bluuebunny/crossref_metadata_2025_split huggingface dataset:
New poly(bismaleimide‐diamine)s containing crown‐ether groups in the main chain
Authors: Kurmanaliev Musrepbek , Ergozhin Edil E. , Izteleuova Indira K. 
Published: April 2003

AbstractA series of new poly(bismaleimide‐diamine)s (3a–c) with crown‐ether groups in the main chain were synthesized from bismaleimides (1a–c) and a diamino‐functional dibenzo‐18‐crown‐6 (2). The polymerization occurred in solution through the addition of the NH2 groups of 2 to the CC double bonds of the maleimide rings of 1. The optimum polymerization conditions were established. The polymers 3 were obtained in good yields and fairly high molecular weights (ηred = 0,15–0,35 dL/g). The polymeric crown eithers show high capacity for the binding of alkali metal ions and may be used as selective sorbents.
Biodegradation of poly(D(–)‐3‐hydroxybutyrate)/atactic poly(epichlorohydrin) blends by aureobacterium saperdae
Authors: Sadocco Patrizia , Bulli Chiara , Elegir Graziano , Seves Alberto , Martuscelli Ezio 
Published: April 2003

AbstractThe biodegradability of solution‐cast films of poly(D(–)‐3‐hydroxybutyrate) (PHB) blended with the melt‐compatible component atactic poly(epichlorohydrin) (aPECH) was investigated. A bacterium which produced extracellular enzymes that degraded PHB even when blended with aPECH was isolated, and tentatively designated as Aureobacterium saperdae. The growth rate of A. saperdae decreased with increasing aPECH content in the blend, up to films containing 60 wt.‐% aPECH, at which composition growth was completely inhibited. The decrease in the bacterial growth rate could be due to the dilution of PHB molecules on the blend film surface caused by the presence of aPECH molecules. At the stationary phase of bacterial growth the percentage of weight loss of blend films decreased with increasing aPECH fraction, which was probably due to the lower accessibility of PHB when blended with aPECH. During the bacterial growth only PHB was metabolized, whereas neither degradation nor abiotic release of aPECH was detected for blend films.
Relation between phase behaviour and morphology in polyethylene/diphenyl ether systems
Authors: Aerts Luc , Kunz Martin , Berghmans Hugo , Koningsveld Ronald 
Published: April 2003

AbstractThe phase behaviour and the related morphology of the system high‐density polyethylene/diphenyl ether was investigated. A liquid‐liquid demixing precedes the crystallization in solutions with polymer weight fractions lower than 0,30. A three‐phase equilibrium is installed, in which two liquid phases with different polymer concentrations and a crystalline phase coexist. This does not lead to an invariant situation, as would be predicted from the phase rule for a strictly binary system. The crystallization and melting temperature decrease in this concentration region with increasing polymer concentration. Transmission electron microscopy observations were carried out on samples with a polymer concentration in the demixing region. A morphology, characteristic of a liquid‐liquid demixing, preceding crystallization, is observed. Globular particles with a variety of surface structures and internal organization are obtained at very low polymer concentration. Solutions with a polymer weight fraction higher than 0,10 are transformed into porous, crystalline structures. An important shrinkage of the concentrated domains takes place. It results in a pronounced solvent synersis. This change in the physical aspect of the samples is ascribed to the nature of the three‐phase equilibrium.
Radical polymerization of vinyl monomers by captodative substituted dimers
Authors: Tanaka Hitoshi , Teraoka Yasunobu , Sato Tsuneyuki , Ota Tadatoshi 
Published: April 2003

AbstractPolymerization of vinyl monomers such as styrene, methyl methacrylate, and vinyl acetate was carried out in the presence of the captodative substituted dimers 1–6 at 50 to 110°C. It was found that the dimer initiates the radical polymerization of these monomers, even of vinyl acetate. The initiation ability of the dimers depends on the nature of both captive and dative groups as well as the substituent at a remote position. The kinetic study suggests that in the polymerization initiated by the dimers primary‐radical termination and chain transfer play a minor role.
Block copolymers with poly(oxy‐1,4‐phenylene) and liquidcrystalline polyester segments
Authors: Heyde Gabriele , Heitz Walter , Karbach Alexander , Wehramann Rolf 
Published: April 2003

