bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of poly(4‐vinylpyridine) substituted with a novel betaine salt derived from 4,5‐dicyanoimidazole
Authors: Apen Paul G. , Rasmussen Paul G. 
Published: April 2003

AbstractA novel betaine internal salt (3) has been synthesized by the reaction of pyridine with 1‐methyl‐2‐bromo‐4,5‐dicyanoimidazole (1). The reaction of pyridine with 1 serves as a model for the reaction of poly(4‐vinylpyridine) with 1. The reaction of poly(4‐vinylpyridine) with 1 gives betaine salt substituted polymers which were characterized by IR, NMR, UV‐visible spectroscopy, and viscometry. The substituted polymers were compared to the model compound (3) and to unsubstituted poly(4‐vinylpyridine) in order to determine polymer structure and the degree of substitution. One of the substituted polymers shows polyelectrolyte behavior. Thermal characterization of the substituted polymers shows two exothermic transitions at 260 and 340°C attributed to chemical reactions of the pendant groups.
Studies of the antenna effect in polymer molecules. XVII. Synthesis and photocatalytic activity of poly(sodium styrenesulfonate‐co‐N‐vinylcarbazole) and poly[sodium styrenesulfonate‐co‐N‐(acryloyloxyhexyl)carbazole]
Authors: Nowakowska M. , White B. , Vogt S. , Guillet J. E. 
Published: April 2003

AbstractTwo new antenna polyelectrolytes, poly(sodium styrenesulfonate‐co‐N‐vinylcarbazole) (PSSS–VCz) and poly[sodium styrenesulfonate‐co‐N‐(acryloyloxyhexyl)carbazole](PSSS–AHCz) have been synthesized. Both polymers were found to solubilize large hydrophobic compounds such as perylene in aqueous solution, but PSSS–AHCz was much more efficient than PSSS–VCz. The distribution coefficients of perylene between the polymer pseudophase and water was determined to be (2.9 ± 0.1) × 106 and (4.0 ± 0.2) × 104 in PSSS–AHCz and PSSS–VCz, respectively. The greater solubilizing ability of PSSS–AHCz is attributed to the higher content of hydrophobic monomer units in the polymer. Both copolymers displayed photocatalytic activity, absorbing light in the UV‐visible spectral region. Energy can then be transferred to a solubilized molecule or dissolved oxygen and induce photochemical reactions. The model reaction used in this study was the photosensitized oxidation of perylene solubilized in aqueous polymer solutions. PSSS–AHCz was found to be a much more efficient photocatalyst than PSSS–VCz. The enhanced photocatalytic activity of PSSS–AHCz is attributed to the greater concentration of carbazole chromophores, the higher local concentration of probe in the polymeric pseudophase and possibly to the elimination of the low‐energy excimer.
Synthesis of linear polyformal and copoly(carbonate formal) from polycarbonate
Authors: Wang Z. Y. , Berard N. , Hay A. S. 
Published: April 2003

AbstractA linear, high molecular weight polyformal is readily synthesized by direct transformation of commercially available polycarbonate. The reaction is best carried out in dibromomethane with 8.0 equiv. of potassium hydroxide pellets in the presence of a phase‐transfer catalyst at 90–95°C. A random copoly(carbonate formal) can also be obtained simply by reducing the amount of potassium hydroxide used in the reaction. The molecular weight of the resulting polymer is governed by the starting polycarbonate.
Excited states of CF4 plasma for polymerization of TMPTA monomer
Authors: Bretagne J. , Epaillard F. , Richard A. 
Published: April 2003

AbstractThe F and CF2–CF2+ excited states have been detected by emission spectroscopy in CF4RF plasmas used for TMPTA polymerization. These excited states are related through electron collision to F and CF2 ground states. The temporal variation of the F and CF2–CF2+ radiative states near the substrate reveals that the F atoms disappear first by incorporation in the monomer during the polymerization phase and, then, by a third body recombination process enhanced by the polymer surface. The CF2–CF2+ radiative states are varying as the inverse of the F states indicating a strong destruction mechanism of CF2 radicals by F atoms.
Model studies on the kinetics and mechanism of polyarylate synthesis by acidolysis
Authors: Huang Jianing , Leblanc Jean‐Pierre , Hall H. K. 
Published: April 2003

