bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic studies of the anionic polymerization of methyl methacrylate in tetrahydrofuran with Na+ as counter ion, using monofunctional initiators
Authors: Warzelhan V. , Höcker H. , Schulz G. V. 
Published: April 2003

AbstractA newly designed automatically controlled stirred reactor suitable for kinetic measurements of reactions with half lives ≥2s has been applied to follow the anionic polymerization of methyl methacrylate in THF with Na+ as a counter ion in the presence of an excess of NaB(C6H5)4.As initiators were used: benzylsodium reacted with α‐methylstyrene (I), fluorenylsodium (II), and 9‐methylfluorenylsodium (III). With I the initiation is fast as compared with the polymerization reaction which is first order in monomer concentration. Within the range of −50°C to −100°C an almost unperturbed “living” polymerization is observed. The Arrhenius plot of the rate constants results in a straight line with activation energy Ea = 4,4kcal·mol−1 (= 18kJ·mol−1) and frequency exponent A = 7,0.II and III are slow initiators, II giving rise to side reactions because of the “acidic” proton in 9‐position after initiation, III exhibiting a rate constant of initiation ki = 1l·mol−1·s−1 at −72°C. The termination reaction is becoming increasingly important with increasing temperature and seems to be a unimolecular reaction with Ea,t = 11,5kcal·mol−1 (= 48 kJ·mol−1) and At = 10. Since the basic feature of the reactor is the possibility of drawing samples, polymers from each state of the reaction were available to be investigated also with respect to their tacticity. The monomer addition was shown to follow Bernoullian statistics. A structure of the “living” end being in harmony with the results observed is discussed.
Synthesis of a polycarbonate directly from carbon dioxide, alkali metal diolates and α,ω‐dihalo compounds
Authors: Soga Kazuo , Toshida Yomishi , Hosoda Satoru , Ikeda Sakuji 
Published: April 2003

AbstractA detailed study was carried out on the new synthesis of poly[oxycarbonyloxy‐(1,4‐cyclohexylene)oxycarbonyloxymethylen‐1,4‐phenylenemethylen] (3) from 4‐bromomethylbenzyl bromide (1), dipotassium 1,4‐cyclohexanediolate (2) and carbon dioxide by using a variety of crown ethers as catalysts, which has recently been found by the present authors. Crown ethers having an 18‐member‐ring showed the best catalytic property of the various crown ethers, and the reaction was conducted in various solvents at 40–120°C by using 1,4,7,10,13,16‐hexaoxacyclooctadecane (18‐crown‐6 ether). A maximum yield with the highest molecular weight was obtained from the reaction at 100°C in dioxane solvent. In addition, as result of a kinetic study a plausible mechanism could be proposed. Similar reactions were also carried out with dipotassium and disodium 1,4‐phenylenedimethanolate (6a, b) and dipotassium 4,4′‐isopropylidenediphenolate (7) in place of 2.
Photoredox polymer with incorporated thionine and alkylenepolyamine capable of inducing photopotential
Authors: Kaneko Masao , Sugai Makio , Yamada Akira 
Published: April 2003

AbstractA new type of photoredox polymer with incorporated thionine, (7‐amino‐3H‐phenothiazin‐3‐iminium chloride). (TH) and alkylenepolyamine groups was prepared by the reaction of poly(acrylic acid) with TH and alkylenepolyamines such as ethylenediamine (en), tetraethylenepentamine (3,6,9‐triazaundecane‐I,II‐diamine), (tetraen) and poly(iminoethylene). The photoredox polymers were able to induce photopotential in aqueous solution in the absence of any other redox reagents. The polymers from TH with on and with tetraen induced photopotentials of 180 mV and 167 mV, respectively. The photopotential of the former system was much higher than that of the system, TH/en. The induced photopotential of the polymer systems did not depend so much upon the mole ratio [en]/[TH] of the pendent groups, while the photopotential of the TH/en system was strongly dependent upon [en]/[TH]. Effects of the polymer structure were discussed.
Optimization of solution fractionation of poly(vinyl chloride)
Authors: Klein Joachim , Schriever Eckhard 
Published: April 2003

