bluuebunny/crossref_metadata_2025 huggingface dataset:
13C‐NMR spectral studies on the distribution of substituents in some cellulose derivatives
Authors: Takahashi Shin‐Ichi , Fujimoto Tetsuya , Barua Basu M. , Miyamoto Takeaki , Inagaki Hiroshi
Published: April 2003

13C‐NMR spectra of trityl cellulose (Tr‐Cell), tosyl cellulose (Ts‐Cell), cellulose S‐methyl xanthate (Cell‐M‐Xan), and cellulose formate (CF) in dimethylsulfoxide‐d6 were analyzed at 50.4 MHz. It was found that the distribution of substituents in the anhydroglucose units of these cellulose derivatives can be estimated from their ring carbon spectra. The results showed that (i) in Tr‐Cell having degree of substitution (DS) lower than 1, the hydroxyl groups at C‐6 carbon position are selectively tritylated, (ii) in the case of Ts‐Cell, the difference in the relative DS value among three different types of hydroxyl groups is not large, although the relative reactivities of hydroxyl groups toward tosylation decrease in the order C‐6 > C‐2 > C‐3, (iii) in Cell‐M‐Xan, the hydroxyl groups at C‐3 carbon position are mainly substituted, and (iv) the ease of formylation is C‐6 > C‐2 > C‐3. The 100.8 MHz 13C‐NMR spectra of O‐methyl cellulose (MC) revealed that the reactivity order in commercial MC prepared from alkali cellulose is C‐6 ⋍ C‐2 > C‐3. Concerning MC, its water solubility was also discussed in terms of the distribution of substituents along the cellulose chain.
Aqueous polymerization of methyl methacrylate catalyzed by corundum and characterization of the obtained polymers
Authors: Moustafa A. B. , Abdel‐Latif Z. H. , Amer L. I. , Sayyah S. M.
Published: April 2003

The aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bi‐sulfite as initiator in the absence and presence of corundum (Al2O3). It was found that corundum has a catalytic effect on the polymerization reaction. The polymers obtained in the presence of corundum were found to have a wider molecular weight distribution than in its absence; this was deduced by thin‐layer chromatographic analysis in a binary mixture (benzene: methanol 1:1.5 by volume) at 25°C. The apparent energy of activation was calculated between 40 and 50°C, and was found to be 4.50 × 104 and 1.70 × 104 J/mol in the absence and presence of 0.5 g corundum (type 600 grit)/105 mL of the reaction mixture, respectively.
XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process
Authors: Takahagi T. , Shimada I. , Fukuhara M. , Morita K. , Ishitani A.
Published: April 2003

In the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x‐ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π‐electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.
Effect of solvent for vinyl acetate polymerization on microstructure of poly(vinyl alcohol)
Authors: Imai Kiyokazu , Shiomi Tomoo , Oda Naonobu , Otsuka Hideo
Published: April 2003

The solution polymerization of vinyl acetate was carried out in several solvents at 0 to 100°C, using 2,2′‐azobisisobutyronitrile as initiator. For the resulting poly(vinyl alcohol) (PVA), iodinecoloration, 1,2‐glycol structure and tacticity were observed. The pentad tacticity of PVA was estimated from its methine carbon spectra by means of 13C‐FTNMR spectrometer. Iodine‐coloration ability of PVA varied markedly with the type of polymerization solvent and decreased in the following order: phenol > aq. phenol > methyl alcohol > ethyl acetate > DMSO, ethylene carbonate. The syndiotactic fraction in PVA also decreased with polymerization solvent in the same order as that of iodine coloration, while 1,2‐glycol content of PVA was not almost affected by polymerization solvent except for phenol and aq. phenol. In solution polymerization performed, effect of polymerization temperature on tacticity was less than that of solvent.
Plasma‐substrate interaction: Effect of volatile oligomers in silicone rubber on plasma polymerization of fluorine‐containing monomers
Authors: Yeh Y. ‐S. , Yasuda H.
Published: April 2003

The cause of the conspicous Si content consistently observed on plasma polymers deposited on silicone rubber was investigated in this study. Plasma polymers of tetrafluoroethylene and of hexafluoroethane were deposited on the inside surface of Silastic tubings with and without oligomers by using a semicontinuous plasma polymerization reactor. This tube coating reactor is unique in the sense that the only surface which interacts with the plasma is the substrate surface (i.e., inside wall of tubing) and that plasma polymerization occurs in a very small volume of 3.3‐mm‐I.D. and 2‐cm‐long section of tubing at any given time. These two factors render the reactor a suitable system for the investigation of plasma‐substrate surface interaction. Silastic tubings free of oligomers were prepared by extracting the tubings as received with distilled n‐hexane for 3 h which yielded a 3% weight loss. It was found that the conspicuous Si content noted previously was not occasioned by the migration of oligomers through the plasma polymers but was caused by the redeposition of plasma copolymers formed from a mixture of the feed‐in monomer and the silicon‐containing volatile components evolved from the silicone rubber when exposed to the plasma. The presence of Si‐containing compounds in the plasma evidently interfered with the plasma polymerization of tetrafluoroethylene and hexafluoroethane. Without volatile oligomers (the extracted samples), ESCA analysis indicated that the plasma polymers contained large amounts of CF3, CF2, and CF moieties, just like most typical plasma polymers of these monomers deposited on nonreactive substrates. With the presence of volatile oligomers, the fluorine content decreased drastically and a significant increase of oxygen‐containing and silicon‐containing moieties was observed. The influence of the volatile oligomers in the substrate on the balance between ablation and polymerization in plasma polymerization and its energy input level dependence (manifested by W/FM) were studied as well. The results were also discussed in relation to the bicyclic rapid step‐growth polymerization mechanism.
Use of cyclohexanone oxime as an oxidant in redox polymerization: Kinetics of oxidation and polymerization
Authors: Varaprasad D. V. P. R. , Mahadevan V.
Published: April 2003