AbstractModel reactions were carried out to simulate the acidolysis process for polyarylate synthesis by using p‐tert‐butylphenyl acetate (ptBuPhOAc) and benzoic acid in diphenyl ether. p‐tert‐Butylphenol was formed in the reaction mixture and its concentration stayed constant throughout the reaction. Acetic benzoic anhydride and benzoic anhydride were detected by NMR. Based on this experimental evidence, a mechanism for the acidolysis was proposed involving the mixed anhydride. The kinetics of the acidolysis reaction was studied for this model reaction. The overall reaction order is two and the reaction order with respect to each reactant is one. Second‐order reaction rate constants were measured at different reaction conditions (200–250°C). The activation energy (Ea), activation enthalpy (ΔH≠), and activation entropy (ΔS≠) were calculated from these data. The thermodynamic parameters of the acidolysis reaction were also measured for the analogous reaction of p‐tert‐butylphenyl pivalate (ptBuPhOPiv) and benzoic acid. The kinetics of two other elementary reactions involved in the acidolysis reaction were also studied: p‐tert‐butylphenol with acetic anhydride or benzoic anhydride, and p‐tert‐butylphenyl pivalate with benzoic acid.
An improved method for the diimide hydrogenation of butadiene and isoprene containing polymers
Authors: Hahn Stephen F. 
Published: April 2003

AbstractThe hydrogenation of unsaturated polymers with diimide generated in‐situ by thermolysis of p‐toluenesulfonyl hydrazide (TSH) is a commonly used method for preparing laboratory scale quantities of saturated diene based polymers. The by‐products from TSH, particularly p‐toluenesulfinic acid, can attack at olefinic sites, adding p‐tolylsulfone functionality and degrading polymer molecular weight. The addition of tri‐n‐propyl amine has been found to eliminate these side reactions in butadiene containing polymers and copolymers, enabling the preparation of polymers devoid of backbone unsaturation. No detectable sulfur‐containing impurities were indicated by IR, NMR, or elemental analysis, and no chain degradation was observed via GPC analysis of the hydrogenated polymers. cis‐Polybutadiene and butadiene containing random and block copolymers with styrene were hydrogenated cleanly using this technique. A ratio of 2 mol TSH and 2 mol amine/mol of olefin was necessary to assure > 99% hydrogenation, and a w/v ratio of 2 parts butadiene/100 parts o‐xylene gave the most efficient hydrogenation. Polymers prepared from isoprene were only partially hydrogenated when treated with TSH in the presence of tri‐n‐propyl amine, and gave evidence of slight degradation of the polymer structure.
Preparation of hydrogenated nitrile rubber using palladium acetate catalyst: Its characterization and kinetics
Authors: Bhattacharjee Susmita , Bhowmick Anil K. , Avasthi B. N. 
Published: April 2003

AbstractHydrogenated nitrile rubber was prepared by using palladium acetate as the homogeneous catalyst system. The effect of different reaction parameters on the level of hydrogenation was studied. The extent of hydrogenation increased with increase in reaction time, temperature, pressure, and catalyst concentration. A maximum conversion of 96% could be achieved. The degree of hydrogenation was estimated from IR and NMR spectroscopy. The selectivity of the catalyst in reducing CC in presence of CN was supported by IR and 13C‐NMR spectra. ESCA studies further confirmed this observation. Properties of hydrogenated nitrile rubber were investigated by various techniques such as gel permeation chromatography (GPC), glass transition temperature (Tg), stress‐strain behavior and rheological measurements. GPC studies showed no significant change in molecular weights of the products after the reaction. Tg value decreased with an increase in the level of hydrogenation. The ultimate stress improved significantly with the increase in the extent of hydrogenation. The die swell decreased with hydrogenation at a particular shear rate. The kinetics of the NBR hydrogenation were investigated. With the increase of the hydrogen pressure and catalyst concentration, the rate of the reaction increased. The reaction was apparently first order with respect to olefinic substrate at higher hydrogen pressure. The apparent activation energy, enthalpy, and entropy of the reaction were calculated as 29.9 kJ/mol, 27.42 kJ/mol, and –0.20 kJ mol−1 K−1, respectively.
Gamma‐, photo‐, and thermally‐initiated oxidation of linear low density polyethylene: A quantitative comparison of oxidation products
Authors: Lacoste J. , Carlsson D. J. 
Published: April 2003

