bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorescence of auramine O and its binding to poly(vinylbenzo‐18‐crown‐6) and to polyvinylbenzoglyme in water
Authors: Wong Kam‐Han , Kimura Keiichi , Smid Johannes
Published: April 2003

Binding of the cationic dye auramine O (AuO) to the polysoap‐type polymers poly(vinylbenzo‐18‐crown‐6) (P18C6) and polyvinylbenzoglyme (PVBG) in water were studied by fluorimetry and dialysis. The quantum yield of P18C6‐bound AuO was found to be 0.028, the value being 0.018 for AuO bound to PVBG. The intrinsic binding constants were found to be 2.2 × 104M−1 (P18C6) and 1.2 × 104M−1 (PVBG), the respective first binding constants being 317 and 63M−1. Addition of crown‐ether‐complexable cations such as K+, Tl+, or Cs+ converts the neutral poly(crown ether) into a polycation, causing repulsion of the cationic dye and a strong decrease in the AuO fluorescence. AuO fluorescence was also studied in the absence of polymer in ether solvents, giving θ values of 0.011 and 0.018 in THF and dioxane. Traces of water rapidly form a nonfluorescent species. Solutions of AuO in water without polymer present exhibit very strong fluorescence on addition of BPh4 anions owing to formation of AuO+, BPh4− ion pairs and higher aggregates.
Anionic polymerization of lactones initiated by alkali graphitides. II. Changes in the KC24 structure during polymerization of lactones
Authors: Rashkov Iliya B. , Gitsov Ivan , Panayotov Ivan M.
Published: April 2003

The structural changes in the potassium graphitide KC24 in its interaction with ϵ‐caprolactone, γ‐butyrolactone and pivalolactone are examined by profilometric measurement and electron scanning microscopy. The interaction of KC24 with a nonpolymerizable lactone‐γ‐butyrolactone proceeds without delamination of the graphitide. The polymerization of ϵ‐caprolactone and pivalactone in the interlayer spaces of KC24 leads to destruction of the initiators structure. An increase in the temperature and monomer concentration enhances the delamination of the graphitide.
Friedel–crafts crosslinking methods for polystyrene modification. IV. Macromolecular structure of crosslinked particles
Authors: Barar Donald G. , Staller Kerry P. , Peppas Nikolaos A.
Published: April 2003

Crosslinked polystyrene particles were prepared by Friedel–Crafts suspension crosslinking of polystyrene using 2,4‐dichloromethyl‐2,5‐dimethyl benzene as crosslinking agent. The polymer was dissolved in nitrobenzene and reaction occurred in a 70 wt % aqueous solution of ZnCl2 with poly(vinyl alcohol) as a suspending agent. The spherical particles produced were swollen in toluene, chloroform, and tetrahydrofuran to determine their equilbrium polystyrene volume fraction. Analysis of the crosslinked macromolecular structure gave values of number‐average molecular weight between crosslinks of M̄c = 900–5900 increasing as the nominal crosslinking ratio X decreased from 0.75 to 0.0625 mol of crosslinking agent per mole of polystyrene repeating unit. Porosimetric analysis contributed to the understanding of the importance of the pore structure for swelling behavior.
Macromers by carbocationic polymerization. IV. Synthesis and characterization of polyisobutenyl methacrylate macromer and its homopolymerization and copolymerization with methyl methacrylate
Authors: Kennedy Joseph P. , Hiza Misao
Published: April 2003

This article describes the synthesis and characterization of a new macromer, polyisobutenyl methacrylate (PIB‐MA), its free‐radical homopolymerization and copolymerization with methyl methacrylate (MMA) to afford the graft copolymer poly(methyl methacrylate‐g‐isobutylene) (PMMA‐g‐PIB), the characterization of these polymers, and some physical‐mechanical (stress‐strain) measurements of the graft copolymer. The key intermediate toward the synthesis of the target macromer was the preparation of polyisobutenyl chloride PIB‐Clt by the minifer technique. As shown by 1 H‐NMR spectroscopy, and independently by IR spectroscopy coupled with M̄n determination, the PIB‐MA macromer carries one terminal methacrylate function per polyisobutylene chain. The free‐radical homopolymerization of PIB‐MA to very high‐molecular‐weight product was achieved in bulk at 60°C. The free‐radical copolymerization of PIB‐MA with MMA also occurs readily and is a convenient route to PMMA‐g‐PIB. The reactivity of PIB‐MA is almost identical to that of MMA; however, in highly viscous systems its rate of diffusion to the reaction site is reduced.
Study of interpolymer complex formation of polyvinylpyrrolidone and poly(ethylene oxide) with phenolic polymers in nonaqueous media
Authors: Chatterjee S. K. , Sethi K. R.
Published: April 2003

A study was made of interpolymer complex formation between polyvinylpyrrolidone (PVP) and poly(ethylene oxide) (PEO) with phenolic polymers (PPF) in an acetone–methanol mixture by several methods; for example, viscosity, potentiometry, conductometry, turbidity, and precipitate (complex) weight. A distinct stepwise complex formation between PVP and phenolic polymers was observed by these methods. As in polycarboxylic acid, however, PEO formed a 1:1 complex with phenolic polymers. Some of these observations have been interpreted in terms of the structure of the polymers, preferential solvation of the component polymers, and the probable change in conformation of the complex molecules in mixed solvents.
A kinetic method of reactivity ratio measurement in olefin copolymerization with Ziegler–Natta catalysts
Authors: Kissin Y. V. , Beach D. L.
Published: April 2003