AbstractBlock copolymers were synthesized composed of an isotropic, crystallizable poly(oxy‐1,4‐phenylene) block and a thermotropic liquid‐crystalline (LC) polyester block. Crystalline as well as amorphous LC polyesters were used, derived from substituted poly(1,4‐phenylene terephthalate). The block of poly(oxy‐1,4‐phenylene) was introduced via telechelic 1. 1 was prepared with a functionality of 2 in a Cu‐catalyzed reaction of 4‐bromophenolate 4 with 4,4′‐isopropylidenediphenol (bisphenol A). The molecular weight of the telechelic is given by the ratio 4/bisphenol A. The increase in molecular weight during formation of the block copolymer is shown by viscosity and gel‐permeation chromatography measurements. The maximum weight loss of the block copolymer as obtained by thermogravimetry is in the range of 450–500°C. Both segments in the block copolymers have a strong influence on their mutual crystallization behaviour. Short segments of poly(oxy‐1,4‐phenylene) suppress the crystallization of both blocks. When using longer segments of poly(oxy‐1,4‐phenylene) the melting endotherms of both blocks are observed, but the degree of crystallinity is lower than that of the homopolymers. The fracture behaviour of the liquid‐crystalline polyester 2a is changed by modification with 20 wt.‐% of poly(oxy‐1,4‐phenylene) and the shear‐banded texture is lost.
Photochemical behaviour of α‐thiocyanatoketones in a polymer matrix and of thiocyanatoketones groups covalently bound to polystyrene
Authors: Kern Wolfgang , Hummel Klaus , Koller Dagmar , Sadaghiani Nassim 
Published: April 2003

AbstractThe laser‐induced photoisomerization of various α‐thiocyanatoketones in a polymer matrix (polystyrene, cis‐1,4‐polybutadiene, butadiene‐styrene copolymer) was studied by means of FT‐IR spectroscopy. Phenacyl thiocyanate was converted to phenacyl isothiocyanate under UV irradiation. The degree of isomerization increased with the styrene content of the matrix polymer. Aromatic sensitizers such as chrysene and anthracene enhanced the isomerization reaction, but also led to the decomposition of already formed isothiocyanate. After comparison of the photoreactivity of different α‐thiocyanatoketones, a linear correlation was established between the amount of isothiocyanate formed after a certain pulse number and the absorption coefficient at the laser wavelength. Polystyrene containing thiocyanatoacetyl groups was prepared via reaction with acetyl chloride, subsequent bromination at the acetyl group and reaction with potassium thiocyanate. The photoisomerization was similar to that of the low‐molecular‐weight α‐thiocyanatoketones. This photoisomerization increased, and the degree of crosslinking decreased, when a magnetic field of 900 mT was applied.
Pivalolactone, 2. Copolyester synthesis via interchange reactions with polypivalolactone
Authors: Tijsma Edze Jan , van der Does Leen , Bantjes Adriaan , Vulić Ivan , Buning Gerard Hidde Werumeus 
Published: April 2003

AbstractThe synthesis of copolyesters via interchange reactions of polypivalolactone (PPVL) with several compounds was studied. The synthetical procedures are two‐stage melt processes: in the first stage ester bonds in the polymer chain are cleaved and new groups are incorporated in the polymer chain, while in the second step condensation of the end‐groups formed occurs. For the synthesis of copolymers, three procedures were used, with tetrabutyl orthotitanate as a catalyst. PPVL was heated with equimolar mixtures of bisphenol‐A diacetate (BPAac) and terephthalic acid (TA), but no copolymers were formed; instead, polycondensation of BPAac with TA occurred, leaving the PPVL unaffected. From PPVL and mixtures of BPAac and dimethyl terephthalate (DMT) polymers were obtained which contained a significant amount of copolymeric sequences. However, most of the polymeric chains consisted of PPVL and poly(bisphenol‐A terephthalate) blocks. Random copolymers with thermal stability were obtained after heating PPVL with bisphenol‐A polycarbonate and DMT. The latter process was studied in detail by IR, DSC, and solubility and selective degradation tests. Based on the results of these studies, the reactions occurring during the three procedures were discussed.
Synthesis of poly(vinyl alcohol)‐graft‐polystyrene
Authors: Tezuka Yasuyuki , Araki Akitoshi 
Published: April 2003

