bluuebunny/crossref_metadata_2025 huggingface dataset:
Manipulation of the ferroelectricity in LC polymers via photomechanical isomerization of azobenzene moieties
Authors: Öge Tanja , Zentel Rudolf
Published: April 2003

We report the synthesis and characterization of a new ferroelectric liquid crystalline side chain copolymer containing photoisomerizable chromophores and non‐photoisomerizable mesogenic units. On illumination with UV‐light a suppression of the polar order is obtained as indicated by a substantial drop of the spontaneous polarization (PS) compared to the dark state. We interpret this as the phase order being disrupted by the cis‐isomer of the chromophore. After illumination with VIS‐light only the major part of Ps is restored. The photochemical cis‐trans back‐isomerization (restoration of the phase) leads to a different stationary state than the dark state of the material. The thermal reisomerization (cis‐trans) in the liquid‐crystalline phase was observed to be faster than in solution by one order of magnitude.
Ligand effects on olefin polymerizations with multinuclear zirconocene catalysts having dimethylsilylferrocene as a cyclopentadienyl substituent
Authors: Mitani Makoto , Oouchi Kunihiro , Hayakawa Michiya , Yamada Tohru , Mukaiyama Teruaki
Published: April 2003

Olefin polymerizations were conducted with novel multimetallic zirconocene catalyst systems: RCpCpZrCl2 (1) (R = dimethylsilylferrocene; Cp = cyclopentadienyl) and (RCp)2ZrCl2 (2) in combination with methylaluminoxane or tetrakis(pentafluorophenyl) borates. In ethylene polymerization, the maximum catalyst activity was observed at a lower temperature (30–45°C) when using complex 1 or 2, compared with Cp2ZrCl2. It was also revealed that complex 1 is a more effective catalyst than Cp2ZrCl2 for copolymerization of ethylene and propene.
Swelling behavior and controlled release of new hydrolyzable poly(ether urethane) gels derived from saccharide and L‐lysine derivatives and poly(ethylene glycol)
Authors: Wibullucksanakul Sirinat , Hashimoto Kazuhiko , Okada Masahiko
Published: April 2003

New hydrolyzable gels bearing saccharide, L‐lysine, and poly(oxyethylene) moieties were prepared via polyaddition of methyl ß‐D‐glucofuranosidurono‐6,3‐lactone (1) and poly(ethylene glycol) PEG, Mn = 1000 with an L‐lysine derivative, methyl (S)‐2,6‐diisocyanatohexanoate (2), using dibutyltin dilaurate and triisocyanate 3 as a catalyst and a crosslinking agent, respectively. The swelling ratio and rate of hydrolysis of these gels in phosphate buffers increased with the content of PEG. Hydrolysis of these gels was enhanced by increasing the pH of phosphate buffer solution in the range from 5.5 to 8.0, while the gel having only repeating units derived from 1 and 2 but no PEG was hardly hydrolyzed in any buffer solutions (pH 5.5, 7.0, 8.0). The release of hydrophilic 5(6)‐carboxyfluorescein (CF) from these gels in buffer solution of pH 8.0 was faster than that of hydrophobic magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS). The release of ANS from the gel was enhanced with the swelling caused by hydrolysis.
Study of the propagation centre in the anionic polymerization of (meth)acrylic monomers, 7. Study of the interaction of the living dimer with lithium tert‐butoxide in tetrahydrofuran
Authors: Kříž Jaroslav , Dybal Jiří , Janata Miroslav , Lochmann Lubomír , Vlček Petr
Published: April 2003

Using 1H, 6I i, 7Li and 13C NMR, di‐tert‐butyl 2‐lithio‐2,4,4‐trimethylglutarate (A) as a dimeric model of the living poly(tert‐butyl methacrylate) is shown to form well‐defined aggregates with lithium tert‐butoxide (B) in tetrahydrofuran. The prevailing aggregates with the composition A2B2 and AB3 are controlled mainly by the ratio A:B. The initial mixture of aggregates is formed very fast but is metastable. Using 1D and 2D spectra, 1H‐1H and 1H‐6Li nuclear Overhauser effect and relaxations of 1H, 7Li and 13C, both aggregates are shown to exist mainly in three conformational forms (b, c, d) of the A‐part which are very similar in both aggregate types. In agreement with the previously published infrared spectra, form d has the γ‐ester group of A coordinated to Li. d does not exchange with the ‘open’ forms b or c with perceptible rate on the NMR time scale. Its population is promoted by a larger content of B in the aggregate. By modified neglect of differential overlap (MNDO) quantum calculations, the aggregates A2B2 and AB3 are predicted to have a roughly cubical core (OLi)4 which is distorted in the d form where one (AB3) or two (A2B2) Li atoms are pulled out of the cube by coordination to the γ‐ester group. The stabilization of the supramolecule A2B2 or AB3 and the promoting effect of B on intramolecular coordination to the γ‐ester group in A is explained in terms of a cooperative system of polycentric bonds and electrostatic interactions.
Preparation and thermal properties of semi‐rigid homo‐ and copoly(imide‐carbonate)s based on 4,4′‐oxydiphthalimide
Authors: Sato Moriyuki , Hirata Tomohiro , Ujiie Seiji
Published: April 2003

