bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of molecular weight of the donor polymer on the solid‐state behavior of interchain EDA complexes
Authors: Pugh Coleen , Rodriguez‐Parada Jose M. , Percec Virgil 
Published: April 2003

AbstractN‐(2‐hydroxyethyl)carbazolyl methacrylate (HECM) and N‐ethyl‐3‐hydroxymethyl carbazolyl methacrylate (HMCM‐2) were polymerized by group transfer polymerization to varying molecular weights of somewhat narrow molecular weight distribution. The thermal behavior of the homopolymers and of their EDA complexes with poly(β‐hydroxyethyl‐3,5‐dinitrobenzoyl methacrylate) (PDNBM‐2) was studied as a function of molecular weight. The Tg′s of both polymers and their miscible complexes increase steadily as molecular weight increases and then become constant at about Mn = 6000. Both the PHECM–PDNBM‐2 and PHMCM‐2—PDNBM‐2 systems are thermally reversible miscible networks over all polymer molecular weights. Miscibility is thermodynamically controlled over the entire range of molecular weights in the first system and decomplexation does not occur below the decomposition temperature. However, miscibility is thermodynamically controlled in the second system when the molecular weight of PHMCM‐2 is less than 5000, and kinetically controlled for higher molecular weights. The decomplexation temperature or LCST of the PHMCM‐2–PDNBM‐2 system occurs below the decomposition temperature and increases with decreasing PHMCM‐2 molecular weight, in agreement with theoretical predictions on the dependence of LCST on polymer molecular weight.
Polymerization of 1‐bromo‐2‐phenylacetylene
Authors: Trumbo D. L. , Marvel C. S. 
Published: April 2003

AbstractThe title monomer was polymerized by thermal initiation and the polymers were analyzed by IR, NMR, and GPC. The polymers were found to be low molecular weight species that had eliminated bromine as the polymerization progressed. In addition, initiation with AIBN was attempted, however, no difference in rate of polymerization, percent conversion, or molecular weight was noted between these polymers and those synthesized by thermal initiation. Also, no initiator fragments were found in the polymers.
Preparation and properties of azopolyimides‐I
Authors: Padma S. , Mahadevan V. , Srinivasan M. 
Published: April 2003

AbstractA new class of aromatic and heterocyclic polyimides were synthesized from benzothiazoleamines benzidine, 4,4′‐diaminodiphenyl ethane and 4,4′‐diamino diphenyl sulfone with 4,4′‐azodipthalic anhydride and/or pyromellitic dianhydride. The synthesis involved the reaction of the dianhydride with the respective diamine to yield an intermediate, soluble, open chain precursor polymer, the polyamic acid, which on cyclodehydration yielded the less soluble, heat resistant polyimides. All these polyimides were characterized by IR and NMR. Solubility, density, viscosity, and thermal stability of these polymers were also studied.
Photosensitized polymerizations of some vinyl monomers using aliphatic carbonyl polymers as initiators
Authors: Naito I. , Ueki T. , Tabara S. , Tomiki M. , Kinoshita A. 
Published: April 2003

AbstractApplications of poly(4,4‐dimethyl‐1‐penten‐3‐one) (PBVK) and poly(3‐methyl‐3‐buen‐2‐one) (PMIK) as initiators for UV curing were studied. The triplet state of PBVK was quenched by monomers but its rate was small compared with the low molecular model compound, 3,3‐dimethyl‐2‐butanone. The α‐cleavage quantum yield of PBVK was estimated to be ca. 0.5. The graft efficiencies of the resulting polymers were 0.5. The sensitivity of PBVK is greater than benzoin methyl ether under 313 nm of irradiation.
Synthesis of poly(benzoxazole)s by direct polycondensation of dicarboxylic acids with 3,3′‐dihydroxybenzidine dihydrochloride using phosphorus pentoxide/methanesulfonic acid as condensing agent and solvent
Authors: Ueda Mitsuru , Sugita Hiroya , Sato Masaki 
Published: April 2003

AbstractA convenient method for the synthesis of poly(benzoxazole)s of high molecular weights has been developed. These polymers were prepared readily by direct polycondensation of aromatic dicarboxylic acids containing phenyl either structure with 3,3′‐dihydroxybenzidine dihydrochloride using phosphorus pentoxide/methanesulfonic acid (PPMA) as condensing agent and solvent. Polycondensations proceeded fast and was completed within 5 h at 140°C and produced poly(benzoxazole)s with inherent viscosities up to 4.6 dL/g. Model compound work was performed in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(benzoxazole)s showed 10% weight loss in air and nitrogen at 450–505°C and 465–535°C, respectively.
Termination‐rate coefficients in methyl methacrylate polymerizations
Authors: Ballard Mathew J. , Napper Donald H. , Gilbert Robert G. , Sangster David F. 
Published: April 2003

