bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(phenylenevinylene)‐type conjugated alternating copolymers: Synthesis and optical properties in solution
Authors: Hilberer Alain , Van Hutten Paul F. , Wildeman Jurjen , Hadziioannou Georges
Published: April 2003

We have synthesized a series of new conjugated alternating copolymers containing oligo(p‐phenylenevinylene) units of well‐defined size and structure as conjugated chromophores in their main chain. In order to interrupt the conjugation between chromophores, the oligomers were linked to each other either via non‐π‐conjugated silylene units or directly, but in a non‐coplanar way. In this paper we describe the synthesis, the structural characterization and the optical properties in solution of these new copolymers.
Poly(vinyl alcohol) having amino sugar as the pendant group: Synthesis, characterization and binding of concanavalin A
Authors: García‐Oteiza Mari Carmen , Sánchez‐Chaves Manuel , Arranz Felix
Published: April 2003

Poly(vinyl alcohol) (PVAL) samples partially functionalized with 4‐nitrophenyl carbonate groups were obtained by reaction of PVAL with 4‐nitrophenyl chloroformate using pyridine as a catalyst. 2‐Amino‐2‐deoxy‐D‐glucose (glucosamine) was virtually quantitatively bound to PVAL activated with 4‐nitrophenyl carbonate groups. Glucosamine‐carrying PVAL (PVAL‐G) and Concanavalin A (Con A) in phosphate buffer (pH 7,2) at room temperature were proven to interact with each other.
Preparation and evaluation of novel side‐chain liquid‐crystalline polydienes using photoinitiated free‐radical cyclopolymerization
Authors: Buxton Ian Peter , Hall Alan William , Lacey David
Published: April 2003

This investigation has shown that the technique of photoinitiated free‐radical polymerization can be used successfully to produce a variety of side‐chain liquid‐crystalline (SCLC) polydienes, which contain novel alicyclic ring structures along the polymer backbone. With the appropriate side chain, ferroelectric SCLC polymers can be prepared exhibiting wide S ranges and low Tg values. By synthesising a polydiene incorporating a lactone‐ring structure, clear evidence is provided that these types of polymers do contain an alicyclic ring structure along the polymer backbone. The systematic approach adopted for this investigation has also shown that the low DP values obtained for all the polydienes were due to degradative chain transfer.
Correction to “The glass transition of mixtures of polystyrene with alkyl‐terminated oligostyrene – experimental evidence for microphase separation in a polymer blend”1
Authors: Abetz Volker , Müller Gunther , Stadler Reimund , Schlick Shulamith
Published: April 2003

In this correction note we compare the predictions of the phase diagram of a bidisperse polystyrene blend by using different approaches for the segmental χ‐parameter. Depending on the approach very different results are obtained.
Physical aging of poly(ether sulfone) from enthalpy relaxation measurements
Authors: Jong Shi Ru , Lee Jun Sheng , Yu Tzyy Lung
Published: April 2003

Enthalpy relaxation due to physical aging of hydroxyl‐terminated poly(ether sulfone)s (PES) with various molecular weights was studied by DSC at three aging temperatures between Tg − 45°C and Tg − 10°C. The experimental results revealed that both the average enthalpy relaxation time 〈τ〉 and limiting enthalpy relaxation ΔH∞ decrease slightly with increasing molecular weight for PESs aged at the same temperature intervals Tg − Ta (where Ta < Tg). This behavior is not quite consistent with the enthalpy relaxation process of polystyrene. Agrawal reported that the relaxation spectra for polystyrenes with different molecular weights could be superimposed when Tg − Ta was the same. The experimental results of the present work suggest that the motion of segments is affected by intermolecular hydrogen bonding through the OH groups of the PES chain ends.
Metallocene‐catalyzed propene/1‐hexene copolymerization: Influence of amount and bulkiness of cocatalyst and of solvent polarity
Authors: Forlini Fabrizio , Fan Zhi‐Qiang , Tritto Incoronata , Locatelli Paolo , Sacchi Maria Carmela
Published: April 2003