New aromatic‐aliphatic semi‐rigid homo‐ and copoly(imide‐carbonate)s 7 containing the 4,4′‐oxydiphthalimide ring system were prepared by melt polycondensation of N,N′‐bis(6‐hydroxyhexyl)‐4,4′‐oxydiphthalimide (4) and/or 6,6′‐(4,4′‐biphenyldiyldioxy)dihexanol (5) with hexamethylene diphenyl dicarbonate in the presence of zinc acetate, and their thermal and mesomorphic properties were evaluated. The assigned structures of the monomer and the polymers were identified by Fourier‐transform infrared and 13C nuclear magnetic resonance spectroscopy and elemental analyses. Differential scanning calorimetry measurements, observation of the texture by means of a polarizing microscope equipped with a hot stage and powder X‐ray analyses at various temperatures demonstrated that only the biphenyl moiety‐rich polymers from nematic phases, but the 4,4′‐oxydiphthalimide moiety‐rich polymers exhibit no liquid‐crystalline melts. It was suggested that the mesogenic character of the 4,4′‐oxydiphthalimide ring system is low. The glass transition temperature steps decrease with the biphenyl moiety content. Thermogravimetry/differential thermal analysis (TG‐DTA) measurements indicated that the polymers are thermostable up to 300°C in air.
Preparation, characterization and properties of gradient polymer blends: discussion of poly(vinyl chloride)/poly(methyl methacrylate) blend films containing a wide compositional gradient phase
Authors: Agari Yasuyuki , Shimada Masayuki , Ueda Akira , Nagai Susumu
Published: April 2003

We prepared several types of thick ≈200 μm films of a poly(vinyl chloride)/poly‐(methyl methacrylate) (PVC/PMMA) gradient polymer blend, which contained a widely waried compositional gradient phase, using a dissolution and diffusion method. We discussed the preparation conditions by classifying those gradient blend films into 5 types based on the results of differential scanning calorimetry (DSC) measurements and found the optimum conditions for preparing the ideal gradient blend consisting of only one extremely wide compositional gradient phase. Further, the gradient structures, which were evaluated by the results of DSC measurements, were confirmed by means of Fourier transform infrared/attenuated total reflection (FTIR‐ATR). Finally, the ideal blend was found to have significantly new or improved properties (e.g. a large half‐width of temperature of the dissipation factor tan δ) which cannot be observed in any PVC, PMMA homogeneously (that is ordinarily) miscible blend or a laminate system.
Chromic phenomena in neutral polythiophene derivatives
Authors: Leclerc Mario , Fréchette Martin , Bergeron Jean‐Yves , Ranger Maxime , Lévesque Isabelle , Faïd Karim
Published: April 2003

Thermochromic phenomena in various regioregular and non‐regioregular polythiophene derivatives have been investigated both in the solid state and in solution. These studies have revealed the existence of two different types of thermochromic phenomena which are correlated to the substitution pattern of the polymers. Formation of delocalized conformational defects (twistons) has been observed in regioregular polythiophene derivatives but did not occur in non‐regioregular polythiophenes. For the latter polymers, only localized conformational defects can be created along the polymer backbone leading to a monotonic blue shift of the absorption maximum upon heating. It is suggested that all these optical features are driven by order‐disorder transitions of the side‐chains, side‐chain disordering increasing their steric hindrance and/or disrupting short‐range ordered assemblies, which then force the thiophene backbone to adopt a nonplanar conformation. It has been also found that non‐covalent interactions between alkali metal ions and regioregular ether‐substituted polythiophenes can modify the side‐chain organization and can lead to interesting ionochromic effects. It is believed that chromic phenomena can be induced via a large range of external stimuli which should lead to the development of novel affinitychromic and photochromic materials.
Metal complexation of polymeric amino ligands derived from N,N′‐methylenebis(acrylamide)‐crosslinked polyacrylamides
Authors: Jose Lissy , Pillai V. N. Rajasekharan
Published: April 2003

The N,N′‐methylenebis(acrylamide) (NNMBA)‐crosslinked polyacrylamide supported amino ligands undergo complexation with Cr(III), Mn(II), Fe(III), Pb(II) and Cd(II) ions. Complexation is maximum for Cr(III) ion. The metal intake decreases as the crosslinking increases. The NNMBA resin can be reused after complexation and desorption without appreciable reduction in amino capacity. The IR spectrum of the Cr(III) complex gives an additional peak for sulfate complexation and the amino peak undergoes a negative shift, which is a clear evidence of metal coordination through the amino nitrogen. EPR, electronic spectra and magnetic moment are indicative of a distorted geometry for Cu(II), Cr(III), Fe(III) and Mn(II) complexes. Cd(II), Pb(II) complexes are diamagnetic. Complexation brings about vivid changes in the surface morphology of polymeric ligand. The thermal stability of Cr(III) complex increases as the metal content increases.
Polyethylene graft copolymers with a liquid crystalline component in the side chains
Authors: Pinto Mauricio R. , Gomes Ailton S. , Soares Bluma G.
Published: April 2003

An ethylene‐vinyl acetate copolymer (EVA) was chemically modified by the introduction of pendent thiol groups (EVA‐SH) suitable for chain transfer. The resulting copolymer was grafted with 4‐phenylazophenyl 4‐(4‐acryloyloxybutoxy)benzoate, a liquid crystalline monomer (LCM), initiated by AIBN. Grafting was performed at LCM/EVA‐SH mass ratios of 10, 5, 2 and 1 in the feed. The grafting degree, i.e., the fraction of LC polymer in the graft copolymer, ranged from ca. 5–30 wt.‐%. The thermal transitions were investigated by DSC, pointing at marked microphase separation between LC and polyethylene moieties. The anisotropic properties of the graft copolymers were confirmed by cross‐polarized light microscopy. All the samples showed birefringence at 140°C, some only on shearing however.
Characterization of polystyrene‐block‐poly(4‐vinyl‐pyridine) block copolymer micelles in toluene solution
Authors: Calderara Frédéric , Riess Gérard
Published: April 2003