AbstractIt is shown that, by observing the kinetics of the seeded emulsion polymerization of methyl methacrylate with and without added chain‐transfer agent, and using γ‐radiolytic initiation, it is possible to examine separately the effects of the length of the growing chain and of the weight fraction of polymer on the termination rate coefficient. Studies using this technique confirm predictions that chain entanglement causes translational diffusion to be the rate‐determining termination event for growing chains of lower molecular weight, while the rate‐determining termination event for growing chains of higher molecular weight is “residual,” the annihilation encounter being caused by excess chain end mobility of two growing chains in a viscous medium. The data show unambiguously that free‐volume theories which do not incorporate the molecular weight of the growing chain are inapplicable to this system.
Thermally stable polymers based on addition‐type imidobenzoxazoles; synthesis and characterization of polybismaleimidobenzoxazoles and polybiscitraconimidobenzoxazoles
Authors: Nair C. P. Reghunadhan , Sebastian T. V. , Nema S. K. , Rao K. V. C. 
Published: April 2003

AbstractFour structurally different bisimidobenzoxazole monomers were synthesized, based on the reaction of two isomeric diaminobenzoxazoles, viz., 5‐amino‐2‐(p‐aminophenyl) benzoxazole and 5‐amino‐2‐(m‐aminophenyl) benzoxazole with maleic and citraconic anhydrides. The diamines were synthesized by a new route. The imides and the amic intermediates were characterized by elemental analysis, IR, NMR, and mass spectra. The imides could be thermally polymerized to crosslinked brittle polybisimidobenzoxazoles. The citraconimides polymerized at a lower temperature than the maleimide. Thermal stability of the cured resins was evaluated by TGA and was correlated to the structure of the polyimide. The polybismaleimidobenzoxazoles were stable up to about 500°C in N2, leaving 50–60% anaerobic char yield at 800°C, whereas polybiscitraconimidobenzoxazoles were stable up to 420°C. Comparison of the thermal behavior of similar polyimides based on oxydianiline revealed that incorporation of benzoxazole structure enhances the decomposition temperature, lowers the rate of decomposition, and enhances the anaerobic char yield at high temperature. Addition of diamines as chain‐extending agents decreased the thermal stability of the resins without any change in the anaerobic char yield.
Asymmetric induction copolymerization of optically active N‐(l‐menthyl carboxylatomethyl)citraconimide with styrene
Authors: Oishi Tsutomu , Okamoto Nobushige , Fujimoto Minoru 
Published: April 2003

AbstractA novel, optically active N‐(l‐menthyl carboxylatomethyl)citraconimide (MCMCI) was prepared from citraconic anhydride, glycine, and l‐menthol. The polymerization of MCMCI with styrene (ST) was carried out in benzene with azobisisobutyronitrile (AIBN) as initiator to give optically active copolymers. After the removal of the optically active menthyl group by hydrolysis with potassium hydroxide, the ester‐cloven poly(MCMCI‐co‐ST)s still showed optical activity. It is thought that an asymmetric induction took place in the polymer main chains. The asymmetric induction is discussed based on the measurements of the optical rotatory dispersion and circular dichroism of the original and hydrolyzed copolymers.
Epoxidation of bromostyrene – butadiene cotelomers
Authors: Naé H. N. , Coldman M. , Vofsi D. 
Published: April 2003

AbstractThe synthesis of low‐molecular‐weight copolymers of bromostyrenes and butadiene and their epoxidation is discussed. The copolymers contain in the same molecule an elastomeric part, a flame‐retardant part, and epoxy groups. Two epoxidation routes were studied: by an in situ generated peracid and by m‐chloroperbenzoic acid. The latter is preferred, but limited to about 40% epoxidation. Epoxidation occurs mainly at the 1,4 structure of the butadiene segments. The cure of these copolymers with a tetra functional epoxy resin and diaminodiphenyl sulfone is discussed. The epoxides and their cured systems are thermally stable.
Growth of carbonyl index in the degradation of polypropylene by UV irradiation
Authors: Subowo Wiwik S. , Barmawi M. , Liang Oei Ban 
Published: April 2003

