bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the internal friction characteristics of a polyaryl ether sulfone with bulky substituent below the glass transition temperature
Authors: Zhang Mingqiu , Zeng Hanmin , Zhang Jinxiu 
Published: April 2003

AbstractThe temperature and frequency dependence of internal friction of a polyaryl ether sulfone with cardo side groupsSystematic name: poly(phthalidylidene‐1,4‐phenyleneoxy‐1,4‐phenylenesulfonyl‐1,4‐phenyleneoxy‐1,4‐phenylene).
(1) are measured using a multi‐function torsion pendulum below the glass transition temperature (531 K). Two relaxation peaks are observed at 328 K and 150 K (for 0,1 Hz). The elementary processes of the two relaxations are found to be different from each other: the relaxation at higher temperature is an ordering process and that at lower temperature is a disordering one.
Conformational changes of amorphous poly(ethylene terephthalate) films during uniaxial stretching
Authors: Shen Deyan , Long Fujin , Wen Zaiqing , Qian Renyuan 
Published: April 2003

AbstractRapid scanning Fourier transform infra‐red spectroscopy was used to follow the changes in the population of trans conformers and in the infra‐red dichroic functions of the bands characterizing the trans (T) and gauche (G) conformers and the chains in the amorphous regions during stretching of a solution‐cast amorphous poly(ethylene terephthalate) (PET) film A in the glassy state (67°C) and in the rubbery state (88°C). Stretching at 67°C showed a yield stress peak followed by strain softening in the stress‐strain curve. The population of trans conformers in the amorphous and crystalline regions, Ta + Tc, decreased in the pre‐yielding region and then increased continuously after yielding. The T conformers formed during post‐yield stretching showed high orientation, while the G conformers remained in low degree of orientation. Stretching at 88°C showed no pronounced yield stress peak in the stress‐strain curve, and the population of T conformers did not change until the beginning strain‐induced crystallization. A solvent‐cast PET film annealed at 67°C for 24 h, the film N, showed a sharp and high yield stress peak in the stress‐strain curve, and strain‐induced crystallization occurred at lower draw ratio as compared to the film A. The film A showed a non‐equilibrium high population of Ta conformers, part of which reverted to G conformers during sub‐Tg annealing.
Thermotropic polyesters with flexible spacers in the main chain and oligo(oxyethylene) substituents
Authors: Bhowmik Pradip K. , Garay Paul O. , Lenz Robert W. 
Published: April 2003

AbstractAn expanded series of alkoxy‐and oligo(oxyethylene)‐substituted thermotropic polyesters with flexible decamethylene spacers in the main chain, which have higher molecular weights than those described in an earlier report, were prepared and characterized. All of the polymers in the series are soluble in common organic solvents, and have low melting temperatures (Tm) and isotropization transition temperatures (Ti). The members of the series with oligo(oxyethylene) substituents form both smectic and nematic phases.
Radical and spontaneous thermal polymerizations of some captodative‐substituted acrylates
Authors: Tanaka Hitoshi , Kameshima Takashi , Sasai Kensuke , Sato Tsuneyuki , Ota Tadatoshi 
Published: April 2003

AbstractThe polymerization of some captodative‐substituted acrylates was examined in the presence and absence of 2,2′‐azoisobutyronitrile (AIBN) at 60 °C. Methyl acrylates, substituted by acetoxy, methoxy and ethylsulfenyl groups in α‐position, and tert‐butyl α‐methoxyacrylate homopolymerized with and without this initiator. The rate of AIBN‐initiated homopolymerization of methyl α‐acetoxyacrylate was as high as that of methyl methacrylate in spite of the captodative‐substituted monomer, and these acrylates also gave polymers spontaneously in remarkably high yield even under conditions under which styrene and methyl methacrylate are not polymerized. Copolymers of these monomers with styrene also were obtained in the presence and in the absence of AIBN. The mechanism of the initiation of the spontaneous thermal polymerization is discussed on the basis of ESR spectra, reaction intermediates and radical inhibition experiments.
Physicochemical behaviour of the sodium salt of carboxymethylcellulose in dye, salt and surfactant environments
Authors: Gupta Syamasri , Moulik Satya Priya , Das Akhil Ranjan 
Published: April 2003

