bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionic conduction in polyphosphazene containing oligo(oxyethylene) side chains with cyclic carbonate as terminal groups
Authors: Tada Yuji , Sato Moriyuki , Takeno Noboru , Inubushi Akiyoshi , Nakacho Yoshifumi , Shigehara Kiyotaka 
Published: April 2003

AbstractNovel comb‐type polyphosphazene derivatives with cyclic carbonate groups as the terminal function of oligo(oxyethylene) side chains [CEP] were prepared for the achievement of high ionic conductivity, when they were hybridized with LiCIO4, in accordance with increase of permittivity. The relative permittivity of CEP turned out to be extraordinarily high, i.e. 24,6, whereas that of a similar comb‐type polyphosphazene with methyl ether terminal function of side chains was less than 10 at 25°C. The [LiCIO4(5)/CEP (95 wt.‐%)] hybrid showed relatively high ionic conductivity of 7,3 · 10−6 at 25°C and 9,6 · 10−5 S · cm−1 at 60°C, respectively. From the observation of the temperature dependence of ionic conductivity at 10–60°C, it was revealed that the ionic conduction obeys the Vogel‐Tamman‐Fulcher and Williams‐Landel‐Ferry equations based on the free volume theory.
Poly(2,5‐dialkoxy‐p‐phenylene)s—synthesis and properties
Authors: Vahlenkamp Thomas , Wegner Gerhard 
Published: April 2003

AbstractThe synthesis of poly(2,5‐dialkoxy‐p‐phenylene)s (PPP) by palladium‐catalyzed polycondensation of 2,5‐dialkoxy‐4‐bromophenylboronic acids is described. Number‐average degrees of polymerization of ca. 30 have been reached at best. The characterization of the polymers by NMR, IR, UV‐VIS and fluorescence spectra, data on the bulk structure obtained by X‐ray methods, melting behavior and thermal stability are reported. PPP's with long alkoxy side chains exhibit a layered phase structure, those with short or branched alkoxy side chains, cylindrical packing. Poly(2,5‐dibutoxy‐p‐phenylene) was prepared with chain lengths 7 ≤Pn≤ 30. The polymer withPnof 30 shows thermal transitions in the bulk phase at 182°C and 227°C. It forms an anisotropic melt above 227°C which only starts decomposing if heated above 300°C. The polymers of shorter chain length show isotropic melts, with the melting point strongly depending on chain length.
Investigation of poly(vinyl alcohol)/poly(N‐vinyl‐2‐pyrrolidone) blends, 3. Permeation properties of polymer blend membranes
Authors: Ping Zhenghua , Nguyen Quang Trong , Néel Jean 
Published: April 2003

AbstractDense membranes made of poly(vinyl alcohol) (PVA) and poly(N‐vinyl‐2‐pyrrolidone) (PVP) blends of different compositions were studied in gas‐sweeping permeation of a water‐ethanol mixture containing 10 wt.‐% of water. When the PVP content increases, the steady‐state permeation flux and the water content in the permeate show sudden changes at ca. 30–40 wt.‐% of PVP in the membrane: the flux increases drastically, while the water selectivity of the membrane falls to a much lower level. The diffusion coefficients of both water and ethanol, as determined from the permeation flux changes in the transient regime, exhibit a large increase when the PVP content exceeds 30 wt.‐%, and this accounts for the flux increase. The fall in the permeation selectivity is shown to be due to a strong decrease in the sorption selectivity. The threshold of the change corresponds approximately to the PVP content at which PVA crystallites no longer exist in the blend. A further study on the states of water in the blend membranes by differential scanning calorimetry made it possible to relate these changes with a change in the interactions of water with hydrophilic sites in the polymer blend when the PVP content changes.
Radically initiated copolymers of styrene with 4‐vinylbenzylamine and its trifluoroacetamide derivative, 1. Kinetic studies of solution polymerization
Authors: Charreyre Marie‐Thérèse , Razafindrakoto Vanghi , Veron Laurent , Delair Thierry , Pichot Christian 
Published: April 2003

