bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixed (electronic and ionic) conductive solid polymer matrix, 1. Synthesis and properties of poly(2,5,8,11,14,17,20,23‐octaoxapentacosyl methacrylate)‐block‐poly(4‐vinylpyridine)
Authors: Li Jean , Khan Ishrat M. 
Published: April 2003

AbstractPoly(2,5,8,11,14,17,20,23‐octaoxapentacosyl methacrylate)‐block‐poly(4‐vinylpyridine) semicomb polymers were synthesized using anionic living polymerization techniques. The polymers are white, powdery materials and were characterized by 1H and 13C nuclear magnetic resonance spectroscopy and gel‐permeation chromatography. The polymers display monomodal molecular weight distributions which are relatively narrow. The block copolymers show microphase separation as indicated by the presence of two glass transition temperatures (Tg), a soft (oxyethylene) phase Tg is observed between −60°C and −45°C and a hard (4‐vinylpyridine) phase Tg is observed between 135°C and 150°C. The soft oxyethylene phase has been doped with LiClO4 to obtain ionic conductors with electrical conductivities around 5 · 10−6 S · cm−1 at 25°C and the hard 4‐vinylpyridine phase has been complexed with 7,7,8,8‐tetracyano‐1,4‐quinodimethane (TCNQ, 2,5‐cyclohexadiene‐1,4‐diylidenedimalonitrile) to obtain electronic conductivities around 10−6 S · cm−1 at 25°C. The mixed (electronic and ionic) conductivities are intermediate between the ionic and electronic conductivities. Higher electronic conductivities (≈ 10−5 S · cm−1 at 30°C) are obtained for the polycation TCNQ−/TCNQ0 complexes.
Synthesis and cation‐sensitive fluorescence of polyelectrolytes bearing crown ether side groups
Authors: Shirai Masamitsu , Ishimaru Shinichi , Tsunooka Masahiro 
Published: April 2003

AbstractPolyelectrolytes bearing crowned acetophenone moieties were prepared by radical copolymerization of 4′‐acryloylbenzo‐18‐crown‐6System. name of benzo‐18‐crown‐6: 1,2‐benzo‐1,4,7,10,13,16‐hexaoxa‐2‐octadecene.
and methacrylic acid or lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonate. On excitation with 330 nm light the polymers showed fluorescence at 410 nm in a mixed solvent of methanol and water (1:9 v/v) at 30°C. When cations were added, the fluorescence intensity of the polymers decreased in the orders Li+ > Na+ > Cs+ > Rb+ > K + for alkali metal cations, Ca2+ > Sr2+ > Ba2+ for alkaline earth metal cations and C2H5NH2 > CH3(CH2)3NH2 > C6H5CH2NH2 for alkylamine hydrochlorides used. The concentration effect for cations in the neighborhood of the polymer‐bound crown ether groups by electrostatic and/or hydrophobic binding induced significant complex formation between cations and crown ethers in aqueous solutions, resulting in a decrease of the fluorescence intensity.
Structure and mechanical properties of films of rigid‐rod polymers having flexible side chains
Authors: Schrauwen Cornelius , Pakula Tadeusz , Wegner Gerhard 
Published: April 2003

AbstractA series of rigid‐rod polyesters with flexible alkoxy side chains of different length has been studied in order to determine the structure and properties of the polymers in various states (solid state, mesophase, melt). Various supermolecular structures can be obtained depending on the length of the side chains and on the preparation conditions of the samples. The relaxation behavior of the polymers has been investigated by dynamic mechanical measurements. Complex relaxation spectra have been observed, and types of molecular motions and structural rearrangements have been assigned to the observed mechanical relaxation transitions. The rheological behavior was studied in the mesophase and in the melt. In some polymers typical liquid‐crystalline properties have been observed, as for example the flow‐thinning effect. Large deformation of polymer films as well as the structure and mechanical strength of oriented samples have also been studied.
Benzoxazole‐2‐thiol/dibenzoyl peroxide combination as photoinitiator for methyl methacrylate polymerization
Authors: Sengupta Pranab K. , Ray Gour M. Singha 
Published: April 2003

