bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amino acid based bioanalogous polymers. Novel regular poly(ester urethane)s and poly(ester urea)s based on bis(L‐phenylalanine) α,ω‐alkylene diesters
Authors: Kartvelishvili Tamara , Tsitlanadze George , Edilashvili Lamara , Japaridze Nona , Katsarava Ramaz 
Published: April 2003

AbstractNovel biodegradable regular poly(ester urethane)s 2 (ηred ≤ 0,62 dL/g) were synthesized for the first time by polycondensation of di‐p‐toluenesulfonic acid salts of bis(phenylalanine) α,ω‐alkylene diesters 1 with di‐p‐nitrophenyl trimethylenedicarbonate (4) under mild conditions in organic solvents in the presence of triethylamine as acid acceptor. The first synthesis of homopoly(ester urea)s 3 (ηred ≤ 0,33 dL/g) was carried out by polycondensation of 1 with di‐p‐nitrophenyl carbonate (5) under the same conditions. Preliminary in vitro evaluation of specific and nonspecific hydrolysis of the polymers obtained has been brought about using potentiometric titration.
Polymerization behavior of electron‐accepting substituted quinodimethanes
Authors: Itoh Takahito , Iwatsuki Shouji 
Published: April 2003

AbstractThis article describes the polymerization behavior of electron‐accepting substituted quinodimethanes. Chlorine‐substituted quinodimethanes (1a–c) behave differently depending on the number of chlorine substituents. Strong electron‐accepting substituted quinodimethanes like 2a–c and 4 are not homopolymerizable, but copolymerizable with donor monomers like styrene in an alternating fashion. 7,7,8,8‐Tetrakis(alkoxycarbonyl)‐quinodimethanes (3a and 3b) and 7,7,8‐tris(tert‐butoxycarbonyl)‐8‐cyanoquinodimethane (5a) show amphoteric behavior in their alternating copolymerizations and in their charge‐transfer complex formation. Some substituted quinodimethanes with two different substituents on their exocyclic carbons (5b, 6a–c, 7a–e, 8a and 8b, and 9a–e) are homopolymerizable; for instance anionic polymerization of 7,8‐bis(butoxycarbonyl)‐7,8‐dicyanoquinodimethane (6c) takes place in a living way and gives a polymer with a molecular weight above 106. The homopolymerizations are equilibrium polymerization reactions and the thermodynamic parameters were determined. Their copolymerizations with styrene occur in a random fashion. The cross‐propagation step was studied by means of a linear free energy relationship and a new concept of radical alternating copolymerization is proposed.
Preparation and identification of di‐block copolymer composed of crystalline poly(ethylene oxide) and noncrystalline poly(vinyl acetate) with well‐defined structure
Authors: Huang Junlian , Huang Xiaoyu , Hu Wenbin 
Published: April 2003

AbstractA block copolymer of ethylene oxide (EO) and vinyl acetate (VAc) was prepared by sequential anionic and photo‐induced charge transfer polymerization (CTP) using UV sensible p‐aminophenoxy end groups on PEO (PEOa). The structure and composition of this block copolymer (PEO‐b‐PVAc) were identified in detail. The relationship between polymerization rate (Rp) and the concentrations of benzophenone (BP) and monomer, and the effect of the concentration and molecular weight of PEOa on the polymerization of VAc, are discussed; the relationship Rp ∝ [PEOa‐11000]0.33 [VAc]0.28 [BP]0.47 using benzene as a solvent was derived. The dependence of the thermal properties of PEO‐b‐PVAc on the length of the PVAc block is described. It turned out that the PEO and PVAc blocks are compatible.
Synthesis and properties of poly(ether imide)s derived from 4,4′‐(1,5‐naphthylenedioxy)diphthalic anhydride and various aromatic diamines
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Chu Kuan‐Yu 
Published: April 2003