Cyclohexanone oxime was employed as an oxidant in combination with Vanadium (III) as a redox initiator system for the polymerization of AN and MMA. Kinetics were investigated in aqueous sulphuric acid medium and mechanisms for oxidation and polymerization were proposed. Michaelis–Menten kinetics were evident from the rates of oxidation with protonation of oxime being the noncompetitive complexation. A mechanism involving monomer in the initiating radical production step and mutual termination of growing radicals was proposed to account for the fractional orders in the initiator concentration and the monomer exponents higher than unity.
Molten bisphenol‐A polycarbonate‐poly(ethylene terephthalate) blends. I. Identification of the reactions
Authors: Godard P. , Dekoninck J. M. , Devlesaver V. , Devaux J.
Published: April 2003

This paper is devoted to the study of the reactions taking place in molten bisphenol‐A polycarbonate‐poly(ethylene terephthalate) mixtures. The analysis of the reaction products by infrared, proton and nuclear magnetic resonance spectroscopy, and by thermogravimetric analysis shows that the main reaction is an exchange reaction identical to that occurring in bisphenol‐A polycarbonate‐poly(butylene terephthalate) mixtures. However, some other reactions consecutive to this exchange reaction also take place, probably resulting from the instability of the ethylene carbonates produced by transesterification.
Synthesis and characterization of uracil base grafted polyacrylamides as polynucleotide analogs
Authors: Overberger C. G. , Ferng W. B.
Published: April 2003

In conjunction with the previous studies of the adenine base grafted polyacrylamides, the uracil base grafted polyacrylamides and their monomer model compounds were prepared. In this case, however, an amine bond instead of an amide bond was used to attach the pendants onto the amino active site. A wider range of grafting efficiency (45–90%) and a smaller hypochromic effect were observed. This increase in grafting efficiency is responsible for the observed increase in percent hypochromicity. The reactivity ratios of the monomer model compounds with complementary bases, e.g., uracil and adenine, were estimated from a Finemann–Ross plot. Continuous mixing experiments involving the synthetic polyacrylamides with complementary bases suggested that polymer–polymer mixtures form base‐paired complexes that stabilize the stacked conformation only in neutral aqueous solution. Electrostatic repulsion prèvented such stability in acidic or alkaline aqueous solution. The collective information from NMR, UV, and CD spectra suggested that uracil based grafted poly(2‐amino‐2‐methylpropyl)acrylamide (PDMPA) and poly(2‐amino‐2‐methylbutyl)acrylamide (PDMBA) exist in limited ordered conformation.
Kinetics and mechanism of polymerization of acrylonitrile by peroxomonosulphate
Authors: Manivannan Gurusamy , Maruthamuthu Pichai
Published: April 2003

The kinetics of polymerization of acrylonitrile initiated by peroxomonosulphate (PMS) has been carried out in the temperature range 45–60°C at constant ionic strength of 0.50 mol dm−3 under deaerated conditions. The rate of polymerization Rp has been investigated at various concentrations of monomer and initiator. The effects of [monomer], [initiator], [H+], ionic strength, temperature, and reducing agents (organic and inorganic substrates) on the rate of polymerization have been observed. Activation energy was found to be 15.2 kcal mol−1.
Vapor synthesis of high‐activity catalysts for olefin polymerization
Authors: Ittel Steven D. , Mulhaupt Rolf , Klabunde Ulrich
Published: April 2003

Vaporization of MgCl2 and other metal halides results in monomeric gas‐phase species. Cocondensation of these species with organic diluents such as heptane yields highly activated solids which are precursors to MgCl2 supported “high‐mileage” catalysts for olefin polymerization. These catalysts, prepared by treatment with TiCl4 followed by standard activation with aluminum alkyls display high activity for ethylene and propylene polymerization. MgCl2 can also be evaporated into neat TiCl4 to give a related catalyst. The concentration of MgCl2 in the diluent affects catalyst properties as does the nature of the diluent. TiCl3, 3TiCl3 · AlCl3, VCl3 and other metal halides are subject to similar activation.
Association of copolymers of methacrylic acid and 4‐vinylpyridine in comparison with an intermacromolecular complex of poly(methacrylic acid) with poly(4‐vinylpyridine)
Authors: Abe Koji , Senoh Saburo
Published: April 2003

Solution properties of copolymers [C(MA‐Py)x] of methacrylic acid and 4‐vinylpyridine and intermacromolecular complexes of poly(methacrylic acid) (PMAA) and poly(4‐vinylpyridine) (PVP) in the presence or absence of a proton‐accepting water‐soluble polymer such as poly(ethylene glycol) (PEG) in water/methanol mixed solvent are studied by potentiometric titration, turbidity and viscosity methods. These copolymers behave like polyampholytes and their solubilities are strongly dependent with pH changes. The pH regions where they are precipitated around their isoelectric points are narrower than those of the intermacromolecular complex of PMAA with PVP. The polyampholyte can form an intermacromolecular complex with PEG in acidic solution but this complex is soluble in the medium.
Hydrolytic polycondensation of alkoxysilanes and modification of polymerization reactions
Authors: Yoldas Bulent E.
Published: April 2003

