bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross polarization between 1H and 13C nuclei in isotactic poly(propylene). Effects of crystallinity and crystallographic form
Authors: Tanaka Hiroshi , Fujiwara Yasuna , Asano Tsutomu , Polizzi Stefano
Published: April 2003

13C spectra of monoclinic (α), hexagonal (β) and smectic isotactic poly(propylene) (PP) with different degrees of crystallinity were obtained by the cross polarization/magic angle spinning (CP/MAS) method. In order to estimate the effects of cross polarization, an accurately weighed poly(oxymethylene) (POM) rod was packed into a rotor together with the sample and the ratio of the peak area of PP to that of POM was measured precisely. Taking the crystallinity into consideration, the cross polarization seems to occur rather effectively in smectic PP. This result indicates that there are constrained chains in the amorphous regions of the smectic PP, which contribute effectively to the cross polarization. The ratio of the peak are of α‐and β‐PP is nearly equal, indicating that the cross polarization occurs mainly in the crystalline regions in both samples and not in the amorphous regions. The 1 H spin‐lattice relaxation time in the rotating frame decreases with decreasing crystallinity, indicating the presence of imperfect crystallites in the smectic PP.
Copolymers of 1,5‐cyclooctadiene and [2.2]paracyclophane‐1,9‐diene: metathetic preparation and structure analysis
Authors: Thorn‐Csányi Emma , Pflug Kai Patrick
Published: April 2003

Copolymers of 1,5‐cyclooctadiene (COD) and [2.2] paracyclophane‐1,9‐diene (PCPDE) were prepared by methathesis reaction using a well‐defined tungsten carbene complex as catalyst. UV/Vis and 1H NMR spectroscopy give evidence for a dissection of the opened PCPDE molecule into separate p‐phenylenevinylene units in the course of the polymerization. These units are distributed randomly in the polymer chain. This was confirmed by the metathetical preparation and spectroscopic investigation of a model substance and the comparison with spectra of compounds similar to the p‐phenylenevinylene units in the copolymer.
Preparation of poly(urethane/vinyl) block copolymers initiated by polyurethane‐type macroazo initiators
Authors: Kinoshita Hiroshi , Tanaka Nobuo , Araki Takeo , Ooka Masataka
Published: April 2003

Poly(urethane/vinyl) block copolymers (PU‐PV) were obtained in high yields by the polymerization of vinyl monomers (butyl methacrylate (BMA), ethyl acrylate (EA), and methyl methacrylate (MMA)) in the presence of polyurethane‐type macroazo initiators (PUMAI). PUMAI was prepared via addition reaction of azodialcohol, dipropylene glycol and hexamethylene diisocyanate. The PU‐PBMA's, as typical examples of PU‐PV's were purified by solvent extraction. Characterization of the purified PU‐PBMA's by 1H NMR, IR, together with extraction behavior, supported the block nature of PU‐PBMA. Film tensile strength and elongation measurements in comparison with the corresponding blend samples also supported the block nature of PU‐PV.
Effects of non‐mesogenic comonomers on the phase behaviour, the structure and the miscibility of side chain liquid‐crystalline polymers
Authors: Braun D. , Neumann H. J. , Hellmann G. P.
Published: April 2003

The phase behaviour of methacrylic side chain liquid‐crystalline (LC) copolymers, with a spacer‐decoupled mesogen in one comonomer and a methyl (MMA) or stearyla (SMA) substituent in the other comonomer, was studied. The mesogen is of the phenyl benzoate type and has a methoxy end group. The LC homopolymer (PLC) has a smectic and a nematic phase. The comonomers MMA and SMA destabilize the LC phase. This effect is compared to the destabilisation caused by end groups in oligomers of PLC. The SMA side chains crystallize so that the SMA copolymers assume a smectic‐crystalline bilayer structure. Finally, it is shown that the order of the copolymers affects their mutual miscibility.
Multicolor electrochromic behavior of polyaniline composite films combined with polythiophene and poly(3‐methylthiophene) films
Authors: Morita Mitsuyuki
Published: April 2003

