bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamics of cycloalkenes, of their bulk polymerization in the presence of matathesis catalysts and of polyalkenes
Authors: Lebedev Boris , Smirnova Natal'ya 
Published: April 2003

AbstractPrincipal regularities of the thermodynamics in ring‐opening bulk polymerization of cycloalkenes (cyclononene, cyclodecene, cycloundecene, cyclododecene, cyclotridecene, cyclotetradecene and cyclopentadecene) as established from precise calorimetric studies are considered. For all monomers and polymers studied the temperature dependence of the heat capacity was investigated in the range of 5 K to 400 K, and the temperatures and enthalpies of physical transitions were determined. The enthalpies of combustion of a number of monomers and polymers were measured, and for some monomers direct calorimetric measurements of enthalpies of polymerization were made. From the data obtained the thermodynamic functions H0(T) − H0(0), S0(T), G0(T) − H0(0) were calculated for all compounds under study in the range from 0 to 400 K and for some monomers and polymers the enthalpies of formation at T = 298,15 K and pressure p = 101,325 kPa. For monomers in the glassy state zero entropies Sgl0(0) were estimated and the difference in zero enthalpies of polymers in the glassy and the crystalline state Hgl0(0) − Hcr0(0) was determined. Enthalpies, entropies and Gibbs functions of polymerization were calculated between 0 and 400 K at standard pressure.
Synthesis and cationic ring‐opening polymerization of 2‐methylene‐7‐oxabicyclo[2.2.1]heptane
Authors: Bai Ruke , Li Shihua , Zou Yinfang , Pan Caiyuan , Uryu Toshiyuki 
Published: April 2003

AbstractA new unsaturated bicyclic ether, 2‐methylene‐7‐oxabicyclo[2.2.1]heptane (4) was synthesized by successive Diels‐Alder addition of furan to acrylonitrile, hydrogenation of cyano compound 5, and Hofmann degradation of the quaternary ammonium hydrate 7 derived from the amine 6. Cationic polymerization of the monomer 4 was carried out in CH2Cl2 using BF3 · OEt2, PF5, SbCl5 and SnCl4 as catalysts in the temperature range of −20 to −25°C. White or slightly yellow powdery polymers of low molecular weight were obtained with PF5 and BF3 · OEt2 as catalysts, while no polymer was obtained with SbCl5 and SnCl4 as initiators. The IR, 1H and 13C NMR spectra of the polymers indicated that they consist of three kinds of repeating units, that is, two unsaturated units caused by ring‐opening polymerization and one addition unit. Using proton NMR data of the polymers, the distribution of repeating units was calculated. A polymerization mechanism is proposed. The thermal stability of the obtained polymers is discussed.
Synthesis, solution properties, and glass transition temperatures of polymethacrylates with alicyclylmethyl side groups
Authors: Pateropoulou Despina , Siakali‐Kioulafa Ekaterini , Hadjichristidis Nikos , Nan Shouyan , Mays Jimmy W. 
Published: April 2003

AbstractThe synthesis, solution properties, and glass transition temperatures of polymethacrylates having alicyclic rings connected to the ester linkage via methylene spacers are reported. The rings cover the range in size from cyclobutyl to cycloundecyl. An attempt was also made to prepare and study poly(cyclopropylmethyl methacrylate), but free radical solution polymerization led to gels. Solution and thermal properties of these polymers are compared to those previously reported for polymethacrylates with both alicyclyl and n‐alkyl substituents. The introduction of the methylene spacer between the ester linkage and the ring results, for small rings, in diminished characteristic ratios relative to those obtained for the alicyclyl materials. Chain flexibilities of poly(alicyclylmethyl methacrylates) are instead found to be identical to those of poly(n‐alkyl methacrylates) having the same number of carbons. The glass transition temperatures of the poly(alicyclylmethyl methacrylates) are generally intermediate to those observed for alicyclyl and n‐alkyl methacrylates, but are closer to the former.
Critical epitaxial layers of different kinds of polyethylene on highly oriented isotactic poly(propylene) substrates
Authors: Yan Shouke , Lin Jian , Yang Decai , Petermann Jürgen 
Published: April 2003