An efficient kinetic method of reactivity ratio measurement for binary copolymerization of gaseous monomers4 that does not require the measurement of copolymer composition and can be applied to the data obtained in a single copolymerization run was modified and applied to olefin copolymerization with heterogeneous Ziegler–Natta catalysts. Estimated r1 and r2 values for pairs like ethylene‐propylene and propylene‐1‐butene agree favorably with published data.
Synthesis of benzylidene‐pendant polyphthalimidines from flexible bisphthalides and various diamines
Authors: Imai Yoshio , Takahashi Takeyoshi , Nan Renzhi , Ueda Mitsuru
Published: April 2003

New polyphthalimidine‐forming monomers, 5,5′‐(oxydi‐p‐phenylenedicarbonyl)bis(3‐benzylidenephthalide) and the 6,6′‐derivative, were synthesized by the Friedel–Crafts reaction of diphenyl ether with 5‐ and 6‐chloroformyl‐3‐benzylidenephthalide, respectively. The direct polycondensation of these bisphthalides with both aliphatic and aromatic diamines in o‐phenylphenol at 200–250°C afforded polyphthalimidines having inherent viscosities of 0.2–1.2 dL/g in almost quantitative yields. Syntheses of aliphatic polyphthalimidines with higher inherent viscosities were also achieved by a two‐step procedure involving ring‐opening polyaddition and subsequent thermal cyclodehydration. All the polymers were amorphous and readily soluble in N‐methyl‐2‐pyrrolidone (NMP), m‐cresol, nitrobenzene, pyridine, and chloroform. Tough and flexible films could be cast from NMP solutions of the polymers. Glass transition temperatures of the polyphthalimidines were in the range of 158–246°C. The thermogravimetry of the aromatic polymers showed 10% weight loss in air and nitrogen at 445–515 and 500–520°C, respectively. The crosslinking reaction of some benzylidenependant polyphthalimidines took place at 300°C through double‐bond addition to afford cured polymers with improved thermal stability.
Photopolymerization reactions initiated by copper (II)–amino acid chelates: Investigation of the initiating species by flash photolysis. I
Authors: Namasivayam C. , Natarajan P.
Published: April 2003

Flash photolysis of copper (II)–bis(amino acid) complexes (amino acids: glutamic acid, serine, or valine) in deaerated aqueous solution produces transient species having absorption maxima at around 350 nm. The transient species are identified as copper (II)–alkyl complexes. In the case of Cu(valine)2 at pH > 6.5 formation of Cu(II)‐alkyl complex is not observed; this is interpreted to be due to the presence of two bulky methyl groups of the coordinated valine ligand, which hinders the rearrangement. Pseudo‐first‐order rate constants for the decay of the transients are determined at different pH with varying concentration of amino acid ligand. The free‐radical species of the complexes responsible for the initiation of the vinyl polymerization reactions are identified as Cu(I)‐coordinated amino acid radicals which are formed in the primary photochemical reaction of the complex. A mechanism for the secondary reactions involving the initiating species consistent with the nature of the product formed and the pH dependence of the decay of the transients is proposed.
Synthesis of monomers that expand on polymerization. Synthesis and polymerization of 2,6,7‐trioxabicyclo[2.2.2]octanes with phenyl groups
Authors: Saigo Kazuhide , Bailey William J. , Endo Takeshi , Okawara Makoto
Published: April 2003

2,6,7‐Trioxabicyclo[2.2.2]octanes with phenyl group were prepared to obtain monomers which expand on polymerization. 1‐Phenyl‐4‐ethyl‐2,6,7‐trioxabicyclo[2.2.2]octane (I) could expand 0.2% during polymerization at a temperature slightly higher than the melting point. 1,4‐Diphenyl‐2,6,7‐trioxabicyclo[2.2.2]octane (II) also expanded as much as 1.4% on polymerization. Further, the hydrolysis of 2,6,7‐trioxabicyclo[2.2.2]octanes with p‐substituted phenyl groups were investigated to estimate the stability in water.
Mechanism of imidazole catalysis in the curing of epoxy resins
Authors: Ricciardi Fiore , Romanchick William A. , Joullié Madeleine M.
Published: April 2003

The mechanism of imidazole catalysis in the curing of epoxy resins was studied using the PGE/1‐methylimidazole, 2‐methylimidazole, and 1,2‐dimethylimidazole model systems and another model system based on trichloromethylethylene oxide. It was demonstrated that imidazolium systems, generated in the curing reaction, show an inherent instability leading to cleavage of an NC bond or the 2‐CH bond (2‐unsubstituted imidazoles). Fourier‐transform infrared spectroscopy was used to follow specific changes in the IR spectrum of the curing mixture during polymerization. The identification of carbonyl absorptions occurring during the polymerization led to the conclusion that ketone formation is a general occurrence in the cure of epoxides with nitrogen compounds. We have also shown that imidazoles are regenerated during the curing process by at least two routes. One pathway for the regeneration of the catalyst involves N‐dealkylation of the imidazole via a substitution process. Another route, β‐elimination, afforded carbonyl compounds, which account for the previously unexplained appearence of infrared bands in the 1650–1770 cm−1 region during the curing process. These investigations demonstrated the true catalytic function of the imidazole. Possible mechanisms for the regeneration of the catalyst are also suggested.
Enantioselective polymerization of γ‐benzyl‐DL‐glutamate N‐carboxy anhydride in the presence of poly(γ‐benzyl‐L‐glutamate)
Authors: Oguni Nobuki , Kuboyama Hiroaki , Nakamura Akira
Published: April 2003