An investigation on the effect of the variation of the amount and the structure of cocatalyst and of polarity of the solvent on propene/1‐hexene copolymerization with the isospecific catalyst rac‐[ethylenebis(1‐indenyl)]zirconium dichloride (rac‐(EBI)ZrCl2) was performed. A noticeable enhancement of copolymerization activity and a moderate increase of the molecular weights were observed with increasing MAO/Zr ratio as well as upon mixing methylaluminoxane (MAO) and AliBu3, while isotacticity and comonomer composition are not affected by such variations. On the other hand, a gradual increase in CH2Cl2 content in the CH2Cl2/toluene solvent mixture, which greatly increases the copolymerization activity, noticeably influences the molecular weight and sensibly enhances the 1‐hexene comonomer content. The formation of cationic active species, separated from their counterions, might be the cause of the better accessibility of the active sites for the bulkier comonomer.
Illustration of surface crosslinking of different polymers treated in argon plasma
Authors: Poncin‐Epaillard Fabienne , Vallon Sophie , Drévillon Bernard
Published: April 2003

The influence of argon plasma on polycarbonate (PC) and poly(propylene) (PP) has been studied in terms of structural changes and reaction mechanisms. In situ UV‐visible ellipsometry reveals formation of a surface layer with a higher refractive index than the untreated polymer. The increase in the refractive index is attributed to polymer densification, which is assigned to crosslinking. However, a decrease in the average molecular weight of the PC is also observed and two populations of macromolecules of different size are detected by light scattering measurements, revealing a competition between crosslinking and degradation. The reaction mechanisms were investigated using Nuclear Magnetic Resonance (1H NMR) and in situ IR ellipsometry. Degradation is caused by carbonate bond breaking, while crosslinking seems to be related to a decrease in methyl groups. The ellipsometry results are correlated with amorphous phase extraction and 1H NMR analysis of modified PP. The crosslinking mechanism involves the elimination of methyl groups, and also the formation of exomethylenic bonds. Spectroscopic ellipsometry appears to be a valuable tool to study the interaction between a plasma and a polymer, as UV‐visible ellipsometry is sensitive to structural changes in the polymer, while IR ellipsometry detects the appearance and disappearance of chemical groups in a surface layer.
Synthesis of poly(ethylene oxide) with a terminal amino group by anionic polymerization of ethylene oxide initiated by aminoalcoholates
Authors: Mosquet Martin , Chevalier Yves , Le Perchec Pierre , Guicquero Jean‐Pierre
Published: April 2003

Poly(ethylene oxide)s having a primary or secondary amino group at one chain end have been synthesized by direct anionic polymerization of ethylene oxide initiated by aminoalcoholates. The ring opening reaction of ethylene oxide by the amino group could be avoided when the alcoholate was reactive enough, that is, with potassium alcoholates in dry aprotic medium (THF). In this case, a living anionic polymerization of ethylene oxide occurred, with full conversion of the monomer. This is shown by the NMR and molecular weight characterizations of the polymers and kinetic studies of the polymerization.
Complex‐radical cyclocopolymerization of allyl a‐(N‐maleimido)acetate with styrene and maleic anhydride
Authors: Rzaev Zakir M. O. , Salamova Ulviye U. , Altindal Şemsettin
Published: April 2003

Radical copolymerizations of allyl a‐(N‐maleimido)acetate (AMI) with styrene (D, electron‐donor) or maleic anhydride (A, electron‐acceptor) were carried out in benzene and/or methyl ethyl ketone (MEK) at 50–70°C in the presence of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The structure and properties of copolymers synthesized were derived from IR, chemical, DTA and TGA analyses. Side‐chain unsaturation of macromolecules was also proved by the crosslinking effect observed. Kinetic parameters of copolymerization such as complex‐formation (Kc), cyclization (kcyc), and copolymerization constants and ratios of chain growth rates for the participation of monomer charge transfer complexes (CTC) and free monomers for both systems were obtained: Kc = 0,20 ± 0,01 and 0,05 ± 0,005 L/mol in CH3COOH‐d4 at 35 ± 0,1°C (1H NMR method) for D…AMI and AMI… A complexes, respectively; kcyc · 105 = 1.71 and 0,66 L/(mol · s), r1 = 0,13 ± 0,01 and 0,037 ± 0,002, r2 = 0,048 ± 0,002 and 0,052 ± 0,002 (by Kelen‐Tüdőş method), k12/k21 = 0,20 and 0,62, k1c/k12 = 0,6 and 29,8, k2c/k21 = 4,8 and 9,1 for the D‐AMI and AMI‐A systems, respectively. The results show that alternating cyclocopolymerization reactions are realized which are carried out via a “mixed” mechanism in the D‐AMI system and via a “complex” mechanism in the AMI‐A system, with formation of cyclolinear macromolecules containing side‐chain unsaturated fragments of “allyl” (D‐AMI copolymer) and “imide” (AMI‐A copolymer) types. The synthesized copolymers easily undergo crosslinking by thermotreatment (105°C, 30 min) and/or by UV‐irradiation (25°C, 15 min), which was confirmed by DTA and TGA analyses.
PdCl2‐induced chain transfer reaction by hydrogen at the initial stage of propene polymerization with MgCl2‐supported Ziegler catalyst
Authors: Mori Hideharu , Iizuka Takehiko , Tashino Kunihiko , Terano Minoru
Published: April 2003