AbstractEpitaxial crystallization of high‐density polyethylene (HDPE), linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE) in the epitaxial system with highly oriented isotactic poly(propylene) (iPP) has been investigated by electron microscopy. The results obtained by bright field electron microscopy and electron diffraction confirmed that all of the three kinds of PE (HDPE, LLDPE and LDPE) have the ability of epitaxy on iPP surfaces. There exists a critical thickness of the PE layer in which the PE can grow epitaxially on iPP substrates. When the PE/iPP layered films are heat‐treated at a temperature above the melting temperature (Tm) of PE and below Tm of iPP for 10 min and then quenched to room temperature, the critical layer thickness of epitaxial HDPE, LLDPE and LDPE is about 250, 120 and 30 nm, respectively. For PE further apart from the interface, the epitaxial orientation becomes disturbed due to simultaneous spherulitic nucleation or lamellar twisting of the epitaxially grown lamellae.
p‐Phenylene‐2,2′‐bis(3‐aminopropenenitrile) and its polymerization with terephthaloyl dichloride
Authors: Sikkema Doetze J. , Reichwein John 
Published: April 2003

AbstractWith the aim of preparing a new rigid rod type polymer, we worked out a synthesis of the title compound: 1,4‐bis(chloromethyl)benzene was reacted with KCN, and the product was formylated with ethyl formate; exchange of enol by enamine function by treatment with ammonium acetate completes the synthesis. Polymerization of this only mildly nucleophilic monomer with terephthaloyl dichloride proceeded rather slowly and only moderate chain length polymer proved accessible. The cyclization envisioned could be shown to proceed as desired in a model compound from the title compound with benzoyl chloride. Upon putative cyclization, the polymer remained soluble in sulfuric acid.
Détermination des masses et des distributions moléculaires d'un poly(aryléthercétone‐co‐sulfone) semi‐cristallin (HTX) à l'aide d'une méthode de dérivatisation chimique, 2. Chromatographie d'exclusion stérique du HTX sulfoné
Authors: Daoust Daniel , Godard Pierre , Devaux Jacquex 
Published: April 2003

AbstractHTX, a poly(aryletherketone‐co‐sulfone), is characterized by size exclusion chromatography (SEC) at room temperature. As HTX is not soluble in any solvent compatible with the SEC instrumentation, a derivatization procedure is applied in order to prepare a modified copolymer with improved solubility properties. This derivatization consists in a sulfonation by concentrated sulfuric acid. The derivative polymer is soluble in N‐methyl‐2‐pyrrolidone (NMP), a classical SEC solvent. Sulfonated HTX (HTXS) is a polyelectrolyte. Consequently, a salt is added to NMP to perform reliable viscometric and SEC analyses. The SEC method is standardized with the establishment of the universal calibration with poly(methyl methacrylate) standards and the determination of the Mark‐Houwink‐Sakurada relationship of HTXS in NMP‐salt at 25°C. Finally, the reliability of the derivatization procedure and of the SEC method is confirmed by comparison with molecular masses from NMR.
Electrooptically active polymers. Non‐linear optical polymers prepared from maleic anhydride copolymers by polymer analogous reactions
Authors: Ahlheim Markus , Lehr Friedrich 
Published: April 2003

AbstractThe synthesis of new high‐molecular‐weight non‐linear optical (NLO) polymers, prepared by polymer analogous reaction of maleic anhydride copolymers with aminoalkyl functionalized azo dyes is described. The thermal behavior of the resulting copolymers is discussed in terms of molar dye concentration, polymer main‐chain flexibility and spacer length on the glass transition temperature.
Polymerization of 1,2‐epoxypropane and 1,2‐epoxycyclohexane by diethylzinc‐polyhydric phenol and/or phenol or 1‐phenoxy‐2‐propanol as catalysts
Authors: Kuran Witold , Listoś Tomasz 
Published: April 2003