AbstractThe optimization of solution fractionation of poly(vinyl chloride) (PVC) is described with regard to the variation of several parameters. The best separation efficiency is obtained by a single‐step discontinuous solution fractionation at the following conditions: solvent: cyclohexanone (CHN); nonsolvent: ethylene glycol (EG); temperature: 130°C, isothermal; contact‐time: 2 h per fraction; amount of polymer: 2 mg/g support (glass beads). An essential improvement with respect to the separation of high molecular weight species can be achieved, applying a re‐deposition method of the polymer remaining in the column after half of the fractionation steps. This diminishes the unfavorable formation of a molecular weight‐ and concentration gradient along the column, occurring during fractionation. The optimally controlled single‐stage discontinuous solution fractionation of PVC turns out to be superior to multistage processes. This is attributed to the very critical problem of formation of insoluble microcrystalline aggregates with increasing duration of stay of the polymer in the column. The efficiency of the fractionation technique can be established by the characterization of fractions (center fractions: M̄w/M̄n < 1.1) and by confirmation of small differences in molecular weight distributions, shown by other methods.
Effect of polymer matrix on the cis‐trans isomerization of azobenzene residues in bulk polymers
Authors: Eisenbach Claus D. 
Published: April 2003

AbstractSeveral acrylates and methacrylates were copolymerized with two 4‐aminoazobenzene methacrylic derivatives. The photochemical and thermal cis‐trans isomerization about the azolink was investigated in the bulk polymers. All the copolymers show photochromic behaviour without fading; the photostationary states upon irradiation with UV‐light of the appropriate wavelengths were similar in bulk and in solution. The thermal cis‐trans isomerization follows simple first order kinetics in the rubbery specimens as in solution. Below the glass transition temperature Tg, the isomerization can only be described by two simultaneous first order reactions. Depending on the conditions of irradiation and on the reaction temperature, a portion of the azoaromatic compound reacts anomalously fast. The temperature dependence of the relaxation time of the isomerization reaction in all the polymer films investigated can be represented by a single WLF‐type graph; the corresponding Arrhenius plot is curved above Tg. The findings are interpreted by considering the effects of the free volume and of the chain segmental mobility on the cis‐trans isomerization. A rotational and a translational relaxation mechanism is discussed for the normal and the anomalously fast reaction below Tg.
Surface photografting, 2. Modification of polypropylene film surface by graft polymerization of acrylamide
Authors: Tazuke Shigeo , Kimura Hitoshi 
Published: April 2003

AbstractThe hydrophobic surface of oriented poly(propylene) film (OPP) was modified to a hydrophilic one by a novel photo‐grafting procedure using acrylamide (AM) as monomer. A deoxygenated acetone solution containing AM and benzophenone (BP) or other sensitizers was brought into contact with OPP film and the reaction system was photoirradiated from the other side of the polymer film. Within a few minutes, surface photo‐grafting resulted. The influences of solvent, sensitizer, and additives revealed that the graft polymerization was initiated by hydrogen abstraction from the polymer surface by the triplet excited state of the sensitizer. IR Spectroscopy as well as ESCA measurements confirmed that the graft polymerization occurred on the film surface. The wettability of the grafted OPP film is discussed and correlated with the relative amount of surface grafting. The contact angle of untreated OPP film to water (101°) decreased to ≈40° after surface photografting. The drastic change of surface properties makes the practical application of the present technique feasible.
Dilute solution behavior of poly(vinylidene fluoride). Intrinsic viscosity and light scattering studies
Authors: Ali Sabz , Raina Autar K. 
Published: April 2003