AbstractThe growth of the carbonyl index in the degradation of polypropylene by UV irradiation, with and without UV stabilizer, has been measured and interpreted. From the kinetics of the degradation process the mathematical expression of the growth of the carbonyl index was derived using the steady‐state treatment for short‐lived intermediates, except for the alkyl radical P. For polypropylene without UV stabilizer and for polypropylene with UV absorber or excited‐state quencher, the growth of the carbonyl index was related to UV irradiation time by X = Aeλ1t + Beλ2t. While in the presence of an antioxidant or radical scavenger, the general form was X = Aeλ1t + Beλ2t + C. The values of A, B, λ1, λ2, and C were obtained by fitting the experimental data into the equation. It was found that the error was about 15%.
Synthesis and characterization of aromatic polyesteres and polyamide–esters from bisphenols and aromatic aminophenols, and 2,5‐bis(4‐chloroformyl)‐3,4‐diphenylthiophene
Authors: Kakimoto Masa‐Aki , Negi Yuvraj Singh , Imai Yoshio 
Published: April 2003

AbstractPolycondensation of 2,5‐bis(4‐chloroformyl)‐3,4‐diphenylthiophene (I) with various bisphenols afforded tetraphenylthiophene‐containing aromatic polyesters by the interfacial or solution polycondensation method. Polyamide–esters were obtained from I and aminophenols by means of the interfacial technique. These polymers had inherent viscosities of 0.4–0.8 dL/g. All the polymers were readily soluble in various organic solvents, and could be cast into transparent and flexible films. Their glass transition temperatures were in the range of 235–335°C. These polymers did not lose weight below 400°C in either air or nitrogen.
Cyclopolymerization of (E,E) ‐ [6.2]paracyclophane‐1,5‐diene
Authors: Longone Daniel T. , Glatzhofer Daniel T. 
Published: April 2003

AbstractPolymerization of (E,E)‐[6.2]paracyclophane‐1,5‐diene proceeds by an intra–intermolecular mechanism to give a polymer containing a [3.2]paracyclophane in the repeat unit. Polymerization occurs with either free radical or cationic initiation; anionic initiation was unsuccessful. Cationic polymerization is favored and appears to proceed through a stabilized carbonium ion intermediate. Spectroscopic and model compound studies are consistent with the proposed polymer structure. Thermal analyses of the polymer indicate a complex thermooxidative behavior in the presence of oxygen, while depolymerization occurs above about 400°C in an inert atmosphere.
Magnesium chloride supported high‐mileage catalyst for olefin polymerization. IX. Molecular weight and distribution and chain‐transfer processes
Authors: Chien James C. W. , Kuo Chi‐I. 
Published: April 2003

AbstractMn, Mw and PD = Mw/Mn of polypropylene obtained with the MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4–AlEt3/methyl‐p‐toluate (CW‐catalyst) have been obtained as a function of temperature, monomer, and AlEt3 concentrations. The values of Mn after a few minutes of polymerization range from 50% to 100% of the final values. I.I. (percent yield of stereoregular polymer) and P.D. of stereoregular polymer remain constant during a batch polymerization. The MW distribution is very narrow with PD ⋍ 2.0 between 0° and 50° using optimum A/T ratio. It is broader for polymerizations employing low or high A/T ratio or elevated temperature, reaching P.D. = 2.78 at 70°C. The corresponding P.D. values for the total polymer ranged from 3.1 to 4.5 due to contributions from the heptane soluble fraction. The latter gives bimodal GPC chromatogram. The Mn of stereoregular polymer is much smaller than the reciprocal of concentration of metal polymer bonds, [MPB]−1; the ratio of the two quantities is a measure of number of polymer chains not bonded to a metal ion to the number of those which are bonded to either Ti or Al. Depending upon the experimental conditions, this ratio varied from 2.3 to 23.5 for short polymerization time, and 16 to 31 for long polymerization time.Chain transfer with AlEt3 is ineffective for the CW‐catalyst system. From the plots of [MPB] versus yield, the rate constants for this process obtained at 50° are: k = 2.1 × 10−4 sec−1; k = 2 × 10−5 sec−1; k = 1.1 × 10−4 sec−1; and k = 1.2 × 10−5 sec−1 where the subscripts i, a, 1 and 2 refer to stereospecific and nonstereospecific sites of first and second kind respectively. Thr transfer rates increase with both increasing and decreasing temperatures consistent with the Langmuir–Hirschelwood adsorption model.The MW of isotactic polymers are dependent upon monomer concentration. The chain transfer with monomer has rate constants at 50° of k = 1.34 × 10−2 M−1 sec−1 and k = 1.2 × 10−3 M−1 sec−1. In addition there is chain transfer by β‐hydride elimination with k = 2.7 × 10−2 sec−1 at 50° which is the chain lifetime limiting process at low monomer concentration. The rate of chain transfer with monomer can exceed that of β‐hydride elimination at high propylene pressure.The very narrow PD for the stereoregular polymers suggest there is only one chemically distinct isospecific active site.
Synthesis, polymerization, and copolymerization of multimethacrylate in matrix of poly(vinyl alcohol)
Authors: Jantas R. , Połowiǹski S. 
Published: April 2003