Abstract1,2‐Epoxypropane and 1,2‐epoxycyclohexane were polymerized in the presence of catalysts derived from reactions of diethylzinc with a polyhydric phenol (4‐tert‐butylcatechol, pyrogallol) and/or phenol or 1‐phenoxy‐2‐propanol in 1,4‐dioxane solution, varying the polymerization temperature and time. The polymers formed in these polymerizations were analysed by means of 1H NMR, 13C NMR and UV spectroscopy in terms of the polymer chain microstructure and chain end‐groups. The poly(propylene oxide) (PPO) obtained appeared to be a high‐molecular‐weight polymer with prevailing isotactic diads (mole fraction in the range of 0,65–0,72). It was found to consist of a predominant amorphous (atactic) fraction and a crystalline (isotactic) fraction. An enhancement of both the crystallinity and the average molecular weight of PPO was observed with an elongation of the duration of the polymerization. Therefore, it was concluded that the catalyst enantioselectivity increases with progressing polymerization. The poly(cyclohexene oxide) (PCHO) obtained appeared to be a polymer with prevailing syndiotactic diads (mole fraction in the range of ca. 0,58–0,80) and threo‐enchainement of monomeric units. This was explained in terms of inversion of the configuration at the carbon atom of the epoxide ring upon cleavage. A possible mechanism for the epoxide polymerization by the coordination catalysts studied is presented.
Telechelic polystyrene obtained by degradation of polyurethane‐polystyrene block copolymers
Authors: Kinoshita Hiroshi , Tanaka Nobuo , Araki Takeo , Ooka Masataka 
Published: April 2003

AbstractPolystyrene with one or two terminal hydroxyl groups was obtained in a high yield (88–90%) from polyurethane‐polystyrene block copolymers (PU‐PS). The block copolymers were prepared by radical polymerization of styrene with a polyurethane‐type macroazo initiator, and then the urethane bonds were degraded with 2‐aminoethanol. The purity of the hydroxylated polystyrene thus obtained, which consists predominantly of the dihydroxy‐telechelic component, was much higher (ca. 90%) than that of polystyrene obtained by conventional radical polymerization using the corresponding low‐molecular‐weight azo initiator 2,2′‐azobis(2‐cyanopropanol) (ca. 80% mono‐ and dihydroxylated polystyrene). Formation of a predominantly telechelic HO—PS—OH was confirmed from the results of the polyaddition reaction of the hydroxylated polystyrene with a diisocyanate.
Viscometric study of extremely dilute solutions of two polymers with different molecular weights
Authors: Papanagopoulos Dimitrios , Dondos Anastasios 
Published: April 2003

AbstractThe intrinsic viscosity of a polymer A (referred to as guest polymer) in a solvent containing a second polymer B (referred to as host polymer) at constant concentration was found to be lower than the intrinsic viscosity of the same polymer in the pure solvent. This decrease becomes more important as the molecular weight of the host polymer becomes smaller. When the intrinsic viscosity of a low‐molecular‐weight guest polymer is measured in the presence of a high‐molecular‐weight host polymer, no such decrease is observed and the decrease of the dimensions of a guest polymer in the presence of a host polymer of comparable molecular weight, is insignificant. A parameter bAB is introduced characterizing the hydrodynamic interactions between the two polymers in the region of extremely dilute solutions. The values of bAB strongly depend on the difference in the segment densities between the two polymers.
Spinning and characterization of fibers from poly(2,6‐dichloro‐p‐phenyleneterephthalamide): a study of constitutional isomerism and solid‐state arrangements by comparison between simulation and experiment
Authors: Glomm Bernhard H. , Rutledge Gregory C. , Küuchenmeister Frank , Neuenschwander Peter , Suter Ulrich W. 
Published: April 2003

