bluuebunny/crossref_metadata_2025 huggingface dataset:
Some electrical properties of wood pulp treated with sodium hydroxide
Authors: Hanna A. A. , Ibrahem Atef A. , Heikal Salwa O.
Published: April 2003

The effect of the degree of crystallinity and degree of polymerization on the electrical properties of soda‐treated wood pulp has been investigated. The dielectric constant (E′) and the dielectric loss (E″) were measured for the treated samples over a frequency band 0.2–10 MHz at 20°C. Also, the electrical conductivity (σ) was calculated from the measured data of the dielectric constant. From the results obtained we found that the degree of crystallinity and the degree of polymerization decrease with time of oxidation while the number of carboxylic groups increased. E″,E′, and σ were found to increase with the decrease in the degree of crystallinity.
New processable poly(ether‐keto‐sulfone)s, poly(arylene sulfone)s, and polyesters curable by intramolecular cyclization. XVII
Authors: Somers A. , Marvel C. S.
Published: April 2003

New processable polyaromatic ether‐keto‐sulfones were prepared from 2,2′‐diiododiphenyl‐4,4′‐dicarbonyl dichloride (I), bis(p‐phenoxybenzene)sulfone (V), isophthaloyl chloride (VI), terephthaloyl chloride (VII), and diphenylether (IX) in Friedel‐Crafts‐type polymerizations. By varying (VI):(VII) ratio and (V):(IX) ratio and by reducing the polymerization time, soluble, processable polymers were obtained. In these polymers, phenylacetylenyl groups were introduced by replacing the iodine. This process led to soluble and curable polymers. Transparent, tough films and fairly flexible glass fiber laminates can readily be prepared. After curing, the polymers were insoluble and showed excellent chemical and thermal resistance. The curing process increased the polymers' softening temperature by ca. 20°C and produced intersting new useful materials for laminates. Processable poly(arylene sulfone)s were prepared from I, V, and diphenylether‐4,4′‐disulfonylchloride (X) in a Friedel‐Crafts‐type polymerization. Different monomer ratios and polymerization times were used. Only low‐molecular‐weight polymers were obtained. The same result was shown by curable polyester formation from I, VI, VII, and 4,4′‐sulfonyldiphenol (XI) in an interfacial polycondensation.
Polymerization of N‐vinylpyrrols
Authors: Trofimov B. A. , Minakova T. T. , Tandura T. A. , Mikhaleva A. I. , Korostova S. E.
Published: April 2003

The free polymerization of 2‐methyl‐1‐vinylpyrrol (I), 2,3‐dimethyl‐1‐vinylpyrrol (II), 1‐vinyl‐4,5,6,7‐tetrahydroindol (III), 1‐vinyl‐2‐phenylpyrrol (IV), and 1‐vinyl‐2‐phenyl‐5‐trifluoroacetyl pyrrol (V) in the presence of azobisisobutyronitrile as an initiator at 60–80°C has been studied. The polymer yield (up to 90%) and molecular weight in the range 2000–13,000 are strongly dependent on the monomer structure and the polymerization conditions. The reactivity of N‐vinylpyrrols studied falls in the order: I > III > II > V > IV implying an important role of the initial radical stabilization with the participation of the ring substituents as well as the steric hindrances in the propagation stage.
A study of the mechanism of radiation‐induced polymerization of carbon suboxide
Authors: Barkalov I. M. , Kim I. P. , Mikhailov A. I. , Kiryukhin D. P.
Published: April 2003

The γ radiolysis of solid C3O2 at 77 K produces paramagnetic centers of several types. The ESR spectrum constitutes a number of narrow lines with an anisotropic g factor. Some of the centers are photounstable and are lost after optical bleaching. Heating the sample results initially in the loss of photounstable centers and then, in the temperature region in which solid C3O2 undergoes a phase transition (140 K), loss of the centers responsible for the center section of the ESR spectrum. In the temperature region 140–270 K concentration of the centers remained at the level of 1015−1016 g−1. At higher temperatures an intense polymerization of liquid C3O2 followed by a sharp increase in concentration of the paramagnetic centers was observed. It is assumed that in radiolysis at 77 K and on subsequent heating the formation of oligomeric centers in solid C3O2 results in a decreasing probability of their loss. Using a calorimetric technique, we studied the kinetics of the postradiation polymerization of C3O2. Small additions of acetone (cationic inhibitor) brought about the loss of the oligomeric centers and suppressed completely all postpolymerization. The polymerization rate increased with the concentration of the resulting polymer. An autocatalytic character of the process is supposed to be connected with the formation of polymer‐monomer complexes.
Application of high‐performance size‐exclusion chromatography to the determination of low‐molecular‐weight compounds in polyarylethers
Authors: Brydia L. E. , Garty O. M.
Published: April 2003

The production of high‐molecular‐weight polymers is often accompanied by the formation of oligomers and of side products. Since the presence of these and other low‐molecular‐weight compounds (e.g., monomers and additives) can have a significant effect on the ultimate performance properties of the basic polymer, their quantitative determination is of great importance. This article presents a facile method for separating and quantifying low‐molecular‐weight compounds in polymers. The advent of high‐performance size‐exclusion column‐packing materials extends the application of liquid chromatographic size separations to small molecules. By using two 500‐Å μ‐Styragel columns in series and a chloroform mobile phase, the polymers being studied elute near the solvent front with subsequent resolution of lower‐molecular‐weight components. The described method, which includes the use of an appropriate internal standard, results in determinations that are independent of mobile phase‐polymer interactions. The utility of this analytical technique is exemplified in the determination of cyclic dimers and other low‐molecular‐weight compounds in polysulfones and polyhydroxyethers.
ESCA applied to polymers. XXVI. Investigation of a series of aliphatic, aromatic, and fluorine‐containing polycarbonates
Authors: Clark D. T. , Feast W. J. , Tweedale P. J. , Thomas H. R.
Published: April 2003