AbstractThe reaction of living polystyrene, prepared with butyllithium as an initiator in a tetrahydrofuran/benzene (vol. ratio 1/1 or 2/1) solution at −30°C or −50°C, with chlorodimethylvinylsilane was carried out to prepare polystyrene with narrow molecular‐weight distribution and with a vinylsilane end group (1). The radical copolymerization of vinyl acetate with 1 in ethyl acetate solution yields poly(vinyl acetate)‐graft‐polystyrene (2) of controlled graft segement length. The subsequent saponification of 2 with NaOH in methanol provides poly(vinyl alcohol)‐graft‐polystyrene (3).
Conformational change on polymer chains of partially formalized poly(vinyl alcohol)‐iodine color complex studied by using synchrotron radiation small‐angle X‐ray solution scattering
Authors: Hirai Mitsuhiro , Hirai Toshihiro , Ueki Tatsuo 
Published: April 2003

AbstractThe structure of a partially formalized poly(vinyl alcohol) (PFV)‐iodine color complex was investigated at a series of iodine concentrations by using small‐angle X‐ray scattering and resonance Raman Methods. Scattering experiments show that the increase of iodine concentration induces a structural change of the PFV polymer chains from an expanded coil to a Gaussian coil. On the process of complexation of PFV with iodine, the number of iodine atoms occluded by a PFV molecule with degree of polymerization (D.P.) 560 was evaluated to be less than 25 (0,044/D.P.) in the amorphous state or 31 (0,056/D.P.) in the crystal state, a value being much smaller than those deduced for amylose and cyclodextrin. The resonance Raman Spectrum of the PFV‐iodine complex clearly indicates the presence of polyiodine chains in the polymers. Therefore, it can be assumed that the hetrogeneous occlusion of iodine in polymer chains occurs cooperatively, and that the formation of polyiodine chains changes the local structure of the polymer chains breaking the long‐range interactions between the polymer segments for exhibiting an excluded volume effect.
Synthesis and initiation/transfer properties of carbamoyl disulfides
Authors: Popielarz Roman , Clouet Gilbert 
Published: April 2003

AbstractThree model tetraalkylcarbamoyl disulfides were prepared and their initiation/transfer capabilities tested. The compounds studied were: bis(1‐piperidinecarbonyl) disulfide (1), bis(4‐(2‐hydroxyethyl)piperazine‐1‐carbonyl) disulfide (2), bis[N‐ethyl‐N‐(2‐(trimethylsiloxyethyl)‐carbamoyl)] disulfide (3). It was found that, in contrast to tetraalkylthiruam disulfides, the carbamoyl disulfides were not able to initiate free radical polymerization of methyl methacrylate (MMA) and styrene (ST), even at the highest temperatures applicable to these monomers. Apparently, the central S—S bond in carbamoyl disulfides is much stronger than the corresponding S—S bond in thiuram disulfides. Moreover, the carbamoyl disulfides are rather poor transfer agents. The transfer constants were estimated to be 2,5 10−3, 18.10−3 and 2,8. 10−3 for 1,2 and 3 in thermal polymerization of MMA at 110, 110 and 100°C, respectively, and 2,1. 10−3 for 3 in polymerization of MMA initiated with AIBN at 70°C. Chemistry aspects of synthesis and stability of hydroxy‐functionalized carbamoyl disulfides are discussed.
Ring‐opening metathesis polymerization of 7‐methylnorbornadiene
Authors: Hamilton James G. , Rooney John J. , Snowden David G. 
Published: April 2003