AbstractA naphthalene unit‐containing bis(ether anhydride), 4,4′‐(1,5‐naphthylenedioxy)‐diphthalic anhydride, was prepared in three steps starting from the nucleophilic nitro‐displacement reaction of 1,5‐dihydroxynaphthalene and 4‐nitrophthalonitrile in N,N‐dimethylformamide (DMF) solution in the presence of potassium carbonate. High‐molarmass aromatic poly(ether imide)s were synthesized using a two‐stage polymerization process from the bis(ether anhydride) and ten aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0,66–1,27 dL/g. The films of poly(ether imide)s derived from some diamines, such as p‐phenylenediamine, benzidine, and bis[4‐(4‐aminophenoxy)phenyl] ether, crystallized and embrittled during the thermal imidization process. The other poly(ether imide)s were amorphous materials and could be fabricated into transparent, flexible, and tough films. These poly(ether imide) films had yield strengths of 111–125 MPa, tensile strengths of 96–150 MPa, elongations to break of 10–38%, and initial moduli of 1,6–2,4 GPa. All of these polymers were insoluble in organic solvents, except for that derived from 2,2‐bis[(4‐aminophenoxy)phenyl]propane. Their Tg's were recorded in the range of 226–265°C by DSC. Thermogravimetric analysis (TG) showed that all the polymers were stable up to 535°C in both air and nitrogen atmosphere.
Semifluorinated diblock copolymers. Synthesis, characterisation and amphiphilic properties
Authors: Krupers Maarten , Möller Martin 
Published: April 2003

AbstractSemifluorinated diblock copolymers based on methyl methacrylate and 1H,1H,2H,2H‐perfluoroalkyl methacrylates were prepared by nucleophilic catalysed group transfer polymerisation. Characterisation was carried out by 1H NMR spectroscopy, differential scanning calorimetry (DSC) and gel‐permeation chromatography (GPC) in toluene. The latter method revealed the formation of micelles. The surface activity of the materials was demonstrated by tensiometry using a Wilhelmy balance. Measurements on thin polymer films showed low critical surface tensions and low dispersion force contributions to the surface energy indicating the presence of the fluorinated block at the surface.
Polymers of carbonic acid, 23. Photoreactive cholesteric polycarbonates based on isosorbide, 4,4′‐dihydroxychalcone and 4,4′‐dihydroxybiphenyl
Authors: Kricheldorf Hans R. , Sun Shih‐Jieh , Sapich Beate , Stumpe Joachim 
Published: April 2003

AbstractNumerous copolycarbonates were prepared from 4,4′‐dihydroxychalcone, on the one hand, and methylhydroquinone, 4,4′‐dihydroxybiphenyl or isosorbide (1,4:3,6‐dianhydro‐D‐sorbitol), on the other. Three different polycondensation methods were compared, but polycondensation in an organic solvent using diphosgene as condensing agent proved to be the most satisfactory. The resulting copolycarbonates were characterized by their inherent viscosities, elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR) and 13C NMR spectra, by differential scanning calorimetry (DSC) measurements and by optical microscopy. The 13C NMR spectra proved the formation of almost random sequences in all cases. In contrast to the homopolycarbonate of chalcone which is crystalline and insoluble in inert solvents, all copolycarbonates of chalcone are completely or largely amorphous and soluble. Whereas 4,4′‐dihydroxychalcone itself proved to be nonmesogenic, copolycarbonates containing 4,4′‐dihydroxybiphenyl are thermotropic. Ternary copolycarbonates containing isosorbide as a chiral component are cholesteric and form Grandjean textures upon shearing in the molten state. Ultraviolet (UV) irradiation of thin films resulted in crosslinking.
Poly(phenylenevinylene)‐type conjugated alternating copolymers: Synthesis and optical properties in solution
Authors: Hilberer Alain , Van Hutten Paul F. , Wildeman Jurjen , Hadziioannou Georges 
Published: April 2003