The electrochromic behavior of polyaniline‐poly(sodium acrylate) composite films (CPAn‐PAcNa) combined with electrochemically synthesized polythiophene (EPT) and poly(3‐methylthiophene) (EPMeT) films was investigated in LiClO4–CH3CN aprotic non‐aqueous solution. The combination was achieved by chemical deposition of CPAn‐PAcNa on EPT and EPMeT. The combined films showed spectra overlapped with the absorption of each component polymer by electrochemical oxidation. The individual electrochromic processes of the components did not influence each other. The electrochemical stability of EPT and EPMeT improved by their combination. Each electrochromic change of the component polymers in a combined film was controllable individually to some degree by applying the potential giving rise to the specific visible absorption of each component when the combined film was prepared with an appropriate quantity of EPT and EPMeT.
Synthesis and characterization of rigid‐rod polyesters bearing 3‐hydroxypropyl and 3‐acetoxypropyl side groups
Authors: Steuer Martin , Rehahn Matthias , Ballauff Matthias
Published: April 2003

A description of the syntheses of two structurally well‐defined aromatic polyesters having polar 3‐hydroxypropyl or 3‐acetoxypropyl side groups is given. The hydroxy derivative was prepared by reacting a soluble precursor polyester bearing 2‐propenyl substituents with 9‐borabicyclo‐[3.3.1]nonane, followed by an oxidative work‐up procedure. The acetoxy‐substituted polyester was obtained treating the hydroxy polymer with acetic anhydride. The reaction conditions for these steps were studied in detail by using model compounds to minimize cleavage of the ester bonds during the conversions. The analysis of the polyesters by NMR spectroscopy and osmometry proved that under suitable conditions almost no degradation occurs during the conversions of the polyesters.
Microstructure of poly(vinyl alcohol) hydrogels investigated with differential scanning calorimetry
Authors: Cha Won‐Ill , Hyon Suong‐Hyu , Ikada Yoshito
Published: April 2003

The physical state of water in poly(vinyl alcohol) (PVA) hydrogels was studied with differential scanning calorimetry to elucidate their microstructure. PVA hydrogels were prepared after three different methods, viz. chemical crosslinking with glutaraldehyde, annealing of dried film and crystallization at low temperature. The water in PVA hydrogels could be classified into three types: free water, intermediate water and bound water. The concentration of bound water is practically not dependent on the total water content of the hydrogels when prepared by low‐temperature crystallization or annealing of the PVA film. The gel prepared by low‐temperature crystallization contained less bound water than the gel obtained by annealing of a cast film. Furthermore, the concentration of bound water increases as the degree of polymerization (DP) of PVA increases, whereas the reverse tendency was observed for the intermediate water. From these results it was concluded that the low‐temperature crystallization method results in a larger free space between the PVA microcrystallites and a larger size of microcrystallites than the annealing method. It is also likely that PVA of higher DP provides a larger amount of free PVA chains which are not involved in microcrystallites.
Conductivity relaxation of polyaniline
Authors: Lee Hsun‐Tsing , Liao Chien‐Shiun , Chen Show‐An
Published: April 2003

Measurements on polyaniline using dielectric analysis (DEA, −50°C to 240°C, 0,4 Hz to 105 Hz), differential scanning calorimetry (DSC, 30°C to 240°C) and infrared spectroscopy (IR) after heat treatment from 25°C to 300°C are carried out. After conversion of DEA results to complex electric modulus, the conductivity relaxation time distribution can be obtained, which remains unchanged for temperatures below 160°C and becomes narrower in the temperature range from 180°C to 240°C due to the occurrence of crosslinking reactions, as is confirmed by the exothermic behavior above 160°C and by the decrease of the relative intensity of quinoid absorption with respect to that of the aromatic ring. The crosslinking reaction causes a decrease in dc conductivity, a narrowing in conductivity relaxation time distribution and an increase in activation energies for conductivity and conductivity relaxation.
Terpolymerization of ethene, acrylonitrile and vinyl acetate
Authors: Buback Michael , Panten Kristen
Published: April 2003

