bluuebunny/crossref_metadata_2025 huggingface dataset:
A 13C‐NMR spectral study of cellulose and glucopyranose dissolved in the NH3/NH4SCN solvent system
Authors: Degroot A. W. , Carroll F. I. , Cuculo J. A.
Published: April 2003

The 13C‐NMR chemical shifts of a cellulose with a DPw of 23 dissolved in the NH3/NH4SCN solvent system were found to be very similar to those of cellulose dissolved in DMSO (cellulose oligomers), in the LiCl/DMAC system and in the N‐methylmorpholine N‐oxide/DMSO system. It was concluded from this that cellulose does not react with the NH3/NH4SCN solvent. It was found, however, that glucose reacts with the solvent at C‐1 to form β‐D‐glucopyranosy‐lamine. Separation of this compound from the solvent resulted in another compound which was determined to be β,β‐di‐D‐glucopyranosylamine. The compounds β‐D‐glucopyranosylamine, N‐acetyl‐2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosylamine, β,β‐di‐D‐glucopyranosylamine, α,β‐di‐D‐glucopyranosylamine, 2,3,4,6,2′,3′,4′,6′‐octa‐O‐acetyl‐α,β‐di‐D‐glucopyranosylamine were all synthesized and the 13C‐NMR chemical shifts of these compounds are reported. It was also found that for the low‐DP cellulose sample which was used the reducing end group existed and had reacted with the solvent to form an amine at C‐1.
Plasma polymerization of phenyl isothiocyanate
Authors: Czeremuszkin G. , Wróbel A. M. , Kryszewski M.
Published: April 2003

Thin polymer films were obtained by plasma polymerization of phenyl isothiocyanate. Polymerizations were carried out in rf (13.56 MHz) glow discharge generated in an electrodeless flow system. It was found that this monomer produces uniform films with a wide range of thicknesses, from hundreds of nanometers to tens of micrometers. The deposition rate appeared to be dependent on the substrate distance from the monomer inlet. The chemical structure of plasma polymer was characterized by using elemental analysis, IR spectroscopy, gas chromatography, and mass spectrometry. Elemental analysis showed that the composition of polymer depends on the substrate position in the reactor. It was observed that sulphur content decreased with increasing the substrate distance from the monomer inlet, whereas nitrogen content appeared to increase. The IR data revealed significant decrease in —NCS groups content in the polymer as compared with the monomer spectrum and indicated for the appearance of new absorption bands corresponding to the CN and CH aliphatic, groups. The results account for a strong fragmentation of monomer in plasma involved in decomposition of isothiocyanate group and phenyl ring. The soluble fraction of polymeric material was examined by gas chromatography and then the separated products were analyzed by mass spectrometry. The soluble fraction was found to be composed of numerous low molecular‐weight compounds. Identification of their structure revealed the presence of residual monomer, thiophenol, cyanobenzene, diphenyl, diphenyl sulphide, diphenyl disulphide, phenyl thiocyanate, dicyanobenzene, phenatroline, and some other oligomeric products. Formation of these compounds proves high susceptibility of NCS group in the monomer towards different fragmentation reactions. The surface free energy and electrical conductivity of polymer films were evaluated. The surface free energy value was very close to those estimated for plasma polymers deposited from other benzene derivatives. The low electrical conductivity manifested by the investigated polymeric material indicated for its dielectric character. The photoelectrical measurements revealed some photoconductivity effect in this material.
An ESCA study of chemical reactions on the surfaces of cellulose fibers
Authors: Zadorecki Pawel , Rönnhult Tore
Published: April 2003

Cellulose fibers in the form of paper sheets were chemically modified with different functional groups using trichloro‐s‐triazine as coupling moiety. The treatments made the paper surfaces hydrophobic, as was indicated by an increase in contact angle against water. ESCA was used for the chemical characterization of the paper surfaces. The shape of the carbon 1s peak depended on the chemical functionality of the triazine derivatives. As a reference, ESCA spectra were also recorded for the triazine derivatives precipitated on aluminum plates. The chemical composition of modified cellulose surfaces could then be determined using a computer program for the peak separation and peak area measurement.
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