Polystyrene‐block‐poly(4‐vinylpyridine) diblock copolymer micelles of various compositions and molecular weights were characterized in toluene. Static light scattering, quasielastic light scattering and viscosity measurements were used to determine the basic micellar characteristics (aggregation number, micellar size, geometry and polydispersity). Depending on the copolymer under investigation, two different geometries (spherical and non‐spherical geometry) were observed. The micelles which are spherical in shape have aggregation numbers in the range 200–600 while the non‐spherical micelles have a much larger aggregation number (ranging between 600–1000). The sizes of the micelles remain unchanged in our concentration range (10−3 − 5 middot; 10−3 g/mL) and no critical micelle concentration could be detected in the concentration range from 10−5 to 10−3 g/mL. A detailed analysis of the structural parameters of the micelles which are spherical in shape, reveals that the core‐shell interfacial area per copolymer chain as well as the volume fraction of the copolymer in the shell are relatively constant, and that the core is almost not swollen by the solvent. Mixed uniform micelles were observed after mixing equal amounts of two solutions containing micelles differing in size and molecular weight. The reequilibration rate was found to be very fast.
Thermoreversible gel formation in poly(ethylene terephthalate)/epoxy resin solutions
Authors: Ji Gending , Xue Gi , Zhang Xining , Liu Bo , Zhou Dongshan , Gu Xinhong
Published: April 2003

The thermoreversible gelation of solutions of poly(ethylene terephthalate) (PET) in liquid diglycidyl ether of bisphenol‐A epoxy resin has been investigated. The critical polymer concentration for gel formation is 10 wt.‐%. The solutions were found to solidify rapidly into gels on cooling. Polarized light microscopy (PLM) and small‐angle light scattering (SALS) studies showed that these gels contain many large, regular PET spherulites. The gels in this system may be formed according to two consecutive processes: first the liquid‐liquid phase separation, and second the crystallization of PET in polymer‐rich domains. Hence, gelation occurs by formation of a three‐dimensional PET network in the epoxy solvent, where the nodes of the network are PET spherulites.
Synthesis and properties of thermotropic polyesters modified with a non‐mesogenic rigid group
Authors: Tseng Han‐Thing , Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing
Published: April 2003

Four series of copolyesters, namely BB6‐DMT, BB5‐DMT, BB6‐DMI and BB5‐DMI series, were prepared by melt polycondensation of dimethyl 4,4′‐bibenzoate (BB) with a dimethyl phthalate (DMT: dimethyl terephthalate or DMI: dimethyl isophthalate) and an alkanediol (1,6‐hexanediol or 1,5‐pentanediol). The homopolyesters poly(hexamethylene 4,4′‐bibenzoate) (BB6) and poly(pentamethylene 4,4′‐bibenzoate) (BB5) exhibit a smectic phase. The thermotropic liquid crystalline and crystalline properties of the copolyesters are significantly influenced by the presence of the non‐mesogenic rigid phthalate unit. All BB6‐DMT copolyesters remain crystalline. As x, the molar fraction of the phthalate units in the diacid units, ≧ 0.7 the mesophase of the BB6‐DMT copolyesters is destroyed completely. For BB5‐DMT copolyesters, the mesophase disappears as x ≧ 0.4, and the copolyesters become amorphous as 0.5 ≦ x ≦ 0.8. The mesophase and the crystallinity of the BB6‐DMI copolyesters are destroyed completely as x > 0.5. The BB5‐DMI copolyesters lose the mesophase as x ≧ 0.3, and become amorphous as x ≧ 0.4. The results indicate that the non‐linear isophthalate unit destroys mesophase and crystallinity of the copolyesters to a greater extent than the para‐linked terephthalate unit.
Insoluble polyelectrolyte complex formed from chitosan and α‐keratose: conformational change of α‐keratose
Authors: Park Won Ho , Lee Kuen Yong , Ha Wan Shik
Published: April 2003

The conformational change of α‐keratose in the polyelectrolyte complex (PEC) formation with chitosan was investigated by means of differential scanning calorimetry and infrared spectroscopy. The change of the secondary structure of α‐keratose in the reaction mixture was estimated quantitatively with circular dichroic spectra by the curve fitting method. The α‐helix structure of 30% and above of α‐keratose was found to be destructed and transformed into random structures at a mixing ratio of maximum PEC formation.
Interfacial agents for polymer/liquid crystal dispersions
Authors: Gohy Jean‐François , Jérôme Robert
Published: April 2003

Liquid crystals (LC) were covalently and ionically bonded to one (or both) end(s) of polystyrene chains. These compounds were tested as interfacial agents in polystyrene/liquid crystal dispersions. In case of covalent bonding, the additive is too much “soluble” in polystyrene and no interfacial activity is observed. Ionic bonding of the LC to polystyrene chains deeply changes the situation, all the other conditions being the same. The dipolar interactions of the ion pairs are clearly favorable to the localization of the additive at the polymer/LC interface. The higher polarity of the ammonium sulfonate pairs compared to the parent ammonium carboxylate ion pairs accordingly accounts for a higher interfacial activity.
Ring‐opening polymerization of cyclobutane adducts of tetracyanoethylene and vinyl ethers with quaternary ammonium halides
Authors: Yokozawa Tsutomu , Mori Takanori , Hida Kimitada
Published: April 2003

Ring‐opening polymerizations of cyclobutane adducts of tetracyanoethylene (TCNE) and vinyl ethers (VE) with quaternary ammonium halides are described. The polymerization of the cyclobutane adduct 5a of TCNE and ethyl vinyl ether (EVE) was carried out with 10 mol‐% of tetrabutylammonium iodide (TBAI) in N,N‐dimethylacetamide (DMAc) at ambient temperature to afford the alternating copolymer of TCNE and EVE with high molecular weight in good yield without contamination by TBAI. Under the optimum conditions, the cyclobutane adducts of TCNE and a variety of VEs such as butyl vinyl ether, isobutyl vinyl ether, 2,3‐dihydrofuran, and 3,4‐dihydro‐2H‐pyran were polymerized to yield similar polymers. On the basis of the fact that the polymer molecular weight increased rapidly at the initial stage and slowly even after the consumption of all monomers, we propose that the iodide ion of TBAI initiates the anionic chain polymerization of the cyclobutane adduct to afford an iodide‐substituted macroanion 6, which is subjected to intermolecular nucleophilic substitution with each other in a step reaction manner. This intermolecular reaction of 6 was further confirmed by a model reaction of cyclobutane with chloromethyl methyl ether in the presence of chloride ion.
Determination of copolymerization parameters of methyl methacrylate with dodecyl methacrylate by means of FTIR spectroscopy
Authors: Kleinová Angela , Borsig Eberhard , Schulze Ulrich , Pionteck Jürgen
Published: April 2003