Polymers having oxide network chains are produced by hydrolytic polycondensation of metal alkoxides and alkoxysilanes. Molecular morphology and molecular size distribution of these inorganic polymers are strongly affected by certain nonchemical parameters. Included among these parameters is the molecular separation of interacting species during the polymerization. There is strong evidence that the molecular size expansion occurs by two distinct processes: initially by a gradual “growth” process, and later by “recombination” of high‐molecular weight species. The later process often leads to a bi‐modal molecular size distribution. The concentration of water‐rich siloxane solutions leads to significant molecular size expansion by further oxide network formation. No similar polymer size growth occurs during the concentration of alcohol based solutions. This difference in the polymeric activities can be related to the difference in the terminal bond under the two different conditions.
Synthesis of copolyamides based on ε‐caprolactam and AH salt in the presence of cationic resin
Authors: Nevrekar Nitin B. , Joshi K. A.
Published: April 2003

Copolyamides based on ε‐caprolactam and AH salt were prepared by copolymerization of various combinations of ε‐caprolactam and AH salt in the presence of a cationic resin. In terms of adhesivity towards metals they have proved their superiority over nylon 6, nylon 6, 6, and the copolyamides of ε‐caprolactam and AH salt, prepared in presence of water. Adhesive property of the copolyamide was found to be increased with increasing proportion of AH salt in the combinations. ε‐Caprolactam (1 part) and AH salt (5 parts) in presence of a cationic resin (0.55%) were copolymerized to give a best performing copolyamide: yield 93%, mp 232°C, relative viscosity 2.42, and shear tensile strength 620 kg/in.2
Polymerization of surface‐active monomers. II. Polymerization of quarternary alkyl salts of dimethylaminoethyl methacrylate with a different alkyl chain length
Authors: Nagai Katsutoshi , Ohishi Yoshiyuki
Published: April 2003

The cationic monomers (CNBr), obtained by quarternization of dimethylaminoethyl methacrylate with n‐alkyl bromide containing varying carbon number (N = 4, 8, 12, 14, and 16) were polymerized with radical initiators in water and various organic solvents. The degree of polymerization of the resulting polymers was determined by GPC measurements on poly(methyl methacrylate) samples derived from them. The rate of polymerization of the micelle‐forming monomers (N = 8, 12, 14, and 16) in water increases with increasing a chain length of alkyl group, whereas it is little dependent on N in isotropic solution in dimethylformamide. The data on the degree of polymerization for the polymers of C4Br, C8Br, and C12Br show that the polymerization of C12Br with azo initiators in water and benzene gives polymers with a very high degree of polymerization. The results obtained here suggest that highly developed or relatively rigid, aggregated structures of monomers in solution are responsible for the formation of the polymers with a very high degree of polymerization, in addition to an enhanced rate of polymerization. Also considered are the relation of the molecular weight of poly(C12Br) to the viscosity data in chloroform and methanol.
Synthesis of poly(styrene‐tetrahydrofuran‐2‐methyl‐2‐oxazoline) triblock and graft copolymers
Authors: Ishizu Koji , Fukutomi Takashi
Published: April 2003

Poly[styrene (ST)‐tetrahydrofuran (THF)‐2‐methyl‐2‐oxazoline(MeOz)] triblock and graft copolymers were prepared by ionic polymerizations. Poly(ST‐THF) graft copolymers were synthesized by coupling of ST‐4‐vinylpyridine (4VP) copolymer with a large excess of PTHF dication. The ion coupling of PST dianion with PTHF dication was accompanied by the side reaction (abstraction of α proton of oxonium ion). After tosylation of terminal hydroxyl groups of PTHF blocks, cationic copolymerizations of MeOz with poly(ST‐THF) block and graft copolymers were carried out, and characteristics of produced copolymers were investigated in some detail.
Elementary reactions of the emulsions polymerization of styrene with the localization of radical formation acts at the interface
Authors: Ivanchev S. S. , Pavljuchenko V. N. , Byrdina N. A.
Published: April 2003

The localization of radical formation acts at the interface achieved by the application of specially prepared surfactant initiators, fixation of initiating sites on the surface of seed latex particles by covalent bonds, or by redox initiating systems were experimentally studies. It is ascertained that the fixation of the initiator of polymerization at the interface of the emulsion system brings about a change of the kinetic parameters of its decomposition—an increase in the decomposition rate and decrease in the initiation efficiency. The experiments (measurements of chain propagation rate) demonstrated that the nature of emulsifying agent and initiator has no effect on the chain propagation acts. The kinetics of the chain termination depends on the properties of the emulsion system that is revealed in the dependence of chain termination constants on the type of initiator and the diameter of latex particles. These effects are supposed to be explained by influence of the colloid and chemical parameters of the reaction system on the conformation entropy of the growing macroradicals; and the low values of the chain termination constants (102–104 L mol−1 s−1) are due to the higher activation energy of chain termination for the emulsion polymerization.
Polymer‐supported bases. 5. Acetylation of linalool with acetic anhydride using dialkylaminopyridines attached by spacer chains to polystyrene resins
Authors: Tomoi Masao , Goto Makio , Kakiuchi Hiroshi
Published: April 2003

The acetylation of linalool with acetic anhydride was carried out in the presence of polystyrene‐bound aminopyridines and triethylamine. The catalytic activity of the immobilized aminopyridines increased with decreasing percentage of ring substitution and with increasing spacer‐chain length. The increased activity is attributed to an increase in the amount of aminopyridine units complexed with acetic anhydride. The acetylation could be successfully conducted by use of a mixture of the immobilized aminopyridines and polymer‐supported benzyldiethylamine, which effectively trapped acetic acid formed in the reaction system.
Soluble alkyl substituted polygermanes: Thermochromic behavior
Authors: Miller R. D. , Sooriyakumaran R.
Published: April 2003

