bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvent effects on free‐radical polymerization, 1. Solvent effect on initiation of methyl methacrylate and N‐vinyl‐2‐pyrrolidone
Authors: Czerwinski Wojciech Krzysztof 
Published: April 2003

AbstractInitiation constant 2kd · f, dissociation constant kd, and efficiency factor f of AIBN were measured at 60°C for two model homopolymerization systems: methyl methacrylate (MMA) in N‐methyl‐2‐pyrrolidone (NMP) and N‐vinyl‐2‐pyrrolidone (NVP) in methyl isobutyrate (MiB) as the solvent. The stable Banfield radical was used as inhibitor. A pronounced solvent effect was observed on the side reaction of the inhibitor with the monomers. Particular solvent sensitivity of monomers in this reaction was identified, whereby opposite solvent properties of NMP and MiB as well as of MMA and NVP were found. The initiation constant 2 kd · f depends mainly on the dissociation constant of the initiator kd in regard to its solvent dependence. The efficiency factor f is influenced by monomer concentration, stability (reactivity) of primary radicals and by viscosity of the reaction medium (solvent cage effect).
Polymerization in inverse microemulsions, 3. Copolymerization of water‐ and oil‐soluble monomers initiated by radical initiators
Authors: Vašková Viera , Juraničová Viera , Bartoň Jaroslav 
Published: April 2003

AbstractThe copolymerization of acrylamide with methyl methacrylate or styrene in inverse microemulsion initiated by radical initiators with different solubility in water was studied in the initial stages of the reaction. It was found that the initial rate of copolymerization depends on the mole fraction of acrylamide in the comonomer mixture and is independent of the solubility of the radical initiator in water.
Determination of the microstructure of poly(chlorophenyl methacrylates) by 13C NMR spectroscopy
Authors: Hiller Wolf‐Gerald , Pasch Harald , Lampe Irene v. 
Published: April 2003

AbstractPoly(chlorophenyl methacrylate)s with varying number and positions of the chloro substituent were prepared and investigated using 13C NMR spectroscopy. The tactic sequence distribution was determined from the signals of the carbonyl carbon (pentads) and the α‐methyl carbon atoms (triads). It was found that the polymers are predominantly syndiotactic with an average sequence length of between 3 and 4. The isotactic sequences accounted for a very small fraction of the polymer chain with an average sequence length of between 1,3 and 1,5. As for the signals of the aromatic carbon atoms it could be demonstrated that, depending on the substitution pattern of the aromatic ring, the sensitivity on sequence distribution was more or less pronounced.
Telechelic poly(ε‐caprolactone) terminated at both ends with OH groups and its derivatization
Authors: Sosnowski Stanislaw , Slomkowski Stanislaw , Penczek Stanislaw , Florjanczyk Zbigniew 
Published: April 2003

AbstractThe synthesis of highly uniform (1,08 ≤ Mw/Mn ≤ 1,13) telechelic poly(ε‐caprolactone) terminated at both ends with OH groups and its derivatization leading to poly(ε‐caprolactone) with pyrene end‐groups are described. The synthesis, carried out in THF at room temperature, involves initiation with (CH3CH2)2AlO(CH2CH2O)3Al(CH2CH3)2, leading to poly(ε‐caprolactone) macromolecules growing at both ends. The active centers were deactivated with acetic acid, giving macromolecules with OH end‐groups. Reaction of α,ω‐dihydroxypoly(ε‐caprolactone), HO‐poly(εCL)‐OH, with 4‐(1‐pyrenyl)butyryl chloride yields α,ω‐di‐1‐pyrenylpoly(ε‐caprolactone), Py‐poly(εCL)‐Py. Polymers are characterized by GPC, 1H NMR, and UV spectroscopies. The UV spectra of polymers with pyrene end‐groups are compared with the UV spectra of the model compound.
Preparation and polymerization of dimethylamino(methyl)styrenes
Authors: Kitayama Tatsuki , Masuda Eiji , Hatada Koichi 
Published: April 2003

