bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of soluble microgel by the copolymerization of methylmethacrylate with p‐divinylbenzene in the presence of tetrabromomethane
Authors: Chen Hui , Ishizu Koji , Fukutomi Takashi , Kakurai Toshio 
Published: April 2003

AbstractVarious types of soluble crosslinked polymers obtained from the copolymerization of methylmethacrylate (MMA) and p‐divinylbenzene (p‐DVB) in the presence of a transfer agent (CBr4) have been discussed in relation to the variation of the structure during the reaction time. When [p‐DVB]/[MMA] = 1.49 × 10−3 and [CBr4]/[MMA] = 1.28 × 10−4, only linear polymers (primary polymer; Mn = 1.0 × 105) with pendant vinyl groups are formed intially. Considerable branched structure is attained in rather large polymers (Mn = 2.5 × 105), but the number of pendant double bonds is not enough to reach the gelation. As the concentration of the transfer agent becomes high, the intermolecular crosslinking is depressed, and the formed polymers contain loops and short chains. At [p – DVB]/[MMA] = 7.43 × 10−3 and [CBr4]/[MMA] = 1.28 × 10−3, the shape of polymer with the same Mn became compact gradually with increasing reaction time. These results are considered to be useful for the preparation of soluble crosslinked polymer with controlled structure.
Hydroxamic acid polymers. Effect of structure on the chelation of iron in water: II
Authors: Varaprasad D. V. P. R. , Rosthauser J. , Winston A. 
Published: April 2003

AbstractThe effect of structure on the ability of hydroxamic acid polymers to chelate iron(III) was examined. The polymers were derived from acryloyl or methacryloyl backbones that bore side chains terminated in hydroxamic acids. The side chain length, which establishes the atomic chain distances between hydroxamic acid groups, had the most pronounced effect on the stability constant of the iron chelate. It was this atomic chain distance that determined how easily the three neighboring hydroxamic acids could fit the octahedral sphere of the iron. Other structural changes such as the presence or absence of methyl groups on the backbone or on the hydroxamic acid nitrogen had little measurable effect. The stability of the iron complexes appeared to be optimum at an 11‐atom spacing between hydroxamic acids and decreased with shorter or longer spacing distances.
Photocationic crosslinking of poly(2,3‐epithiopropyl methacrylate) and photo‐initiated cationic polymerization of its model compounds
Authors: Tsunooka Masahiro , Ueda Toshihiro , Tanaka Makoto , Egawa Hiroaki 
Published: April 2003

AbstractPhotocationic crosslinking of a poly(2,3‐epithiopropyl methacrylate) (PETMA) film containing 4‐N,N‐diethylaminobenzene diazonium tetrafluoroborate (DAC) was investigated. Very rapid photocrosslinking of PETMA was observed and the rate was greater than that of poly(glycidyl methacrylate) with DAC. Post‐heating of the irradiated PETMA film resulted in a decrease of the insoluble fraction. This decrease was explained by scission of crosslinking points by the BF3. In the present conditions, more than 0.3 wt % of DAC was required to insolubilize the PETMA film. Photopolymerizations of propylene sulfide (PS) and 2,3‐epithiopropyl pivalate (ETPP) in the presence of DAC were investigated. The polymerization of PS proceeded smoothly but addition of ethyl acetate to PS depressed the rate and the degree of polymerization. ETPP could not be polymerized but copolymerized with PS by this method. Addition of ETPP to PS depressed both the rate of the polymerization and the degree of polymerization. From these results, it is deduced that the photocrosslinking of a PETMA film is caused by a cationic polymerization of episulfide groups but the chain length is not large.
Surface degradation of wood by ultraviolet light
Authors: Hon David N.‐S. , Chang Shang‐Tzen 
Published: April 2003

