bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular structure and photoreaction of poly(methylpropylsilane)
Authors: Ban Hiroshi , Sukegawa Ken
Published: April 2003

The molecular structure and photoreaction of poly(methylpropylsilane) (PMPrS) are investigated. The 29Si‐NMR spectra reveal that PMPrS is a linear polymer with no blanches. Fine multiple splitting of 29Si‐NMR is observed at room temperature. This multiple splitting is thought to be due to molecular conformation. The photo‐oxidation reaction of the PMPrS film is found to be caused by light irradiation at the UV absorption band, 330 nm. Quantum efficiencies of scission and crosslink related to photodegradation are evaluated. There is little difference in either the molecular structure or photoreactivities between the high and the low molecular weight portions of the bimodal molecular weight distributions of PMPrS.
Organotin polymers.I. Copolymerization on tributyltin methacrylate with (hydroxy) alkyl methacrylates
Authors: Dharia J. R. , Pathak C. P. , Babu G. N. , Gupta S. K.
Published: April 2003

Copolymers of tributyltin methacrylate (M1) with cyclohexyl methacrylate, ethoxyethyl methacrylate, ethyl methacrylate, 2‐hydroxyethyl methacrylate, and 2‐hydroxypropyl methacrylate were synthesized in solution at 55°C utilizing azobisisobutyronitrile initiator. Copolymer compositions were determined by tin analysis; monomer reactivity ratios were calculated by Kelen‐Tüdös method. Since the reactivity ratios indicate the distribution of different monomer units in the polymer chain, the measured values are compared and discussed. Preliminary results of the biotoxicity studies on some of the copolymers are also reported.
Copolymerization of trifluoropropene with itaconic acid and ethylvinylether by using gamma rays
Authors: Otsuhata Kazushige , Jin Cao , Tabata Yoneho
Published: April 2003

Copolymerization of trifluoropropene (TFP) with itaconic acid (IA) and ethylvinylether (EVE) have been carried out by using gamma rays from a 60Co source. Copolymers of TFP‐IA and TFP‐EVE were white powder and white grease, respectively. The copolymerization rate of TFP‐IA system is proportional to 0.64 power of dose rate and that of TFP‐EVE system is proportional to 1.0 power of dose rate. The apparent activation energy for TFP‐IA system is 4.3 kcal/mol and it is 10 kcal/mol for TFP‐EVE system. The copolymerizations of both TFP‐IA and TFP‐EVE are inhibited remarkably by a radical scavenger, PBQ. The reactivity ratios for those systems were determined roughly to be rTFP = 0.55, rIA = 13 and rTFP = 0.30, rEVE = 0.20.
High activity Ziegler–Natta catalysts for the preparation of ethylene copolymers
Authors: Nowlin T. E. , Kissin Y. V. , Wagner K. P.
Published: April 2003

High activity ethylene polymerization catalysts have been prepared by the interaction of ethylmagnesium chloride in tetrahydrofuran with high surface area silica, followed by reaction with excess titanium tetrachloride in heptane. The catalysts were tested in ethylene—hexene copolymerization reactions in the presence of AlEt3 at 80°C. For comparison purposes, the copolymerization properties of a similar catalyst prepared without silica were also evaluated. Preparative conditions were identified which provide catalysts that possess high reactivity towards 1‐hexane. The silica and the amount of magnesium used in catalyst preparation strongly affect the copolymerization properties of the catalysts. Generally, catalysts prepared with silica showed much higher sensitivity to 1‐hexene (effective reactivity ratio r1 = 25–60) while a similar catalyst prepared without silica exhibited an r1 value of 125. Fractionation of the copolymer with a series of boiling solvents showed that all the catalysts exhibit a wide distribution of active centers with respect to reactivity ratios, with the r1 values varying from 5–7 to ca. 200. The width of a the center distribution depends on catalyst composition—it is the narrowest for the catalyst prepared without silica and is the widest for the catalysts with intermediate Ti : Mg ratios.
The kinetics of photoinitiated dead‐end polymerization
Authors: Joshi Makarand G. , Rodriguez Ferdinand
Published: April 2003

The kinetic expressions for a dead‐end polymerization initiated by the photolysis of a sensitizer are derived. The phenomenon of dead ending amplifies the inherent differences between the kinetics of photoinitiated and thermally initiated polymerizations. The analysis clearly shows that photoinitiation has distinct advantages over thermal initiation for improving yields in a polymerization which exhibits dead ending.
Flame retardation of polyurethanes by means of 1,4‐bis[(dialkoxyphosphinyl)hydroxymethyl]benzene
Authors: Mikroyannidis John A.
Published: April 2003

New phosphorus‐containing homopolyurethanes were synthesized by reacting various diisocyanates such as tolylene diisocyanate, methylenebis(4‐phenylisocyanate) and hexamethylene‐1,6‐diisocyanate with 1,4‐bis[(dialkoxyphosphinyl)hydroxymethyl]benzene (BDAB). In addition, copolyurethanes containing approximately 3% phosphorus were prepared by copolymerization of these diisocyanates with an equimolar amount of BDAB—hydroquinone mixture. BDAB was less reactive towards diisocyanates than hydroquinone due to the electron‐withdrawing inductive effect of the phosphinyl groups. The polymers synthesized were characterized by inherent viscosity measurements as well as by proton nuclear magnetic resonance (1H‐NMR) and infrared (IR) spectroscopy. The spectroscopic examination of polymers did not provide evidence for crosslinking by allophanate groups. Differential thermal analysis (DTA) studies of polymers revealed that the incorporation of BDAB in polyurethanes altered their thermal decomposition mode by increasing the exothermicity due to pyrolysis. Thermogravimetric analysis (TGA) of polymers showed that the phosphorus‐containing homopolyurethanes and copolyurethanes were thermally less stable than the corresponding common polyurethanes but afforded higher char yields. Determination of the limiting oxygen index (LOI) values showed that the phosphorus‐containing copolyurethanes exhibited a higher fire resistance than that of common polyurethanes.
Polymerization of methyl methacrylate with ferric laurate in combination with various substituted amines as initiators
Authors: Saha Sanjib Kumar , Chaudhuri Ajit Kumar
Published: April 2003