We have prepared a number of high molecular weight, soluble, symmetrical dialkyl substituted germanium homopolymers and germanium‐silicon copolymers. In solution, the absorption of the homopolymers was ∼ 20 nm red shifted from the crossponding silicon derivatives. This was somewhat unexpected based on theoretical predictions and has been rationalized on the basis of conformational arguments. In the solid state, samples of poly(di‐n‐hexylgermane) and poly(di‐n‐octylgermane) are strongly thermochromic. The effect is attributed to the conformational locking of the backbone which is caused by the crystallization of the side groups. In this regard, the germanium derivatives behave similarly to the corresponding silicon polymers, and the convergence of the long wavelength absorptions for both types of polymers is consistent with theoretical predictions. The germanium‐silicon copolymers are also strongly thermochromic, but the long wavelength absorption is somewhat blue shifted (8 nm) from the respective homopolymers. As expected, the new germanium homo and copolymers are quite sensitive to light and readily undergo chain scission to produce lower molecular weight materials.
Thermal decomposition behavior of mono‐aminimides and their application to polymerization of epoxide
Authors: Inubushi Shinzo , Ikeda Tomiki , Tazuke Shigeo , Satoh Tasuku
Published: April 2003

Mono‐aminimide compounds [N,N‐dimethyl‐N‐(2‐hydroxypropyl)‐amine‐N′‐propionimide (1), trimethylamine valerimide (2), and trimethylamine benzimide (3)] were found to exhibit different thermal decomposition behaviors and polymerization efficiencies for an epoxide (phenyl glycidyl ether, PGE). The thermal decomposition rate of aminimides at 150°C decreased in the order 1 > 2 > 3. It seemed that hydrogen bonding enchanced the decomposition rate, and the resonance effect induced by the phenyl group suppressed the decomposition. 1 was thermolyzed to give isocyanate and tertiary aminoalcohol, which subsequently reacted with each other to give isocyanate and tertiary aminoalcohol, which subsequently reacted with each other to give urethane. When 2 was heatted, the isocyanurate generated from 2 remained intact. On heating of 3, we observed the formation of triphenyl isocyanurate. PGE reacted with those aminimides and gave different products depending on their thermolyzed products. Equimolar mixtures of isocyanate, tertiary amine, PGE were used in the model reactions, and the thermal reaction between the expected decompostion products of aminimides was investigated in the presence and absence of PGE. The rate of PGE consumption was in the order PGE + 2 > PGE + 1 > PGE + 3. It is clear that the formation of urethanes and oxazolidone derivatives affects the polymerization process.
Effects of linking groups in fluorinated aromatic polyamides
Authors: Whang W. T. , Pearce E. M.
Published: April 2003

Based on dynamic thermogravimetric analysis (TGA) of fluorinated aromatic polyamides, we found that substituting terephthaloyl units for isophthaloyl units usually increased the thermal stability of the polymers. In contrast, the first steps of thermal degradation of poly(5,5′‐sulfonyl‐2,2′‐difluoro‐diphenyl terephthalamide) (2,2′‐DIF‐PSDPT) and poly(5,5′‐sulfonyl‐2,2′‐difluorodphenyl isophthalamide)(2,2′‐DIF‐PSDPI) followed almost the same curve. This was attributed to the relative flexibility of the SO2 group, and also to the activating effect on the dehydrofluorination reaction, which was believed to be the first step of the degradation of the ortho‐fluorinated aromatic polyamides, , resulting in the formation of benzoxazole groups, , on the polymer backbone. With fluorinated aromatic polyamides having ortho fluorine to the amide nitrogen, the electron releasing CH2 group deactivated the nucleophilic substitution of the dehydrofluorination reaction and the electron withdrawing group SO2 activated the reaction, so that the onset degradation temperatures of the fluorinated aromatic units R in followed the order:
Photodegradation of poly(vinylacetophenone). II. Short‐wave photolysis
Authors: Weir N. A. , Arct J.
Published: April 2003

The photodegradation of films (2 × 10−4 cm thick) of poly(vinyl‐acetophenone) [poly(4‐acetylstyrene)] exposed to 254 nm radiation under high vacuum at 25 ± 1°C was studied. The principal gaseous product was H2, but CH4, C2H6, and smaller amounts of acetaldehyde and CO were also formed. The photochemistry more closely resembles that of other substituted styrene polymers than that occuring on the long wave (λ > 300 nm) irradiation of the polymer in that the principal initial processes involve fissions of bonds in the β‐position to the phenyl chromophores. Studies of a deuterated analogue (D3 acetyl) indicate that H‐abstractions occur from the polymer and also that fission of CH bonds in the acetyl group does not occur. The polymer undergoes rapid cross linking. Mechanisms of the various primary and secondary processes are discussed.
Crosslinking of polyaromatic ether‐ketones with biphenylene derivatives
Authors: Ogawa Takeshi , Marvel C. S.
Published: April 2003

