bluuebunny/crossref_metadata_2025 huggingface dataset:
Copolymerization of 3,3,3‐trifluoro‐1,2‐epoxypropane with N‐phenylmaleimide using organozinc initiators
Authors: Ikeda Yoji , Yoshida Yasuhiko , Ishihara Kenji , Hamana Hiroshi , Narita Tadashi , Hagiwara Tokio
Published: April 2003

Novel copolymers consisting of 3,3,3‐trifluoro‐1,2‐epoxypropane (TFEP) and N‐phenylmaleimide (PMI) units were prepared by the copolymerization of TFEP with PMI initiated with an organozinc compound. Using [Zn(OCH3)2 · (C2H5ZnOCH3)4] as an initiator, the copolymer chains consisted mainly of TFEP‐TFEP sequences. The TFEP‐PMI sequence content in the copolymer chains was small. On the other hand, using (C2H5ZnOCH3)4 as an initiator, only low molecular weight copolymers were formed. Those copolymers were suggested to have block structure, poly(TFEP)‐block‐poly(PMI), by the 19F NMR analysis. The copolymers showed higher thermostability than poly‐(TFEP).
Propene polymerization catalyzed over MCM‐41 and VPI‐5‐supported Et(ind)2ZrCl2 catalysts
Authors: Ko Young Soo , Han Taek Kyu , Park Je Woo , Woo Seong Ihl
Published: April 2003

Et(ind)2ZrCl2 (C2H5(indenyl)2ZrCl2) confined inside regular pores of molecular sieves MCM‐41 and VPI‐5 were prepared and used to polymerize propene with high activity. Stereoregularity, melting point and molecular weight of polypropene obtained were increased and the polymerization behavior was quite different from that prepared with homogeneous Et(ind)2ZrCl2. The small, regular and cylindrical pores of MCM‐41 and VPI‐5 suppress the formation of inactive binuclear complexes between metallocene and metallocene, or between metallocene and methylaluminoxane, resulting in stable active sites and high activity in propene polymerization.
Synthesis and photocrosslinking of maleimide‐type polymers
Authors: Kim Woo‐Sik , Seo Kwan‐Ho , Chang Won‐Suk
Published: April 2003

Self‐sensitizable photocrosslinking maleimide‐type polymers were synthesized by using (N‐cinnamoyloxymethyl)maleimide (1) as a maleimide having a photodimerizable group, nitrophenyl acrylate as a sensitizer monomer, and styrene or methyl acrylate. The fluorescence spectra of these polymers exhibit an excimer band around 455 nm. The excimer intensity of the polymers decreased mainly during the early irradiation time. This decreasing tendency was similar to the increasing tendency of the insoluble fractions of the polymers with irradiation time. These results suggest that the photocrosslinking reaction of the polymers occurs via an excimer formation of the cinnamoyl groups and can be traced by fluorescence spectroscopy.
Water soluble, conjugated main chain azo polymer: Synthesis and characterization
Authors: Balasubramanian Srinivasan , Kim Jaehyun , Yu Kim Dong , Kumar Jayant , Tripathy Sukant K.
Published: April 2003

The monomer 2,5‐diaminobenzenesulfonic acid has been polymerized to a high molecular weight, conjugated main chain azo polymer. The presence of the azo group in the polymer was confirmed using Raman spectroscopy. The polymer is highly soluble in water over a wide pH range. It is also soluble in common polar organic solvents such as N,N‐dimethylformamide, dimethyl sulfoxide and N‐methyl‐2‐pyrrolidone.
Biochemical synthesis of water soluble polyanilines: Poly(p‐aminobenzoic acid)
Authors: Alva K. Shridhara , Marx Kenneth A. , Kumar Jayant , Tripathy Sukant K.
Published: April 2003

This report describes the synthesis of a water soluble polyaniline through a biochemical synthetic route. The oxidative free radical coupling mechanism for the synthesis of poly(p‐aminobenzoic acid) is catalyzed by horseradish peroxidase in the presence of hydrogen peroxide. The resulting polymer is electrochemically active and undergoes reversible redox reactions. The polymer as synthesized is self doped and undergoes undoping in alkaline or ammonia solutions.
Living ring‐opening polymerization of cyclic carbonate using cationic zirconocene complex as catalyst
Authors: Hayakawa Michiya , Mitani Makoto , Yamada Tohru , Mukaiyama Teruaki
Published: April 2003

Living ring‐opening polymerization of the cyclic carbonate 1,3‐dioxepan‐2‐one was achieved by using the cationic zirconocene complex [Cp2ZrMe]+[B(C6F5)4]− as catalyst at room temperature. A linear relation between conversion and molecular weight of the obtained polymer was observed. Furthermore, block copolymerization of the cyclic carbonate and ε‐caprolactone was successfully performed.
Optimum measurement temperature for elucidating incomplete phase separation in core‐shell latexes by solid state NMR
Authors: Landfester Katharina , Spiess Hans‐Wolfgang
Published: April 2003

Core‐shell latexes with a core of poly(buty1 acrylate) (PBuA) and a shell of poly(methyl methacrylate) were studied by solid‐state nuclear magnetic resonance (NMR) methods at different temperatures. 13C cross polarization/magic angle spinning spectra show differences in mobility in the mobile PBuA phase. In spin‐diffusion experiments the sensitivity of the NMR parameters towards the interphase structure and towards the entire core‐shell structure changes with varying temperature. For an efficient characterization of interphase structures in core‐shell systems the measuring temperature has to be optimized, i.e. the mobility gradient between the two phases within the particle must be sufficiently high to allow for effective selection by the dipolar filter. Yet, the spin diffusion coefficient of the mobile component should be high enough to allow quantitative evaluation of length scales. It is shown that a measuring temperature of about 60–70 K above the glass transition temperature of the mobile component represents an optimum for fulfilling the different requirements simultaneously.
MALDI‐TOF characterization of macromonomers
Authors: Spickermann Jochen , Räder Hans‐Joachim , Müllen Klaus , Müller Beate , Gerle Markus , Fischer Karl , Schmidt Manfred
Published: April 2003

