bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface studies on copolymers having pendant monosaccharides
Authors: Nakamae Katsuhiko , Miyata Takashi , Ootsuki Norihito , Okumura Masakazu , Kinomura Keisuke 
Published: April 2003

AbstractCopolymers having pendant monosaccharide groups were synthesized by copolymerizing 2‐(glucosyloxy)ethyl methacrylate (GEMA, 1), with methyl methacrylate (MMA) or styrene (St). The surface characteristics of the copolymer films were investigated by means of contact angle measurements, X‐ray photoelectron spectroscopy (XPS), and protein adsorption. The surface free energy of the GEMA/St copolymer films was constant in the range of a GEMA content from 10 mol‐% to 60 mol‐%. Insertion of GEMA of over 60 mol‐%, however, caused an increase of the surface free energy of the copolymer films. The surface composition determined by means of XPS supported the result from surface free energy measurements. There was a significant difference between the GEMA/St and GEMA/MMA copolymer films in the effect of the GEMA content on the surface characteristics of the films. The differences could be explained on the basis of the sequence of monomeric units in each copolymer. Immersing the copolymer films in hot water made the copolymer surface more hydrophilic. This is because each component migrates to the surface or the bulk in order to minimize the surface free energy of the copolymer films. The introduction of GEMA to the copolymer suppressed fibrinogen adsorption onto the copolymer films.
Assignment of finely resolved 13C NMR spectra of poly(methyl methacrylate), 2. Methylene carbon
Authors: Kawamura Tokiji , Toshima Naoki , Matsuzaki Kei 
Published: April 2003

AbstractThe 13C methylene carbon absorptions of poly(methyl methacrylate) with a random structure were assigned in terms of tetrad sequences using the 2D COSY (1H‐13C) NMR spectrum and by comparison with the absorptions of isotactic‐rich and syndiotactic‐rich poly(methyl methacrylate)s. The rrr, rmr and mmr tetrads were further assigned in terms of hexad sequences.
Influence of spacer length between interacting group and polymer backbone on the glass transition temperature of electron‐donor/electron‐acceptor blends
Authors: Bolsinger Michael , Schneider Hans Adam 
Published: April 2003

AbstractCharge transfer Interaction (CT‐I) between electron‐donor/electron‐acceptor groups contributes to an enhancement of the miscibility in polymer blends. Typical of polymer blends with charge transfer interaction is an increase of the glass transition temperature, suggesting a decrease of the free volume during mixing of the blend components. Both, “zip”‐like orientation effects of the CT‐I onto the polymer backbones and temporary crosslink formation may contribute to the reduction of the free volume. The effect generally decreases with increasing spacer length between the interacting groups and the polymer backbone, although an increased probability of electron‐donor/electron acceptor (EDA) association may be accepted due to the enhanced mobility of the interacting endgroups. Thus the increased probability of EDA association is overcome both by the increased mobility of the temporary crosslinks and by the decrease of the induced orientation effect on the polymer backbone of the CT‐I due to the enhanced decoupling of the mobile interacting groups from the less mobile polymer backbone. Because of the possibility of D/2A association of the carbazolyl end‐group the effect is more complicated. For the same overall spacer length of the interacting EDA groups the deviation from the additivity of the glass transition temperatures of the polymer blend components is always the larger the longer the donor‐spacer.
Synthesis and properties of amphiphilic “dumbbell”‐shaped grafted block copolymers, 1. Anionic synthesis via a polyfunctional initiator
Authors: Bayer Uwe , Stadler Reimund 
Published: April 2003

AbstractTwo poly(ethylene oxide) stars linked by a long polystyrene chain represent a novel amphiphilic architecture (dumbbell), which is available by anionic grafting of ethylene oxide from a hydroxylated polybutadiene‐block‐polystyrene‐block‐polybutadiene triblock copolymer. The short butadiene end‐blocks (DPB = 36) of a BSB triblock copolymer with a long styrene middle block (DPS = 650) was first modified by hydroboration and oxidation. A multifunctional alkoxide initiator is thus prepared by titration of the hydroxyl groups of the “polybutadiene” end‐block with cumylpotassium. Gelation and precipitation of the polyfunctional initiator in THF could be avoided by complexing the cation (K+) with a suitable cryptand (Kryptofix[2.2.2]TM). This multifunctional macroinitiator was used to polymerize ethylene oxide. Dumbbell‐shaped molecules with various number and length of PEO branches were synthesized. Some first results about their solution properties are presented and discussed based on viscosity and light scattering measurements.
Spectroscopic study of 1‐decene oligomers obtained with AlCl3 as catalyst
Authors: Doskočilová Danica , Pecka Jan , Dybal Jiří , Kříž Jaroslav , Mikeš František 
Published: April 2003