The PdCl2‐induced chain transfer reaction by hydrogen in the initial stage of propene polymerization with a MgCl2‐supported Ziegler catalyst was studied by means of the stopped‐flow polymerization technique. A chain transfer reaction was found to occur even in the initial stage of the polymerization in the presence of PdCl2 which dissociates the hydrogen molecule. PdCl2 itself has no ability for propene polymerization as well as for the chain transfer reaction. The results indicate that the chain transfer reaction occurs through atomic hydrogen formed on PdCl2 particles.
Synthesis and radical polymerization behavior of a novel methacrylate with an L‐leucyl‐L‐alanylglycine peptide moiety
Authors: Murata Hironobu , Sanda Fumio , Endo Takeshi
Published: April 2003

The synthesis and radical polymerization behavior of a novel methacrylate having a peptide moiety, N‐benzyloxycarbonyl‐L‐leucyl‐L‐alanylglycine 2‐methacryloyloxyethyl ester (1), are described. 1 shows radical polymerizability in spite of the bulky peptide moiety. Only the ester group near the peptide moiety of poly(1) could be hydrolyzed selectively and completely in the hydrolysis of poly(1) in an alkaline solution.
Orientation behavior of smectic polymer networks by uniaxial mechanical fields
Authors: Nishikawa Etsushi , Finkelmann Heino
Published: April 2003

Polymer networks showing different smectic polymorphism with either an interdigitated smectic A to undulated smectic A phase transformation or an interdigitated smectic A to double layer smectic C phase transformation are synthesized. Their orientation behavior in uniaxial mechanical fields is investigated by means of X‐ray scattering techniques and thermal expansion measurements. By applying uniaxial extension to the smectic elastomers in the isotropic state ordered smectic networks result with the director uniformly aligned parallel to the strain axis. These networks are optically transparent. Uniaxial deformations of the ordered smectic networks in the direction parallel and perpendicular to the director are performed that also help to elucidate the structure of the smectic phases. We find a reorientation process of layers of the ordered smectic C network. The spontaneous elongation in the direction of the director at the isotropic to smectic A phase transformation of the smectic elastomers is observed by thermoelastic measurements. This indicates that the polymer backbone conformation in the smectic elastomers is prolate in contrast to previous observations of oblate chain conformation in linear smectic polymers.
Synthesis of biomedical, fluorescence‐labelled polyesterurethanes for the investigation of their degradation
Authors: Ciardelli Gianluca , Kojima Kazushige , Lendlein Andreas , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