AbstractWe have synthesized a series of new conjugated alternating copolymers containing oligo(p‐phenylenevinylene) units of well‐defined size and structure as conjugated chromophores in their main chain. In order to interrupt the conjugation between chromophores, the oligomers were linked to each other either via non‐π‐conjugated silylene units or directly, but in a non‐coplanar way. In this paper we describe the synthesis, the structural characterization and the optical properties in solution of these new copolymers.
Poly(vinyl alcohol) having amino sugar as the pendant group: Synthesis, characterization and binding of concanavalin A
Authors: García‐Oteiza Mari Carmen , Sánchez‐Chaves Manuel , Arranz Felix 
Published: April 2003

AbstractPoly(vinyl alcohol) (PVAL) samples partially functionalized with 4‐nitrophenyl carbonate groups were obtained by reaction of PVAL with 4‐nitrophenyl chloroformate using pyridine as a catalyst. 2‐Amino‐2‐deoxy‐D‐glucose (glucosamine) was virtually quantitatively bound to PVAL activated with 4‐nitrophenyl carbonate groups. Glucosamine‐carrying PVAL (PVAL‐G) and Concanavalin A (Con A) in phosphate buffer (pH 7,2) at room temperature were proven to interact with each other.
Preparation and evaluation of novel side‐chain liquid‐crystalline polydienes using photoinitiated free‐radical cyclopolymerization
Authors: Buxton Ian Peter , Hall Alan William , Lacey David 
Published: April 2003

AbstractThis investigation has shown that the technique of photoinitiated free‐radical polymerization can be used successfully to produce a variety of side‐chain liquid‐crystalline (SCLC) polydienes, which contain novel alicyclic ring structures along the polymer backbone. With the appropriate side chain, ferroelectric SCLC polymers can be prepared exhibiting wide S ranges and low Tg values. By synthesising a polydiene incorporating a lactone‐ring structure, clear evidence is provided that these types of polymers do contain an alicyclic ring structure along the polymer backbone. The systematic approach adopted for this investigation has also shown that the low DP values obtained for all the polydienes were due to degradative chain transfer.
Correction to “The glass transition of mixtures of polystyrene with alkyl‐terminated oligostyrene – experimental evidence for microphase separation in a polymer blend”1
Authors: Abetz Volker , Müller Gunther , Stadler Reimund , Schlick Shulamith 
Published: April 2003

AbstractIn this correction note we compare the predictions of the phase diagram of a bidisperse polystyrene blend by using different approaches for the segmental χ‐parameter. Depending on the approach very different results are obtained.
Physical aging of poly(ether sulfone) from enthalpy relaxation measurements
Authors: Jong Shi Ru , Lee Jun Sheng , Yu Tzyy Lung 
Published: April 2003

AbstractEnthalpy relaxation due to physical aging of hydroxyl‐terminated poly(ether sulfone)s (PES) with various molecular weights was studied by DSC at three aging temperatures between Tg − 45°C and Tg − 10°C. The experimental results revealed that both the average enthalpy relaxation time 〈τ〉 and limiting enthalpy relaxation ΔH∞ decrease slightly with increasing molecular weight for PESs aged at the same temperature intervals Tg − Ta (where Ta < Tg). This behavior is not quite consistent with the enthalpy relaxation process of polystyrene. Agrawal reported that the relaxation spectra for polystyrenes with different molecular weights could be superimposed when Tg − Ta was the same. The experimental results of the present work suggest that the motion of segments is affected by intermolecular hydrogen bonding through the OH groups of the PES chain ends.
Metallocene‐catalyzed propene/1‐hexene copolymerization: Influence of amount and bulkiness of cocatalyst and of solvent polarity
Authors: Forlini Fabrizio , Fan Zhi‐Qiang , Tritto Incoronata , Locatelli Paolo , Sacchi Maria Carmela 
Published: April 2003