AbstractWood is beautiful but sensitive to light. Because of the chromophoric system at its surface, ultraviolet light cannot penetrate it deeper than 80 μm. Surface characteristics of ultraviolettreated wood were analyzed by infrared and ultraviolet spectroscopy. Analyses of infrared spectra revealed that ultraviolet‐treated wood is rich in carboxylic and carbonyl chromophoric groups and poor in aromatic functional groups. Ultraviolet spectral studies suggest that water‐soluble low molecular weight fractions of degraded products from the wood surface are mainly derived from lignin. These degradation products contained carbonyl conjugated phenolic hydroxyl groups and had a weight‐average molecular weight of about 900, confirmed by gel permeation chromatography.
Bis(difluoroaluminum)organophosphonates and difluoroaluminumdiorganophosphinates
Authors: Flagg Edward E. , Schmidt Donald L. 
Published: April 2003

AbstractOligomers and polymers of the general types [RR′P(O)OA1F2]n, I, and [F2AlOP(R)(O)OAlF2]n, II, were prepared by the addition of phosphonic or phosphinic acids and hydrogen fluoride to etherated alanes. The hydrocarbon moieties (R,R′) on the phosphonic and phosphinic acids were important determinants of physical and chemical properties. When the alkyl moieties contained six or more carbon atoms type I oligomers were partially crystalline, soluble in tetrahydrofuran, and fused below 415°C. Type II polymers were soluble in tetrahydrofuran when n‐octyl or larger alkyl moieties were used, but these polymers tended to be amorphous and liberated solvated tetrahydrofuran below 225°C. Data are presented in support of inter‐monomer fluorine bridge bonding; that is, AlFAl bonds.
Crown ethers as ligands for stereospecific polymerization by Ziegler–Natta catalysts
Authors: Jarrin J. , Dawans F. , Marechal E. , Boileau S. 
Published: April 2003

AbstractSome new TiCl4/Crown ether complexes were synthesized and used as polymerization catalysts with AlEt3 or AlEt2Cl as cocatalyst for the stereospecific polymerization of 1,3‐butadiene. As with most of the nucleophilic ligands the addition of crown ethers to Ziegler–Natta catalytic systems results in a decrease of the polymer conversion. But the Al/Ti molar ratio appears to be less critical for the complexed systems than for the uncomplexed ones. The presence of the crown ether in the surroundings of the catalytic sites presumably protects them from an excess of the organoaluminum cocatalyst. The side groups of the crown ether do not influence the microstructure of the polybutadiene obtained but they change the activity of the catalytic systems. Thus, the electron‐donating effect of the macrocyclic ligands seems to be less important than the sterical effect due to the rigidity and to the hole size of the crown ether.
Copolymers of vinylamine and vinylalcohol by acid hydrolysis of poly(N‐vinyl‐tert‐butylcarbamate‐co‐vinylacetate): Evaluation of reactivity ratios
Authors: Brouwer W. M. , Piet P. , German A. L. 
Published: April 2003

AbstractCopolymers of vinylamine and vinylalcohol were prepared by hydrolysis of poly(N‐vinyltert‐butylcarbamate‐co‐vinylacetate) in 1:1 v/v % ethanol/HCl mixtures at room temperature. Reactivity ratios of the monomers N‐vinyl‐tert‐butylcarbamate (1) and vinylacetate (2) were calculated from monomer feed and copolymer composition data, according to the methods of Fineman–Ross and Kelen–Tüdös, yielding r1 = 1.14 ± 0.05, r2 = 0.47 ± 0.07, and r1 = 1.12 ± 0.07, r2 = 0.46 ± 0.03, respectively. From these values the average sequence length distribution of monomer units was derived showing that in the raction of N‐vinyl‐tert‐butyl carbamate and vinylacetate nearly Bernouillian (i.e., purely random) copolymers are formed, with a slight tendency toward alternation.
Determination of absolute rate constants for free radical polymerization of ethyl α‐fluoroacrylate and characterization of the polymer
Authors: Yamada Bunichiro , Kontani Takashi , Yoshioka Minoru , Otsu Takayuki 
Published: April 2003