The polymerization of γ‐benzyl‐DL‐glutamate NCA in the presence of poly(γ‐benzyl‐L‐glutamate) was investigated. At the initial stage the D‐enantiomer was preferentially polymerized (ca. 35% ee) by using triethylamine as an initiator. Enantioselectivity was independent of the molecular weight of preformed poly(γ‐benzyl‐DL‐glutamate).
Synthesis and solution properties of poly(trans‐5‐ethylproline). A slow mutarotating substituted polyproline
Authors: Ahn Kwang‐Duk , Overberger C. G.
Published: April 2003

An optically active polypeptide, poly(trans‐5‐ethylproline) (PT5EP) was synthesized and its solution properties were observed to investigate the conformational changes with various conditions. The trans‐5‐ethyl substitution on polyproline showed noticeable perturbed effects on the conformations of the polypeptide as well as mutarotation of the polypeptide in solution. Circular dichroism (CD) spectra suggested that the polypeptide existed in a poly(L‐proline) form‐I‐type helix and mutarotated slowly to an intermediate conformation in which some of the amide bonds had rotated to a trans conformation. In trifluoroethanol (TFE) solution the polymer took more than 20 days to change from a form‐I‐type helix conformation, in which CD bands for D‐PT5EP are at 199.5 ± 1.0 (positive), 115.5 ± 0.5 (negative), and around 238 nm (positive), to an intermediate conformation. Upon addition of trifluoroacetic acid (TFA) to a TFE solution, the polymer was transformed to form‐II‐type polymers. Even a greater change in conformation was observed in a solution of TFA or in LiClO4‐TFE. The overall change of the intensity ratio RCD of positive to negative CD bands of D‐PT5EP was from 0.6–0.7 to 30. Reverse mutarotation toward the original form I was observed when n‐butyl alcohol, water, or THF was added to a solution containing the form II polymer. A blue shift of the UV spectra and a change in the NMR spectrum also supported the concept of this conformational change.
Glow discharge polymerization of tetramethylsilane investigated by infrared spectroscopy and ESCA
Authors: Inagaki N. , Kishi A.
Published: April 2003

The influence of operating conditions (W/FM parameter: W input energy of rf power; F flow rate of monomer; M molecular weight of monomer) on glow discharge polymerization of tetramethylsilane (TMS) was investigated by infrared spectroscopy and ESCA. Elemental analyses showed that the compositions of the polymers formed strongly depended on the level of the W/FM parameter, i.e., whether the W/FM value was more or less than 190 MJ/kg. The infrared spectra indicated that these polymers were composed of SiH, SiO, SiC, SiCH3, and SiCH2 groups, and that there was no significant difference in structural features between polymers prepared at W/FM parameters of more or less than 190 MJ/kg. ESCA spectra (C1s and Si2p core‐level spectra) showed that the polymers included carbonized carbon, aliphatic carbon SiC, CO, SiO, and SiO2 species, and that the sum of carbonized and aliphatic carbons reached more than 50%. Raising the W/FM value increased the formation of the carbonized carbon but did not influence the formation of Si units such as SiC and SiO groups.

From this evidence the rupture of SiCH3 bonds in the polymer forming process is emphasized. The magnitude of the W/FM parameter may be related to the detachment of hydrogen from the aliphatic carbon units.
Synthesis, characterization, and properties of novel poly(ether urethanes)
Authors: Ghatge N. D. , Jadhav J. Y.
Published: April 2003

Novel poly(ether urethanes) were synthesized by homo‐ and random copolymerization of the m‐ and p‐hydroxyethoxy benzoyl azides. Polymerization proceeded by decomposition and rearrangement of the acid azide group to the isocyanate group, which immediately reacted intermolecularly with the hydroxyl group to produce polyurethanes. These polymers were characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), x‐ray diffraction, scanning electron microscopy (SEM), viscosity, and solubility. The thermal stability of these polymers was also studied by TG and DTG (derivative TG).
Adsorption layers of surface‐active substances and their influence on polyurethane network formation
Authors: Lipatova T. E. , Vengerovskaya Sh. G. , Feinerman A. E. , Sheinina L. S.
Published: April 2003

The study of polyurethane systems cured in the presence of surface‐active substances (SASs) proves that surfactants call forth the structural and kinetic changes in the reaction system. It is shown that surfactant decreases the viscosity of these systems in the early stages of reaction, shifting the beginning of structural gel formation to the higher degrees of NCO‐group conversion. The reaction rate is shown to be a complex function of surfactant concentration. The binary polyether‐surfactant system was studied by IR spectroscopy and surface tension measurement. The data prove that intermolecular and intramolecular H bonds in the system are redistributed at all surfactant concentrations but 0.03 and 0.15%. According to our calculations for surfactant adsorption layers at the polyether‐air interface, ΔS values do not depend on temperature at surfactant concentration 0.03% whereas at 0.15% ΔS and ΔH values are maximum. The results obtained by different methods are well correlated and suggest that kinetic effects are due to redistribution of H bonds under the influence of conformational changes in surfactant structure.
Polyaromatic ether‐ketones from o,o′‐disubstituted diphenyl ethers
Authors: Lee Jasun , Marvel C. S.
Published: April 2003

