bluuebunny/crossref_metadata_2025 huggingface dataset:
Initiator efficiencies in 2,2′‐azoisobutyronitrile‐initiated free‐radical polymerizations of styrene
Authors: Buback Michael , Huckestein Brigitta , Kuchta Frank‐Dieter , Russell Gregory T. , Schmid Elisabeth
Published: April 2003

Results are presented from a comprehensive study of the variation with conversion, temperature and pressure of the initiator efficiency of 2,2′‐azoisobutyronitrile in styrene bulk polymerizations. These efficiencies were measured using a new method involving the use of infra‐red spectroscopy to monitor directly the concentrations of various nitrile‐group containing species. Our results are shown to be satisfactorily fitted by a simple model based on the idea that initiation follows as a result of primary radical fragments diffusing away from each other. Closer microscopic inspection of the variations with temperature and pressure of the entire range of our initiator efficiencies implies the possibility that capture by monomer may also contribute as a mechanism of out‐of‐cage escape of primary radicals. Taking a wider view, the experimental method of this paper is shown to be of use for simultaneous determination of other important kinetic parameters: it yields rate coefficients of initiator decomposition, and also, when initiator decomposition is stimulated by pulse‐laser irradiation, the method is capable of delivering individual values of the rate coefficients for termination and propagation.
Radically initiated copolymers of styrene with 4‐vinylbenzylamine and its trifluoroacetamide derivative, 2. Preparation of latex particles bearing amino groups
Authors: Charreyre Marie‐Thérèse , Razafindrakoto Vanghi , Veron Laurent , Delair Thierry , Pichot Christian
Published: April 2003

Polystyrene(PS)‐based latex particles bearing amino groups have been prepared using a two‐step process consisting of seeded copolymerization of a monomer mixture with styrene (S) and either 4‐vinylbenzylamine (VBA) or its trifluoroacetamide derivative (VBAF) in the presence of monodisperse PS latex. Poor colloidal properties and bad chemical stability were found in the case of latexes obtained with VBA. Better results were obtained with VBAF, but conversion was not completed. Surface characterization of the final latexes by 1H NMR, XPS and colorimetric titration offer some insight into the location of the VBAF monomer units within the particles.
Etude de la réaction de télomérisation d'un monomère tensioactif anionique
Authors: Boutevin Bernard , Robin Jean‐Jaques , Boyer Bernard , Roque Jean‐Pierre , Senhaji Omar
Published: April 2003

The synthesis of a new anionic polymerizable surfactant is described. It is obtained by reaction between methacryloyl chloride and 5‐phenyl‐1‐pentanol. In a last step, the aromatic group is alkylated with succinic anhydride in order to obtain an ionic group. All products were characterized by 1H nuclear magnetic resonance and the transfer constant CT with C8H17C2H4SH and the ratio kp2/kt were determined. CT is in agreement with that of classical acrylates whereas kp2/kt is lower because of the long methacryloyl chain which reduces the propagation rate.
Living cationic polymerization of styrene by the bifunctional initiating system 1,4‐bis(1‐chloroethyl)benzene/SnCl4 in the presence of 2,6‐di‐tert‐butylpyridine
Authors: Kwon Oh‐Sig , Gho Chang Gi , Choi Byong‐Seok , Choi Sam‐Kwon
Published: April 2003

The polymerization of styrene was studied by using a bifunctional initiator, 1,4‐bis(1‐chloroethyl)benzene (1). It was demonstrated that living polymerization can be achieved in the styrene/1/SnCl4 system in chloroform at −15°C in the presence of 2,6‐di‐tert‐butylpyridine. The number‐average molecular weight of the obtained polymers increases with monomer conversion and with addition of a fresh feed of monomer at the end of the first‐stage polymerization. The molecular weight distribution (MWD) of the obtained polymers is narrow ratio of weight‐ to number‐average molecular weights (Mw/Mn < 1,2) throughout the polymerization. In the absence of 2,6‐di‐tert‐butylpyridine, the initiating system results polystyrene with a bimodal MWD. Also a bimodal MWD was obtained with H2O/SnCl4 as initiating system. 2,6‐Di‐tert‐butylpyridine in conjunction with H2O/SnCl4 does not lead to polymerization.
Phase transformation on heating of undercooled melt of poly(ethylene oxide)‐urea molecular complex
Authors: Bogdanov Bogdan , Michailov Marin , Uzov Christo , Gavrailova Girka
Published: April 2003

X‐ray and calorimetric investigations of the structure and transformations on heating of quenched (undercooled) samples of poly(ethylene oxide)‐urea molecular complexes are discussed. It was established that at room temperature the undercooled melt of the molecular complex contains free urea in a tetragonal crystal modification and a high‐temperature poly(ethylene oxide)‐urea molecular complex whose crystal modification does not coincide with the known hexagonal crystal structure of the molecular complex obtained from solution or by slow cooling from the melt. It was shown that on heating this molecular complex to a temperature between 87,5 and 90°C, the hexagonal crystal modification, stable at room temperature, is obtained.
Preparation and photochemical properties of 4‐propenoylbenzil polymers
Authors: Lukáč Ivan , Hrdlovič Pavol , Schnabel Wolfram
Published: April 2003

