bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soluble, well‐defined copper(I) and silver(I) coordination polymers from 4,4″‐bis((9‐aryl)‐2‐o‐phenanthrolinyl)‐2′,5′‐dihexyl‐p‐terphenyl
Authors: Velten Ulf , Lahn Brigitte , Rehahn Matthias 
Published: April 2003

AbstractA novel synthetic concept is presented which allows, for the first time, the preparation of soluble, constitutionally well‐defined transition‐metal coordination polymers of considerable molecular weights from kinetically unstable, pseudotetrahedral copper(I)‐ and silver(I)‐phenanthroline complexes. It is demonstrated that rigorous exclusion of all molecules that might act as competitive ligands for the metal ions of the polymer constitutes the central requirement for obtaining solutions of “proper” coordination polymers, i.e., polymers having a constant number of repeating units per individual chain. Tetrachloroethane was found to be an appropriate solvent for this purpose. Solubility of the copper(I) and silver(I) coordination polymers – which are polyelectrolytes – in this rather apolar solvent was achieved by the attachment of two hexyl side chains to each polymer repeating unit. It was thus possible to prove the defect‐free constitution of the obtained coordination polymers and to show their excellent stability in solution with the aid of 1H and 13C NMR spectroscopy. Moreover, formation of coordination polymers of considerable chain lengths is supported by the complete disappearance of end‐group absorptions in the 1H NMR spectra and the results of viscosimetric investigations.
Self‐organization of a liquid crystalline methacrylate‐monofunctionalized crown‐ether compound in low‐shrinkage acrylate mixtures
Authors: Beginn Uwe , Zipp Gabriela , Möller Martin , Johansson Gary , Percec Virgil 
Published: April 2003

AbstractCrystallization and supramolecular aggregation of 1,4,7,10,13‐pentaoxacyclopentadecane‐2‐ylmethyl 3,4‐bis[4‐(dodecyl‐1‐oxy)benzyloxy]‐5‐(11‐methacryloyloxyundecyl‐1‐oxy)benzoate (1) and its complexes with sodium triflate are described in solutions of the methacrylate monomers. Formation of a gel was observed covering a rather wide concentration range in the pseudo‐binary phase diagram. In the low concentration regime and at low temperatures, gel formation by elongated crystals of 1 was observed. It was demonstrated that the formation of a crystalline network and the shape of the crystals strongly depend on the cooling rate.
Surface acidic sites on supported titanium‐magnesium catalyst for propylene polymerization: ESR study via adsorption of stable nitroxyl radicals
Authors: Potapov Alexandr G. , Zakharov Vladimir A. , Mikenas Tatijana B. , Sergeev Sergeyi A. , Volodin Alexandr M. 
Published: April 2003

AbstractESR was used for studying the interaction between the stable nitroxyl radical TEMPO (2,2,6,6‐tetramethylpyperidin‐1‐oxyl) and the titanium‐magnesium catalysts TiCl4/MgCl2 and TiCl4/MgCl2 · nD (D is either diisobutyl phthalate or 2,2‐diisobutyl‐1,3‐dimethoxypropane), as well as TiCl4/MgCl2 · nD treated with triethylaluminium. In all cases, only part of the surface titanium complexes (18–53 mol‐%) exhibit Lewis acid properties and can interact with TEMPO. The portion of titanium complexes with acidic properties depends on the composition and preparation of the catalysts, and it decreases upon treatment with triethylaluminium.
Liquid crystalline networks from 1,4‐benzenedicarboxylic acid bis(4‐cyanatomethylphenyl) ester
Authors: Shiota Atsushi , Körner Hilmar , Ober Christopher K. 
Published: April 2003

AbstractThe phase behaviour and curing reaction of 1,4‐benzenedicarboxylic acid bis(4‐cyanatomethylphenyl) ester (LC dicyanate) as well as the mechanical properties of the LC network were examined. The overall reaction kinetics were found to be first order with an activation energy of 67.5 kJ/mol similar to many conventional dicyanate monomers. Gelation was detected by viscoelastic measurements and occurred at a conversion of ≈0.5. These results suggest that the topology of the network formed in the LC dicyanate system was the same as non‐LC dicyanates such as 2,2‐bis(cyanatophenyl)propane. The onset of the mesophase was found to start at a conversion of ≈0.06 and end at a conversion of ≈0.20, independent of the curing temperature (180–280°C). This observation indicates that small clusters comprising a small oligomer (mainly trimer) surrounded by 6–7 monomers dominate formation of the mesophase which possesses a clearing temperature above at least 280°C. Competition between liquid crystalline order and high crosslink density resulted in a large free volume in the glassy state. This large free volume strongly affects mechanical behavior as well as the glass transition temperature of the LC network.
UV/VIS and NMR spectroscopic studies on the structure of cationically polymerized cyclopentadiene on the surface of silica particles
Authors: Spange Stefan , Langhammer Elke 
Published: April 2003