AbstractThe detailed oxidation products from the initiated oxidation of linear low density polyethylene have been compared by the use of infrared spectroscopy combined with chemical derivatization. Oxidized films were treated with NO or SF4 to allow the resolution of the various alcohol and hydroperoxides and of the carbonyl species, respectively. All types of initiation gave very similar products but in varying quantities. In photooxidation, hydroperoxide was clearly shown to approach a photostationary concentration either from below for fresh film or from above for samples that had been pre‐oxidized by γ‐irradiation, prior to UV exposure. Carboxylic acid groups, the main backbone scission product, dominated in photooxidations, possibly as the result of the further oxidation of sec‐hydroperoxide sites.
Poly(Aryl ether‐phenylquinoxaline)s: Self‐polymerization of an A—B monomer via quinoxaline‐activated ether synthesis
Authors: Labadie J. W. , Hedrick J. L. , Boyer S. K. 
Published: April 2003

AbstractA new A—B monomer, 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline (1), which contains both a quinoxaline‐activated fluoro group and a phenol group was prepared and it's self‐polymerization studied. Compound 1 was prepared either by condensation of 3,4‐diaminofluorobenzene with 4‐hydroxybenzil, or condensation/demethylation with 4‐methoxybenzil in a one pot procedure. The polymerization of 1 was carried out in NMP in the presence of potassium carbonate at 180–190°C, analogous to previous examples of quinoxaline‐activated polyether synthesis. A new poly(aryl ether‐phenylquinoxaline) (2) was synthesized by this procedure, which was processable from N‐methylpyrrolidone, displayed a Tg of 255°C and a polymer decomposition temperature of 450°C. The mechanistic implications of quinoxaline activated fluoro‐displacement using an A—B monomer are discussed.
Absorption spectra of thin film of polyaniline
Authors: Wan Meixiang 
Published: April 2003

AbstractThe absorption spectra of thin film of polyaniline (PANI) on slide glass coated by a spin coater were measured as a function of the protonation state of PANI, the concentration of solution of PANI in NMP, drying temperature, and atmosphere. The absorbance value of the 950 nm peak and the ratio of the absorbance value at 950 nm to that of the 630 nm peak increases with increasing the protonation state of PANI. This is consistent with the observation of varying the conductivity with the protonation state. A modified molecular structure of PANI is proposed:
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where y and x are defined as the oxidation and the protonation states of PANI, respectively.
Synthesis and conformation of poly(L‐azetidine‐2‐carboxylic acid‐L‐proline) and poly([L‐proline]3‐L‐azetidine‐2‐carboxylic acid)
Authors: Tsai F. H. , Overberger C. G. , Zand R. 
Published: April 2003

AbstractThe synthesis, characterization, and conformational assessment of poLy(L‐Aze‐L‐Pro) and poly[(L‐Pro)3‐L‐Aze] are reported. The polymers were prepared by using the pentachlorophenol active ester as the polymerizable tetrapeptide derivatives. The copolymer, poly(L‐Aze‐L‐Pro), assumes a Form II helix in polar solvents, and is converted into a form I‐like helix at a critical solvent composition of ethanol to trifluoroethanol. The CD spectrum of this Form I‐like conformation of poly(L‐Aze‐L‐Pro) is similar to that of poly(trans‐5‐isopropyl‐L‐proline), indicating that the rigid four‐membered ring at the alternating position can lock in the structure by a mechanism similar to that of a bulky substituent at the trans‐5‐position of proline. The helix conformation of this copolymer was unfolded in a 0.2M CaCl2 aqueous solution. In contrast to poly(L‐Aze‐L‐Pro), the copolymer of poly[(L‐Pro)3‐L‐Aze] contains both cis and trans peptide bond geometry when dissolved in a 90:10 ETOH‐H2O mixture. The conversion of the mixed conformation of poly[(L‐Pro)3‐L‐Aze)] into a polyproline Form II‐like structure occurred in highly polar solvent environments such as water.
Grafting of polymers onto carbon whisker by anionic graft polymerization of vinyl monomers using metallized aromatic rings and/or phenoxy lithium groups on the surface as initiator
Authors: Tsubokawa Norio , Yoshihara Toshio , Sone Yasuo 
Published: April 2003