AbstractKinetics of radically initiated solution homopolymerization of 4‐vinylbenzylamine (VBA) and its trifluoroacetamide derivative (VBAF), and their copolymerization with styrene (S), have been investigated at 60°C in toluene and DMSO, respectively, using AIBN as initiator. kp/kt1/2 values were first estimated, showing a higher value for VBAF than for VBA and styrene. The reactivity ratios were determined to be rVBA = 2,15, rS = 0,45 for the VBA/S system and rVBAF = 0,93, rS = 1,03 for the VBAF/S one. This indicates that the reactivity of VBA is higher than that of styrene, but it is significantly lower when VBA is in its protected form (i.e. VBAF), which is well reflected in the Q, e values. Average copolymer compositions, as characterized by 1H NMR and elemental analysis, are in good agreement with the theoretical ones; in addition, comparison of the molecular weights of both series of copolymers, as obtained from GPC, suggests that the VBA monomer can act as a relatively efficient chain transfer agent.
The electron transfer behavior of some new polymers with viologen structure on the reduction of azobenzene in heterophases
Authors: Liu Fu‐Tian , Song Ning , Yu Xian‐Da , Li Shu‐Ben 
Published: April 2003

AbstractSeveral polymers with viologen structure were prepared by polymer analogous reaction with poly(vinyl alcohol) (PVA) and ethylcellulose (EC). The polymers were used as electron‐transfer catalysts (ETC) for the reduction of azobenzene, either in a Zn‐PV2+ system (reductant: Zn, in CH3CN/H2O) or a Na2S2O4‐PV2+ system (reductant: Na2S2O4, in CH2Cl2/H2O). It was found that all the polymers used in our work had the ability to mediate the reduction of azobenzene. Two factors (polymeric carrier and viologen group) are believed to affect the reduction.
High performance aromatic polyimide fibers, 3. A polyimide synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐dimethyl‐4,4′‐diaminobiphenyl
Authors: Eashoo Mark , Wu Zongquan , Zhang Anqiu , Shen Dexing , Tse Cecilia , Harris Frank W. , Cheng Stephen Z. D. , Gardner Kenncorwin H. , Hsiao Benjamin S. 
Published: April 2003

AbstractA new high molecular weight aromatic polyimide has been synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 2,2′‐dimethyl‐4,4′‐diaminobiphenyl (DMB) in p‐chlorophenol at elevated temperature. BPDA‐DMB fibers have been spun by a dry‐jet wet spinning method. The fibers were elongated and annealed at elevated temperatures above 400°C to achieve excellent mechanical properties. In seven times drawn fibers, the BPDA‐DMB molecule packs into a triclinic unit cell with dimensions of a = 2,10(2) nm, b = 1,523(8) nm, c = 4,12(7) nm, α = 61,2(6)°, β = 50,7(7)°, and γ = 78,9(6)° with the number of chain repeating units per unit cell (Z) is sixteen. After annealing at elevated temperatures, the fibers produce a small modification of the unit cell [a = 2,048(6) nm, b = 1,529(5) nm, c = 4,00(2) nm, α = 62,1(3)°, β = 52,2(3)° and γ = 79,6(3)°]. By increasing the draw ratio, both the crystallinity and crystal orientation increase. The BPDA‐DMB fibers possess a decomposition temperature of 530°C in nitrogen and 500°C in air at a 5% weight loss when the heating rate is 10°C/min. After extensive drawing, BPDA‐DMB fibers exhibit a tensile strength of 3,3 GPa and a tensile modulus of over 130 GPa. Dynamic mechanical behavior of the fibers show both α (glass transition) and β (sub‐glass transition) relaxations above room temperature. The nature of the sub‐glass transition behavior is described as a noncooperative motion attributed to the diamine portion of the molecule. The activation energy for this relaxation in as‐spun fibers is 109 kJ/mol and increases to 144 kJ/mol by increasing the draw ratio. This β relaxation is found to be crystallinity dependent. The α transition is also suppressed by crystallinity which increases with draw ratio.
Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 4. Poly(imide‐urethane‐carbonate)s based on pyromellitdiimide and 3,4:3′,4′‐biphenyldicarboximide
Authors: Hirata Tomohiro , Sato Moriyuki , Mukaida Ken‐ichi 
Published: April 2003

