bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low‐temperature structural relaxation in poly(alkyl methacrylate)s and related polymers probed by photochemical hole burning
Authors: Tanaka Satomi , Machida Shinjiro , Yamashita Takashi , Horie Kazuyuki 
Published: April 2003

AbstractExcursion temperature dependences of spectral hole profiles in photochemical hole burning for free‐base systems porphyrin/poly(alkyl methacrylate)s are investigated to see the relationship between relaxation properties and chemical structure of the polymers. The irreversible change in hole width is a characteristic of each polymer and is very similar to the relaxation behavior measured mechanically and dielectrically. Poly(methyl methacrylate) (PMMA) shows the highest thermal stability of hole profiles among the polymers presently studied with no marked appearance of local relaxation at 20–100 K. Poly(ethyl methacrylate) (PEMA) and poly(isopropyl methacrylate) (PiPMA) show an increase in hole width even at 20 K with a plateau region at 50–70 K, which is attributed to the rotation of the ethyl or isopropyl group around the CO bond. Polymers which contain more than two serial methylene groups in the side chains (poly(propyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate)) show a similar relaxation behavior around 50–60 K, suggesting the onset of the rotation of the terminal ethyl or isopropyl group in the ester side chain around the CC bond. Low‐density polyethylene (LDPE) shows a similar excursion‐temperature dependence probably due to the existence of branched oligomethylene side chains. The relaxation behavior is independent of the nature of chromophores, which indicates that irreversible hole broadening is controlled mainly by the local motion of the host matrices.
p‐Toluenesulfonyl esters in cellulose modifications: acylation of remaining hydroxyl groups
Authors: Heinze Thomas , Rahn Kerstin , Jaspers Mariet , Berghmans Hugo 
Published: April 2003

AbstractNew soluble cellulosics with interesting molecular structures and properties were obtained by the acylation of remaining hydroxyl groups of pure, homogeneously synthesized p‐toluenesulfonylcelluloses of different degree of p‐toluenesulfonyl (tosyl) substitution (DSTosyl) ranging from 0.5 to 2.0 in pyridine and sodium acetate as a catalyst with various aliphatic, aromatic and unsaturated carbonic acid anhydrides as well as isocyanates. The reactions proceed homogeneously and yield products of a high degree of acyl substitution (DSAcyl). In the case of acetic and propionic acid anhydrides a complete functionalization of all free hydroxyl groups was achieved. Even with fatty acid anhydrides like stearic anhydride 94% of the remaining OH groups were acylated. The new polymers are readily soluble in common organic solvents such as acetone, dimethyl sulfoxide, N,N‐dimethylacetamide, N,N‐dimethylformamide, and tetrahydrofuran. They are solution processible film‐ and membrane‐forming materials. Tosylcellulose phthalates and trimellitates of appropriate DSTosyl and DSAcyl values are even soluble in aqueous NaOH. Compared to the original tosylcelluloses, the thermal degradation of tosylcellulose acylates was initiated at nearly the same temperature independent of type and degree of esterification providing an equal DSTosyl. The stability found is sufficiently high for processing.
Structures of polyethylene and copolymers of ethylene with 1‐octene and oligoethylene produced with the Cp2ZrCl2 and [(C5Me4)SiMe2N(t‐Bu)]TiCl2 catalysts
Authors: Soga Kazuo , Uozumi Toshiya , Nakamura Shuji , Toneri Tatsuya , Teranishi Toshiharu , Sano Tsuneji , Arai Takashi , Shiono Takeshi 
Published: April 2003

AbstractPolymerization of ethylene and copolymerizations of ethylene with 1‐octene and oligoethylene having a vinyl end group were conducted with Cp2ZrCl2 and [(C5Me4)SiMe2N(t‐Bu)]TiCl2a as catalysts, and the structures of the resulting polymers were analyzed in detail. The Cp2ZrCl2 catalyst combined with methylalumoxane (MAO) gives polyethylene with vinyl, vinylidene and trans‐vinylene groups. The use of Al(iC4H9)3/(C6H5)3C · B(C6F5)4 as cocatalyst produces polyethylene predominantly containing trans‐vinylene groups. Polyethylene with vinyl end groups was obtained selectively with [(C5Me4)SiMe2N(t‐Bu)]TiCl2MAO as catalyst. The types and contents of CC double bonds in polyethylene markedly depend upon the metallocene compound as well as as the cocatalyst. In the copolymerizations the [(C5Me4)SiMe2N(t‐Bu)]TiCl2MAO catalyst system, on the other hand, gives poly[ethylene‐co‐(1‐octene)] with a high content of 1‐octene and a polyethylene containing an appreciable amount of long‐side‐chain oligoethylene.
Synthesis of degradable, biocompatible, and tough block‐copolyesterurethanes
Authors: Hirt Thomas D. , Neuenschwander Peter , Suter Ulrich W. 
Published: April 2003