AbstractThe absolute rate constants for propagation (kp) and for termination (kt) of ethyl α‐fluoroacrylate (EFA) were determined by means of the rotating sector method; kp = 1120 and kt = 4.8 × 108 L/mol.s at 30°C. The monomer reactivity ratios for the copolymerizations with various monomers were obtained. By combining the kp values for EFA from the present study and those for common monomers with the monomer reactivity ratios, the absolute values of the rate constants for cross‐propagations were also evaluated. Reactivities of EFA and poly(EFA) radical, being compared with those of methyl acrylate and its polymer radical, were found to be little affected by the α‐fluoro substitution. Poly(EFA) prepared with the radical initiator was characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Although the glass transition temperature obtained by DSC for poly(EFA) resembled that of poly(ethyl α‐chloroacrylate), its TGA thermogram showed fast chain de polymerization to EFA that was distinct from complicated degradation of poly(ethyl α‐chloroacrylate).
Functional monomers and polymers. CXVII. Photochemical reactions on oligo‐ and polyethyleneimines containing pendant thymine bases: Effect of the spacer
Authors: Suda Yasuo , Kono Michihiro , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractThe photodimerization reaction of thymine bases incorporated in the modified oligo‐ and polyethyleneimines, in which α‐alanine or ß‐alanine unit was inserted between the main chain and the pendant thymine bases, was studied both in aqueous and in dimethyl sulfoxide solutions. It was found that the quantum yields for the photodimerization for the oligomers were closely related to the intramolecular interaction in the ground state, while those of the copolymers were not related to the ground state interaction. It was suggested that the singlet energy migration was present in the case of the polyethyleneimine derivatives. This result is discussed in terms of the effects of the nearest‐neighboring thymine units, the structure of the side chain, and the singlet energy migration, particularly for the copolymers.
Polymerization photoinitiated by carbonyl compounds. VI. Mechanism of benzil photoinitiation
Authors: Encinas M. V. , Lissi E. , Gargallo L. , Radic D. , Sigdman R. 
Published: April 2003

AbstractThe mechanism of the photoinitiation of the vinyl polymerization sensitized by benzil and 4,4′‐dimethoxybenzil was studied. The monomers considered were methacrylic acid esters and styrene derivatives. All these monomers are efficient quenchers of the excited triplet benzil. However, the initiation efficiency of the benzil is important only when styrene derivatives are employed as monomers. The main polymerization process follows a simple free radical mechanism. The initiation step is a consequence of the interaction (triplet benzil–monomer double bond) through a charge transfer complex.
Poly‐2‐vinylfuran, synthesis, characterization, and diels‐alder reaction with maleic anhydride
Authors: Küsefoǧlu Seli̇m H. 
Published: April 2003

AbstractPoly‐2‐vinylfuran, synthesized by free‐radical polymerization of 2‐vinylfuran, was characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. The pendant furan rings on the polymer backbone were then used as the diene component of a Diels‐Alder reaction with maleic anhydride. The juxtaposition of the furan rings at first suggested an “avalanche” Diels‐Alder reaction, in which the product of one cyclization would be the reactant of the next. A lack of polymer stereoregularity and the reversibility of the Diels‐Alder reaction, however, prevented its formation. On the other hand, when the dienophile was used in a 1:1 molar ratio with respect to furan the smooth reaction produced a new polymer, the maleic anhydride adduct of poly‐2‐vinylfuran, which characterized by NMR and IR spectroscopy, was air stable and soluble in a number of solvents up to 70% transformation. When heated to 160°C the polymer reverted to maleic anhydride and somewhat decomposed poly‐2‐vinylfuran.
Reactions in the presence of organic phosphites, II: Low‐temperature amidatior in solvent
Authors: Aharoni Shaul M. , Hammond Willis B. , Szobota John S. , Masilamani Divakar 
Published: April 2003