The synthesis and characterization of fluorescence‐labelled, phase segregating block polyesterurethanes based on the known biocompatible and degradable materials poly[(R)‐3‐hydroxybutyric acid] (PHB), poly(ϵ‐caprolactone) (PCL), and poly[(ϵ‐caprolactone)‐co‐glycolide] (PCL/PGA) is described. To introduce fluorescence labels in the amorphous domains of the polymers, phenacyl 10,11‐dihydroxyundecanoate (PDUA) was synthesized and copolymerized with a PHB diol, a PCL diol, and aliphatic diisocyanates. After cleavage of the protecting group (without degradation of the polymer backbone), the carboxyl group was reacted with a fluorescent amine (dansylcadaverine) in the presence of 4,6‐diphenylthieno[3,4‐d]‐1,3‐dioxol‐2‐one 5,5‐dioxide (Steglich reagent). Also a polymer containing 13C‐labelled carboxy groups was synthesized and the labelling reaction monitored by 13C NMR spectroscopy. To introduce fluorescence labels in the hard segment of the polymers, a new low‐molecular‐weight diol based on poly[(R)‐hydroxybutyric acid] and containing protected carboxy groups was synthesized. After the deprotection, the carboxy groups were reacted with a fluorescent amine (dansylcadaverine) in the presence of an activating system based on dicyclohexylcarbodiimide. The labelled PHB diol was then copolymerized with a poly[(ϵ‐caprolactone)‐co‐glycolide] diol and an aliphatic diisocyanate. The so obtained fluorescence‐labelled block polyesterurethanes are promissing materials for the investigation of the biocompatibility and degradation of the corresponding, non‐labelled materials (DegraPol®) by means of fluorescence‐aided microscopic and spectroscopic techniques.
Photocalorimetric monitoring of the polymerization of an oligo(ethylene glycol) dimethacrylate in oligo(ethylene glycol) dimethyl ethers
Authors: Sandner Barbara , Kotzian Norbert , Tübke Jens , Wartewig Siegfried , Lange Otfried
Published: April 2003

The course of the 2,4,6‐trimethylbenzoyldiphenylphosphine oxide initiated free‐radical photopolymerization of an oligo(ethylene glycol) dimethacrylate ((EG)23DMA) in two oligo(ethylene glycol) dimethyl ethers ((EG)3DME and (EG)11DME) in the presence of LiCF3SO3 has been studied by means of differential scanning calorimetry (DSC), FT‐Raman spectroscopy and sol‐gel analysis. In order to obtain the kinetical data of the fast photopolymerization, the photo‐DSC curves were corrected numerically. Both, the initial and the maximum polymerization rates were found to depend on the concentration of the monomer and the photo‐initiator with the order 2,5 and 0,2, respectively. Upon addition of LiCF3SO3, the polymerization rate is increased. Grafting reactions from (EG)11DME were observed resulting in its partially linking to the poly(methacrylate) network.
NMR imaging of technical SBR vulcanizates under dynamic mechanical load
Authors: Hauck Daniela , Blümler Peter , Blümich Bernhard
Published: April 2003

Inhomogeneous heating of carbon‐black filled SBR (styrene‐co‐butadiene rubber) cylinders was mapped by NMR imaging in situ during dynamic mechanical load. The linear relationship betweenT2and temperature was used for direct imaging of temperature profiles. Experiments were performed as a function of shear frequency between 0 and 10 Hz and of carbon black contents between 10 and 70 phr (parts per hundred rubber). For a composite cylinder with a hard core and a soft shell an unexpected heat distribution was observed.
On the interaction of supported zirconocene catalysts with alkylaluminium co‐catalysts
Authors: Semikolenova Nina V. , Zakharov Vladimir A.
Published: April 2003

The interaction of supported metallocene catalysts with methylaluminoxane leads to the desorption of the metallocene compound from the surface of the support and the formation of highly active homogeneous complexes. The catalytic properties of the system and characteristics of polyethylene formed are determined by these species.
Influence of propene pressure on the isotacticity of polypropene produced with typical C1‐symmetric metallocene and Ziegler‐Natta catalysts
Authors: Schneider Martin Julius , Kaji Eiichi , Uozumi Toshiya , Soga Kazuo
Published: April 2003

Polymerization of propene was conducted at 40°C under reduced pressure (0.35 – 1.0 atm) using the C1‐Symmetric threo‐iPr(3‐tBuCp)(3‐tBuInd)ZrCl2/MAO and TiCl4/MgCl2/Al(iBu)3 catalyst systems and the effect of propene pressure on the microstructure of the resulting isotactic polypropene was investigated. In the case of C1‐symmetric metallocene, the [mmmm]‐pentad fraction decreased moderately with decreasing propene pressure, but the magnitude of decrease was much smaller than those reported by Busico et al. using typical C2‐symmetric metallocenes. Whereas, the [mmmm]‐pentad fraction of isotactic polypropene obtained with the conventional Ziegler‐Natta catalyst did not change so much in the pressure range. Thus, epimerization of the growing polymer chain was found to be drastically dependent upon the catalyst system.
Coordination polymers from 1,3,4‐thiadiazole‐2,5‐dithiol and metal ions
Authors: Ortega Pedro , Vera Leonel R. , Guzmán Miguel E.
Published: April 2003