AbstractThe interactions of the polyelectrolyte carboxymethylcellulose (sodium salt) with salts, dyes and surfactants have been studied by viscometry, conductometry, spectrophotometry and membrane potential measurements. The compact conformation of the polyelectrolyte has been realized in all the environments. The average radius of gyration, s̄, and the intrinsic viscosity, [η], decline with increasing concentration of the additives. This and the narrow pseudoternary single‐phase zones for both the carboxymethylcellulose (sodium salt)/CTAB (cetyltrimethylammonium bromide)Systematic name: hexadecyltrimethylamounium bromide.
/ Triton X‐100 (α‐alkylphenyl‐ω‐hydroxypoly(oxyethylene))/water and the carboxymethylcellulose (sodium salt)/CTAB/Tween 20 (poly(oxyethylene)sorbitan monolaurate)/water system suggest instability of the polymer in presence of the additives. The spectral results indicate dye aggregation (stacking) on the flexible polymer chain. The binding of CTAB with the polyelectrolyte is Langmuirian in absence of KCl and strongly co‐operative in its presence. Thermodynamic parameters have been evaluated in the light of both Langmuir and Scatchard equations. Considering water and polymer to be in separate phases, the free energy of transfer of CTAB from the aqueous to the polymer phase has been calculated.
Crosslinking index, molecular weight distribution, and rubber equilibrium shear modulus during polyfunctional crosslinking of existing polymer, 1. Theory
Authors: te Nijenhuis Klaas 
Published: April 2003

AbstractA statistical theory is presented, concerning polyfunctional crosslinking of polymer initially heterogeneous with respect to molecular weight. It is an extension of Flory's theory concerning tetrafunctional crosslinking. Relationships between the equilibrium shear modulus, the crosslinking index, the sol fraction, and the functionality of the crosslinks are given for uniform polymer and for non‐uniform polymer of unknown as well as known molecular weight distributions. It appears that at and just beyond the gel point, fractionation of the primary polymer has occurred in such a way that the number‐ and weight‐average molecular weights of the primary polymer molecules, present in the network fraction, are equal to the weight‐ and z‐average molecular weights of the original primary polymer, independent of the functionality of the crosslinks.
Polymers with pendant carbazolyl groups, 5. Photoconductive properties of some carbazole derivatives with electron donor and acceptor groups
Authors: Haarer Dietrich , Meyer Harald , Strohriegl Peter , Naegele Dieter 
Published: April 2003

AbstractIn this paper photocurrents of N‐isopropylcarbazole (NIPC) derivatives in polycarbonate hosts are reported and compared to data for a benzotriazole derivative (BTA). The carbazole moiety was substituted with both electron donor and acceptor substituents and the photoconductivity was measured as a function of concentration, electrical field, and temperature using the time‐of‐flight (TOF) technique. The observed increase of the effective mobility of charge carriers at low dopant concentrations upon substitution with a moderate electron acceptor is in contrast to literature data for some other materials. We interpret this increase as being due to an increase in the delocalisation radius of the transport state of the substituted carbazole molecule. The field dependence of the effective mobility shows Poole‐Frenkel behaviour, which is attributed to polaron formation. Comparison of the effective mobility of the NIPC derivatives with BTA shows that the size of the molecule plays a decisive role for the absolute value of the effective mobility.
New polymer syntheses, 51. Thermotropic homopolyesters of 4,4′‐dihydroxybiphenyl and substituted terephthalic acids
Authors: Kricheldorf Hans R. , Weegen‐Schulz Bettina , Engelhardt Jürgen 
Published: April 2003

AbstractPolyesters were prepared from 4,4′‐dihydroxybiphenyl and various aryloxyterephthalic acids or various disubstituted terephthalic acids. The aryloxyterephthalic acids were prepared by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The disubstituted terephthalic acids were synthesized by double alkylation of diethyl 2,5‐dihydroxyterephthalate with various alkyl bromides containing aromatic rings in the ω‐position. The silyl method was primarily used for the polycondensation procedure. The resulting polyesters were characterized by elemental analyses, viscosity measurements, wide‐angle X‐ray scattering and differential scanning calorimetry measurements, and by optical microscopy. All polyesters proved to be semicrystalline, meltable materials forming a nematic phase above their melting points. The substituents of terephthalic acid enhance the solubility in organic solvents, so that all polyesters are soluble in CH2Cl2/trifluoroacetic acid mixtures and some of them even in hot N,N‐dimethyl‐formamide or methyl benzoate.
New polymer syntheses, 52. Thermotropic copolyesters of various substituted terephthalic acids and 4,4′‐dihydroxybiphenyl
Authors: Kricheldorf Hans R. , Engelhardt Jürgen , Weegen‐Schulz Bettina 
Published: April 2003

