bluuebunny/crossref_metadata_2025_split huggingface dataset:
1,3‐Oxazoline intermediates in reactive processing applications, 2.multiphase polymer blends via in‐situ cationic melt phase polymerization of 2‐phenyl‐1,3‐oxazoline
Authors: Müller Philipp , Wörner Christof , Mülhaupt Rolf 
Published: April 2003

Abstract2‐Phenyl‐1,3‐oxazoline was injected into poly(ethene‐co‐methacrylic acid), containing 4,25 mol‐% methacrylic acid units, at 225°C. In the first stage, 2‐phenyl‐1,3‐oxazoline reacted with carboxylic acid groups to form esteramide side chains via grafting reaction. In the second stage, 2‐phenyl‐1,3‐oxazoline containing methyl 4‐nitrobenzensulfonate initiator was added to initiate in‐situ cationic polymerization, yielding poly(N‐benzoylethylenimine) as dispersed phase with 0,2–3,5 μm average diameter. Morphological, mechanical and thermal properties of poly‐(ethene‐co‐methacrylic acid) blends, prepared by grafting combined with in‐situ polymerization of 2‐phenyl‐1,3‐oxazoline, were investigated.
Anionic polymerization of fluorine‐containing vinyl monomers, 12. Anionic polymerization mechanism of hexafluoro‐1,3‐butadiene
Authors: Nishimura Shin , Takahashi Akio , Narita Tadashi , Hagiwara Tokio , Hamana Hiroshi 
Published: April 2003

AbstractInitiation and propagation reaction mechanisms of the anionic polymerization of hexafluoro‐1,3‐butadiene (HEBD) were investigated. The initiation reaction with caesium tert‐butoxide was found to be completed within 5 min although the reactions were carried out at a much lower temperature than that of the polymerization reaction. The initiation reaction was, therefore, inferred to take place in an anionic fashion by adding the tert‐butoxide anion to HFBD. In order to clarify the propagation reaction mechanism of HFBD which yielded a polymer with a polyvinylene structure, the polymerization reactivity of HFBD and hexafluoro‐2‐butyne (HFBY), the isomerization of HFBD to HFBY, and the structural difference between poly(HFBD) and poly(HFBY) were discussed. In spite of the low yield of HFBY by the isomerization reaction under polymerization conditions, higher yields of poly(HFBD) were obtained. Judging from the X‐ray analysis which showed that poly(HFBD) was highly crystalline and poly(HFBY) was amorphous, poly(HFBD) might not be produced by polymerization of HFBY. An addition reaction of the propagating anion to the carbon‐2 of the HFBD monomer followed by isomerization at the propagating living end to yield poly[1,2‐bis(trifluoromethyl)vinylene] is proposed.
Cationic polymerization of glycidol. Polymer structure and polymerization mechanism
Authors: Dworak Andrzej , Walach Wojciech , Trzebicka Barbara 
Published: April 2003

AbstractGlycidol (2‐epoxy‐1‐propanol) was polymerized under the action of Lewis acids (BF3OEt2,, SnCl4) and protonic acids (CF3COOH, CF3SO3H). Polymers with number‐average molecular weights (M̄n) varying from 2500 to 6000 g/mol were obtained. The structure of obtained polymers was characterized by 13C and 29Si NMR spectroscopy, and the amount of 1‐3 units, 1‐4 units and chain branches was determined. The structure of the polymers was related to the polymerization mechanism, especially to the contribution of activated monomer mechanism in chain growth.
Polymerization of methyl methacrylate with achiral 4B group metallocene compounds
Authors: Deng Hai , Shiono Takeshi , Soga Kazuo 
Published: April 2003

AbstractMethyl methacrylate (MMA) was polymerized with Cp2ZrCl2/ methylalyminoxane or Cp2M(CH3)2 (M: Zr, Hf; Cp = cyclopentadienyl) combined with B(C6F5)3 (1) or Ph3CB(C6F5)4 (2), (Ph = phenyl). in the presence of a Lewis acid like Zn(C2H5)2 with slow inititation, which gave syndiotactic‐rich poly(methyl methacrylate) (PMMA) with high molecular weight. The polymer yield increases with polymerization time, which indicates that the propagation rate is zero order in concentration of monomer. The polymer yield increases also with concentration of Cp2Zr(CH3)2.2, which indicates the zirconocene to be the real catalyst. The polymer yield and the initiation efficiency (N/[Zr]) increase with the concentration of Zn(C2H5)2, which indicates Zn(C2H5)2, to be involved in the initiation. It is also shown that the propagation reaction is independent of the concentration of Zn(C2H5)2.
Synthesis and properties of segmented poly(ether‐urethanes) with specially designed and symmetrically chain‐folding poly(N‐alkylurethane) hard segments
Authors: Eisenbach Claus D. , Stadler Edmund 
Published: April 2003