Polyaromatic ether‐ketone resins with potentially open structures which are possibly useful as membranes were prepared from diphenyl ethers with alkyl substitutions in the ortho positions and isophthaloyl or terephthaloyl chloride by Friedel–Craft‐type polymerization. These polymers are soluble in such solvents as DMF, DMA, and CHCl3, and can be cast into colorless transparent films.
Interaction of crosslinked polyethylenimine with a homologous series of methyl orange derivatives in aqueous solution
Authors: Takagishi Toru , Sugimoto Takeo , Hayashi Akiyo , Kuroki Nobuhiko
Published: April 2003

Polyethylenimine (PEI) was crosslinked with dichloroethane, glyoxal, or glutaraldehyde and polymers of various degrees of crosslinkage were made. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl, ethyl, propyl, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. PEI crosslinked with glutaraldehyde showed markedly increased binding affinity toward these cosolutes compared with the polymers crosslinked with dichloroethane or glyoxal. The extent of the binding increased with an increase in the degree of crosslinkage. These results suggest that the enhancement of the binding by the crosslinking is due mainly to a dual effect, introduction of hydrophobic moieties and proximity of neighboring polymer chains. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. The thermodynamic data show that the binding process is athermal and is stabilized entirely by the entropy term. Water‐soluble PEI exhibited stronger cooperative interactions than the crosslinked polymer because the mobilities of the chains of the former are greater than those of the latter.
Ignition of poly(methyl methacrylate) slabs using a small flame
Authors: Clark Ferrers R. S.
Published: April 2003

When exposed to a lean hydrogen‐oxygen flat flame, slabs of poly(methyl methacrylate) ignited to flaming combustion after a delay, the length of which depended on the gas temperature and the separation between the slab and the igniting flame. The delay obeyed an Arrhenius‐type expression, giving an activation energy of 96 ± 8 kJ mol−1. By the end of the delay the surface of the sample was pitted if the delay was long and almost unchanged if the delay was short. The rates of flame development measured immediately after the ignition were proportional to the ignition delay, the proportionality constant varying with the separation between slab and flame. These rates decreased as temperature increased; the slope of the linear Arrhenius plots was independent of slab‐flame separation. During the delay, carbon dioxide was formed within the boundry layer and a blue preignition glow was visible at its outer edge. These data were explained by a model in which ignition delay is governed by the induction period of gas‐phase reactions in or near the boundry layer. Models in which delay is governed by the time taken to heat the polymer to a critical ignition temperature did not satisfactorily explain the data.
Preparation and photolysis of polyamides having coumarin dimer component
Authors: Hasegawa Masaki , Saigo Kazuhiko , Katsuki Hirokazu , Yonezawa Noriyuki , Kanoe Toshio
Published: April 2003

The ring‐opening polyaddition reaction of anti and syn head‐to‐head Coumarin dimers with diamines and the photocleavage behavior of the resulting polyamides were investigated. Anti head‐to‐head Coumarin dimer successfully reacted with aliphatic and aromatic diamines in an aprotic polar solvent to give corresponding high molecular weight polyamides. The polyamides showed good film forming ability and exhibited solubility behavior typical of polyelectrolytes. Furthermore, these polyamides were found to undergo exclusively asymmetric photocleavage on the cyclobutane rings in the polymer main chain to give a fumaramide unit with elimination of 2,2′‐dihydroxystilbene. On the other hand, syn head‐to‐head Coumarin dimer gave only low molecular weight polyamides. These polymerization and photocleavage behaviors were elucidated in comparison with those of model reactions.
Ultra‐fast polymerization of epoxy‐acrylate resins by pulsed laser irradiation
Authors: Decker Christian
Published: April 2003

The 337.1‐nm emission of a pulsed nitrogen laser was shown to initiate the crosslinking polymerization of epoxy‐acrylate photoresists effectively. We evaluated the extent of curing from the amount of insoluble polymer formed and by the decrease in infrared (IR) absorption of the reactive double bond at 810 cm−1. With the large power density available in the laser pulse (0.5 MW cm−2) rates of polymerization as high as 108 mol L−1 s−1 were observed in the presence of air. Quantum yield measurements indicated that each photon absorbed can create as many as 450 crosslinks; the kinetic chain length was calculated as ca. 4000 double bonds polymerized per initiating radical. During the induction period due to oxygen inhibition each photoinitiator radical consumed 1 O2 molecule. The influence of the monomer and photoinitiator used on the sensitivity of the resin was examined; the best performing formulation contained the epoxy‐acrylate oligomer, pentaerythritol triacrylate, as monomer and 2,2 dimethoxy‐2‐phenyl‐acetophenone as photoiniatior. All the formulations studied can be cured by a single 500‐kW laser pulse of 8 ns duration, provided that the irradiation is carried out in an inert atmosphere or with a focused laser beam.
Gamma radiation‐initiated polymerization of styrene at high pressure. IV. Emulsion polymerization with nonionic emulsifier
Authors: Moore P. W. , Clouston J. G. , Chaplin R. P.
Published: April 2003

The effects of pressure, irradiation dose rate, and emulsifier concentration on the rate of polymerization of styrene emulsions stabilized with a nonionic surfactant, Teric GX13, were investigated. Results differed from those previously obtained with anionic surfactants and did not follow Smith–Ewart kinetics. The controlling influence of the surfactant at the particle–water interface on the reaction was demonstrated and results could be interpreted in terms of the Medvedev equation. Using this equation, we determined a value for the activation volume for chain propagation, ΔV, as −18.7 cm3 mol−1. This value is the same as that for pure styrene and emulsions that follow Smith–Ewart kinetics.
Polybromostryl macromers and their anionic polymerization
Authors: Königsberg Itzhak , Jagur‐Grodzinski Joseph
Published: April 2003