The absolute and relative binding energies for the C1s, O1s, and F1score levels have been determined using x‐ray photoelectron spectroscopy (ESCA) for a series of aliphatic, aromatic, and fluorine‐containing polycarbonates. Comparisons of these experimentally determined, core‐level binding energies with theoretical calculations using the ground‐state potential model in the CNDO/2 SCF MO formalism as well as model compounds have been made on the C1sand O1score levels. The degree of polymerization for low‐molecular‐weight fluorine‐containing polycarbonates, as determined from ESCA measurements, is compared to measurements by vapor‐phase osmometry and19F‐NMR.
Polyesters containing ring units in main chains. I. Preparation and stereochemistry of monomers and polyesters
Authors: Matsumoto Naoji , Daimon Hiroshi , Kumanotani Ju
Published: April 2003

Cycloalkanone (C5–C8, C12, and C15) or cycloalkane (C5 and C6) ring‐containing monomeric diesters and the polyesters derived from them were prepared, and their configurations were studied by 13C‐NMR spectroscopy. Absolute configurations were determined for ring sizes 5, 6, and 7. Configurational change during reduction of a ketonic group of monomeric diesters with ring sizes 5 and 6 was discussed in terms of the steric effect of ring substituents on the ketonic group. In the polycondensation reaction epimerization of the ring units was observed in 5‐, 6‐, and 7‐membered cycloalkanones and not in others, which is explained by steric hindrance by the ring substituents against attack of tetrabutyl titanate catalyst on the ketonic group.
Grafting of polytetrahydrofuran from neoprene W in the presence of perchlorate salts
Authors: Eckstein Y. , Dreyfuss P.
Published: April 2003

Silver, mercury, and lead perchlorates can be used to prepare graft copolymers of polytetrahydrofuran from neoprene. Iron and aluminum perchlorates lead to graft copolymers but the conversion is low. The most efficient graft copolymerizations are obtained at high salt‐to‐neoprene ratios, long reaction times, and low monomer‐to‐neoprene concentration ratios. Very surprisingly, high initial monomer‐to‐neoprene concentration ratios lead to low graft copolymerization efficiencies.
Polyelectrolyte effects on the charge transfer complex formation between FMN and indole derivatives
Authors: Ishiwatari Tsutomu , Okubo Tsuneo , Ise Norio
Published: April 2003

The complex formation of flavin mononucleotide (FMN) with tryptamine, indoleacetate, and trytophan was investigated in the presence of polyelectrolytes; that is, sodium polyethylene sulfonate (NaPES), sodium polystyrene sulfonate (NaPSS), and a copolymer of diethyldiallylammonium chloride and sulfur dioxide (DECS). The complexation of FMN and tryptamine was strongly retarded by the macrocations and macroanions, whereas that of FMN and indoleacetate was enhanced by the macrocations. Furthermore, the equilibrium constants of FMN‐tryptophan complex were insensitive to the addition of polyelectrolytes. These results suggest that the complexation of FMN was strongly influenced by the electrostatic interactions between the reactant ions and macroions, in addition to those between the reactant ions, in conformity with the secondary salt effect.
High‐molecular‐weight poly(amino acid)s by the direct polycondensation reaction promoted by triphenyl phosphite and LiCl in the presence of polyvinylpyrrolidone
Authors: Higashi Fukuji , Sano Kenji , Kakinoki Hideo
Published: April 2003

Poly(α‐amino acid)s of high molecular weight were obtained by the direct polycondensation reaction of α‐amino acids in the presence of polyvinylpyrrolidone (PVP) as a matrix of triphenyl phosphite and LiCl in N‐methylpyrrolidone (NMP). Molecular weights of the polymer produced were improved by use of an increasing amount of matrix of higher molecular weight. Most favorable results were obtained by the reaction at 80°C for 16 hr at a monomer concentration of 0.33 mole/liter in a NMP solution that contained about 3 wt % LiCl in the presence of an equivalent unit mole of PVP with the molecular weight of 3.6 x 105. The polymer from β‐alanine with high molecular weight, which is difficult to obtain by the NCA method, was easily prepared by this process.
Functional monomers and polymers. LXXI. Conformation and interaction studies of poly‐L‐lysine derivatives with pendant nucleic acid bases
Authors: Ishikawa Tomohiro , Inaki Yoshiaki , Takemoto Kiichi
Published: April 2003

Copolymers of L‐lysine and L‐lysine derivatives which contained nucleic acid bases substituted on the Nε position were synthesized by grafting nucleic acid derivatives onto poly‐L‐lysine. The conformation and interaction of these copolymers in solution were studied by using spectroscopic measurements. They existed in helical conformation at neutral pH values, and the polymer complex formation among them was examined by ultraviolet (UV) measurements in organic solvents. A decrease in the nucleic acid base content of the copolymers resulted in a decrease in helical structures and also in interactions with the polymer‐containing complementary bases.
Polymer containing fluorinated ketone groups. I. DSC and NMR studies of poly(p‐vinyltrifluoroacetophenone) and polymers of similar structure
Authors: Cheng C. H. , Pearce E. M.
Published: April 2003