4‐Propenoylbenzil (PCOCO) obtained by dehydrochlorination of 4‐(3‐chloropropanoyl)benzil (CICOCO) was homo‐ and copolymerized with styrene (St) and methyl methacrylate (MMA). The polymers strongly absorb UV light at wavelengths between 300 and 400 nm. The triplet‐triplet absorption spectra of the homo‐ and copolymers and of CICOCO are bathochromically shifted relative to the spectrum of unsubstituted benzil triplets. The triplets of the homopolymer have a lifetime shorter than that of CICOCO and the copolymers, which is attributed to self‐quenching. Similar conclusions were arrived at from emission measurements. Irradiation of the copolymer PCOCO/St in dilute solution at λinc = 366 nm results in simultaneous crosslinking and mainchain degradation. Crosslinking is accomplished via combination of ketyl radicals formed by hydrogen abstraction of 1,2‐dicarbonyl groups in side chains. Therefore, crosslinking is the predominant process in solutions of hydrogen‐donating liquids such as tetrahydrofuran. Main‐chain scission is a secondary photoreaction. It primarily affords the photooxidative decomposition of 1,2‐dicarbonyl groups. Main‐chain scission predominates over crosslinking in solvents not acting as hydrogen donors such as benzene. Generally, O2 retards crosslinking and enhances main‐chain degradation.
Synthesis and thermal behavior of liquid‐crystalline block copolymers containing both main‐chain and side‐chain mesomorphic blocks
Authors: Galli Giancarlo , Chiellini Emo , Laus Michele , Bignozzi Maria Chiara , Angeloni Annino Sante , Francescangeli Oriano
Published: April 2003

A novel type of block copolymers comprising both side‐chain and main‐chain liquid‐crystalline (LC) blocks in the same macromolecular structure was synthesized and studied. The former block was either one of two LC polymethacrylates containing an azobenzene mesogen with different substituents (block A), and the latter was a semiflexible LC polyester block (block B). Thermal, dynamic‐mechanical, and X‐ray diffraction data indicated that the two structurally different blocks were at least partly phase‐separated within the glassy and LC states. The thermodynamic phase transition parameters of block A were not affected by copolymer composition. However, significant deviations of the thermodynamic parameters of block B were observed relative to those of the corresponding homopolymers. In particular, the normalized transition enthalpies of block B were much lower, suggesting the occurrence of a more or less diffuse interphase. An increase in the nematic‐isotropic temperature was found at variance with previous results on most of the LC block copolymers, in which only one block was an LC component.
Liquid‐crystalline main‐chain polymers with a poly(p‐phenylene terephthalate) backbone, 9. Dynamic mechanical and dielectric behaviour of the polyester with 6‐(pentyloxy)hexyloxy side chains
Authors: Damman Sebastian B. , Buijs Jan A. H. M.
Published: April 2003

In the liquid‐crystalline polymer poly(p‐phenylene terephthalate) with dodecyloxy side chains the various possible crystalline structures of the side chain layers determine the mechanical and dielectric behaviour in the solid state. In this investigation the influence of replacement of the methylene unit at the centre of the side chain by an oxygen atom is studied by means of dynamic mechanical and dielectric measurements. It turns out that the oxygen replacement results in an obstruction of crystallization within the side‐chain layers, as is clearly manifested by the enhancement of the β‐relaxation (attributed to the amorphous side‐chain regions) and the nearly complete disappearance of the β*‐relaxation (crystalline side‐chain regions).
Synthesis of poly(9‐hexyl‐3,6‐carbazolyleneethynylene) and its model compounds
Authors: Beginn Christine , Gražulevičius Juozas V. , Strohriegl Peter , Simmerer Jürgen , Haarer Dietrich
Published: April 2003

The novel conjugated polymer poly(9‐hexyl‐3,6‐carbazoylyleneethylene) (16) was prepared by palladium‐catalyzed polycondensation of 3,6‐diiodo‐9‐hexylcarbazole and 3,6‐diethynyl‐9‐hexylcarbazole. The polymer has a number‐average molecular weight (M̄n) of 3 100. By fractionation a polymer with M̄n of 6 400 was obtained. Besides polycondensation, a palladium‐catalyzed bond‐opening polymerization of the triple bonds occurs as a side reaction which can be partially suppressed by lowering the reaction temperature to 60°C. Two well‐defined model compounds of the title polymer, a dimer and a trimer, were synthesized by stepwise reaction. The mass spectra of both model compounds demonstrate the remarkably high stability of the radical cations of the dimer and trimer. Since the trimer forms a stable glass it is ideally suited for the investigation of its photoconductive properties. First experiments carried out by the Time‐of‐Flight technique showed remarkably high carrier mobilities up to 2 · 10−4 cm2/(V · s) for the trimer.
Functional metallomacrocycles and their polymers, 26. Synthesis of 2‐acryloylamino‐9,16,23‐tri‐tert‐butylphthalocyanine and autoxidation of thiol with water‐soluble polymers containing cobalt(II) phthalocyaninate complex
Authors: Kimura Mutsumi , Dakeno Tomohiro , Adachi Etsuko , Koyama Toshiki , Hanabusa Kenji , Shirai Hirofusa
Published: April 2003

The catalytic autoxidation of 2‐mercaptoethanol was studied by using new water‐soluble polymers containing a cobalt(II) phthalocyaninate complex as a catalyst. The phthalocyanine vinyl‐monomer, 2‐acryloylamino‐9,16,23‐tri‐tert‐butylphthalocyanine (APc(t‐Bu)3), was synthesized and copolymerized with three kinds of water‐soluble monomers to result in a favorite electrostatic environment as a catalyst. The resulting cationic polymer containing a cobalt(II) phthalocyaninate complex has high activity as a catalyst for autoxidation of 2‐mercaptoethanol independent of pH. The catalystic system obeys Michaelis‐Menten kinetics with respect to substrate concentration. The rate constant k5 of the rate‐controlling step and the apparent Michaelis constant K were obtained from a Lineweaver‐Burk plot. The cationic environment on the polymeric catalyst enhances enzyme‐like activity in the neutral pH region for autoxidation of 2‐mercaptoethanol, because of the promotion of substrate dissociation and the accumulation of thiolate anions.
Bulk crystallization of solution epoxidized trans‐1,4‐polyisoprene
Authors: Vasanthan Nadarajah , Corrigan Joseph P. , Woodward Arthur E.
Published: April 2003