The decomposition of polybromostyryl carbanions (PBS−), obtained by anionic polymerization of 4‐bromostyrene in tetrahydrofuran (THF), was investigated in the dark in a temperature range of −6–−21°C. It was accompanied by the evolution of bromine anions and by the formation of polymeric allylic carbanions (λmax = 575 nm; εmax = 6800 eq−1·L·cm−1). The reaction mechanism was elucidated. The rate constant of the unimolecular rate‐determining step of the process was 1.3 × 10−5 s−1 and 9.7 × 10−5 s−1 at −21 and −6°C, respectively. Its apparent energy of activation Eapp = 18.38 Kcal/mol. The polybromostyrenes with allylic carbanions at their ends may decompose further. Their “dark” decomposition yielded 1,3‐butadiene‐1,3‐diphenyl‐macromers. The mechanisms of decomposition of the PBS− carbanions and the dark decomposition of the polybromostyryl allylic carbanions are analogous. The rate constant of the latter process was 2.5 × 10−6 s−1 at −6°C. The anionic polymerization of prepared macromers can be initiated in THF at −78°C by α‐methylstyryl carbanions, which do not react, however, with PBS− carbanions. “Comblike” polymacromers were prepared in which each branch had a molecular weight of about 50,000. The overall molecular weight of the polymacromer was estimated to be about 1 × 106. It has been assumed that the 2–1 mode of addition to the diene group of the macromer is predominant during its polymerization. The 3–4 mode of addition followed by proton shift represents the termination step. The 4–3 mode of addition was ruled out on the basis of spectroscopic evidence.
Radical polymerization in the presence of complexing agents. VI. Effect of low concentrations of ZnCl2 on the overall rate of copolymerization of methyl methacrylate with ethyl acrylate
Authors: Madruga E. L. , Román J. San , Rodriguez M. J.
Published: April 2003

Overall rates for the free‐radical copolymerization of methyl methacrylate with ethyl acrylate in the presence of low concentrations of ZnCl2 have been determined at 50°C. The rate of copolymerization Rp depends on both the ZnCl2 concentration and the monomer feed composition. Relative copolymerization rates Rp/R where R is the rate of copolymerization in the absence of complexing agent in the reaction mixture, show a minimum for intermediate feed compositions, independently of the ZnCl2 concentration. On the basis of the results obtained, a conventional copolymerization mechanism is proposed for this system in which free and complexed species of both acrylic monomers participate.
Kinetics and mechanism of acetylene polymerization
Authors: Schen M. A. , Karasz F. E. , Chien James C. W.
Published: April 2003

The kinetics of acetylene polymerization initiated by Ti(OBu)4/4AlEt3 catalyst was studied by radioquenching with C*O to count the number of active sites [C] and by CH3OT* to determine the total metal polymer bonds [MPB] and M̄n of the polymer. The amount of quenching agent and time of reaction required and the kinetic isotope effect for CH3OT* were determined. The effects of Al/Ti ratio, catalyst aging, catalyst concentration, temperature, and monomer pressure on the polymerization were investigated. Detailed kinetic data on the variation of rate of polymerization, Rp, [C] [MPB], and M̄n with time were obtained at 298 and 195°K. The results required the assumption that the catalytic species C, is initially active and within less than 30 min all are converted by bimolecular kinetics to a far less active species. Analysis of the data yielded rate constants of propagation and termination and their energies of activation. Estimates of chain transfer efficiency were obtained. The mechanisms for the propagation, termination, and transfer processes were discussed. By drawing on our earlier EPR results we propose probable structures for the catalytically active species.
Correlation of fine structural characteristics and textile properties of silk fiber
Authors: Padhi R. C. , Labischinski H. , Patel A.
Published: April 2003

The small‐angle, x‐ray scattering method was applied to evaluate macromolecular parameters of defated proteinous silk fibers like Eri, Muga, Tussah, and raw silk. For the experimental measurement of scattering intensities the small‐angle Kratky camera, coupled with an automatic‐step scanning device, pulse‐height discriminator, and counter attachment was used. Macromolecular parameters like specific inner surface, percentage of void, length of coherence, range of inhomogeneity, and transversal length were evaluated by using the theories of Kratky, Porod and Debye, and Bueche. The physical properties of these defated fibers were also evaluated with Scott's IP2‐inclined plane tester. The correlation of the tertiary structural parameters with textile properties like average breaking strength of the proteinous fibers indicated a dependence of physical properties on certain macromolecular parameters.
Curing epoxy resins with anhydrides. Model reactions and reaction mechanism
Authors: Matějka L. , Lövy J. , Pokorný S. , Bouchal K. , Dušek K.
Published: April 2003

The mechanism of acid curing of epoxy resins catalyzed with tertiary amines was investigated by using model systems composed of phenylglycidyl ether and benzoic acid or acetic acid anhydrides in the presence of benzyldimethylamine. The reaction was studied by NMR spectrometry, liquid chromatography, and ozone absorption. The main findings are that (1) the tert‐amine is bound chemically and irreversibly during the reaction under the formation of a quaternary ammonium salt
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and (2) 1‐phenyloxypropanediol‐2,3‐dibenzoate or diacetate is the main reaction product. The suggested reaction mechanism involves initiation in which the tertiary amine reacts with the epoxy group, giving rise to a zwitterion that contains a quaternary nitrogen atom and an alkoxide anion; the latter immediately reacts with the anhydride and quaternary salt is formed. In a later stage the carboxy anion of the quaternary salt reacts first with the epoxy group, then with the anhydride. By this reaction diester is formed and the carboxy anion is regenerated.
Novel polyurethanes with macroheterocyclic (crown‐ether) structures in the polymer backbone
Authors: Herweh J. E.
Published: April 2003