AbstractThree isomers of methylstyrene derivatives with a dimethylamino group in ortho position to the methyl group were prepared through the coupling reaction of the corresponding Grignard reagent and vinyl bromide using a Pd(0) catalyst, and their radical and anionic polymerization was examined. Monomer reactivity ratios in the radical copolymerization with styrene indicate that 3‐dimethylamino‐4‐methylstyrene (3‐DMA‐4‐MS) and 4‐dimethylamino‐3‐methylstyrene (4‐DMA‐3‐MS) have a higher reactivity than styrene, while the reactivity of 3‐dimethyl‐amino‐2‐methylstyrene (3‐DMA‐2‐MS) is lower than that of styrene. The 13C NMR chemical shift of vinyl carbons as well as the e‐values indicate that the electron density at the vinyl carbons of 3‐DMA‐4‐MS and 4‐DMA‐3‐MS is increased by the electron donating effect of the dimethylamino group, which results in lower reactivity of the monomers in anionic polymerization. The anionic copolymerization with 1,1‐diphenylethylene gave an alternating copolymer. In the anionic polymerization of 3‐DMA‐2‐MS, proton transfer reaction from the methyl group to the propagating chain end occurred to some extent to incorporate o‐phenylene units in the chain.
Thermal solid state polymerization of deuterated 2,4‐hexadiynylene di‐p‐toluenesulfonate: The topotactic reaction of topospecifically modified diacetylene derivatives
Authors: Gruner‐Bauer Petra , Müller Irene , Dormann Elmar , Kröhnke Christoph 
Published: April 2003

AbstractThe thermal solid state polymerization was analysed for topospecifically deuterated derivatives of 2,4‐hexadiynylene di‐p‐toluenesulfonate (PTS). Deuteration of the methylene groups close to the diacetylene‐monomer triple bonds influences drastically the length of the induction period and the reaction‐rate constants in the autocatalytic period. These peculiarities were investigated by the combination of dielectric permittivity measurements with differential scanning calorimetry and gravimetrical analyses of the solid state polymerization.
Modification of isotactic poly(propylene) with a nitrogen plasma; differences in comparison to the treatment with a carbon dioxide plasma
Authors: Poncin‐Epaillard Fabienne , Chevet Bruno , Brosse Jean‐Claude 
Published: April 2003

AbstractThe modification of isotactic poly(propylene) by nitrogen plasma treatment was studied in comparison to the use of a carbon dioxide plasma, which was reported earlier. The effect of the modification was characterized with secondary ion mass spectrometry (SIMS) to a depth of 3 Å, with electronic spectroscopy for chemical analysis (ESCA) to a depth of 20 Å and with attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR) to a depth of 10 μm: the nitrogen plasma modification seems to be milder than the CO2 plasma treatment. Surface degradation is a minor reaction, and in an opposite manner, crosslinking and functionalization (formation of primary amino groups) are the most important reactions. Radicals, probably originating from the elimination of [methyl groups] along the polymer backbone, could induce these reactions.
Graph theory of configurational and viscoelastic properties of polymers, 7. Chains containing large copolymeric blocks
Authors: Yang Yuliang 
Published: April 2003

AbstractThe graph theory of configurational and viscoelastic properties of polymers developed by the author is extended to treat chains containing large copolymeric blocks. The analytical expressions of zero‐shear‐rate viscosity, η0, and the radius of gyration weighted by the friction coefficients of beads, 〈S2〉ρ, of AB and ABA type block copolymer chains are obtained.
Synthesis and properties of quasi‐rigid polyesters containing 2,5‐disubstituted tetrahydropyran rings in their main chains
Authors: Atsumi Miharu , Okada Masahiko , Sumitomo Hiroshi , Yamada Satoru 
Published: April 2003