The copolymerization of 1,3,4‐thiadiazole‐2,5‐dithiol (bismuthiol) with 1+, 2+, and 3+ valent metals is reported. Polymerization conditions were mimicked by means of Job's technique of solutions mixing. The polymers in aqueous solutions do not conduct electricity, but electrolytes are formed in proportion to polymer formation and the pH changes. The metal concentration in solutions confirms the metal‐ligand stoichiometry. The UV absorption of the ligand (at 320 nm) decreases and light scattering by polymer (at 380 nm) increases with polymer formation. The stoichiometry of polymers (obtained from the conductivity inflection point and metal analysis) is as follows. Mt2+: bismuthiolate = 1 : 1; Al3+ : bismuthiolate = 2 : 3 and Ag+ : bismuthiolate = 2 : 1. Equations describing polymer formation on the basis of the solution conductivities are presented, and a model of polymer formation is proposed. It is concluded that 2+ valent metals from linear polymers but Al3+ forms branched polymers.
Studies on the pH‐dependent swelling properties and morphologies of chitosan/calcium‐alginate complexed beads
Authors: Lee Ok‐Sub , Ha Byung‐Jo , Park Soo‐Nam , Lee Yoon‐Sik
Published: April 2003

Chitosan/calcium‐alginate beads were prepared by a coacervation method in aqueous medium. Their swelling properties and morphologies were studied. Complexed beads with a mean diameter of 500 μm were obtained by dropwise addition of a sodium alginate solution into a chitosan‐calcium chloride solution. From scanning electron microscopic studies, we observed that chitosan modifies the morphology of calcium‐alginate beads. The swelling properties of chitosan/calcium‐alginate beads are different from those of calcium‐alginate beads. In the case of the calcium‐alginate beads, the swelling volume increases as the pH of the medium increases. However, chitosan/calcium‐alginate beads show a maximum swelling volume at pH 9.0.
Thermally stimulated current and DSC studies of the dual glass transitions in side‐chain liquid crystalline copolysiloxanes containing 4‐[(S)‐2‐methylbutoxy]phenyl 3‐chloro‐4‐alkenyloxybenzoate side groups
Authors: Chang Huey‐Ling , Hsu Chain‐Shu
Published: April 2003

The synthesis of side‐chain liquid crystalline copolysiloxanes containing ω‐[4‐[4‐[(S)‐2‐methylbutoxy]phenoxycarbonyl]‐2‐chlorophenoxy]alkyl side groups is presented. Differential scanning calorimetry, optical polarizing microscopy and X‐ray diffractometry reveal smectic mesomorphism for most of the obtained polymers. The copolysiloxane with three methylene units in the spacer is the only one showing no mesomorphic property. The other four copolysiloxanes, containing four, five, six or eleven methylene units in the spacer, display a smectic A phase. All of the obtained polymers present dual glass transition behavior by both DSC and thermally stimulated current (TSC) techniques. The first glass transition (Tg1) at lower temperature is due to the segmental motions of the polysiloxane backbone, while the second glass transition (Tg2) is due to the cooperative relaxation motions of spacers and mesogenic units.
Endgroup‐functionalized polytetrahydrofurans by polymerization with functional triflate esters, 1. PolyTHF‐macromonomers
Authors: Dubreuil Marjorie F. , Goethals Eric J.
Published: April 2003

Functional esters of trifluoromethanesulfonic acid (triflate esters) have been synthesized by reaction of functional alcohols (allyl alcohol, 2‐hydroxyethyl acrylate (HEA) and methacrylate (HEMA), 4‐hydroxybutyl acrylate (HBA)) with triflic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. These esters were used in situ as initiators for the polymerization of tetrahydrofuran (THF), with the purpose to synthesize endgroup‐functionalized polyTHF's. The method was first tested with the system butanol/triflic anhydride. With this combination, quantitative formation of the ester and, subsequently, controlled polymerization of THF was realized. Similar results were obtained with the system allyl alcohol/triflic anhydride. With 2‐hydroxyethyl acrylate (HEA) and 2‐hydroxyethyl methacrylate (HEMA), the synthesis of the triflate ester was accompanied by the formation of substantial amounts of ether formed by reaction of the triflate ester with a second molecule of alcohol. This was attributed to an enhanced reactivity of the triflate ester due to nucleophilic assistance by the carbonyl group in γ‐position. This assistance is not possible with 4‐hydroxybutyl acrylate (HBA) and with this alcohol, the formation of the ester was almost quantitative. The synthesis of polyTHF acrylate macromonomer was successful with the latter system.
Thermal and thermo‐oxidative degradation of polystyrene in the presence of ammonium sulfate
Authors: Zhu Xinsheng , Elomaa Matti , Sundholm Franciska , Lochmüller Charles H.
Published: April 2003