AbstractThe study of a series of segmented poly(ether‐urethanes) with highly flexible poly(oxytetra‐methylene) soft segments and especially designed, molecularly uniform poly(N‐alkylurethane) hard segments based on piperazine and 1,4‐butanediol bischloroformate has shown that size, shape and perfection of the hard domains can be varied by both the primary structure of the urethane chain and the sample history. Depending on the conformation or the stereogeometry of the built‐in central constitutive hard segment unit, chain‐extended or chain‐folded hard segment crystallization, i. e., the formation of cylindrical or lamellar shaped hard domains can be achieved. These thermoplastic elastomers exhibit distinctly different properties which correlate systematically with the supermolecular structure and the corresponding hard segment architecture, respectively.
Process analysis: properties of poly(ethylene terephthalate) measured by near infrared spectroscopy, 1. At‐line analysis of poly(ethylene terephthalate) chips
Authors: Van Uum Marinus P. B. , Lammers Hans , De Kleijn Jaap P. 
Published: April 2003

AbstractNear infrared (NIR) reflectance spectra recorded from poly(ethylene terephthalate) (PET) chips contain a sufficient amount of information to estimate the number of carboxylic end groups and the relative viscosity. To obtain reliable results, careful attention has to be paid to the calibration procedure.
Process analysis: properties of poly(ethylene terephthalate) measured by near infrared spectroscopy, 2. In‐line analysis of poly(ethylene terephthalate) melt
Authors: Lammers Hans , Van Uum Marinus P. B. , De Kleijn Jaap P. 
Published: April 2003

AbstractNear infrared (NIR) transmission spectra recorded from poly(ethylene trerephthalate) (PET) melt contain a sufficient amount of information to estimate the number of carboxylic end groups and the relative viscosity. In‐line monitoring of these quality parameters is feasible.
Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents
Authors: Out Gerardus J. J. , Schlössels Frank , Turetskii Alexei A. , Möller Martin 
Published: April 2003

AbstractThe columnar mesophase formation of poly(dibutylsiloxane) (PDBS) was studied with respect to the influence of molecular weight. Additionally, the synthesis of random copolymers containing dibutylsiloxane and butyl(3‐cyanopropyl)siloxane units was performed in order to examine the influence of side group polarity on the columnar mesophase behaviour without disturbing the overall molecular geometry. Introduction of 6% 3‐cyanopropyl groups appeared to hinder crystallization while copolymers containing 17% 3‐cyanopropyl groups did not show crystallization at all. All copolymers formed a columnar mesophase which seemed to gain stability from the presence of the polar substituents.
Polymeric photosensitizers, 1. Synthesis and photochemical properties of poly[(sodium p‐styrenesulfonate)‐co‐(4‐vinylbenzyl chloride)] containing rose bengal chromophores
Authors: Nowakowska Maria , Kepczyński Mariusz , Szczubialka Krzysztof 
Published: April 2003

AbstractThe new polymeric photosensitizer poly[(sodium p‐styrenesulfonate)‐co‐(4‐vinylbenzyl chloride/rose bengal)] for singlet oxygen production in aqueous solutions was synthesized and studied. The polymer contains rose bengal (4,5,6,7‐tetrachloro‐2′,4′,5′,7′‐tetraiodofluorescein) chromophores covalently attached to the polymer chain. The quantum yield of singlet oxygen formation by the polymer‐bound chromophore was found tobe close to that determined for free rose bengal. The polymer has been shown to photosensitize oxidation reactions in aqueous media.
Anionic polymerization of alkyl methacrylates in the presence of diethylzinc
Authors: Ozaki Hiroyuki , Hirao Akira , Nakahama Seiichi 
Published: April 2003

