bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anionic polymerization of octamethylcyclotetrasiloxane in aqueous emulsion I: Preliminary results and kinetic study
Authors: De Gunzbourg Anémone , Favier Jean‐Claude , Hémery Patrick 
Published: April 2003

AbstractThe synthesis of poly(dimethylsiloxane) (PDMS) by anionic polymerization of octamethylcyclotetrasiloxane (D4) in aqueous emulsion using an emulsifying agent acting also as initiator (benzyldimethyldodecylammonium hydroxide) is described. Stable emulsions of α,ω‐dihydroxy PDMS with an easily controlled molar mass (up to 15 000), a low polydispersity index and high yields were obtained. The amount of cyclics formed (essentially D4 to D7) is lower than that observed in bulk. Kinetics analysis and computerized simulations are in good agreement with a reaction scheme involving simultaneous polyaddition/polycondensation processes. At high monomer consumption, polycondensation predominates leading to a broadening of the molecular weight distribution (MWD). The apparent rate constants of initiation, propagation and condensation at various temperatures and the corresponding activation energies were determined.
Characterising the chemical interactions that occur on polyaniline with inverse thin layer chromatography
Authors: Teasdale P. R. , Wallace G. G. 
Published: April 2003

AbstractInverse thin layer chromatography is used to characterise the chemical interactions that occur on polyaniline that has been electrochemically deposited on to a support. Amino acids are used as the molecular probe species by which the retention behaviour can be related to particular chemical interactions. The mobile phase is also varied, with respect to its polarity and pH, in order to add a further dimension to the qualitative information that is obtained. Anion exchange interactions are found to be the dominant interaction type. However, the behaviour seems to be different to that which occurs on conventional anion exchange materials. The behaviour was dependent upon the number of negative sites and also their spatial arrangement. A configurational‐selective ionic interaction with the polaron lattice of the polyaniline is proposed. The response of the anion exchange behaviour to a change of pH suggested that protonated sites remained within the polymer, even at high pH values (c 9).
Synthesis of highly isotactic (mm > 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et2Be) in xylene at 130°C, the (mm) content as well as the viscosity‐average molecular weight (MÞv) of PAN increased by addition of diisobutylaluminum hydride (i‐C4H9)2AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i‐C4H9)2AlH/Et2Be > 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et2Be and di‐n‐hexylamagnesium ((Et2Be/(n‐C6H13)2 Mg system), where both Et2Be and (n‐C6H13)2 Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et2Be/(n‐C6H13)2 Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et2Be alone ((mm) = 0.56) and (n‐C6H13)2Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in 13C chemical shifts of α‐carbons between Et2Be (1.35 ppm) and (n‐C6H13)2Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et2Be induces the stereospecific polymerization in the Et2Be/(n‐C6H13)2Mg system as initiator, the main role of (n‐C6H13)2Mg is considered to be the suppression of the association of Et2Be (active site) itself.
Electropolymerization and characterization of terpyridinyl iron (II) and ruthenium (II) complexes
Authors: Hanabusa Kenji , Nakamura Atsushi , Koyama Toshiki , Shirai Hirofusa 
Published: April 2003

AbstractElectroactive 2,2′: 6,2″‐terpyridinyl ligands (3, 5, 6) and their iron(II) (7a–9a) and ruthenium(II) complexes (7b–9b) were synthesized. Bis[3‐(aminophenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes (7a, 7b) and bis[2‐(hydroxyphenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes (8a, 8b) were electropolymerized on to the surface of Pt or In‐SnO2 (ITO) electrodes in acetonitrile containing Bu4NCIO4 by scanning the potential between O and + 1.6V (for 7a and 7b), and −0.8 and +1.6V (for 8a and 8b) versus saturated calomel electrode. The electrodes obtained by electropolymerization exhibited reversible electrochromism based on Fe(II)/Fe(III) or Ru(II)/Ru(III) redox couple. Photoresponses to visible light were found in the modified electrode obtained by electropolymerization of ruthenium complex 7b in an aqueous LiClO4 solution containing methylviologen (cation MV2+) under an O2 atmosphere. The mechanism for the photoresponded cathodic current was explained in terms of an excitation of bis(terpyridinyl)ruthenium(II) complex [Ru(terpy)22+] by visible light, an electron transfer from the excited state [Ru(terpy)2+*2] to MV2+, reduction of Ru(terpy)3+2 at an electrode, and oxidation of MV+* with O2.
Carbon membranes from precursors containing low‐carbon residual polymers
Authors: Linkov Vladimir M. , Sanderson Ron D. , Jacobs Ed P. 
Published: April 2003