AbstractBy reacting poly(vinyl alcohol) (PVA) with methacryloyl chloride, multimethacrylate in PVA matrix has been obtained. Free‐radical polymerization of multimethacrylate and copolymerization of two multimethacrylates in PVA and p‐cresol‐formaldehyde matrices in diluted solutions occurs probably along ordered methyl methacrylate units in the matrix and results mainly in ladder‐type homopolymer and copolymer. The structures of multimethacrylate, homopolymer, and copolymer have been found on the basis of elemental analysis, IR, and 1H NMR spectra, and examination of the products of hydrolysis.
Polymerization of vinyl monomers initiated by organoaluminium compounds/benzoyl peroxide systems
Authors: Florjanczyk Zbigniew , Siudakiewicz Marek 
Published: April 2003

AbstractThe free‐radical polymerization of methyl methacrylate (MMA) initiated by systems comprizing benzoyl peroxide (BPO) and different organoaluminium compounds (OACs) has been studied. The influence of the type of OAC, concentration of components of the initiation system, temperature, and time on the reaction yield have been determined. Systems containing BPO and diethylaluminium chloride (Et2AlCl) have been found to enable us to obtain, in high yields at room temperature, of homopolymers of MMA, methyl acrylate, acrylonitrile (AN), vinyl acetate, and the alternating AN/styrene (St) copolymer; they are, however, not very active in the homopolymerization of St and vinyl chloride. Factors affecting the polymerization yield have been discussed in terms of the mechanism of the reaction between BPO and OACs, reactivity of alkyl radicals formed in these systems, and catalytic effect of OAC in the propagation step.
Synthesis of polyurea by direct polycondensation of 4‐aminophenyl ether with lithium carbonate
Authors: Kosaka Yohzou , Watanabe Masayoshi , Sanui Kohei , Ogata Naoya 
Published: April 2003

AbstractPolyureas of high molecular weight were obtained by the direct polycondensation of 4‐aminophenyl ether with lithium carbonate in the presence of triphenylphosphine (Ph3P), hexachloroethane (C2Cl6), and pyridine. Reaction conditions, such as the molar ratios of Ph3P and C2Cl6 to the monomers, monomer concentrations, reaction temperatures, reaction times, and kind of solvents, had a significant effect on the yield and the molecular weight of the resulting polyureas. The polyurea having the highest solution viscosity of 0.91 dL/g was obtained with the molar ratio of Ph3P/C2Cl6/monomers = 2.4/2/1 in the mixed solvent of N‐methyl‐2‐pyrrolidone and pyridine at 80°C.
FT‐IR study of the stabilization reaction of polyacrylonitrile in the production of carbon fibers
Authors: Shimada I. , Takahagi T. , Fukuhara M. , Morita K. , Ishitani A. 
Published: April 2003

AbstractThe stabilized fibers prepared by heating PAN and a PAN copolymer in air and under reduced pressure have been examined by FT‐IR spectroscopy in order to determine their chemical structures. Three kinds of reactions, cyclization, dehydrogenation, and oxygen uptake are found to occur almost simultaneously in the stabilization process in air by digital difference spectrum method. The effect of the comonomer is confirmed to accelate the dehydrogenation reaction and also the formation of acridone ring in the thermal stabilization in air by kinetic study.
Lyotropic mesophase of cellulose in ammonia/ammonium thiocyanate solution
Authors: Chen Yue‐Shen , Cuculo John A. 
Published: April 2003

AbstractSolutions of cellulose in a mixture of 27:73 (w/w) of liquid ammonia and ammonium thiocyanate become liquid crystalline at room temperature above a certain critical concentration which depends on the degree of polymerization of the dissolved cellulose. The high optical rotations of the solution suggest that the cellulose mesophase is cholesteric in nature. In the two‐phase region, the cellulose solutions exhibit negatively birefringent spherulites that possess both ringed and nonringed internal structures. The anisotropic solutions can be oriented by shear, indicating high potential for spinning them into useful fibers.
Resolution of wide‐angle x‐ray scattering from a thermoplastic composite
Authors: Wakelyn N. T. 
Published: April 2003

AbstractWide‐angle x‐ray scattering from a polyetheretherketone/carbonaceous fiber composite has been resolved using a curve‐fit procedure. This resolution yielded under curve areas for crystalline, amorphous, and fiber scatter which could be used as the basis for an estimation of crystallinity.
The crosslinking of epoxy resins at interfaces. III. At a carbonized polyacrylonitrile surface
Authors: Garton Andrew , Daly John H. , Stevenson William T. K. , Wiles David M. 
Published: April 2003