AbstractAn investigation on the effect of the variation of the amount and the structure of cocatalyst and of polarity of the solvent on propene/1‐hexene copolymerization with the isospecific catalyst rac‐[ethylenebis(1‐indenyl)]zirconium dichloride (rac‐(EBI)ZrCl2) was performed. A noticeable enhancement of copolymerization activity and a moderate increase of the molecular weights were observed with increasing MAO/Zr ratio as well as upon mixing methylaluminoxane (MAO) and AliBu3, while isotacticity and comonomer composition are not affected by such variations. On the other hand, a gradual increase in CH2Cl2 content in the CH2Cl2/toluene solvent mixture, which greatly increases the copolymerization activity, noticeably influences the molecular weight and sensibly enhances the 1‐hexene comonomer content. The formation of cationic active species, separated from their counterions, might be the cause of the better accessibility of the active sites for the bulkier comonomer.
Illustration of surface crosslinking of different polymers treated in argon plasma
Authors: Poncin‐Epaillard Fabienne , Vallon Sophie , Drévillon Bernard 
Published: April 2003

AbstractThe influence of argon plasma on polycarbonate (PC) and poly(propylene) (PP) has been studied in terms of structural changes and reaction mechanisms. In situ UV‐visible ellipsometry reveals formation of a surface layer with a higher refractive index than the untreated polymer. The increase in the refractive index is attributed to polymer densification, which is assigned to crosslinking. However, a decrease in the average molecular weight of the PC is also observed and two populations of macromolecules of different size are detected by light scattering measurements, revealing a competition between crosslinking and degradation. The reaction mechanisms were investigated using Nuclear Magnetic Resonance (1H NMR) and in situ IR ellipsometry. Degradation is caused by carbonate bond breaking, while crosslinking seems to be related to a decrease in methyl groups. The ellipsometry results are correlated with amorphous phase extraction and 1H NMR analysis of modified PP. The crosslinking mechanism involves the elimination of methyl groups, and also the formation of exomethylenic bonds. Spectroscopic ellipsometry appears to be a valuable tool to study the interaction between a plasma and a polymer, as UV‐visible ellipsometry is sensitive to structural changes in the polymer, while IR ellipsometry detects the appearance and disappearance of chemical groups in a surface layer.
Synthesis of poly(ethylene oxide) with a terminal amino group by anionic polymerization of ethylene oxide initiated by aminoalcoholates
Authors: Mosquet Martin , Chevalier Yves , Le Perchec Pierre , Guicquero Jean‐Pierre 
Published: April 2003

AbstractPoly(ethylene oxide)s having a primary or secondary amino group at one chain end have been synthesized by direct anionic polymerization of ethylene oxide initiated by aminoalcoholates. The ring opening reaction of ethylene oxide by the amino group could be avoided when the alcoholate was reactive enough, that is, with potassium alcoholates in dry aprotic medium (THF). In this case, a living anionic polymerization of ethylene oxide occurred, with full conversion of the monomer. This is shown by the NMR and molecular weight characterizations of the polymers and kinetic studies of the polymerization.
Complex‐radical cyclocopolymerization of allyl a‐(N‐maleimido)acetate with styrene and maleic anhydride
Authors: Rzaev Zakir M. O. , Salamova Ulviye U. , Altindal Şemsettin 
Published: April 2003