The effect of various substituted amines on the polymerization of methyl methacrylate initiated by ferric laurate—amine as the initiator system has been studied in carbon tetrachloride medium at 60°C. Amines used are n‐butyl amine, di‐n‐butyl amine. The rate of polymerization is found to follow the order: tertiary > secondary > primary amine. From the detailed kinetic studies it was found that the overall polymerization rate can be expressed by the equation:

The relative activity of the different amines has been found to be dependent on the relative electron‐donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.
Preparation of a polymeric membrane crosslinked by the viologen structure from a cyanopyridinium salt polymer
Authors: Kitamura Naoya , Nambu Yoko , Endo Takeshi
Published: April 2003

The polymeric membrane crosslinked by a viologen structure was prepared by the reduction of the homopolymer with a pendant cyanopyridinium structure, poly(1‐vinylbenzyl‐4‐cyanopyridinium perchlorate), chemically or electrochemically. The homopolymer in the state of membrane was reduced chemically by aqueous sodium dithionite (Na2S2O4) to obtain the polymer containing viologen group (64 mol%) despite a heteogeneous reaction. When the membrane was reduced electrochemically, the resulting viologen moiety in the membrane showed reversible one‐ and two‐electron redox behavior.
Die swell–molecular structure model for linear polyethylene
Authors: Koopmans R. J.
Published: April 2003

An empirical relation between capillary die swell and molecular structure, defined by total weight average molecular weight (MwT), molecular weight distribution (MWD), and fraction high molecular weight content (FRB with MwB ≥ 164.000) is established. Via a Box–Behnken experimental design setup blends of Ziegler–Natta catalyzed linear polyethylenes are prepared to allow a statistical analysis of the die swell–molecular structure relation. The contradicting results of Rogers and Mendelson et al. for the die swell–molecular structure relation are shown to be compatible and are to be considered as special cases of the general model presented here. The existence of a die swell maximum is shown. The relative amount (FRB) and size (MwB) of the high molecular weight molecules define this elastic property of linear polyethylene melts.
Photoinduced polymerization and oligomerization of 4‐vinylbenzophenone
Authors: Tsubakiyama Kyoji , Yamamoto Masahide , Nishijima Yasunori
Published: April 2003

The photopolymerizations of 4‐vinylbenzophenone (VBP) in various solvents were investigated to make clear the photoininiation characteristics. It was found that direct photoirradiation produces polymers, oligomers (trimers), and dimers. The dimers were identified as trans‐ and cis‐1,2‐bis(4‐benzoylphenyl)cyclobutanes. The fraction of trans‐form in the cyclobutane dimers produced was about 80%, and was little affected by the reaction conditions. The quantum yields ([VBP] = 0.1M in benzene) was estimated to be 3 × 10−2 for the dimerization and 2 × 10−4 for the initiation of polymerization. The photoreactions via π,π* triplet state of the monomer was suggested from the results.
Direct polyesterification with thionyl chloride in pyridine improved by a modification of monomer sequences in copolymers
Authors: Higashi Fukuji , Sugimori Shigeru , Mashimo Toshio
Published: April 2003

The direct polyesterification with thionyl chloride (SOCl2) in pyridine was further investigated. Copolycondensations of dicarboxylic acids, bisphenols, and hydroxybenzoic acids were significantly affected by the reaction temperatures and combinations of monomers which could change relative rates of alcoholyses of the activated dicarboxylic acids and the hydroxyacids consequently to vary monomer sequences in the copolymers resulted. The sequences were tried to be varied more directly by stepwise reactions of monomers in copolycondensations of dicarboxylic acids, bisphenols, and p‐hydroxybenzoic acid (PHB), as well as PHB and m‐hydroxybenzoic acid (MHB). The reactions proceeded smoothly and satisfactorily when carried out by initial reaction of dicarboxylic acids and PHB followed by bisphenols likely to favor sequential to random distributions of monomers. Reverse addition of PHB and bisphenols, and then dicarboxylic acids resulted in rapid precipitation due to some oligomerization of PHB at an earlier stage of reaction, and largely retarded the reaction. This was also the case for the copolycondensation of PHB and MHB. Copolymers of high inherent viscosities with up to 65 mol % PHB could be obtained by initial reaction of MHB followed by PHB.
Flexible polyaniline
Authors: Kitani Akira , Kaya Masanori , Tsujioka Syo‐Ichi , Sasaki Kazuo
Published: April 2003

Flexible polyaniline having excellent mechanical properties (e.g., elongation at break = 41% and tensile strength = 1.8 kg cm−2) was prepared by electrochemical reduction of ordinary polyaniline in organic solvents. The flexibility is directly related with the polymer morphology which was definitely affected by the nature of electrolyte anion. Perchlorate or tetrafluoroborate anion were found suitable to obtain flexible polyaniline. At the same time, it is essential that the polymer so prepared should be reduced (undoped) in some suitable organic solvents before making a flexible free standing film.
A positron annihilation lifetime study of isothermal structural relaxation in bisphenol‐A polycarbonate
Authors: Hill A. J. , Jones P. L. , Lind J. H. , Pearsall G. W.
Published: April 2003