AbstractThe product of 1‐decene oligomerization with AlCl3 as catalyst was fractionated by vacuum distillation, with the highest fraction consisting predominantly of the hexamer. The structure of the fractions was characterized by 1H and 13C NMR and Raman spectroscopy. The oligomers contain predominantly long branches (7 carbons and longer) and always one double bond per molecule, with strong predominance of tri‐ and tetra‐substituted types. The minority structures are analyzed, and the polymerization and isomerization mechanisms are discussed.
Characterization of the network structure in amine‐cured epoxy resins by selective degradation
Authors: Stutz Herbert , Mäder Hans‐Joachim , Simak Petr , Voelkel Rüdiger 
Published: April 2003

AbstractA special model system based on a diglycidylester (1) and 4,4′‐diaminodiphenylmethane (2) was used to characterize the network structure of epoxy resins. Networks with cure degrees of 0,72 to 0,82 were prepared. These networks could be cleaved by hydrolysis after curing, and the network functionality and its distribution were characterized by chromatography. The results are in good agreement with predictions from branching theory, no indication of a deviation from statistics could be found.
Compatibilizing effect of a thermotropic liquid‐crystalline compatibilizer on liquid‐crystalline polycarbonate/poly(p‐phenylene oxide) blends
Authors: Kobayashi Takanori , Sato Moriyuki , Takeno Noboru , Mukaida Ken‐ichi 
Published: April 2003

AbstractThe compatibilizing effect of a thermotropic block‐graft copolymer (LCBG) as a compatibilizer on thermotropic liquid‐crystalline (LC) polycarbonate (LCPC)/poly(p‐phenylene oxide) (PPO) blends was studied. Compatibility, morphology and mechanical properties of the blend systems were investigated by differential scanning calorimetry (DSC), thermal mechanical analysis (TMA) and scanning electron microscopy (SEM). The blend without the compatibilizer formed thermotropic LC phases, based on LCPC domains, and had a phase‐separated structure. The LC temperature ranges of the blends with LCBG were wider than that of the blend without the compatibilizer. DSC, SEM and TMA data showed that in the blends containing the compatibilizer the compatibility and the viscoelasticity were improved, because LCBG segments penetrate into both the PPO matrices and the LCPC domains in the blends. These results suggest that LCBG acts as a good compatibilizer for blends.
Use of different alkoxysilanes as external donors in MgCl2‐supported Ziegler‐Natta catalysts to obtain propene/1‐butene copolymers with different microstructure
Authors: Sacchi Maria Carmela , Fan Zhi‐Qiang , Forlini Fabrizio , Tritto Incoronata , Locatelli Paolo 
Published: April 2003

AbstractThe effects of different alkoxysilane donors (Ph(EtO)3Si, Me(EtO)3Si and Ph2(EtO)2Si) have been compared in propene/1‐butene copolymerization with MgCl2‐supported Ziegler‐Natta catalysts. The copolymers obtained were fractionated and the fractions characterized by 13C NMR analysis. The influence of the different alkoxysilanes on the yield, the fraction distribution and the composition, the reactivity ratios and the number‐average sequence lengths of all the fractions were analyzed. The results obtained show that it is possible to vary the characteristics of propene/1‐butene copolymers by varying the bulkiness of the hydrocarbon substituent and/or the number of the alkoxy groups of the silane donor. It was also possible to correlate the effect of the silane donor on the homopolymerization stereochemistry and on the characteristics of the copolymers.
Preparation and properties of “thread‐through” copolymers of polyethylene with polyisoprene
Authors: Zhang Xuequan , Li Weidong , Huang Baotong 
Published: April 2003

AbstractGraft copolymers of polyethylene (PE) with polyisoprene (PI) were synthesized through polymerization of ethylene in toluene solution of PI (cis‐1,4‐:95%; 3,4‐:5%) using a homogeneous V(acac)3/Et3Al2Cl3 catalyst. Copolymers are formed when the growing polyethylene chains thread through the external and/or internal double bonds of the dissolved polyisoprene, giving copolymers with proliferating chain structures. Compared to the corresponding PI/PE blends, “thread through” copolymers had lower crystallization temperature, much lower crystallinity, and smaller microcrystallite sizes, indicating that the PI component hampered the crystallization of PE due to the chemical bonding between them. This chemical bonding between PE and PI was substantiated by a 11°C higher Tg of PI, 13°C lower α‐relaxation and the presence of a β‐relaxation, as compared to the corresponding PI/PE blends. Moreover, the PI/PE “thread through” copolymer with higher PI content had lamellar phase morphology, whereas the PI/PE blends with similar composition showed quite broadly dispersed PI domains. Much better mechanical properties of the “thread through” copolymers than of the PI/PE blends indicate that there is a great difference in their chain structures.
Monofunctional polydimethylsiloxane oligomers for graft copolymerisation
Authors: Holohan Aidan T. , George Maurice H. , Barrie James A. , Parker David G. 
Published: April 2003