AbstractWe describe the synthesis of micro‐phase‐segregated block‐copolyesterurethanes from telechelic hydroxyterminated poly{[(R)‐3‐hydroxybutyric acid]‐co‐[(R)‐3‐hydroxyvaleric acid]} (PHB‐diol) as “hard segments” (i. e., crystallizable chain sections) and hydroxyterminated poly(ε‐caprolactone)‐diethylene glycol‐poly(ε‐caprolactone) (PCL‐diol) or telechelic hydroxyterminated poly[(adipic acid)‐alt‐(1,4‐butanediol; diethylene glycol; ethylene glycol)] (Diorez®) as “soft segments”, with 2,2,4‐triethylhexamethylene diisocyanate (TMDI) or methyl (S)‐2,6‐diisocyanatohexanoate (LDI). High molecular weights were obtained with or without catalyst, the properties of the polymers depending only slightly on the presence or absence of the catalyst. The materials thus obtained were investigated also with respect to their mechanical properties and it was found that Young's modulus directly depends on the fraction of crystallizable PHB‐diol in the block copolymer while the type of non‐crystallizable segment or diisocyanate had only a minor influence: Generally, the tensile strength increases and the elongation at break decreases with increasing content of PHB‐diol. Around body temperature, these polymers exhibit only mild changes in their mechanical behavior. The chain length of the non‐crystallizable segment indirectly influences the morphology and the mechanical properties of the polymers through changes in the phase‐segregation behavior.
Kinetics of the reaction between alkaline sulfides and aryl dichlorides — model study on 4‐chloro‐ and 4,4′‐dichlorobenzophenones
Authors: Hedhli Lotfi , Lesclingant Christelle , Fradet Alain , Maréchal Ernest 
Published: April 2003

AbstractThe kinetics of the reaction between alkaline sulfides and halogenated aromatic monomers was studied using lithium sulfide and 4‐chlorobenzophenone (1a) and 4,4′‐dichlorobenzophenone (1b) as models. The release of H2S from reaction medium and the possible formation of a compound between sulfide and N‐methyl‐2‐pyrrolidone (NMP) during the preliminary dehydration step are key steps of the reaction. The reaction proceeds following two successive kinetic regimes: a first one where rapid second‐order reactions of sulfide and thiolate with 1a or 1b take place, and a second one where the slow release of sulfide from the compound formed during dehydration is rate determining and therefore governs the molecular weight of final polymer. A good agreement was found between theoretical curves calculated from this kinetic scheme and experimental data, indicating a polymerization mechanism based on an SNAr reaction mechanism.
Thermally induced radical promoted cationic polymerization using a novel N‐allyloxypyridinium salt
Authors: Reetz Ivo , Bacak Vildan , Yagci Yusuf 
Published: April 2003

AbstractA system consisting of a novel N‐allyloxypyridinium salt and a radical initiator is highly appropriate for the thermal initiation of cationic polymerizations. Radicals formed upon the thermolysis (at 70°C) of initiators as 2,2′‐azoisobutyronitrile or benzoyl peroxide add to the double bond of the pyridinium salt N‐[2‐(ethoxcarbonyl)allyloxy]‐α‐picolinium hexafluoroantimonate (1). Subsequently, the pyridinium salt is fragmented yielding pyridinium‐type radical cations, species able to initiate cationic polymerizations. In the case of the radical initiator phenylazotriphenylmethane (triphenylmethaneazobenzene), the polymerization is extremely rapid, since additionally the triphenylmethyl cation formed by electron transfer initiates the polymerization. The initiation capability of the system described was demonstrated for a number of monomers, such as cyclohexene oxide, butyl vinyl ether and the bifunctional 3,4‐epoxycyclohexylmethyl 3′,4′‐cyclohexanecarboxylate. With the latter, an insoluble polymer network was readily obtained.
Ring‐opening polymerization and copolymerization of a new benzylated 1,6‐anhydro‐3‐azido‐3‐deoxy‐β‐D‐allopyranose and synthesis of amino‐polysaccharides with 1,6‐α‐allopyranosidic structure
Authors: Hattori Kazuyuki , Yoshida Takashi , Uryu Toshiyuki 
Published: April 2003