AbstractMain‐chain types of thermotropic liquid‐crystalline (LC) poly(imide‐urethane‐carbonate)s were synthesized by melt polycondensation of N,N′‐bis(6‐hydroxyhexyl)pyromellitdiimide or N,N′‐bis(6‐hydroxyhexyl)‐3,4:3′,4′‐biphenyldicarboximide with diphenyl hexamethylenedicarbamate and/or diphenyl hexamethylenedicarbonate. The poly(imide‐urethane)s were also obtained from the dihydroxyalkylene diimide derivatives and hexamethylene diisocyanate by polyaddition. Yields and molecular weights of the resulting polymers tended to decrease with increasing urethane units. Differential scanning calorimetry (DSC) measurements, polarizing microscopic observations and powder X‐ray analyses at various temperatures demonstrated that the carbonaterich copolymers comprising the 3,4:3′,4′‐biphenyldicarboximide derivative formed a nematic mesophase. Temperature‐dependent Fourier‐Transform infrared measurements suggest that hydrogen bonding of urethane linkages affects the formation of LC mesophases.
Heterochain polymers based on natural amino acids. Synthesis and enzymatic hydrolysis of regular poly(ester amide)s based on bis(L‐phenylalanine) α,ω‐alkylene diesters and adipic acid
Authors: Arabuli Natia , Tsitlanadze George , Edilashvili Lamara , Kharadze Darejan , Goguadze Tsisana , Beridze Vakhtang , Gomurashvili Zaza , Katsarava Ramaz 
Published: April 2003

AbstractNovel biodegradable regular poly(ester amide)s were synthesized by polycondensation of p‐toluenesulfonic acid salts of bis(phenylalanine) α,ω‐alkylene diesters (1) with bis(p‐nitrophenyl) adipate under mild conditions in organic solvents in the presence of triethyl amine as acid acceptor. Enzymatic hydrolysis (α‐chymotrypsinolysis) of the starting salts 1, the model bis(ester acetamide)s 2 and the obtained poly(ester amide)s 3 was investigated at 37°C and pH 8 using potentiometric titration. It was established that the hydrolysis rate increased with elongation of the α,ω‐alkylene chain. A strong noncovalent immobilization of the enzyme on the polymeric surface was observed.
Light controlled solubility change of polymers: Copolymers of N,N‐dimethylacrylamide and 4‐phenylazophenyl acrylate
Authors: Kröger Rainer , Menzel Henning , Hallensleben Manfred L. 
Published: April 2003

AbstractCopolymers of N,N‐dimethylacrylamide (DMA) and 4‐phenylazophenyl acrylate (PAPA) have been prepared by free‐radical copolymerization in dioxane (DMAP‐x). The molecular weights of the copolymers show a strong decrease with increasing azobenzene content due to the retardation effect of the azobenzene group. An analogous decrease in molecular weight was found with a number of polymers of DMA which were polymerized in the presence of the non‐polymerizable model 4‐phenylazophenyl propionate (PAPP). We were able to induce a lower critical solution temperature (LCST) above a certain content of azobenzene moieties in the copolymers (DMAP‐x) in contrast to the good water solubility of poly(DMA). Due to the reversible photoisomerization and the concomitant change in the dipole moment of the azobenzene moieties, the LCST depends not only on the content of azobenzene but also on the degree of isomerization. A difference in the LCST up to 20°C was found for dark adapted polymer solutions (0% Z‐isomer) and polymer solutions in the photostationary state (ca. 85% Z‐isomer). Within this temperature range the polymer can be precipitated by irradiation with light.
Liquid crystalline epoxy resins containing binaphthyl group as rigid block with enhanced thermal stability
Authors: Carfagna Cosimo , Amendola Eugenio , Giamberini Marta 
Published: April 2003