AbstractVarious copolyesters were synthesized from 4,4′‐dihydroxybiphenyl and combinations of two or three differently substituted terephthalic acids. Various synthetic methods were studied; polycondensations of terephthaloyl dichlorides in dry pyridine gave the highest molecular weights. All copolyesters are semicrystalline and form a nematic melt above their melting points. Several copolyesters are well soluble in aprotic organic solvents, such as dichloromethane, N,N‐dimethyl‐formamide (DMF), methyl benzoate or chlorobenzene. A blend of such a soluble polyester (5 wt.‐%) with bisphenol‐A polycarbonate (poly(oxycarbonyl‐oxy‐1,4‐phenyleneisopropylidene‐1,4‐phenylene)) was prepared from a cosolvent and various mechanical data were measured. These data were compared with those of an aromatic thermotropic polycarbonate.
Polymer complexing equilibria. A new general approach based on the copolymerization equilibrium
Authors: Szymanski Ryszard 
Published: April 2003

AbstractA new general treatment of the equilibria of complex formation between polymers and multivalent species (e.g. metal cations) is given. The treatment is based on the analysis of the equilibrium in the copolymerization of monomers and their complexes with multivalent species. An example of the analysis of experimental data for complexation of sodium tetraphenylborate with poly(oxyethylene) in methanol is presented.
Kinetics of the polymer‐analogous reaction of poly[(methyl methacrylate)‐co‐(methacrylic acid)] with epichlorohydrin
Authors: Sandner Barbara , Ziegler Hans‐Jörg 
Published: April 2003

AbstractPoly[(methyl methacrylate)‐co‐(glycidyl methacrylate)] (poly(MMA‐co‐GMA)) was obtained by polymer‐analogous reaction of poly[(methyl methacrylate)‐co‐(methacrylic acid)] with an excess of epichlorohydrin (ECH) in the presence of a quaternary ammonium salt R4NX as catalyst. The kinetics of the addition reaction and the consecutive transepoxidation reaction was studied at 50–90°C. The rate constant of the addition reaction is one order of magnitude higher with E1 = 71 kJ · mol−1 than that of the transepoxidation reaction with E2 = 83 kJ · mol−1. The rate constants rise linearly with increasing concentration of the catalyst R4NX. The equilibrium constants K ≈ 2,3 of transepoxidation of glycidyl methacrylate (GMA) as well as of poly(MMA‐co‐GMA) both with 1,3‐dichloropropane‐2‐ol were determined in butyl acetate and dimethylformamide as solvent at 80–100°C. During the reverse transepoxidation reaction of 3‐chloro‐2‐hydroxypropyl methacrylate (CHPM) as well as of its MMA‐copolymer with equimolar amounts of ECH, side products were formed from the beginning of the reaction and the equilibrium was not established. The addition of ECH to CHPM was observed as a side reaction.
Cooperative structure formation by combination of covalent and association chain polymers, 3. Control of association polymer chain length
Authors: Hilger Christopher , Stadler Reimund 
Published: April 2003

AbstractThermoanalytical studies on an order‐disorder transition resulting from supramolecular organization of hydrogen bond motifs in an unpolar (polymer‐) matrix are reported. Functional groups having two potential sites for hydrogen bonding are located statistically along the polymer backbone. Multistep hydrogen bond formation leads to the formation of association chains whose lengths can be controlled by addition of monofunctional groups like in conventional stepgrowth polymers. The association chain length is estimated from the variation of transition enthalpy and ‘melting’ temperature.
Water‐swelling, hydrolyzable gels through polyaddition of H3PO4 to diepoxides
Authors: Nyk Andrzej , Klosinski Pawel , Penczek Stanislaw 
Published: April 2003

AbstractPolyaddition of phosphoric acid to diepoxides, studied mostly with diepoxybutane (2), provides either soluble or insoluble (gels) polymers, depending on polyadditions conditions. Gels swell in water and slowly hydrolyze to soluble linear/branched polymers. These soluble polymers, prepared either directly or from hydrolyzable gels, hydrolyze further but much more slowly: some are stable for months, reflecting the difference of the rates of hydrolysis of predominantly tri‐(gels) and diesters (linear polymers) of H3PO4. Kinetic analysis of polyaddition and studies of the microstructure of the polymers indicate that one can influence the relative rates of addition of epoxy groups to POH and COH groups.
Carbonyl‐olefin exchange reaction. A new route to conjugated polymers, 6. Low‐molecular‐weight products
Authors: Jossifov Christo , Schopov Ivan 
Published: April 2003

