bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron paramagnetic resonance (EPR) and electron and nuclear double resonance (ENDOR) characterization of radicals produced during the photopolymerization of multifunctional (meth)acrylate monomers
Authors: Selli Elena , Oliva Cesare 
Published: April 2003

AbstractThe electron paramagnetic resonance (EPR) spectra obtained from radicals produced during the photopolymerization of multifunctional acrylic and methacrylic monomers have been interpreted by taking into account the EPR line‐broadening due to dynamic exchange between two conformations of the β‐methylene groups and a spin‐spin dipolar interaction between radicals trapped in rigid regions of the polymer. From 1H matrix electron and nuclear double resonance (ENDOR) spectra the distance between the radical center and the surrounding shells of protons can be estimated.
Random and block 2‐alkyl‐2‐oxazolines telechelic macromonomers
Authors: Guinot Philippe , Bryant Lonnie , Chow Tak Yuen , Saegusa Takeo 
Published: April 2003

AbstractRing‐opening polymerization of 2‐methyl‐2‐oxazoline initiated by 2‐(p‐nitrobenzenesulfonato)ethyl methacrylate follows the so‐called “living mechanism”, i.e. fast initiation compared to slow propagation and no chain transfer. Accordingly, methacryl macromonomers having homopolymers, block or random copolymers of 2‐methyl and 2‐pentyl‐2‐oxazoline backbones with narrow molecular weight distribution were obtained. Termination of the propagating species by ion‐exchange or aminolysis with triethylamine yielded hydroxyl and quaternary ammonium terminated macromonomers, respectively.
Poly(oxyethylene)s terminated at both ends with phosphonium ion end groups, 1. Synthesis and characterization
Authors: Kubisa Przemyslaw , Biedroń Tadeusz 
Published: April 2003

AbstractThe series of poly(oxyethylene)s (poly‐EO) with number‐average degrees of polymerization ranging from ≈6 to ≈80, terminated at both ends with phosphonium ion groups, was prepared by conversion of hydroxyl end groups of α‐hydro‐ω‐hydroxypoly(oxyethylene)s into bromide end groups, followed by the reaction with triphenylphosphine. The functionality of the products (diionic poly‐EO) was determined by elemental analysis, 1H and 31P NMR as well as mass spectroscopy (MS). The observation of the signals corresponding to individual oligomers in 31P NMR spectra of short chain (DPn < 10) diionic poly‐EO was explained by intramolecular aggregation of ionic end groups leading to cyclic structures. The measurements of spin lattice relaxation times and the chemical shifts of phosphorus at different conditions (temperature, solvent, concentration) confirmed, that the aggregation of ionic end groups is clearly manifested in the 31P NMR spectra of diionic poly‐EO.
Thermal degradation of ethyleneurea formaldehyde polycondensates
Authors: Camino Giovanni , Luda Maria Paola , Costa Luigi , Guaita Marino 
Published: April 2003

AbstractThe mechanism of thermal degradation of the polymer obtained by polycondensation of ethyleneurea with formaldehyde was studied in detail using several techniques. On heating the polymer undergoes crystallisation at about 175°C. Upon melting (at 355°C) further condensation of ethyleneurea with formaldehyde takes place with elimination of water. This process overlaps with the degradation of the polymer which occurs with formation of a complex mixture of volatile products and of a charred residue. The largest fraction of the volatile products of degradation is a low boiling mixture of ethyleneurea with chain fragments containing NH, N‐methyl and unsaturated structures as end groups. A small fraction of gases such as methane, carbon dioxide, carbon monoxide etc. is also evolved. A degradation mechanism is proposed, which accounts for the experimental results.
Systematic investigations on the reactivity of oxazolinium salts
Authors: Nuyken Oskar , Maier Gerhard , Groß Aurelia , Fischer Herbert 
Published: April 2003

AbstractThe termination reaction of the cationic polymerization of 2‐phenyl‐ and 2‐nonyl‐2‐oxazolines was examined by reacting the corresponding model oxazolinium salts having tosylate and trifluoromethansulfonate counterions with various nucleophiles. The reaction was monitored by 1H NMR spectroscopy. Piperidine and KOH react with the oxazolinium salts very fast and quantitatively. In the case of piperidine, the use of a double molar amount of piperidine is necessary to achieve complete conversion. The addition of piperidine, pyridine, 4‐dimethylaminopyridine and morpholine takes place in position 5 of the oxazolinium ring, whereas water and KOH add in position 2. The rate of the termination reaction depends on the electron density of the nucleophile which can be correlated with the pKa value. With CF3SO as counterion the addition of nucleophiles in position 5 is distinctly faster, whereas the addition of water in position 2 is much slower than with TsO− as counterion. The ring‐opening of the nonyl oxazolinium ion is slower than that of the phenyl oxazolinium ion.
Electroconductivity and viscosity of complexes of poly(vinylpyridines) with alkali metal salts in organic solvents
Authors: Bekturganova Gulmira K. , Dzhumadilov Talkybek K. , Bekturov Esen A. 
Published: April 2003