Ammonium sulfate was compounded into polystyrene (PS) to modify thermal degradation of PS. At elevated temperatures, ammonium sulfate decomposes into ammonia, sulfuric acid and further into sulfur trioxide and water. The aim of the study was to investigate how these acidic and oxidizing compounds affect the thermal and thermo‐oxidative degradation behaviour of polystyrene. Thermal degradation was studied by thermochromatography (ThGC). In addition, isothermal pyrolysis at 340°C was carried out and the dissolved parts of the residues were analyzed by size exclusion chromatography (SEC). The random chain scission index Sr (based on the components of evolving gases), the chain scission number Sx (based on the number‐average molar mass), the oxygen effect K, and the synergistic effect Z were used to describe thermal and thermo‐oxidative degradation processes. The increases of Sr and Sx with the increase of ammonium sulfate imply that thermal degradation of PS is modified. The synergistic effect Z indicated that, at low addition levels, ammonium sulfate synergistically promotes thermo‐oxidative degradation with oxygen. At high addition levels, it promotes thermo‐oxidative degradation with oxygen.
Investigation of a fine‐grain MgCl2‐supported Ziegler catalyst by stopped‐flow propene polymerization: Model for the formation of active sites induced by catalyst fragmentation during polymerization
Authors: Mori Hideharu , Yoshitome Masaki , Terano Minoru
Published: April 2003

A fine‐grain catalyst, as a model of catalyst fragmentation in the course of polymerization, was prepared by grinding an original MgCl2‐supported Ziegler catalyst. In order to clarify the nature of the active sites generated after catalyst fragmentation, the kinetic parameters for propene polymerization with both catalysts were estimated using the stopped‐flow method. The active sites concentration of the fine‐grain catalyst was higher than that of the original MgCl2‐supported catalyst, indicating that the grinding treatment induced the formation of new active sites. However, the propagation rate constant and stereoregularity of polypropene remained unaffected. This is an indication that the nature of the active sites formed after the grinding treatment was the same as that of active sites on the original MgCl2‐supported catalyst.
Studies on the phase separation of polyetherimide‐modified epoxy resin, 2. Effect of molecular weight of PEI on the structure formation
Authors: Cui Jun , Yu Yinfeng , Chen Wenjie , Li Shanjun
Published: April 2003

The effect of molecular weight on the structure formation of polyetherimide modified epoxy system was studied. Using time‐resolved light scattering (TRLS) and scanning electron microscopy (SEM), the process of phase separation and the morphology of the blends were investigated. As the curing reaction proceeds, the phase separation occurs first in the large molecular weight polyetherimide (PEI) modified epoxy resin and the time of occurrence of phase separation is increased with the decrease of the inherent viscosity of PEI. Because of the different viscosity of the blends, the blends display varied morphologies from a PEI particle dispersion to co‐continuous phases. Changing of the PEI molecular weight may be another possible route to control the morphology of the PEI modified epoxy resins.
Synthesis and characterization of halogen‐containing polyisophthalamides
Authors: Álvarez Julio C. , García José M. , De la Campa José G. , de Abajo Javier
Published: April 2003

Two series of aromatic polyamides were prepared from m‐phenylenediamine (MPD) and 4,4′‐diaminodiphenyl sulfone (DDS) in combination with a set of new halogenated diacyl chlorides, namely, 5‐fluoroisophthaloyl chloride, 5‐chloroisophthaloyl chloride, 5‐bromoisophthaloyl chloride and 5‐iodoisophthaloyl chloride. The polymers were synthesized in high yields and in high molecular weight (as determined by gel permeation chromatography) by means of the low temperature condensation method. Noticeable changes in the spectral characteristics of the halogen‐modified polyisophthalamides were observed compared to those of the corresponding unmodified polyisophthalamides. Slight improvements were observed for the glass transition temperatures, which increased 5–30°C relative to those of the conventional polyisophthalamides. Moreover, a correlation was found between the size of the halogen substituents and the increase in Tg values. Thermogravimetric analysis showed that the new polymers are almost as thermally resistant as the unmodified ones, while solubility in organic solvents was some‐what poorer.
Radical products of poly(triphenylcarbinol) thermolysis
Authors: Shishlov Nikolay M. , Akhmetzyanov Shamil S. , Novoselov Igor V. , Nikiforova Galina I.
Published: April 2003