AbstractThe processes which take place with the α,β‐unsaturated compound 1,2,3,3‐tetraphenyl‐2‐propen‐1‐one (1) under the influence of WCl6 were investigated. Special attention was paid to the low‐molecular‐weight products. It was established that beside polydiphenylacetylene and benzophenone also benzil, tetraphenylethylene and molecular oxygen are present in the product mixture. Their formation is explained as a result of a redistribution of the atoms connected with double bonds according to olefin metathesis (OM), carbonyl‐olefin exchange reaction (COER) and reductive coupling (RC) of carbonyl compounds, accompanied by molecular oxygen evolution. The yields of products insoluble in methanol are sometimes higher than a simple stoichiometry would allow. This can be attributed to the participation of both the inner double bonds of the polymer and the low‐molecular‐weight products.
Synthesis of polymers containing pseudohalide groups by cationic polymerization, 1. Homopolymerization of 3,3‐bis(azidomethyl)oxetane and its copolymerization with 3‐chloromethyl‐3‐(2,5,8‐trioxadecyl)oxetane
Authors: Cheradame Hervé , Andreolety Jean‐Pierre , Rousset Eliane 
Published: April 2003

AbstractThe cationic polymerization of 3,3‐bis(azidomethyl)oxetane (BAMO) was compared with the polymerization of 3,3‐bis(chloromethyl)oxetane (BCMO). The initiating system, boron trifluoride diethyl etherate/diethylene glycol (system. name: 2,2′‐oxydiethanol) was used and it was shown that unusually high concentrations were necessary to observe polymerization. NMR analysis of poly(BAMO), produced by this initiating system, suggested that BAMO polymerization proceeds through the activated‐monomer mechanism. The oligomer functionality, which was found close to 2, supports this suggestion. It was also shown that by copolymerization of BAMO with 3‐chloromethyl‐3‐(2,5,8‐trioxadecyl)oxetane the crystallization tendancy and the glass transition temperature of poly(BAMO) decreased.
Copolymerization of maleic anhydride with ethyl cinnamate and with anethole in chloroform
Authors: Fujimori Kijohisa , Schiller Wayne S. , Craven Ian E. 
Published: April 2003

AbstractThe composition of the copolymers of maleic anhydride (MA) with ethyl cinnamate (EC) and with anethole (ANE) polymerized in chloroform solutions with a radical initiator is reported. A strong alternating tendency is observed in the ANE‐MA copolymer but EC is incorporated dominantly into the EC‐MA copolymer. Both ANE and EC form 1 : 1 charge‐transfer complexes with MA with the equilibrium constants determined to be 0,0845 and 0,026 L/mol, respectively. Applicability of the terminal, the penultimate and the complex participation models of the copolymerization mechanism is examined by non‐linear least‐square minimization technique using the most general forms of the composition equations. The complex participation model is found to be slightly in favor for both EC‐MA and ANE‐MA copolymerizations in CHCl3.
Study of heterocyclic polymers, 3. Synthesis and properties of the ampholytic heteroccylic polyelectrolyte poly[n‐(2‐hydroxy‐3‐methacryloyloxypropyl)‐pyridinium‐3‐carboxylate]
Authors: Hsu Ying Gev , Hsu Miau Jing , Chen Keng Ming 
Published: April 2003

AbstractA non‐betaine type of ampholytic heterocyclic polyelectrolyte (AHP), poly[N‐(2‐hydroxy‐3‐methacryloyloxypropyl)pyridinium‐3‐carboxylate] [poly(NHMPPC)], was synthesized by freeradical polymerization. The turbidimetric, viscometric and potentiometric properties of the polymer were studied in aqueous solution. It exhibits good salt tolerance in CaCl2 up to 100°C and a viscositiy behavior in aqueous alkali salt and hydrochloride solutions different from that of usual polyelectrolytes. The potentiometric behavior revealed that the polymer does not undergo a conformational transition during acidification and that the electrostatic repulsion along the chain is low. The polymer main chain forms compact hydrophobic areas in concentrated HCl solution, whereas in concentrated NaCl solution it extends to a more straight form.
Alternating copolymerization of butadiene and propene with the catalyst VO(ONeo)2 Cl/Al(i‐C4H9)3, 1
Authors: Arnold Manfred , Wohlfarth Lutz , Frank Willy , Reinhold Günter 
Published: April 2003