Polyaromatic ether‐ketones prepared from isophthaloyl dichloride, diphenyl ether, and various amounts of biphenylene and its derivative, were compressed to films under various conditions, and their crosslinking behaviors were studied. Although strong and flexible films could be obtained from low melting crosslinkable polymers, the low molecular weight polymers, which melt below 300°C, decompose at the biphenylene ring opening temperature of over 290°C, giving films full of gas bubbles. The addition of metal complexes to decrease the biphenylene ring opening temperature did not improve the film quality, although gas bubbles could be avoided. The strong and flexible films were amorphous, and the brittle films were mixtures of crystalline and amorphous polymers.
Polymerization of vinyl chloride in the presence of modified Ziegler–Natta catalysts comprising long chain organoaluminum compounds
Authors: Florjanczyk Zbigniew , Kuran Witold , Sitkowska Jadwiga , Ziółkowski Andrzej
Published: April 2003

Polymerization of vinyl chloride in the presence of systems containing a transition metal compound/Lewis base and an organoaluminum compound of a different length of carbon chain have been carried out. The influence of the structure and the concentrations of particular components on the polymerization yield and molecular weight of the products has been determined. The polymerization of vinyl chloride proceeds according to the free radical mechanism, and the effectiveness of such types of initiators decreases with an increase in the length of the substituent chain in the organoaluminum chain. When using ethyl derivatives, the maximum degree of vinyl chloride conversion is about 75%, and for polystyryl or polyisoprenylaluminum of an average polymerization degree of 50–100, the conversion did not exceed 0.5%. The maximum polymerization degree of vinyl chloride in block copolymers containing polyisoprenyl or polystyryl units was 90–300.
Poly(α‐methylstyrene‐b‐styrene) by a cationic mechanism
Authors: De Souza Gomes Ailton , Soares Bluma Guenther
Published: April 2003

Block copolymers of styrene and α‐methylstyrene were obtained by a cationic mechanism involving a single‐step addition in the m‐chloroperbenzoic acid/liquid sulfur dioxide system. This result was possible because of the difference in the reactivity of these monomers in the temperatures of −40°C, −60°C, and −78°C. Under these temperature conditions α‐methylstyrene is more reactive than styrene. The composition of the block copolymers was determined by NMR and TGA analysis in fractionated samples.
Equilibrium copolymerization of tetrahydrofuran‐3‐methyltetrahydrofuran
Authors: Guzman J. , Riande E.
Published: April 2003

The bulk cationic copolymerization of tetrahydrofuran and 3‐methyl‐tetrahydrofuran was studied at 0°C with acetylhexafluoroantimonate as initiator. The experimental equilibrium concentrations of both monomers were determined in all the intervals of composition, and the results obtained were compared with those calculated by different methods developed to study copolymerization systems in which depropagation reactions play an important role. In particular, very good agreement between calculated and experimental values was obtained by using Monte Carlo methods of simulation that allow the determination of the unknown cross‐propagation and cross‐depropagation rate constants, a necessary condition to calculate the equilibrium monomer concentrations.
Synthesis of polynucleotide analogs by grafting optically active nucleic acid base derivatives onto polyethylenimine
Authors: Overberger C. G. , Chen C. C.
Published: April 2003

Polynucleotide analogs with a polyethylenimine backbone and optically active thymine‐ and adenine‐containing pendants and their model compounds were synthesized. The pendants were prepared by the addition reaction of the nucleic acid base to ethyl crotonate. The ammonium salt of 3‐(adenin‐9‐yl)butyric acid was employed to replace its free acid for the formation of diastereomeric salt with brucine. Fractional crystallization of the diastereomeric salt generates the partially resolved enantiomers. The solubility difference between the racemic mixture and its enantiomer was utilized to obtain the pure enantiomers. The active esters of the pendants were prepared. Grafting reactions were carried out by the reaction of active esters with PEI at room temperature. Completely grafted polymers were obtained.
Functional polymers and sequential copolymers by phase transfer catalysis. 25. Transformation of a monotropic mesophase into an enantiotropic one by increasing the molecular weight of the polymer and by copolymerization
Authors: Percec Virgil , Nava Hildeberto
Published: April 2003

The influence of molecular weight on thermal transitions and on the thermodynamic parameters was studied for two polymers based on 4,4′‐dihydroxy‐α‐methylstilbene with either 1,9‐dibromononane (HMS‐C9 polyethers) or 1,11‐dibromoundecane (HMS‐C11 polyethers). HMS‐C9 polyethers present an enantiotropic nematic mesophase over the entire range of molecular weights and a monotropic smectic mesophase for polymers of number average molecular weights higher than 17,000. The low molecular weight HMS‐C11 polyethers are only crystalline. On increasing their molecular weight, the polymers become monotropic nematics, and at higher molecular weights, enantiotropic nematics. Up to a composition containing as little as 20 mol % nonane structural units, the random copolyethers based on 1,9‐dibromononane, 1,11‐dibromoundecane, and 4,4′‐dihydroxy‐α‐methylstilbene (HMS‐C9/11 copolyethers) exhibit on cooling a phase diagram resembling that of HMS‐C9 polyether. HMS‐C9/11 containing about a 1/1 mole ratio between the two spacers presents both smectic and nematic enantiotropic mesophases. These results suggest that the phase diagram of random liquid crystalline copolymers is controlled by the shorter spacer. The thermodynamic parameters of isotropization for both polyethers and copolyethers are compared and suggest that copolymerization does not significantly decrease the degree of order of the mesogenic units in the mesomorphic phase.
Organic semiconductors—metal phthalocyanine sheet polymers
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. , Keshavayya J.
Published: April 2003