The bulk copolymerization of methyl methacrylate (MMA) with dodecyl methacrylate (DMA) initiated by 2,2′‐azoisobutyronitrile (AIBN) at 60°C was used to prepare samples with different MMA/DMA ratios. The composition of the copolymers was determined by means of FTIR spectroscopy, using the absorption intensity ratio of CH2/CO for copolymers in CDCl3 solution and as KBr tablets. Reactivity ratios, determined by the Kelen‐Tüdős method, were found to be: rMMA = 1.58 and rDMA = 1.88 for copolymers analyzed in solution, and rMMA = 1.67 and rDMA = 1.95 for samples prepared as KBr tablets. Comparison of copolymer composition of some samples was made with elemental analysis data. It was found that the shift in the CO maximum observed for the copolymer in CDCI3 solution, compared to the corresponding homopolymer solutions, could also be used for determining copolymer composition.
Kerr effect in a laterally substituted side‐chain liquid‐crystalline polymer
Authors: Merekalov Alexei S. , Finkelmann Heino
Published: April 2003

The static and dynamic Kerr effects in a liquid‐crystalline (LC) side‐end polymer with a laterally substituted mesogenic fragment are studied. The characteristic relaxation times of the two different relaxation processes observed diverge at the same temperature. The main feature of the dynamic behavior of the polymer, e.g., the type of the electro‐optical response is similar to that of side‐on LC polymers.
Modification of poly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] film surfaces in an oxygen low pressure plasma
Authors: Mas André , Jaaba Hassan , Schué François , Bellu Anna Maria , Kassis Camille , Linton Richard , Desimone Joseph Mark
Published: April 2003

Poly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] (91:9 mass‐%) (P(HB‐co‐9% HV)) film surfaces were modified by an oxygen plasma treatment (75 W, 50 Pa, 5 min). The number of oxygen atoms increases about 12–13% and the polar component of the surface energy increases from 6.3 to 21 mN · m−1. However, the wettability is stable only after 60 days. Untreated and treated film surfaces are studied by means of X‐ray photoelectron spectroscopy with two different depth analyses. With storage time, the oxygen contents of the modified film is constant at a take‐off angle of 20° but decreases to the initial value at a take‐off angle of 70°. The superficial layer of the polymer film between the top of the film to a depth of 10 nm is divided into three superimposing zones. The interpretation is supported by motions of modified macromolecular chains and buried polar groups, chain cleavage and the formation of low‐molecular‐weight molecules which leads to a decrease of the glass transition temperature (plasticizer effect) and migration of short chains from the lowest modified zone toward the surface.
Effects of solvent treatment on cold crystallization behavior and morphology of poly(ether ether ketone)
Authors: Woo Eamor M. , Chang Wei J. , Hong Chia‐H. , Chen Chuh‐Y.
Published: April 2003

Isothermal crystallization kinetics at temperatures between 160–194°C and the morphology of virgin and solvent‐treated poly(ether ether ketone) (PEEK) were investigated by using differential scanning calorimetry, scanning electron microscopy (SEM), and wide‐angle X‐ray scattering analysis. Kinetic analysis showed that the cold crystallization of virgin (untreated) PEEK proceeds with an Avrami exponent of n = 2,5–2,6, and the SEM results revealed a grainy‐texture morphology with no regular spherulites, suggesting a planar growth. The X‐ray characterization revealed low to medium crystallinity, which is consistent with the SEM results. This is quite different from the typical impinged spherulitic morphology of high crystallinity in melt‐crystallized PEEK. Post cold‐crystallization annealing at temperatures near the melting point (300–320°C), however, induced a spherulitic morphology resembling that produced from melt crystallization. Furthermore, methylene dichloride treatment on PEEK was found to significantly affect the cold‐crystallization kinetics and the resulting morphology. The cold crystallization of solvent‐desorbed PEEK samples proceeds with n = 1,0–1,2, reflecting probably an irregular line growth with heterogeneous nucleation. Additionally, SEM examination revealed a highly porous texture in the desorbed/cold‐crystallized PEEK that hindered direct observation of the actual crystalline morphology; nevertheless, neither spherulites nor planar lamellar crystals were observed.
Grafting reaction of macromolecules with pendant amino groups via photoinitiation with benzophenone
Authors: Si Kun , Qiu Kun Yuan
Published: April 2003

N‐(3‐Dimethylaminopropyl) acrylamide (DMAPAA) and N‐(3‐dimethylaminopropyl) methacrylamide (DMAPMA) were prepared and polymers with pendant amino groups were synthesized via copolymerization of methyl methacrylate (MMA) with DMAPMA. With benzophenone (BP) as a sensitizer, the photo‐grafting reaction of acrylonitrile (AN) onto poly(MMA‐co‐DMAPMA) was investigated. The formation of a graft copolymer is confirmed by means of IR spectroscopy, elemental analysis and viscometry. The photoreaction of BP with polymers having pendant amino groups was studied by means of electron paramagnetic resonance (EPR) spectroscopy. It revealed that an alkylaminomethylene radical and a semipinacol radical are produced by the photoreaction. Amino end‐group analysis also proved that the radical formed from the amino component can initiate radical polymerization. Based on the EPR studies and amino end group analysis, the photo‐grafting reaction mechanism is proposed.
Tailored rigid‐flexible block copolymers, 1. Synthesis of diblocks of poly(p‐benzamide) and poly(m‐phenylene isophthalamide)
Authors: Chavan Nayaku N. , Ciferri Alberto , Dell'Erba Carlo , Novi Marino , Renamayor Carmen S.
Published: April 2003