AbstractFibers of three constitutionally isomeric rigid‐rod polymers, produced by polycondensation of 2,6‐dichloro‐p‐phenylenediamine and terephthaloyl dichloride, were spun from nematic solutions and characterized by wide‐angle X‐ray diffraction (WAXD) measurements and mechanical tests. A post‐spin heat treatment was employed to improve the low degrees of orientation and crystallinity that the untreated fibers showed. The dominating crystal structure of constitutionally ordered head‐to‐head/tail‐to‐tail fibers seems to be very similar to “Modification II” of the fibers from poly(p‐phenyleneterephthalamide) (PPTA), but the fibers do not suffer a comparable structural transformation upon heat treatment. Influences of the constitutional regularity in the chains on the crystal structure, structural order and mechanical properties of the fibers could be observed. Both the observed crystal structure and the experimentally determined mechanical properties agree well with the results of detailed atomistic modeling predictions.
Ionic conduction of cross‐linkable oligo(oxyethylene)‐branched poly(phosphazene)
Authors: Tada Yuji , Sato Moriyuki , Takeno Noboru , Kameshima Takashi , Nakacho Yoshifumi , Shigehara Kiyotaka 
Published: April 2003

AbstractA new cross‐linkable polyphosphazene [AEP7] in which allyl groups were introduced at the ends of the etheric side chains of the polymer was prepared. The LiClO4/AEP7 hybrids showed relatively high ionic conductivity of 7,9·10−5 S·cm−1 at 25°C with 6 wt.‐% of LiClO4. The ionic conductivity of the hybrids remained unchanged before and after cross‐linking by UV‐irradiation. The dimensional stability or the mechanical strength of the hybrids was improved upon cross‐linking. Additionally, the cross‐linked AEP7(29)/propylene carbonate (PC)(60)/LiClO4(11) (wt.‐%) hybrids, in which PC was used as a plasticizer, showed an ionic conductivity as high as 3,1·10−3 S·cm−1 at 25°C.
Particle growth in butadiene emulsion polymerization, 1. The use of Fremy salt as aqueous radical scavenger
Authors: Verdurmen Edwin M. , Geurts John M. , German Anton L. 
Published: April 2003

AbstractThe kinetics of the seeded emulsion polymerization of butadiene in combination with variable Fremy salt (potassium nitrosodisulfonate) concentrations was investigated in order to monitor non‐steady state kinetics necessary for obtaining information on entry and exit of radicals from latex particles. Fremy salt is used because it is an entirely water‐soluble stable radical that in principle can scavenge water‐soluble radicals produced by a water‐soluble initiator like peroxodisulfate, but allegedly will not interfere with radicals within latex particles. Adequate buffering of the pH is a prerequisite for stable Fremy salt concentrations in time. Emulsion polymerizations in the presence of Fremy salt showed that not all radicals in the aqueous phase of a swollen polybutadiene latex are scavenged. The use of Fremy salt to monitor non‐steady state kinetics in the seeded emulsion polymerization of butadiene in the presence of tertiary dodecyl mercaptan yields no satisfying results. The use of Fremy salt seems to be restricted to systems where the rate of polymerization is strongly influenced by variation in initiator concentration, i.e. the styrene system or the butadiene system in the absence of tertiary dodecyl mercaptan.
Particle growth in butadiene emulsion polymerization, 4. The promoting effect of mercaptans
Authors: Verdurmen Edwin M. , Verstegen John M. , German Anton L. 
Published: April 2003