The unexpected crystallinity of free radically polymerized poly(p‐vinyltrifluoroacetophenone) (PVTFA) due to lateral order was previously found in this laboratory. To further the understanding of the relationship between chemical structure and crystalline order in polymers of the PVTFA type, polymers of similar structure were synthesized and characterized by differential scanning calorimetry (DSC). These polymers were poly(p‐vinyldifluoroacetophenone) (PVDFA), poly(p‐vinylphenylheptafluoropropyl ketone) (PVHFK), poly(p‐vinylacetophenone) (PVA), and poly(p‐vinylphenyltrifluoromethyl carbinol) (PVPTC). Only PVTFA had a crystalline melting temperature (188°C); 220‐MHz nuclear magnetic resonance (NMR) measurements on the microstructure of PVTFA and PVDFA revealed broad peaks for the chain protons. The PVTFA was therefore assumed to be predominantly atactic. The results suggested that the unusual crystallinity of PVTFA was related to the unique size and interaction of the trifluoroacetyl moiety on the polymeric side chain.
Polymers containing fluorinated ketone groups. II. NMR studies of the reaction of methylbenzyl trifluoromethyl ketones with alcohols in carbon tetrachloride
Authors: Cheng C. H. , Pearce E. M.
Published: April 2003

Prior to the study of poly(o‐ and p‐vinylbenzyl trifluoromethyl ketone) (PVTFK) polymers and their reaction with alcohols, the reactions of some simple model compounds with alcohols were investigated. The reaction of fluorinated ketones toward alcohols was determined by proton nuclear magnetic resonance (NMR) spectroscopy. Two fluorinated ketones–p‐methylbenzyl trifluoromethyl ketone (p‐MTFK) and o‐methylbenzyl trifluoromethyl ketone (o‐MTFK)–were prepared. Studies of the reaction of p‐MTFK and o‐MTFK to various alcohols based on NMR produced equilibrium constants (1M in CCl4) at 31°C that ranged from 0.1 to 6.0. The equilibrium constants for p‐MTFK with alcohols were larger than those for o‐MTFK. In addition, the equilibrium constants for primary alcohols were larger than those for secondary and tertiary alcohols. Steric effects in this reaction could explain the lowered equilibrium constants for o‐MTFK and the secondary and tertiary alcohols.
Radical polymerization of N‐vinylpyrrolidone in the presence of syndiotactic poly(methacrylic acid) templates
Authors: Koetsier D. W. , Tan Y. Y. , Challa G.
Published: April 2003

Radical polymerization of N‐vinylpyrrolidone along poly(methacrylic acid) templates of high syndiotatic content was followed dilatometrically in dimethylformamide, which was used as solvent. The effects of template concentration, template molar mass, and temperature on polymerization rate and average molar mass of the formed polyvinylpyrrolidone (PVP) were examined. Template concentrations were varied around the critical concentration for homogeneous segmental distribution, C*. Below this concentration, template coils can act as separate microreactors wherein growing PVP radicals exhibit maximum rate enhancement, i. e., relative rate νR = νR,max. In the free solution, blank polymerization occurs, i. e., νR = 1. Consequently, νR can be approximated by the equation νR = ϕνR,max + (1 − ϕ), where ϕ represents the volume fraction occupied by template coils. The slight increase in UR and PVP molar mass with the template chain length is supposed to be caused by the influence of translational diffusion on the termination step. Over the investigated temperature range of 50–70°C, the activation energy and entropy were almost identical for blank and template polymerization. An expected decrease of ΔE≠ and ΔS≠ in template systems is supposed to be compensated by the effects of desolvation of the template macromolecules during the propagation step.
Electroinitiated graft copolymerization
Authors: Funt B. Lionel , Hsu Li‐Chien
Published: April 2003

A technique has been developed for initiating a graft copolymerization electrochemically. A copoly(styrene/vinylbenzophenone) linear copolymer was prepared to serve as the electroactive starting material. The benzophenone sites on this molecule are readily activated at the cathode. Macroradical ions result from the direct transfer of electrons to benzophenone groups of the electroactive backbone polymer. In solution in N,N‐dimethylformamide with tetraethylammonium perchlorate (TEAP) as supporting electrolyte the passage of current produced a dark blue solution similar to that observed with radical anions obtained with benzophenone directly. When monomer such as acrylonitrile or methyl methacrylate was added, a graft copolymer was formed. Electrolysis of solutions of the backbone polymer in tetrahydrofurn (THF), with sodium tetraphenylboride as supporting electrolyte, produced relatively stable, persistent macroradical anions and, under appropriate conditions, the reddish‐violet macrodianions. Both types initiated graft copolymerization of acrylonitrile and methyl methacrylate. Graft copolymers were characterized by gel permeation chromatography (GPC), infrared (IR), and solvent extraction. High grafting efficiency (i. e., free from homopolymer) can be obtained under appropriate conditions. Suitable mechanisms are proposed, compared, and discussed.
Emulsion polymerization of acenaphthylene. I. A study of particle nucleation in water phase and in aqueous emulsions
Authors: Chen Chi‐Yu , Piirma Irja
Published: April 2003

As the first phase in the study of the emulsion polymerization of acenaphthylene (AcN), the oligomerization kinetics of the in‐aqueous‐phase soluble portion of the AcN monomer was investigated. The reactions were carried out in the absence and presence of anionic emulsifiers. The monomer disappearance rate was followed by ultraviolet (UV) spectroscopy and spectra were established for these species. It was found that aqueous phase AcN oligomerized with K2S2O8 initiator at 50°C to yield SOK+ ‐ended oligo ‐AcN species which showed a UV hypsochromic shift in polar solvents. The oligomerization had a second‐order dependence on monomer concentration. The presence of sodium oleate (SO) and sodium dodecyl sulfate (SDS) emulsifiers at below and above their critical micelle concentrations decreased the rate constant of the aqueous phase oligomerization. These observations led to the suggestion of a mixed micellization concept in the particle nucleation mechanism.
Methods for the determination of the number of polytetrahydrofuran branches in neoprene‐g‐polytetrahydrofuran
Authors: Eckstein Y. , Lee D. P. , Quirk R. P. , Dreyfuss P.
Published: April 2003