N‐(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

The 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

A 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

Applications 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

A 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

It 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

Four 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

A 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

The 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

The 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

Polycondensation 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

Polymerization 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

Mn, 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

By 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

The 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

Polyureas 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

The 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

Solutions 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

Wide‐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

The 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

T‐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

A 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

Polymerizations 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.
High conversion free‐radical suspension polymerization: End groups in poly(methyl methacrylate) and their influence on the thermal stability
Authors: Giannetti Enzo , Mazzocchi Romano , Fiore Leonardo , Visani Francesco
Published: April 2003

Suspension free‐radical polymerization of vinyl monomers, carried out in the presence of alkyl mercaptans as chain‐transfer agents, is analyzed. A model which accounts for the development with conversion of the polymer weight fractions having particularly tagged end groups, namely sulfur‐containing and unsaturated end groups, is presented. The best current theories for diffusion‐controlled polymerizations are included in the model. The sulfur content of poly(methyl methacrylate), determined as a function of conversion by a microcoulometric method, is in good agreement with the values predicted from polymerization kinetics. The rate of weight loss of the produced polymers is then related to the content of the unsaturated end groups. By comparing experimental thermal stability indexes (from thermogravimetry and isothermal heating experiments) to calculated polymer weight fractions, it is shown that the thermal stability of poly(methyl methacrylate) produced in the presence of alkyl mercaptans approximately depends on the square of the weight fraction of the polymer chains with an unsaturated end group.
Isomeric bismaleimides and polyaspartimides
Authors: Bell Vernon L. , Young Philip R.
Published: April 2003

A study was conducted of the effects of meta‐para isomerism on the synthesis and properties of aromatic bismaleimides and polyaspartimides. Three isomers, 3,3′‐, 3,4′‐, and 4,4′‐diaminodiphenylmethanes (methylenedianilines), were used to prepare three isomeric bismaleimides. The bismaleimides then were reacted with their respective isomeric diamines in m‐cresol solution to give a series of isomeric polyaspartimides. The properties of each of the isomeric series were measured and compared. Strong flexible films were solvent cast from the two polyaspartimides derived from the 3,4′‐ and 4,4′‐diamines and their respective bismaleimides. Tensile properties of the films from the 3,4′‐diamine/3,4′‐bismaleimide combination polyaspartimide were equivalent to those from the 4,4′‐diamine‐derived polymer. That finding, together with that polymer's lower softening temperature and the nonmutagenic nature of the 3,4′‐diamine monomer, suggested a potential usefulness for 3,4′‐diaminodiphenylmethane as a replacement for 4,4′‐diaminodiphenylmethane in addition polyimides.
Magnesium chloride supported high‐mileage catalysts for olefin polymerization. X. Effect of hydrogen and catalytic site deactivation
Authors: Chien James C. W. , Kuo Chi‐I.
Published: April 2003

The effect of H2on propylene polymerization initiated by a MgCl2/EB/PC/AlEt3/TiCl4–3 AlEt3/MPT catalyst was studied. Hydrogen increases significantly the initial rate during the early stage of the polymerization to give a higher yield of polymer than reactions without H2. But H2reduces the yield toward the latter stages so that the net effect on the total yield can be quite small. There is no appreciable effect of H2on either the isotacticity index or polydispersity of the products. It decreases molecular weight proportional to (pH2)1/2. The chain transfer by H2resulted in a decrease of total metal polymer bond concentration with time of polymerization. The rate constants of hydrogen chain transfer for the two kinds of isospecific and nonspecific sites are= 5.1 × 10−3,= 2.7 × 10−3,= 7.5 × 10−3,= 4.4 × 10−3, in units of torr1/2sec−1at 50°. Hydrogen assists in the deactivation of the catalytic sites as does propylene; rates of the former and the latter vary with (pH2)1/2and [C3H6]1/2, respectively, withk= (12.1 ± 0.9) M−1torr−1/2sec−1andk= (65.3 ± 3.3) M−3/2sec−1at 50° andA/T= 167. The mechanism for deactivation of catalytic sites are discussed.
Dye‐sensitized photopolymerization. III. Photopolymerization of methyl methacrylate initiated by acryflavin: Ascorbic acid system in aqueous solution
Authors: Lenka Subasini , Mohanty Indu B.
Published: April 2003