Anilino‐terminated poly(m‐phenylene isophthalamide) [PhNH(MPD‐I)] and benzoyl terminated poly(p‐benzamide) [PhCO(PBA)] were coupled according to a one‐pot two‐step scheme of Yamazaki's reaction. Diblock copolymers with varying length of the flexible PhNH(MPD‐I) segment, and similar length of the rigid PhCO(PBA) block, were freed from unbound homopolymers exploiting their selective solubility in N,N‐dimethylacetamide (DMAc) containing varying amounts of LiCl. The method should also allow a fractionation of the compositional distribution of the copolymers. Copolymers were characterized by 1H NMR spectroscopy, thermal analysis and intrinsic viscosity. In an aggregating solvent the viscosity appears to decrease with the length of the flexible block.
Synthesis of poly(ethylene glycol)‐modified urethane acrylates and their soap‐free emulsification
Authors: Kim Ju‐Young , Suh Kyung‐Do
Published: April 2003

In order to prepare the soap‐free emulsion of urethane acrylates, poly(ethylene glycol)‐modified urethane acrylates (PMUA), containing poly(oxyethylene) chains as terminal groups, were synthesized by reaction of poly(ethylene glycol) (PEG) with residual isocyanate groups. The size of the droplets of PMUA emulsions decreases as the molar ratio of PEG to 2‐hydroxyethyl methacrylate (2‐HEMA) increases. The interfacial activity of PMUA was confirmed by the measurement of the adsorption isotherm at the water/benzene interface. The chain length of poly(oxyethylene) and the type of polyol (PTMG, PPG) affects significantly the size of the droplets and the stability of the PMUA emulsions.
Poly(germanium thiolate): a new class of organometallic polymers having a germanium‐sulfur bond in the main chain
Authors: Shoda Shin‐Ichiro , Iwata Satoru , Kim Hyun Joon , Hiraishi Masafumi , Kobayashi Shiro
Published: April 2003

A novel germanium‐containing copolymer 3 a having a germanium(IV) unit and a trimethylene sulfide unit alternatingly in the main chain was prepared by the combined use of a germylene, 1,3‐bis(trimethylsilyl)‐1,3‐diaza‐2‐germa(II)‐indan (1 a) and thietane (2). The resulting copolymer has a very high molecular weight (M̄w > 106). The usage of a germylene, bis[bis(trimethylsilyl)aminato]germanium(II) (1 b), as a comonomer also gave an alternating copolymer 3 b with high molecular weight in good yields. On the other hand, the reaction of a germylene, bis(N‐trimethylsilyl‐tert‐butylaminato)germanium(II) (c), with thietane afforded a 1 : 1 adduct 4c having a 1‐thia‐2‐germacyclopentane structure without producing an alternating copolymer.
Study on the morphology in composite emulsion particles produced by seed emulsion polymerization
Authors: Liu Zhengping , Liu Fengqi , Liu Zhiqiang , Tang Xinyi
Published: April 2003

A series of poly(ethyl acrylate)/polystyrene composite emulsions with different compositions and levels of emulsifier was produced by seed emulsion polymerization. The morphology of the composite particles was inferred from their coalescence ability detected by torsional braid analysis. It was found that the poly(ethyl acrylate) will partially move to the exterior of the particles when using it as a seed, and the increase of surface tension of the particles can enhance this diffusion.
Cationic ring‐opening polymerization of 2‐isopropenyl‐4‐methylene‐1,3‐dioxolane in donative solvents
Authors: Park Jaekyeung , Kihara Nobuhiro , Endo Takeshi
Published: April 2003

2‐Isopropenyl‐4‐methylene‐1,3‐dioxolane (1) undergoes cationic polymerization in donative solvents without crosslinking to afford poly(ether‐ketone) 2 having two unitstructures. When solvents having medium donor number (DN = 14,1–17,1), such as acetonitrile, dioxane, ethyl acetate, and propylene carbonate, were used, 2 was obtained in high yields. When solvents having DN (>19,2), such as diethyl ether, DMF, and DMAc, were used, the rate of polymerization decreased considerably, although polymerization proceeded even in the most donative solvent, DMAc (DN = 27,8). The ratio of the unit‐structures was independent of the solvent used. When ethanol was used as the solvent, ethoxyacetone and methacrolein were obtained instead of 2. It was concluded that hard nucleophiles such as ethanol attack at the α′‐position of terminal oxyallyl cation, while soft nucleophiles such as monomer 1 attack at the α‐or γ‐position.
Liquid crystallinity of poly(ester‐imide)s derived from biphenyl‐4,4′‐diol and ω‐amino acids. Studies on low molecular weight model compounds
Authors: Orzeszko Andrzej
Published: April 2003

The liquid crystallinity of poly(ester‐imide)s obtained from biphenyl‐4,4′‐diol, ω‐amino acids and trimellitic anhydride is discussed. Four models 1–4, similar to repeating units I–III, were prepared from biphenyl‐4,4′‐diol or biphenyl‐4‐ol and 6‐phthalimido‐hexanoic acid, 6‐(4‐carboxyphthalimido)hexanoic acid and N‐hexyltrimellitimide. DSC and microscopic studies revealed that only biphenyl groups esterified with two aromatic acids are thermotropic, and those parts of the chain probably induce liquid crystallinity.
Linear non‐conjugated dienes from biomass as termonomers in EPDM synthesis, 3. Conventional versus metallocene catalysis
Authors: Dolatkhani Marc , Cramail Henri , Deffieux Alain
Published: April 2003