AbstractThe observation that butadiene emulsion polymerizations in the presence of fatty acid emulsifiers need minimal amounts of tertiary or n‐dodecanethiols to polymerize at a reasonable rate is often referred to as the promoting effect of mercaptans and is evaluated in this paper. Experimental evidence is presented which shows that fatty acid emulsifiers can actively reduce the average number of radicals per particle. In this paper it will be shown that three components are necessary for retardation of the rate of polymerization in the absence of dodecanethiol to occur: (1) Only diene monomer polymerizations show retardation. (2) Only peroxodisulfate‐initiated polymerizations show retardation. (3) Retardation of the rate of polymerization only occurs in the presence of fatty acid emulsifiers. These three components are combined for the first time in a reaction scheme which is an extension of a reaction scheme proposed by Kolthoff in 1951. Experimental evidence justifies the suggestion that reaction between a fatty acid radical and butadiene play an important role in the promoting effect.
Kinetic study on thermal polymerization and cross‐linking of pre‐irradiated 1,4‐butanediol diacrylate
Authors: Selli Elena , Bellobono Ignazio Renato , Oliva Cesare 
Published: April 2003

AbstractThe thermal polymerization and cross‐linking of 1,4‐butanediol diacrylate taking place after irradiation was followed kinetically in the temperature range from 60 to 140°C. Low conversions were reached by polychromatic pre‐irradiation in the absence of any photoinitiating species. The disappearance of double bonds follows first‐order kinetics, up to degree of conversion 0,4 < x < 0,5, and then proceeds up to high x values, according to a multiple relaxation phenomenon, characterized by the same mean relaxation lifetime as first‐order kinetics. Activation parameters also were calculated. The present results on the decay of double bonds are discussed in the framework of the classical polymerization mechanism and in connection with previous kinetical data on the decay of radicals trapped in the same pre‐irradiated monomer, obtained by electron paramagnetic resonance (EPR) measurements. Propagation and termination processes depend in the same way on the mobility of the vitrified polymerized network, both being diffusion‐controlled.
Block copolymers by sequential group transfer polymerization: poly(methyl methacrylate)‐block‐poly(2‐ethylhexyl acrylate) and poly(methyl methacrylate)‐block‐poly(tert‐butyl acrylate)
Authors: Masař Bohumil , Vlček Petr 
Published: April 2003

AbstractPoly(methyl methacrylate)‐block‐poly(2‐ethylhexyl acrylate) (PMMA‐block‐PEHA) and poly(methyl methacrylate)‐block‐poly(tert‐butyl acrylate) with a methacrylate/acrylate unit ratio of 1:1 and 1:3, 16000 < Mn < 44000 and 1,9 < Mw/Mn < 2,5, were prepared by sequential group transfer polymerization using (1‐methoxy‐2‐methyl‐1‐propenyloxy)trimethylsilane as initiator and tetrabutylammonium fluoride monohydrate as a catalyst in tetrahydrofuran at −30°C, PMMA being the first block. The increase in Mn during the successive addition of monomers is linearly dependent on the (co)polymer yield and size‐exclusion chromatography (SEC) curves are shifted towards higher molecular weights in comparison with PMMA macroinitiators. The block structure of the copolymers was also proven by extraction experiments. The presence of homopolymers in the copolymers was not detected. When the former copolymer is prepared in a reverse way (PEHA segment being the first), the MMA polymerization ceases at ≈ 43–45% conversion.
Synthesis of polyvinylamine and polymer analogous reactions
Authors: Fischer Thomas , Heitz Walter 
Published: April 2003

AbstractPolyvinylamine (PVVAm) was synthesized using the precursor poly(tert‐butyl N‐vinylcarbamate) (PTBNVC). The monomer synthesis was improved, and the control of the molecular weight of the PTBNVC and the PVAm by a transfer reaction with the solvent is demonstrated. TBNVC was radically polymerized. In suspension polymerization molecular weights of 106 g/mol are accessible. Different polymer analogous reactions were carried out. The resulting polymers are methylated polyvinylamine, poly(N‐vinylureas), poly(N‐vinylalkanamides) and PVAm‐adducts with acrylic acid derivatives.
On the intrinsic viscosity of anionic and nonionic rodlike polysaccharide solutions
Authors: Chun Myung‐Suk , Park O Ok 
Published: April 2003