At least three kinds of stable paramagnetic species are formed in films of poly(triphenylcarbinol) 1 upon thermolysis in vacuo up to 500°C. “Low temperature” radicals of triarylmethyl type (RTAMT1) are created in the 120 ÷ 220°C temperature region. These radicals give rise to a symmetric ESR signal (g = 2.0026 ± 0.0003; ΔH ≈ 1.0 mT) with poorly resolved hyperfine structure and to an absorption band (AB) of allowed transition with λmax = 407 nm in UV spectra. The spectral region of forbidden transitions, assumed for the RTAMT1, is masked by a nonradical AB, in particular by that of quinoid structure of Chichibabin hydrocarbon type with λmax = 595 nm. From 220°C to 280°C the “high temperature” radicals RTAMT2 appear, with a strong bathochromic shifted AB of forbidden transition (λmax = 710 nm). Maximum concentration of RTAMT2 (≈︁1020 spin/g) is achieved at ≈︁280°C. Possible structures of both kinds of RTAMT are discussed. At T ≥ 300°C paramagnetic species that differ from RTAMT are formed in 1.
Stereoselectivity in cyclic and acyclic metathesis reactions
Authors: Basset Jean‐Marie , Leconte Michel , Lefebvre Fredéric , Hamilton James G. , Rooney John J.
Published: April 2003

Metathesis polymers of norbornene and 1‐methylnorbornene were prepared using a well‐defined aryloxy(chloro)neopentylidene tungsten initiator which behaves in a stereo and regioselective manner giving predominantly cis polymers and a strong head‐to‐tail bias in the case of 1‐methylnorbornene. This is in accord with the observation that this initiator is also very stereoselective in acyclic metathesis.
Relation between the alternating monomer unit sequence and the cis and trans linkage configurations at the cyclic maleic anhydride units in the copolymers of styrene and maleic anhydride prepared in carbon tetrachloride
Authors: Ha Nguyen T. H. , Fujimori Kiyohisa , Craven Ian E.
Published: April 2003

The monomer unit triad sequence distribution and the cis/trans linkage configurations at the cyclic maleic anhydride (MA) units in the copolymers of styrene (ST) and MA prepared in CCl4 with AIBN at 50°C were quantitatively determined by 13C DEPT NMR spectroscopy. So much as 61 % of the linkages at the MA units were found to be in cis configuration, which was considered to be formed by a participation of the 1:1 electron donor‐acceptor complex formed between ST and MA in the propagation step. The mole fraction of the cis configuration was found to be proportional to the mole fraction of alternating triad sequences when the monomer unit sequences approach to be completely alternating. This supported the proposal that, in alternating and semi‐alternating copolymerizations, the alternating sequences were formed mainly by the addition of the complex. The equilibrium constant of the complexation in CCl4 at 23°C was determined to be 0,21 L/mol.
Thermal and morphological study of fractionated poly(3‐hydroxybutyric acid‐co‐3‐hydroxypropionic acid)
Authors: Cao Amin , Ichikawa Masafumi , Ikejima Tetsuya , Yoshie Naoko , Inoue Yoshio
Published: April 2003