This publication discusses the electronic, magnetic susceptibility, MS and GC–MS pyrolysis, X‐ray powder diffraction, and electrical conductivity studies on metal phthalocyanine sheet polymers. The magnetic measurements over the range of magnetic field strengths 1025–6144 gauss indicated the absence of the intermolecular cooperative effect. MS and GC–MS studies indicate that all these metal phthalocyanine sheet polymers give benzene, cyanobenzene, and dicyanobenzene on thermal degradation. The electrical conductivity measurements showed that these polymers are semiconductor in nature.
Kinetic studies of nonaqueous polymerization of methyl methacrylate initiated by ferric laurate–n‐hexyl amine system
Authors: Saha Sanjib Kumar , Chaudhuri Ajit Kumar
Published: April 2003

The polymerization of methyl methacrylate was studied in carbon tetrachloride medium with ferric laurate, a metal soap, in combination with n‐hexyl amine as the initiator system at 60°C. The rate of polymerization was found to be linear with the monomer concentration and proportional to the square root of both ferric ion and amine concentration. A reaction scheme involving initial complex formation between ferric ion and amine and subsequent reaction of the complex with the solvent molecule to produce free radicals responsible for initiation of polymerization has been postulated to account for the observed results.
Structure property correlation in crosslinkable copolyimides
Authors: Sen Debasish , Maiti Mrinal M. , Maiti Sukumar
Published: April 2003

Three copolyimides containing crosslinkable alkyne groups either in the main chain backbone or as endgroups, have been synthesized and characterized in regard to their structure, molecular weight, solubility, film‐forming properties, crystallinity, crosslinking behavior, and thermal stability. A good correlation between the structure of the polymers and their properties has been established.
A comparison of heterogeneous and homogeneous kinetics in the formation of a polyurethane
Authors: Pearson R. G. , Williams E. L.
Published: April 2003

The extent of reaction between a liquid polyfunctional aromatic isocyanate and a diol was studied using infrared spectroscopy to follow the reduction in concentration of the isocyanate group. For the homogeneous conditions the reaction was performed in benzene solution. For the heterogeneous conditions the isocyanate was dispersed as droplets in the diol and the reaction proceeded interfacially.

From a proposed model for the interfacial reaction based on the steady‐state diffusion theory the second‐order rate constant of the reaction can be evaluated. The values obtained were compared to the second‐order rate constants obtained for the solution method. For a range of temperature the heterogeneous rate constant was approximately six decades higher than that obtained for the homogenous conditions. However the activation energies obtained corresponded within a factor of 1.5.
Preparation of new blocked diisocyanate for dental application
Authors: Lei G. Y. , Angeli S. R. , Kristol D. S. , Snyder W. H.
Published: April 2003

A novel two‐stage method of preparing 2‐hydroxyethyl methacrylate (HEMA) and methoxyphenol or cholorophenol blocked 2,4‐tolylene diisocyanate (TDI) was devised. The first stage reaction of TDI with HEMA was carried out in petroleum ether heterogeneously with the precipitation of the intermediate product, monoadduct, in the reaction solution, and followed by a second stage homogeneous reaction of monoadduct with the blocking agent, chlorophenol, or methoxyphenol, in ethyl acetate. In both reactions the inhibitor, chloranil, and the catalyst, dibutyltin dilaurate, were used. A total of eight products were achieved. Results of elemental analyses of these products along with their LC chromatograms, NMR, and IR spectra indicated that these materials were indeed the compounds expected. Testing results of these materials as dental adhesives will be reported in a separate paper.
Nematogenic block copolymers of rigid and flexible aromatic units. I. Synthesis and characterization
Authors: Krigbaum W. R. , Preston J. , Ciferri A. , Shufan Zhang
Published: April 2003

Three types of wholly aromatic block copolymers were synthesized using the phosphorylation reactions of Yamazaki and Higashi. Each copolymer contained blocks of rigid and flexible units. The first copolymer, PBA/PABH‐T, contains blocks of poly(p‐benzamide) and the polyterephthalamide of p‐aminobenzhydrazide. The second copolymer, PBA/MPD‐I, contains blocks of poly(p‐benzamide) and poly(p‐phenylene isophthalamide), whereas the third, PPD T/MPD‐I, contains blocks of poly(p‐phenylene terephthalamide) and poly(m‐phenylene isophthalamide). Three synthetic routes were used for the preparation of the block copolymers. In the two‐step polycondensation (A), monomers of the flexible block are added to the rigid prepolymer. The multistep method (B) differs in that the rigid prepolymer is carboxy‐terminated prior to addition of the monomers of the flexible block. Carboxy‐terminated prepolymer of the rigid block is reacted with amine‐terminated prepolymer of the flexible block in the two‐pot condensation (C). The presence of a considerable amount of the flexible homopolymer is indicated by viscosity, extraction, and NMR studies, particularly when methods A and C were used. The flexible homopolymer can be extracted by using a nonsolvent for the rigid blocks. Extraction of the rigid homopolymer (which may also be presumed to be produced) entails a more elaborate procedure. In principle, one can use these methods to obtain pure block copolymer for study of mixtures with the rigid and flexible homopolymers. Phase studies of some of these systems will be reported in a following paper.
Influence of functional sulfonic acid groups on styrene–divinylbenzene copolymer pyrolysis
Authors: Matsuda Masami , Funabashi Kiyomi
Published: April 2003

The decomposition ratio of cation exchange resin (sulfonated ST‐DVB copolymer) after pyrolysis is only 50 wt%, while that of ST‐DVB copolymer is 90 wt%. Fundamental experiments were performed to investigate the reason for the low decomposition ratio of the former.