AbstractRing‐opened metathesis polymers of 7‐methylnorbornadiene (1) have been synthesized with cis main‐chain double bond contents ranging from 20 to 97% using several initiators; their microstructures have been examined in detail using 13C NMR spectroscopy. The result show that polymerization from the anti‐exo orientation is greatly favoured over the syn‐exo mode. A nonbonded repulsion energy of 6–8 kJ · mol−1 between the syn‐7‐methyl group and the double bond is estimated. The microstructural features also resemble those for polymers of the anti‐ and syn‐7‐methylnorbornenes, in contrast to poly(norbornadiene) itself and to poly(norbornene), in that the splitting of a given resonance due to tacticity effects is of the same order as splittings due to neighbouring double bonds. Cis double bond contents and tacticities using different catalysts agree well with those expected from previous work with norbornadiene and several methyl‐substituted norbornenes, respectively, as monomers. The previous surprising observation that there is significantly less or no discrimination between the syn‐ and anti‐orientations in polymerizing 7‐tert‐butoxy‐ and 7‐acetoxynorbornadiene is discussed and is attributed to a pseudo [3 + 2] transition state replacing the normal one for [2 + 2] metallacyclobutanation. In the [3 + 2] mode a lone pair of electrons on the oxygen acts in conjunction with the π pairs of the CC and [Mt]C moieties. The net effect is to lower the energy barriers for the [2 + 2] cycloaddition and the reverse step. The same explanation, rather than chelation, is also believed to be correct for the beneficial effect on the metathesis polymerization of the 7‐oxa group in several substituted 7‐oxanorbornenes and 7‐oxanorbornadienes when compared to the corresponding 7‐methylene monomers.
Network formation by cyclotrimerization
Authors: Stutz Herbert , Simak Petr 
Published: April 2003

AbstractA theoretical approach to network formation by cyclotrimerization is presented which allows a full description of all network characteristics. Its application to trimerization of bisphenol‐A dicyanateSystematic IUPAC name: 4,4′‐isopropylidenebis(1,4‐phenylene) dicyanate.
shows full agreement between theoretical predictions and experimental data. Cyanate analysis was accomplished by means of Fourier transform infrared spectroscopy and a photometric method. The experimental gel point (at conversion 50,4%) was in close agreement with theoretical predictions.
Photochemical behaviour of poly(organophosphazene)s, 12. Photo‐oxidation of catena‐poly[bis(4‐benzylphenoxy)‐λ5‐phosphazene] at short and long wavelengths under accelerated conditions
Authors: Scoponi Macro , Pradella Fiorella , Carassiti Vittorio , Gleria Mario , Minto Francesco 
Published: April 2003

AbstractIn this paper the mechanism of the thermo‐and photo‐oxidation of catena‐ poly[bis(4‐benzylphenoxy)‐λ5‐phosphazene] films at short and long wavelengths has been followed under accelerated conditions using FTIR and UV‐visible spectroscopic techniques. The decrease of the band at 1453 cm−1 and the simultaneous appearance of new bands at 3400 and 3481 cm−1, due to free and bonded hydroperoxides, show that the primary hydroperoxidation in this polymer occurs at CH2 groups belonging to benzylic moietics. According to our previous paper, the bands observed in the carbonyl region at 1657, 1704 and 1725 cm−1 during photo‐oxidation have been assigned to the formation of benzophenone, benzaldehyde and benzoic acids (dimmers), respectively. The formation rate of benzophenone groups increases during irradiation at long wavelengths (λ > 400 nm). Under thermo‐oxidative condition (90°C), the benzophenone groups are the main oxidation products derived from hydroperoxide decomposition. In addition, the photooxidation of a film pre‐thermo‐oxidized for 500 h shows clearly that the benzophenone groups can generate aldehydes, benzoic acids and peracids. Crosslinking takes place in high yields by hydrogen abstraction occurring at both benzylic and secondary alcohol units. The regeneration of benzophenone groups has been evidenced during the photo‐oxidation.
Synthesis and properties of polyimides derived from 4,4′‐(2,7‐naphthylenedioxy)dianiline and aromatic tetracarboxylic dianhydrides
Authors: Yang Chin‐Ping , Chen Wen‐Tung 
Published: April 2003