AbstractWell defined, narrow molecular weight distribution polydimethylsiloxane (PDMS) oligomers containing single, terminal, reactive end groups were synthesised by the anionic polymerisation of hexamethylcyclotrisiloxane (D3). A variety of functionalities were obtained by termination with an appropriate silyl chloride end blocker, e.g. styryl, allyl, silyl chloride, silane, hexenyl etc. Certain monomeric end blockers were also synthesised where necessary. The resulting oligomers were subjected to detailed characterisation using 1H NMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and IR spectroscopy.
Study of the propagation centre in the anionic polymerization of acrylic monomers, 1. Spectroscopic study of methyl 2‐lithioisobutyrate, an initiator for the anionic polymerization of acrylic monomers
Authors: Kříž Jaroslav , Dybal Jiří , Vlček Petr , Janata Miroslav 
Published: April 2003

AbstractAs the simplest model for the propagation centre in the anionic polymerization of methyl methacrylate, the solution of methyl 2‐lithioisobutyrate (1) in tetrahydrofuran was studied by means of 1H, 6Li, 7Li and 13C nuclear magnetic resonance (NMR), and Raman spectroscopy at various concentrations and temperatures. A system of equilibria of differently solvated dimeric, tetrameric and two isomeric trimeric aggregates was found and their thermodynamic constants were established. On the basis of the analysis of NMR chemical shifts, heteronuclear nuclear Overhauser effect correlation spectroscopy (NOESY) spectra and relaxation data, structures of the aggregates are suggested. The kinetics of the exchange between the aggregates and the lifetime of individual aggregates was established. The results suggest that the aggregation can interfere with initiation in the early steps of anionic polymerization of acrylics.
A master curve for tensile properties of thermoplastics
Authors: Elias Hans‐G. 
Published: April 2003

AbstractUltimate mechanical properties of polymers can be characterized by a dimensionless Hooke number He ≡ σb/(Eϵb), where σb is the ultimate tensile strength, E the tensile modulus, and ϵb the elongation at break. Hooke numbers are found to be a smooth function of ultimate elongations, independent of the chemical and physical structure of common thermoplastics. This master curve for fracture strengths and elongations can be described by He = [1 + (ϵb/ϵcrit)ab]−1/b with empirically found parameters ϵcrit = 0,0168, a = 0,918, and b ≈ 4. The decrease of He with increasing ϵb at ϵb > ϵcrit reflects the shear flow on deformation. Hooke numbers depend on entanglement densities ve according to He = 1,285·1036 (ve/cm−3)−1,846 for ve > 3,65·1019 cm−3. A correction for additional segment orientation during tensile testing brings the exponent to −1,846/0,918 = −2,01; i. e., a dependence of Hooke numbers on the reciprocal square of entanglement densities.
Entanglement of poly(ethylene terephthalate): A reevaluation
Authors: Elias Hans‐G. 
Published: April 2003

AbstractThe mass‐average based critical molar mass Mc = 9200 g·mol−1 and the entanglement density ve = 17,0·1019 cm−3 of poly(ethylene terephthalate) PETP were calculated for 280°C from literature data on PETP melts, using appropriate corrections for polymolecularities.
Elastomers based on poly(hexafluoropropylene oxide) crosslinked via triazine groups
Authors: Ding Ji‐Feng , Khan A. Rasheed , Proudmore Martin , Mobbs Richard H. , Heatley Frank , Price Colin , Booth Colin 
Published: April 2003

AbstractPoly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end‐linking via triazine groups. The networks were characterised by NMR spectroscopy and by determination of the number of network chains from the shear modulus, and were shown to contain both triazine crosslinks and imidoylamidine links. The mechanical, thermal and chemical properties of the networks were investigated by a range of techniques. A network formed from fully difunctional poly(HFPO) had excellent elastomeric properties above −15°C, and was thermally stable up to 270°C.
Assignment of 13C nuclear magnetic resonance spectra of poly(methacrylonitrile)
Authors: Kawamura Tokiji , Toshima Naoki , Matsuzaki Kei 
Published: April 2003