AbstractDuring the anionic polymerization of methyl methacrylate (MMA) initiated by n‐butyl‐lithium (n‐BuLi) in the presence of carbon whisker, PMMA was found to be grafted onto the surface depending on the propagation from OLi groups, which are produced by the reaction of oxygen containing groups on the surface with n‐BuLi. But no grafting of polystyrene was observed at all. By the activation of OLi groups by the addition of crown ether, however, the grafting of polystyrene onto the carbon whisker was achieved. On the other hand, it was found that metallized carbon whisker also initiates the anionic graft polymerization of MMA and styrene: percentage of grafting of PMMA and polystyrene reached 231.3 and 157.9%, respectively. The metalation of carbon whisker was achieved by the treatment with n‐BuLi in aprotic polar solvents, such as N,N,N′,N′‐tetramethylethylene‐diamine or hexamethylphosphorous triamide, and in toluene in the presence of complexing agent of cation such as crown ether or a small amount of aprotic solvent. In the polymerization, grafted polymer chains were considered to propagate both from metallized aromatic rings and from OLi groups. The polymer‐grafted carbon whisker gave a stable colloidal dispersion in organic solvents.
Inhibition of acrylic acid polymerization by phenothiazine and p‐methoxyphenol. II. Catalytic inhibition by phenothiazine
Authors: Levy Leon B. 
Published: April 2003

AbstractInhibition of acrylic acid by p‐methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N‐radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p‐methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p‐methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p‐methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p‐methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.
Cationic polymerization of γ‐methyl‐ and α‐methylphenylallene
Authors: Takahashi Tatsuya , Yokozawa Tsutomu , Endo Takeshi 
Published: April 2003

AbstractThe cationic polymerizations of γ‐methylphenylallene (1) and α‐methylphenylallene (2) were carried out with some Lewis acids at 25 and 0°C in dichloromethane to obtain the corresponding polymers through allyl cations, respectively. Tin (IV) chloride was found to be an effective catalyst for the cationic polymerization of both allenes 1 and 2 compared with other Lewis acids. Thus, in the polymerization of 1, methanol‐insoluble polymer was only obtained using Tin (IV) chloride, and M̄n of methanol‐insoluble polymer obtained by Tin (IV) chloride was the highest in the polymerization of 2. From the analysis of 1H‐ and 13C‐NMR spectra of the obtained polymers, the polymer from 1 consisted of two kinds of units polymerized by each double bonds of allene 1, whereas the polymer from 2 consisted of only one unit polymerized by terminal double bond of allene 2. Moreover, effect of solvent on the cationic polymerizations of 1 and 2 were discussed.
Thermal redistribution reactions in crosslinked polysiloxanes
Authors: Belot V. , Corriu R. J. P. , Leclercq D. , Mutin P. H. , Vioux A. 
Published: April 2003

AbstractThe thermolysis under argon of various polysiloxane resins containing D, T, DH, or TH units was investigated using thermogravimetric analysis combined with mass spectroscopy (TG/MS analysis) and solid‐state 29Si‐NMR. Redistribution reactions involving the exchange of SiC/SiO bonds or SiH/SiO bonds were evidenced in addition to the exchange of SiO/SiO bonds reported to date. These reactions significantly modify the initial siloxane units and lead to an escape of volatile silanes or siloxanes. The exchange of SiH/SiO bonds takes place at lower temperatures (300°C) than the exchange of SiC/SiO bonds (500°C).
Catalytic inhibition in free radical polymerizations
Authors: Suddaby K. G. , O'Driscoll K. F. , Rudin A. 
Published: April 2003

AbstractFree radical polymerizations of methyl methacrylate and methacrylamide in DMF solution were found to be catalytically inhibited by the addition of the boron fluoride derivative of cobaloxime to the system. The nature of this inhibition is examined and equations which describe the kinetics of these catalytically inhibited polymerizations are developed. Using these equations estimates of the inhibition constants (Cz) of 7.23 × 102 and 2.27 × 102 were estimated for methacrylamide and methyl methacrylate, respectively.
Poly(N‐acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. III. Surface properties and abhesion
Authors: Cai Gangfeng , Litt Morton H. 
Published: April 2003

AbstractThe surface properties and abhesion of both N/Si and U/Si series of random copolymers were studied by contact angle and peel strength measurements. When these copolymers are coated on clean glass slides, the contact angles of water on the polymer films are over 105° for copolymers with less than 50 mol % of Si, and 98‐104° for those with more than 50 mol % of Si. All the polymers have similar critical surface energies, 21 dyn/cm (from hydrocarbon probes) and 20 dyn/cm (from EtOH/H2O probes), within the experimental error. This demonstrates that the amide groups in the polymer backbones are buried and all the polymers have methyl surfaces. The copolymers with less than 50 mol % Si (for N/Si copolymers) or 20 mol % (for U/Si copolymers) are stable and show good abhesive properties toward Scotch magic tape at or below 50°C. The peel strengths of Scotch magic tape with the copolymer coated slides rise dramatically as the annealing temperatures approach to the melting points of the polymers.
Stereoregular polyamides derived from methylene‐L‐tartaric acid and aliphatic diamines
Authors: Rodríguez‐Galán A. , Bou J. J. , Muñoz‐Guerra S. 
Published: April 2003