Copolymers of trans‐1,4‐polyisoprene containing 2,2 mol‐%, 5,0 mol‐% and 9,8 mol‐% epoxidized units were crystallized from the melt at temperatures (Tc) of 25 to 36°C. The progress of the crystallization was monitored, and final crystallinities at Tc and after cooling to 25°C were measured using Fourier‐transform infrared spectroscopy. The morphology of samples, treated with OsO4 at 25°C after crystallization was complete, was observed using scanning electron microscopy. The crystallinity decreases linearly with increasing epoxy content at Tc = 25°C and 30°C and shows marked deviations from linearity at Tc = 36°C. Differences in morphology with epoxy content and Tc were observed. The differences in crystallinity between solution and melt crystallized samples are discussed.
Anomalies in the temperature dependence of the electrical conductivity of polypyrrole
Authors: Skákalová Viera , Fedorko Pavol , Plocharski Janusz
Published: April 2003

Anomalies in the temperature dependence of the conductivity of BF4− doped polypyrrole were observed in cyclic measurements at temperatures between 250 K and 310 K. The anomalies were accompanied by endothermic effects in differential scanning calorimetry and are interpreted as being due to conformational changes (creation and disappearance of conformational defects) in the polymer chains. The conformational defects are supposed to influence the energy and the concentration of bipolarons and, consequently, the transport in the polymer.
A study of chain dynamics in water‐swollen gels of poly(ethylene oxide) dialkyl ethers using NMR and differential scanning calorimetry
Authors: Knowles Paul R. , Barlow Raymond J. , Heatley Frank , Booth Colin , Price Colin
Published: April 2003

Water swollen gels of (unbranched) dialkyl ethers (n = 16, 17, 18, 20 and 21) of poly(ethylene oxide) (M̄n = 10000, 20000 and 30000) have been investigated using NMR spectroscopy and differential scanning calorimetry (DSC). Aggregates of the alkyl segments were found to undergo a ‘solid/liquid’ transition at a temperature approximating the melting point of an unbranched hydrocarbon about three to four carbon atoms shorter than the alkyl chain. Below the transition temperature, the alkyl component gave a broad NMR line whose second moment was approximately one‐quarter that of a crystalline alkane of similar length. The enthalpy of the transition was approximately one‐third that of the corresponding unbranched alkane. These results indicate a partially crystalline structure for the ‘solid’ aggregates.
Synthesis of poly(chalcone)s by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds
Authors: Ueda Mitsuru , Yokoo Takayoshi , Oda Mitsuo
Published: April 2003

Poly(chalcone)s were prepared by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds in methanesulfonic acid (MSA) or phosphorus pentoxide/methanesulfonic acid (PPMA). Polycondensations proceed smoothly at room temperature and produced poly(chalcone)s with inherent viscosities up to 0,97 dL · g−1. The reaction of acetophenone with aromatic aldehydes in MSA or PPMA was studied in detail to demonstrate the feasibility for polymer formation. Poly(chalcone)s are only soluble in concentrated sulfuric acid and methanesulfonic acid at room temperature. Thermogravimetry of poly(chalcone)s showed 10% weight loss around 380 and 420°C in air and under nitrogen, respectively.
New type of polyvinylsaccharides with N,N‐dimethylbarbituric acid as a linker between sugar and styrene residue
Authors: Wulff Günter , Clarkson Guy
Published: April 2003

A new type of polyvinylsaccharide with a CC bond between the pendent sugar and the backbone was prepared. Without use of protecting groups N,N‐dimethylbarbituric acid was used to link sugars directly to a polymerizable group. Homo‐ as well as copolymers were prepared by radical initiation. The barbiturate ring of the polymer undergoes a specific base‐catalyzed ring cleavage to give highly water‐soluble polymers. Also in copolymers with less than 32 mol‐% styrene residues water solubility is attained due to the newly formed diamide groups.
Ring‐opening metathesis polymerization of 11‐alkylidenebenzonorbornadienes
Authors: Schimetta Michael , Stelzer Franz
Published: April 2003

11‐(α‐Phenylbenzylidene)benzonorbornadiene (3) and other similar monomers were synthesized by cycloaddition of dehydrobenzene with different fulvenes. Ring‐opening metathesis polymerization of the resulting monomers using Mo‐carbene initiators gave highly stereoregular polymers. Variation of the substituents allows control of the stereoregularity of these polymers. Poly[11‐(α‐phenylbenzylidene)benzonorbornadiene] is completely cis connected, whereas poly[11‐(α‐methylbenzylidene)benzonorbornadiene] is completely trans linked. The polymers contain two very reactive carbon‐hydrogen bonds that are both allylic and benzylic. Elimination of these bridgehead hydrogens gives a fully conjugated polymer that can be described as having “fulvenoid” or “quinoid” geometry.
The crystal and molecular structure of an asymmetric diacetylene monomer, 6‐(2‐methyl‐4‐nitroanilino)‐2,4‐hexadiyn‐1‐ol
Authors: Vlasse Marcus , Paley Mark S.
Published: April 2003

The crystal and molecular structure of an asymmetric diacetylene monomer has been determined from x‐ray diffraction data. The crystals, obtained from an acetone/pentane solution, are orthorhombic, Fdd2 with Z = 16 in a unit cell having dimensions of a = 42,815(6) Å, b = 22,224(5) Å, c = 4,996(1) Å. The structure was solved by direct methods and refined by leastsquares techniques to an RF of 6,4% for 988 reflections and 171 variables. The diacetylene chains are disposed in the unit cell in a complex manner in order to satisfy the hydrogen‐bonding, crystal packing, and symmetry requirements of the system. The solid state polymerization mechanism is discussed with respect to the geometric disposition of the diacetylene chains. These chains are far apart and incorrectly oriented with respect to each other to permit polymerization in the crystal by means of 1,4‐addition, consistent with the Baughman mechanistic model.
Graft copolymerization of methyl methacrylate by lithium diisopropylamide‐treated poly(vinyl propionate)
Authors: Inoki Mari , Akutsu Fumihiko , Yamaguchi Hideki , Naruchi Kiyoshi , Miura Masatoshi
Published: April 2003