AbstractThe ionic strength dependence of intrinsic viscosity as a function of molecular weight was observed substantially for the anionic xanthan polyelectrolyte, while the intrinsic viscosity of nonionic schizophyllan does not change with ionic strength. Ultrasonic degradation was applied as the best mean of obtaining polymer fractions of different molecular weights. It is true, as expected, that schizophyllan has a more rigid triple helix backbone than that of xanthan. As the molecular weight increases, the extension coefficient ε of the xanthan chain with ionic strength is found empirically to increase by order 1,48 of molecular weight. Using the Yamakawa‐Fujii theory for worm‐like chains, both the persistence length q and the contour length Lc were determined from the best fit of the experimental data of intrinsic viscosity for different ionic strengths to the theoretical curves. The stiffness parameter was established from the ratio of the Kuhn statistical segment length (i. e., twice the persistence length) to the contour length. As the molecular weight decreases, stiff chains of short degraded xanthan become rodlike, while they become gradually worm‐like with increasing molecular weight. It also can be seen that the chain stiffness depends on the ionic strength.
Dielectric properties of poly[bis(trifluoroethoxy)phosphazene] and poly[bis(m‐methylphenoxy)phosphazene]
Authors: Moriya Keiichi , Nishibe Yasushi , Yano Shinichi 
Published: April 2003

AbstractDielectric properties of poly[bis(trifluoroethoxy)phosphazene] (PFEP) and poly[bis(m‐methylphenoxy)phosphazene] (PmMPP) were studied in a temperature range from −195 to 120°C and at several frequencies between 0,1 and 100 kHz. In PFEP, two relaxations, an α relaxation above the glass transition temperature (Tg) and a β relaxation below Tg, which are related to a glass‐rubber transition and a local molecular motion of short segments, respectively, were observed. However, PmMPP shows no β relaxation. From the above dielectric results, it was concluded that side groups play an important role in molecular motion of the polyphosphazenes. In PmMPP a γ′ relaxation was found below Tg by immersing the polymers into water. The γ′ relaxation is related to the molecular motin of absorbed water.
The structure of poly(ethylene oxide)‐salt complexes with 13c CPMAS NMR and relaxation studies
Authors: Maunu Sirkka L. , Soljamo Kari , Laanterä Matti , Sundholm Franciska 
Published: April 2003

Abstract13C cross polarization and magic‐angle spinning (CPMAS) NMR studies were made on poly(ethylene oxide) (PEO) complexed wit LiClO4, NaClO4, BaSCN, Bal2 and Ba(ClO4)2. The proton and carbon spin‐lattice relaxation times in a rotating frame (T1ρH, T1ρC) as well as the rate of cross polarization were measured at room temperature. For Ba(ClO4)2 the measurements were made with different polymer molar masses and salt concentrations. The changes in relaxation behaviour indicate changes in polymer chain mobility as well as strong interaction between ions and PEO chains. The T1ρH and T1ρC decrease with decreasing salt concentration towards the relaxation times of the pure polymer. Nonexponential relaxation behaviour was found for the samples according to the T1ρC and TCH measurements.
Catalytic behavior in the olefin oxidation and characterization of polyacrylonitrile‐palladium complexes
Authors: Jia Cheng‐Guo , Jin Feng‐You , Pan Hui‐Quan , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2003

AbstractWe prepared polyacrylonitrile‐palladium(PAN‐Pd) complexes in which palladium is coordinated with approximately 2 nitrile groups and has a mixed valency (Pd(0) + Pd(I) + Pd(II)). The complexes contain small palladium aggregates (diameter ca. 50 Å) which are rather stable due to the coordination of palladium to the polymer. The PAN‐Pd complexes are highly active and stable catalysts for the oxidation of olefins in the presence of cocatalysts like CuCl2·2H2O. They could be recycled 5 times without loss of activity in the oxidation of 1‐heptene.