bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical opalescence of polymer solutions at high pressures
Authors: Kiepen Friedheinz , Borchard Werner
Published: April 2003

With a new type of high‐pressure cell the angular dependence of light scattering intensities at scattering angles θ between 30° and 150° can be measured as a function of pressure P. The linear extrapolation of (Iθcorr)−1 as a function of sin2 (θ/2) to θ = 0 does not show an angular dependence of the scattering intensities. For this result the term including sin2 (θ/2) in Debye's equation for the critical opalescence vanishes. The reason for this is probably due to the low molar mass of the polystyrene (number‐average molar mass M̄n = 1 000 g/mol). This means that the range of molecular forces of a polymer/solvent system is too small to be detected by light scattering. A second linear extrapolation of (Iθcorr)−1 to θ = 0 as a function of P yields the spinodal points of the system polystyrene/pentane in the temperature‐pressure‐concentration diagram.
Polymers with carbazolyl groups, 3 Fluorescence properties of some polysiloxanes with pendant carbazolyl groups
Authors: Hennecke Manfred , Strohriegl Peter
Published: April 2003

The polarized fluorescence spectra and the time‐resolved fluorescence decay of some novel carbazole‐containing polysiloxanes were measured in solution and in the solid state. The fluorescence data show that these polymers, due to the conformational freedom of the carbazole group, are free of excimer‐forming sites. As indicated by the extensive fluorescence depolarization in solid solution, the migration of excitation energy along the chain is fast with respect to the fluorescence lifetime, and the number of migrational steps comes up to the number of chromophores per chain. If the polymers were prepared starting from commercial carbazole (which contained small amounts of aromatic impurities), the occurrence of sensibilized benzocarbazole‐like fluorescence in the solid state and in concentrated solution demonstrates the high efficiency of transferring the excitation energy to a suitable acceptor.
Effect of cationic surfactants on the permeability across a membrane of poly[butyl methacrylate‐co‐N‐methyl‐N‐(4‐vinylphenethyl)ethylenediamine]‐graft‐poly(L‐glutamic acid)
Authors: Chung Dae‐won , Kurosawa Koichi , Maeda Mizuo , Inoue Shohei
Published: April 2003

The effects of three cationic surfactants, dodecylammonium chloride (C12N+), dodecyldimethylammonium chloride (C12N+ 2C1), and dodecyltrimethylammonium chloride (C12N+ 3C1), on the permeability of 1‐phenyl‐1,2‐ethanediol were investigated for the membrane of poly[butyl methacrylate‐co‐N‐methyl‐N‐(4‐vinylphenethyl)ethylenediamine]‐graft‐poly(L‐glutamic acid) (PLGA) (1b), the permeating pathway being composed of the polypeptide domain. The membrane treated with a surfactant shows a decrease in permeability due to the coil‐to‐helix transition of PLGA induced by the surfactant. The effects of the three surfactants on the permeability was found to be of the order: C12N+ > C12N+2C1 > C12N+3C1.
Photoinitiators and photoinitiation, 8 The photoinduced α‐cleavage of acylphosphine oxides. Identification of the initiating radicals using a model substrate
Authors: Baxter Jane E. , Davidson R. Stephen , Hageman Hendrik J. , Overeem Ton
Published: April 2003

The photodecomposition of diphenyl‐2,4,6‐trimethylbenzoylphosphine oxide (1) was studied both in solution at 40°C and in thin films in the presence of 1,1‐di‐p‐tolylethylene as a model substrate for vinyl monomers. Both primary radicals resulting from α‐cleavage of 1 were found to add to the olefinic double bond of the model substrate (initiation). The diphenylphosphinoyl radical (3) proved to be twice as effective as the 2,4,6‐trimethylbenzoyl radical (2) under all conditions. Oxygen (air) considerably reduced the initiating efficiencies fp, in particular fp(2) (of radical 2). The addition of triethylamine partially restored the overall initiating efficiency in all likelihood by oxygen scavenging. A direct contribution of triethylamine‐derived radicals to the initiation was not observed.
Crystallinity and thermal behaviour of trans‐poly(1‐octenylene)
Authors: Schneider Wolfgang A. , Müller Michael F.
Published: April 2003

The commercially available poly(1‐octenylene) Vestenamer® formed by the metathetic polymerization of cyclooctene with a tungsten catalyst, is highly crystalline at room temperature; it shows specific properties as a blend component, thus favourably influencing the processing characteristics and the final product quality. Differential scanning calorimetry, infrared and torsion pendulum experiments indicate that the melting temperature and the degree of crystallinity depend on the concentration of trans double bonds, on their distribution along the polymer chain as well as on the sample history. The formation of crosslinks induced by very intensive UV irradiation of 100 μm thin films leads to a reduction of the melting temperature and the crystallinity. A correlation between stiffness (shear modulus G′) and crystallinity was found for samples with varying amounts of trans double bonds.
Polymerization of macromonomers, 3. Monomer reactivity ratios in radical copolymerization of poly(tetrahydrofuran) macromonomers with 2‐vinylnaphthalene
Authors: Asami Ryuzo , Takaki Mikio , Matsuse Takashi
Published: April 2003

Methacrylate‐terminated poly(tetrahydrofuran) (MA‐PTHF) and acrylate‐terminated poly‐(tetrahydrofuran) (A‐PTHF) macromonomers (M2) were radically copolymerized with 2‐vinylnaphthalene (2‐VN, M1). The composition of copolymers was determined by UV spectroscopy taking advantage of the very high absorption coefficient (UV) of the monomeric units of 2‐VN in copolymer. The monomer reactivity ratios r1 and r2 evaluated are as follows. MA‐PTHF: r1 =1,3 ± 0,21, ± 0,05; A‐PTHF: r1 = 2,5 ± 0,35, r2 = 0,10 ± 0,05. These reactivity ratios were compared with those in the copolymerizations of 2‐VN with the corresponding small monomers and were discussed in terms of polymer (hindering) effect and the concept of equal reactivity of growing chain.
Optically controlled ligand delivery, 1. Synthesis of water‐soluble copolymers containing photocleavable bonds
Authors: Yen Hung‐Ren , Kopeček Jindřich , Andrade Joseph D.
Published: April 2003