The anionic grafting of methyl methacrylate (MMA) onto poly(vinyl propionate) (PVPr) was achieved after treatment of the latter with lithium diisopropylamide (LDA). The percentage of grafting of the polymer was between 120 and 730%, no homopolymers being obtained. The degree of lithiation was determined to be 26 mol‐% with respect to monomer units by means of deuterolysis. The hydrolysis of the graft copolymers results in the side‐chain polymers (PMMA) and poly(vinyl alcohol) (PVA). The average number of branches in the graft copolymer increases from 1 to 7 with increasing percentage of grafting. M̄w/M̄n of the side chain poymer is between 2,0 and 6,7. The low reactivity of the lithium sites may be caused by aggregation of enolates, leading of the broadening of the molecular weight distribution.
Reduction of bis(η5‐cyclopentadienyl)zirconium dichloride in the presence of methylalumoxane
Authors: Cam Darinn , Sartori Franco , Maldotti Andrea
Published: April 2003

The reaction occurring between bis(η5‐C5H5)ZrCl2 (C5H5 = cyclopentadienyl) and methylalumoxane (MAO) has been studied by means of electron paramagnetic resonance (EPR) spectroscopy at different zirconium concentrations and Al/Zr mole ratios. The toluene solution of bis(η5‐C5H5)ZrCl2/methylalumoxane, in the absence of ethylene, was verified to be more stable than the catalytic system based on bis(η5‐C5H5)TiCl2/AIR3 (R = alkyl). Zr(IV) was reduced to Zr(III) in small amounts with a Landé factor g = 1,998 and a hyperfine interaction splitting constant α (91Zr) = 7 G. The presence of ethylene strongly increased the efficiency of the Zr(IV) to Zr(III) reduction. Simultaneously it modified the chemical electronic surrounding of the Zr nucleus as revealed by the sharp increase of α(91Zr) = 12 G.
Enhancement of miscibility between hemicellulose and lignin by addition of their copolymer, the lignin‐carbohydrate complex
Authors: Shigematsu Mikiji , Morita Mitsuhiro , Sakata Isao , Tanahashi Mitsuhiko
Published: April 2003

The miscibility between hemicellulose and lignin from beech wood was investigated from observation of their glass transition temperature, along with the effect of addition of their copolymer, the lignin‐carbohydrate complex (LCC). The binary and ternary blend systems of hemicellulose, lignin and LCC change from immiscible to miscible by increasing the temperature. This behavior shows that this blend system has an upper critical solution temperature (UCST). The binodal temperature decreases with increasing amount of LCC added. This behavior was analyzed by the temperature and composition dependence of the Flory polymer‐polymer interaction parameter (χ12). The value of χ12 estimated from the phase diagrams indicates that χ12 decreases with an increase in both the lignin content and the temperature.
Synthesis of 6‐O‐carboxymethylchitin immobilizing doxorubicins through tetrapeptide spacer groups and its enzymatic release behavior of doxorubicin in vitro
Authors: Ohya Yuichi , Nonomura Koji , Hirai Keiichi , Ouchi Tatsuro
Published: April 2003

Chitin is a non‐toxic biodegradable polysaccharide. 6‐O‐Carboxymethylchitin (CM‐chitin) is a water‐soluble chitin derivative. In order to provide a water‐soluble macromolecular prodrug of doxorubicin (DXR) reducing the side‐effects and exhibiting high antitumor activity, the fixation of DXRs to CM‐chitin through covalent bonds was carried out. Especially, a lysosomally digestible tetrapeptide (Gly‐Phe‐Leu‐Gly) was used as spacer groups between CM‐chitin and DXRs. In this paper, two kinds of conjugates, CM‐chitin/Gly‐Phe‐Leu‐Gly/DXR conjugate 5 having lysosomally digestible tetrapeptide spacer groups and CM‐chitin/C5/DXR conjugate 6 having pentamethylene spacer groups, were synthesized. The effect of introduction of the spacer groups on the release behavior of DXR from the conjugate was investigated. The conjugate 5 having tetrapeptide spacer groups showed a distinct increase in the release rate of DXR in the presence of the lysosomal enzyme cathepsin B at 37°C in vitro; however, the conjugate 6 did not show such specific release behavior.
Poly(phenylene oxide) macromonomers for graft copolymer synthesis via ring‐opening olefin metathesis polymerization
Authors: Grutke Stefan , Hurley James H. , Risse Wilhelm
Published: April 2003

Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) samples with bicyclic olefin end groups were obtained by esterification of the hydroxyl end group of the poly(phenylene oxide) with bicyclo[2.2.1]hept‐5‐ene‐2‐carbonyl chloride. Mixtures of these macromonomers with bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid 2‐(2‐(2‐methoxyethoxy)ethoxy)ethyl ester were copolymerized by ring‐opening olefin metathesis polymerization (ROMP) to produce graft copolymers with poly(phenylene oxide) side chains. The catalyst used for the metathesis polymerization was RuCl3(hydrate). Molecular weights of the graft copolymers were in the range of 130 000 to 250 000. Macromonomers containing exclusively exo‐linked bicyclic end groups were found to be more reactive than macromonomers with 55% exo‐ and 45% endo‐substituted end groups.
Degradation of a branched perfluoropolyalkylether fluid with anhydrous aluminium chloride
Authors: Eapen Kalathil C. , John Peter J. , Liang Jim C.
Published: April 2003