AbstractLight scattering and viscosity measurements of poly(vinylidene fluoride), (PVF2), were made in three solvents; namely, N,N‐dimethylacetamide (DMA), N,N‐dimethylformamide (DMF), and N‐methyl‐2‐pyrrolidone (NMP). The following relations between the intrinsic viscosity, [η], (in deciliters per gram) and the weight‐average‐molecular weight, M̄w, were obtained: [η] = 17,8·10−6 M̄(in DMA at 125°C), [η] = 31,7·10−6 M̄ (in DMF at 125°C) and [η] = 48,8·10−6 M̄ (NMP at 125°C). Treatment of the data by the method of Inagaki et al. indicates that the steric factor, σ, is 1,89, 1,65 and 1,60 in DMA, DMF, and NMP respectively. It is found that the root‐mean‐square radius of gyration of the chain measured by light scattering is in good agreement with the root‐mean‐square radius of gyration of the chain calculated by using the viscosity theory of Inagaki et al. The relations between the root‐mean‐square radius of gyration of the chain in the three solvents and the molecular weight obtained were as follows: 〈S̄2〉 = 2,95·10−1 M̄ (in DMA); 〈S̄2〉 = 8,13·10−2 M̄ (in DMF) and 〈S̄2〉 = 2,82·10−1 M̄ (in NMP). From the estimation of the second viral coefficient, A2, and the values of B (cf. Eq. (6)) obtained from viscosity data, it is concluded that the polymer chains are more extended in DMA than in DMF and NMP.
Copolymerization of 1‐vinylindol with maleic anhydride
Authors: Priola Aldo , Gatti Giuseppe , Santi Giuliano , Cesca Sebastiano 
Published: April 2003

AbstractThe formation of a charge‐transfer complex between 1‐vinylindole (1a) and maleic anhydride (MA) was detected by 1H NMR analysis, and the corresponding Keq was measured (Keq=0,251 mol in CDCl3 at 25°C). It could be shown that this complex can be involved both in the initiation and propagation steps of the 1a‐MA copolymerization by carrying out spontaneous copolymerization experiments and studying the influence of the feed composition on the conversion and [η] of the copolymer. The structure of the 1a‐MA copolymer, investigated by 13C NMR spectroscopy, was found to be complicated due to the formation of indoline rings along the chains by an attack of the propagating MA radical at position 2 in the indole ring. As a consequence an excess of MA, with respect to a 1:1 mole ratio of monomer feed, was usually found in the copolymer. The mechanism of the cyclization reaction was clarified by copolymerizing MA with 2‐methyl‐1‐vinylindole (1b), 3‐methyl‐1‐vinylindole (1c), or 2,3‐dimethyl‐1‐vinylindole (1d). An alternating copolymer with MA (mole ratio 1:1 of monomeric units), without irregularities, was obtained only by employing 1d as a comonomer.
Telechelic oligomers, 4. Synthesis of telechelic oligobutadienes by rh‐catalysis
Authors: Arlt Klaus , Heitz Walter 
Published: April 2003

AbstractPolymerisation of butadiene using different Rh‐compounds, specially Rh(NO3)3, in allyl alcohol results in oligobutadienes with carbonyl functionality of 1 and hydroxyl functionality between 0—1. Under proper conditions telechelics are formed. Catalysis by Rh(NO3)3 can be accelerated by the addition of alcoholate or phosphine. The oligomers have exclusively 1,4‐trans‐structure. The combined use of alcoholate and triphenylphosphine results in oligobutadienes with 40% 1,4‐cis‐, 35% 1,4‐trans‐ and 25% 1,2 structure. Determination of the structure of isolated oligomers shows that both functional groups are incorporated by insertion of a complete allyl alcohol unit. According to the frequently found endgroup CH2C(CH2OH) … the incorporation of the hydroxyl group in the termination reaction by β‐hydride transfer is most likely. The carbonyl functionality is formed in the initiation step by hydride transfer from allyl alcohol to Rh. Analogous use of allyl chloride or allyl bromide results in telechelic oligobutadienes containing two halogens per molecule. but the structure of isolated oligomers shows that only one allyl halogenide unit is incorporated. The second terminal halogen is fixed to a butadiene unit. Again the characteristic group CH2C(CH2Cl)—… is found, suggesting a termination by β‐hydride transfer.
Polymerization of lactams, 29. On the initial stage of the activated anionic polymerization of 2‐pyrrolidone
Authors: Roda Jan , Kučera Otakar , KrálíčEk Jaroslav 
Published: April 2003