To verify the possibility of developing a ligand delivery system which is controlled by light pulses, we synthesized copolymers of N‐(2‐hydroxypropyl)methacrylamide (1) containing sidechains terminated in ligands (Boc‐Gly, fluorescein, tetramethylrhodamine) bound via photocleavable 2‐nitrobenzyl groups. Copolymers in solution were exposed to light of wavelength ≈︁ 360 nm which resulted in release of the bound ligands. Depending on the experimental conditions (type of solvent, presence of oxygen) changes in the structure of released fluorochromes were observed (photofading effect). These effects were quantified by determining the binding constants of released modified fluorochromes with monoclonal antifluorescyl anti‐bodies.
Electron transfer from carbanionic salts to linear sequences of conjugated double bonds, 2. Reaction with trans‐β‐carotene
Authors: Rudatsikira Alphonse , François Bernard , Mathis Claude
Published: April 2003

The reactions of a set of organoalkaline compounds with trans‐β‐carotene (Car) were studied in solution (using UV/Vis, ESR, and mass spectroscopy) and compared with the reactions of the same set with insoluble polyacetylene. It was shown that the naphthalene radical ion and the dicarbanionic dimer of 1,1‐diphenylethylene, 1,1,4,4‐tetraphenyl‐1,4‐butanediide, react with Car by a simple electron transfer leading to Car radical ion and dianion. This dianion is protonated by methanol mainly at carbon 7 or 7′. On the contrary of diphenylalkyllithium compounds add to Car double bonds. This addition of 1 mol of diphenylalkyllithium per Car takes place mainly at the central double bond. sec‐Butyllithium (sec‐BuLi) reacts also by addition to Car. The addition products are in some cases instable and decompose to radical ions through a non‐elucidated mechanism. These transfer or addition reactions with Car, as well as the exclusive electron transfer observed with polyacetylene, are rationalized on the basis of the relative redox potentials of reactants.
Sulfopropylated hemicellulose: Synthesis and NMR characterization
Authors: Focher Bonaventura , Marzetti Annamaria , Naggi Annamaria , Torri Giangiacomo
Published: April 2003

Sulfopropylation of hemicelluloses was achieved in dimethyl sulfoxide solution. The progress of sulfopropylation reaction was studied as a function of the dimsyl/hemicellulose ratio, reaction time with dimsyl (dimethylsulfinyl carbanion), propanesultone/hemicellulose ratio, and reaction time with propanesultone. The degree of substitution of sulfopropylhemicelluloses ranged between 0,5 and 1,1 as a function of experimental conditions. Intrinsic viscosity (0,1—0,3 dl/g) and molecular weight measurements (15000 g.mol—1) showed a controllable degradation of hemicellulose chains during the reaction. The NMR characterization of enzymatically degradated sulfopropylhemicelluloses indicated a homogeneous substitution along the polysaccharide chains. A significant regioselectivity for the OH‐2 hydroxyl groups was observed only for DS ≤ 0,5.
Blends of poly(tetramethylene terephthalate) with a liquid‐crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate), 2. Crystallization kinetics and melting behaviour
Authors: Pracella Mariano , Chiellini Emo , Dainelli Dario
Published: April 2003

The isothermal crystallization kinetics, the morphology and melting behaviour of blends of poly(tetramethylene terephthalate) {poly(butylene terephthalate), (PBT)} with a thermotropic liquid‐crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) (HTH10), were studied in the composition range 0—50 wt.‐% of HTH10 by optical microscopy and differential scanning calorimetry. The spherulite growth rate and the overall crystallization rate of PBT from melt blends are markedly depressed by the presence of the mesomorphic component. Changes of superstructure and of primary nucleation density of PBT spherulites in the blends were observed. The analysis of the melting behaviour of these samples indicates that the stability of PBT crystals and their reorganization processes on heating are dependent on the blend composition. A decrease of the equilibrium melting temperature of PBT is found with increasing the amount of HTH10. According to previously reported investigations on the same system, the results are discussed in respect of the onset of interactions between the two polymers in the liquid state.
On the reaction of catenapoly(diphenoxy‐λ5‐phosphazene) with sulfur trioxide
Authors: Montoneri Enzo , Gleria Mario , Ricca Giuliana , Pappalardo Giuseppe C.
Published: April 2003

The reaction of catenapoly(diphenoxy‐λ5‐phosphazene) (1) with SO3 in 1,2‐dichloroethane at 15°C, applying a mole ratio m = [SO3]/[‐–P(OC6H5)2N—] ≤ 1,0 and subsequent quenching with water, leads to catenapoly(diphenoxy‐λ5‐phosphazene‐co‐diphenoxy‐λ5‐phosphazenium hydrogen sulfate) (2) containing up to 57% protonated nitrogen. At m > 1,0 C‐sulfonation occurs, resulting in the formation of water‐soluble catenapoly[diphenoxy‐λ5‐phosphazene‐co‐diphenoxy‐λ5‐phosphazenium hydrogen sulfate‐co‐bis(sulfophenoxy)‐λ5‐phosphazenium hydrogen sulfate] (3). The latter can be converted into catenapoly[diphenoxy‐λ5‐phosphazene‐co‐bis(sulfophenoxy)‐λ5‐phosphazene] (4b) by treatment with alkali and subsequent percolating through a cation exchange resin. Analytical results show that C‐sulfonation is preceded by the formation of a polymer‐SO3 donor‐acceptor complex.
Synthesis of polysulfone‐block‐polysiloxane copolymers, 4. A model study of the limitation of hydrosilylation coupling
Authors: Torrès Ghislaine , Madec Pierre‐Jean , Maréchal Ernest
Published: April 2003