AbstractBenzoxazole‐2‐thiol (1)/dibenzoyl peroxide (Bz2O2) was used as photoinitiator for the polymerization of methyl methacrylate (MMA) in bulk and in solution. The study of initiator decomposition was conducted spectrophotometrically. Kinetic studies of the photopolymerization indicated the formation of a complex between 1 and Bz2O2 in the stoichiometric ratio 2:1. The initiation is believed to occur via in situ formation of bis(benzoxazol‐2‐yl) disulfide in the presence of light.
Thermal degradation of polybutadiene, 2. Overall thermal behaviour of polymers with different microstructures
Authors: Luda Maria Paola , Guaita Marino , Chiantore Oscar 
Published: April 2003

AbstractThe thermal decomposition at volatilization temperatures of polybutadiene samples with different initial microstructures was investigated i. vac. and under nitrogen atmosphere by thermogravimetry, differential scanning calorimetry, thermal volatilization analysis and infrared spectroscopy. The decomposition of cis‐1,4‐, trans‐1,4‐ and random polybutadienes occurs in two stages, whereas only one stage is shown by 1,2‐polybutadiene. Chemical changes and amounts of weight loss in the first degradation stage are dependent on the sample heating rates. The volatile degradation products were collected, fractionated and compared for the different polymers.
MgCl2‐supported Ziegler‐Natta catalysts: Synthesis and X‐ray diffraction characterization of some MgCl2‐Lewis base adducts
Authors: Noto Vito Di , Marigo Antonio , Viviani Maria , Marega Carla , Bresadola Silvano , Zannetti Roberto 
Published: April 2003

AbstractSome adducts of MgCl2 and Lewis bases (or donors) B were examined, having a composition MgCl2 · 2B, where B = Ethyl (Et) formate, Et acetate, Et propionate, Et benzoate, Et crotonate, acetone, 2‐butanone and EtOH. The crystallographic investigation of these adducts, carried out on polycrystalline powders and some single crystals, shows some remarkable structural analogies for all examined donors. In particular, the X‐ray diffraction patterns of the adducts indicate the total absence of the close‐packing of chlorine which characterizes α‐MgCl2 and the presence of covalent Cl‐Mg‐Cl chains. The obtained data are correlated with the preparation of active supports for Ziegler‐Natta olefin polymerization: after total elimination of B, a disordered structure of MgCl2 is obtained, which is coincident with the reported one for the mechanically activated (by ball‐milling) MgCl2 and previously described both in the scientific and in the patent literature.
Highly oxygen‐permeable copoly(methacrylate/siloxane)s with perfluoroalkyl ester groups
Authors: Koßmehl Gerhard , Fluthwedel Andrea , Schäfer Horst 
Published: April 2003

AbstractBasic materials for contact lenses were obtained by radical copolymerization of linear α,ω‐bis(methacryloyloxy)‐terminated oligo‐ and poly(dimethylsiloxane)s, methyl methacrylate and 2,2,3,3,4,4,4‐heptafuorobutyl methacrylate. Oxygen permeabilities, contact angles and ball indentation hardness were determined.
Effect of the internal/external donor pair in high‐yield catalysts for propylene polymerization, 2. Polymerization results
Authors: Barbè Pier Camillo , Noristi Luciano , Baruzzi Giovanni 
Published: April 2003