AbstractThe synthesis and characterization of a novel liquid crystalline difunctional epoxy compound, 6,6′‐bis(2,3‐epoxypropoxy)‐2,2′‐binaphthyl (4), is presented. This epoxide, obtained by glycidyl termination of 2,2′‐binaphthyl‐6,6′‐diol, shows a nematic phase between 240 and 270°C. The curing reaction was carried out in the DSC pan by mixing the epoxy monomer with 4,4'‐diaminodiphenyl sulfone (DDS) or phthalic anhydride (FA). The thermal analysis of the cured resins indicated high thermal resistance.
Lamellar structure formation in the mixture of two cylinder‐forming block copolymers
Authors: Vilesov Alexander D. , Floudas Georg , Pakula Tadeusz , Melenevskaya Elena Yu. , Birshtein Tatiana M. , Lyatskaya Yulia V. 
Published: April 2003

AbstractTwo cylinder‐forming polystyrene‐block‐polybutadiene block copolymers of type A‐B with antisymmetric composition (polymer P1 with A : B = 3 : 1 (w/w) and polymer P2 with A : B = 1 : 3 (w/w)) and their binary mixture were studied by small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) in order to determine the microphase structure. The cylindrical microstructure is confirmed for both copolymers, whereas, in the mixture, both techniques have unambiguously shown that a regular lamellar structure is obtained at the polymer‐polymer composition P1 : P2 = 1 : 1 (ratio of the numbers of chains). Qualitatively, the same results are obtained for corresponding systems simulated by the cooperative motion algorithm (CMA). Direct observations of the structure as well as the cooperative structure factors determined in the strong segregation limit for the simulated systems indicated lamellar structures in the blend of composition P1 : P2 = 1 : 1, in contrast to the microfibrillar morphology of the copolymers. The simulation additionally indicated a polymer‐polymer microseparation. The experimental and simulation results are compared with theoretical predictions based on the self consistent field theory.
Cationic polymerization of hexamethylcyclotrisiloxane by trifluoromethanesulfonic acid and its derivatives, 1. Initiation by trifluoromethanesulfonic acid
Authors: Nicol Pascal , Masure Michèle , Sigwalt Pierre 
Published: April 2003

AbstractPolymerization of hexamethylcyclotrisiloxane (D3) initiated by trifluoromethanesulfonic acid (triflic acid TfOH) was carried out under vacuum, in methylene chloride solution at 20°C. The reaction rate is first order in [D3] and the constant active sites concentration [P*] varies as [P*] = k · [TfOH] · [D3]. The two main products of the reaction, both formed in similar amount from the beginning, are the dimer D6 and a high‐molecular‐weight polymer (HP). The other cyclic products also formed are the multiples of D3 (D9, D12, …), macrocycles MC (number‐average molecular weight M̄n ≈ 104) and small amounts of D4, D5 … (with [D5] > [D4]). The concentration of HP, MC, D6, D9, D12, … and the M̄n of the high polymer grow proportionally to conversion. The main reaction giving the high polymer and D6 is interpreted as a chain reaction, the growing HP bearing at each end potentially reactive silyl triflates which may be activated by the residual acid. D6 is mainly formed by a special type of back‐biting reaction involving transitory tertiary siloxonium ions. The other cycles D3x and the macrocycles mainly result from cyclization reactions of a second population of growing macromolecules which bear a silyl ester at one end and a nucleophilic silanol group at the other end.
Synthesis of polymers with pendant spiro orthoester groups
Authors: Zamzow Manfred , Höcker Hartwig 
Published: April 2003