AbstractAsymmetrical hollow‐fibre carbon membranes with increased porosity were obtained by carbonization of polyacrylonitrile based precursors containing high quantities of polymers, such as polyethylene glycol and polyvinylpyrrolidone, which give low‐carbon residue upon pyrolysis. The interaction between molecules of the two polymers, which could serve as evidence of at least partial miscibility of these polymers, occurred only with PVP‐containing precursors. The narrowest pore‐size distribution was inherent in carbon membranes produced from such precursors.
Highly isotactic polyacrylonitriles prepared using dialkylmagnesium/water systems as initiators
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to synthesize stereoregular polyacrylonitrile (PAN) with high molecular weight (e.g. viscosity‐average molecular weight (M̄v) > 1 × 105) by anionic polymerization. The triad tacticities (i.e. the content of mm, mr and rr (m, meso; r, racemo)) of the polymers obtained were analyzed by 13C NMR and their M̄v was determined by viscometry in dimethylsulfoxide at 25°C using Kamide et al.'s Mark–Houwink–Sakurada equation. Highly isotactic and high molecular weight PAN with M̄v > 2.5 × 105 ((mm) ∼ 0.57) was synthesized in anisole at 130°C when the reaction product of di‐n‐hexylmagnesium with water supplied by heating sulfate hydrates (Na2SO4 10H2O, CuSO4 5H2O, and MgSO4 7H2O) was used as a polymerization catalyst. The M̄v of PAN was increased significantly by using the catalyst combined with triethylaluminum (Et3Al). Maximum M̄v attained was 9.7 × 105 ((mm) = 0.64). The main role of Et3Al added is explained as the reduction of OH groups in the catalyst and of residual H2O in the catalyst solution.
Kinetics of nitroglycerine migration through unsaturated non‐halo and halo polyesters
Authors: Agrawal J. P. , Kulkarni K. S. 
Published: April 2003

AbstractThe diffusion coefficients (D) of nitroglycerine (NG) migration through cured non‐halo and halo polyesters have been calculated with the help of M∞ determined experimentally and Fick's Law. The calculated NG migrations at different time intervals compare very closely with the corresponding NG migrations determined experimentally. The concentration profiles at various locations in thin sheets of non‐halo and halo polyesters have also been calculated.
Hydrocarbon‐soluble difunctional organolithium anionic initiators. A gas–liquid chromatographic study of the reaction of sec‐butyllithium with m‐divinylbenzene
Authors: Sanderson Ronald D. , Roediger Andrew H. A. , Summers Gabriel J. 
Published: April 2003

AbstractQuantitative gas–liquid chromatography provides an efficient, novel technique for the kinetic study of the reaction between sec‐butyllithium and m‐divinylbenzene. The reaction of stoichiometric amounts of ultra‐high purity sec‐butyllithium with pure m‐divinylbenzene at −23°C produces an anionic initiator, 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene, 2, without traces of monofunctional and polyfunctional impurities. The relative rates of formation of 2 with and without the presence of Lewis base, triethylamine, or Lewis acid, diethylzinc, were studied by gas–liquid chromatography. The presence of diethylzinc reduces the activity of sec‐butyllithium to such an extent that the reaction did not proceed beyond the monofunctional component stage, that is, the formation of m‐1‐lithio‐3‐methylpentylvinylbenzene, 1. The reaction of sec‐butyllithium with m‐divinylbenzene at −79°C with a 10mol% ratio of triethylamine to sec‐butyllithium yielded a homogeneous product with composition of 94% difunctionality and 6% monofunctionality, with the total disappearance of m‐divinylbenzene as observed by GLC. However, precipitation due to agglomeration was observed at 25°C at 100% conversion.The high purity 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene initiator, 2, is effective for the polymerization of 1,3‐butadiene and allows the synthesis of polybutadienes with predictable molecular weights and narrow molecular weight distributions. Depending on the polymerization solvent, polybutadienes with microstructures ranging from 9 to 13% 1,2‐vinyl content were observed by 1H NMR analysis and FTIR spectroscopy. However, the presence of diethylzinc retards the rate of polymerization of 1,3‐butadiene, without any change in polymer microstructure. Triethylamine enhances the rate of 1,2‐enchainment without significant reduction in the 1,4‐enchainment of polybutadiene.
Monolayer formation of chitin derivatives containing PMMA side‐chains
Authors: Ren Long‐Di , Goto Yasutomo , Kaneko Hiroaki , Shirai Akihiro , Nishi Norio , Nishimura Shin‐Ichiro , Yamagishi Akihiko , Tokura Seiichi 
Published: April 2003