Hydrosilylation reactions of 1‐allyloxy‐3‐phenoxy‐2‐propanol (3) as model compound were carried out with α‐dimethylsilyl‐ω‐hydrooligosiloxane (7; M̄n = 1200) in the presence of hexachloroplatinic acid. It was found that under stoichiometric conditions only 75‐–80% of the allyl groups were hydrosilylated, due to some isomerization of the allyl groups into vinyl groups, which do not undergo hydrosilylation. This isomerization could be shown to be sensitive to the type of the allyloxy structure. Thus, for example, allyloxybenzene does not undergo isomerization.
Stereospecific functionalization of poly(vinyl chloride)
Authors: Millán José‐Luis , Martínez Gerardo , Mijangos Carmen , Gómez‐Daza Mariano
Published: April 2003

The substitution reaction of PVC with sodium dimethyldithiocarbamate (NaDC) and sodium azide (NaN3) was performed in cyclohexanone and dimethylformamide at various temperatures. The degree of compositional heterogeneity was estimated and found to be important up to conversions of about 0,5%, but to vanish afterwards. The evolution of unreacted iso, hetero and syndiotactic triads was measured by 13C NMR spectroscopy. For conversions of at least up to 12%, the content of both the isotactic and heterotactic triads was found to decrease, relative to the syndiotactic ones, but at different relative rates depending on the nucleophile. From these results, together with the kinetic ones, it is concluded that the reaction proceeds by a stereoselective mechanism. The results are discussed on the basis of a hypothesis concerning the role of the local triad conformations in PVC that contain the TT isotactic diad conformation. The results enable the selective substitution of PVC with NaDC and NaN3, which may be used as a useful tool to prepare specific graft copolymers based on PVC.
Condensation polymerization of 2,2′‐diiodobiphenyl‐4,4′‐dicarbonyl dichloride with some mono‐ and dihydroxy aromatic compounds
Authors: Banihashemi Ahmad , Ameri Farahnaz
Published: April 2003

Several potentially thermostable polyesters 3a–1 were prepared by Schotten‐Baumann condensation of 2,2′‐diiodo‐4,4′‐biphenyldicarbonyl dichloride (1) with several aromatic hydroxy compounds 2a–1. The reactivity of 1 towards various phenols was tested and the spectra of the resulting model compounds 4a–d were compared with those of the polymers. With some exceptions (3h and 3c) the polyesters were found to be soluble in organic solvents. Their inherent viscosities vary between 0,1 and 0,45 dl · g−1 (in CHCl3 at 25°C). The values of the inherent viscosity were in the range of 0,06–0,45 dl/g (c = 0,2 g/dl in CHCl3 at 25°C). The melting points of the polymers were found to be higher than 300°C.
Polymerization of 1‐alkynes initiated by transition metal carbene complexes, 2. Kinetics and mechanism of the initiation reaction
Authors: Lucas Christine , Soum Alain , Fontanille Michel
Published: April 2003

A kinetic study of the initiation reaction of alkyne polymerization by a transition metal intramolecular coordinated carbene complex, was carried out. It showed that there is a slow disappearance of the initial carbene and simultaneously appearance of both active species and organic side‐products. Their structures were determined by GC‐MS. The apparent rate constants of both initiation and side‐reactions were measured and the corresponding thermodynamic parameters established. According to the experimental results, a mechanism of the initiation reaction is proposed. In the first step a replacement of the intramolecular double bond of the initiator by the triple bond of a monomer molecule takes place and in the second step the insertion of the monomer. The resulting carbenic active species may lead either to organic products via cyclopropanation reaction or to a high‐molecular‐weight polymer.
Synthesis and electrical conductivity of poly(1,4‐phenylenevinylene‐co‐2,5‐thienylenevinylene)
Authors: Shim Hong‐Ku , Lenz Robert W. , Jin Jung‐Il
Published: April 2003

Copolymers containing either 1,4‐phenylenevinylene or 2,5‐dimethoxy‐1,4‐phenylenevinylene units combined with 2,5‐thienylenevinylene units were prepared in film form from precursor polymer films of the respective sulfonium salt polymers, which, in turn, were synthesized by the copolymerization of the respective bis(sulfonium salt) monomers. All of the copolymers could be “doped” with iodine to obtain films with high electrical conductivities and good air stability.
Electrochemical polymerization of some dihydrobenzodipyrroles
Authors: Zotti Gianni , Schiavon Gilberto , Berlin Anna , Ferraccioli Raffaella , Pagani Giorgio , Sannicolo Franco
Published: April 2003

Anodic coupling of the dihydrobenzodipyrrole isomers 1H,8H‐pyrrolo[3,2‐g]indole (1), 1H,7H‐pyrrolo[3,2‐f]indole (2), and 1H,5H‐pyrrolo[2,3‐f]indole (3) in 0,1 M tetraethylammonium perchlorate in acetonitrile produces polymeric films which are reversibly oxidized around 0,3 V vs. Ag/Ag+ with 0,5 electrons per monomeric unit. IR reflectance, UV‐vis and cyclic voltammetry show that the oxidized polymers undergo easy overoxidation at the benzene ring without affecting the charge storage ability. Conductivities (0,2–5 Ω−1 · cm−1) are higher than those presented by chemically prepared samples (10−4 – 10−1 Ω−1 · cm−1) and are attributed to more ordered structures of the polymers.
Inertie photochimique du poly(fluorure de vinylidène) à courte et à grandes longueurs d'onde
Authors: Philippart Jean‐Louis , Siampiringue Narcisse , Strassel Albert , Lemaire Jacques
Published: April 2003