Methacryloyl endfunctionalized oligostyrene macromonomers were characterized by matrix assisted laser desorption ionization/time of flight (MALDI‐TOF) spectroscopy and by isocratic and gradient high performance liquid chromatography (HPLC). The molar mass distribution derived by the different techniques coincide for the investigated oligomers. Mixing experiments revealed that the MALDI‐TOF peak areas do not necessarily represent the mixing ratio of the components. Combination of gradient HPLC and MALDI‐TOF has resolved the chemical composition of the coupling products formed by reaction of the living anion with oxygen.
Synthesis, characterization and properties of a soluble polymer with a poly(phenylenevinylene) structure
Authors: Babudri Francesco , Cicco Stefania R. , Farinola Gianluca M. , Naso Francesco , Bolognesi Alberto , Porzio William
Published: April 2003

Soluble poly(2,5‐dialkoxy‐1,4‐phenylenevinylene) has been prepared via Stille coupling reaction between 2,5‐dialkoxy‐1,4‐diiodobenzene and E‐1,2‐bis(tributylstannyl)‐ethene in the presence of palladium complexes. Characterization of this material by means of 1H and 13C nuclear magnetic resonance (NMR), ultraviolet/visible (UV/VIS) and infrared (IR) spectra is described. Molecular weights, determined by means of gelpermeation chromatography (GPC) analysis and referred to standard polystyrene, were in the range number‐average molecular weights Mn = 2061–2544 and weight‐average molecular weights Mw = 3347–3878. X‐ray diffraction (XRD) analysis of the polymer showed semicrystalline structure. Tg = 57°C, transition to a stable smectic mesophase at 115°C and clearing point at 210°C were revealed by differential scanning calorimetry analysis, optical microscopy observation and XRD of the annealed polymer.
Sequence control on the ring‐opening oligomerization of cyclic imino ethers
Authors: Aoi Keigo , Okada Masahiko , Miyamoto Masatoshi
Published: April 2003

Sequence‐controlled oligomers of cyclic imino ethers were synthesized by the one‐pot multi‐stage feeding method. Selective formation of the sequence was clearly demonstrated by equimolar reactions between the monomers and 1:1 adducts of an initiator with the monomers. Efficiency of the sequence control is determined by the difference of reactivities of the active ends. A new general prerequisite to synthesize a well‐defined sequence by multi‐stage oligomerization was proposed.
Relationship between molecular structure and thermal properties of poly(aryl ether ketone)s
Authors: Shibata Mitsuhiro , Yosomiya Ryutoku , Wang Junzuo , Zheng Yubin , Zhang Wanjin , Wu Zhongwen
Published: April 2003

Five kinds of poly(aryl ether ketone)s (PAEKs) having para‐substituted linear molecular chains were synthesized via nucleophilic substitution reaction of the corresponding difluoro‐ and dihydroxy‐compounds. The glass transition temperature and melting temperature of the PAEKs measured through differential scanning calorimetry in addition to those of other PAEKs reported are approximately proportional to the logarithm of the ratio of the mole fractions of ketone and ether groups in the repeating unit of the PEAKs. On the other hand, this ratio does not affect the crystal structure of the PAEKs.
Mechanistic study of enzyme catalyzed polymerization of 8‐hydroxyquinoline‐5‐sulfonate using nuclear magnetic resonance spectroscopy
Authors: Alva K. Shridhara , Marx Kenneth A. , Kumar Jayant , Tripathy Sukant K.
Published: April 2003

Horseradish peroxidase catalyzed polymerization of 8‐hydroxyquinoline‐5‐sulfonate (HQS) has been studied by in‐situ NMR spectroscopy. The 2, 4 and 7 positions of the HQS are involved in oxidative free radical coupling with other HQS molecules with the order of reactivity being 7 ≥ 2 > 4. A mechanism for the oxidative free radical coupling and structure of the resulting polymer is proposed, which is supported by 13C NMR spectroscopy.
Synthesis and polymerization of N,N‐diallylpyrrolidinium bromide
Authors: De Vynck Valérie , Goethals Eric J.
Published: April 2003

The synthesis of N,N‐diallylpyrrolidinium bromide (DAPB) and its free‐radical initiated polymerization are described. It is shown that DAPB polymerizes via a cyclopolymerization mechanism leading to a polyelectrolyte consisting of azoniaspiro[4.4]‐nonane containing repeating units.
Immobilization of trypsin in polycation‐polyanion complexes
Authors: Dautzenberg Herbert , Karibyants Natalia , Zaitsev Sergei Yu.
Published: April 2003

Trypsin was immobilized in quasi‐soluble polyanion‐polycation complexes with retention of the enzyme activity. The activity of the immobilized enzyme strongly depends on pH of the prepared solution, composition, relative concentrations and molar masses of the polyelectrolytes. The highest activity of trypsin (about 93%) was found in the case of the complexes Na‐poly(styrenesulfonate)‐poly(diallyldimethylammonium chloride): trypsin = 10:1, prepared at pH 3.0, with high molar mass of the polyanion (about one million). This method can be proposed for immobilization of various serine proteases.
Ruthenium catalyzed polymerization of 4‐acetylstilbenes and 1,3‐divinyltetramethyldisiloxane
Authors: Londergan Timothy Martin , Weber William P.
Published: April 2003