Positron annihilation lifetime spectroscopy has been used to study the isothermal relaxation response of compression molded bisphenol‐A polycarbonate at temperatures of 263, 273, and 303 K. The temperature dependence of both the lifetime and intensity of the ortho‐Positronium (o‐Ps) pickoff component is discussed in terms of ductile‐to‐brittle transition behavior and free volume theory. An additive exponential model and the Williams–Watt model were used to analyze the relaxation as a function of temperature and provided results consistent with the anticipated molecular mobility of polycarbonate at sub‐Tg temperatures.
Synthesis and characterization of polyimides containing heterocyclic units
Authors: Subramaniam Prema , Srinivasan Mahalingam
Published: April 2003

Five new polyimides containing phenoxaphosphine as well as dibenzothiophene, phenoxathiin, and thianthrene units have been synthesized from 10‐phenylphenoxaphosphine‐2,3,7,8‐tetracarboxylic dianhydride‐10‐oxide and heterocyclic diamines by the cyclopolycondensation method. These polyimides had inherent viscosities in the 0.75–1.10 dL/g range in conc. H2SO4 at 30°C. All the polymers were characterized by elemental analysis, density, solubility, crystallinity, IR spectra, and thermal methods.
High performance size exclusion chromatography of polyamic acid
Authors: Walker C. C.
Published: April 2003

Molecular weight studies of polyamic acids are complicated by polyelectrolyte effects. Although early work on the molecular weight determination of polyamic acids employed salts to suppress this polyelectrolyte effect, recent publications reveal that such salts can cause precipitation of polyamic acids from solution, however, a mobile phase consisting of 0.03M LiBr/0.03M H3PO4/1% vol THF in dimethyl formamide was reported to successfully suppress the noted polyelectrolyte effect without causing the precipitation of polyamic acid and give satisfactory size exclusion chromatograms using columns packed with “macro‐porous” glasses. However, the development time was long (ca. 4 h) and considering the lability of the polyamic acids, the results must be viewed with skepticism. We find that use of a similar “mixed” mobile phase with Zorbax® PSM‐Bimodal columns using size exclusion chromatography in the high performance mode (HPSEC) provides well resolved and reproducible chromatograms and molecular weight data with development times of < 15 min. Aside from the avoidance of long development times, which can lead to questionable results, this procedure permits the facile routine analysis of polyamic acid on a daily basis. The procedure has great utility as an analytical tool to support fundamental studies of polyamic acid chemistry and two examples of this application are given.
Plasma polymerization of mixed monomer gases
Authors: Sakata Jiro , Yamamoto Minoru , Tajima Ichiro
Published: April 2003

In this paper, plasma polymerization of mixed monomer gases was studied. In the films, the elements derived from each monomer are contained, and they are distributed homogeneously at a certain depth. The films are made up by the copolymers in which both monomers are combined. The chemical compositions of the copolymers can be controlled by changing the proportions of the two monomer gases. The films having gradual compositional change toward depth can be prepared by using a mixture of two monomer gases and changing their proportions during the plasma polymerization. These copolymeric and gradient copolymeric films were formed on porous glass hollow fibers, and gas permeability of these composite membranes was measured. The gradient copolymerization methods are available for the preparation of the membranes for gas separation.
Application of NIRA techniques for the determination of polymer end and functional groups
Authors: Roy R. B. , Kradjel C.
Published: April 2003

Near infrared reflectance analysis (NIRA) provides a quick and reliable method for the measurement of end and functional groups in polymers and polymeric products. Feasible applications of Technicon InfraAlyzer for the simultaneous determination of OH and COOH numbers from polyester resins, and percent nitrogen estimation in crosslinkable acrylamido derivatives of partially esterified cellulosic materials were studied. The analytical results obtained show that NIRA techniques provide accurate and precise measurement of functional and end groups from the polymer samples used for this study. In addition, the statistical data showed that the number of samples used in learning sets were adequate for the generation of reliable calibration equations.
Superactive and stereospecific catalysts. I. Structures and productivity
Authors: Hu Youliang , Chien James C. W.
Published: April 2003

Two series of catalysts were made, one from MgCl2–A solution containing MgCl2, EH (2‐ethylhexanol), and EB (ethyl benzoate) dissolved in decane and another from MgCl2–B solution containing MgCl2, EH, and phthalic anhydride which reacted to form the corresponding phthalic ester. Reactions of these solutions with TiCl4 with or without another ester produced a family of eight catalysts. They form two groups, one having monoesters as modifiers, and the other containing diesters as modifiers. The surface area, pore volume, x‐diffractions, polymerization activity, and catalytic stereospecificity of these catalysts have been compared. The diester catalysts differ from the monoester catalysts in every respect. By comparison the corresponding member of the diester catalysts have half as much Ti per Mg, more than 10 times the pore volume, more than a 100‐fold the surface area, about 50% more productivity, and greatly increased steroespecificity.
Synthesis and characterization of liquid crystalline copolymethacrylates, copolyacrylates, and copolysiloxanes containing 4‐methoxy‐4′‐hydroxy‐α‐methylstilbene and 4‐hydroxy‐4′‐methoxy‐α‐methylstilbene constitutional isomers as side‐groups
Authors: Percec Virgil , Hsu Chain Shu , Tomazos Dimitris
Published: April 2003