Methods for the determination of the number of the number of polytetrahydrofuran branches in neoprene‐g‐polytetrahydrofuran were examined. Only two suitable methods were found; namely, termination of oxonium ions by triphenylphosphine followed by 31P‐NMR and termination with NH4OHNH4Cl buffer and reaction with fluorescamine followed by fluorescence spectroscopy. Both methods led to the conclusion that Neoprene W has 9 ± 1 active halogens per mole that can be used to initiate tetrahydrofuran polymerization when silver salts are added. Among the methods examined in this study the fluorescence method was the most reliable, most reproducible, fastest, and simplest.
Splitting of the disulfide bonds in polysulfide polymers by hydrazine
Authors: Rekalić Vladimir J. , Tenc‐Popović Mirjana E. , Radosavljević Slobodan D.
Published: April 2003

The action of hydrazine on desulfurized tetrasulfide polymer obtained from bis‐2‐chloroethyl formal leads to SS bond splitting and depolymerization. Our studies show that successful depolymerization can be initiated only in a strong alkali medium at 95–98°C. During this process cleavage of the disulfide bonds and the formation of polymers of lower molecular weight with SH end groups takes place. From the results of the experiments performed it can be seen that the degree of depolymerization increases with an increase in the amount of hydrazine, in the mole ratio of sodium hydroxide, and in the time of reaction. When 0.7–1.0 mole of hydrazine per segment of polymer and 4 mole of sodium hydroxide per mole of hydrazine are used, a polymer of low average molecular weight in the form of water‐soluble sodium salt (fraction I) and a polymer in dispersion form (fraction II) are obtained. Similar results could be attained if the amount ot hydrazine were decreased and the mole ratio of sodium hydroxide were simultaneously increased to more than 4 mole per segment of hydrazine used. In a constant amount of sodium hydroxide with a smaller quantity of hydrazine or a shorter reaction time the amount of water‐soluble polymer (as a sodium salt) decreases and the amount of polymer in dispersion form increases. If a portion of the polymer in dispersion is coagulated with a portion of the polymer in the mother liquid, the yield of the depolymerized product is higher, but the average molecular weight is also higher than those of fraction I. The influence of the average contents of sulfur on the efficiency of the depolymerization is tested in polymers that contain 2.5 (i.e., 3) atoms of sulfur per segment of polymer. The result is that the depolymerization of the polysulfide polymer could be carried out without previous desulfurization, but the molecular weights of the products obtained with an equivalent quantity of hydrazine are much higher than those obtained by depolymerization of the disulfide polymer.
Thermal oxidative stability of poly‐p‐xylylenes
Authors: Nowlin T. E. , Smith Jr. D. Foss , Cieloszyk G. S.
Published: April 2003

The air oxidation of poly‐p‐xylylene films was studied at temperatures between 125 and 200°C. The oxidation kinetics were obtained from neutron activation (NA) oxygen analyses and infrared (IR) Spectroscopy. A correlation between the NA oxygen analyses and mechanical properties indicated that the amount of oxygen incorporated into these polymers before a significant degradation mechanical properties is about 1000 ppm for poly(dichloro‐p‐xylylene) and 5000 ppm for poly(monochloro‐p‐xylylene) or poly‐p‐xylylene. The activation energy for the oxidation of these polymers was about 30 kcal/mole. Long‐term‐use (100,000 hr) temperatures were also estimated for each of the poly‐p‐xylylenes studied. The 100,000‐hr maximum continuous‐use temperature is 112°C for poly(dichloro‐p‐xylylene), 72°C for poly(monochloro‐p‐xylylene), and 57°C for poly‐p‐xylylene.
Model reactions for stereochemistry of Ziegler‐Natta polymerization: Asymmetric hydroisomerization of α‐olefins by chiral titanium tetra‐alkoxides/tri‐isobutyl aluminum catalytic systems
Authors: Carlini Carlo , Chiellini Emo , Solaro Roberto
Published: April 2003

Homogeneous catalytic systems based on optically active low‐molecular‐weight and macromolecular titanium alcoholates and tri‐isobutyl aluminum were used in the isomerization and hydrogenation of chiral and prochiral olefins. The reactions performed in a nitrogen and hydrogen atmosphere show a different behavior in regard to reaction rate, composition of reaction mixture, and stereochemical control. The catalyst based on macromolecular titanium alcoholate displays lower activity and a varying influence on the stereochemical pathway with respect to the catalysts based on low‐ molecular‐weight alcoholates. The data obtained in both cases strongly support the absence of a stereocontrol by the growing chain in the stereoelective polymerization of racemic α‐olefins by Ziegler‐Natta catalysts based on optically active precursors. Finally evidence is provided in favor of the intermediate step responsible for asymmetric isomerization which does not occur via η‐allyl complex.
Free radical grafting of monomers to polydienes. III. Kinetics and mechanism of styrene grafting to polyisoprene
Authors: Cameron G. Gordon , Qureshi M. Younus
Published: April 2003

The radical‐induced grafting of styrene onto polyisoprene (PIP) in benzene solution at, 60°C was studied in rubber concentration (up to 0.5 monomer mole liter‐1) in which the polymerization of styrene shows ideal kinetics with no retardation by PIP. The proportion of polystyrene incorporated as graft is independent of the initiator (benzoyl peroxide) concentration and was found to be consistent with the kinetic expression derived by Cameron et al. The graft fraction of polystyrene which is higher than in the corresponding styrene‐polybutadiene system reflects the higher reactivity of PIP toward radicals. Azobisisobutyronitrile produces no graft copolymer in this system.
Interfacial sythesis of polyphosphonate and polyphosphate ester. VII. Temperature effects and reaction loci in polycondensations of hydroquinone with phenylphosphonic dichloride and 4‐methythiophenyl phosphorodichloridate
Authors: Millich F. , Lambing L. L.
Published: April 2003