The dye‐sensitized photopolymerization of methyl methacrylate by acryflavin–ascorbic acid system in aqueous solution has been investigated. The systems were buffered with phosphate–citrate buffer (Na2HPO4, citrid acid) and the effects of monomer, dye, temperature, buffer, ascorbic acid, etc. on the rate of polymerization were studied. The rate of polymerization was evaluated gravimetrically. A suitable kinetic scheme was proposed and the composite rate constants were evaluated.
Infrared spectroscopic analysis of poly(methyl acrylate‐co‐styrene)
Authors: Kandil S. H. , El‐Gamal M. A.
Published: April 2003

Methyl acrylate–styrene copolymers of different copolymer compositions were free‐radically prepared. The relative intensities of the carbonyl frequencies of the methyl acrylate units atv1730 cm−1were correlated with the copolymer composition. The positions and shapes of the carbonyl bands in the infrared absorption spectra of the copolymers‐dissolved in chloroform, were shown to depend on the composition of the copolymers and upon the presence of different proportions of methyl acrylate centered triads. The results obtained by infrared spectroscopy were compared with those obtained by13C‐NMR. Infrared spectra may be used to yield information about both the copolymer composition and the triad sequence distribution.
Potentiometric and viscosimetric titration of poly(N‐acyldehydroalanines) containing asymmetric nucleic acid base derivatives as pendant groups
Authors: Brandt K. A. , Overberger C. G.
Published: April 2003

The potentiometric and viscosimetric titration curves of poly(N‐acetyldehydroalanine) (PNAcDHA) were compared with those of the nucleic acid base‐containing dehydroalanine backbone polymers poly{(+ −) and (−)− [2‐(thymin‐1‐yl]{propanoamido}propenoic acid} (PTDHA and P(−)TDHA)). The behavior of PNAcDHA was similar to polyacids such as poly(acrylic acid), but PTDHA and P(−)TDHA displayed very strong nearest neighbor interactions, since the pH curves had an additional inflection at half neutralization that was sensitive to the ionic strength of the medium and the viscosity curves showed little expansion of the polymer coil with increasing ionization. NAcDHA–TDHA copolymers were prepared which showed similar behavior. These results suggested that PTDHA and P(−)TDHA were extended and conformationally restricted in aqueous solution compared to PNAcDHA, findings that agreed with the results of spectroscopic studies of these polymers.
Poly(methyl methacrylate‐g‐urethane). I. Synthesis
Authors: Akcelrud L. , Gomes A. S.
Published: April 2003

Poly(methyl methacrylate‐g‐urethane) was prepared by coupling between poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) and polyurethane. The polyurethane was obtained by bulk polycondensation of tolylene diisocyanate and polypropylene glycol. The two polymeric species were synthesized and characterized separately, and the composition of the grafted products varied only by the spacing of the grafted segments. Grafted copolymers with 5, 10, 20, 25, 40, 50, 70, and 90% of incorporated polyurethane have been prepared.
Production of anomalous particles in the process of emulsifier‐free emulsion copolymerization of styrene and 2‐hydroxyethyl methacrylate
Authors: Kamei Shigeru , Okubo Masayoshi , Matsumoto Tsunetaka
Published: April 2003

It was found that copolymer particles produced by emulsifier‐free emulsion copolymerization of styrene and 2‐hydroxyethyl methacrylate had an anomalous shape with uneven surface. The formation mechanism is discussed.
Synthesis of poly(arylene sulfide)s by reaction of aromatic sulfides with AlCl3
Authors: Sergeyev Vladimir A. , Nedelkin Vladimir I.
Published: April 2003