AbstractStereoregular polyamides containing two chiral backbone carbons in the repeating unit were prepared by polycondensation of bis(pentachlorophenyl) 2,3‐O‐methylene‐L‐tartrate with 1,9 and 1,12‐alcanediamines activated as N,N′‐bis(trimethylsilyl) derivatives. The polymers were characterized by elemental analysis, IR, and 1H‐NMR spectroscopy, and differential scanning calorimetry. Both viscosimetry and GPC were used to estimate the molecular weights which ranged between 6000 and 44000. These polytartaramides were readily soluble in chloroform, displayed moderate optical activity in solution, and formed highly crystalline films.
Molecular weight distribution in emulsion polymerization. I. The homopolymer case
Authors: Storti Giuseppe , Polotti Gianmarco , Cociani Michele , Morbidelli Massimo 
Published: April 2003

AbstractA model for evaluating the instantaneous degree of polymerization distribution of homopolymers produced in emulsion, based on the mathematics of the Markov chains, is developed. The model accounts for any number of active chains per particle, as well as for the two fundamental mechanisms of chain termination: mono‐ and bi‐molecular, both by combination and by disproportionation. The core of the model is the so called subprocessmain process treatment, which allows us to correctly evaluate the degree of polymerization of the chains growing in the polymer particles, by distinguishing between the events experienced by the polymer chain which imply a change of its degree of polymerization (subject transitions) and those which imply only a change in the particle state (environment transitions). This is obtained by properly defining the one‐step transition probability matrix of the relevant Markov process. Once this is done, the evaluation of the distribution of the degrees of polymerization reduces to a few simple operations among matrices. Explicit expressions for the instantaneous probability density functions and the relative cumulative distributions are obtained. The application of such relationships is facilitated by the numerical procedures reported in the Appendices. The results of the model developed in this work are in agreement with those of earlier models in the range of parameter values of practical interest. In the limit of very low molecular weights, only the model developed in this work provides the correct answer. Moreover, a much more significant result is its applicability to the case of emulsion copolymerization, as it is shown in Part II.
Selective hydrolysis of oxazoline block copolymers
Authors: Litt M. H. , Lin C. S. 
Published: April 2003

AbstractBlock copolymers, composed of a hydrophobic block [poly(N‐t‐butylbenzoyl ethylenimine) or poly(N‐lauroyl ethylenimine)] and a hydrophilic block [poly(N‐propionyl ethylenimine)], synthesized by cationic ring‐opening polymerization of 2‐substituted Δ2‐oxazolines, were selectively deacylated by acid hydrolysis. The hydrolysis process was monitored by using 1H‐NMR. The results show that the propionyl groups could be removed from the hydrophilic block of the polymer chain without touching the hydrophobic block, if appropriate reaction conditions were used.
Side‐chain liquid crystalline polymers with silphenylene‐siloxane main chains. III. Synthesis and characterization of polymers with phenyl benzoate mesogenic groups
Authors: Itoh Maki , Lenz Robert W. 
Published: April 2003

AbstractSide‐chain liquid crystalline (SCLC) silphenylene‐siloxane polymers with a phenyl benzoate mesogenic group and polymethylene spacers were prepared and characterized, and their properties were compared with those of equivalent SCLC polymers, SCLCPs, with a biphenyl mesogenic group. With identical spacers and terminal substituents, the melting temperatures of the former were much lower, but the isotropization temperatures were lowered to a lesser extent, than those of the latter, and, consequently, a more thermally stable nematic phase was obtained for the former. Both types of SCLCPs formed nematic phases, while polymethylsiloxanes with the same side‐chain mesogens exhibited smectic phases with wider temperature ranges. The lower thermal stability of the mesophases in the silphenylene‐siloxane SCLCPs compared to those of the SCLC polymethylsiloxanes can be attributed to both the rigidity of the backbone and the greater separation of the side‐chains along the main chains of the former.