AbstractThe behaviour in propylene polymerization of catalysts containing ethyl benzoate/methyl p‐toluate (EB/MPT) or dibutyl phthalate/triethoxy(phenyl)silane (DBP/EPS) as internal/external donor pairs was investigated. Comparing catalyst composition with performance, it appears that no qualitative difference exists in the role of MPT and EPS, both acting as poisons of atactic sites and activators of isotactic sites. A higher efficiency of EPS is evident. On the contrary, a difference can be found between the internal donors EB and DBP/DBP seems not directly involved in the formation of isotactic centers as EB. These results, though obtained under conditions leading to much lower activities than usual for the catalysts considered, can be assumed to describe the general behaviour of the donor pairs investigated when the polymerization is carried out in the absence of hydrogen.
Studies of the free‐radical reaction kinetics and of the influence of lewis acids on the copolymerization of acrylonitrile with furan compounds
Authors: Chau Chun‐Wah , Fawcett Allan H. , Mulemwa Jane N. , Poon Lai Wo , Surgenor Avril , Tan Chu‐Eng 
Published: April 2003

AbstractWe found that furan and alkyl‐substituted furans function as slowly reacting monomers rather than retarders or inhibitors in free‐radical copolymerization reactions with acrylonitrile. The effect of the presence of Lewis acids was examined: some cause an ionic reaction of the furan ring, one (SO2) acts as an inhibitor, and others enhance the entry of the furan into the copolymer, increase the yield and molecular weight, and for 2‐methylfuran cause a new type of furan residue to form by promoting a hydrogen abstraction reaction.
Synthesis of poly(vinyl ether)s with perfluoroalkyl pendant groups
Authors: Höpken Jens , Möller Martin , Lee Myongsoo , Percec Virgil 
Published: April 2003

Abstract2‐Perfluoro(alkyl)ethyl vinyl ethers, F(CF2)nCH2CH2OCHCH2, (n = 6 or 8), were synthesized and polymerized by means of cationic initiators (HI/ZnI2 and CF3SO3H/(CH3)2S). The perfluorohexyl‐substituted poly(vinyl ether) is completely amorphous. The polymer with perfluorooctyl segments shows side chain crystallization with a disordering transition. For the corresponding perfluorooctyl monomer a liquid‐crystalline phase was observed before melting. Copolymerization experiments of the flurocarbon‐segmented monomers with a vinyl ether containing a cyanobiphenyl group in the side chain did not give homogeneous copolymers. This is attributed to the slower rate of polymerization of the fluorinated vinyl ethers as compared with the liquid‐crystalline comonomer.
Oligomerization of oxiranes in the presence of phosphorus acids, 2. Kinetics of addition of ethylene oxide to phosphoric and phosphorous acid
Authors: Biela Tadeusz , Szymanski Ryszard , Kubisa Przemyslaw 
Published: April 2003

AbstractKinetics of addition of ethylene oxide to the POH groups in phosphorous (H3PO3) and phosphoric acid (H3PO4) were studied. The reaction is catalysed by the POH groups themselves, presumably by formation of hydrogen‐bonded complexes with ethylene oxide. The values of apparent rate constants of reactions involving subsequent POH groups were determined. The apparent reactivity of POH increases with increasing number of OCH2CH2OH substituents present in the reacting molecule. This has been attributed to the formation of intramolecular hydrogen bonds influencing the reactivity of the POH groups. Mechanistic implications and the distribution of products are discussed in connection with the observed kinetic dependences.
The effect of chain transfer agent on the entry of free radicals in emulsion polymerization
Authors: Maxwell Ian A. , Morrison Bradley R. , Napper Donald H. , Gilbert Robert G. 
Published: April 2003