The synthesis in the presence of the rac‐EtInd2ZrCl2/MAO catalytic system of new EPDM terpolymers based on linear non‐conjugated dienes issued from biomass, 3,7‐dimethylocta‐1,6‐diene (3,7‐DMO) and 5,7‐dimethylocta‐1,6‐diene (5,7‐DMO), is described. 5,7‐DMO can be readily incorporated in ethylene/propylene (E/P) chains, while 3,7‐DMO does not react in the presence of the metallocene catalyst. The reactivity of these linear dienes is compared with that of 2‐ethylidenebicyclo[2.2.1]hept‐5‐ene (ENB), the preferred termonomer for the industrial synthesis of EPDMs. With the metallocene catalyst, the reactivity of 5,7‐DMO is close to that of ENB, suggesting that 5,7‐DMO is a good candidate for the synthesis of a new EPDM. A comparison with the conventional catalysis based on vanadium systems shows that the advantages of the metallocene catalysis consist in higher catalyst activities and higher incorporation rates of the termonomers in the polymer without any noticeable side reaction. The structural and physico‐chemical characteristics of the various terpolymers, investigated by NMR, SEC and DSC, also underline that the use of metallocenes allows one to prepare EPDM based on linear dienes, with an homogeneous chemical composition and a controlled structure.
Photocleavage mechanism of polyimides having cyclobutane rings
Authors: Ohkita Hideo , Tsuchida Akira , Yamamoto Masahide , Moore James A. , Gamble Donald R.
Published: April 2003

The photocleavage reaction of dimer model compounds of photosensitive polyimides having cyclobutane rings in the main chain was studied. Efficient photocleavage was observed for the dimer models (CBAM2, CBAM4, and CBPM2) which had an electron‐donating aromatic substituent at the electron‐accepting imide group. On the other hand, the cleavage quantum yield was nearly zero for a dimer (CBCM2) which had a cyclohexane substituent instead of the aromatic ring. Solvent polarity effects on the cleavage quantum yield revealed that these dimers gave the largest photocleavage efficiency in medium‐polar solvents. The transient absorption band of the excited triplet of CBPM2 was effectively quenched by oxygen, whereas no oxygen quenching was observed for the cleavage quantum yield. This leads to the conclusion that the cyclobutane ring in the polyimide is photocleaved via the excited singlet intramolecular CT state.
Aspects of hydrogen activation in propene polymerization using MgCl2/TiCl4/diether catalysts
Authors: Chadwick John C. , Morini Giampiero , Albizzati Enrico , Balbontin Giulio , Mingozzi Ines , Cristofori Antonio , Sudmeijer Olof , Van Kessel Gerard M. M.
Published: April 2003

13C NMR analysis of the chain‐end distribution of poly(propylenes) prepared using the highly active catalyst system MgCl2/TiCl4/diether—AlEt3 has revealed particularly high proportions of butyl chain‐ends in polymers prepared at relatively low hydrogen pressures. This indicates that the high sensitivity of this type of catalyst to hydrogen, both with respect to catalyst activity and polymer molecular weight, can largely be ascribed to chain transfer following regioirregular (2,1‐) insertion, such an insertion leading to a species having low activity in chain propagation. Isotactic stereoregularity increases with increasing hydrogen pressure, indicating that a stereoirregular insertion may also slow down the chain propagation, again leading to chain transfer and resulting in the conversion of a potential chain defect into an isobutyl chain‐end. Analysis of highly isotactic polymer fractions isolated via temperature rising elution fractionation revealed the presence of both butyl and isobutyl chain‐ends, indicating that even the most highly stereo‐specific sites in MgCl2‐supported catalysts are not totally regiospecific.
Microstructures of emulsified polymer blends
Authors: Adedeji Adeyinka , Jamieson Alex M. , Hudson Steven D.
Published: April 2003

Morphologies of solvent‐cast blends of immiscible polymer pairs emulsified with block copolymers have been examined using transmission electron microscopy. The morphology of such blends is controlled by the delicate balance in the swelling of each block copolymer segment by the corresponding compatible homopolymers. By manipulating the relative swelling via changes in molecular weight and enthalpic interactions, a variety of morphologies including macrophase co‐existing with microphase, and microphase alone, with structures ranging from spheres to vesicles, vesicles co‐existing with worm‐like microdomains, and phase‐inverted networks (PIN), are observed. The morphologies of ternary blends of the type A/A‐b‐B/B and A/X‐b‐B/B can be related to the phase behavior observed in the binary A/A‐b‐B and A/X‐b‐B blends.
Kinetic study of the heterogeneous anionic coordinated polymerization of ethylene oxide
Authors: Letourneux Jean‐Pierre , Hamaide Thierry , Spitz Roger , Guyot Alain
Published: April 2003

New heterogeneous catalytic systems for anionic ring opening polymerization of oxygenated heterocycles are obtained by grafting alkylaluminium moieties on porous silica. Adding alcohol in excess causes the formation of aluminium alkoxides and allows a rapid exchange reaction between the grafted active centers and the free alcohols remaining in the solution, so that more polymer molecules than the number of metal atoms used are produced. An interesting feature is the facility to obtain functionalized oligomers because these exchange reactions lead to polymer chains end‐capped by moieties derived from the alcohol molecules. The kinetic behaviour was investigated for different monomer, alcohol and aluminium concentrations. An activation is observed for a well‐defined alcohol concentration range which is interpreted in terms of the enhancement of the nucleophilic reactivity of the oxygen atom of the alkoxide due to the coordination of the free alcohol onto the active centers and the share of the acidic vacancy of the aluminium atom.
Synthèse de l'acide 2‐acrylamido 2‐méthylpropanoïque et copolymérisation avec l'acrylamide
Authors: Camail Michel , Margaillan André , Thuret Sandrine , Vernet Jean‐Louis
Published: April 2003

The synthesis of 2‐acrylamido‐2‐methylpropanoic acid (2A2MPA) was carried out starting from 2‐methylpropanoic acid. Copolymerizations of the 2A2MPA salt (2A2MPANa, monomer A) with acrylamide (AM, monomer B) were investigated using K2S2O8 as initiator. They were terminated before reaching 15% conversion. A range of feed compositions was selected (2A2MPANa increasing from 10 to 100 mol‐%) and the compositions of the copolymers obtained were assessed through 13C NMR. The reactivity ratios for the couple A, B were determined as rA = 0,76 and rB = 1,06. One additional copolymerization was allowed to reach 100% conversion, and the final copolymer showed interesting drag reduction properties.
Interaction of N‐tert‐butylaziridine with π‐electron acceptors, 2. Polymerization initiated by tetracyanoethylene
Authors: Christova Darina Ch. , Velichkova Rumiana S. , Panayotov Ivan M.
Published: April 2003