AbstractThe anionic polymerizations of methyl methacrylate (MMA), isopropyl methacrylate (IPMA), and tert‐butyl methacrylate (TBMA) in THF in the presence of diethylzinc were investigated. The addition of diethylzinc to the reaction mixture remarkably lowers the polymerization rates of the methacrylates initiated with potassium diphenylmethanide to afford polymers with the predicted molecular weights and very narrow molecular weight distributions, while PMMA and poly(IPMA) produced with potassium diphenylmethanide in the absence of diethylzinc have rather broad molecular weight distributions. The stereospecificities of PMMA, poly(IPMA) and poly(TBMA) are not affected by diethylzinc. From the result of the block copolymerization of MMA with TBMA, it was found that the presistency of the anionic propagating end of PMMA is significantly enhanced by the addition of diethylzinc. The retardation of the polymerization rates and the enhancement of the persistency of the propagating end in the presence of diethylzinc may be caused by the weak coordination of diethylzinc toward the enolate anions at the propagating end groups.
Structural characterisation of a new heparinisable material based on ethylene/vinyl alcohol/vinyl acetate terpolymer and a poly(amido‐amine)
Authors: Lamponi Stefania , Tempesti Federica , Magnani Agnese , Benvenuti Manuela , Barbucci Rolando , Ranucci Elisabetta , Cimmino Sossio , Martuscelli Ezio , Baszkin Adam , Boissonnade Marie‐Martine 
Published: April 2003

AbstractPartially hydrolyzed ethylene/vinyl acetate copolymers (EVALVA) were modified by covalent binding of a heparin‐complexing poly(amido‐amine) (N2LL). The physicochemical characterisation of the starting and modified materials was carried out through thermal analysis, dynamic mechanical thermal analysis, mechanical tensile test, contact angle, potentiometric measurements, water uptake and FT‐IR spectroscopic measurements. The behaviour of this material in both the dry and the wet state was stressed, evidencing the different orientation of the chemical groups, which are buried or exposed according to whether its nature is hydrophilic or hydrophobic. The material was heparinised, and the presence of heparin was revealed by energy dispersive X‐ray analysis (EDAX) and FT‐IR.
Preparation of a triphenylcarbinol moiety‐containing cellulose derivative and its properties
Authors: Arai Kenichiro , Kawabata Yumi 
Published: April 2003

AbstractA triphenylcarbinol (TPC) moiety‐containing cellulose derivative (TPC‐Cell) was prepared by a two‐step reaction. First, microcrystalline cellulose was dissolved in SO2‐diethyl‐amine‐dimethyl sulfoxide and homogeneously reacted with p‐bromobenzyl bromide to obtain tri‐O‐(p‐bromobenzyl)cellulose (BB‐Cell). Second, the BB‐Cell was reacted with butyllithium and then with Michler's ketone. The degree of substitution (DS) of the obtained ethanol‐soluble TPC‐Cell was up to 0,56. The leuco form of TPC moiety in TPC‐Cell showed a small extent of ionic dissociation in ethanol under irradiation with UV light of λ > 290 nm, accompanied by a large extent of decomposition of the structure. With additions of acid and then of alkali, the TPC structure was reversibly isomerized from the leuco form to the colored from and then from the colored from to the leuco form. However, repeated cycles of the additions of acid and alkali resulted in considerable fatigue with the number of cycles.
Synthesis of a polyethylene‐graft‐polystyrene copolymer and its compatibilization for linear low density polyethylene/poly(phenylene oxide) blends
Authors: Chen Hui , Wang Jianguo , Zhang Xuequan , Tang Tao , Huang Baotong 
Published: April 2003

AbstractBased on unsteady diffusionkinetics, polyethylene(PE)‐graft‐polystyrene (PS) copolymers were designed and synthesized with a heterogeneous high yield titanium‐based catalyst by copolymerization of ethylene with a PS‐macromonomer using 1‐hexene as a short main agent to promote the incorporation of the PS‐macromonomer. The presence of 1‐hexene facilitated the diffusion of the PS‐macromonomer, giving rise to the significantly increased incorporation of the PS‐macromonomer. Compatibilization of blends of linear low density polyethylene (LLDPE)/poly(phenylene oxide) (PPO) with the PE‐g‐PS copolymer were investigated using scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA).
Degradability of hydrogels containing azoaromatic crosslinks
Authors: Yeh Ping‐Yang , Kopečkova Pavla , Kopeček Jindřich 
Published: April 2003