The synthesis of a functionalized crown ether was accomplished in two steps by condensing 3,4‐dihydroxybenzaldehyde with bis(2‐chloroethyl)ether and subsequent reduction of the reaction product, bis(formylbenzo)‐18‐crown‐6 (4) to a diol (5). Polyurethanes that bear the dibenzo‐18‐crown‐6 moiety in the polymer backbone were synthesized from bis(methylolbenzo)‐18‐crown‐6 (5), a polypropylene glycol, and methylene bis(4‐cyclohexyl isocyanate). The resulting polymers were fibrous white solids with glass transitions from ca. 15–120°C, depending on the starting diol composition. The thermomechanical spectra of melt pressed or solvent cast films of several crown‐ether‐bearing polyurethanes showed evidence of multiphase character. The polymers failed to complex effectively with sodium ions. However, their complexing ability with potassium ion was similar in magnitude to that observed with relatively simple crown ethers.
Phase transfer catalysis in dehydrofluorination of poly(vinylidene fluoride) by aqueous sodium hydroxide solutions
Authors: Kise Hideo , Ogata Hiroshi
Published: April 2003

The reaction of poly(vinylidene fluoride) (PVDF) powder with aqueous sodium hydroxide solutions in the presence of quaternary ammonium or phosphonium halides as phase transfer catalysts afforded dehydrofluorinated polymers. The structure of the products was investigated by infrared spetroscopy, and a fluorine‐substituted conjugated polyene structure was suggested which was found to be stable against air oxidation. Tetrabutylammonium bromide and tetrabutylphosphonium bromide were the most active among the catalysts used. The effects of the reaction conditions on the conversion are described. The treatment of PVDF films under phase transfer conditions increased the wettability of the surface and electric conductivity. The reaction of PVDF with potassium hydroxide in 2‐propanol proceeded not only by elimination but also by substitution of hydroxide ions.
Synthesis, characterization, and diels–alder extension of cyclopentadiene telechelic polyisobutylene. IV. α,ω‐Di(3‐cyclopentadienylpropyldimethylsilyl)polyisobutylene
Authors: Kennedy J. P. , Carlson G. M.
Published: April 2003

The synthesis and chain extension of polyisobutylene having nonfluxional terminal cyclopentadiene groups is described. The fluxional behavior of silylcyclopentadiene end groups was previously found to prevent Diels–Alder dimerization of the end groups. The incorporation of a propyl moiety between the silicon atom and the cyclopentadiene ring was found to prevent this fluxional isomerization. Polyisobutylene was synthesized having 3‐cyclopentadienylpropyldimethylsilyl end groups with a functionality near 2.0. While thermal extension at 80°C resulted in threefold molecular weight increase, coupling with bisdienophiles yielded greater than tenfold molecular weight increases. The retro‐Diels–Alder reaction of coupled end groups prevents the attainment of high‐molecular‐weight polymers at equilibrium.
The synthesis of poly(styrene‐co‐sodium styrene‐p‐carboxylate)
Authors: Brockman N. L. , Eisenberg A. E.
Published: April 2003

This article describes a technique for the homogeneous lithiation and subsequent carboxylation of high‐molecular‐weight polystyrenes containing up to 14 mol %p‐bromostyrene. Thus, poly(styrene‐co‐p‐bromostyrene)s were reacted in dilute tetrahydrofuran solution with large stoichiometric excesses ofn‐butyllithium with no precipitation of ionomer and subsequently carboxylated with anhydrous carbon dioxide or dry ice. By this technique polystyrenes in which up to 100% of the original bromine groups had been replaced by carboxyl functionalities were obtained.
Diffusion of acid dyes in nylon film in the presence of inorganic salts
Authors: Kumazawa Hidehiro , Sada Eizo , Ando Tetsuo
Published: April 2003

The concentration‐dependence measured by steady‐state permeation and unsteady‐state dyeing methods for a system of acid dye C.I.Acid Blue 182–nylon 6 film in the presence of inorganic salts such as NaCl, Na2SO4, and K2SO4, was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption. It would found that the dyeing process with added NaCl was governed by surface diffusion with two kinds of Langmuir adsorption, whereas with added Na2SO4 and K2SO4 it was governed by surface diffusion with three kinds of Langmuir adsorption.
The effect of organic nitriles on the radiation induced polymerization of styrene
Authors: Guthrie J. T. , Squires L. J.
Published: April 2003

The effect of a range of 10 organic nitriles on the radiation‐induced polymerization of styrene was studied. A dose rate of 4.4 rad s−1 was used. A rate of polymerization of styrene (1.744 mol L−1 of toluene solution) of 5.0 × 10−7 mol L−1 s−1 was found. With organic nitriles present (styrene:nitrile ratio of 1:0.28) the rate of polymerization increased. Rates in the range of 5.5 × 10−7 −5.2 × 10−6 mol L−1 s−1, depending on the nitrile present, were obtained. The polymers were partially characterized and evidence of involvement of each of the nitriles in the polymer chains was revealed. The increase in rate of polymerization has been attributed to the part played by nitrile radicals in the initiation of styrene polymerization. Radical yield values [as G(nitrile radical)] were derived from the relevant rate expressions. Values ranged from 2.7 to 49.5, depending on the particular nitrile. Corresponding values of G(nitrile radical) in the range of 5.1–129.4 were obtained by the manipulation of number‐average molar mass data. Values of kpkt of approximately 2 × 10−5 L mol−1 s−1 were found. Trommsdorff types of effect are absent from these systems.
Acrolein polymerization: Monodisperse, homo, and hybrido microspheres, synthesis, mechanism, and reactions
Authors: Margel Shlomo , Wiesel Erika
Published: April 2003