The interaction of N‐tert‐butylaziridine (TBA) with the strong π‐electron acceptor tetracyanoethylene (TCNE) was investigated, which results in ring‐opening polymerization of the aziridine. Charge‐transfer complex formation between TBA and TCNE was proved by means of UV/VIS spectroscopy and is assumed to be the first stage of the initiation. There is evidence that only linear TBA homopolymers are formed and TCNE is not covalently bound in the polymer chains as comonomer. The acceptor is present in the final products as a stable complex with the nitrogen atoms along the polyaziridine chains.
Synthesis and phase behaviour of new carbazole containing liquid crystal side chain polysiloxanes
Authors: Arnim Volkmar v. , Finkelmann Heino , Dobarro Alicia , Velasco Dolores
Published: April 2003

A series of chiral mesogenic side chain polymers containing a carbazole unit have been synthesized and investigated with regard to their liquid crystal (1c) phase behaviour. The carbazole units are linked either via the 2‐position with a 1‐oxycarbonyl‐4‐alkoxylphenyl moiety (end‐on) or via the 9‐position with an alkyl chain (side‐on) to polymethylsiloxane. Only end‐on polymers with long spacers or a ratio bigger one of spacer length and the free lateral alkyl chain length exhibit stable or metastable smectic phases. The side‐on polymers are only isotropic or crystalline.
Polymerization of cyclic monomers, 2. Synthesis and radical polymerization of vinylcyclopropanes
Authors: Zeuner Frank , Moszner Norbert , Rheinberger Volker
Published: April 2003

New 1,1‐disubstituted 2‐vinylcyclopropanes were synthesized by reaction of the corresponding malonyl diesters with trans‐1,4‐dibromo‐2‐butene and of sodium hydride. The structure of the 2‐vinylcyclopropanes could be confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. Radical polymerization of the 2‐vinylcyclopropanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) and di‐tert‐butyl peroxide (DtBPO), respectively, gives transparent polymers. In case of the liquid monomers, the polymerization is accompanied by negative volume changes. Spectroscopic investigations show that 2‐vinylcyclopropanes primarily undergo opening of the cyclopropane ring forming an 1,5‐addition polymer.
Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 7. Poly(ester‐imide)s based on 3,4:3″,4″‐p‐terphenyldicarboximide
Authors: Sato Moriyuki , Ujiie Seiji , Hirata Tomohiro
Published: April 2003

New thermotropic liquid crystalline semi‐rigid homo‐ and copoly(ester‐imide)s composed of the 3,4:3″,4″‐p‐terphenyldicarboximide and/or the biphenyl unit and flexible aliphatic chains were prepared by polytransesterification using a dihexanol derivative of 3,4:3″,4″‐p‐terphenyldicarboximide and/or a dioxydihexanol of biphenyl as monomers. Differential scanning calorimetry (DSC) measurements, polarizing microscope observations and powder X‐ray analyses at various temperatures indicated that the homopolymer containing the 3,4:3″,4″‐p‐terphenyldicarboximide unit forms a smectic phase and the copolymers a nematic phase. It is suggested that the 3,4:3″,4″‐p‐terphenyldicarboximide unit acts as a good mesogen.
Polyanhydrides, 8. Hydrolytic degradation of aromatic poly(ester‐anhydride)s
Authors: Kricheldorf Hans R. , Jürgens Claas
Published: April 2003

The hydrolytic degradation of three aromatic poly(ester‐anyhdride)s, PEA's, was studied at 25°C in buffer solutions at pH 6 and pH 7 over a period of 16 and 14 months, respectively. Two PEA's (1 and 2a) possessed an ester/anhydride mole ratio of 75 : 25. The loss of weight, the film thickness, elemental analyses, IR spectra, GPC curves and SEM micrographs were recorded. It was found that the degradation of the molecular weights is much faster than the loss of weight and the decrease of the film thickness. During the first 12 months the hydrolysis mainly involved the anhydride groups. No significant difference was observed between pH 6 and pH 7. The third PEA (2b) only contained 5% of anhydride groups. It showed little degradation at pH 6 or pH 7 over a period of 12 month. A rapid degradation involving ester groups occurred at pH 4 or pH 9. All results together clearly indicate that, in addition to an erosion of the surface, a penetration of water into the hydrophobic PEA's occurs, followed by a more or less random hydrolysis of anhydride groups.
Characteristics of permeation and separation of xylene isomers through poly(vinyl alcohol) membranes containing cyclodextrin
Authors: Miyata Takashi , Iwamoto Tooru , Uragami Tadashi
Published: April 2003

The characteristics of permeation and separation for xylene isomers through poly(vinyl alcohol) membranes containing cyclodextrin (CD‐PVA membranes) were investigated by pervaporation and evapomeation. Evapomeation is more effective for the separation of xylene isomers through the CD‐PVA membrane than pervaporation. An increase in CD content gives rise to an increase in a p‐xylene‐permselectivity through the CD‐PVA membrane by evapomeation. This is attributed to the stronger affinity of CD for p‐xylene as compared with o‐xylene. Especially, the CD‐PVA membrane at a CD content of 40 wt.‐% shows a higher separation factor than has ever been reported. When the p‐xylene concentration in the feed is lower, the p‐xylene‐permselectivity is improved. The mechanism of permeation and separation for xylene isomers is discussed from the standpoint of solution‐diffusion theory.
Study of the structure of polyethylene and poly(tetrafluoroethylene) radiation grafted ion‐exchange copolymers
Authors: Turmanova Sevdalina , Dimitrova Antoaneta , Kostov George , Nedkov Emanuel
Published: April 2003