AbstractRadical copolymerizations of allyl a‐(N‐maleimido)acetate (AMI) with styrene (D, electron‐donor) or maleic anhydride (A, electron‐acceptor) were carried out in benzene and/or methyl ethyl ketone (MEK) at 50–70°C in the presence of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The structure and properties of copolymers synthesized were derived from IR, chemical, DTA and TGA analyses. Side‐chain unsaturation of macromolecules was also proved by the crosslinking effect observed. Kinetic parameters of copolymerization such as complex‐formation (Kc), cyclization (kcyc), and copolymerization constants and ratios of chain growth rates for the participation of monomer charge transfer complexes (CTC) and free monomers for both systems were obtained: Kc = 0,20 ± 0,01 and 0,05 ± 0,005 L/mol in CH3COOH‐d4 at 35 ± 0,1°C (1H NMR method) for D…AMI and AMI… A complexes, respectively; kcyc · 105 = 1.71 and 0,66 L/(mol · s), r1 = 0,13 ± 0,01 and 0,037 ± 0,002, r2 = 0,048 ± 0,002 and 0,052 ± 0,002 (by Kelen‐Tüdőş method), k12/k21 = 0,20 and 0,62, k1c/k12 = 0,6 and 29,8, k2c/k21 = 4,8 and 9,1 for the D‐AMI and AMI‐A systems, respectively. The results show that alternating cyclocopolymerization reactions are realized which are carried out via a “mixed” mechanism in the D‐AMI system and via a “complex” mechanism in the AMI‐A system, with formation of cyclolinear macromolecules containing side‐chain unsaturated fragments of “allyl” (D‐AMI copolymer) and “imide” (AMI‐A copolymer) types. The synthesized copolymers easily undergo crosslinking by thermotreatment (105°C, 30 min) and/or by UV‐irradiation (25°C, 15 min), which was confirmed by DTA and TGA analyses.
PdCl2‐induced chain transfer reaction by hydrogen at the initial stage of propene polymerization with MgCl2‐supported Ziegler catalyst
Authors: Mori Hideharu , Iizuka Takehiko , Tashino Kunihiko , Terano Minoru 
Published: April 2003

AbstractThe PdCl2‐induced chain transfer reaction by hydrogen in the initial stage of propene polymerization with a MgCl2‐supported Ziegler catalyst was studied by means of the stopped‐flow polymerization technique. A chain transfer reaction was found to occur even in the initial stage of the polymerization in the presence of PdCl2 which dissociates the hydrogen molecule. PdCl2 itself has no ability for propene polymerization as well as for the chain transfer reaction. The results indicate that the chain transfer reaction occurs through atomic hydrogen formed on PdCl2 particles.
Synthesis and radical polymerization behavior of a novel methacrylate with an L‐leucyl‐L‐alanylglycine peptide moiety
Authors: Murata Hironobu , Sanda Fumio , Endo Takeshi 
Published: April 2003

AbstractThe synthesis and radical polymerization behavior of a novel methacrylate having a peptide moiety, N‐benzyloxycarbonyl‐L‐leucyl‐L‐alanylglycine 2‐methacryloyloxyethyl ester (1), are described. 1 shows radical polymerizability in spite of the bulky peptide moiety. Only the ester group near the peptide moiety of poly(1) could be hydrolyzed selectively and completely in the hydrolysis of poly(1) in an alkaline solution.
Orientation behavior of smectic polymer networks by uniaxial mechanical fields
Authors: Nishikawa Etsushi , Finkelmann Heino 
Published: April 2003

AbstractPolymer networks showing different smectic polymorphism with either an interdigitated smectic A to undulated smectic A phase transformation or an interdigitated smectic A to double layer smectic C phase transformation are synthesized. Their orientation behavior in uniaxial mechanical fields is investigated by means of X‐ray scattering techniques and thermal expansion measurements. By applying uniaxial extension to the smectic elastomers in the isotropic state ordered smectic networks result with the director uniformly aligned parallel to the strain axis. These networks are optically transparent. Uniaxial deformations of the ordered smectic networks in the direction parallel and perpendicular to the director are performed that also help to elucidate the structure of the smectic phases. We find a reorientation process of layers of the ordered smectic C network. The spontaneous elongation in the direction of the director at the isotropic to smectic A phase transformation of the smectic elastomers is observed by thermoelastic measurements. This indicates that the polymer backbone conformation in the smectic elastomers is prolate in contrast to previous observations of oblate chain conformation in linear smectic polymers.
Synthesis of biomedical, fluorescence‐labelled polyesterurethanes for the investigation of their degradation
Authors: Ciardelli Gianluca , Kojima Kazushige , Lendlein Andreas , Neuenschwander Peter , Suter Ulrich W. 
Published: April 2003