AbstractA polyester composed of trans‐2,5‐linked tetrahydropyran rings (4t) was synthesized by direct polycondensation of trans‐5‐hydroxytetrahydropyran‐2‐carboxylic acid (5t) using N‐methyl‐2‐chloropyridinium iodide or triphenylphosphine and hexachloroethane as condensing agents in pyridine at 25 or 50°C. The hydroxycarboxylic acid 5t was polymerized also with dibutyltin oxide, although longer reaction times were required. The polyester 4t is soluble in m‐cresol and halogenated protic solvents such as 2,2,2‐trifluoroethanol, trifluoroacetic acids and dichloroacetic acid, but insoluble in chloroform and dichloromethane in which the corresponding cis‐isomer (4c) composed of cis‐2,5‐linked tetrahydropyran rings is soluble. According to conformational energy calculations, the repeating unit exists predominantly as a conformer in which both the exocyclic oxygen and the carbonyl carbon in the backbone of the chain are located in the equatorial positions of the tetrahydropyran ring; in other words, the chain of 4t takes a linear conformation. On the other hand, the exocyclic oxygen in the repeating unit of 4c occupies an axial position of the tetrahydropyran ring and the chain is winding. Conformational energies for dimer models for 4c and 4t were also estimated by means of force field calculations. These polyesters are partially crystalline according to their X‐ray diffraction patterns. Both polyesters show birefringence at or above 200°C. The polyesters 4c and 4t decompose at 300°C in nitrogen atmosphere, approximately 150°C higher than the isomeric polyester 2.
Propene polymerization with a Mg(OC2H5)2‐supported TiCl4 catalyst, 3. The role of benzoyl chloride
Authors: Jeong Young‐tae , Lee Dong‐ho , Shiono Takeshi , Soga Kazuo 
Published: April 2003

AbstractThe catalyst systems Mg(OC2H5)2/benzoyl chloride (BC)/TiCl4 and Mg(OC2H5)2/ethyl benzoate (EB)/TiCl4 were prepared for the polymerization of propene. In case of the Mg(OC2H5)2/BC/TiCl4 catalyst, BC changes into the internal donor EB during the in situ preparation of the catalyst and the unchanged BC acts as additional donor after reaction with triethylaluminium (TEA). Catalyst activity and isospecificity were also studied for the two catalysts by changing the amounts of BC or EB in the polymerization of propene cocatalyzed with TEA.
Fast living cationic polymerization of isobutyl vinyl ether and related vinyl ethers by C2H5AlCl2 in the presence of ClCH2COOCH3
Authors: Aoshima Sadahito , Shachi Kenji , Kobayashi Eiichi 
Published: April 2003

AbstractFast living cationic polymerization of isobutyl vinyl ether (IBVE) was examined using the initiating system 1‐(isobutoxy)ethyl acetate (1)/C2H5AlCl2 in the presence of various esters in hexane between 0°C and +40°C. Methyl chloroacetate as added ester turned out to be effective: the apparent polymerization rate constant k was larger by a factor of 400 – 500 than that in the presence of methyl acetate. The rate difference was explained on the basis of the basicity of the esters and their nucleophilic interaction with the propagating species. The polymers obtained in the presence of both esters had a narrow molecular‐weight distribution (MWD) (Mw/Mn ≤ 1,1), and Mn was directly proportional to monomer conversion. As low reactive monomers, 2‐chloroethyl vinyl ether (CEVE) and tert‐butyldimethylsilyl vinyl ether (SiVE) were polymerized under similar conditions. By selecting methyl chloroacetate as an additive, in the case of CEVE, fast living polymerization was achieved to give quantitative conversion within 10 min at 0°C; in the case of SiVE, polymers with a narrow MWD were obtained even at −20°C in high yield, whereas hardly any polymerization of SiVE occurred in the presence of methyl acetate.
The influence of the length of alkoxy side groups on the phase state of polydialkoxyphosphazenes
Authors: Tur Dzidra R. , Provotorova Natalia P. , Vinogradova Svetlana V. , Bakhmutov Vladimir I. , Galakhov Michail V. , Zhukov Valery P. , Dubovik Irina I. , Tsvankin Daniil Ja. , Papkov Vladimir S. 
Published: April 2003