The synthesis of methacrylates and acrylates containing 4‐methoxy‐4′‐hydroxy‐α‐methylstilbene and 4‐hydroxy‐4′‐methoxy‐α‐methylstilbene constitutional isomers attached to the polymerizable group through flexible spacers containing 11, 8, 6, 3, and respectively 2 methylenic units is described. The radical copolymerization of a 1/2 or 2/1 mole ratio of the two constitutional isomeric monomers led to thermotropic side‐chain liquid crystalline polymers in all cases. The synthesis of copolysiloxanes based on the same constitutional isomeric mesogens as side groups, and flexible spacers containing 11, 8, 6, 5, and respectively 3 methylenic units is also described. All polymers were characterized by differential scanning calorimetry and optical polarization microscopy. The polymers containing 11 methylenic units in the spacer exhibit Sc mesomorphism, while the other polymers are nematic. Copolymethacrylates do not undergo side‐chain crystallization. Only the copolyacrylate containing 11 methylenic units in the spacer exhibits side‐chain crystallization. All the copolysiloxanes display side‐chain crystallization. The number of melting transitions seen for these polymers decreases with increasing spacer length. Copolysiloxanes containing dissimilar spacer length were also prepared. Only the copolymer synthesized with highly dissimilar spacer lengths, i.e., containing 3 and 11 methylenic units, does not undergo side‐chain crystallization. These results have demonstrated that while the type of mesophase is dictated only by the spacer length, the degree of decoupling of the motion of the side‐groups from the motion of the main chain is strongly dependent on the nature of the polymer backbone. For the same mesogenic unit and spacer length, the thermal stability of the mesophase is also dictated by the nature of the polymer backbone. The use of constitutional isomers of mesogenic units as side groups in liquid crystalline polymers provides at least qualitative information on the degree of decoupling of the side groups from the polymer main chain.
Investigation of the formation of poly(ethylene terephthalate) with model molecules: Kinetics and mechanism of the catalytic esterification and alcoholysis reactions. I. Carboxylic acid catalysis (monofunctional reactants)
Authors: Otton Jean , Ratton Serge
Published: April 2003

Monofunctional compounds (benzoic acid, heptyl alcohol, and 2‐butoxy‐ethanol) were used to investigate the kinetics of the esterification and the alcoholysis reactions. Carboxylic acids (benzoic acid) are the only catalysts present in the reaction medium. The factors which influence the kinetics of the esterification reaction were studied: the nature of the carboxylic acid (substituents on the benzene ring), the nature of the alcohol, the composition of the reaction medium (alcohol alone or with another solvent, ester, or water). The results point out for an acyl type (AAC2) mechanism. The alcoholysis reaction needs the presence of carboxylic acid as a catalyst to occur significantly. A similar mechanism is proposed for both reactions: nucleophilic attack by the oxygen atom of the alcohol at the ion pair formed by protonation of the acid (esterification reaction) or by protonation of the ester (alcoholysis).
New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). LIII. Lithiation of 2,4,4‐trimethyl‐1‐pentene and isopropylidene‐capped polyisobutylenes by butyllithiums in the presence of complexing agents
Authors: Peng K. L. , Kennedy J. P. , Wilczek L.
Published: April 2003

Lithiated isopropylidene‐telechelic polyisobutylenes (i.e., PIBs capped with

end groups) are most interesting novel intermediates for further transformations, e.g., functionalization, polymerization. This report concerns model lithiation experiments of 2,4,4‐trimethyl‐1‐pentene (TM1P) that guided us toward the subsequent quantitative lithiation of isopropylidene‐telechelic PIBs. Thus, lithiation of TM1P with, n‐, s‐, and t‐butyllithium, in the presence of various complexing agents (i.e., TMEDA, t‐BuOK, 1,2‐DPE, CH3OCH2CH2OCH3, THF, and 12‐crown‐4) followed by silylation with Me3SiCl (for the purpose of quantitation) gave three products: 2(trimethylsilylmethyl)‐4,4‐dimethyl‐1‐pentene (TM1P‐Si), 2(trimethylsilylmethyl)‐4,4‐dimethyl‐2‐pentene (TM2P‐Si2). The relative product composition strongly depends on the BuLi/complexing agent ratio and temperature. Among the different butyllithiums and complexing agents the best overall results were obtained with the s‐BuLi/TMEDA combination. Complete lithiation of TM1P with minimum dilithiation was obtained using the molar ratio [s‐BuLi]: [TMEDA]: [TM1P] = 2 : 2 : 1. The apparent activation energy of lithiation by s‐BuLi/TMEDA was found to be 6.7 ± 0.8 kcal/mol. Guided by TM1P model experiments, quantitative monolithiation of isopropylidene‐capped polyisobutylene (including ca. 4% chain and isomerization) was achieved using the molar ratio [s‐BuLi] : [TMEDA] : [CC] = 5 : 4 : 1.
Grafting of maleic anhydride to n‐eicosane
Authors: Russell K. E. , Kelusky E. C.
Published: April 2003

Maleic anhydride was grafted to the linear hydrocarbon, n‐eicosane, at 165°C in the presence of the free radical initiator, 2,5‐dimethyl‐2,5‐di(t‐butylperoxy)‐3‐hexyne. The anhydride has a low solubility in eicosane and a multiple addition procedure was adopted. Grafted product which separated from the reaction mixture was fractionated and analyzed. The fractions contained on average 2–5.5 anhydride units/eicosane residue. 1H‐ and 13C‐NMR studies show that the grafts consist of single succinic anhydride rings. At the concentrations of maleic anhydride chosen for homogeneous reaction ( < 0.02 M) and at 165°C, poly(maleic anhydride) is above its ceiling temperature, so that succinic anhydride radicals cannot add maleic anhydride to form polymer side chains. Instead, these radicals abstract hydrogen atoms to yield grafts consisting of single anhydride units.
Linear A–B and AA–BB polyamides with backbone aryl, alkyl, and alkenyl units
Authors: Ahmed Sharf U. , Livant Peter D. , Sikes Allison M. , Mathias Lon J.
Published: April 2003

High performance linear AA–BB and A–B polyamides were generated using polymerization schemes that gave polymers in higher yields and having better performance than previous methods. Polymers were characterized with FTIR, solution and solid‐state 13C‐NMR and showed the incorporation of aryl, alkyl, and alkenyl linkages in the polymer backbone. Thermal analysis showed that a significant weight percent of the polymers remained at 1000°C.
Thermal degradation of aliphatic polyamides studied by field ionization and field desorption mass spectrometry
Authors: Schulten Hans‐Rolf , Plage Bernd
Published: April 2003