AbstractThe synthesis and characterization of fluorescence‐labelled, phase segregating block polyesterurethanes based on the known biocompatible and degradable materials poly[(R)‐3‐hydroxybutyric acid] (PHB), poly(ϵ‐caprolactone) (PCL), and poly[(ϵ‐caprolactone)‐co‐glycolide] (PCL/PGA) is described. To introduce fluorescence labels in the amorphous domains of the polymers, phenacyl 10,11‐dihydroxyundecanoate (PDUA) was synthesized and copolymerized with a PHB diol, a PCL diol, and aliphatic diisocyanates. After cleavage of the protecting group (without degradation of the polymer backbone), the carboxyl group was reacted with a fluorescent amine (dansylcadaverine) in the presence of 4,6‐diphenylthieno[3,4‐d]‐1,3‐dioxol‐2‐one 5,5‐dioxide (Steglich reagent). Also a polymer containing 13C‐labelled carboxy groups was synthesized and the labelling reaction monitored by 13C NMR spectroscopy. To introduce fluorescence labels in the hard segment of the polymers, a new low‐molecular‐weight diol based on poly[(R)‐hydroxybutyric acid] and containing protected carboxy groups was synthesized. After the deprotection, the carboxy groups were reacted with a fluorescent amine (dansylcadaverine) in the presence of an activating system based on dicyclohexylcarbodiimide. The labelled PHB diol was then copolymerized with a poly[(ϵ‐caprolactone)‐co‐glycolide] diol and an aliphatic diisocyanate. The so obtained fluorescence‐labelled block polyesterurethanes are promissing materials for the investigation of the biocompatibility and degradation of the corresponding, non‐labelled materials (DegraPol®) by means of fluorescence‐aided microscopic and spectroscopic techniques.
Photocalorimetric monitoring of the polymerization of an oligo(ethylene glycol) dimethacrylate in oligo(ethylene glycol) dimethyl ethers
Authors: Sandner Barbara , Kotzian Norbert , Tübke Jens , Wartewig Siegfried , Lange Otfried 
Published: April 2003

AbstractThe course of the 2,4,6‐trimethylbenzoyldiphenylphosphine oxide initiated free‐radical photopolymerization of an oligo(ethylene glycol) dimethacrylate ((EG)23DMA) in two oligo(ethylene glycol) dimethyl ethers ((EG)3DME and (EG)11DME) in the presence of LiCF3SO3 has been studied by means of differential scanning calorimetry (DSC), FT‐Raman spectroscopy and sol‐gel analysis. In order to obtain the kinetical data of the fast photopolymerization, the photo‐DSC curves were corrected numerically. Both, the initial and the maximum polymerization rates were found to depend on the concentration of the monomer and the photo‐initiator with the order 2,5 and 0,2, respectively. Upon addition of LiCF3SO3, the polymerization rate is increased. Grafting reactions from (EG)11DME were observed resulting in its partially linking to the poly(methacrylate) network.
NMR imaging of technical SBR vulcanizates under dynamic mechanical load
Authors: Hauck Daniela , Blümler Peter , Blümich Bernhard 
Published: April 2003

AbstractInhomogeneous heating of carbon‐black filled SBR (styrene‐co‐butadiene rubber) cylinders was mapped by NMR imaging in situ during dynamic mechanical load. The linear relationship betweenT2and temperature was used for direct imaging of temperature profiles. Experiments were performed as a function of shear frequency between 0 and 10 Hz and of carbon black contents between 10 and 70 phr (parts per hundred rubber). For a composite cylinder with a hard core and a soft shell an unexpected heat distribution was observed.
On the interaction of supported zirconocene catalysts with alkylaluminium co‐catalysts
Authors: Semikolenova Nina V. , Zakharov Vladimir A. 
Published: April 2003

AbstractThe interaction of supported metallocene catalysts with methylaluminoxane leads to the desorption of the metallocene compound from the surface of the support and the formation of highly active homogeneous complexes. The catalytic properties of the system and characteristics of polyethylene formed are determined by these species.