AbstractThe activated anionic polymerization of 2‐pyrrolidone in the initial stage was studied at 30–70°C in the range of 1–60 min. Potassium tert‐butoxide and N‐benzoyl‐2‐pyrrolidone were used as initiator and activator, respectively. It can be seen from the polymerization process that side reactions occur parallel to the fast propagation reaction.
Préparation et étude des propriétés chiroptiques de poly(tert‐butyloxiranne)s optiquement actifs
Authors: Sepulchre Maurice , Khalil Ahmed , Spassky Nicolas , Vert Michel 
Published: April 2003

AbstractOptically active poly(tert‐butyloxirane)s of various molecular weights were prepared by polymerization of R(–)‐tert‐butyloxirane with different initiators or by stereoelective polymerization of the racemic monomer. Using identical conditions of polymerization (initiator, temperature etc.) it was found that the pure enantiomer polymerizes much faster than the racemic monomer. The chiroptical properties of the obtained polymers showed similarities in behaviour with those of a synthetized linear model molecule representative for a monomeric unit of the polymer. The enhanced optical activities of low molecular weight polymers were correlated with the presence of chelated hydroxylic end‐groups.
15N NMR spectroscopy 14. Neighboring residue effects in glycine‐containing polypeptides
Authors: Kricheldorf Hans R. , Hull William E. 
Published: April 2003

AbstractThe sequence polypeptides (Ala*‐Ala‐Gly)n, (Ala‐Gly*‐Gly)n, (Leu‐Gly‐Gly)n, (Val‐Gly‐Gly)n, and (Pro‐Gly‐Gly)n were synthesized by known methods, and their natural abundance 15N NMR spectra were measured in trifluoroacetic acid. These spectra were compared with those of other previously described sequence polypeptides and with the corresponding homopolypeptides. The spectra of all sequence polypeptides exhibit neighboring residue effects, so that glycine nitrogen atoms acylated by other χ‐(or ω‐)amino acids have chemical shifts different from that of the Gly‐Gly bond. These neighboring residue effects cannot be summarized or explained by simple rules; however, they are useful for the characterization of copolypeptides. Such an application was tested in the case of four sequence polypeptides consisting of isomeric sequences of identical monomeric units. All isomeric sequences can be distinguished from each other, and the observed shift effects could be related to the neighboring residue effects of other copolypeptides.
Synthese und halbleitereigenschaften von hemiporphyrazinartigen polymeren mit tetrathiafulvalen‐einheiten
Authors: Koßmehl Gerhard , Rohde Michael 
Published: April 2003

AbstractHemiporphyrazine type macroheterocycles with 2,2′‐bi‐1,3‐dithiolylidene (tetrathiafulvalene) units in the polymeric chains (3a–e) were obtained by reaction of 2,2′‐bi‐1,3‐dithiolylidenetetracarbonitrile (tetracyanotetrathiafulvalene) (1) with several diamines (2a–e). The black polymers were characterized by elemental analyses and IR spectra. Thermoanalytic measurements showed that decomposition starts without melting at temperatures > 300°C. The polymers were found to be polymeric organic semiconductors with activation energies of 0,6–1,4eV and electrical conductivities in the range from 10−14 to 10−10Ω−1.cm−1. In the case of the polymers 3a and 3b it was possible to obtain metal complexes (4a–b) by substituting the two hydrogen atoms inside the macroheterocyclic rings. Depending on the metal atoms the electrical conductivities were enhanced up to two orders of magnitude.
Polymerization of α,α‐disubstituted β‐propiolactones and lactams, 12. Properties and crystalline structure of poly(β‐propiolactam)s
Authors: Eisenbach Claus D. , Lenz Robert W. , Duval Michel , Marchessault Robert H. 
Published: April 2003