AbstractThe monolayer behaviour of poly(methyl methacrylate) (PMMA)‐grafted chitin derivatives was studied on an air–water interface by measuring surface pressure–area isotherms. The formation of a stable monolayer indicates the well‐defined packing and orientation of the chitin derivative, which can be regulated by the main‐chain length under appropriate experimental conditions. The isotherms exhibit a transition point from a liquid expanded phase to a condensed phase at a surface pressure of approximately 15mN/m for almost all monolayers examined. The transition pressure decreases with increase of temperature from 10 to 20°C. The properties of the sub‐phase affected the formation of a monolayer greatly. The collapse of a surface film takes place at lower pressure on the sub‐phase of a 0.1 M NaCI solution. After introducing lysozyme at a concentration at 2.4 × 10−8M to the sub‐phase, the monolayer showed an extensively expanded phase with a longer transition region. This indicates that the monolayer was degraded by the lysozyme, resulting in a disordered structure. The results are contrasted with those of an aqueous phase where N‐acetylglucosamine residues may be inaccessible to lysozyme so that the degradation of the chitin derivative occurs at a very slow rate.
DC electrical conduction in solution‐grown pure and iodine‐doped poly(butylene terephthalate) films
Authors: Dasaradhudu Y. , Rao V. V. R. Narasimha 
Published: April 2003

AbstractDC electrical conduction in poly(butylene terephthalate) films sandwiched between planar aluminium electrodes was investigated. The films were grown by the isothermal immersion technique. The conduction process was studied in the temperature range 300–450K, with an applied electric field of 0.22 × 107−6.66 × 107 Vm−1. It was found that the Richardson‐Schottky type of conduction mechanism was dominant throughout the temperature range of study. The values of the Schottky field lowering constant β, the effective metalinsulator potential barrier and the activation energy were evaluated. The value of the activation energy (U = 0.7 eV) indicates the predominance of electronic conduction. The effect of impurities like iodine on electrical conduction was also investigated.
Gamma‐radiation damage to polyamide‐1010 crystal structure
Authors: Zhang Lihua , Zhang Hongfang , Yu Li , Zhang Wende , Mo Zhishen , Chen Donglin 
Published: April 2003

AbstractRadiation effects on polyamide‐1010 specimens having various states of aggregation were studied using wide angle X‐ray diffraction, electron spin resonance, calorific and sol measurement techniques. Experimental results indicated that chain crosslinking and scission of the irradiated polyamide‐1010 occurred mainly in the amorphous region and on the crystal surface. The radiation‐induced crystal damage and amorphotization started from the crystal surface (or interface) and extended into the inner portion of the crystal with increasing radiation dose. It is believed that the interface between crystalline and amorphous regions was the main region wherein free radicals were trapped.
β‐relaxation of drawn isotactic polypropylene in terms of a simplified two phase model
Authors: Jawad S. A. , Alhaj‐Mohammad M. H. 
Published: April 2003

Abstractβ‐Relaxation in die‐drawn isotactic polypropylene (i‐pp) is associated with a glass transition temperature and depends on the mobility of the molecules in the amorphous regions. A simplified two phase model was employed to explain the decrease in the intensity of the β‐process peak upon drawing. The model predicts that the decrease in the loss factor (tan δ) upon drawing is associated with a change in continuity from a series to a parallel situation.
Free radical two step synthesis of styrene and acrylate block copolymers with disulphide initiators
Authors: Opresnik Marko , Šebenik Anton 
Published: April 2003