AbstractRing‐opening polymerization of a new anhydro‐hexose monomer having an azido group, 1,6‐anhydro‐3‐azido‐2,4‐di‐O‐benzyl‐3‐deoxy‐β‐D‐allopyranose (A3ABA), was carried out with Lewis acid catalysts to give a stereoregular (1→6)‐α‐D‐allopyranan derivative having the azido group at the C3 position. The number‐average molecular weights and specific rotations were 5.0 × 103 to 24.0 × 103 and +71° to +79°, respectively. Reduction of the azido groups into amino groups by lithium aluminium hydride and subsequent debenzylation of the benzyl group into hydroxyl groups by sodium in liquid ammonia gave 3‐amino‐3‐deoxy‐(1→6)‐α‐D‐allopyranan in good yield. In addition, copolymerization of A3ABA with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (LGTBE) in the various feeds was carried out to afford the corresponding copolymers. The monomer reactivity ratios were calculated with the Kelen‐Tüdős method to be rA3ABA = 0.66 and rLGTBE = 1.67. After reduction of azido groups and deprotection of benzyl groups of the copolymers, new hetero‐polysaccharides having different contents of glucopyranose and 3‐amino‐allopyranose units were obtained.
Syntheses and properties of films from polymer gels based on polymer‐metal complexes
Authors: Bekturov Esen A. , Mamutbekov Galym K. 
Published: April 2003

AbstractFilms of poly(2‐vinylpyridine) (1), poly(allylamine hydrochloride) (2), poly(5‐methyl‐2‐vinylpyridine) (3) and poly(ethyleneimine) (4) with Ag+, Cu2+, Li+ and Ca2+ salts as well as complex transition metal ions [Fe(Cn)6]3− are prepared at the interface boundaries of immiscible solvents. The polymer/metal salt complexes exhibit highly ordered structures and high thermal stabilities as revealed by reduced viscosity, X‐ray diffraction, infrared spectrometry, thermogravimetry, differential thermal analysis as well as measurements of swelling coefficients and electroconductivity. Mole ratios of complex formation of the neat polymers as well as the polymer gels with these salts were found at [polymer] : [salt] = 1, 2, 3 and 4 referring to the repeating units of the polymers. It is suggested that the properties of the films are due to ionic bonds, ion‐coordination bonding, coordination bonds and ion‐dipole interactions between the functional groups of the polymeric hydro‐ and organic gels and the metal ions.
Aggregates of peptide‐containing block copolymers and their interactions with a lipase in aqueous solution
Authors: Naka Kensuke , Yamashita Rie , Nakamura Tohru , Ohki Akira , Maeda Shigeru , Aoi Keigo , Tsutsumiuchi Kaname , Okada Masahiko 
Published: April 2003

AbstractPeptide‐containing block copolymers poly(N‐acetyliminoethylene)‐block‐poly(L‐phenylalanine)s (1) form water‐soluble large aggregates in water due to the hydrophobic and hydrogen‐bonding nature of the poly(L‐phenylalanine) block. The solution properties were studied by size exclusion chromatography, dynamic light scattering, 1H NMR spectroscopy, and transmission electron microscopy. The results were compared with those of the block copolymers poly(N‐acetyliminoethylene)‐block‐poly(N‐benzoyliminoethylene)s (2) as analogous structures of poly(L‐phenylalanine). The peptide‐containing block copolymers 1 form aggregates in water even though only short segments of poly(phenylalanine) are provided. The hydrogen‐bonding character of the amide bond in the poly(phenylalanine) segment may induce strong interactions with each polymer chain in water. The interaction of Lipase P with the polymer aggregates in water was studied by means of size exclusion chromatography. The aggregates have a strong capability of incorporating Lipase P and largely increase the hydrolysis activity of Lipase P against p‐nitrophenyl propionate compared with free Lipase. The guest‐binding ability of 8‐anilino‐1‐naphthalenesulfonic acid for the polymer aggregates was also studied.
“Living” free radical polymerization of macromonomers: Preparation of well defined graft copolymers
Authors: Hawker Craig J. , Mecerreyes David , Elce Edmund , Dao Julian , Hedrick James L. , Barakat Ibrahim , Dubois Phillippe , Jérôme Robert , Volksen Willi 
Published: April 2003

AbstractWell defined graft copolymers have been synthesized by a nitroxide‐mediated “living” free radical process using pre‐formed macromonomers. Analysis of the graft systems revealed that the macromonomer was efficiently incorporated into the polymeric backbone to give block copolymers of controlled molecular weight and narrow polydispersities. An added benefit of the “living” free radical process is that macromonomers, such as polylactide or polycaprolactone, which contain reactive functional groups can be used to form novel graft systems using this approach. Functionalized monomers or polymeric initiators were also used in the copolymerization mixture to give graft systems with a variety of functional groups attached to the backbone.
Synthesis of poly[isobutyl (2S,3R)‐3‐benzyloxyaspartate]
Authors: García‐Martín María de Gracia , de Paz María Violante , Galbis Juan Antonio 
Published: April 2003