AbstractNovel polyimides containing 2,7‐diphenoxynaphthalene moieties were prepared from 4,4′‐(2,7‐naphthylenedioxy)dianiline (DAPON) and various aromatic tetracarboxylic dianhydrides via a two‐stage procedure that includes ring‐opening polyaddition in a polar solvent such as N,N‐dimethylacetamide to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s exhibit inherent viscosities between 0,63 and 1,94 dL/g depending on the tetracarboxylic dianhydrides used. Except for the polyimide 4d, obtained from 3,4 : 3′,4′‐benzophenonetetracarboxylic dianhydride (2d), all polymides from yellow, flexible, and tough films upon casting from the poly(amic acid) solutions. Polyimide 4ederived from 4,4′‐sulfonyldiphthalic anhydride (2e) exhibits better solubility than the other polymides. The polyimides synthesized from and 2d are semicrystalline polymers, whereas the other polyimides are amorphous due to their X‐ray diffractograms. Tensile strength and elongation of the DAPON‐based polyimide films from 86–107 MPa and 6–25% respectively. These polyimides have glass transition temperature 223 and 285°C. Thermal analyses indicated that these polymers are fairly stable, and the 10% weight loss temperatures were recorded in the ranges 568–581 °C in nitrogen and 557–570°C in air.
Chemical reduction of the emeraldine base of polyaniline by reducing agents and its kinetic study
Authors: Moon Doo‐Kyung , Ezuka Masahiro , Maruyama Tsukasa , Osakada Kohtaro , Yamamoto Takakazu 
Published: April 2003

AbstractThe reduction of the emeraldine base form of polyaniline (PEM) by N,N‐diethylhydroxylamine, sodium tetrahydroborate, sodium dithionite, and hydrazine monohydrate proceeds smoothly at room temperature to give the leucoemeraldine base form of polyaniline (PLM). The reduction of PEM to PLM with these reducing agents obeys a pseudo‐first‐order kinetics with respect to the concentration of PEM. The pseudo‐first order rate constants, k, of the reduction with hydrazine monohydrate (5,0 · 10−1 mol · L−1), N,N‐diethylhydroxylamine (6,2 · 10−2 mol · L−1), and NaBH4 (1,13 · 10−3 mol · L−1) are 1,46 · 10−4 S−1, and 2,50 · 10−4 s−1, and 1,7 · 10−3 s−1 at 20°C, respectively. In the case of sodium dithionite, which has a higher reducing ability, the reduction proceeds very rapidly at room temperature. Plot of In(k/[reductant]) against the electrochemically measured half‐wave potential E1/2 affords a linear correlation with a slope of 20 V−1.
Structure and aggregation behavior of tamarind seed polysaccharide in aqueous solution
Authors: Lang Peter , Burchard Walther 
Published: April 2003

AbstractLight‐scattering data from tamarind seed polysaccharide (TSP) very often result in different molar masses and dimensions. This effect is due to a strong tendency to self‐association of the polysaccharide. The relation between particle masses and radii of gyration indicates worm‐like chain behaviour of TSP at fairly low particle masses. The solution properties of TSP in this regime may conveniently be described by the model of bundle‐shaped lateral aggregates of single polymer chains, whereas the aggregates seem to attain more spherical shape at higher degree of aggregation. It is shown that the relation of thermodynamic and hydrodynamic behaviour of TSP is different from that of Gaussian coils and is rather that of polymers which are known to be of high chain stiffness.
The ring‐opening metathesis polymerization of (±)‐endo‐bicyclo[2.2.1]hept‐5‐en‐2‐yl acetate; microstructure of the polymer
Authors: Ivin Kenneth J. , Lam Luk‐Mui , Rooney John J. 
Published: April 2003