AbstractThe crosslinking chemistry of an anhydride‐cured epoxy resin, in the first 200–400 nm adjacent to a carbonized polyacrylonitrile (PAN) surface (a model for the surface of a carbon fiber), is significantly affected by the humidity history of that surface. Prior humid aging of the carbonized PAN surface increases the subsequent rate of consumption of anhydride curing agent, and decreases the yield of ester crosslinked products. The crosslinking chemistry of an amine‐cured epoxy resin appears unchanged by the presence of the carbonized surface. Dynamic mechanical analysis (DMA) of unidirectional composites made from carbon fibers and the above epoxy resin matrices shows that the damping characteristics of composites made with an epoxy–anhydride matrix are sensitive to the preconditioning history of the carbon fibers, while composites made with an epoxy–amine matrix are unaffected by the preconditioning history of the fibers. Partial removal of the carbon fiber surface coating by dichloromethane extraction does not change the sensitivity of the composites to fiber preconditioning history. These results are rationalized on the basis of the effect moisture adsorbed by the carbonized PAN and by the carbon fiber has on the epoxy resin crosslinking processes.
Retardation of radical polymerization rate by phenoxy radical produced from T‐butylperoxy phenylcarbonate
Authors: Matsuyama Kazuo , Komai Takeshi , Ito Katsukiyo 
Published: April 2003

AbstractT‐butylperoxy phenylcarbonate (BPPC) was prepared. Its decomposition rate constant in cumene is given by kd = 2.39 × 1015 exp(−17,300/T), where T is the absolute temperature. When BPPC decomposes to polymerize styrene at 100°C, it produces 12% phenoxy radical to total primary radicals. The phenoxy radical hardly adds to styrene and reacts the other primary radicals and polymer radical. Thus it retards the rate of polymerization.
Ozonation of hydrocarbon diene elastomers: A mechanistic study
Authors: Ho K. W. 
Published: April 2003

AbstractA study of the effects of ozonation on polybutadiene, polyisoprene, and several related hydrocarbon elastomers has shown that elastomers containing di‐substituted double bonds (e.g., cis‐1,4‐polybutadiene) give crosslinked products as well as chain scission products in nonpolar solvents, whereas those containing tri‐substituted double bonds (e.g., cis‐1,4‐polyisoprene) give chain scission products only. Both types of elastomer, however, give only chain scission products in polar solvents. Further investigation of the ozonation of elastomers, including the effect of ozonides of monoolefins and the solvent effect has led us to postulate that the chain scission involves the attack of a second ozone molecule on the preformed ozonide, and, the crosslinking is due to the attack of the biradical carbonyl oxide on the rubber.
Magnesium chloride supported high mileage catalysts for olefin polymerization. XII. Polymerization of ethylene
Authors: Chien James C. W. , Bres Phillipe L. 
Published: April 2003

AbstractPolymerizations of ethylene by the MgCl2/ethylbenzoate/p‐cresol/AlEt3 TiCl4‐AlEt3/methyl‐p‐toluate (CW‐catalyst) have been studied. The initially formed active site concentration, [Ti] has a maximum value of 50% of total titanium at 50°C and lower values at other temperatures. The Ti decays rapidly to Ti sites with conc. ca. 10 mol %/mol Ti. The rate constants for four chain transfer processes have been obtained at 50°C: for transfer with AlEt3, k = 2.1 × 10−4 s−1 and k = 4.8 × 10−4 s−1; for transfer with monomer, k = 3.6 × 10−3 (M s)−1 and K = 8.3 × 10−3 (M s)−1; for β‐hydride transfer, k = 7.2 × 10−4 s−1 and k = 4.9 × 10−4 s−1; and transfer with hydrogen, k = 4.0 × 10−3 torr1/2 s− and k = 5.1 × 10−3 torr1/2 s−1. The rate constants for the termination assisted by hydrogen is k = 1.7 (M1/2 torr1/2 S)−1. If monomer is assisting termination as was observed for propylene polymerization, then k = 7.8 (M3/2 s)−1. Values of all the rate constants can be higher or lower at other temperatures. Detailed comparisons were made with the results of propylene polymerizations. There are more than four times as many Ti active sites for ethylene polymerization than there are for stereospecific polymerization of propylene; the difference is more than a factor of two for the Ti sites. Certain rate constants are nearly the same for both monomers while others are markedly different. Some of the differences can be explained by stereoelectronic effects.