Abstract13C Nuclear magnetic resonance (NMR) spectra of atactic and syndiotactic‐rich poly(methacrylonitrile) (PMAN) were determined. In addition, 2D (1H‐13C COSY)COSY = COrrelated SpectroscopY.
NMR spectra of α‐methyl and methylene regions of atactic PMAN were measured. Values of tetrads and pentads were calculated from triads obtained from α‐methyl carbon absorptions of the samples. By comparing calculated values with the observed ones, and by taking 2D NMR spectra into consideration, both α‐methyl carbon and proton absorptions were assigned by pentads, and methylene carbon absorptions by tetrads (partly by hexads).
Polymerization of propene with highly isospecific. SiO2‐supported zirconocene catalysts activated with common alkylaluminiums
Authors: Soga Kazuo , Kim Hyun Joon , Shiono Takeshi 
Published: April 2003

AbstractSeveral types of SiO2‐supported metallocene catalysts were prepared using chemically modified silica gel. Polymerization of propene was conducted with these catalysts combined with methylaluminoxane (MAO) or ordinary alkylaluminiums. Highly isotactic poly(propylene) with high molecular weight was obtained by the catalysts whose zirconocene ligands were chemically immobilized on SiO2. The preparative methods of these catalysts and the results of propene polymerization, together with the analytical data of produced polymers, are reported in some detail.
Raman spectroscopic study of hydrogen bonding of poly(N‐vinyl‐2‐pyrrolidone) in heavy water and dimethyl sulfoxide
Authors: Tanaka Naoki , Ito Kensaku , Kitano Hiromi 
Published: April 2003

AbstractThe Raman spectra of solutions of poly(N‐vinyl‐2‐pyrrolidone) (PVP; M̄w = 1 000, 10 000, 40 000 and 360 000) in D2O and dimethyl sulfoxide (DMSO) were measured at various concentrations. PVP is hydrated by D2O in a manner different from N‐ethyl‐2‐pyrrolidone (NEP) and N‐methyl‐2‐pyrrolidone (NMP), monomer analogues of PVP. The self‐association of DMSO molecules in the solution of PVP was found to be different from that in the solution of NMP by using difference spectroscopy. These phenomena were attributed to a net‐like structure of concentrated solutions of PVP.
Magnesium chloride‐supported catalysts for Ziegler‐Natta propene polymerization: Ethyl formate as internal base
Authors: Noto Vito Di , Zannetti Roberto , Viviani Maria , Cecchin Giuliano 
Published: April 2003

AbstractMgCl2‐supports for Ziegler‐Natta polymerization processes were prepared by an activation method based on the thermal removal of ethyl formate (EF) from adducts between EF and MgCl2. The various steps of activation were investigated by X‐ray diffraction (XRD) and infrared spectroscopy (FT‐IR) of MgCl2(EF)x adducts having 0 ≤ x ≤ 2. A subsequent titanation process of the above supports gives rise to a decrease of the EF content in the obtained products. By XRD on polycrystalline powders, the effects were investigated of the EF concentration in the titanated adducts used in Ziegler‐Natta polymerization processes and having a composition [MgCl2(EF)k(TiCl4)m]. Moreover, the relationships were investigated between yield and stereospecificity in the propene polymerization tests; a maximum of isospecificity was observed for the mole ratios Ti/Mg ≈ 0,065, EF/Mg ≈ 0,47 and Ti/EF ≈ 0,15. It was also demonstrated that a progressive removal of EF from the adducts gives rise to supports showing a different structural disorder in dependence on the removal time.
Polymerization of 2,2‐dimethyltrimethylene carbonate with tri‐sec‐butoxyaluminium; a kinetic study
Authors: Wurm Birgid , Keul Helmut , Höcker Hartwig 
Published: April 2003

AbstractThe polymerization of 2,2‐dimethyltrimethylene carbonate (DTC, 1) with tri‐sec‐butoxyaluminium (Al(O‐sec‐Bu)3) proceeds with suppression of macrocyclics formation. The propagation of the polymerization proceeds pseudoanionically via insertion. Within the scope of a kinetic treatment, the time‐conversion relationship was determined for the polymerization of DTC with Al(O‐sec‐Bu)3 as initiator and toluene as solvent. For a polymerization temperature between 15°C and 74°C, the apparent rate constant was found to be between 0,1 and 1,0 L · mol−1 · s−1. Using the Arrhenius plot the experimental temperature coefficient (20,6 kJ · mol−1) as well as the frequency factor of the polymerization (1,3 · 103 L · mol−1 · s−1) were determined. Investigation of the dependence of the rate of polymerization on the initiator concentration revealed a degree of aggregation of 2 for the active species.
Investigation of the structural changes in high‐speed spun yarns of polyamide 6 by means of WAXS employing synchrotron radiation
Authors: Schmack Gerhilt , Beyreuther Roland , Häußler Liane , Tidick Peter Joachim , Zachmann Hans Gerhard , Koch Michel Henry Jean 
Published: April 2003