AbstractPolyamides and related model compounds were prepared from carboxy acids and primary amines by reacting them with triphenylphosphite in an appropriate solvent at 100°C. The reactions proceeded in the absence of organic base but were accelerated by the addition of bases such as pyridine. Nevertheless, even the powerful combination of 13C and 31P NMR failed to indicate the presence of pyridinium phosphite in the reaction mixture. In the reaction of a primary amine and carboxyl groups a detectable amount of the diphenoxy aminophosphine intermediate was observed. The end products are the amides, phenol, and diphenyl phosphite. When primary amine was not present a slow formation of a phenyl ester of the carboxylic acid was evident. All the intermediate species and the end products were formed with or without added pyridine. A mixed anhydride of carboxylic acid and phosphite was never seen. The results in this article are fundamentally the same as those in the companion article (I) for which the data were obtained at 280°C in the absence of solvent and base. However, because the reaction went quickly to completion at 280°C, the diphenoxy aminophosphine intermediate was not observed. A mechanism for the amidation in which the diphenoxy aminophosphine is an initial reaction intermediate is proposed. This species reacts with the carboxylic acid through an intramolecular substitution to give an amide. This mechanism may be valid for the high‐temperature reactions as well. Several minor unclear points are indicated.
Catalyseurs Zieger‐Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. II. Système catalytique simple: Solide binaire MgCl2‐TiCl4 et solution cocatalytique triéthylaluminium, benzoate d'ethyle
Authors: Spitz R. , Lacombe J. L. , Guyot A. 
Published: April 2003

AbstractThe kinetics of propene polymerization in heptane slurry at 1–4 bars was studied with a catalytic system that consisted of a solid catalyst prepared by adsorption of TiCI4 on pure porous MgCl2 (by dehydrating MgCl2, 6 H2O with thionyl chloride) and a cocatalytic, heptanic solution of ethylbenzoate (BE) and triethylaluminium (TEA). At a temperature approaching 60°C/polymerization began immediately after the introduction of the monomer. The polymerization rate decreased continuously during the reaction. The loss in activity, however, was not due to a diffusional effect (e.g., blocking of the catalyst by the growing polymer). Studies of the ageing of the catalytic system showed a deactivation of the catalytic system itself as a function of the time of contact between the catalyst and the cocatalyst. The product of the thermal decomposition of the complex 1:2 formed by the reaction of BE with TEA was not associated with the deactivation process or stereospecific control, which depend on the BE/AI ratio and the presence of the complex.
New telechelic polymers and sequential copolymers by polyfunctional initiator–transfer agents (inifers). XLI. Kinetic and reactivity studies on sterically hindered inifers
Authors: Santos Raquel , Fehérvári Ágota , Kennedy Joseph P. 
Published: April 2003

AbstractThe kinetics of chain transfer to the bifunctional initiating and transfer agents (binifers) 1,4‐di(2‐chloro‐2‐propyl)benzene (p‐DCC), 1,3‐di(2‐chloro‐2‐propyl)‐5‐tert‐butylbenzene (m‐tBuDCC), and 1,3‐di(2‐chloro‐2‐propyl)‐4,6‐dimethylbenzene (m‐DMeDCC) in the polymerization of isobutylene has been investigated. Chain transfer to monomer was shown to be absent up to −20°C in CH3Cl/n‐hexane and CH2Cl2/n‐hexane mixtures using the m‐tBuDCC/BCl3 binifer system. Chain transfer constants (Ci) to m‐tBuDCC and kt/kp ratios determined in the range from −30°C to −80°C in CH3Cl/n‐hexane mixtures and pure CH3Cl solvent are reported, and the activation energy differences Etr,l − Ep and Et − Ep were calculated. Chain transfer constants to p‐DCC and m‐DMeDCC were determined by the use of pure CH3Cl diluent at −50°C. The chain transfer reactivity of five different inifers is discussed and compared based on CI values obtained under identical conditions, with special regard to the new, sterically hindered binifer m‐DMeDCC of extraordinary reactivity.
Semiconducting poly(monocyanoacetylenes)
Authors: Carlini Carlo , Chien James C. W. 
Published: April 2003