The photooxidizability of poly(vinylidene fluoride) films has been examined at the short wavelength (λ = 254 nm) at 30°C and at long wavelengths (λ > 300 nm) at 60°C. No oxidized groups can be observed in the infrared and ultraviolet spectra of films exposed for long periods of time. Variations of mechanical properties and of permeabilities for CO2 or O2 can only be observed after very long exposures. Introduction of photoactive pigments such as ZnO or TiO2 does not induce any photocatalyzed oxidation in prolonged exposures.
Thermodynamic stability of mixtures containing statistical copolymers, 1. Phantom‐lattice treatment of chemically modified polymers
Authors: Koningsveld Ronald , Macknight William J.
Published: April 2003

For two statistical copolymers containing the same repeating units to be miscible their chemical compositions should not differ by more than a maximum tolerable composition difference. Measurements of the miscibility behaviour of mixtures of brominated polystyrenes by Kambour et al. can be interpreted if the small changes in molecular volume caused by bromination are taken into account with a simple extension of Scott's model. The feature is in accordance with the well‐known sensitivity of polymer blend miscibility to small changes in chain length. The relatively small extension of the model already changes the value of the pairinteraction parameter (χ) drastically, which exemplifies the necessity to let χ values in literature be accompanied by precise information about the model used in the evaluation.
Thermal degradation of anionically prepared poly(methyl methacrylate)s
Authors: Chiantore Oscar , Guaita Marino , Rendina Gabriele
Published: April 2003

Thermal degradations of samples of poly(methyl methacrylate), prepared with different anionic initiators, were compared. It could be shown that the polymers prepared with 1,1‐diphenylhexyllithium and with the tetramer of α‐methylstyrene degrade in one step at temperatures higher than 300°C, whereas those prepared with cumylcesium exhibit two degradation steps, one at temperatures lower and one at temperatures higher than 300°C. By means of end group analysis and molecular weight determinations it could be concluded that the low temperature degradation step of poly(methyl methacrylate), prepared with cumylcesium, involves initiation at the polymer chain ends.
Azo polymers — syntheses and reactions, 2. Selfcrosslinking, swelling and DSC experiments
Authors: Nuyken Oskar , Weidner Richard , Schuster Robert H.
Published: April 2003

Polymers containing azo groups and CC‐double bonds were crosslinked by heating to the temperature at which cleavage of the azo functions covalently linked to the polymer backbone takes place. The crosslinking process was characterized by swelling experiments and by DSC. From the reaction enthalpy the number of polymer chains initiated by one radical was estimated. Swelling experiments and DSC showed that the crosslinking efficiency of the radicals increases with the temperature at which the azo groups are split off and with the instability of the radicals. Polymers containing also functions with different thermostability were used for selective stepwise network formation.
Copolymerization of cycloalkenes with ethylene in presence of chiral zirconocene catalysts
Authors: Kaminsky Walter , Spiehl Regina
Published: April 2003

The chiral catalyst ethylene(bisindenyl)zirconiumdichloride/methylaluminoxane, which is soluble in hydrocarbons, allows the polymerization of cyclic alkenes, e. g. cyclopentene, to form isotactic polymers. No ring opening reaction occurs. To reduce the high melting point of the polycyclopentene, copolymers with ethylene were synthesized. The copolymerization of cyclopentene with ethylene shows similar reaction rates as found for the homopolymerization of ethylene. From 13C NMR spectroscopically calculated rates of incorporation of cyclopentene or cycloheptene in the polymers the copolymerization parameters can be deduced. With increasing polymerization temperature from −10 to 20°C the r1 values rise significantly from 80 to 300. Up to 10 mol‐percnt; of cyclopentene monomeric units in the polymer the comonomer is incorporated statistically, whereas a higher content of comonomer leads to two‐block formation.
Analysis of mutual exclusions in multichain athermal systems
Authors: Cifra Peter , Romanov Andrej
Published: April 2003

The concentration‐dependent decrease of the entropy of polymer chains in polymer solutions is treated by Monte Carlo simulation technique and by blob analysis. The results suggest the existence of a universal relation for this dependence over a broad concentration range. Differences between the observed combinatorial entropy of the multichain system and the behaviour proposed by mean‐field treatments as well as implications for treatments of the melting entropy of a polymer are pointed out.
Interpretation of the effects of segmental friction on the diffusion coefficients of polymer chains
Authors: Stepto Robert F. T.
Published: April 2003

Previously established variations with chain length and solvent of the segmental friction coefficient (ζ) of poly(methylene) chains in dilute solution are rediscussed and reanalysed as effects due to chain dynamics. The assumption of a solvent continuum, common to all theories of the diffusion coefficient (D), is seen to be a gross but presently unavoidable oversimplification. Given this situation, Kirkwood‐Riseman (K‐R) (rigid‐body) hydrodynamics are shown to provide a satisfactory basis for correlating changes in ζ. (The use of full Oseen hydrodynamics brings only a minor improvement). Basically, because the differences between segmental and centre‐of‐mass velocities increase with chain length then ζ also increases, bringing relative reductions in values of D compared with those calculated on the basis of constant ζ. In addition, values of ζ are smaller in solvents of larger molar volume and/or viscosity, consistent with more slippage between segment and solvent. In the limit of infinite chain length, the ratio, ψ(∞), of equilibrium radius and Stokes‐Einstein diffusion radius, rD, is shown to be reduced significantly below the value of 1,505 predicted by K‐R hydrodynamics for the freely‐jointed chain in a continuum. The reduction in ψ(∞), essentially an increase in rD, is due to less penetration of the molecular domain by the solvent in real systems. Larger values of rD, because of less penetration, appear to occur with solvents of higher molar volume and/or viscosity (e.g. quinoline, cf. benzene), although the values of ζ in such solvents are smaller.
Kinetics of reaction of living polymers with linking agents resulting in ring closure
Authors: Szwarc Michael
Published: April 2003