Polyphosphate and polyphosphonate esters of molecular weights > 10,000 were synthesized by base‐promoted, liquid‐vapor and liquid‐liquid interfacial polycondensations of hydroquinone (HQ) with 4‐methylthiophenyl phosphorodichloridate (MTPP) and phenylphosphonic dichloride (PPD). The barium hydroxide‐initiated liquid‐vapor polycondensation of PPD and HQ in the temperature range of 15–95°C shows that [η] increases with reaction temperature and unfractionated yields exhibit a maximum at about 45°C. The analogous liquid‐vapor polycondensation of MTPP and HQ between 25 and 854C also shows a maximum yield at 45°C, whereas [η] decreases with increase in reaction temperature. The results are contrasted with temperature dependencies of base‐catalyzed, liquid‐liquid polycondensation of HQ with MTPP and PPD. A different insight is obtained by analyzing the temperature effects on fractionated products. The relative importance of degradative saponification reactions are ranked as attack on chain ester linkages > phosphorus chloride reactant > end groups of growing chains.
Polyimides derived from bis‐N‐hydroxyimides. II. Synthesis and properties of polyimide‐esters
Authors: Imajo Hidetomo , Kurita Keisuke , Iwakura Yoshio
Published: April 2003

Polycondensation of bis‐N‐hydroxyimides, N,N′ dihydroxypyromellitic diimide, and N,N′ ‐dihydroxybenzophenonetetracarboxylic diimide with dicarboxylic acid chlorides was carried out in dimethylacetamide in the presence of triethylamine to produce novel polyimide‐esters. The resulting polymers had inherent viscosities up to 0.27 dl/g. These polyimide‐esters and model compounds exhibited high reactivity toward nucleophiles such as aniline and n‐butylamine, which brought about rapid reductions in the viscosity of the polymers. These polymers were fairly resistant to organic solvents but soluble in m‐cresol. Thermal stability oft he polyimide‐esters was evaluated by thermogravimetry and their good heat‐resistant properties were confirmed.
Effects of ortho‐substituents on reactivities, tacticities, and ceiling temperatures of radical polymerizations of phenyl methacrylates
Authors: Otsu Takayuki , Yamada Bunichiro , Sugiyama Shigeru , Mori Shigeki
Published: April 2003

Radical polymerization and copolymerization of some o‐alkylphenyl methacrylates were carried out and the effect of the ortho‐substituents on the ability to homopolymerize, on the monomer reactivities, and on the ceiling temperatures of the monomers was studied. The effect of the substituent on tacticities and thermal stabilities of the polymers formed was also discussed. The ability to honiopolymerize and the monomer reactivity were considerably decreased by the introduction of the o‐substituent. 2,6‐Di‐tert‐butylphenyl methacrylate formed no methanol‐insoluble polymer at 60°C. On the basis of the tacticity determined it was noted that the o‐substituted phenyl methacrylates preferred syndiotactic addition in the propagation reaction less than did phenyl methacrylate or methyl methacrylate. The polymers formed from the o‐substituted monomers were thermally less stable than poly(phenyl methacrylate), and, consistent with this finding, ceiling temperatures of the o‐substituted phenyl methacrylates seemed to be lower than that of phenyl methacrylate. The effects observed were characteristic of the o‐substituents conformationally close to the carbon‐carbon double bond of the monomer or the carbon carrying the unpaired electron of the polymer radical.
Syntheses of vinyl polymers with pendant porphyrin dimers and their catalytic effects on photoreductions
Authors: Kamogawa Hiroyoshi , Inoue Hideaki , Nanasawa Masato
Published: April 2003

Vinyl copolymers with pendant porphyrin dimers were synthesized first by the dimerizations of chlorophyll‐α and protoporphyrin IX via the ethylenebisamide linkage, then by copolymerization of the vinylbenzyl esters of the resulting dimers with N‐vinylpyrrolidone or the esterification reaction of the dimers with chloromethylstyrene copolymers. Dimer‐pendant copolymers with vinyl pyrrolidone catalyzed photoredox systems in aqueous solutions more efficiently than the corresponding monomer analogs, presumably because of the interactions exerted between the two combined porphyrin rings, which are manifested in the hypochromic effect in absorption spectra. The effect of the central Mg atom in the protoporphyrin IX ring was also considerable.
Phenolic resins for solid‐phase peptide synthesis. III. Copolymerization of acrylonitrile and p‐acetoxystyrene and comparison of reactivity with styrene‐based resins
Authors: Ledwith A. , Rahnema M. , Gupta P. K. Sen
Published: April 2003

The copolymerization of acrylonitrile (r1) and p‐acetoxystyrene (r2) in bulk yields reactivity ratios r1 = 0.08 and r2 = 0.42. Crosslinked resins are readily obtained by a new type of precipitation copolymerization of acrylonitrile, p‐acetoxystyrene, and divinylbenzene. After deacetylation, the phenolic groups afford useful attachment sites for protected amino acids as a first stage in solid‐phase peptide synthesis. Reactivity of typical 10% functionalized polyacrylonitrile‐based resins is comparable to that of the more usual polystyrene‐based equivalents, although swelling characteristics of the two types of resin are very different.
Effect of unequal functional group reactivity and monomer masses on the polydispersity index in linear step polymerization
Authors: Ozizmir Ercument , Odian George
Published: April 2003

The Macosko‐Miller approach is used to obtain an expression for the polydispersity index for AA, BB, CC linear step polymerization system in which B and C are the same type of functional group. The dependence of the polydispersity index, as a function of the extent of reaction, on the monomer masses and on the relative reactivities of B and C groups toward A, is examined in detail.
Interaction of crosslinked polyvinylpyrrolidone with a homologous series of methyl orange derivatives in aqueous and nonaqueous solutions: Thermodynamics of the binding equilibria
Authors: Takagishi Toru , Naoi Yozo , Sonoda Ichiro , Kuroki Nobuhiko
Published: April 2003