AbstractA chiral poly(3‐substituted isobutyl D‐aspartate) 12 was synthesized by polymerization of the chiral β‐lactam 11 derived from D‐glyceraldehyde. The new polyamide was characterized by elemental analyses, and infrared, 1H‐ and 13C nuclear magnetic resonance spectroscopies. The molecular weight was estimated as 543 000 and 230 000 on the basis of viscosimetric measurements and gel‐permeation chromatography, respectively. Polyamide 12 is soluble in a variety of organic solvents including chloroform.
Syntheses of polysiloxane‐supported zirconocene catalysts and application to ethene polymerization
Authors: Arai Takashi , Ban Hoang The , Uozumi Toshiya , Soga Kazuo 
Published: April 2003

AbstractPolysiloxanes with bisindenyl, bisfluorenyl, and bis(1,2,3,4‐tetramethyl)cyclopentadienyl side groups were synthesized by condensation of the corresponding dichlorosilane compounds and water to obtain supported ziroconocene catalysts. The polymerization of ethene was conducted over these catalysts combined with methylalumoxane. The polymerization activity depends markedly upon the substituents and decreases in the order: bisindenyl ≫ bisfluorenyl ≫ bis(1,2,3,4‐tetramethylcyclopentadienyl). All the supported catalysts give linear polyethene with fairly high molecular weights. The catalyst with bisindenyl groups was found to be composed of a toluene‐soluble and a toluene‐insoluble fraction. The polymerization profile (activity versus time curve) was analyzed with the toluene‐soluble and ‐insoluble fraction as well as the corresponding homogeneous system. The homogeneous system, which exerts the highest activity in the initial phase, was completely deactivated after several hours whereas the activity of the supported catalyst, especially of the toluene‐insoluble fraction, was unchanged during 12 h even at 70°C. Polysiloxanes with different content of bisindenyl groups were also synthesized via the co‐condensation with dimethyldichlorosilane and applied as the carrier. However, the activity per Zr atom decreases remarkably with an increase in dimethylsilane units.
Step growth polymerization via tandem ene and diels‐alder reactions
Authors: Mallakpour Shadpour E. , Kolshorn Heinz , Schollmeyer Dieter , Stadler Reimund 
Published: April 2003

AbstractIn contrast to other electron deficient enophiles or dienophiles which react with 1,4‐cyclohexadiene (1,4‐CHD) under aromatization, 1,2,4‐triazoline‐3,5‐diones react in a defined reaction sequence. In a first step the 1,4‐cyclohexadiene reacts via an ene‐reaction. The intermediately formed substituted 1,3‐cyclohexadiene immediately reacts in a Diels‐Alder reaction. The regiochemistry of the Diels‐Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low‐molarmass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are available.
Block copolymerization of triphenylmethyl methacrylate with other methacrylates using (−)‐sparteine/9‐fluorenyllithium as an initiator
Authors: Liu Weihong , Yang Yonghong , Chen Chuanfu , Chen Yongming , Xi Fu 
Published: April 2003

AbstractDiblock and triblock copolymerization of triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), butyl methacrylate (BuMA), benzyl methacrylate (BzMA) or diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator, (−)‐sparteine/9‐fluorenyllithium, were investigated. The resulting block copolymers show high specific rotation and were characterized by means of gel‐permeation chromatography, scanning electron microscopy, nuclear magnetic resonance, circular dichroism spectra and thermal analysis.
Thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)propane carbonate]: A reinvestigation
Authors: Berti Corrado , Bonora Virna , Fiorini Maurizio , Pilati Francesco , Sweileh Bassam 
Published: April 2003