AbstractThe melting and recrystallization of yarns of polyamide 6 spun at different take‐up velocities ranging from 3 500 to 5 600 m/min was investigated by means of wide‐angle X‐ray scattering (WAXS) employing synchrotron radiation and by differential scanning calorimetry (DSC). It was shown that the first peak in the double melting peak of the DSC‐curves is caused by the melting of the γ‐crystals. The melting point is increased by approximately 5°C when the take‐up velocity is increased from 3 500 m/min to 5 600 m/min. The addition of calcium stearate to the material has no effect on the thermal stability of the crystals, but seems to have some effect on the crystallization rate.
Fluorination of polymers containing COOH/COOR‐groups with SF4/HF, 2
Authors: Nuyken Oskar , Dannhorn Wolfgang , Obrecht Werner 
Published: April 2003

AbstractCarboxyl‐ and ester groups of low molecular‐weight compounds are selectively and quantitatively converted into trifluoromethyl moieties by reaction with SF4/HF as shown in a previous paper. This reaction is now applied to the polymers poly(acrylic acid), poly(acrylic esters) and poly[(acrylic acid)‐co‐(acrylic ester)]. Poly(acrylic acid) yields gelled products whereas poly(acrylic ester) and the copolymers yield highly fluorinated soluble polymers upon reaction with SF4/HF. Under mild reaction conditions the carbonyl groups in acrylic acid/acrylic ester copolymers are selectively fluorinated. Unter vigorous reaction conditions, acid as well as ester moieties of the copolymers are completely fluorinated. Macroscopic gelation during fluorination is most probably associated with intermolecular ether formation. Molecular weights, NMR spectra and glass transition temperatures of the reaction products are given.
Synthesis, structure‐property relations and lyotropic behavior of perfluoroalkyl‐substituted para‐linked aromatic polyamides
Authors: Hatke Wilfried , Schmidt Hans‐Werner 
Published: April 2003

AbstractA series of perfluoroalkyl‐containing para‐linked aromatic polyamides based on trifluoromethyl‐p‐phenylenediamine and a mixture of trifluoromethyl‐ and pentafluoroethyl‐substituted terephthalic acid have been synthesized. The polyamides were prepared by a low temperature solution polycondensation of aromatic diacyl chlorides with N,N′‐bis(trimethylsilyl)‐substituted aromatic diamines. The influence of these perfluoroalkyl substituents on thermal properties, solubility and lyotropic behavior is discussed. 19F NMR spectroscopy was utilized for molecular weight determination and for further examination of the polymer structure.
Synthesis and dielectric characterization of poly[acrylonitrile‐co‐acrylamide‐co‐(acrylic acid)] terpolymer gels
Authors: Hu David Shiaw‐Guang , Lin Yow‐Shi 
Published: April 2003

AbstractThe acidic hydrolysis of polyacrylonitrile, stabilization and thermal gelation in mixed solvents were sequentially carried out to yield a variety of terpolymer gels made up of 58,5 to 89,4 mol‐% units of acrylonitrile, 10,2 to 39,2 mol‐% acrylamide and 0,4 to 2,3 mol‐% acrylic acid. The posthydrolysis stabilization at temperature below 0°C was shown to induce chemical conversion from acrylonitrile to acrylamide, that is more pronounced for a certain range of initial acrylamide contents than others as evidenced by the kinetic analysis using 1H NMR and base titration. The dielectric relaxation measurements on swollen gels show three relaxation transitions, α, β and γ in decreasing order of temperature, over −150 to 0°C. The β‐transition, due to the segmental motion of the polymer, is the least distinct of the three. The β‐ and γ‐transitions in decreasing order of temperature are associated with the cooperative motion of polar groups with water and glass transition of water, respectively, as judged from the activation energy and temperature of relaxation. The β‐relaxation was shown to be strongly influenced by the type of swelling solvent in the gel, water contents and chemical composition of the gel. Furthermore, the Cole‐Cole plots in the region of the β‐relaxation were constructed to demonstrate the role of morphology in the dielectric behaviour of hydrogels.