The extent of binding of methvI orange, ethyl orange, propyl orange, and butyl orange by crosslinked polyvinylpyrrolidone was measured in all aqueous Solution. The first binding constants and the thermodynamic parameters accompanying the binding were evaluated. These values were compared with those of water‐soluble polyvinylpyrrolidone. The first binding constant, the absolute magnitude of ΔF°, and the value of ΔS° of the crosslinked polyvinylpyrrolidone are substantially larger than those of the water‐soluble product for any particular dye. These behaviors can be accounted for in terms of increased hydrophobic domains in the former and enhanced hydrophobic contribution in the binding process. Also the binding of the dye by the crosslinked polymer in a nonaqueous solvent, ethylene glycol, was measured to assess the contribution of hydrophobic interaction to the dye‐polymer complex formation in aqueous medium. It was found that the binding of butyl orange by the crosslinked polymer is suppressed in ethylene glycol and the contribution of entropy term to the free energy change in the aqueous environment is large compared with that in ethylene glycol. The significance of the hydrophobic of the hydrophobic interaction in the dye‐polymer association process is described.
Polymerization and copolymerization of 2‐phthalimidomethyll 1,3‐butadiene. II. Kinetic study of the polymerization of 1,3‐butadiene and of the copolymerization of 1,3‐butadiene with 2‐phthalimidomethyl 1,3‐butadiene initiated by bis‐(η3‐allyl nickel trifluoroacetate)
Authors: Borg‐Visse F. , Dawans F. , Maréchal E.
Published: April 2003

The kinetics of the polymerization of 1,3‐butadiene initiated by bis(η3‐allyl nickel trifluoroacetate) prepared in benzene was studied in methylene chloride at 40°C. The reaction is first order with respect to the monomer, second order with respect to the catalyst in contrast to the case in which solvent is benzene. We have shown that the presence of a polar molecule (fe, N‐methyl phthalimide) decreases the overall rate of polymerization. The apparent reactivity ratios for the system 2‐phthalimidomethyl 1,3‐butadiene (1)‐1,3‐butadiene (2) are r1 = 0.65 ± 0.006 and r2 = 0.48 ± 0.015.
Polymeric p‐benzoquinone–tin derivatives as thermal stabilizers for rigid poly(vinyl chloride). II. Evaluation of the stabilizing efficiency
Authors: Yassin Ahmady A. , Sabaa Magdy W.
Published: April 2003

The polymeric p‐benzoquinone‐tin derivatives obtained from the reaction of p‐benzoquinone with tin tetrachloride in the absence of solvent have been investigated as thermal stabilizers for rigid PVC at 200°C by measuring the rate of dehydrochlorination. The results reveal the greater stabilizing efficiency of the investigated products in relation to dibutyltin maleate and the basic lead stabilizers commonly used in industry. Evidence has been accumulated that the quinone and metallic elements (SnSn bonds) of the stabilizer participate in the stabilization process by trapping the radical intermediates of degradation and blocking the odd electron sites formed on the polymer chains. Although stabilizers with high quinone content provide greater stabilization in the early stages of degradation, their efficiency sharply decreases in subsequent stages. On the other hand, stabilizers of high tin content effectively prohibit the dehydrochlorination reaction at all stages of degradation. On an equivalent basis of metal content, the results clearly demonstrate the greater stabilizing efficiency of tin atoms when found in direct contact in the stabilizer molecule. The mechanism of stabilization suggested to account for the results obtained may be considered as additional evidence in support of the radical nature of the dehydrochlorination reaction.
Flow properties of epoxide prepolymers
Authors: Aleman Jose V.
Published: April 2003

The following characterstics of four molten epoxide prepolymers are described: flow curvepeculiarities, shift factor and temperature‐independent flow activation energy, shear stress and shear rate effects, and their graphical and analytical descriptions.
Studies on ceric–thiol‐initiated aqueous vinyl polymerization with particular reference to end groups in poly(methyl methacrylate)
Authors: Pramanick D. , Chatterjee A. K.
Published: April 2003

Ceric‐thiol systems are good initiators for the acid aqueous polymerization of some water‐soluble Vinyl monomers although not for styrene (in aqueous emulsion) and vinyl acetate. Thiols used are 2‐mercaptoethanol, thioglycolic acid, 2‐mercaptoethylamine hydrochloride, and L‐cysteine hydrochloride. The polymerization proceeds through a radical mechanism. End‐group analysis of poly(methyl methacrylate) obtained by initiation with various ceric‐thiol systems has been carried out using Palit's dye testes. Hydroxyl, carboxyl, and amine end groups (to the extent of about one per polymer molecule) were incorporated in poly(methyl methacrylate)s obtained by initiation with 2‐mercaptoethanol, thioglycolic acid, and 2‐mercaptoethylamine hydrochloride, respectively, each in combination with Ce4+ ions; both amine and carboxyl end groups were obtained using C4+/L‐cysteine hydrochloride initiator system. From the end‐group results, the initiating species have been identified and the initiation mechanism prooposed. The probable termination mechanism also has been discussed.
Peel adhesion and viscoelasticity of rubber–resin blends
Authors: Aubrey D. W. , Sherriff M.
Published: April 2003