The aliphatic polyamides nylon 6.6, 6.9, 6.10, 6.12, 12.6, 12.10, and 12.12 of the diamine dicarboxylic acid‐type were pyrolyzed in the ion source of a double‐focusing mass spectrometer and the thermal degradation products were recorded by field ionization (FI) and field desorption (FD) mass spectrometry (MS). In the FI mode, several series of thermal degradation products differing in the number of polymer repeating units were detected up to 1000 Daltons. The main products were oligomers and, in addition, protonated dinitriles and various protonated nitriles are formed in large amounts except for nylon 6.6 and nylon 12.6. These two polymers form, in contrast to all other samples, large amounts of protonated amides and diamines. The technique employed allows distinction between oligomers already present in the original polymer and oligomers formed by thermal fission of bonds in the polymer chain. Reaction mechanisms are given that explain the products observed. High resolution experiments and accurate mass measurements were performed to confirm the proposed structures. In the FD mode, cationized oligomers (attached mostly to a sodium cation) were observed below 200°C with the dimers being the base peak for most samples. In contrast to the FI results, the monomers were only detected at very low intensities. Similarly, only weak signals for additional thermal degradation products were registered except for nylon 12.6. At higher temperatures the FD mass spectra gave protonated and doubly protonated oligomers in the high mass range up to 2000 Daltons, which resulted in complementary structural information about the polymers.
Synthesis and characterization of semi‐ and full‐interpenetrating polymer networks of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and polydimethylsiloxane
Authors: Frisch Harry L. , Gebreyes Kassu , Frisch Kurt C.
Published: April 2003

The synthesis and characterization of pseudo or semi‐ and full‐interpenetrating polymer networks (IPNs) of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and polydimethylsiloxane were performed. We observed that in full IPNs, the elasticity of the IPN samples increased very drastically, as the composition of polydimethylsiloxane increased (i.e. 0–60%) while the tensile strength (TS) and the glass transition temperature (Tg) decreases. The pseudo IPNs appeared to consist of two phases while the full IPNs of lower siloxane content were miscible.
Copolymerization of 1‐(trimethylsilyl)‐1‐propyne with disubstituted hydrocarbon acetylenes
Authors: Hamano Toshiyuki , Masuda Toshio , Higashimura Toshinobu
Published: April 2003

Copolymerization of 1‐(trimethylsilyl)‐1‐propyne (MeC ≡ CSiMe3) with several aromatic and aliphatic disubstituted acetylenes (MeC ≡ CPh, n‐BuC ≡ CPh, 2‐octyne, and 4‐octyne) were examined by using Ta and Nb catalysts. The TaCl5–Ph3Bi catalyst was effective in copolymerization with the aromatic acetylenes, whereas the NbCl5–Ph3Bi catalyst was preferable in copolymerization with the aliphatic acetylenes. The copolymerization products were not mixtures of homopolymers but copolymers. The relative reactivity of monomer tended to decrease with increasing steric effect of monomer: 2‐octyne > MeC ≡ CSiMe3 > 4‐octyne > MeC ≡ CPh > n‐BuC ≡ CPh. The copolymers of MeC ≡ CSiMe3 with MeC ≡ CPh [copoly(TMSP/PP)s] had high molecular weight (Mw > 1 × 106), and provided thermally stable tough films. With increasing MeC ≡ CPh content of copoly(TMSP/PP), the oxygen permeability coefficient (P) decreased, while the separation factor (P/P) increased.
The substitution of polychlorotrifluoroethylene with sulfur, selenium, and phosphorus nucleophiles
Authors: Pelter Michael W. , Taylor Richard T.
Published: April 2003

The substitution of polychlorotrifluoroethylene (PCTFE) with sulfur, selenium, and phosphorus nucleophiles is reported. The primary reaction, which extends throughout the bulk of the polymer, is the incorporation of the nucleophile with concommitant loss of chloride. The substituted PCTFE's are studied by 1H‐, 13C‐, 19F‐, and 31P‐NMR, as well as IR, and elemental analysis.
Cationic and polymeric radicals of vinyl monomers in halogenated matrices: An ESR and SCF MO study
Authors: Tabata M. , Lund A. , Samskog P. O. , Lunell S. , Huang M. B.
Published: April 2003

The vinyl monomers methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, and β‐methylstyrene were dissolved in CF3CCl3, x‐irradiated at 4 or 77 K, and investigated by ESR spectroscopy. The molecular cation of methyl acrylate has no resolved hyperfine structure, indicating that the unpaired electron is localized on the carbonyl oxygen. Evidence that a two‐stage photoinduced reaction gives rise to a propagating radical was obtained. Propagating radicals were observed also with methyl methacrylate, acrylic acid, and methacrylic acid as solutes. The positive ion of β‐methylstyrene has been prepared and characterized. The experimental data have been compared with molecular orbital calculations at different levels of approximation.
Thermally reversible, covalently crosslinked polyphosphazenes
Authors: Salamone J. C. , Chung Y. , Clough S. B. , Watterson A. C.
Published: April 2003

The concept of thermally reversible crosslinking was investigated by using poly[bis(trifluoroethoxy)phosphazenes] with different percentages of cyclopentadienylethoxy and dicyclopentadienyldiethoxy substituent groups. The resultant structures of these polymers are discussed and the phenomenon of reversible crosslinking is demonstrated by means of a DSC study and solubility behavior.
Superactive and stereospecific catalysts. II. Kinetics of propylene polymerizations
Authors: Chien James C. W. , Hu Youliang
Published: April 2003