AbstractThe model of Maxwell et al. (Macromolecules 24, 1629 (1991)) for initiator efficiencies in emulsion polymerization has been extended to take into account the effect of added chain transfer agent (CTA). The model supposes that the rate‐determining step for radical entry into latex particles is aqueous‐phase propagation of the primary free radicals to a critical chain length z required for entry (forming species such as .MzSO, where M is a monomer entity and peroxodisulfate S2O is the initiator). The effect of CTA on the entry rate is assumed to occur by facilitating the production of aqueous‐phase free‐radical species (CTA.) by transfer between species such as .MzSO (where n < z) and CTA in the aqueous phase. The CTA. will be formed at a reasonable rate provided the CTA is not too water‐insoluble (e.g. C12H25SH); it should also be capable of entering the latex particles rapidly because of its relative insolubility. If the monomer‐derived .MnSO tend to suffer aqueous‐phase termination rather than entry, the overall rate of entry (and hence initiator efficiency) will be increased. This can explain the accelerating effect of intermediate molecular weight CTA's on emulsion polymerization of monomers such as butadiene, where z is large and hence initiator efficiency is very low in the absence of CTA, because most .MnSO undergo termination rather than entry into the latex particles.
Copolymerization of ethylene and propene with soluble TiCl3 catalyst systems
Authors: Makino Kenya , Tsuda Kazuichi , Takaki Mikio 
Published: April 2003

AbstractFor random copolymerization of ethylene and propene, the catalytic activity was studied of various catalyst systems consisting of TiCl3 prepared by reduction of TiCl4 with hydrogen. The extent of reduction of TiCl4 markedly affects the activity of the catalyst. Furthermore, the combination of solvent and donor affects the activity, and 1,2‐dichloroethane and dibutyl ether (DBE) was found to be the most favourable combination. Metal halides (MXn) such as VCl4 and VOCl3 enhance the activity of the TiCl3 catalyst. Concerning the co‐catalyst, triisobutylaluminium results in the highest activity. As a whole, both the catalytic activity of these catalyst systems and the structure of the resulting copolymer are largely dependent on the solubility of the catalyst system. The copolymer obtained with a soluble TiCl3 · DBE · Al(isobutyl)3 system is highly isotactic in the PPP triad and has a lower content of inversion than a copolymer prepared with a conventional VOCl3 catalyst system. Moreover, the copolymer obtained with the above TiCl3 catalyst has superior physical properties, especially tensile properties, in comparison with the copolymer obtained with the conventional VOCl3.
Copolymers prepared on the basis of isopropenyl derivatives of o‐carborane
Authors: Teplyakov Michail M. , Khotina Irina A. , Sakharova Antonina A. , Mel'nik Olga A. , Papkov Vladimir S. , Kvachev Jurie P. 
Published: April 2003

AbstractNew mono‐ and bifunctional isopropenyl derivatives of o‐carborane were synthesized according to the Witting reaction, from the corresponding acetyl derivatives and methylenetriphenylphosphorane. The radical copolymerization with methyl methacrylate was investigated and thermal and thermomechanical characteristics of the obtained copolymers were studied. In copolymers prepared on the basis of a monofunctional carborane‐containing monomer, the increase of glass transition temperature takes practically a linear course with increasing boron content. In crosslinked copolymers the presence of o‐carborane fragments leads to the widening of the glass transition temperature range, predominantly at low temperatures, irrespective of the type of bifunctional monomer used.
Solvent effects on free‐radical polymerization, 3. Solvent effect on polymerization rate of methyl methacrylate and N‐vinyl‐2‐pyrrolidone
Authors: Czerwinski Wojciech K. 
Published: April 2003

AbstractThe homopolymerizations of methyl methacrylate (MMA) in N‐methyl‐2‐pyrrolidone (NMP) and of N‐vinyl‐2‐pyrrolidone (NVP) in methyl isobutyrate (MiB) were investigated at 60°C using AIBN as initiator. Reaction rate and dynamic viscosity of the medium were determined as function of monomer dilution. It follows from the estimated monomer exponent n that MMA reacts in NMP faster (n = 0,739) and NVP in MiB slower (n = 1,495) in comparison with reaction rates obtained from the direct proportionality of monomer concentration. The observed deviation was quantitatively separated in partial deviations caused by chain initiation, propagation and termination. It was found that the viscosity effect on chain termination plays a dominant role in the global solvent effect. Chain propagation is influenced by electron donor‐acceptor interactions between monomers and solvent.
Influence of thionoesters on the degree of polymerization of styrene, methyl acrylate, methyl methacrylate and vinyl acetate
Authors: Meijs Gordon F. , Rizzardo Ezio , Le Tam P. T. , Chen Yi‐Chi 
Published: April 2003