Reaction of a living polymer endowed with two reactive end‐groups with a bifunctional linking agent results in ring closure as well as in chain extension. These competing reactions are described by a kinetic scheme involving dimensionless rate constants which gives the fractions of the initial reagents converted into products as functions of a dimensionless “time”. The treatment leads to 9 coupled differential equations solved numerically. The results are discussed and the approximation involved in this treatment was shown to be reliable.
Melt elongation of a commercial poly(methyl methacrylate) product and a commercial polystyrene
Authors: Linster Jean‐Jacques , Meissner Joachim
Published: April 2003

Melts of a commercial poly(methyl methacrylate) product and a commercial polystyrene were elongated homogeneously up to Hencky strains of ε > 4 by means of the rotary clamp technique. For this purpose, certain modifications to the rheometer were necessary which are described in detail. Both polymer melts show strain hardening, i. e. the elongational viscosities are higher than the threefold of the linear viscoelastic limiting viscosity measured in shear. The degree of hardening is very different: For the poly(methyl methacrylate) product the hardening is only small, and so are the recoverable portions of the total strains, whereas for the polystyrene the opposite is true. This different behaviour is connected with a difference of the linear viscoelastic relaxation spectra at long relaxation times. The test results can be described efficiently by the Lodge‐Wagner rubberlike liquid constitutive equation.
Polymers from multifunctional isocyanates, 3. Synthesis and polyaddition reactions of (liquid‐crystalline) fully aromatic diisocyanatoesters
Authors: Mormann Werner , Brahm Martin
Published: April 2003

The regioselective reaction of aliphatic ω‐isocyanatoacyl chlorides with silyl‐protected hydroxy‐nucleophiles was extended to aromatic isocyanatoacyl chlorides. Starting with 3‐ or 4‐isocyanatobenzoyl chloride and 3‐ or 4‐trimethylsiloxyphenyl isocyanate, the four isomeric isocyanatobenzoic acid isocyanatophenyl esters were synthesized in high yields. From terephthaloyl chloride and two moles of a siloxyphenyl isocyanate or from 1,4‐bis(trimethylsiloxybenzene) and two moles of an isocyanatobenzoyl chloride, diesterdiisocyanates were obtained containing 3 benzene rings. The para‐substituted diisocyanates show liquid‐crystalline behaviour. Polyaddition reaction with various diols led to poly(esterurethane)s with a regular sequence of urethane and ester groups. The poly(urethane)s from the para‐substituted diisocyanates have very high melting points (225–350°C). Liquid crystallinity could not be proven unambiguously due to the instability of the urethane linkage at these temperatures.
Préparation de microlatex acryliques par polymérisation photochimique de solutions micellaires et de microémulsions
Authors: Schauber Claude , Riess Gérard
Published: April 2003

Microlatices of acrylic monomers, in the particle size range of 10–30 nm, were prepared by photopolymerization of micellar systems (monomer‐surfactant) and of microemulsions based on monomer‐surfactant‐cosurfactant. Formation of monomer containing microemulsions is shown for various surfactants in combination with alcohols as cosurfactants and the corresponding phase diagrams are given. Photopolymerization, in the presence of oil‐soluble initiators, was investigated for such systems based on cyclohexyl methacrylate (CHMA) and on tetramethylene dimethacrylate (BDMA). Crosslinked and non‐crosslinked colloidal polymer particles could be obtained, with a 5–10% solid content of polymer. The variation of particle size, and the molecular weight for non‐crosslinked systems, was studies as a function of initiator concentration, and monomer/surfactant ratio. The smallest particles (10–15 nm) are obtained for the system BDMA/lauryl sulfate (LS).
Partitioned polymerization, 2. Simultaneous transfer of monomer and of initiator
Authors: Bartoň Jaroslav , Juraničová Viera
Published: April 2003

The kinetics of the 2,2′‐azoisobutyronitrile (AIBN)‐initiated emulsion polymerization of methyl methacrylate and butyl methacrylate was studied in the presence or in the absence of 4‐stearoyloxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl radical (STMPO) situated in the oil (monomer) phase. The polymerization was initiated and oligomeric radicals were formed in the aqueous phase to which methyl methacrylate (butyl methacrylate) and AIBN were transferred. Polymerization does not take place in the oil phase because of the inhibitor present. Relatively short inhibition periods of polymerization observed in systems containing STMPO confirm that a small part of STMPO was transferred from the oil to the water phase. The length of the inhibition period in the emulsion polymerization is determined by a competition between the addition reaction of primary radicals with monomer and the termination reaction of primary radicals with STMPO as well as by the rate of STMPO scavenging by oligomer‐monomer and polymer‐monomer particles. The polymerization system studied belongs to a group of partitioned polymerization systems characterized by simultaneous transfer of monomer and initiator from the oil to the water phase, where the initiation of polymerization takes place.
Synthesis and properties of poly(L‐glutamic acid)s containing covalently bound 4‐hydroxyphenylporphyrin moieties
Authors: Hanabusa Kenji , Sogabe Seiji , Koyama Toshiki , Shirai Hirofusa , Hayakawa Tadao , Hojo Nobumasa , Kurose Akio
Published: April 2003