The degradation of a branched perfluoropolyalkylether (PFPAE) fluid with anhydrous AlCl3, in the absence of oxygen, has been re‐examined with emphasis on understanding the nature of the volatile products formed. GC/FTIR and GC/MS have been employed for identification of a number of compounds in the complex mixture of volatile products obtained. Hexafluoroacetone was a major component of this mixture. In addition, a number of chlorofluoro compounds and shorter chain oligomers without and with reactive functional groups such as ketone, acyl fluoride, and acyl chloride were formed. While successive losses of end units appear to be the predominant mode of degradation, the possibility of internal bond fission cannot be completely ruled out. There is strong evidence to suggest that carbonyl functional groups are not restricted to the leaving monomer units. They are present to a smaller extent in the residual fluid also. More than one mode of degradation, beginning either at the perfluoropropoxy end‐group or perfluoroethoxy end‐group which involves migration of a chlorine atom or fluorine atom from the end‐group to internal site or vice versa, can explain the formation of the volatile compounds identified. The mechanism of degradation involved in the initial loss of a terminal unit need not be operational in further degradation of the polymer chain, as a carbonyl functionality generated in the end‐group of the degrading polymer chain can alter the course of further reactions. While such a change in the mechanism of degradation is possible due to carbonyl functionality generated, it remains speculative in the absence of experimental support.
Effects of axial ligands on the electron transfer catalyzed by manganese tatrakis(pentafluorophenyl)porphyrin in poly(γ‐methyl L‐glutamate) membrane
Authors: Dewa Takehisa , Satoh Mitsuru , Komiyama Jiro , Nango Mamoru , Tsuda Kazuichi
Published: April 2003

Poly(γ‐methyl L‐glutamate) (PMLG) membrane containing manganese tetrakis(pentafluorophenyl)porphyrin

Systematic name: Tetrakis(pentafluorophenyl)porphyrinatomanganese.

(MnPFPP) has been studied for the transmembrane redox reaction between dithionite and ferricyanide in separated solutions. The effects of the ligand species, namely, OH−, Cl−, imidazole (Im), pyrazine (Pyz), triethylamine (TEA), and pyridine (Py), on the electron transfer rate in the membrane were examined. UV/VIS spectroscopy and sorption measurements confirm that these ligands are sorbed by the membrane from the external buffer solution and coordinate to MnPFPP. With the membrane containing 160 μmol · g−1 of MnPFPP, the apparent rate factor, estimated as the pseudo‐first‐order rate constant of the bleach of ferricyanide times membrane thickness, follows the order Im ≫ Cl− > Pyz > TEA, OH−, Py > 0, suggesting that Im, Cl− and Pyz are effective ligands for the electron transfer. Such a ligand‐specific transfer stems from the electron‐transferability of the ligands between MnPFPP's.
Liquid‐crystal behaviour of some laterally substituted stiffchain polyesters containing 2‐phenylbenzoxazole units
Authors: Centore Roberto , Roviello Antonio , Sirigu Augusto , Kricheldorf Hans R.
Published: April 2003

The synthesis and the phase behaviour of three laterally substituted stiff‐chain polymers containing 2‐phenylbenzoxazole units is reported. Polymers were obtained by reaction of 2‐(4‐acetoxyphenyl)‐6‐acetoxybenzoxazole with 2‐phenoxyterephthalic acid (polymer 2a), 2‐phenylthioterephthalic acid (polymer 2b) and 2‐hexadecylthioterephthalic acid (polymer 2c). Polymers 2a and 2b are virtually non‐crystalline. 2a is nematogenic, while for 2b a smectic‐like liquidcrystal phase is observed, whose structural periodicity is probably connected with the intercalated stacking of the lateral phenyl groups along the direction of the chain axes. The solid phase of 2c is of the sanidic type. On melting, a liquid‐crystal phase with equatorial periodicity is observed. This periodicity is probably related to the segregation of the stiff chains between the paraffinic layers.
Fluorination of polymers containing COOH/COOR groups with SF4/HF, 1. Model reactions with low molecular weight compounds
Authors: Nuyken Oskar , Dannhorn Wolfgang , Obrecht Werner
Published: April 2003

Model studies with low molecular weight compounds are performed in order to evaluate the feasibility of synthesizing fluorine‐containing polymers by modification of commercially available products. The conversion of COOH and COOR into CF3 moieties by means of SF4/HF is checked with the following low molecular weight models for poly(acrylic acid) and poly(acrylic ester)s: hexanoic acid (1), ethyl hexanoate (2), 2,4‐dimethylglutaric acid (3), 4‐carboxypimelic acid (4) and 2,2‐diethylmalonic acid (5). For the model compounds, the reaction conditions have been optimized. The desired products are obtained in high yield and in high selectivity. Therefore, this type of reaction will be applied to the modification of polymers in the next step.
Free radical suspension polymerization kinetics of styrene up to high conversion
Authors: Tefera Nurelegne , Weickert Günter , Bloodworth Robert , Schweer Johannes
Published: April 2003

Styrene was polymerized using different amounts of azoisobutyronitrile as initiator at temperatures of 70°C, 75°C and 80°C in suspension. The course of reaction up to almost complete conversion was modeled within a classical kinetic framework. Optimal simultaneous descriptions of both conversion and average degree of polymerization data were possible using two sets of values for the variation of the overall termination rate coefficient kt with conversion. One explanation for this is that kt is chain length dependent. Evidence for this necessity was derived by considering all kinetic parameters, except the termination rate coefficient, as reliable absolute values.
Polymerization of L‐lactide and ϵ‐caprolactone in the presence of methyl trifluoromethanesulfonate
Authors: Rangel Irma , Ricard Michèle , Ricard Alain
Published: April 2003