Successful dihydridocarbonyltris(triphenylphosphine)ruthenium (Ru‐complex) catalyzed polymerization of 4‐acetylstilbene with 1,3‐divinyltetramethyldisiloxane to yield poly(3,3,5,5‐tetramethyl‐4‐oxa‐3,5‐disila‐1,7‐heptanylene‐alt‐4‐acetyl‐3,5‐stilbenylene) is reported. Polymerization results from Ru‐complex catalyzed activation of aromatic C‐H bonds which are ortho to the acetyl for selective anti‐Markovnikov addition across the terminal C‐C double bonds of 1,3‐divinyltetramethyldisiloxane. The internal C‐C double bond of 4‐acetylstilbene does not react.
Synthesis of a novel poly[2]‐catenane containing rigid catenanes
Authors: Muscat Dirk , Witte Andreas , Köhler Werner , Müllen Klaus , Geerts Yves
Published: April 2003

A novel poly[2]‐catenane containing rigid catenane subunits connected by semirigid spacers has been synthesized. This new macromolecular architecture is the second example of a polymer containing topological bonds in the main chain. The poly[2]‐catenane structure was proved by spectroscopic methods, especially 1H NMR, IR and MALDITOF. The polymer is thermally stable up to 380°C and shows a high glass transition temperature of ca. 265°C.
1,3,5,5‐tetraphenyl‐Δ3‐1,2,4‐triazolin‐2‐yl radical–properties in the controlled radical polymerization of poly(methyl methacrylate) and polystyrene
Authors: Colombani Daniel , Steenbock Marco , Klapper Markus , Müllen Klaus
Published: April 2003

The triazoline derivative 1 was used as an additive in the chain‐growth controlled radical polymerization of vinylic monomers to afford narrowly distributed polymers. This new system is applicable to styrene as well as to methacrylates. The monomer consumption and the variation of the molar mass were monitored with time. Thermal properties of the obtained polymers were also studied. After isolation of the polymers, the growth of the chains was re‐initiated in the presence of a second monomer and yielded block copolymers.
Synthesis and surface characterization of a new multiblock copolymer based on poly(dimethylsiloxane) and aromatic polysulfone
Authors: Di Pasquale Giovanna , La Rosa Angela , Mamo Antonino
Published: April 2003

A new alternating block copolymer was synthesized from dihydroxy‐terminated poly‐(ether ketone sulfone) and bis(dimethylamino)‐terminated polydimethylsiloxane oligomers. The chemistry and the thermal properties are discussed. Surface chemical composition of films was analyzed by ESCA. Quantitative calculations showed a noticeable siloxane enrichment at the surface.
Preparation of new poly(ester‐imide)s with cyanoazobenzene side chains generating optical phase‐conjugate signals
Authors: Sato Moriyuki , Nakagawa Kazuo , Tada Yuji , Ujiie Seiji
Published: April 2003

New semi‐rigid poly(ester‐imide)s with cyanoazobenzene side chains were prepared by melt polycondensation of a diethyl isophthalate derivative of cyanoazobenzene with N, N′‐dihexanols of five aromatic diimides in the presence of zinc acetate. Differential scanning calorimetry (DSC) measurements and polarizing microscope observations demonstrated that the polymers have glass transitions (Tg) between 46 and 93°C and show no liquid crystalline (LC) properties. All poly(ester‐imide)s generated optical phase‐conjugate (PC) signals at high reflectivity by degenerate four‐wave mixing (DFWM) at low pump‐beam power.
Intermolecular chain transfer to polymer with chain scission: general treatment and determination of kp/ktr in L,L‐lactide polymerization
Authors: Baran Jolanta , Duda Andrzej , Kowalski Adam , Szymanski Ryszard , Penczek Stanislaw
Published: April 2003

A general kinetic treatment of the system with intermolecular chain transfer followed by fast reinitiation is given. It leads to the broadening of the molecular weight distribution (MWD), the number of growing chains being invariable. Thus, this system can be considered as a special case of living polymerization. A general method has been elaborated allowing the determination of the ratio of the rate constant of propagation (kp) to the rate constant of the bimolecular transfer (k(2)tr) from the dependence of the MWD on monomer conversion. Numerical values of kp/k(2)tr equal to ≈ 102 and 25 were thus determined for the polymerization of L, L‐lactide (L, L‐dilactide) initiated with aluminium tris(isopropoxide) trimer ({Al(OiPr)3}3) and tributyltin ethoxide (nBu3SnOEt), respectively.
Novel core‐shell type thermo‐sensitive nanoparticles composed of poly(γ‐benzyl L‐glutamate) as the core and poly(N‐isopropylacrylamide) as the shell
Authors: Cho Chong‐Su , Cheon Jae‐Bok , Jeong Young‐Il , Kim In‐Sook , Kim Sung‐Ho , Akaike Toshihiro
Published: April 2003

AB diblock copolymers consisting of PBLG as the hydrophobic part and PNIPAAm as the hydrophilic one were prepared by polymerization of BLG‐NCA with semitelechelic PNIPAAm with amino end group as initiator. The core‐shell type nanoparticles of the block copolymers were obtained by the diafiltration method. The sizes of the nanoparticles were from about 73 to 359 nm and the shapes of them were spherical. The release for indomethacin (IN) from the nanoparticles was faster at 28°C than at 34°C due to the conformational change of PNIPAAm by temperature.
Electron transfer between two stable radicals
Authors: Zheng Haipeng , Zhang Ruifeng , Dong Fengxia , Zheng Yingguang , Shen Jiacong
Published: April 2003

Electron spin resonance (ESR) is a sensitive tool to detect the electron‐transfer processes in some specified systems from the change of the ESR signals. In this paper, the interaction between poly(N,N‐dimethylaniline) (PDMA) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) was investigated by ESR spectra based on the stability of their radicals in ethanol. It is shown that an electron‐transfer process occurs from nitrogen atoms of PDMA molecules to those of DPPH molecules which makes PDMA form more stable radical cations and eliminates the radicals on DPPH.
Synthesis and characterization of star‐shaped polytetrahydrofuran
Authors: Van Caeter Peter , Goethals Eric J.
Published: April 2003