Poly(L‐glutamic acid)s with various contents of 4‐[10,15,20‐tris(4‐hydroxyphenyl)‐5‐porphyrinyl]phenoxy groups (polymers 3a–e) prepared by reaction of poly(L‐glutamic acid) (1) and 5,10,15,20‐tetrakis(4‐hydroxyphenyl)porphyrin (2) in the presence of dicyclohexylcarbodiimide. The structures of 3a–e in ethanol were studied by CD spectroscopy and it was found that the introduction of large amounts of porphyrin moieties into 3 tends to prevent the α‐helix formation. The IR dichroic ratios of films of 3a–e, obtained by rubbing the concentrated ethanol solution on an NaCl plate with a spatula into a constant direction, gave informations about the orientation of the α‐helix rod. X‐ray diffraction photographs suggest that the crystalline packing of the α‐helix is more disordered with increasing content of porphyrin moieties in 3. Polarizing microscopy indicates that 3a–d form lyotropic liquid crystals in concentrated DMF solution.
Characterization of ethylene‐propene copolymers prepared with heterogeneous titanium‐based catalysts
Authors: Kakugo Masahiro , Naito Yukio , Mizunuma Kooji , Miyatake Tatsuya
Published: April 2003

Ethylene‐propene (EP) copolymers prepared with various heterogeneous titanium‐based Ziegler‐Natta catalysts, i. e., δ‐TiCl3, β‐TiCl3, and MgCl2‐supported titanium catalysts were fractionated by successive solvent extraction. Wide composition distributions were observed for all samples. Composition distributions of some samples were investigated precisely by temperature‐programmed elution column fractionation. The fractionation data showed that these copolymers are a mixture of polyethylene and of copolymers with different structures, i. e., random and block copolymers. In every sample random copolymers were found most abundantly, the propylene sequences being present only as mmmm pentads. These data suggest that random copolymer is formed on an isospecific site.
Infrared spectroscopic investigation of solution‐crystallized trans‐1,4‐polybutadiene copolymers
Authors: Wang Pei‐guo , Woodward Arthur E.
Published: April 2003

Fourier transform infrared spectra were obtained for solution‐crystallized samples of two polybutadiene copolymers, one containing 10% cis‐, 1,5% 1,2‐ and 88,5% trans‐ and the other 1% cis‐ and 99% trans‐polybutadiene. Measurements were made at room temperature, at temperatures above the crystal transition temperature, but below the melting temperature, and at temperatures above the melting temperature. Spectra for 100% crystalline samples were obtained by subtraction of the spectrum for the melt from that for the semicrystalline sample. Infrared spectra were also obtained for suspension epoxidized samples; these showed the presence of an unreacted crystal core and completely reacted lamellar surfaces.
Effect of dilution during network formation on the sol fraction and elasticity of polyurethane networks
Authors: Ilavský Michal , Bouchal Karel , Dušek Karel
Published: April 2003

The effect of dilution at network formation (polymer volume fraction v(0) = 1 − 0,4) on the fraction and equilibrium photoelastic behaviour of polyurethane networks was investigated. The networks were prepared from poly(oxypropylene)triol and 4,4′‐methylenedi(phenyl isocyanate) with various mole ratios of reactive groups 1 ≤ rH = [OH]/[NCO] ≤ 1,5. From a comparison between the experiments and the theory of branching processes we find that: (a) with both increasing ratio rH and increasing dilution the fraction of bonds lost in elastically inactive cycles increases from 0,02 to 0,06; (b) the experimental reduced equilibrium moduli Gr of the predominant majority of samples are higher than those theoretically predicted by the Flory junction‐fluctuation theory for the front factor A = 1. Also the decrease of Gr with dilution (expressed as volume fraction of diluent during network formation v(0)) is very steep, thus supporting the contribution of permanent interchain constraints to the overall Gr value.
Chitosan gels, 3. The formation of gels by reaction of chitosan with glutaraldehyde
Authors: Roberts George A. F. , Taylor Kathryn E.
Published: April 2003

The effects of several variables on the gelation behaviour of the chitosan/glutaraldehyde system have been studied. The rate of gelation is increased by increase in concentration of either chitosan or glutaraldehyde, or by an increase in temperature, and reduced by an increase in the concentration of acetic acid. Addition of a number of neutral electrolytes also causes an increase in the rate of gelation, the increase being larger the greater the activity coefficient of the electrolyte. UV/visible and NMR spectra of glutaraldehyde, acetaldehyde and crotonaldehyde, together with those of their 2,4‐dinitrophenylhydrazine derivatives, indicate that only a very small proportion (<0,15%) of the aldehyde groups have undergone an aldol condensation reaction leading to α,β‐unsaturated aldehyde groups. This, together with other evidence, suggests that the cross‐linking mechanism involves formation of Schiff's base structures rather than Michael‐type adducts as previously postulated.
Hydrogen peroxide generation from reduced polymer nitroxyls and oxygen
Authors: Seidemann Rolf , Dulog Lothar
Published: April 2003

For producing hydrogen peroxide the suitability of stable polymeric nitroxyls as reaction carriers was investigated. These can be hydrogenated to the corresponding hydroxylamines, which are oxidized by oxygen exclusively to hydrogen peroxide and nitroxyls. The yield of hydrogen peroxide was determined in different solvents, at different reaction times and temperatures. Possible side reactions for the decomposition of hydrogen peroxide were investigated. The activation energy for the oxidation of polymeric hydroxylamine with oxygen in DMSO was calculated to be 67 kJ/mol.
Thermodynamics of ternary mixtures of random copolymers
Authors: Dafniotis Petros , Karayianni Eleni , Panayiotou Constantinos
Published: April 2003