AbstractThe cationic polymerization of cyclopentadiene (CPD) in the presence of silica gel particles is initiated by triphenylmethyl chloride, triphenylmethyl bromide, and methyl triflate in 1,2‐dichloroethane. The suspension polymerization yields soluble colourless polycyclopentadiene (PCPD) and intensively blue coloured silica particles (PCPD+ silica). The formation of the polymer structure on the silica surface in suspension is followed by transmission UV/VIS spectroscopy and solution (1H and 13C) NMR spectroscopy. The structure of the novel solid materials (PCPD modified silica particles) is additionally investigated by DRIFT spectroscopy, solid‐state 13C CP/MAS NMR spectroscopy and scanning electron microscopy (SEM).The blue colour of the PCPD+ silica particles is caused by polyenylium sequences with five or six conjugated double bonds along the isomerized PCPD chains. The PCPD+ structures are compared with similar ionic model compounds derived from retinol and retinal, respectively. The remaining of the PCPD layer including the conjugated sequences on the surface is attributed to the formation of covalent SiOC bonds. Model reactions of the cationically active PCPD+ silica particles with benzyltriethylammonium chloride and hexachloroantimonate, as well as charge transfer complex formation of the PCPD polymer layer with carbenium salts, (C6H5)3C+AsF and C7HBF, are also investigated. A possible mechanism for the formation of crosslinked PCPD layers on the silica surface is suggested.
Cyclopolymerization, 24. Cyclopolymerizability of an unconjugated triene with functional groups with no homopolymerization tendency: Radical polymerizations of N,N‐diallyl‐2‐(methoxy‐carbonyl)allylamine
Authors: Kodaira Toshiyuki , Liu Qing‐Qing , Urushisaki Michio 
Published: April 2003

AbstractN,N‐Diallyl‐2‐(methoxycarbonyl)allylamine (1a), a trifunctional compound with functional groups of low homopolymerizability, was synthesized and its radical cyclopolymerizability was investigated. Monomer 1a was polymerized to yield high molecular weight polymers with a considerably high polymerization rate; the degree of cyclization (DC) of poly(1a) was about 55%, irrespective of the polymerization conditions, while bifunctional compounds with functional groups of low homopolymerizability have been known to yield highly cyclized polymers. Pendant unsaturations detected in poly(1a) were found to consist almost exclusively of allyl groups. The acryloyl groups and one of the allyl groups of 1a can be regarded as one functional group in a pair with high polymerizability, since N‐allyl‐N‐propyl‐2‐(methoxycarbonyl)allylamine which has the structure of 1a with one of its allyl groups saturated has been known to yield linear polymers with a DC of 100%. This consideration indicates that 1a has similar cyclopolymerizability to unsymmetrical bifunctional monomers the functional groups of which have high and low homopolymerizability. This is the reason why 1a has low cyclopolymerizability, since such unsymmetrical bifunctional monomers have generally low cyclopolymerizability. The high polymerization tendency of 1a is attributed to the high conjugative nature of the acryloyl group as proven by 13C NMR.
Synthesis of molecularly uniform model oligomers for 1,5‐naphthalene diisocyanate and 1,4‐butanediol based polyurethanes by using the 3,5‐di‐tert‐butylbenzyloxy‐carbonyl protective group
Authors: Festel Gunter , Fischer Karl , Eisenbach Claus D. 
Published: April 2003

AbstractA modified benzyloxycarbonyl (BOC) protective group, the 3,5‐di‐tert‐butyl substituted BOC (3,5‐tBBOC) group, was introduced to the stepwise synthesis of molecularly uniform oligourethanes based on 1,5‐naphthalene diisocyanate (NDI) and 1,4‐butanediol (BDO) for the protection of the amino functions of the starting material 1,5‐naphthalene‐diamine (NDA). The tert‐butyl substituents of the 3,5‐tBBOC group significantly improved the solubility of the intermediate products in the oligourethane synthesis. Thus, applying this modified protective group, reactions could be carried out, which were not possible with the conventional BOC group, due to the insolubility of the compounds in all suitable solvents. Furthermore, the substituted BOC protective group considerably improved the efficiency of the liquid chromatographical purification of key intermediates of the synthesis route.
LC‐polyimides, 32. Characterization of the Mitsui‐Toatsu LC‐polyimide and related polyimides
Authors: Schwarz Gert , Sun S.‐J. , Kricheldorf Hans R. , Ohta Masahiro , Oikawa Hideaki , Yamaguchi Akihiro 
Published: April 2003