AbstractPolydialkoxyphosphazenes with different substituents varying from methoxy up to octoxy which contain only minor amounts (below 0,1 mol‐%) of various defective units in their macromolecules were synthesized. It was shown that such polyphosphazenes with propoxy, butoxy and pentoxy side groups can exist in the mesomorphic state and that a defect content as low as about 2 mol‐% prevents mesophase formation. In spite of high flexibility of the main chain, the polydialkoxyphosphazenes were found to gain the ability to crystallize only if the number of C atoms in the alkoxy substituents is higher than six.
Steric environments of radicals produced by addition of tert‐butoxyl radicals to dialkyl maleates as studied by spin trapping with 2,4,6‐tri‐tert‐butyl‐1‐nitrosobenzene
Authors: Yamada Bunichiro , Yoshikawa Eiichiro , Otsu Takayuki 
Published: April 2003

AbstractRadicals produced by the addition of tert‐butoxyl radicals to maleic esters were spin‐trapped with 2,4,6‐tri‐tert‐butyl‐1‐nitrosobenzene (BNB). Although this does not yield polymers, the radicals resulting from the former addition were further added to maleate thus extending the chain length to a limited extent prior to the reaction with BNB. Increasing the bulkiness of the ester alkyl group and the chain length brought about considerable steric hindrance against the reaction with BNB as evidenced by an increase in the amount of N‐(alkoxy)phenylaminyl radicals in the spin adduct. The steric effect was found to arise already at the stage of short chain lengths (trimers): The radical consisting of two maleate units and bearing a tert‐butoxy end group seems to be less hindered than the longer homologues.
Telechelics via addition of dithiols onto diolefins, 3. Heat‐resistant polysulfides from 1,3‐benzenedithiol and norbornadiene
Authors: Nuyken Oskar , Völkel Thomas , Pöhlmann Thomas 
Published: April 2003

AbstractThe addition of an aromatic dithiol (1,3‐benzenedithiol) (3) onto a strained, unsaturated ring such as norbornadiene is studied. The average degree of polymerization depends on the stoichiometric ratio of the reactants. The functional end‐groups of the polymers are determined by the component used in excess. The resulting polymer is heat‐resistant up to 400°C. Non‐stoichiometric ratios of the reactants yield telechelics with thiol and vinyl end‐groups. By reaction with selected, suitable compounds a great variety of possible functional end‐groups can be obtained.
Emulsion polymerization of butadiene, 3. Kinetic effects of stirring conditions and monomer/water ratio
Authors: Weerts Pierre A. , Van der Loos Jos L. M. , German Anton L. 
Published: April 2003

AbstractThe stirring speed n influences the emulsion polymerization of butadiene, (1) by reducing the effective emulsifier concentration [E]eff available for particle nucleation and stabilization at high n, and (2) by limiting diffusion of monomer to the latex particles at low n. The large density difference between butadiene and water promotes the breaking up of droplets at high n, while the same condition constitutes a large driving force for (partial) phase separation at low n. Increasing the monomer/water ratio at constant [E] decreases [E]eff, and thus the final particle number. At monomer volume fractions >0,6 mixed emulsions are likely to be formed initially, reducing [E]eff even further. In the presence of mixed emulsions, polymerization in the monomer phase may no longer be neglected, giving rise to a complex kinetic behaviour.
Gas permeation through a side‐chain liquid‐crystalline polysiloxane‐based membrane
Authors: Chen Deng‐Shan , Hsiue Ging‐Ho , Hsu Chain‐Shu 
Published: April 2003