AbstractA series of α,α‐disubstituted β‐propiolactams (substituted nylon 3 polymers) was prepared from non‐optically active lactams. Their thermal characteristics, densities, and x‐ray fiber diffraction patterns were recorded. One of the α‐substituents was always a methyl group while the other was either CH3, C2H5, n‐C3H7, or n‐C4H9. The melting point for the dimethyl substituted polymer was 268°C; the others were respectively 76, 74, and 72°C. X‐ray fiber diffraction data on all four samples yielded the same fiber repeat of ≈8,4 Å. A minimum energy based conformational analysis for the α,α‐dimethyl derivative indicates that two conformations correspond to this repeat, each of which is a 21 helix.
Crystallization of poly(L‐proline) in the course of polymerization
Authors: Kim Kea Yong , Kōmoto Tadashi , Kawai Tohru 
Published: April 2003

AbstractThe heterogeneous polymerization of L‐proline N‐carboxy anhydride was carried out in acetonitrile and benzene, using butylamine as the initiator. Polyproline I was formed in acetonitrile and polyproline II in benzene in the course of the polymerization. The conversion attained 99% and 66% after 1 week‐polymerization in acetonitrile and benzene, resp. Extended chain crystals were obtained by the polymerization in acetonitrile. On the other hand, poly(L‐proline) obtained by the polymerization in benzene gave aggregates into which many growing chain ends were occluded. The differences in the crystallization behaviour during the polymerization between the two different liquids may be due to the conformation of the resultant polymers. Polyproline I exhibits a cross‐section per chain of 0.709 nm2, whereas polyproline II shows only one of 0,386 nm2. The wider the cross‐section per chain the more the growing, active chain ends can react with the monomer, giving rise to a higher conversion. In contrast with the case of crystallization of such α‐helical chains as poly(L‐alanine) during polymerization, hexagonal lamellar crystals were formed.
Interferenzmikroskopische charakterisierung von faserstrukturen, 4. Zusammenhänge zwischen der farbstoffdiffusion und der faserstruktur beim färben von polyethylenterephthalat‐fasern mit dispersionsfarbstoffen
Authors: Kühnle Gerhard , Schollmeyer Eckhard , Herlinger Heinz 
Published: April 2003

AbstractConcentration distributions of dyestuffs C. I. Disperse Red 60 and C. I. Disperse Blue 139 in microtomic cuttings of fibers of poly(ethylene terephthalate), (poly(oxyethyleneoxyterephthaloyl)) are discussed. An interpretation of the results in relation to order and orientation along the fiber radius by interferometric investigations gives informations about the diffusion process. It is shown, that the diffusion of dyestuffs in high polymers depends—in a complicated way—on fiber structure (as a function of the diffusion path), fiber history, and experimental conditions: C. I. Disperse Red 60 shows a lower diffusion rate at higher radial orientations, whereas the diffusion rate of C. I. Disperse Blue 139 does not depend on the radial dependence of these structure parameters.
Sequential homogeneity of copolymers
Authors: Georgiev George Stefanov 
Published: April 2003