AbstractTwo polyimides were prepared from 1,3‐bis[4′‐(4″‐aminophenoxy)cumyl]benzene and 1,2:4,5‐benzenetetracarboxylic dianhydride (PMDA) or 1,8:4,5‐naphthalenetetracarboxylic dianhydride. A poly(amide‐imide) was prepared from the same diamine and trimellitic anhydride. Furthermore, two polyimides were prepared from 1,4‐bis‐[4′‐(4″‐aminophenoxy)cumyl]benzene or a mixture of the 1,3‐ and 1,4‐diamines. Moreover, one polyimide was synthesized from PMDA and 1,3‐(4‐aminocumyl)benzene. All polyimides were characterized by elemental analyses, optical microscopy, DSC and various X‐ray measurements. Only the polyimide of PMDA and the 1,3‐amine proved to be thermotropic. SAXS and WAXS measurements between 25 and 350°C, along with a fiber pattern suggest that this LC‐polyimide forms a smectic‐A phase in the melt and a disordered smectic‐B phase in the solid state. Also most other polyimides formed a disordered smectic‐B or a smectic‐A glass in the solid state. However, the polyimide derived from 1,3‐(4‐aminocumyl)benzene crystallized in the form of a smectic‐H phase with tilted mesogens. All results together underline the high potential of polyimides of form layer structures.
Shape memory effect of dehydrochlorinated crosslinked poly(vinyl chloride)
Authors: Skákalová Viera , Lukeš Vladimír , Breza Martin 
Published: April 2003

AbstractCrosslinked poly(vinyl chloride) (CPVC) samples with various extent of dehydrochlorination x, exhibiting a shape memory effect, were prepared. In order to determine the optimal structure for the shape memory effect, electron microscopy, dilatometry, differential thermal analysis (DTA), thermal conductivity and tensile strength measurements were performed. The extremum of all the measured physical properties was found for the sample with x = 12%, corresponding to the optimal structure. The characteristic parameters of the expansion process were calculated from the fits of the experimental data. The extremum was qualitatively predicted by simplified quantum chemical models of a double PVC chain using the semiempirical AMI method. The generalized zip mechanism of CPVC dehydrochlorination might explain the extremum due to mutual chain reorientation with increasing x.
Silver ion‐selective extraction and transport by polystyrene derivatives with pendant ethoxycyclotriphosphazene
Authors: Inoue Kenzo , Ooshita Yuji , Itaya Tomoyuki , Nakahara Hisanori 
Published: April 2003

AbstractStyrene derivatives with pendant cyclotriphosphazenes carrying ethoxy (1) and ethylene glycol monomethyl ether groups (O(CH2CH2)nCH3:2,n= 1;3,n= 2;4,n= 3) and their (co)polymers were prepared, and the selective binding and transport toward silver picrate by these ligands were examined. The extractabilities toward alkali metal and Ag+picrates are significantly affected by the length of side arms on the phosphazene ring, and1extracted only Ag+ion with a moderate efficiency, forming a 1:11‐Ag+complex. Although all of the homopolymers prepared by radical polymerization extracted almost entirely Ag+ion from the aqueous to the dichloromethane phase, the ratio of extracted amount of Ag+ion to alkali metal ions was in the range of 2.5–30. A significant improvement of the extractability toward Ag+ion was observed for poly(1‐co‐MMA) with 38.4 mol‐% of1(copoly(7)), which extracted Ag+ion with a high efficiency (65%) but has negligibly low ability to extract alkali metal ions. Reflecting this, the competitive transport in the Ag+/Na+and Ag+/K+systems with copoly(7) through liquid membrane showed that the rate of Ag+ion was 60 and 85 times higher than those of Na+and K+ions, respectively. The role of cyclophosphazene units in the selective binding and transport of Ag+ion is discussed.
Lightly crosslinked liquid crystalline epoxy resins: The effect of rigid‐rod length and applied stress on the state of order of the cured thermoset
Authors: Giamberini Marta , Amendola Eugenio , Carfagna Cosimo 
Published: April 2003