The kinetics of propylene polymerization by superactive CH‐catalyst prepared from toluene solution of MgCl2 · EH/PA/TiCl4–TEA/PES was investigated. The results are compared with CW‐catalyst prepared from crystalline MgCl2/EB/PC/TEA/TiCl4–TEA/MPT (abbreviations given in the text). The former is four times more active than the latter and produces more isotactic polypropylene. The CH‐catalyst has 25% of the Ti as isospecific sites as compared to 6.7% for the CW‐catalysts. These sites have the same rate constant of propagation so that the higher polymerization activity of the CH‐catalyst is attributable simply to a greater number of active sites. Differences in the kinetics of deactivation and of chain transfer for the two catalysts are described.
Synthesis and characterization of urethane polymers containing 2,2′‐biimidazole
Authors: Liu F. J. , Kokorudz J. S. , Collier H. L.
Published: April 2003

A heterocyclic nitrogen‐containing system having substituent primary diol function, i.e., 1,1′‐dihydroxethyl‐2,2′‐biimidazole (I), has been prepared and used to synthesize a series of new polyurethanes based on aromatic diisocyanates (TDI, MDI). Variation of solution polymerization parameters permitted the isolation and infrared, NMR, molecular weight, and thermal characterization of polymeric materials. Isolated polymers exhibit a linear structure and have Tg (150–170°C) and thermal stability (205–250°C for 20% weight loss) properties comparable to other typical urethane polymers. Zn2+ complexation was indicated by shifts in the imidazole ringmode infrared vibrational bands at 917 and 1133 cm−1 to higher frequencies.
Activation and racemization of trifluoroacetate esters in the cationic polymerization of styrene
Authors: Matyjaszewski K. , Lin C. H.
Published: April 2003

1‐Phenylethyl trifluoroacetate (1) does not react directly with styrene but it is readily incorporated into polymer chains in the presence of an excess of trifluoroacetic acid. The proportion of the nondeuterated 1‐phenylethyl end groups in the polymerization of deuterated styrene coinitiated with the acid was much higher than the proportion of the end groups formed by direct incorporation of the acidic protons ([CH3CHPhCD2CDPh …] > [HCD2CDPhCH2CDPh …]). The racemization of the optically active ester‐(pseudo‐first order rate constant at [HA]0 = 0.79 mol/L at 20°C equals kR = 1.7 × 10−4 S−1) is more rapid than the incorporation of the ester into polymer chains (kE = 1.5 × 10−4 mol−1 Ls−1, [M]0 < 0.4 mol L−1, i.e., kR > kE · [M]). These results and the complete loss of the optical activity in the final polymer indicate that the ester is activated by the acid but it is incorporated into polymer chain via ionic intermediates.
Synthesis and characterization of a multiblock copolymer of poly(N‐isovaleryl ethyleneimine) and poly(ethylene glycol)
Authors: Hsiue G. H. , Swamikannu A. X. , Litt M. H.
Published: April 2003

Block copolymers of poly(N‐isovaleryl ethyleneimine) (PiVEI) and poly(ethylene glycol) (PEG) were synthesized by coupling previously prepared blocks of PEG ditosylate with the dianion of the dihydroxy PiVEI. On the average four blocks coupled together to form the final block polymer. The PiVEI blocks crystallized with the same melting points as in the homopolymer. This restricted the mobility of the PEG blocks and they did not crystallize unless cooled well below room temperature. The mechanical properties of cast films were quite good with a tensile strength of 77 kg/cm2 and an elongation of 120%. The swelling of unoriented and oriented films with water was studied. The unoriented polymer absorbed about its own volume of water, even though PEG comprised only 40% of the total polymer.
Thermotropic liquid crystallinity of copoly(ester‐amides) prepared by the direct polycondensation with diphenyl chlorophosphate in pyridine
Authors: Higashi Fukuji , Arikawa Hideo , Mochizuki Akihiko
Published: April 2003

Copolycondensation of isophthalic (IPA) and terephthalic (TPA) acids, methylhydroquinone (MeHQ), and aromatic diamines with diphenyl chlorophosphate (DPCP) in pyridine were investigated. The resulting copoly(ester‐amides) showed optical anisotropy, which was discussed in terms of the ester and amide sequence lengths in the copolymers. The temperature above which the anisotropy was observed varied in the 225 to 300°C range by changing addition time of a mixture of MeHQ and diamines, initial reaction with MeHQ, and the further reaction with diamines.
Benzocyclobutene in polymer synthesis. III. Heat‐resistant thermosets based on Diels–Alder polymerization of a bisbenzocyclobutene and a bismaleimide
Authors: Tan Loon‐Seng , Arnold Fred E. , Soloski Edward J.
Published: April 2003

Several compatible mixtures of 2,2‐bis[4‐(N‐4‐benzocyclobutenyl) phthalimid‐4‐phenyl]hexafluoropropane (BCB) and 1,1′‐(methylene di‐4,1‐phenylene)bismaleimide (BMI) were prepared according to the molar ratios (BCB : BMI): 1 : 1; 1 : 1.5; 1 : 3; 1.5 : 1. Complete compatibility of the mixtures was evidenced by a single initial Tg. All mixtures showed relatively low initial Tg's (61–70°C) and characteristic polymerization exotherms of benzocyclobutene‐based systems (onset: 221–225°C; maximum: 257–259°C), providing an excellent processing window (ca. 155°C). The cured sample of the mixtures, pure BCB and BMI (250°C; N2; 8 h) were subjected to comparative isothermal gravimetric analysis (ITGA). After 200 h at 650°F (343°C) in circulating air, the cured BMI sample retained only 3% of its original weight, whereas the mixtures of BCB and BMI exhibited thermo‐oxidative stabilities similar to BCB (13–15% weight loss). A model compound was synthesized from the intimate mixture of N‐phenylmaleimide and N‐benzocyclobutenyl phthalimide in 63% yield. The ITGA results and isolation of the model Diels–Alder adduct render strong support to the conviction that Diels–Alder polymerization is indeed the predominant curing process in the BCB/BMI system.
Grafting of vinyl monomers onto sisal fiber in aqueous solution
Authors: Samal Bibhuti B. , Sahu Sagarika , Chinara Braja B. , Nanda S. , Otta P. K. , Mohapatro L. M. , Mohanty Trijama R. , Ray A. R. , Singh K. C.
Published: April 2003