The cationic polymerization of L‐lactide and ϵ‐caprolactone initiated by methyl trifluoromethanesulfonate in nitrobenzene was studied. The monomer conversion and the average molecular weight decrease when the temperature increases. The kinetics constants for L‐lactide and ϵ‐caprolactone polymerizations are, respectively, equal to 1,7·10−3 min−1 and 1,60·10−3 min−1 at 50°C. The thermodynamic parameters were determined from the temperature dependence of the equilibrium monomer concentration. Thus for L‐lactide and ϵ‐caprolactone polymerization the enthalpy and entropy values are, respectively, equal to ΔH(L‐lactide) = −24,9 kJ/mol; ΔS(L‐lactide) = −25 J/(mol·K) and ΔH(ϵ‐caprolactone) = −15,35 kJ/mol; ΔS(ϵ‐caprolactone) = −35 J/(mol·K).
Electron paramagnetic resonance investigation of the nature of the propagating species in methyl methacrylate polymerization
Authors: Tonge Matthew P. , Pace Ronald J. , Gilbert Robert G.
Published: April 2003

The electron paramagnetic resonance (EPR) spectrum of methyl methacrylate polymerizing in a range of systems is simulated using a consistent set of parameters for two rotamers of a single free radical. The 9‐line spectrum observed in bulk and emulsion polymerization was fitted by a superposition of two spectra corresponding to two rotamers of a long‐chain species (each a somewhat hindered, non‐rotating macroradical), having anisotropic methylene proton hyperfine couplings which can be treated as isotropic to a good approximation. The 13‐line spectrum observed at low conversion with very high radical flux was simulated as a superposition of the spectra of two very similar rotamers, the EPR spectra of which are indistinguishable; either rotamer is part of a very short chain (primarily an initiator fragment which has propagated once) undergoing free rotation in a low‐viscosity medium. Thus the EPR spectra can be explained without having to invoke earlier suggestions that there are two types of free radicals (“trapped” and “untrapped”) in these systems, corresponding to the 9‐line and 13‐line spectra. The existence of an enormous proportion of very short free radicals under conditions of high radical flux is supported by quantitative calculations of the radical chain‐length distribution. It is suggested that the two rotamers have significantly different propagation rate coefficients because of differences in the hindered rotations in their transition states.
Protection and polymerization of functional monomers, 22. Synthesis of well‐defined poly(4‐vinylbenzoic acid) by means of anionic living polymerization of N‐(4‐vinylbenzoyl)‐N′‐methylpiperazine, followed by deprotection
Authors: Ishizone Takashi , Kurosawa Hiroki , Hirao Akira , Nakahama Seiichi
Published: April 2003

Anionic polymerizations of N‐(4‐vinylbenzoyl)‐N′‐methylpiperazine (3a) and N‐(4‐vinylbenzoyl)morpholine (3b) were carried out in tetrahydrofuran at −78°C with oligo(α‐methylstyryl)‐dilithium, ‐disodium, and ‐dipotassium. The polymerizations of both 3a and 3b proceeded quantitatively to give stable living polymers having predicted molecular weights and narrow molecular weight distributions. Novel block copolymers, poly(3a)‐block‐polystyrene‐block‐poly(3a) and poly(3b)‐block‐polystyrene‐block‐poly(3b), were synthesized by using these living polymerization systems. Under acidic conditions (6 N HCl in 1,4‐dioxane‐water), quantitative hydrolysis of the amide linkage of the poly(3a) was achieved to give a well‐defined poly(4‐vinyl‐benzoic acid).
Protection and polymerization of functional monomers, 23. Synthesis of well‐defined poly(2‐hydroxyethyl methacrylate) by means of anionic living polymerization of protected monomers
Authors: Mori Hideharu , Wakisaka Osamu , Hirao Akira , Nakahama Seiichi
Published: April 2003

Anionic polymerizations of 2‐[(trimethylsilyl)oxy]ethyl methacrylate (1), 2‐[(tert‐butyldimethylsilyl)oxy]ethyl methacrylate (2), and 2‐[(methoxymethyl)oxy]ethyl methacrylate (3), the protected forms of 2‐hydroxyethyl methacrylate (HEMA), were carried out in THF at −78°C with 1,1‐diphenylhexyllithium or 1,1‐diphenyl‐3‐methylpentyllithium in the presence of LiCl. The resulting poly(1–3)s were found to possess predictable molecular weights and very narrow molecular weight distributions. The sequential polymerizations of tert‐butyl methacrylate with the anionic propagating ends of poly(1–3) gave block copolymers in quantitative efficiency. Thus, the anionic polymerizations of 1–3 proceeded without transfer and termination reactions to afford stable living polymers. Complete hydrolysis of the protective groups of poly(1–3)s produced linear poly(HEMA) quantitatively. Novel well‐defined di‐ and triblock copolymers containing hydrophobic [polystyrene, poly(4‐octylstyrene), polyisoprene] and hydrophilic segments [poly(HEMA)] were also prepared by sequential polymerization of the corresponding hydrophobic comonomers with 1, followed by deprotection.
A modified synthesis of liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s with completely random chain structure
Authors: Böhme Frank , Komber Hartmut , Leistner Dirk , Rätzsch Manfred
Published: April 2003

A new method for synthesis of liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s (PET/HBA) is proposed. In order to prevent formation of PET‐rich phases, complex monomers were used instead of PET. In comparison tc copolyesters synthesized conventionally, the new products proved to be much more homogeneous. 13C NMR measurements evidenced that the chain segment distribution is almost random. In contrast to literature data for a copolyester composition of PET/HBA (50/50 mol/mol) only a single glass transition was detected by dynamic mechanical analysis. The influence of transesterification reactions on the homogeneity is discussed.
Thermally induced relaxation and recovery of the macroscopic orientation in a side‐chain liquid crystalline polyacrylate
Authors: Yuan Guoxiong , Zhao Yue
Published: April 2003

Thermal relaxation behavior of a mechanically induced macroscopic orientation of the mesogenic groups in a side‐chain liquid crystalline polyacrylate was investigated using timedependent polarized infrared spectroscopy. It was found that a complete relaxation occurred only at temperatures in the nematic to isotropic transition region, and that, more interestingly, the completely relaxed macroscopic orientation was recoverable by cooling the sample to its nematic state. This thermally induced relaxation and recovery of the macroscopic orientation was reversible upon repeated temperature changing cycles over an aging time of more than five hours. Moreover, the level of the orientation recovery was found to be sensitive to the recovery and relaxation temperatures and to the annealing duration at the relaxation temperature before cooling. A tentative interpretation is proposed for this orientation recovery.
Polymeric surfactant systems in the asymmetric hydrogenation of amino acid precursors with a rhodium complex
Authors: Flach Herbert Niels , Grassert Ingrid , Oehme Günther
Published: April 2003