AbstractThis paper describes the synthesis of polymers having spiro orthoester side groups, starting from lactones with methacrylate side groups. The spiro orthoester polymers are synthesized by a reaction with an oxirane. The hydroxy‐functional lactones 3‐hydroxy‐4,4‐dimethyl‐2‐oxotetrahydrofuran (1) and 5‐hydroxymethyl‐2‐oxotetrahydrofuran (13) were esterificated with methacryloyl chloride. The esterification of 5‐oxotetrahydrofuran‐2‐carboxylic acid (6) and 2,2‐dimethyl‐5‐oxotetrahydrofuran‐3‐carboxylic acid (11) with 2‐hydroxyethyl acrylate and 2‐hydroxyethyl methacrylate yielded the functionalized precursors for the synthesis of polymeric spiro orthoesters. These monomers were polymerized and copolymerized with methyl methacrylate and characterized. Furtheron, the obtained polymers with lactone groups were converted to the corresponding spiro orthoesters using 2,3‐epoxypropyl phenyl ether in the presence of boron trifluoride.
Ring‐opening polymerization of ε‐caprolactone in the presence of dicarboxylic acids
Authors: Zhang Qijin , Wang Bin , Hong Kulun , Zhu Qingren 
Published: April 2003

AbstractThe ring‐opening polymerization of ε‐caprolactone (ε‐CL) has been investigated in the presence of succinic acid in nitrogen atmosphere at 225°C. Analysis of the resultant polymers suggests that the poly(ε‐caprolactone) (PCL) obtained has two terminal carboxylic groups. VPO, 1H NMR and titration are used to determine the number‐average molecular weight of the PCL obtained at ε‐CL to acid molar ratios of 4, 8, 12, 14, 16 and 20, respectively. It is found that the molecular weight of the PCL is not related to the ratio of ε‐CL to succinic acid except for low ε‐CL concentrations. At a molar ratio of 14, the molecular weight of PCL reaches a maximum at a reaction time of 3 h. Beyond 3 h the ester exchange reaction becomes predominant, and the molecular weight approaches the equilibrium value (M̄e) due to the ratio of ε‐CL to succinic acid in the feed.
Renewable resources, 2. Poly‐Diels‐Alder additions with disorboylamides as bisdienes and a dimaleoylamide as bisdienophile
Authors: Reinecke Martin , Ritter Helmut 
Published: April 2003

AbstractThe poly‐Diels‐Alder reactions between the disorboylamides 1 and 7 and the dimaleoylamide 9, yielding the oligomers 13 and 14, are described. The applicability of the maleoyl and the sorboyl system for poly‐Diels‐Alder additions is demonstrated in a low‐molecular‐weight model cycloaddition between the monodiene 10 and the monodienophile 11. All presented compounds contain a high amount of molecules derived from renewable resources.
Studies on microgels, 1. Microgel formation studied by gel‐permeation chromatography with an on‐line light scattering detector
Authors: Pille Ludger , Solomon David H. 
Published: April 2003

AbstractThe previously described microgel synthesis in which living poly(4‐tert‐butylstyrene) was reacted with 1,4‐divinylbenzene was studied. Samples were taken after the addition of the crosslinker and characterized by gel‐permeation chromatography (GPC) with an on‐line multi angle laser light scattering (MALLS)‐ and a differential refractive index (DRI) detector. Primary particle formation was found early in the reaction followed by interparticular crosslinking. The GPC calibration curves allowed the derivation of a branching plot. The branching plots showed, that in addition to interparticular crosslink reactions also intraparticular crosslink reactions are occurring. The plots also showed that the primary particles scale like linear polymers, which led to the conclusion that they consist of comb‐like structures with poly(4‐vinylstyrene) as the backbone and poly(4‐tert‐butylstyrene) as branches.
TiCl4/MgH2‐supported Ziegler‐type catalyst system, 3. New findings on the concentration of active sites in ethylene/1‐hexene copolymerization
Authors: Jaber Isam A. , Fink Gerhard 
Published: April 2003

AbstractThe effect of 1‐hexene on the rate constant of ethylene polymerization and on the number of active centres in the copolymerization of ethylene with 1‐hexene is reported. Using three TiCl4/MgH2Al(C2H5)3 catalysts, of different Ti contents and surface area in the polymerization reveals that the addition of small amounts of the comonomer 1‐hexene results in a two‐ to three‐fold increase in the rate of ethylene consumption when a low‐Ti‐content catalyst is used. In contrast, no fundamental change in the catalytic activity was observed when a high‐Ti‐content catalyst is employed. The determination of the concentration of active centres C* by means of the 14CO radio‐labelling technique, shows that C* in ethylene/1‐hexene copolymerization is more or less the same as in ethylene homopolymerization.
Preparation and properties of poly(amide‐imide)s derived from trimellitic anhydride, α‐amino acids, and aromatic diamines
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Wu Feng‐Yueh 
Published: April 2003