The cation resin consists of base polymer (ST‐DVB copolymer) and functional sulfonic acid groups. Chemical analyses of the pyrolysis products showed that most of the functional groups decomposed at about 300°C and generated SO2 gas. However, only a small amount of the base polymer was pyrolyzed even at 600°C and the total decomposition ratio was only 50 wt%. The XPS studies on the residue showed that 35% of the functional sulfonic acid groups was converted to sulfonyl and sulfur bridges between the base polymers during pyrolysis. These bridges made the base polymers, namely ST‐DVB copolymer, thermally stable.
Characterization of cobalt‐modified polyimides
Authors: Boggess Robert K. , Taylor Larry T.
Published: April 2003

Modified polyimide films containing cobalt have been prepared by the addition of cobalt(II) chloride to a solution containing one of the diamines 4,4′‐oxydianiline (ODA) or 4,4′‐diaminodiphenylsulfide (DDS) and one of the dianhydrides 3.3′, 4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) or 4,4′‐bis(3,4‐dicarboxyphenoxy)diphenylsulfide dianhydride (BDSDA) and characterized by thermal methods, UV‐visible spectra, room‐temperature direct‐current electrical resistivity measurements, and X‐ray photoelectron and Auger electron spectroscopy. A principal goal of this work was to establish if there was coordination of the potential donor atoms of the polymide to cobalt. UV‐visible spectra of the modified polyamic acid solutions and polyimide films and a titration study of a model system do not show any appreciable coordination with either the polyamic acid or the polyimide; rather, the cobalt(II) appears to be coordinated to the solvent, N,N‐dimethylacetamide (DMAc), as [Co(DMAc)4]2+, until the temperature is raised above 200°C. X‐ray photoelectron spectra of films cured only to 200°C also do not show significant shifts in the binding energies of the potential donor atoms from those binding energies of the undoped polymers, confirming little direct coordination of the cobalt to atoms of the polyimide. Heating the films to 300°C in a forced‐air oven causes the formation of a cobalt oxide layer on the air side of the polymer. Direct‐current electrical resistivity measurements on this surface show a 104–106 reduction in resistivity due to this layer.
Theoretical basis and kinetic sense of covalent propagation in cationic polymerization
Authors: Matyjaszewski Krzysztof
Published: April 2003

Polymerization of several vinyl and heterocyclic monomers was described recently as proceeding by covalent propagation. In this paper the theoretical basis of purely covalent multcenter propagation is discussed in terms of the orbital symmetry theory and the parity rules. A mechanism is considered in which ionic and covalent species are present simultaneously. Covalent species may react with monomers, forming intermediate ions. The kinetic sense of the rate of this elementary reaction is described.
Synthesis of polyformals from nitro‐ and fluordiols. Substituent and chainlength effects
Authors: Adolph Horst G. , Goldwasser Judah M. , Koppes William M.
Published: April 2003

A series of primary and secondary diols carrying nitroalkyl, nitro, and fluoro substituents was reacted with formaldehyde under conditions of acid catalysis. Short‐chain primary diols gave cyclic formals while predominantly linear polymers were obtained beginning with pentane‐1,5‐diols and hexane‐1,6‐diols, depending upon the nature of the substituents. No polymers were formed from secondary diols with 1‐nitroalkyl substituents. The effect of monomer structure on polymer formation is discussed. The polymers obtained were characterized by GPC and end group analysis.
Synthesis and characterization of certain aromatic azopolyamides
Authors: Rajendran V. , Nanjan M. J.
Published: April 2003

Two new aromatic diamines, 2,2′‐dimethyl‐4,4′‐diaminoazobenzene [benzenamine‐(3,3′‐dimethyl‐4,4′‐azobis)] and 2,2′‐dichloro‐4,4′‐diaminoazobenzene [benzenamine‐(3,3′‐dichloro‐4,4′‐azobis)] were synthesized and their structures confirmed by IR, UV‐visible, 1H‐NMR, 13C‐NMR, and mass spectra. With these diamines, 16 aromatic polyamides were synthesized by both low‐temperature solution and phosphorylation polycondensation methods. The polymers were characterized by viscosity, solubility, IR, UV visible, TGA, and DTA studies.
Studies on poly(iminomethylenes)
Authors: King R. B. , Greene M. J.
Published: April 2003

A variety of simple alkyl and aryl isocyanides have been polymerized using 0.5% NiCl2 in ethanol as a catalyst. The resulting poly(iminomethylenes) have been characterized by carbon‐13 NMR spectroscopy and their polystyrene‐equivalent molecular weights have been determined by gel permeation chromatography. Straight chain aliphatic isocyanides having from three to ten carbon atoms in the chain form readily solyble polymers having molecular weights (Mw) in the general range 10,000 to 30,000. Neopentyl isocyanide unlike tert‐butyl isocyanide forms an insoluble polymer. A number of new soluble aryl isocyanide polymers have been obtained. However, aryl isocyanides having a single alkyl substituent (CH3, C2H5, CF3) in the ortho position give only insoluble polymers, whereas aryl isocyanides having alkyl substituents in both ortho positions (e.g., 2,6‐(CH3)2C6H3NC and 2,4,6‐(CH3)3C6H2NC) fail to polymerize under these conditions. The highest molecular weight soluble aryl isocyanide homopolymer is obtained from 3‐CH3OC6H4NC(Mw = 26,000). The trimethylsilyl substituted isocyanide (CH3)3SiCH2CH2NC has been obtained from LiCH2NC and (CH3)SiCH2Cl and gives a brown soluble homopolymer with a molecular weight (Mw) of 19,000.
Magnesium chloride supported high mileage catalysts for olefin (decene‐l) polymerization XIV. Propagation and chain transfer
Authors: Chien James C. W. , Ang Tsunle
Published: April 2003