Star polymers of tetrahydrofuran (polyTHF) were prepared by reaction of living polyTHF with diethylene triamine (DETA) in the presence of 2,2,6,6‐tetramethylpiperidine (TMP) as proton trap. The influence of several reaction parameters on the end‐capping reaction was studied in order to produce stars having varying number of arms. With a starting living polyTHF with a molecular weight of 1600, star‐shaped polymers containing up to seven polymer chains could be prepared. When the molecular weight of the living polyTHF was 8000, at most five polymer chains could be grafted on the DETA. Some physical properties of the star polymers were compared with those of their linear counterparts of the same molecular weight.
Efficient synthesis and facile polymerization of some cyclic bisphenol o‐phthalates
Authors: Jiang Hongyan , Chen Tianlu , Xu Jiping
Published: April 2003

A series of new macrocyclic aromatic esters have been efficiently synthesized from o‐phthaloyl dichloride and various bisphenols, and unambiguously characterized by a combination of GPC, MS(FAB), FTIR and NMR. These macrocyclic oligomers undergo facile ring‐opening polymerization in the presence of anionic initiators to give high molecular weight polyarylates.
Synthesis of linear and three‐arm star tert‐chlorine‐telechelic polyisobutylenes by a two‐step conventional laboratory process
Authors: Feldthusen Jesper , Iván Béla , Müller Axel H. E. , Kops Jørgen
Published: April 2003

A two‐step conventional laboratory process was developed for the synthesis of mono‐ and difunctional linear and three‐arm star tert‐chlorine‐telechelic polyisobutylenes (PIB) with desired molecular weights (MW) and narrow molecular weight distribution (MWD) by living carbocationic polymerization (LCCP). This polymerization method applies easy to handle operations and chemicals. LCCP of isobutylene (IB), was carried out in CH2Cl2 as solvent and with BCl3 as coinitiator in the first step to obtain soluble low MW PIB prepolymer with narrow MWD. This was followed by addition of hexane, TiCl4 and additional monomer in the second step to prepare PIBs with desired MW and narrow MWD in practically any suitable MW region. Comparison of the one‐step and two‐step processes is also described.
Cyclic carbonates, novel expandable monomers on polymerization
Authors: Takata Toshikazu , Sanda Fumio , Ariga Toshiro , Nemoto Hideo , Endo Takeshi
Published: April 2003

A variety of cyclic carbonates was shown to undergo volume expansion on polymerization. The degree of volume expansion, which was measured by the density gradient tube method, was ranging from 1.1% to 7.7%. The volume expansion was examined by assuming a change in molecular interaction such as dipole moment between monomer and polymer states.
Preparation of monodisperse polymer particles from 4‐vinylpyridine
Authors: Takahashi Kazuhiko , Miyamori Shigeo , Uyama Hiroshi , Kobayashi Shiro
Published: April 2003

Dispersion polymerization of 4‐vinylpyridine was performed by using polystyrene‐block‐polybutadiene as stabilizer in a mixture of N,N‐dimethylformamide (DMF) and toluene to produce polymer particles. The weight ratio of the solvents affects the particle size and dispersity. In the range of DMF content from 5 to 20 wt.‐%, uniform particles of a diameter of ca. 1 μm were obtained. The present system was expanded to the preparation of monodisperse particles of poly[(4‐vinylpyridine)‐co‐(methacrylic acid)].
Synthesis of polysilanes by reductive coupling of dichlorosilanes mediated with alkali metal/crown ether supramolecular complexes in a homogeneous system
Authors: Jedliński Zbigniew J. , Kurcok Piotr , Nozirow Farhod
Published: April 2003

Structure and properties of poly(methylphenylsilane) synthesized by reductive coupling of silyl halides with alkali metal supramolecular complexes: (Mt+/18‐crown‐6, Mt−, where Mt = K, Na; 18‐crown‐6 = 1,4,7,10,13,16‐hexaoxacyclooctadecane) were investigated. The coupling process yields polymers exhibiting narrow molecular weight distribution and number‐average molecular weights up to 8 500, cyclic oligomers being formed along with linear ones.
Synthesis and properties of hydrophilic polymers, 6. Water‐soluble polypyrrole graft copolymers with electrical conductivity
Authors: Geckeler Kurt E. , Arsalani Nasser , Rivas Bernabé L.
Published: April 2003

A novel method for the preparation of water‐soluble polypyrrole graft copolymers with polyamines or polyimines is described. The polyreaction is performed in acidic solution by using chemical oxidants, e.g. iron(III) chloride or ammonium peroxodisulfate. The graft copolymers showed electrical semiconductivity in the undoped state which can be placed between the high conductivity of polypyrrole and the nonconductivity of the polyimine. Their thermal stability at 250°C is improved compared to polypyrrole. The novel graft copolymers are soluble in water over a wide pH range and have a good processability.
A new approach for the fabrication of an alternating multilayer film of poly(4‐vinylpyridine) and poly(acrylic acid) based on hydrogen bonding
Authors: Wang Liyan , Wang Zhiqiuang , Zhang Xi , Shen Jiacong , Chi Lifeng , Fuchs Harald
Published: April 2003

A new approach for the fabrication of a multilayer film assembly is explored, which is based on the alternating assembling of poly(4‐vinylpyridine) and poly(acrylic acid) via hydrogen bonding. The homogeneous multilayer films were characterized by UV‐Vis, X‐ray diffraction and atomic force microscopy (AFM) measurements. The nature of interaction between the two polymers is identified as hydrogen bonding by IR spectroscopy.
Interfacial tension of demixed polymer solutions: augmentation by polymer additives
Authors: Schneider Anja , Wolf B. A.
Published: April 2003