AbstractA membrane was prepared by sandwiching the side‐chain liquid‐crystalline polysiloxane (LCP) 3 between two porous poly(propylene) (Celgard) films. Permeation properties for H2, O2, N2, CH4 and CO2 through the side‐chain LCP‐based membrane was measured using a gaschromatographic method at several different temperatures corresponding to the different states of the side‐chain LCP. The gas permeation behaviour depends strongly on the different states of the side‐chain LCP. The plots of permeability versus reciprocal temperature show an abrupt change of the slope in the vicinity of the glass transition temperature (Tg) of the side‐chain LCP for all five gases. The activation energy for permeation obtained at these different states exhibits different values. The value obtained in the liquid‐crystalline state is the highest. Separation factors (PO2/PN2) and (PCO2/PCH4) exhibit an unusual behaviour when the temperature changes across Tg. They increase abruptly when the temperature increases and the phase changes from the glassy state to the liquid‐crystalline state of the side‐chain LCP. The fact that both permeability and selectivity increases with increasing temperature above the glass transition is attributed to the supermolecular arrangement of the liquid‐crystalline state of the side‐chain LCP.
Regular folding in solution‐grown polyethylene crystal, 1. Model description
Authors: Chang Hwei‐Liang , Hu Andrew Teh 
Published: April 2003

AbstractTo re‐consider the idea that a polymer chain should fold regularly rather than randomly, the pair s‐chain crystalline growth philosophy was suggested. On the basis of this philosophy, the coordinated pair chain folding model (CPCFM) for polyethylene (PE) polymer single crystal is proposed, with the paired chain folding on average along the (110) plane of the orthorhombic crystal lattice and each of the coordinated pair chains folding alternatively at (100) and (010) planes. Being a regular folding model, the CPCFM explains most of the regular shapes of PE single crystals including lamellar diamond shape, flat based and non‐flat based hollow pyramidal shapes, saddle shape, truncated diamond shape as well as twin crystal via either the single‐chain nucleus or the two‐chain nucleus. The folding conformation energies for the folds in a CPCFM are lower than those for conventional adjacent (110) folds. The configuration and conformation mentioned above, together with other evidences, discussed in part 2 of this series and an earlier communication make the CPCFM an acceptable regular folding model.
Uniform tri(oxyalkylene)s. Preparation and characterisation
Authors: Bedells Alison D. , Mobbs Richard H. , Booth Colin 
Published: April 2003

AbstractMethods for the preparation and purification of uniform tri(oxyalkylene)s from the C3 to C6 alkanediols are described. The preparation of the pure C3 trimer [α‐hydro‐ω‐hydroxy‐tri(oxytrimethylene)] is reported for the first time.
Oligomerization of 1‐hexene initiated by Zr(OnPr)4‐AlEt2Cl, 1. Influences of reaction parameters on kinetics and products' distribution
Authors: Liu Hua Qin , Deffieux Alain , Sigwalt Pierre 
Published: April 2003

AbstractAs part of our investigation of high α‐olefin oligomerization initiated by the complexation of a transition metal (Ti and Zr) compound with an organoaluminium derivative, the oligomerization of 1‐hexene initiated by Zr(OnPr)4‐AlEt2Cl was studied in detail at 20°C. It was found that a high mole ratio of [Al]/[Zr] (>5) was necessary in order to observe activity for 1‐hexene oligomerization. The highest activity was obtained for ratios ranging from 12 to 15. The products formed were mainly dimers, addition products of the ethyl group to 1‐hexene, and isomers of 1‐hexene. The corresponding saturated alkanes were also formed in large amount. Their relative percentage is proportional to the mole ratio of [Al]/[1‐hexene].
Preparation of sodium 13‐tetradecenoate and its polymerization under irradiation with UV light
Authors: Arai Kenichiro , Miyahara Shigeyoshi , Okabe Toshio 
Published: April 2003