The synthesis of new types of soluble and insoluble amphiphilic systems is described, being polysoaps, crosslinked polysoaps, an amphiphilised ion exchanger, and ion exchangers loaded with ionic surfactants. It was possible to synthesise insoluble polymeric systems which nevertheless showed micellar properties. The polymers were tested as aids in the stereospecific hydrogenation of (Z)‐methyl α‐acetamidocinnamate to the methyl ester of N‐acetylphenylalanine (R) by means of an optically active rhodium complex in water. With linear polysoaps the effect on the reaction was dependent on the structure of the soap molecules. The enantioselectivity of the reaction with monomeric surfactants in water was almost attained. Crosslinked polysoaps showed the same effects on the hydrogenation as linear polysoaps with an analogous structure. Macromolecular ion exchangers loaded with amphiphilic counterions gave in hydrogenation almost the same effect as these counterions give when they are not bound to an insoluble carrier. Enantioselectivities and reaction rates were usually slightly lower than with monomeric surfactants. However, there is an advantage in the separation of catalyst and product after reaction. It was shown that the rhodium‐containing amphiphilic ion exchangers could be reused for up to 9 times.
Structure of the hard segments in non hydrogen bond forming polyurethane elastomers as derived from oligomeric model compounds
Authors: Eisenbach Claus D. , Nefzger Hartmut , Hayen Heidi , Enkelmann Volker
Published: April 2003

Several molecularly uniform oligourethane model compounds for the hard segment of segmented polyurethane elastomers with piperazine (PIP) and tetramethylene bischloroformate based hard segments have been synthesized. X‐ray structure analysis was performed on single crystals with both compounds representing different parts of the piperazine‐1,4‐diylcarbonyloxy‐tetramethyleneoxycarbonyl repeating unit or containing at least one complete repeating unit and methylurethane end groups. A common feature of the model compounds investigated was that the PIP rings are in the chair conformation; the oxytetramethyleneoxy unit is in the g+ tg− conformation, which is also the conformation of the higher melting modification of the two hard segment model polymorphs. The conformation and packing model of the hard segment was derived from the crystal structure of the model compound containing one repeating unit by connecting the two methyl end groups of successive molecules by a CH2CH2 unit without shifting the molecules, i. e., by replacement of two opposing OCH3 groups by an oxytetramethyleneoxy chain in the g+ tg− conformation. The resulting cell for the polyurethane model structure is triclinic and contains two units of half a polymer repeat, and is in excellent agreement with the experimental X‐ray powder diffraction pattern of the hard segment polymer.
Synthesis and polymerization of N‐trimethylsilylacrylamide: A hydrophobic acrylamide
Authors: Dasgupta Arnab , Sivaram Swaminathan
Published: April 2003

N‐Trimethylsilylacrylamide (TMSAm), a hydrophobic acrylamide, has been synthesized and characterized. The monomer could be polymerized in benzene by 2,2′‐azoisobutyronitrile or benzoyl peroxide to poly(TMSAm). The silylated polymer was characterized with 1H NMR. Poly(TMSAm) is stable in the absence of moisture. It could be quantitatively hydrolyzed to polyacrylamide under mild conditions. The monomer has been copolymerized with styrene in benzene by benzoyl peroxide to yield polymers which on hydrolysis give copolymers of acrylamide and styrene.
Extrapolation of solubility data of monomeric, oligomeric and polymeric hydrocarbons
Authors: Horacek Heinrich
Published: April 2003

Solubility data of hydrocarbons in poly(propylene) were determined by means of inverse gas chromatography and vapour pressure measurements. For better extrapolation, these data were arranged in solubilities of monomers in monomers, in dimers, in oligomers and in polymers as well as in solubilities of monomers, dimers and oligomers in polymers. The results indicate that cyclic compounds are better solvents for polymers than linear ones, because both are more similar in terms of end‐groups. From a theoretical point of view, the extrapolation of solubilities of monomers in polymers to polymers in polymers leads from the Bunsen solubility to the ideal rubber elasticity. The extrapolation of solubilities of monomers in monomers to monomers in their polymers conduces from the ideal gas law or the solubility in itself to the Henry law. The knowledge of solubility is important for the physical foaming process where very fine cell structures are promoted by supercritical gases. Solubility data of propene in hydrocarbons and in poly(propylene) support the thermodynamics of poly(propylene) manufacturing: the heat of solution for propane in poly(propylene) was determined to be 14,7 kJ/mol.
Pop‐corn polymerization of 2‐hydroxyethyl methacrylate and the influence of a charged comonomer
Authors: Starodubtzev Sergei G. , Makhaeva E. E. , Golubev V. B. , Lachinov M. B.
Published: April 2003

The three‐dimensional copolymerization of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate in the presence of water has been studied. An increasing concentration of ethylene dimethyacrylate results in the formation of a pop‐corn polymer. The flakes of the pop‐corn polymer initiate the polymerization of an added monomer which again results in a pop‐corn polymer. The addition of a small percentage of charged monomer into the copolymerization batch (potassium methyacrylate) prevents the formation of a pop‐corn polymer. An experimental investigation of the free‐radical polymerization kinetics was carried out.
Functional metallomacrocycles and their polymers, 27. Catalase‐like activity of water‐soluble polymer containing a phthalocyanine‐manganese complex
Authors: Kimura Mutsumi , Nishigaki Tadayoshi , Koyama Toshiki , Hanabusa Kenji , Shirai Hirofusa
Published: April 2003