AbstractThe complexation of poly(4‐vinylpyridine) (1), poly(2‐methyl‐5‐vinylpyridine) (2) and poly(2‐vinylpyridine) (3) with bromides, perchlorates and tetraphenylborates of alkali metals in organic solvents was investigated by means of electroconductivity, viscometry and nuclear magnetic resonance spectroscopy. The influence of the nature of the polymer, the low‐molecular‐weight salt and the solvent, salt and polymer concentration as well as the temperature on complexation was studied. The fraction of cations and that of polymer units bound were determined. The compositions of the complexes were found by means of viscometry. It was established that the mechanism of binding of the polymers with alkali metal salts is of the ion‐dipole type.
Synthesis of polyurethanes from saccharide‐derived diols and diisocyanates and their hydrolyzability
Authors: Wilbullucksanakul Sirinat , Hashimoto Kazuhiko , Okada Masahio 
Published: April 2003

AbstractPolyurethanes with saccharide moieties in their repeating units (8 and 9) were prepared by polyaddition of methyl α‐ and β‐D‐glucofuranosidurono‐6,3‐lactones (3α and 3β, respectively) and 1,4:3,6‐dianhydro‐D‐glucitol (4) with hexamethylene diisocyanate (5a) and methyl (S)‐2,6‐diisocyanatohexanoate (5b), which was derived from L‐lysine, in N,N‐dimethylformamide at 25°C using dibutyltin dilaurate as a catalyst. Their properties were compared with those of the polyurethanes (6 and 7) prepared from D‐glucaro‐1,4:6,3‐dilactone (1) and D‐mannaro‐1,4:6,3‐dilactone (2), respectively, in our previous work. Hydrolyzability of the polyurethanes containing 1, 2, or 3α units in buffer solutions was found to be higher than that of the polyurethanes derived from 3β or 4.
Gas‐phase versus slurry copolymerization of ethylene with 1‐butene over MgCl2‐supported titanium catalysts after prepolymerization
Authors: Wu Qing , Wang Haihua , Lin Shangan 
Published: April 2003

AbstractGas‐phase copolymerizations of ethylene with 1‐butene over MgCl2‐supported titanium catalysts after prepolymerization were studied. The activity of a catalyst treated by ethylene/1‐butene prepolymerization “prep‐cat‐2” for the copolymerization is not affected by the monomer composition in the range of 0–10 mol‐% of 1‐butene, but it is higher than that of the homopolymerization of ethylene with a catalyst treated by ethylene prepolymerization “prep‐cat‐1”. Comparative studies of the polymerizations in the gas‐phase and in slurry reactors showed differences in the rate‐time profiles. The higher activities in the early stage and declining kinetics for the gas‐phase polymerizations can be considered to be due to the higher macroparticle diffusivity and to fast deactivation of the active centres which has been confirmed by the determination of the oxidation state of titanium in the catalyst. Data from determinations of monomer reactivity ratios indicated that the gas‐phase process favours the incorporation of 1‐butene into the polymer chains.
Polymorphism and crystal structure identification in poly(aryl ether ketone ketone)s
Authors: Cheng Stephen Z. D. , Ho Rong‐Ming , Hsiao Benjamin S. , Gardner Kenncorwin H. 
Published: April 2003