A most general formalism based on the Lattice‐Fluid theory of polymer solutions is presented for multicomponent mixtures of random copolymers which may consist of any number of different types of monomers. Particular emphasis is given to the phase stability in these mixtures. Equations for the spinodals and the critical points are presented. The formalism is subsequently applied to a number of interesting cases of ternary (co)polymer mixtures such as: mixtures of three random copolymers with the same monomers A and B but in different proportions (A B + A B + A B) mixtures of homopolymers Am and Bn with the random copolymer Ai Bj, and mixtures of the random copolymers (A B + A B + A C). The effect of temperature on the phase behavior of these systems is discussed. The agreement of theoretical predictions with available experimental information is satisfactory. Because of its simplicity, the model may be used as a tool for studying multicomponent mixtures exhibiting lower or upper critical solution temperature behavior.
Characterization of isotactic polypropylene obtained with ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dichloride as catalyst
Authors: Tsutsui Toshiyuki , Mizuno Akira , Kashiwa Norio
Published: April 2003

Polypropylene (PP) prepared with ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dichloride in conjunction with methylaluminoxane yields 58 wt.‐% of material insoluble in boiling heptane (C7). The C7‐soluble and the C7‐insoluble fraction exhibit high isotacticity, viz. 97,2% and 98,2%, respectively, relatively narrow molecular weight distribution (weight‐ to number‐average molecular weight M̄w/M̄n = 2,19 for the whole polymer), a small amount of regioirregular units arranged with meso‐placements and relatively low melting points, i.e., 151,3°C for the C7‐soluble and 153,2°C for the C7‐insoluble fraction in spite of high isotacticity.
Emulsion polymerization of styrene using phospholipid as emulsifier. Immobilization of phospholipids on the latex surface
Authors: Yamaguchi Kazuo , Watanabe Shinji , Nakahama Seiichi
Published: April 2003

Emulsion polymerization of styrene using polymerizable and non‐polymerizable phospholipids with double alkyl chains (1a, 1b), and their single‐chain analogues (2a, 2b) as emulsifier gave polymer latices with narrow size distribution. The resulting latices, which were subjected to acid and enzymatic hydrolysis, and reprecipitation with methanol, were characterized by phosphorus analysis and X‐ray photoelectron spectroscopy (XPS). The phospholipids remained mainly on the surface of the latices. The non‐polymerizable emulsifiers were physically adsorbed on the latices, but the polymerizable emulsifiers were chemically bound to the latices. Phospholipid 1b on the latex prepared with a lipophilic radical initiator was hydrolyzed by phospholipase C.
Oligomerization of oxetane and synthesis of polyterephthalates derived from 1,3‐propanediol and 3,3′‐oxydipropanol
Authors: González César Carlos , Bello Antonio , Pereña José Manuel
Published: April 2003

The oligomerization of oxetane (trimethylene oxide) initiated by sulfuric acid in methylene chloride in the presence of 1,3‐propanediol (trimethylene glycol) leads to the formation of α‐hydro‐ω‐hydroxyoligo(oxytrimethylene)s. The effect of adding different amounts of trimethylene glycol was studied, and the dimer, 3,3′‐oxydipropanol, could be isolated. Polymers from dimethyl terephthalate and 3,3′‐oxydipropanol and copolymers from 1,3‐propanediol, 3,3′‐oxydipropanol and dimethyl terephthalate were synthesized. The influence of the chemical structure on their thermal transitions was analyzed.
A chemical modification of a grafted synthetic polymer under cellulose hydrolysis conditions
Authors: Casinos Ismael , Fernández María Jesús , Guzmán Gonzalo Martín
Published: April 2003

The current cellulose hydrolysis methods were applied to cellulose‐graft‐poly(vinyl acetate‐co‐methyl acrylate) giving rise to a residual solid that showed IR absorptions at 3 600 – 3 000 and 1775 cm−1 and partial insolubility in the solvents of poly(vinyl acetate‐co‐methyl acrylate). Some model experiments showed that hydrolysis of the acetoxy and methoxycarbonyl groups takes place and subsequent γ‐lactonization and crosslinking in the grafted synthetic polymer, parallel to the cellulose hydrolysis. It became evident that the competition between lactonization and crosslinking and their extent are controlled by the sequence‐length distributions of the monomeric units in the copolymer and by the conversion in the hydrolysis reaction, respectively. Both esterification reactions were eliminated when the experiment was performed at sufficiently low temperature.
Polymerization of bicyclic acetals, 18. Propagation processes in the cationic ring‐opening polymerization of 6,8‐dioxabicyclo[3.2.1]octane derivatives having a 3(e)‐benzyloxy group as a common substituent
Authors: Okada Masahiko , Hirasawa Takahito , Sumitomo Hiroshi
Published: April 2003

Polymerizations of two bicyclic acetals, rac‐2(a), 3(e)‐bis(benzyloxy)‐6,8‐dioxabicyclo‐[3.2.1]octane (1d) and the D‐enantiomer of 2(a),3(e),4(a)‐tris(benzyloxy)‐6,8‐dioxabicyclo[3.2.1]octane (1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐allopyranose) (1e) were investigated in dichloromethane as solvent at different temperatures ranging from −90 to −30°C. The polymerization of 1d gave polyacetals containing both the trans‐ and cis‐2,6‐linked tetrahydropyran units (2d and 3d) over the entire temperature range. The proportion of 3d increased up to 73% with decreasing initial monomer concentration at higher polymerization temperature. On the other hand, the polymerization of 1e gave rise to polymers exclusively or predominantly composed of trans units (2e), the content of cis units (3e) being at most 25%. On the basis of these results, along with the previous experimental results on the polymerizations of three other relevant bicyclic acetals (1a – c), the marked substituent effect as well as the influence of polymerization temperature and initial monomer concentration on the stereochemical course of the polymerization are discussed in terms of a propagation mechanism involving an oxonium exchange reaction at the penultimate unit of a growing chain.
Transient effects in diffusion‐controlled polymer cyclization
Authors: Xu Huelin , Martinho José M. G. , Winnik Mitchell A. , Beinert Gérard
Published: April 2003