AbstractSodium 13‐tetradecenoate(1) was synthesized as an amphiphile which contains a double bond at the chain end. The micelle formation behavior of 1 was examined by measuring the electric conductivity of its aqueous solutions; the pre‐critical micelle concentration (pre‐CMC) and genuine critical micelle concentration (CMC) were estimated to be 0,021 and 0,066 mol · L−1, respectively. Polymerization of 1 under irradiation with UV light was investigated; only a small amount of polymer was obtained at concentrations below the pre‐CMC, while this amount increased rapidly with increasing concentration of 1 above the pre‐CMC. Pre‐CMC and CMC of the obtained polymer were also examined and found to be 2,8 · 10−4 and 4,5 · 10−3 mol · L−1, respectively. The number‐average degree of polymerization (D̄P̄n) of poly(1) was about 23, the value of which was nearly in accord with the aggregation number of monomer 1, which was estimated by means of measurement of osmotic pressure of aqueous solutions of monomer 1. These results are compared with those of sodium 10‐undecenoate.
Theoretical study of resonant microwave absorption by DNA in aqueous solution
Authors: Fisun Oleg I. , Katanaev Michael O. 
Published: April 2003

AbstractTheoretical analysis of resonant microwave absorption of cloned linear DNA in aqueous solution is given. To this end we calculate the absorption of electromagnetic waves by an ensemble of linear harmonic chains modelling DNA molecules in solution. The absorption depends crucially on the boundary conditions for the DNA molecules. To obtain proper boundary conditions the solvent is considered as a non‐Newtonian fluid of the second order in this frequency range. Calculated values of the resonant absorption coefficient are in agreement with recently found experimental data.
Langmuir‐Blodgett mono‐ and multilayers of preformed poly(octadecyl methacrylate)s, 1. Surface‐area isotherms of atactic and isotactic poly(octadecyl methacrylate)s and transfer into multilayers
Authors: Schouten Arend Jan , Wegner Gerhard 
Published: April 2003

AbstractIn order to elucidate some of the parameters controlling the transfer of compressed monomolecular layers of preformed poly(octadecyl methacrylate)s (PODMA) onto substrates by the so‐called Langmuir‐Blodgett technique, an investigation was undertaken of PODMA's of different tacticity and different molecular weights. For the preparation of multilayered structures it was necessary to decrease the interaction between the side chains. This could be accomplished by introducing side chain inhomogeneities especially in the form of comonomers with shorter alkyl side chains. The transferability of a monolayer could be correlated with features in the pressure‐area diagrams, as there is a liquid‐analogous state formed when shorter alkyl chains are introduced; moreover a partial “melting” with lowering of the collaps pressure of the layer is seen. It appeared that with isotactic PODMA regular Y‐type transferY‐Type transfer: During one dipping and withdrawing cycle, two layers are transferred. Z‐Type transfer: Only during withdrawing one layer is transferred.
took place, whereas with the atactic polymers at the beginning a Z‐type transfer occurred, gradually changing into a Y‐type transfer. Applying the concept of decreasing interaction of the side chains it was possible to prepare multilayers of isotactic and atactic PODMA's.
Langmuir‐Blodgett mono‐ and multilayers of preformed poly(octadecyl methacrylate)s, 2. Structural studies by IR spectroscopy and small‐angle X‐ray scattering
Authors: Arndt Thomas , Schouten Arend Jan , Schmidt Günther F. , Wegner Gerhard 
Published: April 2003

AbstractLangmuir‐Blodgett (LB) mono‐ and multilayers of preformed atactic and isotactic poly(octadecyl methacrylate)s were studied on gold surfaces and silicon wafers. The average orientation of the carbonyl bond of the ester group was found to be about 50° with respect to the normal to the substrate, and the side chains were concluded to be oriented perpendicular to the substrate. Furthermore, the degree of side chain orientation increased on going from a single monolayer to a multilayer. This is explained by an interdigitation of the side chains during or after the transfer process. A peculiar transfer behavior of the atactic samples is discussed in terms of the effect of disorder of the first layer on the transfer process. On heating multilayers of the polymers, melting of the crystalline domains formed by the side chains was observed at temperatures of about 35°C to 40°C. However, the layer structure appeared to be stable up to 100°C. The oriented structure was completely recovered after cooling down to room temperature.