AbstractPoly(monocyanoacetylenes) (PMCA) were synthesized by anionic, Ziegler–Natta, metathesis, and photo initiations. The Ziegler–Natta‐catalyzed polymers probably have highly stereoregular cis‐transoid structure that contains very few defects and the nitrile groups are difficultly cyclized. It has M̄n = 1100. PMCA obtained by anionic polymerization at −78°C has M̄n ∼ 4800; it is rich in trans‐transoid structures but probably contains other isomeric units as well. The unpaired spin concentrations in these polymers are very high, comparable to that in trans‐polyacetylene (PA) isomerized above 150°C. UV irradiation initiated rapid polymerization of cyanoacetylene in solid state at low temperature but the products were bleached in color after long irradiation. The unpaired spins in PMCA are immobile; nitrile cyclization causes some decrease in EPR linewidth and increase in room‐temperature conductivity (σRT). There was also a large increase in unpaired spin concentrations to about 200 monomer units/spin. Iodine doping increases σRT to about 10−3 (ω cm)−1 but the dopant is readily removed by evacuation and the polymer returns to its original insulating state. The properties of pristine and doped PMCA, such as EPR g‐value, ΔHpp, T1, T2, and σRT are very similar. The similarities persist after cyclization and doping for this pair of polymers. These properties are also compared with those of poly(methylacetylene), poly(phenylacetylene), poly(dicyanoacetylene) and PA, and the significance is discussed.
Composition equation for matrix copolymerization
Authors: Połowiński S. 
Published: April 2003

AbstractA mechanism of matrix copolymerization in which a monomer (or macroradical) is complexed by matrix was considered. For this case a composition equation was formulated. It was shown that in general case reactivity ratios are dependent on the matrix concentration. The influence of the critical length of a complexed radical on the process of copolymerization is also discussed. A series of copolymerizations of methacrylic acid and styrene were carried out using various compositions of initial monomer mixtures. The process was performed in benzene in the presence of poly(ethylene glycol) as a matrix. The copolymerization were carried out at various ratios of the monomer being complexed (methacrylic acid) to the matrix. Compositions of the complexes prepared were determined by the NMR method. Reactivity coefficients for both monomers were found and the results are discussed on the basis of the derived equation.
Solid‐state polymerization of butadienes. Crystal structure and solution properties of a stereoregular amphoteric 1,4‐trans‐polybutadiene
Authors: Tieke B. , Chapuis G. 
Published: April 2003

AbstractThe double salt 1 consisting of the hydrochloride of 6‐amino‐2,4‐trans‐hexadienoic acid and cadmium chloride in a 2:1 stoichiometry polymerizes in the crystalline state if exposed to UV or γ irradiation. A stereoregular polymeric ampholyte is formed in an extended chain macroconformation, embedded in an inorganic matrix. The crystal structure of the polymerized crystals and the solution properties of the polymer are reported. Polymerized crystals are triclinic, space group P1, a = 7.2144 Å, b = 7.2447 Å, c = 18.5936 Å, α = 104.49°, β = 96.631°, γ = 95.706°, Z = 2. The structure consists of 2‐dimensional layers of polymer and inorganic CdCl6 octahedra alternatively stacked in the third dimension. The cadmium ions can be separated from the polymer by a precipitation as insoluble CdS. After separation from the inorganic material the polymer is soluble in strong acids and bases and insoluble in neutral water. From viscosity measurements of alkaline solutions of the polymer, an average molar mass of 4 × 104 g/mol can be deduced. The polymer selectively adsorbs divalent transition metal ions if suspended in an aqueous solution of transition metal salts. The structure of the resulting polymer–metal complexes is discussed.
Acyloin condensation of terephthaloyl chloride—a novel route to polyhydroxyketones
Authors: Nallaiah C. 
Published: April 2003