Cation‐ and anion‐exchange copolymers were synthesized by radiation induced copolymerization of acrylic acid and 4‐vinylpyridine onto polyethylene and poly(tetrafluoroethylene) (PTFE) films. The grafting was carried out by the direct method of single or multiple (discrete) irradiation by γ‐rays from a 60Co source. The grafting degree was from 10 to 121% for polyethylene and from 2.5 to 50% for poly(tetrafluoroethylene), depending on the irradiation dose (1–50 kGy). The calorimetric curves of the copolymers synthesized showed a glass transition temperature (Tg) at 333 ± 10 K. The enthalpies of melting and crystallization decreased with increasing degree of grafting. The data from wide angle X‐ray analysis indicated an increase of the amorphous part with degree of grafting. At lower grafting degrees of poly(acrylic acid) and poly(4‐vinylpyridine) (up to 15%) onto PTFE matrix, the size of the crystallites was found to increase. The penetration of the grafted functional monomer leads to partial deorientation of the initial LDPE film.
α,ω‐Dihydroxy telechelic poly(methyl methacrylate) via β‐scission (radical addition‐fragmentation) chain transfer polymerisation by macromonomer chain transfer agents, as prepared by catalytic chain transfer polymerisation
Authors: Haddleton David M. , Topping Clare , Hastings Jeremy J. , Suddaby Kevin G.
Published: April 2003

α,ω‐Dihydroxy telechelic poly(methyl methacrylate) has been prepared by β‐scission (radical addition‐fragmentation) chain transfer polymerisation. Hydroxyethyl methacrylate dimer macromonomer prepared from catalytic chain transfer polymerisation and isolated as a pure compound is shown to be an efficient chain transfer agent. The mode of chain transfer is via β‐scission which results in the dimer breaking in half on addition to a propagating poly(methyl methacrylate) radical terminating the polymerisation and providing a hydroxyethyl methacrylate radical which reinitiates polymerisation. A combination of these two events leads to dihydroxy telechelic products, demonstrated to have a functionality of 2.05 by a combination of NMR and size exclusion chromatography (SEC). The chain transfer coefficients of these methacrylic macromonomers is concentration dependant exhibiting a type of “bootstrap” effect. This ultimately leads to a limiting low molecular weight telechelic product by the use of dimeric β‐scission chain transfer agents. A combination of high field NMR and matrix assisted laser desorption time‐of‐flight mass spectrometry has been utilised to demonstrate the structure of the products. The combination of catalytic chain transfer polymerisation and β‐scission chain transfer has been demonstrated to be a powerful tool in the controlled polymerisation of methacrylates by radical methodology.
Synthesis and properties of poly(1‐alkyl‐3‐methylene‐2‐pyrrolidone)s
Authors: Iskander George M. , Ovenell Toni R. , Davis Thomas P.
Published: April 2003

A series of α‐methylene‐N‐alkyl‐2‐pyrrolidone monomers with varying length of the alkyl chain from C1 to C8 were synthesised. The monomers were subjected to free radical polymerisation to yield a range of polymers each with a different balance in hydrophobic/hydrophilic properties originating from the pyrrolidone moiety and the N‐alkyl chain. The equilibrium water content of polymers crosslinked with ethylene dimethacrylate were found to decrease with increasing alkyl chain length. The glass transition temperatures of the polymers are reported ranging from 98°C to ‐5°C on going from the methyl to the octyl derivative. The thermal degradation of the polymers was studied using thermogravimetric analysis and pyrolysis gas chromatography‐mass spectroscopy. The polymers were found to degrade at ca. 400°C predominantly via an unzipping mechanism. Pyrolysis at 450°C results in five products.
Thermal properties and crystallization behavior of poly(ether ether ketone ketone)/poly(ether biphenyl ether ketone ketone) copolymers
Authors: Shibata Mitsuhiro , Yosomiya Ryutoku , Jiang Zhenhua , Fang Zhijie , Wu Zhongwen
Published: April 2003

Thermal properties of poly(ether ether ketone ketone) (PEEKK)/poly(ether biphenyl ether ketone ketone) (PEDEKK) copolymers were investigated by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The glass transition temperature (Tg) increases from 154°C to 183°C as the content of PEDEKK units increases. The melting point (Tm) of the copolymers varied in the range between 314°C and 409°C and showed the behavior of eutectic type copolymer. From the investigation of the crystallization behavior of the copolymers, it was found that the cold‐crystallization temperature (Tc′) of the amorphous copolymers assumes a maximum value for the copolymer with a mole fraction of the PEDEKK segment (nB) of about 0.6, isothermally crystallized PEEKK and the PEEKK/PEDEKK copolymer exhibit double‐melting behavior.
Effect of styrene on the polymerization of acrylamide in inverse microemulsion
Authors: Bartoň Jaroslav , Juraničová Viera
Published: April 2003

The macroviscosity of a single‐phase toluene/styrene/sodium bis(2‐ethylhexyl)sulfosuccinate/water/acrylamide Winsor IV inverse microemulsion prior to polymerization as a function of the volume fraction ϕaw, of the dispersed aqueous (water + acrylamide) phase at 20°C reaches three distinct maxima of 16, 66, and 30 mPa ·;s for ϕaw values 25%, 46%, and 62%, respectively. At 60°C, the viscosity maxima practically vanish and the macroviscosity of the dispersion systems is in the range of 5–7 mPa · s. The overall maximum (co)polymerization rate of acrylamide and styrene increases with increasing ϕaw. On the other hand, an increase of the mass ratio styrene/toluene leads (for a given ϕaw value) to a decrease of the overall maximum (co)polymerization rate regardless of the nature of the initiator used. This points to an effective competition between monomer in the oil phase (slow homopolymerization of styrene and/or (co)polymerization of styrene with acrylamide dissolved in the oil phase) and monomer in the water pools of inverse micelles (rapid homopolymerization of a major part of acrylamide) for initiator radicals and/or (co)oligomer radicals.