Methods have been developed to obtain poly(arylene sulfide)s by high‐temperature bulk polycondensation of diphenyl sulfide, cyclic aromatic sulfides, as well as direct reaction of benzene with sulfur, under the action of AlCl3. The reaction proceeds via the formation of colored cation‐radical complexes of aromatic sulfides with AlCl3 and results in polymers of ladder structure with, predominantly, thianthrene units in the chain. Taking linear poly(1,4‐phenylene sulfide) as an example, AlCl3 is shown not only to act as a catalyst but also to exert an active influence on the chemical structure of the polymer.
Non‐newtonian viscosity of polypeptides in the helix–coil transition region
Authors: Jang Chun Hag , Kim Jong Ryul , Ree Taikyue
Published: April 2003

The non‐Newtonian intrinsic viscosities [η] of poly(γ‐methyl L‐glutamate) were measured in the helix–coil transition region under various conditions in this work. The helix content fH, which represents the degree of conformational transition, was obtained by using a polarimeter. Our experimental results show that the non‐Newtonian behavior of the polypeptide is markedly affected by its conformation; i.e., the non‐Newtonian effect becomes larger as fH increases. The effect of external pressure ΔP on [η] was studied carefully; [η] increases with fH when ΔP < 1.5 psi, but it decreases when ΔP > 1.5 psi and fH > 0.8. The reason for this result is considered in the text.
Spectroscopic studies of poly(ethylenimine) backbone polynucleotide analogs
Authors: Overberger C. G. , Peng Lin
Published: April 2003

The hypochromicity of poly(ethylene glycol methyl ether)‐b‐poly(ethylenimine) containing thymine derivatives as pendants was observed in water, 0.1N HCl and 0.1N NaOH solutions. The hypochromic effect of this compound is between 30% and 40%. Interactions between this polynucleotide analog and poly‐A was only found in water but not in 0.1N HCl or 0.1N NaOH solution.
Functional monomers and polymers. CXXXII. Template polymerization of methacrylamide derivatives containing nucleic acid bases
Authors: Inaki Yoshiaki , Ebisutani Kazushi , Takemoto Kiichi
Published: April 2003

Free‐radical polymerizations of methacrylamide derivatives containing nucleic acid bases were studied in the presence of the polymethacrylamide having complementary nucleic acid bases as template polymers. The rate of the polymerization did not show remarkable difference in the presence or the absence of the template polymer. A stable polymer complex, however, was precipitated from the polymerization system, and was found to be different in a thermal analysis from the polymer complex which was obtained by mixing of the complementary polymers in solution. Free‐radical copolymerizations in the presence of the template polymers also supported the template polymerization.
Gas separation membranes plasma‐polymerized from perfluoromethylcyclohexane/methane mixture
Authors: Inagaki N. , Kawai H.
Published: April 2003

Plasma‐polymerizations of perfluoromethylcyclohexane (PFMCH)/methane (CH4) mixture were investigated by elemental analysis, infrared spectroscopy, and ESCA; and gas transport characteristics of the plasma‐films formed were studied. The addition of CH4 molecules to PFMCH accelerated defluorination to form plasma‐polymers poor in fluorocarbon units. The surface energy of the plasma‐polymers increased with increasing the CH4 concentration. The oxygen and nitrogen permeation coefficients (PO2 and PN2) and the PO2/PN2 ratio for the polymer films formed from the PFMCH/CH4 mixture depended on the CH4 concentration. The small CH4 addition was effective in improvement of the PO2 value and of the PO2/PN2 ratio, but the much addition was ineffective. The oxygen transport through the plasma‐polymers was discussed.
Effect of water‐soluble polymers on fusion of egg yolk and soybean phospholipid liposomes
Authors: Abe Koji , Sakamoto Hidehiko , Itoh Yoshihiro , Senoh Saburo
Published: April 2003