The free‐radical terpolymerization of ethene, acrylonitrile and vinyl acetate was studied at 2000 bar in the temperature range from 170°C to 240°C in a continuously operated tubular‐type reactor. Polymerization was induced either thermally or chemically by di‐tert‐butyl peroxide as the initiator. Addition of vinyl acetate to ethene and acrylonitrile substantially enlarges the range for polymerization in the homogeneous fluid phase as compared to the binary copolymerization of ethene with acrylonitrile; a terpolymer with a high content of nitrile functional groups can be obtained from a single‐phase reaction. The six reactivity ratios of this terpolymerization, rEA, rEV, rAE, rAV, rVE and rVA are derived by applying first‐order Markov‐chain simulations. As ethene is the major component in the monomer mixtures, rEA and rEV are obtained with higher accuracy. For rEA the Arrhenius expression rEA = 2,6 · exp(−2,1 · 103 · (T/K)−1) is found (for 2000 bar). rEV = 0,9 ± 0,2 appears to be independent of temperature. The accuracy of the reactivity ratios rVE, rAV, rVA and rAE is not sufficient to detect a temperature dependence. The terpolymerization is also treated as a quasi binary copolymerization of ethene/vinyl acetate and acrylonitrile.
Chromatographic investigations of macromolecules in the critical range of liquid chromatography, 5. Characterization of block copolymers of decyl and methyl methacrylate
Authors: Pasch Harald , Augenstein Michael
Published: April 2003

Block copolymers of decyl and methyl methacrylate were analyzed by liquid chromatography at the critical point of adsorption. The molar mass and the polydispersity of the decyl methacrylate block was determined using chromatographic conditions resulting in a critical mode for poly(methyl methacrylate). In addition, using the same column system, the total molar mass and polydispersity of the block copolymers were determined, operating at chromatographic conditions insuring a size exclusion mechanism for both components.
Surface tension of poly(fluoroalkylsilsesquioxane)s
Authors: Kobayashi Hideki
Published: April 2003

Poly(3,3,3‐trifluoropropylsilsesquioxane) (Prf‐T) and poly(3,3,4,4,5,5,6,6,6‐nonafluorohexylsilsesquioxane) (Hxf‐T) were synthesized via the hydrolysis of trichloro‐3,3,3‐trifluoropropylsilane and trichloro‐3,3,4,4,5,5,6,6,6‐nonafluorohexylsilane, respectively. The related resin‐like fluorosilicone polymers containing dimethylsiloxy units were also prepared. Contact angle measurements were carried out after the polymers were crosslinked by condensation. The solid surface tensions were determined from the combined Owens‐Wendt/Young equation using water and methylene diiodide contact angles. The value obtained for Prf‐T resin (20 mN/m) is similar to the value for poly(methylsilsesquioxane) as the unfluorinated silsesquioxane analogue (21,5 mN/m). On the other hand, the Hxf‐T polymer shows a very low surface tension, 7 mN/m, lower than that of the corresponding polysiloxane with linear structure, poly[methyl‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)siloxane]. The surface tensions based on other approaches, such as the Girifalco‐Good‐Fowkes‐Young equation and the Zisman critical surface tension of wetting, were also determined.
Copolymerization of ethylene oxide and sulfur dioxide initiated by lewis bases
Authors: Florjańczyk Zbigniew , Raducha Dorota
Published: April 2003