AbstractA novel type of biodegradable, pH‐sensitive hydrogels was synthesized by crosslinking of N,N‐dimethylacrylamide copolymer precursors. These hydrogels contained azoaromatic crosslinks which may be degraded by the azoreductase activities in the colon. Hydrogel degradation experiments were performed both in vitro and in vivo, using rat cecum contents and implantation into the rat cecum, respectively. In order to evaluate the influence of the detailed network structure on the degradation properties, the degradability of hydrogels synthesized by two different methods, i.e., crosslinking of polymeric precursors and crosslinking copolymerization, were compared. Two different patterns of the degradation of hydrogels were observed, i. e., a surface erosion process and a bulk‐degradation‐like process. The azo bond cleavage rate of hydrogels prepared by crosslinking of polymeric precursors was faster than that of hydrogels prepared by crosslinking copolymerization. The differences in the gel degradation pattern and the cleavage rate of azo bonds were attributed to the differences in the structure of the hydrogel network, i. e., the molecular weight of primary chains and the formation of chain entanglements. Under the experimental conditions used, the degradation rate in vivo was 3 to 5 times faster than that in vitro. It appears that these hydrogels have a potential for colon‐specific drug delivery.
Télomérisation en milieu aqueux, 1. Télomérisation de l'acide acrylique avec l'acide thioglycolique
Authors: Boutevin Bernard , Rigal Gérard , El Asri Mohammed , Lakhlifi Tahar 
Published: April 2003

AbstractThe telomerization of acrylic acid with thioglycolic acid (mercaptoacetic acid) in aqueous medium, with various initiators (H2O2,Na2S2O8,K8 thermal initiation and 2,2′‐azobis (2‐amidiniopropane) dihydrochloride) has been achieved. Thus, we were able to point out the limitation of the chain length due to the transfer agent, which is characteristic of a telomerization reaction. Mono‐, di‐and tri‐adducts were isolated and characterized after esterification of the reaction medium with ethanol, then hydrolized. These various adducts were used as standards for size‐exclusion chromatography, and the influence of the reaction parameters (initiator, temperature, quality of solvent, amount of telogen was investigated). We also determined the transfer constant of thioglycolic acid (CT = 0,47). It is worth to note that knowing this value, it is possible to control precisely the number ‐average degree of polymerization of this type of reaction. This allowed us to prepare telomers with a 50% final weight concentration in the dry extract, as it was recommended for their use in paper industry.
Composition‐dependent Flory‐Huggins parameters: molecular weight influences at high concentrations
Authors: Petri Hans‐Michael , Wolf B. A. 
Published: April 2003

AbstractFlory‐Huggins interaction parameters χ were determined by means of equilibrium vapor pressures (measured via a combination of a head‐space sampler with a gas chromatograph) and light scattering as a function of composition and temperature for the systems cyclohexanone/polystyrene [CHO/PS] and cyclohexanone/poly(butyl methacrylate) [CHO/PBMA]. The investigation of molecular weight influences on χ with the system CHO/PBMA demonstrates that they persist almost up to the pure polymer. In order to rationalize this result, it is postulated (in accord with experimental findings and theoretical predictions) that the dimensions of polymer chains may vary upon the addition of solvent even in highly concentrated solutions. From the information concerning χ(T) the inter action parameters were split into their enthalpy and entropy part. In the case of CHO/PS these quantities vary considerably with composition and turn out to be linearly interrelated.
New chain transfer agents for radical polymerization based on the addition‐fragmentation mechanism
Authors: Jiang Shuiping , Viehe Heinz G. , Oger Nicole , Charmot Dominique 
Published: April 2003

AbstractThis study describes 15 compounds with allylic or pentadienic structure carrying either captodative (cd) carbon‐ or heteroatom substituents as potential radical leaving groups in an addition‐fragmentation reaction. Their experimental evaluation as chain‐transfer agents (CTA) was achieved in radical polymerization of styrene and methyl methacrylate. The α‐(cd‐substituted methyl)acrylates 9 and 11 were more efficient than the t‐thioether 10 in lowering molecular weight of polystyrene. The dienes are particularly effective and provide macromonomers with terminal diene functions which are very useful for further copolymerization with a variety of vinyl monomers.
Cyclopolymerization. Chirality induction for the synthesis of chiroselective corand/ionophore ligands
Authors: Yokota Kazuaki , Haba Osamu , Satoh Toshifumi , Kakuchi Toyoji 
Published: April 2003