The decomposition reaction of hydrogen peroxide by a water‐soluble polymer containing phthalocyanine‐Mn (1c, 1d) was studied in aqueous solution. The catalase‐like activity was varied by the kind of added nitrogen base and its concentration. The catalase‐like activity is also dependent upon the basicity of the nitrogen base and the equilibrium constant for the coordination of the nitrogen base to phthalocyanine‐Mn in lc or 1d. In this catalytic system, the deprotonation of hydrogen peroxide and the formation of a five‐coordinated manganese species are an important factor in the catalase‐like activity. Copolymers 1c and 1d have high activity as catalyst for the decomposition of hydrogen peroxide in the presence of dimethylaminopyridine (DMAPy). The catalytic system obeys Michaelis‐Menten kinetics with respect to the concentration of hydrogen peroxide. The reaction proceeds according to a mechanism similar to that of a reaction catalyzed by catalase.
Studies on the polymerization of ethylene using a high‐yield MgCl2‐supported titanium catalyst, 4. Structural investigation by X‐ray diffraction and electron spin resonance measurements on the state of titanium ions in the standard system and its modifications
Authors: Fuhrmann Hans , Herrmann Werner
Published: April 2003

The MgCl2‐supported titanium catalyst MTKST was characterized by X‐ray diffraction measurement and electron spin resonance (ESR) spectroscopy. To obtain a better understanding of the nature of active sites the process of catalyst formation was interrupted at several stages to obtain samples for ESR measurements. Likewise some systematic modifications of the standard system were performed and the results were studied by ESR technique. The structural data were correlated with the activity pattern in the polymerization of ethylene. It is suggested that the precursor of an active site is a clustered titanium species containing titanium ions of mixed valence state which is complexed and alkylated by AIR3 giving a polymerization active species of high efficiency. A comparison with the polymerization data suggests that the active species or its immediate precursor is characterized by an ESR signal with rhombic anisotropy with g1 = 1,94, g2 = 1,89, g3 = 1,76.
Chemoenzymatic synthesis of linear poly(sucrose acrylate): Optimization of enzyme activity and polymerization conditions
Authors: Chen Xiaomao , Johnson Amy , Dordick Jonathan S. , Rethwisch David G.
Published: April 2003

We have achieved significant improvements in the synthesis of poly(sucrose acrylate). A screen of 15 commercial enzymes was carried out and Alcalase 2T was selected as the best enzyme because of its high activity and selectivity for acylation of sucrose at only one site. The rate of the enzyme catalyzed acylation of sucrose to form sucrose 1'‐acrylate was increased by a factor of ca. 100 compared to previous reports. This rate was increased 10‐fold by treating the as received enzyme by adjusting the pH to the optimum value for the enzyme. An additional 10‐fold increase was achieved by adding a lyoprotectant such as sucrose or poly(ethylene glycol) prior to lyophilizing the enzyme. Significantly higher molecular weights were obtained in aqueous polymerization systems than when N,N‐dimethylformamide (DMF) was used as the solvent. Similarly, higher molecular weights were observed for oxidation/reduction than for azo‐type free radical initiators. We have demonstrated that copolymers of sucrose acrylate and acrylic acid are readily prepared. Finally, by optimization of the polymerization system, we have increased the number‐average molecular weight of the poly(sucrose acrylate) from M̄n = 54 000 to molecular weights M̄n as high as 2 400 000.
Differential scanning calorimetry and thermogravimetry studies of polyacrylamide prepared by free‐radical polymerization in inverse microemulsion and in solution
Authors: Janigová Ivica , Csomorová Katarína , Stillhammerová Martina , Bartoň Jaroslav
Published: April 2003

In spite of the free‐radical polymerization of acrylamide in different reaction environments (non‐percolating (A) and/or percolating (B) inverse microemulsions, water/isopropanol solution (C)) the polyacrylamides obtained did not differ in their Tg values (A: 468 K; B: 469 K; C: 468 K). Similarly, the course of thermogravimetry curves for all three samples A, B and C, was practically identical. The results confirmed that the spatially oriented array of acrylamide molecules at the water/oil interface of the inverse micellar system was destroyed already at early stages of polymerization. The formation of longer polymer chains due to the polymerization at water/oil interface was thus restricted or even eliminated in favor of the propagation of polyacrylamide growing chains in isotropic conditions of water pools of inverse micelles.
Doped polymers by oxidative polymerization, 3. Electrochemical synthesis of poly[trans‐1,2‐di(2‐furyl)ethylene]
Authors: Koßmehl Gerhard , Greczmiel Thomas , Plieth Waldfried
Published: April 2003

Redoxable poly[trans‐1,2‐di(2‐furyl)ethylene] films (PDFE) were synthesized by electrochemical polymerization of trans‐1,2‐di(2‐furyl)ethylene (DFE). Acetonitrile, benzonitrile, nitromethane and propylene carbonate proved to be useful solvents for this polymerization reaction. Suitable supporting electrolytes are tetrabutylammonium perchlorate (TBAP), tetrabutylammonium tetrafluoroborate and lithium perchlorate. To avoid irreversible overoxidation of the polymer, the potential should not exceed 1,15 V (vs. Ag/AgCl). The maintenance of the furan rings in the polymer can be gathered from the reflection IR spectrum. The redoxability of the polymer can be proved by means of the UV/Vis spectrum, which shows a shift of maximum absorption from 310 nm in the reduced state to 345 nm in the oxidized state. PDFE shows an electrochromic behaviour. The potential of oxidation of DFE lies in the same range as the analogous thiophene derivative trans‐1,2‐di(2‐thienyl)ethylene (DTE). A comparison of the polymer PDFE and its corresponding thiophene derivative poly[trans‐1,2‐di(2‐thienyl)ethylene] (PDTE) shows that PDFE is more sensitive to overoxidation, and its electrical conductivity is several orders of magnitude lower.