The efficiencies of polyelectrolytes, i.e., polycations and polyanions, and several kinds of water‐soluble polymers as fusogens on soybean phospholipid liposome (SL) and egg yolk phospholipid liposome (EL) were investigated by the fluorescence quenching method. There were optimal concentrations for the induction of fusion in every system. Polycations induced fusion of liposomes at very low concentration in comparison with other polymers. Poly(carboxylic acid)s induced fusion at relatively high concentration. A strong acidic polyanion with high molecular weight also induced fusion of liposomes. The induction efficiency of poly(ethylene glycol) on fusion was higher than other nonionic polymers. The efficiency of fusion of EL was lower than that of SL in all systems because of the higher stability of EL membrane. It was found that electrostatic interactions, hydrogen bonding and/or hydrophobic interaction between these water‐soluble polymers and liposomal membranes played an important role on aggregation and fusion of liposomes.
Kinetics of successive seeding of monodisperse polystyrene latexes. II. Azo initiators with and without inhibitors
Authors: Sudol E. D. , El‐Aasser M. S. , Vanderhoff J. W.
Published: April 2003

Oil soluble azo initiators in combination with water soluble inhibitors were used to extend the particle size limit in studies of the kinetics of successive seeding of monodisperse polystyrene latexes. Monodisperse latexes were prepared up to 2.5 μm in diam using 4.0 mM AMBN and 14.5 mM hydroquinone with a constant 15% emulsifier (Aerosol–MA) surface coverage throughout the seven step sequence. The polymerization kinetics were measured in a piston/cylinder dilatometer designed for microgravity experiments. The Interval III kinetics were dominated by the gel effect although these were affected by the nature of the inhibitor. In general, the overall polymerization rate decreased with increasing particle size (decreasing Np) up to a size of about 1 μm. Thereafter, the kinetics were independent of these variables, exhibiting Smith‐Ewart Case 3 (bulk) kinetics. The initiator efficiencies were found to be of the order of 10%, considerably lower than reported for bulk polymerizations.
Studies on the mechanism of oligomerization of alkynes by group IVB catalysts
Authors: Farona Michael F. , Thanedar Shrinavas , Famili Amir
Published: April 2003

The homogeneous catalyst systems Cp2MCl2/C2H5AlCl2 (Cp = cyclopentadienyl; M = Ti, Zr) were found to promote homooligomerization of internal and terminal alkynes. Studies using titana‐ and zirconacyclopentadienes without cocatalysts revealed that these molecules were likely formed in the reactions and were active catalytic intermediates. Isolation of expanded metallacycles indicated that the mechanism of oligomerization proceeded by successive insertion reactions to produce larger metallacycles, eventually giving linear oligomers of low molecular weight.
Aliphatic polyimides from phenylene bis(succinic anhydride) and bis(glutaric anhydride)
Authors: Teshirogi Takuma
Published: April 2003

Meta and para derivatives of phenylene bis(succinic anhydride) and bis(glutaric anhydride) were obtained from 1,3‐ and 1,4‐bis(β‐cyano‐β‐carbethoxyvinyl)benzene with potassium cyanide or Meldrum acid followed by hydrolysis with concentrated hydrochloric acid and dehydration with acetic anhydride. Aliphatic polyimides were prepared from these anhydrides with six aromatic diamines through thermal ring closure of polyamic acids obtained by solution polymerization in dimethylacetamide, and thermal stability of these polyimides was examined by thermogravimetric analysis.
Anionic polymerization with expansion in volume
Authors: Brady Robert F. , Simon Frederick E.
Published: April 2003

New bicyclic and tricyclic compounds have been synthesized by the Lewis acid‐catalyzed condensation of epoxides with cyclic acid anhydrides or cyclic bislactones. These materials take part in the anionic addition polymerization of amine‐functional polyamides with diepoxides, and modify the shrinkage that is characteristic of the reaction. It is possible to control the extent of shrinkage by choosing an appropriate comonomer and by adjusting the concentration of this material in the reaction mixture.
Mass spectrometric characterization of poly(ethylene terephthalate‐co‐p‐oxybenzoate)
Authors: Garozzo Domenico , Giuffrida Mario , Montaudo Giorgio , Lenz Robert W.
Published: April 2003