AbstractThe aromatic thionoester 3 (benzyl thionobenzoate) was an effective chain transfer agent in polymerizations of styrene (Cx = 1,0) and methyl acrylate (Cx = 1,2) at 60°C. This activity was close to the ideal for obtaining narrow molecular‐weight distributions in batch polymerizations. The thionoester 3 showed no activity in polymerizations of methyl methacrylate, but was too reactive to be useful in vinyl acetate polymerizations. Ring‐substituted thionoesters 9‐11 and 14 and 1H NMR spectroscopy of the resulting polymers were used to establish the type and quantity of end‐groups. The thionoester 12 was used to produce low‐molecular‐weight polystyrene that was terminated at one end with a hydroxy group and at the other end by a thioloester moiety.
Polymerization of 1‐alkynes initiated by transition metal carbene complexes, 3. Kinetics and mechanism of the propagation reaction
Authors: Fontanille Michel , Lucas Christine , Soum Alain 
Published: April 2003

AbstractA comprehensive study of the 1‐heptyne polymerization initiated by a carbene complex of tungsten was carried out. Kinetic orders, apparent rate constants and thermodynamic parameters of the propagation step were determined. The structure of the organic products appearing simultaneously with the polymer during the reaction was identified by NMR and mass spectrometry. According to the experimental data, a mechanism of the propagation reaction is proposed: the propagating species derive from an initial active carbenic complex formed consequently by the insertion of the first monomer molecule into the [CW] bond of the initiator. Then, these active centres give, through a steady‐state process, active high‐polymeric chains. In competition with the normal insertion of the monomer molecules, termination and transfer reactions occur, including or not the monomer and/or the polymeric chain.
Potassium ion‐based polyurethane anionomers: effects of emulsification on structure and physical properties
Authors: Chen Show‐An , Hsu Jen‐Sung 
Published: April 2003

AbstractA polyurethane was prepared using poly(oxytetramethylene) as soft segments, 4,4′‐methylenedi(phenyl isocyanate) as diisocyanate and 2,2‐bis(hydroxymethyl)propionic acid as chain extender, and then ionized with potassium hydroxide to yield the potassium ion‐based PU anionomer. The resulting PU anionomer solution in ethyl methyl ketone was emulsified by continuous addition of water. In the unionized film, soft segment crystallites are not present. Ionization creates soft segment crystallites and produces increased cohesion in the hard domains, which leads to an increase in both tensile strength and elongation at break. Emulsification of the PU ionomer solution leads to slightly increased phase separation. During the emulsification, conductivity and viscosity variations show that water is first adsorbed on the surface of the hard‐segment microionic lattices and then enters into the disordered hard domains. The morphology of the unionized film shows that the hard domains are dispersed in the soft domains and tha the size of hard domains increases greatly after the ionization. After dispersion, the hard segments originally distributed in the dispersed phase undergo phase inversion and adopt a morphology of interwoven soft and hard domains. Compared with other PU anionomers, the present system is branched rather than linear, as reflected in the good mechanical properties of the present system.
Crystallization kinetics of β‐phase poly(propylene)
Authors: Shi Guan‐yi , Zhang Xiao‐dong , Qiu Zhi‐xue 
Published: April 2003

AbstractCrystal growth rates of spherulites of β‐phase poly(propylene)s and of an ethylene/propene block copolymer, crystallized from the melt, have been investigated in the temperature range of 122 to 146°C. On the basis of the regime theory, a transition between regime II and III is found at ΔT ≈ 37–43,5 K. The nucleation constant for β‐phase poly(propylene)based on the current theory of crystal growth was determined, and the fold surface free energy of β‐phase poly(propylene) was estimated from the nucleation constant for different samples to lie between 48,2 and 55,2 erg/cm2 (1 erg = 10−7 J).
Synthesis of mainly linear poly(dichlorophenylene oxide)s by thermal polymerization in solution
Authors: Şanlt Oya , Kisakürek Duygu 
Published: April 2003