Sulfur dioxide undergoes copolymerization with ethylene oxide in the presence of Lewis bases capable of forming onium ions (such as amines, phosphines, diethyl sulfide, dimethyl sulfoxide, N,N‐dimethylformamide) yielding poly(ethylene sulfite) bearing also a small amount of ethylene oxide monomeric units homosequencies. After 4–6 h of reaction at 50°C in bulk, the monomer conversion reaches 70–90%. The copolymer obtained is a mixture of linear and cyclic products which tend to degrade to yield ethylene sulfite. At 50°C this decomposition is very slow when unreacted SO2 is completely removed. However, it proceeds very rapidly, within a few hours, in the presence of compounds with strong electrophilic properties like BF3, H3PO4, or chlorotrimethylsilane. Studies of model reactions indicate that in the systems studied the macrocyclization results mainly from the attack of sulfite or alcoholate active species at the carbon atoms in polysulfites. Chain transfer reactions with the solvent occur also in reactions carried out in ethanol.
Monomer‐isomerization polymerization, 37. Effect of transition metal chlorides on monomer‐isomerization polymerization of 2‐butene with TiCl3/Al(C2H5)3 as catalyst
Authors: Endo Kiyoshi , Ueda Ryuichi , Otsu Takayuki
Published: April 2003

The effect of transition metal chlorides (MtClx) as isomerization catalysts was examined in the monomer‐isomerization polymerization of cis‐2‐butene with TiCl3/Al(C2H5)3 as a catalyst. The isomerization and polymerization depend on both, MtClx and MtClx/TiCl3 mole ratio. The rate of polymerization of 2‐butene with TiCl3/Al(C2H5)3/MtClx (mole ratio Al/Ti = 3,0, Mt/Ti = 1,0) as catalysts decreases in the following order: NiCl2 > CoCl2 > FeCl3 > None > MnCl2 > CrCl3. This order was found to be in a good agreement with the electronegativity of the metal atom in the chloride.
Photocrosslinking of 1,4‐polybutadiene with α‐thiocyanatoketones as photoinitiators
Authors: Kern Wolfgang , Hummel Klaus
Published: April 2003

The photocrosslinking of 1,4‐polybutadiene with various α‐thiocyanatoketones 1 as photoinitiators was examined. An excimer laser (308 nm) was used as light source, the samples were irradiated with an intensity of 6,2 mJ per pulse per cm2 under exclusion of oxygen. As initiators were used: phenacyl thiocyanate (1a), 1‐oxo‐1,2,3,4‐tetrahydro‐2‐naphthyl thiocyanate (1b), 1‐oxo‐2‐indanyl thiocyanate (1c), α‐phenylphenacyl thiocyanate (1d), 2‐naphthoylmethyl thiocyanate (1e) and 3‐phenanthrylcarbonylmethyl thiocyanate (1f). 1,4‐Polybutadiene samples that contained 20 mmol of initiator per 100 g were irradiated with 200 to 1000 pulses. 1a and 1b showed the highest crosslinking efficiency. The photochemistry of 1a in solution (2‐propanol, benzene and (Z,Z)‐1,5‐cyclooctadiene) was investigated. Analysis of the photochemical reaction products by combination of gas chromatography (GC) and mass spectrometry (MS) confirmed that the radical cleavage into benzoylmethyl and thiocyanato radicals is the first step of the reaction. Tetrafunctional crosslinks in allyl position were found in traces by means of metathesis degradation followed by GC/MS.
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

A 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

The 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

The 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

Polymerization 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

Block 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

The 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

The 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

The 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

The 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

Three 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

Ring‐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

A 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 dicyanate

Systematic 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

In 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

Novel 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

The 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

Light‐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

The 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

The 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

Rate 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

Rubber 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

Synthesis 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.
Amido‐thioether polymers containing pendant carboxylato groups: thermodynamics of protonation and copper(II) complex formation in dilute aqueous solution
Authors: Casolaro Mario , Ranucci Elisabetta , Bignotti Fabio , Ferruti Paolo
Published: April 2003

Calorimetric data are reported for the enthalpy of protonation of pendant carboxylato groups in new polymers 1a–d containing amido and thioether moieties in their main chain. These data, together with potentiometric and viscometric data, afford a complete thermodynamic description of the protonation process of the new polyacids, which are water‐soluble in a narrow range of α (degree of protonation) values. Comparison with the non‐macromolecular model 2 revealed that the thermodynamic features are attributable to polyelectrolyte effects. In contrast with model 2, all polymers studied form stable hydroxocomplex species with copper(II) ion. The hypothesized [Cu(OH)2L2]2− (where L is the monomeric unit of the polymer) stoichiometry fits the potentiometric data well when processed with the ‘SUPERFIT’ program. The trend of the corresponding stability constant (log β) values is to decrease with increasing pH over a wide range.
The post‐irradiation oxidation of poly(propylene), 1. Radical decay and oxygen absorption
Authors: Geuskens Georges , Nedelkos Grigorios
Published: April 2003