Graft copolymerization of acrylonitrile (AN) onto sisal fibers (chemically modified) was studied using the Mn(III)/EDTA redox system in aqueous solution. The effects of time, monomer (AN), metal ion [Mn(III)] substrate [ethylene diamine tetraacetic acid (EDTA)], temperature, and acid concentration on graft yield have been studied. The effects of thiourea on the graft yield has also been studied. A suitable mechanism is proposed.
Phthalonitrile‐based high temperature resin
Authors: Keller Teddy M.
Published: April 2003

An aromatic, diether‐linked phthalonitrile resin, prepared from 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl, exhibits excellent thermo‐oxidative properties. The resin is easily processed from the melt of the monomer in a controlled manner as a function of the amine curing agent and processing temperatures. Polymerization occurs by a cyclic addition reaction without the formation of volatile by‐products. The polymerization reaction can be stopped at a prepolymer stage. The prepolymer can be stored indefinitely at ambient conditions without further reaction. The modulus and viscoelastic properties of the resin were found to be a function of the postcuring conditions.
Thermally reactive aromatic polyamides
Authors: Evers Robert C. , Moore George J. , Abraham Tonson
Published: April 2003

2,5‐Bis(phenylethynyl)terephthaloyl chloride and 4,6‐bis‐(phenylethynyl)isophthaloyl chloride were synthesized in a multistep reaction scheme from 2,5‐dibromoterephthaldehyde and 4,6‐dibromoisophthaldehyde, respectively. Low temperature solution polycondensation of these novel monomers and tolane‐2,4′‐dicarbonyl chloride with aromatic diamines yielded aromatic polyamides containing phenylethynyl moieties. Inherent viscosities of 0.20–0.51 dL/g were recorded. Attempts to carry out the homopolymerization of 2‐(3‐aminophenylethynyl)benzoyl chloride hydrochloride under similar conditions led to low molecular weight polyamide. Under differential scanning calorimetry and thermal mechanical analysis, the polyamides exhibited strong exotherms with onset occurring in the 185–225°C range. The exotherms were attributable to intramolecular cycloaddition of phenylethynyl moieties with amide groups to give polybenzalphthalimidine structures. Curing of a pressed pellet specimen for 16 h at 250°C under a nitrogen atmosphere resulted in partial conversion to a polybenzalphthalimidine structure with a concomitant increase in the polymer glass transition temperature. Isothermal aging in air of the cured specimen at 316°C (600°F) led to 25% weight loss after 200 h.
Separation and structural analysis by 1H‐NMR of the telomers of methyl methacrylate with thiophenol
Authors: Bessiere Jean‐Marie , Boutevin Bernard , Sarraf Lena
Published: April 2003

The stereoselectivity of the addition step and the transfer step of the radical telomerization of methyl methacrylate with thiophenol has been studied by determining the structure and the amount of each isomer by 1H‐NMR. We found, in this case, that the addition step gave preferentially a diad r and that the transfer step gave preferentially a diad m. On the other hand, the tacticity observed for higher telomers is preferentially syndiotactic, similar to that of the poly(methyl methacrylate) prepared by radical initiation. The propagation process for radical telomerization obeys, as for the radical polymerization, Bernoulli's statistics.
Polymerization photoinitiated by carbonyl compounds. VIII. Solvent and photoinitiator concentration effects
Authors: Encinas M. V. , Garrido J. , Lissi E. A.
Published: April 2003

The interaction of benzil and thioxanthone triplets with triethylamine leads to the production of free radicals that are able to initiate the polymerization of methylmethacrylate and vinyl acetate. The process is mediated by a charge transfer complex. The initiation efficiency is higher in benzene than in acetonitrile, a result explained in terms of competition between back electron transfer, production of free ions and ketyl radical formation. The initiation efficiency decreases when the carbonyl concentration increases, because of the occurrence of a radical molecule reaction such as
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The α‐hydroxy radicals produced in this reaction are unable to initiate the polymerization chain.
Oligomerization of ethylene with a homogeneous sulfonated nickel ylide–aluminum alkoxide catalyst
Authors: Kissin Yury V. , Beach David L.
Published: April 2003

Various organoaluminum compounds strongly affect reactivity of a sulfonated nickel ylide complex in its reactions with ethylene. The complex, if used alone, is an active single‐component catalyst for ethylene oligomerization to linear 1‐alkenes. Al(C2H5)3 and tetraethylaluminoxane completely deactivate the catalyst by reducing it to Ni(O). Alkylaluminum halides, such as Al(C2H5)2Cl and Al(C2H5)Cl2, convert the nickel complex into a very active catalyst for ethylene dimerization to mixtures of butenes. Aluminum alkoxides, e.g., Al(C2H5)2OC2H5, AlC2H5(OC2H5)2, and Al(OC2H5)3, significantly increase oligomerization activity by a factor of 20–100. The distribution of 1‐alkenes (in the C4C40 + range) produced with the sulfonated nickel ylide–aluminum alkoxide catalyst follows the Flory molecular weight distribution law. The ratio of the chain termination to chain propagation rate constants is ca. 0.3 and is not temperature‐sensitive in the 50–120°C range. Kinetic analysis of the ethylene oligomerization reaction with the binary catalytic system showed that the number of active centers is proportional to the nickel complex concentration. The effective activation energy of ethylene oligomerization with the catalyst is ca. 27 kJ/mol. The oligomerization catalysts loose their activity in time. The activity decay follows the first‐order kinetic law. The rate of the decay increases with increasing temperature and is caused mainly by the intrinsic instability of active species.
Miniemulsion copolymerization of vinyl acetate and butyl acrylate. III. Experimental evidence for the role of the cosurfactant
Authors: Delgado Joaquin , El‐Aaser Mohamed S. , Silebi Cesar A. , Vanderhoff John W.
Published: April 2003