Fluorescence decay measurements were carried out to study the kinetics of intramolecular exciplex formation in two low‐molecular‐weight samples of polystyrene (1) with narrow molecular weight distribution capped on one end with a pyrene moiety and on the other with an N,N‐di‐methylaminophenyl group. Monomer and excimer decay profiles, IM(t) and IE(t), resp., were inconsistent with the predictions of the simple two‐state (Birks) model, but could be well‐fitted by assuming that the diffusion‐controlled rate coefficient for exciplex formation, k1(t), is time dependent. Using a Smoluchowski formulation for this rate coefficient k1(t) = a(1 + bt−1/2), we could use the a and b parameters to calculate values for the chain‐end diffusion coefficient characterizing the reaction for samples of the polymers in cyclopentane and cyclohexane solutions.
Preparation and crystalline structure of random copolymers of glycine and β‐alanine
Authors: Puiggalí Jordi , Muñoz‐Guerra Sebastián
Published: April 2003

Copolymers of glycine and β‐alanine within a range of amount‐of‐substance compositions from 3:1 to 1:9 were prepared by polycondensation of mixtures of the respective pentachlorophenyl ester hydrobromides. Number‐average molecular weights between 2 500 and 9 000 were obtained, the lower values corresponding to those copolymers with a higher content in glycine. Sequence distributions were evaluated by means of 50,3 MHz 13C NMR spectroscopy and the crystalline structure was examined by wide‐angle X‐ray diffraction. Random copolymers having similar contents in glycine and β‐alanine were found to crystallize in a bidimensional hexagonal lattice (a = 4,79 Å) with chains packed in a similar manner as they do in the crystalline structure of polyglycine II. On the contrary, a heterogeneous product consisting of homopolymer and random copolymer fractions results from mixtures which are enriched in one of the two amino acids. The random copolymer poly(glycine‐ran‐β‐alanine) adopts a packing scheme similar to that found for the helical form of the alternating copolymer nylon 2/3. Chains are hexagonally arranged and interlinked by a three‐dimensional network of hydrogen bonds as described for the well known model of polyglycine II, although in the present case no order along the chain axis should be expected.
Low temperature modification of polymers by triazolinediones. Electrophilic substitution of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene)
Authors: Stadler Reimund , de Araujo Macro A. , Kuhrau Martin , Rösch Joachim
Published: April 2003

Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (PPE, 8) is reacted with substituted 1,2,4‐triazoline‐3,5‐diones 1 to give the partially substituted poly[oxy‐2,6‐dimethyl‐3‐(1,2,4‐triazoline‐3,5‐dione‐1‐yl)‐1,4‐phenylene]9. The reaction occurs via electrophilic substitution of the electron‐rich PPE with the highly electron deficient triazolinediones 1. For low degrees of substitution, the reaction readily occurs at room temperature. The inherent viscosity decreases with increasing substitution. The results are compared to similarly substituted polybutadiene. The glass transition temperature of the substituted PPE's decreases with the content of triazoline groups, a result which is interpreted by a distortion of the packing in glassy PPE.
Determination of the number of active centers in Ziegler‐Natta polymerization of propene using sulfur‐containing terminating agents, 1. Application of carbon disulfide
Authors: Vozka Pavel , Mejzlík Jiří
Published: April 2003

Polymerization of propene catalyzed with TiCl3 · 1/3(AlCl3)/AlEt2Cl or TiCl3 · 1/3(AlCl3)/AlEt3 systems in heptane at 323,2 K in the presence of CS2 was studied. It was demonstrated that the sharp decrease of rate, observed upon addition of CS2, is not due to a decrease of the organometal concentration, although some consumption of the organometal was evidenced by means of IR measurement. Tagging of the growing chains was monitored by determination of the sulfur content in the polymer. Side reactions of CS2, leading to a blank content of sulfur in polypropylene, were observed in the presence of catalytical components even after their deactivation. Thus, a thorough washing of the polymer was necessary. A substantial increase of heptane solubles observed upon addition of larger amounts of CS2 was found to be due to a much lower molecular weight of the polymer, while stereospecificity of the catalytical system was virtually preserved. It was concluded that CS2 behaves as a suitable terminating and tagging agent.
Synthesis of poly(α‐malic acid) and its hydrolysis behavior in vitro
Authors: Ouchi Tatsuro , Fujino Atsushi
Published: April 2003

Biodegradable poly(α‐malic acid) (7) was synthesized by means of ring‐opening homopolymerization of malide dibenzyl ester (5), which is a cyclic dimer of β‐benzyl malate. In order to obtain a high‐molecular‐weight biodegradable lactic acid type polyester having pendent modifiable groups, ring‐opening copolymerization of malide dibenzyl ester with L‐dilactide was applied to give poly(α‐malic acid‐co‐lactic acid) (10). It was found from the results of hydrolysis of poly(α‐malic acid) that the main‐chain ester bonds were cleaved randomly and slowly in vitro.
Thermotropic para‐linked aromatic polyesters containing 1,1′‐binaphthyl‐4,4′‐ylene units
Authors: Hohlweg Martin , Schmidt Hans‐Werner
Published: April 2003

Synthesis, thermal properties and solubility behaviour of para‐linked aromatic homopolyesters containing non‐coplanar 1,1′‐binaphthyl‐4,4′‐ylene units are described. By combining such binaphthylylene units with monosubstituted phenylene units, crystallization can be suppressed and thermotropic liquid‐crystalline polyesters with glass transition temperatures (Tg) up to 190°C are obtainable. The liquid‐crystalline order is maintained below Tg in an anisotropic glass. The polyesters show good solubility in common organic solvents, such as chloroform or tetrahydrofuran.