The oxidation of poly(propylene) following gamma irradiation was studied by means of electron spin resonance spectroscopy, hydroperoxide analysis and oxygen absorption measurements. Most peroxy radicals trapped after irradiation are mobile and decay within a week as a consequence of a migration process involving oxygen absorption and production of hydroperoxides. During that initial stage, the rate of oxygen absorption decreases proportionally to the peroxy radical concentration. Afterwards, the concentration of peroxy radicals becomes practically stationary and the rates of oxygen absorption and of hydroperoxide production remain constant for more than a year. That second stage of post‐irradiation oxidation of poly(propylene) is initiated by the slow decomposition of clustered hydroperoxides that proceeds even in the dark at room temperature.
Kinetics of radical polymerization, 55. The polymerization of p‐methylstyrene in solution
Authors: Gyöngyhalmi I. , Nagy A. , Földes‐Bereznich T. , Tüdős F.
Published: April 2003

Radical polymerization of p‐methylstyrene was studied in benzene solution at 50°C using AIBN as the initiator. The rate of inititation was determined at various dilutions; it shows a slight linear dependence on the composition of the polymerization mixture. The polymerization rate is directly proportional to the square root of initiator concentration; however, in contrast to the classical kinetic picture, it is not directly proportional to the monomer concentration. The experimentally measured solvent effect can be interpreted neither by the diffusion theory nor by the EDA theory, it is, however, quantitatively consistent with the theory of hot radicals. The so‐called absolute values of the rate constants of chain propagation (k̄2) and chain termination (k4) were determined by means of the rotating sector method. The value of k4 was found to be constant within the limits of experimental error, consequently the experimentally observed solvent effect is caused solely by the change in the chain propagation rate constant.
Melting behavior of hydrolyzable poly(oxyethylene)/poly(L‐lactide) copolymers
Authors: Liu Hsin‐Jiant , Hu David Shiaw‐Guang
Published: April 2003

The melting behavior of poly(oxyethylene) (PEG)/poly(L‐lactide) (PLLA) triblock copolymers with PEG contents ≦18,3 wt.‐% was studied by differential scanning calorimetry and polarizing optical microscopy. The influence of the PEG segment contents and the hydrolysis of the PEG/PLLA copolymers on the melting process was investigated. The melting temperatures of the PLLA homopolymers decrease with increasing hydrolysis time up to 600 h, and the degree of crystallinity increases from 46 to 56%. This causes the arrangement of the chains more ordered. Therefore, the entropies of fusion (ΔSm) of the PLLA homopolymers increase during the hydrolysis time up to 600 h. The melting temperatures of the PEG/PLLA copolymers decrease, while the recrystallization temperatures increase with increasing hydrolysis time up to 600 h. In addition, both the increases of PEG content and hydrolysis time of the PEG/PLLA copolymers cause a decrease of ΔSm. The PEG segments and the hydrolysis are responsible for the disordered arrangement of the chains.
Cationic polymerization of α‐pinene with aluminium‐based binary catalysts, 3. Effects of added base
Authors: Higashimura Toshinobu , Lu Jiang , Kamigaito Masami , Sawamoto Mitsuo , Deng Yun‐Xiang
Published: April 2003