AbstractLightly crosslinked liquid crystalline epoxy resins were synthesized by reacting rigid rod epoxy‐terminated molecules with decanedioic acid (SA). The obtained networks exhibited a smectic phase even in the case of 2,6‐bis(2,3‐epoxypropoxy)naphthalene, whose aspect ratio is very low. Upon application of uniaxial stress, a smectic phase was surprisingly obtained also for the system obtained by reacting p‐bis(2,3‐epoxypropoxy)‐benzene (QH), whose aspect ratio is practically equal to one, and SA. Stretching of the smectic samples above the glass transition temperature determines orientation of polymer chains, yielding considerably high values of the order parameter S. Thermomechanical analysis showed, for one of these systems, that stretching induces a shift of the isotropization temperature to higher values.
Geometrical structure of star polymers in solution
Authors: Ishizu Koji , Ono Tomohiro , Uchida Satoshi 
Published: April 2003

AbstractPolyisoprene (PI) stars were prepared by copolymerizing PI‐lithium with divinyl‐benzene (DVB) in heptane. The dilute‐solution properties of these stars (arm numbers f = 43–237) were characterized by static and dynamic light scattering (SLS and QELS), and viscometric measurements. From the results of QELS, it could be concluded that the non‐uniformity of the number of arms in PI starts is relatively narrow due to the organized copolymerization of ω‐functional PI‐lithium with DVB in uniform micelles. The ratio of the radius of gyration over the Stokes radius (RG/RH) in cyclohexane decreases gradually and approaches unity as f becomes large. Even PI stars with multiarms behave not as neat hard spheres but as soft spheres which in good solvents were penetratable near the edges.
Preparation of gradient refractive index rods using methyl methacrylate and benzyl salicylate
Authors: Liu Jui‐Hsiang , Liu Hung‐Tsai 
Published: April 2003

AbstractA new method for preparing gradient refractive index (GRIN) rods by using the swollen‐gel polymerization technique was elaborated. The polymerization of MMA (methyl methacrylate) with BSA (benzyl salicylate) was carried out in the presence of BPO (benzoyl peroxide) in a PMMA (poly(methyl methacrylate)) tube. The three‐dimensional refractive index profile of plastic rods was estimated. The dependence of optical properties of the GRIN rod on swelling time, swelling temperature, polymerization temperature and MMA/BSA feed ratio were investigated. Image transmission without distortion is observed through the GRIN rods fabricated in this investigation.
Lamellar diblock copolymers under large amplitude oscillatory shear flow: Order and dynamics
Authors: Wiesner Ulrich 
Published: April 2003

AbstractA survey is given on the effects of large amplitude oscillatory shear (LAOS) flow on the orientation behavior of lamellar polystyrene‐block‐polyisoprene (PS‐b‐PI) diblock copolymers with emphasis on the identification of key parameters that govern the observed behavior. For LAOS at temperatures close to the order‐disorder transition temperature, TODT, three orientation regimes related to the dynamic shear viscosity of the polymers are observed: parallel orientation at high frequencies, perpendicular orientation at intermediate frequencies, and parallel orientation again at very low shear frequencies. In annealing experiments it is found that the low frequency orientation behavior depends strongly on the thermal history of the samples. In conceptually new “dual frequency” experiments the effect of the superposition of two deformation components with frequencies in two different orientation regimes is described. From further studies identifying strain as the control parameter in these nonequilibrium experiments an orientation diagram for the long time orientation behavior of lamellar PS‐b‐PI diblock copolymers is constructed as a function of strain and frequency. For intermediate time scales in the experiments it is shown that the third orthogonal orientation component, the transverse orientation, can be obtained as a transient state. For all orientation components possible orientation mechanisms are discussed.
Anionic homo‐ and block copolymerization of vinylferrocene
Authors: Nuyken Oskar , Burkhardt Volker , Hübsch Christian 
Published: April 2003

AbstractVinylferrocene was polymerized by means of anionic initiators such as n‐BuLi, s‐BuLi and distyryl disodium in tetrahydrofuran as solvent. In all cases the polymerization shows the characteristics of a living polymerization. Depending on the sequence of the monomer addition, either block copolymers of the ABA or the AB type were synthesized.
Functionality type analysis of carboxy‐terminated oligostyrenes by gradient high performance liquid chromatography
Authors: Braun Dietrich , Henze Inka , Pasch Harald 
Published: April 2003

AbstractCarboxy‐terminated oligostyrenes, prepared by radical polymerization using a dicarboxy‐functional initiator, can efficiently be separated by gradient high performance liquid chromatography (HPLC). On a normal phase chromatographic system, comprising a silica gel stationary phase and a tetrahydrofuran‐hexane eluent, elution occurs in the order of increasing polarity of the oligomers and separation into non‐, mono‐, and dicarboxy oligomer fractions is obtained. The chemical structure of the different functionality fractions is determined by matrix assisted laser desorption/ionization mass spectrometry (MALDI‐MS). The results indicate that further functionality fractions in addition to the carboxy oligomers are formed, due to contamination of the initiator or side reactions during the polymerization process.
Anionic ring‐opening polymerization of cyclodisilazanes, 3. Influence of the silicon substituent on the kinetics of polymerization
Authors: Cazalis Chrystelle , Mingotaud Anne‐Françoise , Soum Alain 
Published: April 2003