AbstractPoly(aryl ether ketone ketone)s (PEKKs) are prepared via a Friedel‐Crafts acylation reaction with diphenyl ether and terephthalic acid (T) and/or isophthalic acid (I). The crystal structure, polymorphism and morphology of three PEKK homopolymers have been investigated using transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X‐ray diffraction (WAXD) experiments. The PEKKs studied consist of either all para‐phenylene linkages [PEKK(T)], one meta‐phenylene linkage [PEKK(I)] or alternating T and I isomers [PEKK(T/I)]. PEKK(T) and PEKK(T/I) show crystalline polymorphism depending upon the crystallization conditions and methods. In PEKK(T) two forms (I and II) can be observed, and their unit cell dimensions and symmetry groups are determined via ED experiments. A possible epitaxial relationship between these two forms is proposed when they coexist. PEKK(I) possesses only one crystal unit cell which belongs to the same category as the form I structure in PEKK(T). The c‐axis dimension of the unit cell has been determined as three phenylenes having a zig‐zag conformation, with the meta‐phenylene lying on the backbone plane. PEKK(T/I) shows a complicated polymorphism. In addition to forms I and II, as in the case of PEKK(T), a possible form III is also observed.
Synthesis and electrochemical behaviour of a polymethacrylate with an azoanthraquinone unit in the side chain
Authors: Leitner Michael Bernhard , Ruhmann Ralf , Springer Jürgen 
Published: April 2003

AbstractThe synthesis of the model compounds 2‐(4‐methoxyphenylazo)anthraquinone (1) and 2‐[4‐(6‐acetoxyhexyloxy)phenylazo]anthraquinone (2), the monomer 2‐[4‐(6‐methacryloyloxyhexyloxy)phenylazo]anthraquinone (3) and the polymethacrylate poly‐3 via radical polymerization of 3 is described. The electrochemical behaviour of poly‐3 is studied by cyclic voltammetry in comparison with 1 and 2. Poly‐3 can be reduced and oxidized reversibly in solution and in thin films in a two‐step redox process. Therefore, poly‐3 is a potential material for a molecular device system using the electrochemical properties.
Amino acid based bioanalogous polymers. Synthesis of novel poly(urethane amide)s based on N,N′‐(trimethylenedioxydicarbonyl)bis(phenylalanine)
Authors: Kartvelishvili Tamara , Kvintradze Akaki , Katsarava Ramaz 
Published: April 2003

AbstractThe feasibility of synthesizing high‐molecular‐weight amino acid based bioanalogous polymers (AABBPs)‐poly(urethane amide)s (PUA) — via polycondensation (PC) of di‐p‐nitrophenyl ester of N,N′‐(trimethylenedioxydicarbonyl)bis(L‐phenylalanine) (3) with diamines or their derivatives under mild conditions in organic solvents was studied for the first time. A regular PUA (ηred = 1,53 dL/g) was obtained by PC of 3 with hexamethylenediamine. A dipeptide (Phe‐Phe) containing regular poly(ester urethane amide) (ηred = 0,58 dL/g) was synthesized by PC of 3 with p‐toluenesulfonic acid salt of bis(L‐phenylalanine) 1,4‐butylene diester. A tripeptide (Phe‐Lys‐Phe) containing PUA (ηred = 0,38 dL/g) with pendent ester groups was prepared via PC of 3 with N,N‐bis(trimethylsilyl)‐L‐lysine methyl ester. These novel AABBPs which may be considered as structural analogs of AB type bioanalogous polymers — conventional poly(amino acids) are of interest in enzymology, immunology, pharmacology, and biotechnology (as materials for biomedical applications).
The synthesis of polymerizable vinyl sugars
Authors: Wulff Günter , Schmid Jürgen , Venhoff Theodor 
Published: April 2003

AbstractIn this feature article we review the synthesis of polymerizable vinyl sugars. Many such syntheses start from isopropylidene‐protected sugars, which still have a free OH‐group. These compounds are then converted to polymerizable monomers by esterification or etherification. Selective reactions at non‐protected sugars, introducing polymerizable groups, can be achieved by enzymatic catalysis. Alternatively, such selective transformations may be accomplished by chemical reaction at the reducing group of the sugar either directly or after transforming the half‐acetal to a more reactive intermediate. Furthermore, results are described on the synthesis of vinyl sugars whose vinyl group is connected with the monosaccharide by a CC bond. Such monomers can be polymerized by radical as well as by anionic initiation. In this case a chemically very stable connection is obtained in the resulting polymers between the sugar moiety and the polymer backbone.
Conductivity, luminescence and vibrational studies of the poly(ethylene glycol) 400 electrolyte based on europium trichloride
Authors: Di Noto Vito , Bettinelli Marco , Furlani Maurizio , Lavina Sandra , Vidali Maurizio 
Published: April 2003