The interfacial tension between phase separated polymer solutions increases pronouncedly upon the addition of small amounts of incompatible polymers. This feature is demonstrated by means of measurements with solutions of polystyrene in cyclohexane and the following additives: poly(styrene‐block‐dimethylsiloxane), polyisobutylene and polydimethylsiloxane. Theoretical considerations based on a correlation between the lengths of tie lines and the corresponding interfacial tension corroborate this finding.
Composites 3. Reinforcement of biodegradable matrices by helical polypeptides
Authors: Kricheldorf Hans R. , Wahlen Lars , Chen Khezi
Published: April 2003

Blends of poly(ε‐caprolactone) as the matrix material and 1,2,4, or 8 wt.‐% of a poly‐peptide were prepared by dissolution in a cosolvent and coprecipitation into cold methanol. A low‐and a high‐molecular‐weight poly(γ‐benzyl L‐glutamate), a poly(γ‐methyl L‐glutamate) and a poly(D,L‐phenylalanine) were used as reinforcing components and compared with a liquid‐crystalline (LC) polyester derived from a double‐substituted terephthalic acid. Films of all blends were subjected to stress‐strain measurements. A weak reinforcing effect was found for the poly(γ‐benzyl L‐glutamate)s, a somewhat stronger influence for the other polypeptides and the strongest effet for the LC‐polyesters 1.
Deorientation effects on extrusion rheometry of a thermotropic copolyester
Authors: Tormes Marta , Muñoz María Eugenia , Santamaría Anton
Published: April 2003

Extrusion rheometry experiments with a commercial thermotropic liquid crystalline copolyester show concave Bagley plots and convex pressure profiles. A loss of the orientation produced at the entrance of the capillary and the slit can explain these non‐linearities. Assuming that the order parameter, S, relaxes exponentially with time, the Doi‐Edwards model for the shear flow of rod‐like polymers is used to adjust experimental data.
Studies towards a tailor‐made catalyst for the Diels‐Alder reaction using the technique of molecular imprinting
Authors: Liu Xiao‐Chuan , Mosbach Klaus
Published: April 2003

A tailor‐made catalytically active polymer catalyzing the bimolecular Diels‐Alder reaction is described. Kinetic studies carried out in acetonitrile at 82°C show a 270‐fold rate acceleration (kcat/kuncat) for the Diels‐Alder reaction between tetrachlorothiophene dioxide and maleic anhydride. The imprinted polymer induces Michaelis‐Menten kinetics, with an apparent Km of 42.5 mM and an apparent kcat of 3.82 × 10−2 min−1, respectively. Substrate selectivity, accessible binding site analysis, dissociation constant determination, and inhibition study were also performed.
Polyolefins with high glass transition temperatures
Authors: Henschke Olaf , Köller Frank , Arnold Manfred
Published: April 2003

The copolymerization of propene and norbornene with the isospecific metallocene catalyst dimethylsilylenebis(η5‐inden‐1‐yl)zirconium dichloride/methylaluminoxane ((CH3)2Si[Ind]2ZrCl2/MAO) was investigated. Because of the surprisingly high reactivity of the cyclic olefin copolymers with a norbornene content of 11 mol‐% up to 98 mol‐% were synthesized. The resulting copolymers are amorphous. The glass transition temperatures studied by differential scanning calorimetry measurements increase with rising norbornene content in the copolymer. High glass transition temperatures of Tg > 240°C were found for the copolymers with the highest content of norbornene.
Ethylene polymerizations with novel tantalum(V) aminopyridinato complex/MAO systems
Authors: Hakala Kimmo , Löfgren Barbro , Polamo Mika , Leskelä Markku
Published: April 2003

The use of two kinds of tantalum(V) aminopyridinato complexes, bis(2‐benzylaminopyridinato)trichlorotantalum(V) and trichlorobis[2,6‐di(phenylamino)pyridinato‐N,N′]‐tantalum(V), activated by methylaluminoxane was studied in polymerization of ethylene. The activities of these homogeneous catalyst systems are comparable to those of metallocenes. The weight‐average molecular weights (M̄w) of the produced polyethylenes are between 60 000 and 200 000 and M̄w/M̄n ≈ 2.
Vinylic polymerization of norbornene by Pd(II)‐catalysis in the presence of ethylene
Authors: Haselwander T. F. A. , Heitz W. , Maskos M.
Published: April 2003

Pd(II) catalysts with nitrilo ligands and BF4− counter ions give the best results in vinylic polymerization of norbornene. Absolute molecular weight determination of polynorbornene (PN) by means of light scattering and the three‐dimensional shape of PN were also investigated. By correlation of molecular weights M̄w with intrinsic viscosity (Staudinger‐index) [η], yield a close to 0.5 exponent for the Mark‐Houwink equation with solvents chlorobenzene and cyclohexane at 25°C expected for polymer molecules with confined conformation. The vinylic polymerization of norbornene with [(CH3CN)4Pd][BF4]2 (I) in nitromethane in the presence of ethylene results in PN with narrow molecular weight distribution. No termination and transfer reactions were found, nor any incorporation of ethylene could be detected.
Effect of crystal‐disrupting chlorohydroquinone on the first‐order transitions of poly(aryl ether ketone)s containing biphenyl units
Authors: Zhang Shanju , Zheng Yubin , Wu Zhongwen , Tian Mingwen , Yang Decai , Yosomiya Ryutoku
Published: April 2003

The novel poly(aryl ether ketone)s were synthesized by nucleophilic substitution reactions of 4,4′‐difluorobenzophenone with 4,4′‐biphenyldiol and chlorohydroquinone. As expected, the copolymers have lower melting transitions than the biphenyldiol‐based homopoly(aryl ether ketone) because of the copolymerization effect of the crystal‐disrupting monomer chlorohydroquinone. Copolymers containing 50 and 70% biphenyldiol show two first‐order transitions which are associated with the crystal‐to‐liquid crystal transition and the liquid crystal‐to‐isotropic transition.
[η3‐methallyl‐nickel‐dad]PF6 complex: new catalyst precursor for ethylene polymerization
Authors: De Souza Roberto‐F. , Mauler Raquel S. , Simon Leonardo C. , Nunes Fernanda F. , Vescia Daniela V. S. , Cavagnolli Alessandro
Published: April 2003