In the presence of nucleophilic additives such as esters (ethyl benzoate, acetate, and chloroacetate), ethers (diethyl ether and 1,4‐dioxane), and ammonium salts (nBu4NCl), oligomers of α‐pinene with relatively high molecular weights (M̄n ≥ 1000) were obtained with the AlCl3/SbCl3 binary catalyst in toluene at 0°C ([AlCl3]0 = 42,5 mmol · L−1, Sb/Al = 0,50, [additive]0 = 10,6 mmol · L−1). The yield was 80–90 wt.‐%, and the dimer content was as low as 6 wt.‐%. Also in the polymerization at 25°C, the addition of ethyl benzoate increased the oligomer's average molecular weight (M̄n = 850) and decreased the dimer content (10 wt.‐%), in contrast to the low M̄n (350) and the high dimer content (40 wt.‐%) in the absence of the additive. The oligomers obtained in the presence of ethyl benzoate contained the repeating unit 1 which has an endo‐olefin group, at higher ratio than in the absence of the additive. Phenomenologically, the role of the additives is to retard the polymerization so as to proceed at a moderate rate even at high temperature above 0°C and thereby to suppress the dimer formation.
Molecular dynamics of new thermoplastic elastomers based on hydrogen bonding complexes: a deuteron nuclear magnetic resonance investigation
Authors: Dardin Alexander , Stadler Reimund , Boeffel Christine , Spiess Hans Wolfgang
Published: April 2003

4‐(4‐Carboxyphenyl)‐3,5‐dioxo‐1,2,4‐triazolidin‐1‐yl moieties resulting from 4‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)benzoic acid (U4A) randomly attached to 1,4‐polybutadiene form supramolecular aggregates which act as effective junction zones in new thermoplastic elastomers. Deuteron nuclear magnetic resonance (2H NMR) spectroscopy was used to investigate the molecular dynamics of the polymer backbone and the junction zones in selectively labelled samples. The spectra show motional heterogeneity along the polymer chain as well as in the supramolecular domains. Polybutadiene segments which are adjacent to these polar clusters are restricted in their mobility, even at temperatures 100 K above the glass transition temperature Tg. The immobilized regions are estimated to involve about two monomeric units. The functional groups in the supramolecular structures are rigid or exhibit 180° ‐phenyl flips dependent on their location in the middle or in the edges, respectively. Polar units which are not enclosed in the clusters and dispersed in the polymer matrix undergo fast isotropic motions.
Activation of SiO2‐supported zirconocene catalysts by common trialkylaluminiums
Authors: Soga Kazuo , Shiono Takeshi , Kim Hyun Joon
Published: April 2003

A modified SiO2 was prepared by reacting SiO2 with Cl2Si(CH3)2 in toluene, on which methylaluminoxane (MAO) was supported to obtain a catalyst precursor. The mixture of the precursor and Cp2ZrCl2 (Cp: cyclopentadienyl) gave polyethylene in a high yield even by using common trialkylaluminiums as cocatalyst. Surprisingly, the MAO‐free catalyst system composed of the modified SiO2 and Cp2ZrCl2 was also found to be activated by common trialkylaluminiums.
Coordinated pair chain folding model for solution‐grown polyethylene single crystal
Authors: Hu Andrew Teh , Chang Hwei‐Liang
Published: April 2003

A new regular chain folding model, namely the “coordinated pair chain folding model” (CPCFM) is proposed to revive the consideration that a polymer chain should fold regularly rather than randomly in solution‐grown polyethylene single crystals.
Influence of aryl substituents on the thermal and solubility behavior of poly(p‐phenylene terephthalate) and poly(p‐phenylene terephthalamide)
Authors: Hatke Wilfried , Land Horst‐Tore , Schmidt Hans‐Werner , Heitz Walter
Published: April 2003

The substitution of poly(p‐phenylene terephthalate) and poly(p‐phenylene terephthalamide) with phenyl and biphenylyl substituents (4‐biphenylyl and 2‐biphenylyl) in the terephthalic acid unit lowers the melting temperatures and crystallization tendency and increases the solubility. The melting temperatures of the polyesters are in the range of 285–350°C. Melting of the polyamides occurs between 440–490°C. The polyamides begin to decompose in the same temperature range. In polyesters as well as in polyamides the 2‐biphenylyl substituent was found to be more effective in decreasing the crystallinity, lowering the melt transition temperatures and increasing the solubility.