Mixtures in various proportions of natural rubber (NR) and each of two tackifier resins, a poly‐β‐pinene and a modified pentaerythritol rosin ester, were used as the adhesive layer in joining a flexible polyester strip to a plane glass substrate. Measurements of the force required to peel the strip from the glass at a 90° angle were made over a range of pulling rates at several temperatures. Application of time‐temperature superposition enabled a master curve of (reduced) peel force versus (log) pulling rate at a standard temperature (296 K) to be obtained for each adhesive composition. The master curves showed, in increasing order of pulling rate, some or all of four different modes of peeling: (i) peeling with viscous adhesive response, (ii) peeling with rubbery response, (iii) oscillatory or slip‐stick peeling, and (iv) peeling with glassy adhesive response. In general, transitions between the different peeling modes were quite abrupt. Increase in concentration of tackifier resin caused displacement of the master curve toward lower pulling rates [an effect interpreted in terms of an increasing adhesive glass temperature (Tg)], and a superimposed displacement of the transition between peeling modes (i) and (ii) toward higher pulling rates‐an effect attributed to reduction in adhesive average molecular weight. The influence of the tackifier resin in modifying the viscoelastic characteristics of the adhesive was further demonstrated in a comparison of the peel force master curves with corresponding master curves of dynamic storage modulus.
Complex triarylsulfonium salt photoinitiators. I. The identification, characterization, and syntheses of a new class of triarylsulfonium salt photoinitiators
Authors: Crivello J. V. , Lam J. H. W.
Published: April 2003

Dilphenyl‐4‐thiophenoxyphenylsulfonium salts have been found to be more efficient cationic photoinitiators than the highly photoactive triphenylsulfonium salts. The former compounds were identified as by‐products produced in the preparation of triphenylsulfonium chloride from benzene, chlorine, sulfur monochloride, and aluminum chloride. Confirmation of the structure was made by NMR and UV spectroscopy as well as by independent synthesis. The photoinitiated cationic polymerization of cyclohexene oxide and other epoxy monomers was carried out to demonstrate the higher efficiency of diphenyl‐4‐thiophenoxysulfonium hexafluoroarsenate as compared to the corresponding triphenylsulfonium salt.
Complex triarylsulfonium salt photoinitiators. II. The preparation of several new complex triarylsulfonium salts and the influence of their structure in photoinitiated cationic polymerization
Authors: Crivello J. V. , Lam J. H. W.
Published: April 2003

Complex triarylsulfonium salts bearing the thiophenoxy chromophore have been synthesized. The effects of the position of attachment of the thiophenoxy group on the rate of photolysis and in the photoinitiated cationic polymerization of various monomers have been investigated. Other salts in which the thiophenoxy group has been oxidized to the sulfoxide and the sulfone also were prepared to examine the effects of the oxidation state of the sulfur‐bearing chromophore on the efficiencies in photoinitiated cationic polymerization. All complex salts having extended conjugation not impeded through positional isomerization or blocked through oxidation of the thiophenoxy chromophore are more reactive than the corresponding triphenylsulfonium salts in cationic polymerization.
Phase transfer‐catalyzed nitromercuration of diene polymers
Authors: Chien J. C. W. , Kohara T. , Lillya C. P. , Sarubbi T. , Su B‐H. , Miller R. S.
Published: April 2003

A mild, efficient method of nitrating olefins was described recently by Corey and Estreicher. Application of their procedure to diene polymers failed because of the insolubility of the hydrophobic polymer in the aqueous nitromercuration regent. Use of water‐immiscible organic cosolvents gave slow nitromercuration with substantial formation of nitrite esters. To overcome these problems a nonaqueous phase transfer‐assisted method of rapid selective nitromercuration of diene polymers was developed.
Photochemical degradation of blends of polystyrene and poly(2,6 ‐dimethyl‐1,4‐phenylene oxide)
Authors: Jensen J. P. Tovborg , Kops J.
Published: April 2003

Blends of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) that cover the entire compositional range have been subjected to the action of singlet oxygen from microwave discharge, dye‐sensitized reaction, and photochemical oxidation. With the applied analytical technique, which consisted of infrared (IR) analysis, including ATR technique and a spectroscopic method combined with chemical analysis for hydroperoxide groups, it was not possible to detect any effect of the singlet oxygen treatment. For that reason singlet oxygen does not appear to be important to the initiation of the photooxidation of these blends. In connection with photochemical oxidation the interaction observed between the two components probably involves energy transfer from PS to PPO. This interaction results in the enhancement of reactions in PPO that lead to greater carbonyl group formation and crosslinking. Simultaneously, the probability of chain scission in the PS is lowered with increased PPO content, found by determining the changes in the molecular weights.
On the rate of soapless emulsion polymerization of methyl methacrylate
Authors: Arai Masahiko , Arai Kunio , Saito Shozaburo
Published: April 2003

The rate of soapless emulsion polymerization is studied experimentally and theoretically. The soapless emulsion polymerization of methyl methacrylate (MMA) in water is carried out with potassium persulfate as initiator. It is shown that the soapless emulsion polymerization of MMA gives different time‐conversion and time‐average molecular weight curves from those of bulk and emulsion polymerizations. Comparing the experimental results with those of the other types of polymerization, features of the rate of soapless emulsion polymerization are discussed and a kinetic model is proposed to apply the soapless emulsion polymerization of MMA in water. The experimental results can be well expressed by this model.
Synthesis and characterization of polymers of 1,4‐hexadienes
Authors: Lal Joginder , Hanlon Thomas L. , Chen Hung Yu
Published: April 2003