AbstractAcyloin condensation of terephthaloyl chloride under homogeneous conditions using a sodium naphthalene radical anion system and under heterogeneous conditions using finely dispersed molten sodium with varying ratios of sodium to organic substrate gave mainly polymeric materials that were identified as polyhydroxyketones. IR, NMR, and DTA analyses indicate that these polymers are copolymers of benzoin and benzil hitherto unknown. The yields of polymers under homogeneous conditions were higher than those obtained under heterogeneous conditions, but the molecular weight distribution was similar to those obtained with molten sodium.
Studies of phosphazenes. XIX. New polyorganophosphazenes derived from the friedel–crafts reactions of hexa(aryloxy)cyclotriphosphazenes with polyhaloalkanes
Authors: Katti K. V. , Krishnamurthy S. S. 
Published: April 2003

AbstractThe reactions of hexa(aryloxy)cyclotriphosphazenes N3P3(OR)6[R = C6H5, C6H4CH3‐p] with polyhaloalkanes in the presence of anhydrous aluminium chloride yield new crosslinked phosphazene polymers which are characterized by elemental analysis, IR spectroscopy, and pyrolysis—mass spectrometric measurements. Soluble “prepolymers” are obtained by using stoichiometric quantities of the phosphazene and haloalkane in nitromethane as the solvent. The 1H and 31P NMR data for these “prepolymers” are presented. The thermal stability of the polymers derived from various haloalkanes decreases in the order 1,2‐ClCH2CH2Cl < CHCl3 > CH2Cl2 > CCl4. The thermal stability also increases with increasing amounts of the catalyst, reaching a maximum at 1:10 mol ratio of N3P3(OPh)6:AlCl3. The phosphazene polymers reported here possess much greater thermal stability compared to linear polyorganophosphazenes, [NPR2]n, as well as the polymers prepared by the Friedel–Crafts reactions of P(O)(OPh)3 and P(O)(OC6H4CH3‐p)3 with haloalkanes.
Synthesis and characterization of β‐forming poly[S‐(ω‐N‐carbazolylalkyl)‐L‐cysteine]s
Authors: Oshima R. , Wada T. , Kumanotani J. 
Published: April 2003

AbstractPoly(L‐cysteine derivative)s containing carbazole groups in the side chains separated from the backbone by several distances have been synthesized. It is revealed by measuring the IR spectra that they assume the antiparallel‐chain pleated sheet (β‐conformation) in the solid films independent of side chain length. DSC thermograms, and CD and fluorescence spectra of the films of these polymers are also presented in relation to the alignment of side‐chain carbazole groups.
The kinetics of oxidative coupling of 2,6‐dimethylphenol with a copper‐diamine catalyst system
Authors: Mobley David P. 
Published: April 2003

AbstractReaction rate measurements show that a Michaelis‐Menten model proposed earlier is inadequate to describe the full course of the polymerization of 2,6‐dimethylphenol to poly(2,6‐dimethyl‐1,4‐phenylene oxide). Modification of this model to include the effects of catalyst deactivation during the reaction and difference in reactivity between the monomer and other oligomers resulted in much greater accuracy. The kinetic constants in the modified model were influenced by reaction temperature, system composition, and method of catalyst component addition.
Initiation reactions in thermal polymerization of vinyl monomers in the molten state
Authors: Verneker V. R. Pai , Santhanalakshmi K. N. 
Published: April 2003

AbstractEvidence of the initiation process during uncatalyzed thermal polymerization of vinyl monomers is presented. DSC studies reveal a prominent endothermic effect just before the polymerization exotherm, which is substantiated by the identification of the free radicals produced in the initiation by a quick quenching technique and subsequent detection by ESR at low temperatures.