Copolyesters containing ethylene terephthalate and p‐oxybenzoate units in mole ratios of ca. 80:20, 70:30, 40:60, and 20:80, respectively, were examined by direct pyrolysis–mass spectrometry to obtain information about the thermal stabilities and the sequences distributions of the two types of units as a function of composition. Thermal stability as measured by rate of volatilization increased with increasing oxybenzoate content, as did the amount of char residue formed. The electron impact mass spectrum of the volatile fragments showed the formation of predominantly linear fragments with carboxyl and vinyl end groups. Dimer, trimer, and tetramer fragments containing either or both types of units could be identified and their relative amounts could be estimated from peak intensities. The results were consistent with those expected for random distributions of the two units, i.e., for statistical copolymers.
Synthesis and characterization of poly[3,5′‐(3‐pyridyl methyl)‐2,6,‐diaminotoluene] and its condensation product, poly[4‐(3‐pyridyl),8‐methyl,2,3‐6,7‐quinolino]
Authors: Ruan J. Z. , Litt M. H.
Published: April 2003

2,6‐Diaminotoluene was reacted with 3‐pyridinecarboxaldehyde in acidic medium and the intermediate polymer was further condensed in polyphosphoric acid at high temperature (335°C) to obtain a soluble heterocyclic ladder polymer, poly[4‐(3‐pyridyl),8‐methyl,2,3–6,7‐quinolino] (PPMQ). The molecular weight of the intermediate polymer depended on the reaction temperature and the rate of reactant addition. The NMR spectra of the intermediate polymer indicated that a linear polymer with resonable molecular weight was formed. Element analysis and IR spectra confirmed the structure of the final polymer.
Polymers containing the [2H]‐1,2,4‐triazoline‐3‐thione ring
Authors: Katritzky Alan R. , Cato Stephen J. , Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R.
Published: April 2003

High‐molecular‐weight polymers containing [2H]‐1,2,4‐triazoline‐3‐thione rings are prepared by the condensations of diisothiocyanates with bis(acid hydrazides) to give intermediate polymeric acylthiosemicarbazides that are ring‐closed by refluxing in 1M aqueous sodium carbonate. Thermal cyclization of the polymeric acylthiosemicarbazides leads to cross‐linked insoluble products. The acylation of bis(thiosemicarbazides) with bis(acid chlorides) produces polymers of a similar structure but lower molecular weight.
New polymer syntheses 16. LC‐copolyesters of 3‐(4‐hydroxyphenyl) propionic acid and 4‐hydroxy benzoic acids
Authors: Kricheldorf Hans R. , Conradi Arnd
Published: April 2003

The polycondensation of 3‐(4‐hydroxy phenyl)‐propionic acid, 4‐Hypp, by means of acetanhydride or acetylchloride was conducted either in the presence or in the absence of a liquid reaction medium. DSC measurements, polarizing microscope, and X‐ray diffraction studies indicate poly(4‐Hypp) possesses at about 215°C a reversible first order transition between two solid phases. Copolyesters containing various mole ratios of 4‐Hypp and 4‐hydroxy benzoic acid, 4‐Hybe, were prepared by bulk condensation with acetanhydride at 320°C. At 4‐Hypp/4‐Hybe ratios less than 1.0:1.5 the reaction product was heterogeneous, containing crystals of pure poly(4‐Hybe). Neither increasing the reaction time nor the variation of the transesterification catalyst resulted in an entirely homogeneous copolyester. However, for 4‐Hypp/4‐Hybe ratios greater than 1.0:1.5, 13C NMR spectra indicate perfectly random sequences. Also, terpolyesters containing 3‐chloro‐4‐hydroxy‐ or 3,5‐dichloro‐4‐hydroxy‐benzoic acid were heterogeneous with less than 30 mol % 4‐Hypp. DSC measurements revealed for all polyesters a glass transition in the range of 55–78°C. Temperature dependent X‐ray diffraction studies confirm that the solid phase is a s.c. LC‐glss. Correspondingly low heat distortion temperatures were found by thermomechanical analyses. The copolyesters display under the polarizing microscope LC‐phase up to temperatures of 450–480°C, where rapid thermal degradation prevents further investigations. In the case of the 4‐Hypp/4‐Hybe 1:1 copolyester, the LC‐phase extends over a temperature range of about 400°C. TGA measurements indicate beginning thermal degradation at temperatures between 350 and 380°C.