The homopolymerization of trans‐1,4‐hexadiene, cis‐1,4‐hexadiene, and 5‐methyl‐1,4‐hexadiene was investigated with a variety of catalysts. During polymerization, 1,4‐hexadienes undergo concurrent isomerization reactions. The nature and extent of isomerization products are influenced by the monomer structure and polymerization conditions. Nuclear magnetic resonance (NMR) and infrared (IR) data show that poly(trans‐1,4‐hexadiene) and poly(cis‐1,4‐hexadiene) prepared with a Et3Al/α‐TiCl3/hexamethylphosphoric triamide catalyst system consist mainly of 1,2‐polymerization units arranged in a regular head‐to‐tail sequence. A 300‐MHz proton NMR spectrum shows that the trans‐hexadiene polymer is isotactic; it also may be the case for the cis‐hexadiene polymer. These polymers are the first examples of uncrosslinked ozone‐resistant rubbers containing pendant unsaturation on alternating carbon atoms of the saturated carbon‐carbon backbone. Polymerization of the 1,4‐hexadienes was also studied with VOCl3‐ and β‐TiCl3‐based catalysts. Microstructures of the resulting polymers are quite complicated due to significant loss of unsaturation, in contrast to those obtained with the α‐TiCl3‐based catalyst. In agreement with the literature, there was no discernible monomer isomerization with the VOCl3 catalyst system.
Polymerization of aromatic olefins in the system liquid sulfur dioxide–percompounds: The nature of the initiation
Authors: Gomes Ailton De Souza , Filho Odyr Do Coutto , Akcelrud Leni , Santos R.
Published: April 2003

Indene, α‐methylstyrene, and styrene were polymerized in liquid sulfur dioxide in the presence of hydroperoxides and peracids. With indene, depending on the molar ratio of the monomer to sulfur dioxide, homopolymerization and polysulfone formation could be observed. With α‐methylstyrene spontaneous polymerization in liquid sulfur dioxide was observed; the addition of hydroperoxide increased the yield and molecular weight. Styrene was polymerized in this solvent with hydroperoxides and peracids, the latter being a more effective initiator. The initiation in these systems could be explained by the formation of a mixed anhydride between sulfuric acid and m‐chlorobenzoic acid.
Asymmetric polymerization of triphenylmethyl methacrylate by optically active anionic catalysts
Authors: Okamoto Yoshio , Suzuki Koichi , Yuki Heimei
Published: April 2003

Triphenylmethyl methacrylate (TrMA) was polymerized with two types of asymmetric anionic catalyst, lithium (R)‐N‐(1‐phenylethyl)anilide (LiAn) and (‐)‐sparteine–butyllithium complex (Sp–BuLi), at −78°C. Both catalysts yielded optically active polymers. The polymers obtained with LiAn in toluene and tetrahydrofuran (THF) showed specific rotations [α] of from −50° to −90° (in THF). The [α] of the polymer obtained with Sp–BuLi in toluene was positive and increased with polymer yield reaching above +300°s, whereas the polymer obtained in THF showed a low [α] (ca. +7°). Gel permeation chromatograms of both polymers obtained with LiAn and Sp–BuLi in THF exhibited rather narrow molecular weight distributions, whereas those obtained in toluene showed at least two or three components with markedly different molecular weights. The circular dichroism (CD) spectrum of the polymer obtained with Sp–BuLi showed strong positive peaks at 208 and 232 nm and a weak band at 250–280 nm; the polymer produced with LiAn showed a similar spectrum with opposite sign. The poly(methyl methacrylate)s derived from these poly(TrMA)s were highly isotactic but showed negligible rotations ([α] ± 2° in toluene). The polymer of high molecular weight showed clear polarization under a polarizing microscope and the low polymer obtained with LiAn appeared to show flow birefringence in chloroform at room temperature.
Solvating properties of certain polymeric ethers
Authors: Panayotov I. M. , Dimov D. K. , Tsvetanov Ch. B. , Stepanov V. V. , Skorokhodov S. S.
Published: April 2003

The formation of two kinds of solvation complex of poly(ethylene oxide), polydimethoxyethylene, and polydioxene with some alkali derivatives of fluorene in dioxane was found, differing in the ionic species of the fluorenyl metal in the complex. Additional evidence was found for the existence of peripherally solvated ion pairs of fluorenyllithium, ‐sodium, and ‐potassium. It was shown that polydimethoxyethylene and polydioxane interact with different cations in a different manner. The complexing ability of poly(ethylene oxide) and polydioxane with respect to fluorenyllithium, ‐sodium, and ‐potassium, and of polydimethoxyethylene for fluorenyllithium, was proved to be stronger than that of their monomer analogs—dimethoxyethane and dioxane. This was explained by the effect of the polymer chain.
Freeze‐dried cellulose acetate membrane fine structure observation
Authors: Kakuta A. , Kuramoto M. , Ohno M. , Kushida H. , Tanioka A. , Ishikawa K.
Published: April 2003

A freeze‐dried cellulose acetate membrane fine structure was observed with an ultrathin sectioning electron microscope. The fine structure for the top surface in this membrane could be seen by lead citrate staining ultrathin sectioning. This network structure was observed among pores, which existed in porous substrate. The pore diameter in the top surface was about 50 Å, a value that agrees approximately with the value estimated by gas permeation.
The kinetics of condensation of phenolic polyflavonoid tannins with aldehydes
Authors: Rossouw D. du T. , Pizzi A. , McGillivray G.
Published: April 2003

The rate constants and free energies of activation of the acid‐and base‐catalyzed reactions of floroglucinolic and resorcinolic flavonoid A rings of pine and wattle tannins, respectively, as well as the model compounds resorcinol, floroglucinol, and catechol, with formaldehyde, acetaldehyde, propionaldehyde, n‐butyraldehyde, isobutyraldehyde, and furfural, were obtained. Second‐order kinetics were found to fit these reactions. Indication and proof of the existence of unstable aldehyde ether bridges and their fast rearrangement at ambient temperature to alkyl bridges for fast‐reacting phenols or phenolic compounds, such as tannins, were obtained for the first time. The dependence of the reaction kinetics on the concentration of OH‐ catalyst was investigated. Anomalies in the behavior of wattle tannin with aldehydes and n‐butyraldehyde with phenols were observed and partially explained. The results led to a slightly different interpretation of the wattle tannin flavonoid structure.