AbstractPoly(ethylene glycol) 400/(EuCl3)x electrolytic complexes with 0 ≤ x ≤ 0.327 were prepared. The ionic conductivity of these systems was investigated, and the data were satisfactorily well fitted by the empirical Vogel‐Tamman‐Fulcher equation. Two different conductivity regions depending on the electrolytic complexes compositions were observed. The conformation of the poly(ethylene glycol) 400 (PEG 400) in the complexes was investigated by FT‐IR and Raman spectroscopies. These investigations suggest that the PEG 400 chains in PEG 400/(EuCl3)x, present a TGT conformation (T = trans, G = gauche). Moreover, by laser luminescence spectroscopy it was also proved that each Eu3+ ion is coordinated by four oxygen atoms of PEG in a distorted C2v site symmetry.
Photoreactive polyarylenevinylenes: Synthesis, characterization and photochemistry
Authors: Mauermann‐Düll Heike , Böhm Arno , Fiesser Gerold , Müllen Klaus 
Published: April 2003

AbstractThe substitution of every second phenylene subunit in the well‐known poly(p‐phenylenevinylene) (PPV) by o,o′‐bridged biphenyl moieties leads to the novel poly(1,4‐phenylenevinylene‐2,2′‐biphenylylenevinylene) (PPVBV, 5) which can be prepared by palladium‐catalyzed aryl‐olefin coupling (Heck reaction). PPVBV possesses a high solubility in common organic solvents and good filmforming capabilities. It exhibits a thermochemical and photochemical reactivity comparable to that of the monomeric model compound 2,2′‐distyrylbiphenyl (3), which undergoes a [2+2]cycloaddition upon heating or irradiation.
Study of the propagation centre in the anionic polymerization of lactams, 1. Spectroscopic and theoretical study of the activated monomer in dimethyl sulfoxide
Authors: Kříž Jaroslav , Stehlíček Jaroslav , Dybal Jiří , Hauer Jan , Schmidt Pavel 
Published: April 2003

AbstractSolutions of Li, Na and K salts of 3,3‐dimethyl‐2‐piperidone and ε‐caprolactam in dimethyl sulfoxide‐d6 were studied by 6Li, 7Li, 23Na, 1H and 13C NMR, Raman spectroscopy and MNDO molecular orbital calculations. Using NMR relaxation, the dynamics and equilibrium states of solvation, dissociation and cation exchange were clarified. At concentrations above, 0,1 mol/L, molecular aggregation to a dimer and possibly higher aggregates has been found.
Study of the propagation centre in the anionic polymerization of lactams, 2. Model study of the interaction between an activated monomer and N‐acyllactam in dimethyl sulfoxide
Authors: Kříž Jaroslav , Stehlíček Jaroslav , Dybal Jiří , Hauer Jan 
Published: April 2003

AbstractInteraction of potassium 3,3‐dimethyl‐2‐piperidone with 1‐benzoyl‐3,3‐dimethyl‐2‐piperidone in DMSO as a model of the complex propagation centre in the anionic polymerization of lactams has been studied by 1H and 13C NMR, infrared spectroscopy, and, for the Li counterion, by MNDO calculations. The reactants were found to form a loose complex which can emerge in various geometries sharing the equivalence and relative motional freedom of both lactam moieties. Types of internal motions in the complex are suggested and their implications for the detailed idea of the propagation mechanism are discussed.
Radicals produced in the photopolymerization of multifunctional monomers, as probes of the polymeric structure
Authors: Selli Elena , Oliva Cesare 
Published: April 2003

AbstractThe EPR spectra of radicals produced during the photoinduced polymerization and cross‐linking of multifunctional acrylic and methacrylic monomers are sensitive to the mobility of the polymeric surroundings. An analysis of the rate of decay of radicals trapped in different environments is reported, with the aim of finding a correlation between the evolution of the EPR spectral shape and the characteristics of the polymeric structure. A dispersive kinetic model was found to be suitable for the interpretation of radical decay results, in terms of a rate parameter (B) and a dispersion parameter (α) which takes into account the disorder of the system. These parameters depend on radical decay temperature and reflect the properties and the mobility of the photopolymerized networks, in relation to the monomer structure and to photopolymerization conditions, such as irradiation time and photoinitiator content.
Copolymerization of propene and higher α‐olefins with the metallocene catalyst Et[Ind]2HfCl2/methylaluminoxane
Authors: Arnold Manfred , Henschke Olaf , Knorr Jana 
Published: April 2003