The complex [η3‐methallyl‐nickel‐dad]PF6 is a new catalyst precursor for ethylene polymerization. The system is active in the presence of usual organoaluminium compounds like diethylaluminium chloride, at low Al/Ni ratios and under mild reaction conditions (temperatures between −10°C and 25°C, ethylene partial pressure from 1 to 15 atm). The polymers show extensive methyl branching, whose content is controlled by reaction parameters like temperature and ethylene pressure.
Hyperbranched methacrylates by self‐condensing group transfer polymerization
Authors: Simon Peter F. W. , Radke Wolfgang , Müller Axel H. E.
Published: April 2003

The synthesis of hyperbranched methacrylates was achieved by self‐condensing group transfer polymerization of 2‐(2‐methyl‐1‐triethylsiloxy‐1‐propenyloxy)ethyl methacrylate (1). “Back‐biting” is shown to be the predominant side reaction. In spite of this, the compact nature of the hyperbranched molecules was demonstrated through SEC‐viscosity measurements and comparison with a linear analogue. The degree of branching can be controlled by copolymerization with conventional monomers, e.g. MMA, and the living polymers can be used as macroinitiators for star‐shaped polymers.
Transition metal catalyzed atom Transfer Radical Polymerization (ATRP): from heterogeneous to homogeneous catalysis using 1,10‐phenantroline and its derivatives as new copper(I) ligands
Authors: Destarac Mathias , Bessière Jean‐Marie , Boutevin Bernard
Published: April 2003

Atom Transfer Radical Polymerization (ATRP) of styrene is investigated in both heterogeneous and homogeneous media using 1‐phenylethyl chloride (1‐PECl)/CuCl/1,10‐phenantroline and derivatives as initiating systems. Using a 1‐PECl/CuCl/4,7‐diphenyl‐1,10‐phenantroline system in 1,2‐dimethoxybenzene as a solvent at 130°C, homogeneous ATRP of styrene leads to polymers with polydispersities down to 1,1. These new systems are compared with previously described 4,4′‐disubstituted 2,2′‐bipyridine‐based systems in terms of kinetics and quality of control.
Controlled radical polymerization of 4‐vinylpyridine
Authors: Bohrisch Jörg , Wendler Ulrich , Jaeger Werner
Published: April 2003

2,2,6,6‐Tetramethylpiperidine‐N‐oxyl (TEMPO)‐mediated free radical polymerization of 4‐vinylpyridine is found to proceed in a “controlled” manner. A linear increase of molecular weight along with an increase in conversion occurs at varying temperatures. Polymerization of styrene with a poly(4‐vinylpyridine) block as macromer results in block copolymers with narrow polydispersity. The polymers are characterized by different size exclusion chromatography methods and converted to cationic polyelectrolytes as well as to polysulfo‐ and polycarbobetaines.
Polymerization of ethylene with nickel α‐diimine catalysts
Authors: Pappalardo Daniela , Mazzeo Mina , Pellecchia Claudio
Published: April 2003

Several nickel α‐diimine compounds of the general formula (ArNC(R)C(R)NAr)NiX2 (Ar = 2,6‐alkyl substituted Ph, R = H or CH3, X = Br or CH3) were tested in ethylene polymerization after activation with different co‐catalysts, such as methylaluminoxane, Al(C2H5)2Cl or other aluminium alkyls, and ionizing reagents like B(C6F5)3, [CPh3][B(C6F5)4] or HBF4. The performances of the different catalytic systems were compared with reference to polymer productivity and structure. The degree of branching of the obtained polyethylenes was shown to depend not only on the ligand environment at the Ni centre but also on the type of co‐catalyst.
Synthesis of a star‐shaped polymer via coordination of ester‐linked pyridyl‐terminated poly(oxyethylene) with ru(II)
Authors: Naka Kensuke , Kobayashi Akiko , Chujo Yoshiki
Published: April 2003

The star‐shaped polymer with trans‐tetrapyridyl complex of Ru(II) as a core was prepared by complexation of ester‐linked pyridyl‐terminated poly(oxyethylene) (M̄n = 2000) with a Ru5Cl122− cluster. The unimodal peak of the star‐shaped polymer in the gel‐permeation chromatogram was shifted to a higher molecular weight region than that of the starting prepolymer. The electron‐withdrawing ester substituent in para position of the pyridine ring shifted the metal‐to‐ligand charge transfer (MLCT) band into the visible region.
Influence of mixed aluminoxane systems on ethylenenorbornene copolymerization catalyzed by metallocene
Authors: Wang Qi , Weng Jianhua , Fan Zhiqiang , Feng Linxian
Published: April 2003

The norbornene/ethylene copolymerization was investigated using Me2SiCp2MCl2 (M = Zr, Ti)/EBAO and MAO as catalyst systems (EBAO: mixed ethyl‐isobutylaluminoxane, MAO: methylaluminoxane). The copolymers were characterized by DSC and 13C NMR. Copolymers with high content of norbornene and high Tg were obtained with the mixed EBAO. It is suggested that the copolymerization is greatly influenced by the state of the ion pair of the metallocene catalyst. The effect of aluminoxane on the composition and the microstructure of copolymer is discussed.
Network models and their dynamics: probes of topological structure
Authors: Blumen Alexander , Jurjiu Aurel , Koslowski Thorsten
Published: April 2003