AbstractThe influence of basic reaction parameters—the ratio of catalyst components, the composition of the monomer mixture and the temperature—on the progress of the copolymerization, the molecular weight and the molecular weight distribution as well as on the composition of the copolymers obtained is reported. Conversion data for the variation of the mole ratio of comonomers show a maximum for an [Al]/[V] mole ratio of approximately 7, whereas the molecular weight of copolymers is not significantly influenced. An increase in the molecular weight of the copolymers can be obtained by an increase of butadiene content in the monomer mixture. However, there is also an increasing incorporation of butadiene into the copolymer. Raising the temperature from −60°C to 0°C results in a significant decrease in molecular weight, whereas the composition of the copolymers is not significantly changed.
A study of thermal oxidative and thermal mechanical degradation of polypropylene
Authors: Ying Qicong , Zhao Yong , Liu Yong 
Published: April 2003

AbstractA study of the mechanism of thermal oxidative and thermal mechanical degradation of isotactic polypropylene (PP) is reported. Size exclusion liquid chromatography has been applied to the study of molar mass distribution (MMD) of samples of PP under oxidative degradation in the presence of an incorporated organic peroxide and of samples subjected to repeated extrusion. The change in MMD of the samples of PP under controlled oxidative degradation at 230°C is explained by a random chain scission mechanism and those of the samples of PP extruded repeatedly from an extruder at 280°C can be elucidated by a mechanism of mechanical chain scission with a threshold degree of polymerization 2L, below which the chain will not undergo scission. The value of L was found to be around 500.
13C NMR relaxation studies of poly(vinyl alcohol) and its derivatives
Authors: Egboh Sunday , Tenhu Heikki , Soljamo Kari , Sundholm Franciska 
Published: April 2003

AbstractSpin‐lattice relaxation times (T1) have been measured by 13C NMR for poly(vinyl alcohol), poly(vinyl benzoate), poly(vinyl cinnamate) and poly(vinyl acetate) in dimethyl sulfoxide as a function of temperature and concentration. As expected, T1 increases with increasing temperature and decreases with increasing polymer concentration. The influence of the microstructure (tacticity) of the polymers on the relaxation times is negligible. T1 for the methine carbon of the polymer main chain is observed to serve as a measure of the rigidity and/or mobility of the chain. Assuming isotropic motion of the polymer chains, the activation energies for the protonated carbons were determined using the calculated correlation times.
Preparation and mesomorphic properties of new thermotropic liquid‐crystalline copoly(urethane‐carbonate)s
Authors: Sato Moriyuki , Hirata Tomohiro , Takeno Noboru , Mukaida Ken‐ichi 
Published: April 2003

AbstractNew thermotropic liquid‐crystalline (LC) copoly(urethane‐carbonate)s (4) with high inherent viscosities were prepared by melt polycondensation from 6,6′‐(4,4′‐biphenylylenedioxy)dihexanol (1) and a mixture of aliphatic bis(phenyl carbamate)s (2) and bis(phenyl carbonate)s (3) in high yields. The polymers characterized by FTIR spectra and elemental analyses show good solubilities in organic solvents such as chloroform. Flexible films were cast from the polymer solutions. Their thermotropic LC properties were evaluated by differential scanning calorimetry and observation under the polarizing microscope equipped with a hot stage. These measurements indicate that the polymers form stable LC mesophases and possess block‐like sequence distributions.
A new theoretical approach to problems of the solution behaviour of ring‐shaped polymers
Authors: Huang Jiaxian , Shen Jun , Li Chunrong , Liu Dongzhou 
Published: April 2003

AbstractIn order to explain the difference in theta temperatures between ring‐shaped polymers and their corresponding linear polymers, the Huggins parameters χ of ring‐shaped polymers is assumed to obey the dependence χ = χ1 (1 + σ ϕ2) on local segment concentration as expressed by the volume fraction of the polymer ϕ2, and σ being a constant. A comparison between theoretical results and light scattering measurements of Roovers and ourselves is satisfactory.
The role of H+ ions in the electrochemical polymerization of pyrrole
Authors: Qian Renyuan , Pei Qibing , Huang Zhitang 
Published: April 2003

AbstractPyrrole was found to polymerize electrochemically in a smooth and facile way when the immediate vincinity of the anode is at a pH of 3 ([H+] = 10−3 mol/dm3). The polymerization is inhibited by the presence of a H+ scavenger, di‐tert‐butylpyridine. Polymerization of pyrrole in a buffered solution of pH 4 gives a polypyrrole (PPy) film of slightly different chemical structure from that obtained in a buffered solution of pH 3, as shown by their IR spectra. No polymerization takes place in the buffered solution at pH > 7. These facts show the important role of H+ ions played in the electrochemical polymerization of pyrrole. Pyrrole might go through a protonated structure before it transfers an electron to the electrode, to form a cation radical which starts the polymerization. A new mechanism of polymerization is proposed in conformity with observed facts about the structure of PPy.