The role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50 : 50 molar ratio vinyl acetate–butyl acrylate monomer mixture is analyzed from an experimental point of view. The main factor responsible for the different kinetic behavior between the miniemulsion and conventional emulsion copolymerization processes was found to be the different particle nucleation mechanism operating in each process. Experimental evidence is presented indicating that in the miniemulsion copolymerization particle nucleation takes place in the preformed stable submicron monomer droplets.
Uncatalyzed polymerization of bistriazolinediones with electron‐rich aromatic compounds via electrophilic aromatic substitution
Authors: Mallakpour Shadpour E. , Butler George B.
Published: April 2003

The reaction of 4‐substituted‐1,2,4‐triazoline‐3,5‐diones(4R‐TD's), i.e., MeTD(4‐methyl substituted) and PhTD(4‐Phenyl substituted) with electron rich aromatic compounds were investigated. N,N‐Dimethylaniline undergoes reaction instantaneously with MeTD and PhTD. Electrophilic aromatic substitution occurred at room temperature at the para position without use of any catalyst. N,N,N′,N′‐tetramethyl‐m‐phenylenediamine (TMPDA) undergoes reaction with 2 mol of PhTD and MeTD which lead to the formation of 2:1 adducts in high yields. These compounds were fully characterized by IR, 13C‐NMR, 1H‐NMR and elemental analysis and were used as model compounds. The reaction of bistriazolinediones with TMPDA was performed in dimethylformamid at room temperature. The reactions are exothermic, fast, and gave novel polymer structures via electrophilic aromatic substitution. Some physical properties and structural characterization of these new polymers have been studied, and will be reported.
Photoresponsive inorganic polymers obtained by metal alkoxides
Authors: Ueda Hisashi
Published: April 2003

The polymerization of metal alkoxides was carried out in organic solvents and light responsive polymers were obtained. As starting materials for polymerization, Ti(OBu)4, Zr(OBu)4, Nb(OEt)5, and Ta(OEt)5 were used. The polymerization yield roughly corresponds to the formation of TiO2, ZrO2, NbO2(OEt), and TaO2(OEt), respectively. The polymers obtained are paramagnetic and all give similar (dark) ESR spectra. When illuminated by visible light, a new ESR absorption is detected in the vicinity of g = 2.00, or 330–340 mT (for 9.450 GHz) region. The formation and decay rates of this ESR absorption was measured. The decay rate constants obtained from the formation curves were larger than those obtained from the decay curves, indicating relatively short lived species are formed during light illumination. The polymers thus prepared have photocatalytic activity and can photolyze 1 : 1 methanol/water system with visible light. Other possible uses of these polymers as paramagnetic or photochromic materials are discussed.
Degradation of epoxidized polyenes in the presence of phthalic acid
Authors: Huang Wen‐Kuei , Hsiue Ging‐Ho
Published: April 2003

Viscometry was used to follow the epoxidation of polybutadiene and styrene–butadiene triblock copolymers (SBS) with monoperoxyphthalic acid (MPPA). Long reaction periods lead to an abnormal increase and then drop in reduced viscosity. The increasing viscosity is due to repulsion between oxirane group and its ring‐opening product with phthalic acid, while the viscosity drop can be correlated with a decrease of molecular weight. Long‐term storage of the epoxidized polyenes in the reaction solution containing phthalic acid, which is the derived product from MPPA, also leads to the dramatic decrease in molecular weights. The occurrence of degradation was confirmed by GPC analysis of molecular weight and molecular weight distribution. Chloroform accelerated the degradation reaction, possibly through the generation of hydrochloric acid. The degraded products were isolated and analyzed by GPC and NMR. A free radical mechanism was proposed for the oxidative degradation of epoxidized polyenes after excessive reaction.
Analysis of model polyurethane thermolysis products by direct mass spectrometer sampling
Authors: Greenwalt C. C. , Futrell Jean H. , Lyman Donald J.
Published: April 2003

The results obtained using a molecular beam direct sampling mass spectrometer system to determine the thermolysis products and investigate the decomposition kinetics of two model linear polyurethanes are reported. The polyurethanes are shown to degrade in this system strictly to the polycondensation reactants. These results conflict with previous research which indicated that the model polymers degraded by different mechanisms and yielded different degradation products. Kinetic analysis of results obtained from rapid thermolysis of the polymer in the ion source chamber of the pyrolysis mass spectrometer using the activation energy and frequency factor parameters deduced from thermogravimetric analysis of the same polymers reproduced the experimental data on decomposition as a function of time and temperature quite satisfactorily.
Synthesis and polymerization of (E,E)‐[6.2](9,10)anthracenophane‐1,5‐diene
Authors: Glans Jeffrey H. , Longone Daniel T.
Published: April 2003

The title compound has been synthesized by dimerization of a substituted p‐xylylene, generated via a 1,8‐Hofmann elimination. Several unique isomers of this dimer are also obtained. The title diene can be polymerized cationically to give low molecular weight polymer. Oxidative doping of this polymer with iodine forms a material with a conductivity of 3 × 10−4 S/cm. In contrast to previously reported anthracenophanes this polymer is photochemically unreactive.