AbstractControlled two step block copolymerization of styrene, methyl methacrylate and ethyl acrylate with aliphatic and aromatic disulphides under UV irradiation took place in bulk and in THF solution. In the first step of the polymerization, the most reactive system was ethyl acrylate with aromatic disulphides.The molecular weights and yields of polymerizations increased with reaction time. The macromolecules were terminated by primary. SR radicals and by combination of two macroadicals which was observed by NMR spectroscopy. Aninsignificant portion of uninitiated photopolymerization was detected only for MMA. In the second step of polymerization, the purified macroinitiators from the first step reacted with additional monomers to form block copolymers with a small quantity of unreacted macroinitiator. The molecular weights of copolymers increased, the bonding segments between the blocks being detected by 1H NMR. The overall reaction is an insertion of monomers between two thiyl groups.
Polymerization of ethylene oxide by the activated monomer mechanism
Authors: Manolova Nevena , Libiszowski Jan , Szymanski Ryszard , Penczek Stanislaw 
Published: April 2003

AbstractThe Polymerization of ethylene oxide catalysed by protonic acids and proceeding via the activated monomer mechanism differs from the polymerizations of substituted epoxides like propylene oxide and epichlorohydrin. The kinetics of ethylene oxide polymerization were investigated and compared with the kinetics of model reactions, namely addition of oligomers of ethylene oxide to ethylene oxide. The mechanism of polymerization involves, besides the addition of monomer to the terminal hydroxyl groups, the addition to the polymer ether groups. This reaction does not take place for substituted oxiranes, most probably because of steric hindrance.
Polymerization of t‐butylacetylene initiated by tungsten carbene complex
Authors: Liaw Der‐Jang , Lin Cheng‐Len 
Published: April 2003

AbstractPolymerization of t‐butylacetylene initiated by a tungsten carbene complex (I) was investigated under various conditions. t‐Butylacetylene was polymerized in high yield in chlorinated hydrocarbons such as CHCI3 and CCI4 and in the presence of AICI3. The molar mass of the polymers formed was as high as 8.2 ×104 ∼ 3.2 × 105. Moreover, when the solution of tungsten carbene complex in CCI4 was irradiated with UV light, the molar mass was remarkably enhanced. This phenomenon may occur because tungsten dichlorocarbene immediately forms. Apparent rate constants were determined by gas chromatography. NMR spectra show a predominant characteristic of high cis content in the structure of poly(t‐butylacetylene) in contrast to poly(phenylacetylene). The cis content increased ca. 11% when poly(t‐butylacetylene) was heated in decalin at 110°C. X‐Ray diffraction diagrams show that poly(t‐butylacetylene) has an amorphous structure.
Macromonomers by activated polymerization of oxiranes. Synthesis and polymerization
Authors: Biedron Tadeusz , Brzezinska Krystyna , Kubisa Przemyslaw , Stanislaw Penczek  
Published: April 2003

AbstractMacromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by the activated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DPn ∼ 15 for propylene oxide and DPn ∼ 20 for epichlorohydrin, polymerization proceeds as a living process, giving with quantitative yields macromonomers with functionality equal to one, controlled molecular weight and narrow molecular weight distribution (MwMn<1.2) free of side products. In the higer molecular weight region, side reactions become increasingly noticeable. Propylene oxide macromonomers undergo radical homopolymerization. Homopolymerization of macromonomer with Mn = 8×102 gives graft copolymers with Mn up to 7.2×103 in copolymerization with styrene, completely soluble graft copolymers with Mn ∼ 2×104 were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with Mn ∼ 6×104 were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with Mn∼ 6×104, which are converted in the later stages into insoluble gels, apparently due to the chain transfer to chloromethly groups of the polyepichlorohydrin chains.
Photopolymerization of carbazolyloxiranes
Authors: Gražulevičius Juozas V. , Kavaliūnas Rimtautus , Lazauskaitė Rūta 
Published: April 2003

AbstractPhotopolymerizations of 1‐allyloxy‐3‐(carbazol‐9‐yl)‐2‐propanol glycidyl ether and 1‐(carbazol‐9‐yl)‐4‐oxa‐2‐pentanol glycidyl ether with diaryliodonium salts in solution and in bulk are reported. These reactions give oligomers of degree of polymerization 4–6. The influence of the functional groups of the monomers on the rate of polymerization, conversion limit and molecular weight is discussed. The effects of photoinitiator and reaction media on these factors have also been studied.
Molecular dynamics simulations of macroscopic vibrations on cooling of superheated polyethylene crystals
Authors: Kreitmeier Stefan N. , Liang Guanghe L. , Noid Donald W. , Wunderlich Bernhard 
Published: April 2003