AbstractThis article presents several methods to prepare polymeric chiral crown ethers by cyclopolymerization. Chiral templates such as 1,1′‐bi‐2‐napthol, D‐mannitol, L‐threitol, and pyranosidic sugars are very useful for synthesizing the polymers by cyclopolymerization of divinyl ethers, polymers which posses the ability of chiral recognition towards α‐amino acids. The chiral twist of the (R)‐ or (S)‐binaphthyl template induces the main chain to form a chiral, R,R‐ or S,S‐racemo sequence, respectively. Other templates with chiral axis can be also used as a tool for chirality induction in cyclopolymerization and cyclocopolymerization. The initiating system consisting of chiral alkylsulfonic acid and Lewis acid induces the enantioselective cyclopolymerization of a divinyl acetal (37). Chiral diepoxides polymerize regio‐ and stereospecifically with Lewis acid and KOH, and especially the diepoxide originating from D‐mannitol forms a polymer having the character as a new macromolecular ionophore.
Rare earth metal initiated polymerizations of polar and nonpolar monomers to give high molecular weight polymers with extremely narrow molecular weight distribution
Authors: Yasuda Hajime , Ihara Eiji 
Published: April 2003

AbstractOrganolanthanide (III) initiated polymerizations of alkyl methacrylates and alkyl acrylates proceed in a living fashion and yield high molecular weight polymers with extremely narrow molecular weight distribution at high conversion. Random and block copolymerizations of alkyl acrylates are carried out successfully to give almost “monodisperse” polymers. Rare earth metal initiated polymerizations of lactones such as ε‐caprolactone and δ‐valerolactone produce again high molecular weight polymers with narrow molecular weight distribution. Bulky divalent and trivalent rare earth metal complexes catalyze the living polymerization of ethylene and α‐olefins and the Sm (OR)3/AIR3H2O initiator system catalyzes the polymerization of propylene oxide to give polymers with narrow molecular weight distribution.
Kinetics of free radical solution polymerization of methyl methacrylate over an extended conversion range
Authors: Beuermann Sabine , Buback Michael , Russell Gregory T. 
Published: April 2003

AbstractThe low and intermediate conversion solution polymerization kinetics of methyl methacrylate in toluene and in 2‐butanone are investigated. For this purpose, repetitively applied laser pulses are employed to stimulate initiation, and quantitative near infrared spectroscopy is used to determine methyl methacrylate concentrations. The monomer concentration change per pulse is measured; it is shown how this information may be converted into coupled values of the rate coefficient for propagation kp, the rate coefficient for termination kt, and the total efficiency of (photo)initiation. In the present case kp is already known from independent investigations, which enables our pseudostationary state methods to yield kt directly. The major thrust of this paper, therefore, concerns the effect of solvent on kt: it is found that at both low and intermediate conversions, kt increases as the solvent concentration increases; possible causes of this are discussed. The effect of initial solvent fraction on the variation of kt with conversion is also reported. Although all our experimental measurements are carried out at an elevated pressure (1000 bar) and a single temperature (30°C), there is no reason for suspecting that our findings regarding solution polymerization termination should not be representative for polymerizations of methyl methacrylate (and other methacrylate monomers) in general.
Concurrent crystallization and interdiffusion in microlayers of polycarbonate and a copolyester
Authors: Nazarenko Sergey , Haderski Denise , Hiltner Anne , Baer Eric 
Published: April 2003

AbstractConcurrent crystallization and interdiffusion of two miscible polymers, polycarbonate (PC) and a copolyester (KODAR), was studied in microlayers with 657 alternating layers. Minimal mixing of the two components during processing was indicated by separate glass transitions of the PC and KODAR layers. Changes in the glass transitions after the microlayers were annealed above the glass transition of PC were determined by DSC and DMTA. When the annealing temperature was 200°C or higher, interdiffusion was much faster than crystallization and the glass transitions gradually shifted closer together until they merged into a single transition. An analysis based on Fick's law of diffusion described the relationship between the glass transition temperatures and the annealing time. At 195°C, the rates of interdiffusion and crystallization were comparable. Annealing at this temperature resulted in more complex changes in the glass transitions, including the persistence of two transitions after long annealing times. This behavior was understood by considering an interlamellar amorphous phase that was trapped in the spherulites and not available for interdiffusion. Models were developed from the spherulite morphology observed in the optical microscope. Two cases were considered: a continuous layer of impinged spherulites in the PC/KODAR 20/80 (w/w) composition, and isolated spherulites aligned with the center of the KODAR layer in PC/KODAR 40/60 and 60/40. These models satisfactorily reproduced the principal features of concurrent crystallization and interdiffusion.