bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractRadical 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

AbstractVinyl 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.
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

AbstractCeric‐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

AbstractMixtures 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

AbstractDilphenyl‐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

AbstractComplex 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

AbstractA 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

AbstractBlends 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

AbstractThe 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

AbstractThe 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

AbstractIndene, 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

AbstractTriphenylmethyl 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

AbstractThe 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

AbstractA 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

AbstractThe 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.
Radiation‐induced polymerization at high dose rate. III. Isoprene in bulk
Authors: Hayashi Kanae , Tachibana Michinori , Okamura Seizo 
Published: April 2003

AbstractRadiation‐induced polymerization of isoprene in bulk state was studied at 25°C in a wide dose rate range. Variations of the rate of polymerization and molecular weight of the products were essentially the same as those observed in the monomers which were capable of both radical and cationic polymerizations. At low dose rate, 7.0‐230 rad/sec, radical polymerization took place. At high dose rate, 8.8 × 103‐2.2 × 105 rad/sec, radical and cationic polymerizations took place concurrently. The average molecular weight of the high‐dose‐rate product was about 850, independent of dose rate. The microstructure of the products at high dose rate consisted mainly of trans‐ 1,4 units with only about 7% of cis‐ 1,4 and 10% of 3,4‐vinyl units. The residual unsaturation in the high‐dose‐rate products was 90%. Decreases in cis units and residual unsaturation at high dose rate were accounted for by the change in predominant mechanism of polymerization with dose rate.