/L.
Initiation of the stereospecific polymerization of p‐chlorophenylglycidyl and phenylglycidyl ethers by the Al(OiPr)3 + ZnEt2 (1:1) initiator system
Authors: Bero M. 
Published: April 2003

AbstractThe Al(OiPr)3 + ZnEt2 (1:1) system has been found to be an efficient initiator of the polymerization of phenylglycidyl ethers. About 40–60% of the polymer obtained was an isotactic polymer fraction (ca. 80% of iso diads). By using aluminum isopropoxide containing C14, the amount of linear polymer molecules terminated by isopropoxide groups was shown not to exceed 50%. IR spectrophotometric studies of the structure of the initiator system showed that its components form a complex compound by an exchange of substituents between the aluminum and zinc atoms.
Comments on “(A) critical examination of the dissociation‐association phenomena in the hexane solution of lithium polyisoprenyl” by M. Szwarc
Authors: Fetters L. J. , Morton M. 
Published: April 2003

AbstractA note has appeared which seeks to question work from these laboratories (which appeared in 1964). The author of this recent paper attempts to demonstrate that the ΔH and ΔS values, based on our results, for the dissociation of the polyisoprenyllithium dimer “have no meaning.” This assessment ignores information in the literature. For similar reasons, other claims by the author of this recent paper are shown to be subject to scrutiny.