Monodisperse polyacrolien (PA) microspheres were obtained by a single step process via two mechanisms: (a) aqueous polymerization of acrolein under alkaline conditions and (b) aqueous radical polymerization of acrolein by irradiation with a cobalt source. The diameter of the former microspheres can be varied from 0.04 up to 8 μm. The monodispersity of the system is also discussed. The diameter of the latter microspheres can be varied up to 0.2 μm. Hybrido PA microspheres were formed by grafting PA microspheres of average diameter of 0.1 μm obtained by irradiation onto the surface of PA microspheres produced by the alkaline mechanism. The aldehyde content of the microspheres prepared by irradiation is much higher than those of the microspheres formed under alkaline conditions. The aldehyde groups were used for the covalent binding of ligands containing primary amino groups, such as proteins and drugs, in a single step under physiological pH.
Radiolysis of resist polymers. III. Copolymers of methyl‐α‐chloroacrylate and trihaloethylmethacrylates
Authors: Babu G. N. , Lu P. H. , Hsu S. L. , Chien James C. W.
Published: April 2003

Homopolymers of 2,2,2‐trifluoroethyl(methacrylate) (TFEMA) and 2,2,2‐trichloroethyl‐(methacrylate) (TCEMA) and copolymers with methyl‐α‐chloroacrylate (MCA) in a range of compositions were synthesized. The reactivity ratios were obtained; the two copolymerizations were close to ideal. Poly(MCA) showed Gs = 7.4 and Gs = 0.9 by γ‐radiolysis. On the other hand, poly(TFEMA) and poly(TCEMA) and Gs values of 2.0 and 2.4, respectively, and Gx = 0. Radiolysis of copolymers was initiated to a large degree by dissociative electron capture by the halogen atoms in both comonomers, as revealed by the ESR spectra of radicals derived from them. Germinal recombinations in irradiated poly(TFEMA) suggested the presence of radicals in proximity. This process was absent in the copolymers. GC‐MS analysis of volatile products and other supporting evidence showed that TFEMA monomers tended to depolymerize; the TCEMA monomers did not. The radiolysis yields varied monotonically with the comonomer composition for the MCA–TFEMA system but the yield–composition relationship was irregular in MCA–TCEMA copolymers. Four noncrosslinking systems are potential radiation resists arranged in increasing order of promise: poly(TFEMA) (Gs = 2.0, Tg = 70°); poly(TCEMA) (Gs = 2.7, Tg = 142°); poly(94MCA‐co‐6TCEMA) (Gs = 2.7, Tg = 142°); and poly(68MCA‐co‐32TFEMA) (Gs = 3.0, Tg = 112°). These materials merit further investigation for E‐beam or x‐ray lithographic applications. Mechanisms of radiolysis for these materials, based on ESR, GC‐MS, and radiolysis yield data, were discussed.
Lyotropic mesophases of hydroxypropylcellulose in pure acetic acid, in water, and in mixed solvents
Authors: Fried F. , Sixou P.
Published: April 2003

Photomicrographys of concentrated lyotropic hydroxypropylcellulose solutions confirm the cholesteric nature of the anisotropic phases in acetic acid and water. They reveal the existence of biphasic separation. Typical liquid‐crystal solvent‐dependent textures are observed. The behavior of liquid‐crystalline phases in mixed solvents is also studied, and the cholesteric pitch of the twist structure is measured for various relative concentrations of solvents. Spherical droplets, or “spherulites,” in well‐defined relative concentrations of solvents have been observed.
Multifunctional polycondensation distributions: A kinetic approach to mixed monomer systems
Authors: Stafford J. W.
Published: April 2003

The size distributions of a number of multifunctional polycondensations which contained mixtures of monomers of different functionalities were derived from kinetic reaction schemes. The distributions obtained were in agreement with those derived by other authors on similar systems. The distribution functions differed, however, from those obtained by a kinetic method by using mean functionalities of the monomer mixtures; the reasons for the differences were explored. Size distribution parameters also obtained were used to consider the differences between actually observed gel points and gel points calculated for multifunctional polycondensing systems.
Radical polymerization behavior of N,N‐disubstituted acrylamide: Absolute rate constants for polymerization and copolymerization of N‐acryloylpiperidine
Authors: Yamada Bunichiro , Yoshioka Minoru , Otsu Takayuki
Published: April 2003

The absolute rate constants of propagation (kp) and of termination (kt) of N‐acryloylpiperidine (NAPi) were determined by the rotating sector method in bulk; kp = 273 and kt = 1.79 × 107 L/mol s at 30°C. It was noted that kp for NAPi was 100 times smaller than that for N,N‐dimethylacrylamide (DMAcAm). The absolute rate constants of cross‐propagations for copolymerizations with common monomers were evaluated by combination of the kp value and the monomer reactivity ratios. Quantitative comparison of the rate constants with those of DMAcAm and poly(DMAcAm) radical shows that NAPi is as reactive as DMAcAm and the smaller kp value for NAPi is ascribable to much the lower reactivity of the poly(NAPi) radical. The large difference in reactivity of the polymer radicals is discussed in relation to the steric factor of the piperadino and the dimethylamino groups which seems to affect the capability of the carboxamide group to stabilize the polymer radical.
Functional monomers and polymers. CXIII. Photoinduced conformational change of thymine containing poly‐lysine derivatives
Authors: Suda Yasuo , Inaki Yoshiaki , Takemoto Kiichi
Published: April 2003