AbstractCopolymerizations of propene with higher α‐olefins including 1‐butene, 1‐hexene, 1‐octene, 1‐dodecene and 1‐hexadecene were carried out with an isospecific metallocene catalyst (Et[Ind]2HfCl2/methylaluminoxane) at 30°C in toluene. 13C NMR analysis showed that all products obtained are random copolymers (r1 · r2 ∼ 1). The reactivity of the higher α‐olefins in the copolymerization is surprisingly high and decreases only slightly with increasing length of the olefin. The incorporation rates of the comonomers in this study were found to be much higher than those obtained by the use of heterogeneous Ziegler‐Natta catalysts. Hence, copolymers with every desired composition and α‐olefin homopolymers can be prepared. The molecular weight of the copolymers is reduced with rising comonomer content. Melting points and glass transition temperatures studied by means of differential scanning calorimetry show a decrease with rising comonomer content and increasing length of the α‐olefin.
Photochromism of anils having a long alkyl side chain in polymer matrices
Authors: Yin Ming , Kuwabara Tetsuo , Haramoto Yuichiro , Nanasawa Masato 
Published: April 2003

AbstractThe photochromism of 4‐alkyl‐N‐(4‐methoxysalicylidene)anilines was investigated in amorphous polymer matrices. The absorbance change after irradiation increased with extending the length of the alkyl chain due to the hindrance of conformational change and the stabilization of the colored species by the alkyl side chain. The thermal decay reaction deviates from the first‐order kinetics. The deviation depends not only on the heterogeneity of the polymer matrix but also on the length of the alkyl chain of the anils.
Effect of crown ether on the ionic conductivity of the poly(ethylene oxide)/lithium salt electrolyte
Authors: Mehta Mary Anne , Kaeriyama Kyoji 
Published: April 2003

AbstractThe addition of small amounts of crown ethers was observed to enhance the conductivity of the system PEO20LiCF3SO3 (PEO: poly(ethylene oxide)). Optimum conductivity enhancement was observed for the system PEO20LiCF3SO3(crown ether)0.003 when 12‐crown‐4 and benzo‐12‐crown‐4 were used and for the system PEO20LiCF3SO3(crown ether)0.03 containing the corresponding azacrown ether (cyclen) and thiacrown ether. Maximum conductivity enhancement was observed for PEO20LiCF3SO3(cyclen)0.03. Over the temperature range studied, the conductivity of this system was 1–1.5 orders of magnitude higher than for the system PEO20LiCF3SO3.The Li+ diffusion coefficient for the system PEO20LiCF3SO3(cyclen)0.03 was determined to be 1.5 · 10−9 cm2 · s−1 at 90°C. This is lower than the values obtained by other workers in the absence of cyclen using pulsed field gradient NMR techniques. The presence of cyclen thus appeared to have the effect of suppressing the Li+ motion. The presence of small quantities of 18‐crown‐6 in PEO8Ca(CF3SO3)2 electrolytes was also associated with a conductivity enhancement. This showed that this effect was not limited to systems containing monovalent cations.
Synthesis, characterization and polymerization of dendrimers with methacrylic end groups
Authors: Moszner Norbert , Völkel Thomas , Rheinberger Volker 
Published: April 2003

AbstractDendritic methacrylic crosslinking agents were synthesized by modification of amino functional poly(propyleneimine) dendrimers. On the basis of model reactions, several experimental methods for the introduction of methacrylate end groups were evaluated. In case of the Michael reaction of 2‐(acryloyloxy)ethyl methacrylate (1) the amino‐end groups of the dendrimers of the second, the fourth or the fifth generation add exclusively onto the acrylic double bonds of 1 forming methacrylic end groups in the modified dendrimers. The quantitative and uniform conversion could be proved by NMR spectroscopy. Analogous dendrimer modifications were carried out with mixtures of 1 and other acrylates. The dendrimeric methacrylates of different generations were polymerized in solution and bulk at 80°C with 2.2′‐azoisobutyronitrile as initiator. The polymerization enthalpy of the dendrimeric methacrylates was determined by differential scanning calorimetry and shows that the polymerization of approximately every double bond takes place. The polymerization of methacrylic dendrimers yields crosslinked polymers with glass transition temperatures near or below room temperature.
NMR spectra of polyimides: Interpretation and local chain motion study
Authors: Wang Jianli , Zhang Jianguo , Li Binyao , Ding Mengxian , Feng Zhiliu 
Published: April 2003

AbstractThree kinds of high‐performance polyimides 1 (poly(ketone‐imide) PKI), 2 (poly(ether‐imide) PEI) and 3 (poly(oxy‐imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two‐dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon‐13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main‐chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.