AbstractThe kinetics of the anionic ring‐opening polymerization of several cyclodisilazanes substituted with different groups on silicon atoms has been investigated in toluene/tetrahydrofuran (THF) using benzyllithium as initiator. Two different behaviours were observed: for hindered substituents (phenyl or allyl), the polymerization is not living; for less hindered groups, the polymerization is living but the rate constants differ markedly from one cyclodisilazane to another. They vary from 9 × 10−4 L · mol−1 · s−1 for DNMeEtDNMe 3 to 0,1 L · mol−1 · s−1 for DDNMe (8). These variations show that the presence of vinyl groups on the monomers tremendously increases the rate of polymerization. In order to discriminate the monomer reactivity from the active center reactivity, a model reaction between lithium silylamides and triethylchlorosilane has been kinetically studied (each lithium silylamide was chosen to modelize one particular active center). Contrary to the corresponding monomers, the less hindered is the silylamide, the faster is the reaction. Thus, the difference of reactivity between the monomers and the reactive center models is so high that the polymerization of cyclodisilazanes can be considered as principally controlled by the reactivity of the monomers.
Propagation rate coefficients in free‐radical homopolymerizations of butyl methacrylate and dodecyl methacrylate
Authors: Buback Michael , Geers Ute , Kurz Caroline H. , Heyne Joachim 
Published: April 2003

AbstractPropagation rate coefficients (kp) for the homopolymerizations of butyl methacrylate (BMA) and dodecyl methacrylate (DMA) were determined by the pulsed laser polymerization (PLP)/size‐exclusion chromatography (SEC) technique. At amibient pressure, the polymerizations of BMA and DMA were studied between −20 and 50°C and between 9 and 60 °C, respectively. For DMA the pressure dependence of propagation rate has been measured up to 1500 bar. The propagation rate coefficients of three major methacrylates (MMA, BMA, DMA) are available over an extended pressure and temperature range. The kp data at identical pressure p and temperature T are close to each other and exhibit a very pronounced family‐type behaviour with respect to both pressure and temperature dependence. The uncertainty of experimental data is estimated to be ± 10 per cent. The imperfect knowledge of the Mark‐Houwink coefficients may give rise to an increased error for the BMA and DMA data which should, however, stay below ± 20 per cent.
Synthesis and controlled release behaviour of dextran bioactive esters by direct reaction of dextran with the potassium salts of bioactive carboxylic acids
Authors: Macias Antonio , Sánchez‐Chaves Manuel , Rodríguez José Luis , Arranz Félix 
Published: April 2003

AbstractThis work deals with the coupling of model bioactive carboxylic acids (1‐naphthylacetic acid, 2‐(6‐methoxy‐2‐naphthyl)propionic acid (naproxen) and nicotinic acid) to dextran by direct reaction with their potassium salts using pyridine/sulfonyl chloride as activating agent. The structure of the resulting polymeric derivatives was determined by means of 1H and 13C NMR spectroscopy. The influence of the pyridine concentration, the type of sulfonyl chloride and the temperature on the reaction of dextran with potassium 1‐naphthyl acetate was evaluated. The activation energy was found to be 65,7 kJ/mol. 13C NMR spectra at 75,4 MHz of partially modified dextran with 1‐naphthyl acetate groups were studied in order to evaluate the selectivity of the reaction between dextran and potassium 1‐naphthyl acetate. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 > C4 > C3. The hydrolysis in the heterogeneous phase of some dextran polymers partially modified with 1‐naphthyl acetate groups shows that the release of the bioactive compound is dependent on the hydrophilic character of the polymer as well as the pH value of the medium.
EXAFS study of supported TiCl4/MgCl2 catalyst
Authors: Potapov Alexandr G. , Kriventsov Vladimir V. , Kochubey Dmitrii I. , Bukatov Gennadii D. , Zakharov Vladimir A. 
Published: April 2003

AbstractExtended X‐ray absorption fine structure analysis (EXAFS) has been used to study supported TiCl4/MgCl2 catalysts containing 1.8 wt.‐% Ti. Adsorbed TiCl4 was found to exist on the MgCl2 surface as a dimeric complex. The possible structures of dimeric TiCl4 complexes on the (100) face of MgCl2 are discussed.