AbstractThe final product of the thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)‐propane carbonate] (polymer 1) at 280°C under vacuum was characterized as a random copolymer containing both ether and carbonate groups and not as pure bisphenol A polycarbonate as reported previously by other authors. Infrared and NMR spectroscopy were used to detect the changes of the polymer structure during the thermal treatment; the resulting polymers were also characterized by measuring their intrinsic viscosity. During the thermal treatment different reactions occur: exchange reactions (which would lead to a random copolycarbonate), and intramolecular elimination of ethylene carbonate and carbon dioxide. This last elimination is responsible for the formation of ether groups which, being stable under the reactions conditions, prevent the complete elimination of the aliphatic moieties. The final random copolymer was also prepared by reacting pure bisphenol A polycarbonate (PC) and ethylene carbonate; this confirms the occurrence of exchange reactions, which lead to a random copolycarbonate having a structure similar to the polymer deriving from polymer 1. Surprisingly, in the presence of a typical exchange reaction catalyst such as dibutyltin dimethoxide or titanium tetrabutoxide, the final product of the thermal treatment of polymer 1 is pure PC.
Polymers from multifunctional isocyanates, 12. Alternating copolymers from isocyanatoalkenes and electron deficient 1,2‐disubstituted alkenes
Authors: Mormann Werner , Schmalz Kerstin , Grimm Axel 
Published: April 2003

AbstractThe free radical copolymerization of the electron rich monomers vinyl isocyanate, isopropenyl isocyanate, trans‐1‐propenyl isocyanate, and trans‐β‐styryl isocyanate with maleic anhydride has been investigated. The copolymerization behaviour of different electron deficient monomers like maleic anhydride, citraconic anhydride, N‐phenylmaleimide and fumaronitrile with isopropenyl isocyanate or vinyl isocyanate has also been studied. Polymerization in benzene is accompanied by precipitation of polymer, while the polymerization proceeds in solution in 2‐butanone. Alternating copolymers were obtained in all cases. The alternating behaviour is favoured by the very low tendency of all monomers except maleimides to undergo homopolymerization. From the reaction with maleic anhydride the reactivity of electron donating monomers was found to be vinyl isocyanate ≈ isopropenyl isocyanate ≫ β‐styryl isocyanate ≈ ≫ 1‐propenyl isocyanate, while the reactivity of electron accepting monomers with isopropenyl isocyanate was: maleic anydride > N‐phenylmaleimide > fumaronitrile.
New monomers and photosensitive polymers: the synthesis and polymerization of 2‐, 3‐ and 4‐vinylphenyl thiocyanate
Authors: Kern Wolfgang , Hobisch Josefine , Hummel Klaus 
Published: April 2003

AbstractThe new monomers 2‐vinylphenyl thiocyanate (6a), 3‐vinylphenyl thiocyanate (6b) and 4‐vinylphenyl thiocyanate (6c) were prepared from 2‐, 3‐ and 4‐aminoacetophenone (1a–c) as starting materials. The homopolymers (7a–c) and the copolymers 8a–c of the monomers 6a–c with styrene were prepared via free radical polymerization. The polymers, which were obtained as fully soluble and stable materials, were sensitive to UV light. The crosslinking of the polymers 7a–c and 8a–c was investigated under 254 nm UV radiation. From the sensitivity curves of the polymers, gel doses Eg between 2,6 and 95 mJ · cm−2 were derived.
Transmission electron microscopy of free standing thin films of poly(ether ether ketone)
Authors: Plummer Christopher John George , Kausch Hans‐Henning 
Published: April 2003

AbstractFree standing thin films of poly(ether ether ketone) crystallized in situ by heating from the glassy state have been shown to be suitable for high resolution transmission electron microscopy lattice imaging. Films mounted on coarse‐mesh copper grids could also be observed in the deformed state, allowing lattice imaging of regions of strain induced crystallization at temperatures in the neighbourhood of the glass transition temperature.
Influence of configuration upon heterogeneity in anisotropic glasses as determined by thermally stimulated current
Authors: Liu Shur‐Fen , Lee Yu‐Der 
Published: April 2003

AbstractThermally stimulated current (TSC) as well as differential scanning calorimetry (DSC) was used to determine the glass transition temperature of anisotropic glasses for semiflexible polyesters with polymethylene spacers. The highly sensitive technique of thermal‐windowing polarization or relaxation map analysis (RMA) was used to further study the relaxation behavior of the anisotropic glasses as well as the heterogeneity of the samples. Experimental results indicate that phase separation is dependent upon the length of the polymethylene chain, i.e., the configuration of polymethylene segments and the number (n value) of methylene groups. The longer the polymethylene segment the larger the difference in the two transition temperatures, the higher transition temperature (Tg,H) and lower transition temperature (Tg,L). For a polymer with even value of n, ΔTg (Tg,H minus Tg,L) of the anisotropic glass is lower than that for the neighboring two polymers with odd n values. In addition, the distortion effect of the polymethylene segment with even number of methylene groups on the polymer chains under polarization was studied by the Vogelian relaxation behavior of the ρ‐peak. These results indicated that the maximum fractional volume of the polymethylene segments of the anisotropic glass for a polymer with even n value would be smaller than that for a polymer with odd n value under polarization.