Decene‐l was polymerized with the MgCl2/ethylebenzoate/p‐cresol/AIEt3/TiCl4‐AlEt3/methyl‐p‐toluate catalyst at 50° using an A/T ratio of 167 and a range of monomer concentration. The concentration of the two kinds of active sites are [Ti] = 12% and [Ti] = 4% of the total titanium. The rate constants of propagation are 24 M−1 s−1. Chain transfers to AIEt3, monomer, and by β‐hydride elimination have rate constant values of 1.7 × 10−3 M−1 s−1, 1.34 × 10−2 M−1 s−1, and 1.7 × 10−2 s−1, respectively. Poly(decene‐l) have relatively narrow MW which are unchanged during the course of a polymerization. Therefore, the active site concentrations in the CW catalyst for propylene and decene polymerization are identical and their rate constant values agree within a factor of 2. However, the rate of decene polymerization depends on fractional order of monomer concentration and decreases with the increase of activator concentration. Furthermore, the formation of metal polymer bonds has a rate independent of these concentrations. These kinetic behaviors are a manifestation of absorption processes of these species which are not seen in propylene polymerizations.
Cationic ring‐opening transfer polymerization of spiro ortho esters initiated by carbon black
Authors: Tsubokawa Norio , Ohshima Shingo , Sone Yasuo , Endo Takeshi
Published: April 2003

The ring‐opening transfer polymerization of spiro ortho esters (SOE) initiated by carbon black was investigated. In the absence of carbon black, no polymerization occurred at all. In the presence of channel black containing carboxyl group, the ring‐opening transfer polymerization of SOE was initiated at 50‐70°C. to give polyether ester, namely alternating copolymer of epoxide and lactone. The rate of polymerization of 1,4,6‐trioxaspiro[4.4]nonane and 1,4,6‐trioxaspiro[4.5]decane was considerably small compared with that of 1,4,6‐trioxaspiro[4.6]undecane. The activation energy of the polymerization of 2‐chloromethyl‐1,4,6‐trioxaspiro[4.6]undecane was estimated to be 6.0 kcal/mol. The initiating activity of carbon black increased with an increase in carboxyl group content of carbon black. Furnace black that contained no carboxyl group was unable to initiate the polymerization. Furthermore, the carbon black lost the initiating ability of the polymerization upon the blocking of carboxyl group on the surface by the treatment with potassium hydroxide or diazomethane. Based on these results, it was concluded that carboxyl group on carbon black plays an important role in the initiation. During the polymerization, a part of the polymer formed was grafted onto carbon black: the grafting ratio was 10–30%. The mechanisms of initiation and grafting were discussed.
Acidolysis of poly(4‐methyl‐1,3‐dioxolane)
Authors: Diab M. A. , Hseih D. T. , Lillya C. P. , Chien James C. W.
Published: April 2003

The onset of decomposition of poly(4‐methyl‐1,3‐dioxolane) was lowered to 70°C by 0.1 wt% p‐toluene sulfonic acid from 170°C in the absence of acid to produce more than 81% yield of monomer. Protonation forms cyclic oxonium ion followed by depolymerization. Minor products are isomers of hydroxymethyl‐2‐hydroxyl‐2‐methyl ethyl ether and bis(2‐hydroxyl‐2‐methyl ethoxyl)methane from rearrangements of the oxonium ions. The first order rate constant of acidolysis of poly(4‐methyl‐1‐1,3‐dioxolane) is about 8.5 kcal mol−1, which is much smaller than about 17 kcal mol−1 for the acidolysis of poly(1,3‐dioxolane).
Circular dichroism of copoly(γ‐stearyl‐L‐glutamate–γ‐methyl‐L‐glutamate)
Authors: Tsujita Yoshiharu , Ojika Ryoko , Tsuzuki Koji , Takizawa Akira , Kinoshita Takatoshi
Published: April 2003

Copoly(γ‐stearly‐L‐glutamate‐γ‐methyl‐L‐glutamate)s with various compositions were synthesized by the ester exchange reaction of poly(γ‐methyl‐L‐glutamate). Circular dichroism studies were carried out for solution and solid film as a function of the degree of stearylation and temperature. The slight and gradual temperature dependence of molecular ellipticity was observed for solution of all the copolyglutamates studied here and for the solid film of the copolyglutamate with the degree of stearylation of 16%, indicative of no reversal in the helix sense. However the remarkable change in negative molecular ellipticity with temperature was detected for the solid film of the copolyglutamate with a low degree of stearylation, e.g., 52%, whereas the drastic change in molecular ellipticity from a negative to positive value appeared for that with a higher degree of stearylation. This is discussed in terms of the reversal in the helix sense from a right‐ to left‐handed α helix with the increase of temperature occurring at the melting temperature of the ordered side chain region.
Thermal decomposition processes in aromatic‐aliphatic polyamides investigated by mass spectrometry
Authors: Ballistreri Alberto , Garozzo Domenico , Maravigna Pietro , Montaudo Giorgio , Giuffrida Mario
Published: April 2003

The thermal decomposition processes of some aromatic‐aliphatic polymides, derived from terephthalic acid and aliphatic diamines, were studied by flash Pyrolysis‐GCMS and by direct Pyrolysis‐Mass Spectrometry, using both Chemical lonization and Electron Impact modes.

The results indicate that the primary thermal decomposition proceeds via a β‐CH hydrogen transfer process, with formation of pyrolysis products containing amide and olefin end‐groups. Nitrile end‐groups are also formed by dehydration of the amide groups formed in the primary decompostion process.