The photodimerization reaction between thymine bases in thymine‐grafted poly‐D‐ and poly‐L‐lysine derivatives was studied in an alkaline, aqueous, buffered solution. It was found that the helix content of the polymers changes by photodimerization. The result was discussed in terms of conversion, the rate of photodimerization, and the helix content of the polymers.
Tetraalkyl titanium and zirconium metal chloride catalyst systems for ethylene polymerization
Authors: Herskovitz Thomas
Published: April 2003

Coordination polymerization of olefins has become an industrially important, yet still poorly understood enterprise. The ethylene polymerization activity of (neophyl)nZrCl4‐n shows a twentyfold increase from n = 4 to n = 3 and a further tenfold increase to n = 2. The heterogeneous MR4/TiCl4 catalysts (M = Ti, R = benzyl; M = Zr, R = benzyl, neophyl) have been developed. To explore the breadth of extendability, other metal chlorides (main group and transition metal) were substituted for TiCl4. Indeed, excess AlCl3 or MgCl2 and the MR4 compounds also produced ethylene polymerization catalysts. The inactivity of corresponding (neophyl)4Ti systems is attributed to sterics. The abovementioned catalysts highlight the necessity of alkyl and chloride ligands at the transition metal catalyst centers.
Preparation of polysiloxanes from silicic acid. V. Condensation of silicic acid butyl esters and formation of silica fiber from the ester solutions
Authors: Abe Yoshimoto , Sekiguchi Tetsushi , Misono Takahisha
Published: April 2003

The condensation of silicic acid butyl esters was investigated by gel permeation chromatographic (GPC) analysis. The results revealed that the condensation was greatly dependent on a degree of esterification of the esters. The ester with the lowest degree of esterification underwent condensation to form a highly polymerized ester. It was found that fibers could be drawn from the ester solution before gelation.
Radical copolymerization of acrylic monomers. VI. Copolymerization of methyl methacrylate with methyl α‐benzylacrylate
Authors: Madruga E. L. , San Román J. , Lavia M. A.
Published: April 2003

Free‐radical copolymerization of methyl methacrylate and methyl α‐benzylacrylate has been studied in benzene solutions at 40 and 60°C. A simple copolymerization model fits the composition data at both temperatures. However, considering that the ceiling temperature for the polymerization of methyl α‐benzylacrylate in benzene solution (|M| = 5 mol/L) is 67°C and that the overall rate of copolymerization drastically decreases with respect to that of methyl methacrylate homopolymerization with an increase of the molar fraction of methyl α‐benzylacrylate in the feed, the behavior of this system is analyzed from both simple and reversible copolymerization models.
Solid products from thermal decomposition of polyethylene terephthalate: Investigation by CP/MAS 13C‐NMR and fourier transform‐IR spectroscopy
Authors: Suebsaeng Thitivat , Wilkie Charles A. , Burger Vern T. , Carter Janet , Brown Charles Eric
Published: April 2003

The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13C‐NMR, FR‐IR, and MAS 31P‐NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO2, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation.
Vinyl polymerization initiated by peroxydiphosphate. XII. Polymerization of acrylamide and acrylic acid by peroxydiphosphate–sodium thiosulfate redox system
Authors: Lenka Subasini , Nayak Padma L. , Ray Suparna
Published: April 2003

The aqueous polymerization of acrylic acid and acrylamide initiated by peroxydiphosphate–sodium thiosulfate redox system was investigated within the temperature range of 25–35°C. The rates of polymerization were measured at different concentrations of oxidant, activator and monomer. The monomer and the initiator exponents were evaluated to be 1.12 and 0.51. The rate of polymerization decreases with increasing thiosulfate concentration. On the basis of the experimental observation of the dependence of the rate of polymerization, Rp, on various variables, a suitable kinetic scheme has been proposed and the rate parameters have been evaluated.
Spectrophotometric studies of some charge‐transfer complexes of tetracyanoethylene with poly(N‐vinyl halogenocarbazoles)
Authors: Pielichowski Jan , Sanetra Jerzy
Published: April 2003

The results and numerical analysis of measurements of absorption spectra of charge‐transfer complexes of poly(N‐vinyl halogenocarbazoles) with tetracyanoethylene are presented. The absorption bands result from donor–acceptor interaction together with values of equilibrium constants, enthalpy, and oscillators strengths of investigated complexes allowed us to conclude that isomerism of complexing took place. The influence of halogen substituents (mono‐ and disubstitution) in positions 3 and 6 of the carbazole ring (polymeric donor) on the spectral properties of its complexes was observed.
Polymerization of terminal alkynes by a new Ziegler–Natta catalyst system: Scandium naphthenate/trialkylaluminum
Authors: Shen Zhiquan , Farona Michael F.
Published: April 2003

The scandium naphthenate/trialkylaluminum system was investigated as a catalyst in the polymerization of substituted alkynes. Phenylacetylene was converted to a moderately crystalline, high cis polymer. The alkyl‐substituted acetylenes produced rubbery or solid materials of relatively high molecular weight. Infrared (IR), ultraviolet (UV), 1H‐NMR, and 13C‐NMR studies of the polyalkylacetylenes revealed high cis conformation, but apparently twisted from planarity to decrease molecular orbital overlap in the polyconjugated chain.