In this work we focus on the mechanical relaxation of macromolecules. Based on linear response theory, this relaxation is in general related to the set of eigenmodes and eigenfunctions of the system. Of particular importance are situations which lead to scaling in the time and frequency domains. Thus the relaxation of star polymers, of dendrimers and of hyperbranched structures does not display scaling. On the other hand, one expects that the relaxation of fractals, as in fact that of linear chains, does scale. Here we numerically analyse the behavior of networks modelled through finite Sierpinski‐type lattices, for which we have previously established that in the Rouse picture the mechanical relaxation scales in frequency and in time. As we show here, in the Zimm model based on the preaveraged Oseen‐tensor, the picture changes drastically; taking the hydrodynamic interactions into account leads to relaxation forms which do not scale.
Dielectric relaxations in polymers containing dioxacyclohexane rings by thermostimulated depolarization currents
Authors: Díaz‐Calleja Ricardo , Jesús Sanchis Maria , Aravena Milton , Riande Evaristo , Guzmán Julio
Published: April 2003

The dielectric activity of poly{5‐[(methacryloxy)methyl]‐5‐ethyl‐1,3‐dioxacyclohexane} (PMAMED) and poly[(5‐methacryloxy)‐1,3‐dioxacyclohexane] (PMAD) in the glassy region and in the glass‐rubber transition is investigated by using global and partial thermostimulated discharge current (TSDC) techniques. The global TSDC curve for each polymer displays an ostensible β absorption in the glassy region followed in increasing order of temperature for a prominent α glass rubber relaxation. Partial depolarisation curves show in detail the regions of the glassy state in which more dielectric activity occurs. The TSDC curves for PMAMED are compared with those of its acrylate homologous, poly{5‐[(acryloxy)methyl]‐5‐ethyl‐1,3‐dioxacyclohexane} (PAMED), finding that the methyl group in the former polymer only hinders long range micro‐Brownian motions in the chains, thus shifting the glass‐rubber relaxation to higher temperatures, without affecting in a significant way molecular motions in the glassy region. Small changes in the neighbourhood of the 1,3‐dioxacyclohexane ring, such as suppression of a methylene group or replacement of the equatorial hydrogen in position 2 of the ring for a phenyl group, depresses the dielectric activity and shifts the β absorptions to lower temperatures. The interconversion between TSDC and a.c. dielectric results in the glassy region is discussed.
Computer simulation of the liquid crystal formation in a semi‐flexible polymer system
Authors: Darinskii Anatoly A. , Neelov Igor M. , Zarembo Anna , Balabaev Nikolai K. , Sundholm Franciska , Binder Kurt
Published: April 2003

Molecular dynamic simulations are reported for system of semi‐flexible linear rod‐like molecules. The molecules are composed of Nc tangent soft spheres, connected by elastic springs. Rigidity is introduced by additional springs between all pairs of spheres along the molecule. The formation of only a nematic LC phase is shown for all systems with Nc = 8 and different flexibility. The effect of flexibility on the order parameter and the volume fraction at the LC phase transition is compared with theoretical predictions by Khokhlov‐Semenov and with available simulation data. The dependence of the anisotropy of diffusion on chain flexibility in LC phase was studied. The polymer brushes consisting of flexible and semi‐flexible (composed of linear rod‐like segments) chains were simulated at different grafting densities. Height of brush, order parameter, distribution of density and chain ends in brush were obtained in both cases and compared with theoretical predictions.
Computer simulations of stretching and collapse of polymer molecules in solution
Authors: Neelov Igor M. , Adolf D.B. , Davies G.R. , Darinskii F Anatoly A. , Niemela Satu , Skrifvars M. , Sundholm Franciska
Published: April 2003

Computer simulations are reported for system of linear polymer molecules, diblock copolymer and dendrimer in dilute solution without and with elongational flow. The effect of fluctuating hydrodynamics interactions (HI) on the coil‐stretch transition of linear polymers and dendrimers in elongational flow is studied. The process of coiling of homo‐ and blockcopolymer from completely extended state is also simulated.
Microphase coexistence in polymeric brushes
Authors: Birshtein Tatiana M. , Amoskov Victor M. , Klushin Leonid I. , Mercurieva Anna A. , Polotsky Alexey A. , Iakovlev Petr A.
Published: April 2003

A collapse of polymeric brushes in a solvent can be induced by a change in external conditions, for example, solvent quality or its temperature. The systems with following specific interactions are considered in this paper, namely, polyelectrolyte brushes, amphiphilic brushes in a mixture of incompatible solvents, and brushes with possibility of liquid‐crystalline ordering of polymer segments. For all the systems it is shown that the brush collapse can be observed under certain conditions, and it occurs through a microphase segregation. There are two microphases of different densities that coexist in the brush. The effect is caused by general properties of the swollen phase of polymeric brush and hence appears at all types of the interactions that can induce a phase transition of the brush into collapsed state.
Adsorption of flexible polymers on small colloids: complexes and gels
Authors: Diez Orrite S. , Bonet Avalos J. , Johner A. , Joanny J.F.
Published: April 2003

We describe adsorption of neutral flexible polymer chains onto small colloids that can be covered by one chain. We discuss the structure of star‐shaped complexes and their abundance in dilute solution. In semi‐dilute solution similar complexes form crosslinks between chains and cause gelation.
Conducting polymers electromechanical actuators and strain sensors
Authors: Spinks Geoffrey M. , Wallace Gordon G. , Liu Lu , Zhou Dezhi
Published: April 2003

Electromechanical actuators are being investigated for a wide range of applications in medical, electronics and industrial areas. One attractive application is to incorporate conducting polymer fibre actuators into fabrics for use in prosthetic applications. In this paper, the design of polypyrrole fibre actuators for use in a glove to open and close the human hand (for assisting those with paralysis or hand injuries) is described. The key requirements for this application are the simultaneous generation of 16 mm of contractile movement and 2.9 N of force. Although not critical in the first prototypes, eventually it will also be necessary to produce a rate of movement of around 10 mm sec−1. The effect of the geometry of polypyrrole actuators is examined in this paper and it is shown that a tubular geometry is superior to conventional flat films. Another aspect of the practical use of actuator materials is their control. Fabric strain gauges with polymer actuators is a convenient means for providing feedback control to the actuating element. The fabric strain gauges ideally articulate with fibre actuators to give both the actuating and sensing function in the same fabric structure.
Synthesis of novel architectures by radical polymerization with reversible addition fragmentation chain transfer (RAFT polymerization)
Authors: Moad Graeme , Mayadunne Roshan T.A. , Rizzardo Ezio , Skidmore Mellissa , Thang San H.
Published: April 2003