AbstractThermal decomposition of bis(4‐bromo‐2,6‐dichlorophenoxo)‐(N,N,N',N'‐tetramethylethy‐lenediamiene)copper(II) complex in toluene, bis(4‐bromo‐2,6‐dichlorophenoxo)(N,N‐dimethyl‐formamide)copper(II) complex in N,N‐dimethylformamide and bis(4‐bromo‐2,6‐dichlorophenoxo)(dimethyl sulfoxide)copper(II) complex in dimethyl sulfoxide was achieved at 70°C. 4‐Bromo‐2,6‐dichlorophenol derivatives prefer 1,4‐addition to 1,2‐addition, leading to highly linear polymers irrespective of the substituted ligands. The complexes were characterized by IR spectroscopy and C, H, N elemental analysis. The characterization of the synthesized polymers were achieved by 1H NMR, 13C NMR and IR spectroscopy. The highest polymer yield was obtained from the decomposition of bis(4‐bromo‐2,6‐dichlorophenoxo)(N,N,N',N'‐tetramethyl‐ethylenediamine)copper(II) complex.
Analysis of the linear methods of determining copolymerization reactivity ratios, 13. A critical application of penultimate model (r2 = 0) to radical copolymerization data of styrene
Authors: Kelen Tibor , Tüdős Ferenc , Turcsanyi Béla , Braun Dietrich , Czerwinski Wojciech K. 
Published: April 2003

AbstractIn an until now widest study of the penultimate effect the reactivity ratios of 66 published styrene copolymerization systems showing a non‐classical behaviour have been reviewed. For the alternating systems a simplified two‐parameter penultimate model with r2 = r′ = 0 was applied. The systems were classified into 2 groups: 1. alternating and 2. non‐alternating systems. 32 systems of the first group have been reevaluated. r‐Values, together with their 95% confidence limits have been calculated. The confidence parameter δ′ and the “efficiency factor” of planning Q, suitable for classification of the systems, have been applied. In this number 23 (72%) systems yielded linear Kelen‐Tüdős‐plots (13 belong to class I, 10 to class I!). 5 (16%) systems were assigned to class II (non‐adequacy of the penultimate model possible) and 4 (12%) to class III, where the experimental data are inconsistent and the r‐values meaningless.
Physically interpenetrating networks in polyurethane ionomers/poly(vinyl alcohol) blends
Authors: Hsu Jen‐Sung , Su Fu‐Hu , Chen Show‐An 
Published: April 2003

AbstractThree series of blends of polyurethane ionomers (PUI) with poly(vinyl alcohol) (PVA) were prepared by mixing aqueous PUI emulsions with aqueous PVA solutions and then allowing them to dry. The characterization of the blends of various compositions was carried out using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry and tensile‐elongation testing. It was found that poly(ether‐urethane) cationomer (Cat‐Et)/PVA‐1 and poly(ether‐urethane) anionomer (An‐Et)/PVA‐2 blends exhibit a positive synergistic effect with respect to the tensile strength and that the amorphous phase of PVA is at least partially compatible with both the disordered hard domains and the soft domains of the ionomers. For the former blends, this behaviour is due to the formation of hydrogen bonding with the glycolate anions and ether groups, and for the latter blends to the formation of hydrogen bonds with the ether groups. For poly(ester‐urethane) cationomer (Cat‐Es)/PVA‐3 blends, there is no hydrogen bonding between these two components and no synergistic effect in the tensile strength after blending. Physically interpenetrating polymer networks (IPNs) are expected to occur in the former two blends, but not in the latter one.