AbstractIn this paper a discussion is given of the change of density with time and temperature within a crystal of 192 (CH2)50 chains, simulated by molecular dynamics computations at temperatures from 65 to 425 K. The highest temperatures exceed the melting temperature (about 365K). On simulation for times of up to 100 ps the temperature dropped through the melting temperature, permitting the study of the behavior of the crystal during initial melting, followed by limited recrystallization. In these short times only a limited number of chains on the surface can begin to coil and melt conformationally, but there is an indication of a disordering transition. A better comparison with experimental data on density, expansivity and speed of sound is possible.
Organo‐soluble aromatic polyamide films
Authors: Lee Chul Joo , Park Seung Koo , Kim Sang Yup , Lee Yun Joo , Min Byung Ghyl , Son Tae Won , Kim Byong Chul 
Published: April 2003

AbstractTo make stable isotropic aramid solutions and films, 6‐amino‐2‐(4‐aminopheyl)‐4‐phenyl quinoline (QDA) was used as base diamine, and copolymerized using terephthaloyl chloride (TPC) with p‐phenylene diamine (PPD), 2,2′‐bis(trifluoromethyl)benzidine (PFMB), and oxydianiline (ODA) as second diamine, respectively. Homogeneous viscous polymerization solutions based on QDA were obtained, and films prepared from them were transparent and amorphous. The reactivity of QDA with TPC was almost equal to that of PPD; the reactivity of PFMB was low due to the electron withdrawing groups (CF3) attached to the ortho positions of the benzene rings. Bulkiness and flexibility of the monomer structure widened the of stable conditions in polymer solution. A rod‐like structure of the monomer caused drawbility to decrease. QDA/ODA copolymer films could be drawn well, probably as a result of the flexible linkage of ODA, and had high tensile strength (86 kg/mm2). High modulus, 3.1 × 103 kg/mm2, was obtained in QDA/PPD copolymer films. Tensile strength and modulus increased with draw ratio. Tg and Tm were not seen by DSC and Td of the polymers was as high as c. 500°C. Excess drawing caused the films to be fibrillated, affecting their tensile properties.
Formation and relative reactivity of comonomer H‐complexes in the radical copolymerization of acrylic acid with 1‐vinyl‐2‐pyrrolidone
Authors: Georgiev George S. , Koseva Nely S. , Christov Latchezar K. 
Published: April 2003

AbstractThe dimerization constant (Kg) of acrylic acid and the association constant of the comonomer complex between acrylic acid and 1‐vinyl‐2‐pyrrolidone (K1) have been determined in chloroform by means of IR and 1H NMR spectroscopy: Kd=(2.0±0.2) × 103litre mol−1 and K1=68.5±0.5 litre mol−1. A detailed equation for the copolymer composition considering the participation of the intermolecular complexes in the chain propagation has been derived with the help of a specific regular three addition states Markov chain. Applying a numerical procedure for fitting the experimental curve for the comonomer composition, this equation has been used in the estimation of the dimer and the comonomer complex relative reactivities. The considerably higher reactivities of the two complexes compared with that of the monomers are accounted for by the π‐electrons' greater delocalization in the transition states involving the complexes species.
Thermal and mechanical properties of poly(esterurethane) modified by copolyamide segments of various molecular weight
Authors: Ahn Tae Oan , Oh Myung‐Hwan , Yoo Kwang Sik , Jeong Han Mo 
Published: April 2003

AbstractThermoplastic polyurethane elastomers (TPUs) from diol‐terminated poly(ethylene adipate) (PEA), 1,4‐butanediol (BD) and 4,4′‐diphenylmethane‐diisocyanate (MDI) were modified by copolymerizing with diamine‐terminated nylon‐6/6,6 copolyamide (CPA) oligomers. The effects of content and molecular weight of CPA segments on the thermal and mechanical properties of TPU were studied. PEA segments showed enhanced crystallization when some of the hard segments were replaced by CPA segments, showing weaker CPA–PEA interaction. The crystallinity of the hard segments was reduced, probably due to some interaction and phase mixing between hard and CPA segments. The modulus of TPU also decreased, more markedly with CPA segments of higher molecular weight.