AbstractThe monomer (±)‐endo‐bicyclo[2.2.1]hept‐5‐en‐2‐yl acetate (1) was polymerized by Re‐, W‐, Mo‐ and Ru‐based metathesis catalysts to yield polymers with cis double bond contents ranging from 76% to 16%. A complete assignment was made of the lines in the 13C NMR spectra. No significant head‐tail bias was observed and no splittings due to tacticity were detected.
Preparation of star‐shaped polylactide with pentaerythritol and stannous octoate
Authors: Kim Soo Hyun , Han Yang‐Kyoo , Ahn Kwang‐Duk , Kim Young Ha , Chang Taihyun 
Published: April 2003

AbstractThe ring‐opening polymerization of L‐lactide with stannous octoate was investigated in the presence of pentaerythritol. By this way it was possible to prepare higher molecular weight star‐shaped poly(L‐lactide)s compared with the linear ones obtained by stannous octoate only. The weight‐average molecular weights of linear and star poly(L‐lactide)s were measured by light scattering analysis from hexafluoro‐2‐propanol solution, and the respective Mark‐Houwink equations were derived. The second virial coefficient and the intrinsic viscosity of the star polymers were lower than those of the linear ones, which confirms the star‐shaped architecture.
Rate coefficients of the free‐radical polymerization of 1,3‐butadiene
Authors: Deibert Stefan , Bandermann Friedhelm 
Published: April 2003

AbstractRate coefficients of termination and transfer in the free‐radical polymerization of 1,3‐butadiene in chlorobenzene were determined in the temperature range 318 K < T < 333 K. On the basis of an earlier published temperature dependence of the rate coefficient of propagation, for the termination reaction the Arrhenius equation Kt = 1,13 · 1010 · exp(− 711 K/T) L · mol−1 · s−1 was obtained. For the transfer to monomer the experiments yielded the Arrhenius equation Ktr,M = 4,22 · 106 · exp(− 5140 K/T) L · mol−1 · S−1 and for the transfer to the solvent Ktr,S = 2,25 · 108 · exp(− 7050 K/T) L · mol−1 · S−1.
Rubber modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/crosslinked polystyrene semi‐interpenetrating polymer networks: morphology and impact behaviour
Authors: Penco Maurizio , Villa Anna Maria , Gobbi Cristina , Pegoraro Mario , di Silvestro Guiseppe , Speroni Franco 
Published: April 2003

AbstractRubber modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO)/crosslinked polystyrene (CPS) semi‐interpenetrating polymer networks (semi‐IPNs) was studied using polybutadiene (PB), a linear styrene‐butadiene‐styrene (SBS) triblock cocpolymer and a star‐shaped SBS multi‐block copolymer, at different composition ratios. The materials, obtained by reactive compression moulding of mixtures containing PPO, an elastomer, styrenic monomers and crosslinker (divinylbenzene), show a very high glass transition temperature (Tg), high dimensional stability and good impact properties.
Synthesis and radical polymerization of allenyl ethers with oligo(oxyethylene) moieties
Authors: Aggour Yassin A. , Tomita Ikuyoshi , Endo Takeshi 
Published: April 2003

AbstractSynthesis and radical polymerization of allenyl ethers with oligo(oxyethylene) moieties (1a–1c: CH2CCHO(CH2CH2O)mCH3, m = 3 − 1) were examined. The polymerization of 1a(m = 3) in bulk with 2,2′‐azoisobutyronitrile as initiator at 60°C gives the polymer 2a in 51% yield with 75% of the double bonds remaining in the polymer chain (estimated by 1H NMR). The polymers 2a–2c are hydrophilic, soluble in protic solvents such as water and methanol, and are subject to crosslinking upon storage in the air.