AbstractFour dicarboxylic acids containing one preformed imide ring were prepared by condensation of trimellitic anhydride with α‐amino acids such as glycine, DL‐alanine, DL‐valine, and DL‐lcucinc. These diacids were subsequently directly polycondensated with various aromatic diamines using triphenyl phosphite (TPP) and pyridine as condensing agents in N‐methyl‐2‐pyrrolidone (NMP) containing calcium chloride, producing various aliphatic‐aromatic poly(amide‐imide)s with pendant alkyl groups. The resultant polymers have inherent viscosities in the range of 0,58–2,15 dL/g and were amorphous, as revealed by wide‐angle X‐ray diffractograms. All polymers were readily soluble in a variety of solvents such as N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), and NMP, and could be cast from their DMAc solutions into transparent, flexible, and tough films. All poly(amide‐imide)s showed clear glass transition temperatures in the range of 181–313°C on the heating traces of differential scanning calorimetry (DSC). Almost all the poly(amide‐imide)s exhibited no appreciable decomposition below 370°C, with 10% weight loss being recorded above 400°C in nitrogen and air. The polymers with larger side chain attached exhibited higher solubility, but lower glass transition temperature and initial decomposition temperature.
Acoustic properties of poly(phenylene sulfide) crystallized in the presence of sorbed nitrous oxide
Authors: Böhning Martin , Schultze J. Dirk , Springer Jürgen , Lukashov Alexander , Kuzaev Oleg , Feofanov Valentin 
Published: April 2003

AbstractPoly(phenylene sulfide) annealed thermally and under the influence of nitrous oxide pressure is investigated using the acoustic vibrating reed technique. The acoustic parameters velocity of sound, c, and loss tangent, tan δ, are calculated. The discussion concerning the structural changes of the polymer during the applied annealing procedures is based on the temperature dependence of these parameters and the transition temperatures TG and T' determined therefrom.
Polymerization of olefins with the TiCl4/SiO2 catalyst system modified with MgCl2
Authors: Maria Luiz Claudio de Santa , Soga Kazuo , Shiono Takeshi 
Published: April 2003

AbstractMgCl2/TiCl4/SiO2 catalysts were prepared by treating TiCl4/SiO2 with MgCl2 · 2THF (THF: tetrahydrofuran) at different Mg/Ti ratios. The catalysts were analysed by X‐ray, electron spin resonance (ESR), atomic absorption spectrometry to determine the crystal structure, oxidation state of titanium and also contents of Ti, Al and Mg. Homo‐ and copolymerizations of ethylene and propene were conducted with them using Al(i‐C4H9)3 as a cocatalyst. The results of polymerization were correlated with the analytical data of the catalyst.
Synthese und charakterisierung von butadien/ethen/propen terpolymeren
Authors: Arnold Manfred , Reußner Jens , Utschick Hermann , Fischer Hartmut 
Published: April 2003

AbstractButadiene/ethene/propene terpolymers are synthesized by Ziegler‐Natta polymerization with the catalyst system VO(O‐neopentyl)2Cl/Al(i‐Bu)3 in toluene at −10°C. Variation of the amounts of propene and ethene leads to products with propene contents between 5 and 30 mol‐% (referring to monomeric unit) in the polymer. These polymers are terpolymers with alternating units of butadiene‐ethene and butadiene‐propene sequences as shown by means of nuclear magnetic resonance investigations. The degree of crystallinity can be varied between 10 and 51 mol‐% by different incorporation of propene into the terpolymer (X‐ray diffraction). The thermal behaviour was characterized using differential scanning calorimetry investigations. Depending on the propene content in the terpolymer the degree of crystallinity significantly influences the parameters of glass transition and the melting process.