AbstractUsing the finite Markov chains, a method for deriving the relations about the sequential homogeneity indexes for s‐component (s ≥ 2) copolymers is developed. The sequential homogeneity index for binary copolymers as proposed by Tosi and Catinella is proved to be a particular case of the sequential homogeneity index for s‐component copolymers as derived in the present paper. Moreover a method for determination of average lengths and composition of sequences, situated among every two arbitrarily chosen monomeric units is proposed. The sequential homogeneity indexes, the lengths and composition of the above‐mentioned sequences for ternary copolymers of styrene (M1), methyl methacrylate (M2) and acrylonitrile (M3) and quaternary copolymers of styrene (M1), methyl methacrylate (M2), acrylonitrile (M3) and vinylidene chloride (M4) are calculated as an illustration of the method developed.
Mechanism of the NCA polymerization 7. The primary and secondary amine‐initiated polymerization of β‐amino acid NCAs
Authors: Kricheldorf Hans R. , Mülhaupt Rolf 
Published: April 2003

AbstractThe reaction of β‐alanine N‐carboxyanhydride (β‐Ala NCA) (1) with various primary and secondary amines was investigated at room temperature. Three reaction products were found: poly(β‐alanine), β‐alaninamides, and N′‐substituted β‐ureidopropionic acids. The mole ratio of these reaction products depends on the reaction conditions, above all on the NCA/amine ratio, and on the nucleophilicity/basicity ratio of the amines. All amines with pKa‐values > 8,0, including the amino end‐groups of the growing chains, cause the formation of β‐isocyanatocarboxylate ions by deprotonation of the β‐NCAs, and thus, the formation of β‐ureidocarboxylic acids. If the chain ends are involved, this reaction sequence is a termination step, and it is this termination step which is responsible, for that high polymerization degrees (> 60) are not accessible by a primary or secondary amine‐initiated polymerization of β‐NCAs. The β‐ureidocarboxylic acid end‐groups are detectable in the 13C NMR spectra of the poly(β‐amide)s.
The influence of intermolecular interactions on the polymerization, 3. Radical polymerization of 1‐naphthyl methacrylate and 2‐naphthyl methacrylate in acetone and acetonitrile
Authors: Boudevska Hrissanta , Brutchkov Christo 
Published: April 2003

AbstractPolymerizations of 1‐naphthyl methacrylate and 2‐naphthyl methacrylate in acetone and in acetonitrile were carried out in the presence of 2,2′‐azoisobutyronitrile at 55 and 60°C, respectively. The polymers precipitate during the polymerization. Poly(1‐naphthyl methacrylate)s are partly soluble in common organic solvents. The polymerization medium does not influence noticeably the intrinsic viscosity of the resulting polymers. The tacticity was determined by 1H NMR analysis after conversion of the poly(naphthyl methacrylate)s into poly(methyl methacrylate)s. Poly(naphthyl methacrylate)s obtained in acetone and acetonitrile have a higher content of isotactic triads than those obtained in solvents with low dielectric constants. The observed results correlate with the changes in the 1H NMR spectra of the monomers depending on the dielectric constants of the solvents.
15N NMR spectroscopy, 16. Stereospecificity and racemization in the course of the synthesis of (ε‐Aca‐D,L‐Ala‐D,L‐Ala)n
Authors: Kricheldorf Hans R. , Hull W. E. 
Published: April 2003

AbstractH‐D,L‐Ala‐D,L‐Ala‐OH (3) synthesized from Boc‐D,L‐Ala‐OH and H‐D,L‐Ala‐OMe by means of ethyl 2‐ethoxy‐1,2‐dihydroquinoline‐1‐carboxylate was shown by 15N NMR spectroscopy to be a mixture of the L‐L and D‐D enantiomers. Using this racemic mixture N‐(6‐isothiocyanatohexanoyl)‐D,L‐Ala‐D,L‐Ala‐OH (1a) was synthesized and then polymerized in N,N′‐dimethylformamide at 120°C. The 15N NMR and 13C NMR spectra of the resulting polymer (ε‐Aca‐D,L‐Ala‐D,L‐Ala)n (2) demonstrate that the polymerization involved to a large extent racemization. The 15N NMR spectra taken in various solvents turned out to be ca. 5 times more sensitive to stereoisomerism than 13C NMR spectra. The solvents were found to have a strong influence on the chemical shift and on the line width.