Radical polymerization with Reversible Addition‐Fragmentation chain Transfer ‐ RAFT polymerization can be adapted to produce a wide variety of block copolymers and other polymers of complex architecture. Such polymerizations require use of a suitable compound [Z‐(C=X)X‐R], which is selected to have a very high transfer constants in radical polymerization of the desired monomers, and appropriate choice of reaction conditions. Block and multiblock polymers, stars and grafts are available through use of precursors containing multiple thiocarbonylthio groups. Stars and microgels are also available through self assembly and crosslinking of RAFT synthesized block copolymer micelles and by a varient of the ‘arm‐first’ approach wherein of a diene monomer is (co)polymerized in the presence of a preformed RAFT‐made polymer. This paper briefly reviews RAFT polymerization then examines the scope for utilizing the technology in the construction of novel architectures.
Nematic conformation of oxyethylene spacers involved in main‐chain liquid crystals
Authors: Furuya Hidemine , Iwanaga Hiroshi , Nakajima Takeshi , Abe Akihiro
Published: April 2003

2HNMR measurements were performed on main‐chain dimer and polymer liquid crystals (LC) having oxyethylene (OE) spacers ‐(OCH2CH2)xO‐(x=2, 3). The orientational as well as conformational characteristics of these molecules have been investigated in bulk and in a nematic solution. The OE spacer was found to take spatial arrangements characteristics of the nematic phase. The nematic conformation of the spacer remains nearly invariant over a wide range of temperature and concentration. In these analyses, the ratio of the deuterium quadrupolar splittings Δν/ΔνR (Δν: spacer and ΔνR: mesogenic unit) provided an important information regarding the spatial configuration of molecules in the LC state. The results obtained in this study are consistent with our previous conclusion drawn on a series of main‐chain LC oligomers and polymers comprising n‐alkane spacers ‐O(CH2)nO‐ (n=9, 10).
Synthesis, properties and molecular modeling of functional hyperbranched polymers and dendrimers
Authors: Fomine S. , Fomina L. , Guadarrama P.
Published: April 2003

The design, synthesis, properties and molecular modeling of fully conjugated dendritic molecules and conjugated hyperbranched polymers are described. It has been shown that conjugated hyperbranched molecules are much more soluble than their linear analogues while maintaining all the properties characteristic of conjugated polymers. It was found that the use of polymeric solid support in hyperbranched polymerization allows to control molecular weight and degree of branching (DB). The molecular modeling of hyperbranched conjugated molecules reveals that hyperbranched structure of conjugated molecules affects significantly neither their stability nor the conjugation. On the other hand the terminal groups affect appreciably the electronic structure of conjugated hyperbranched molecules.
Matrix‐assisted laser desorption/ionization mass spectrometry of synthetic polymers. 7. analysis of fatty alcohol ethoxylates by coupled liquid chromatography at the critical point of adsorption and MALDI‐TOF mass spectrometry
Authors: Spriestersbach Karl‐Heinz , Rode Karsten , Pasch Harald
Published: April 2003

Fatty alcohol ethoxylates can be analyzed efficiently with respect to functionality and molar mass by coupled liquid chromatography and MALDI‐TOF mass spectrometry. Both techniques are coupled via a robotic interface, where the matrix is coaxially added to the eluate and spotted dropwise onto the MALDI target. It is shown that liquid chromatography at critical conditions of adsorption coupled to MALDI‐TOF yield useful structural information on oligomer masses and chemical composition. In particular, the analysis of technical fatty alcohol ethoxylates by LC‐CC/MALDI‐TOF reveals the presence of different functionality fractions in one sample. The oligomer distributions of all functionality fractions are determined.
Ultraviolet (UV) curing of phosphated polyurethane‐acrylic dispersions
Authors: Mequanint Kibret , Sanderson Ronald D.
Published: April 2003

Phosphate‐containing polyurethane‐acrylic dispersions were synthesised for UV curing studies. The effects of light intensity, substrate‐dependent temperature increase, soft‐segment content and water on conversion were investigated. The effect of the light intensity on conversion was twofold. At first, conversion increased with light intensity. This was attributed to the inability of shrinkage to keep pace with the polymerisation and crosslinking, resulting in the creation of free volume, thereby facilitating reaction and enhanced conversion. At higher intensities, conversion was found to be reversed or, at least, it remained constant, owing to increasing radical‐radical termination reactions. Phosphated‐polyurethane coatings with high soft‐segment content show improved conversion with exposure time. This was found to be related to the chain mobility, caused by the low glass transition temperature of the soft segment. The effect of water on conversion was also twofold. On the one hand, water had a plasticising effect on the UV curing and the polymerisation rate was fast. On the other hand, the gel content was found to be lower when films were cured before the evaporation of water.
Investigation into the interactions between filler and elastomers used for tyre production
Authors: Costa Giovanna , Dondero Giovanni , Falqui Luciano , Castellano Maila , Turturro Antonio , Valenti Barbara
Published: April 2003

An investigation in the interactions between silica and elastomers used in the production of tyre treads was carried out. To achieve some knowledge on the interactions between reinforcing agent and elastomers, which are fundamental in determining the rubber reinforcement, inverse gas chromatography (IGC) at infinite dilution was used to evaluate surface properties of both unmodified and modified silica and to calculate the adsorption free energy and enthalpy of low molecular weight analogues of elastomers. The predictions derived from the thermodynamic study were compared with some of the results obtained by a morphological analysis of silica‐filled compounds carried out by transmission electron microscopy (TEM) and automated image analysis (AIA).