The thermal and morphological characteristics of fractionated poly(3‐hydroxybutyric acid‐co3‐hydroxypropionic acid)s (P(3HB‐CO‐3HP)) with narrow comonomer compositional distribution, as well as the natural poly(3‐hydroxybutyric acid) (P(3HB)) and chemosynthetic poly(β‐propiolactone) (PPL) were studied by means of differential scanning calorimeter (DSC) and infrared spectroscopy (IR). It is seen that melting point (Tm), heat of fusion (ΔH) and glass transition temperature (Tg) decrease with the increase of the content of 3HP units up to 60.5 mol‐%. Employing 13C NMR in the solution, the sequence distributions of the fractionated copolyesters were revealed not to be in accordance with the results of the random statistical model. The carbonyl IR absorption bands were further resolved by curve fitting into several components stemming from the bond stretchings in the different molecular environments known as the amorphous, crystalline and intermediate regions. It is demonstrated that the contributions which belong to the crystalline regions show intrinsic absorption peaks at 1724.0, 1723.8 and 1729.1 cm−1 for P(3HB), P(3HB‐CO‐3HP)s and PPL, respectively. In the case of P(3HB‐CO‐3HP)s, the relative intensities of contributions originating from the crystalline regions decrease with the increase of 3HP units up to 60.5 mol‐%. However, only the P(3HB) type of lattice structure is formed despite the variation of the 3HP unit content. Moreover, the effect of the substrates (silicon wafer and KBr) used for preparation of the IR samples on the crystallization behavior was also investigated.
Polymers of carbonic acid, 21. Ring‐opening polymerization of cyclobis(diethylene glycol carbonate) by means of BuSnCl3, SnOct2 or Bu2SnO as catalysts
Authors: Kricheldorf Hans R. , Lossin Martina , Mahler Andreas
Published: April 2003

Cyclobis(diethylene glycol carbonate), (DEGC)2, was synthesized by polycondensation of diethylene glycol with diethyl carbonate followed by thermal depolymerization of the crude polycarbonate in vacuo. BuSnCl3‐initiated polymerizations of (DEGC)2 in chlorobenzene at 100°C gave poor results. Therefore, all further polymerizations were conducted at 145°C in bulk. Two series of polymerizations were performed with BuSnCl3 as catalyst, so that either the time was varied at constant monomer/initiator (M/I) ratio, or the M/I ratio at constant time. Two analogous series were conducted with SnOct2 With both catalysts high yields but only moderate molecular weights were obtained. SnOct2 yielded polycarbonates having octoate end‐groups, which were detected by 1H NMR spectroscopy. (DEGC)2 was also polymerized with Bu2SnO at M/I = 200 or 500 with variation of time. The highest yields and molecular weights were obtained at the shortest time, whereas longer times caused rapid depolymerization. Therefore, Bu2SnO appeared to be the most reactive catalyst. Both 1H and 13C NMR spectra proved that all poly(diethylene glycol carbonates) prepared in this work possess an alternating sequence of ether and carbonate groups.
An “in situ” reaction of propagating chain‐end as iodoacetal in the polymerization of butyl vinyl ether initiated by I2 and HI/I2 systems
Authors: Deák György , Kéki Sándor , Gnandt Csaba , Zsuga Miklós
Published: April 2003

The polymerization reaction of butyl vinyl ether with initiating systems I2 and HI/I2 was investigated with glass fiber photometry and conductometry by monitoring the characteristic changes in the absorbance versus time curve and in the conductivity versus time curve. Aldehyde end‐groups were observed and a mechanism of their formation is proposed.
Copolymerization of 1,3‐dienes with CpTiCl3‐MAO. Some cases in which the mode of monomer coordination affects the copolymer structure
Authors: Ricci Giovanni , Porri Lido
Published: April 2003

The following pairs of monomers were copolymerized using the catalyst system CpTiCl3/methylaluminoxane (MAO): 1,3‐butadiene/(E)‐1,3‐pentadiene, 1,3‐butadiene/4‐methyl‐1,3‐pentadiene and 4‐methyl‐1,3‐pentadiene/(Z)‐1,3‐pentadiene. The copolymers were characterized by NMR and infrared examination. 4‐Methyl‐1,3‐pentadiene/(Z)‐1,3‐pentadiene and 1,3‐butadiene/(E)‐1,3‐pentadiene gave copolymers having a composition intermediate between that of an ideal and that of an alternating copolymer. 1,3‐Butadiene/4‐methyl‐1,3‐pentadiene gave block copolymers only. These results have been interpreted on the basis of a different mode of coordination of the monomers. The cis‐η4 coordination is by far the most stable for 1,3‐butadiene and (E)‐1,3‐pentadiene, while for (Z)‐1,3‐pentadiene and 4‐methyl‐1,3‐pentadiene there is probably an equilibrium between the cis‐η4 and trans‐η2 form. Both these forms are reactive in the case of (Z)‐1,3‐pentadiene, while only the trans‐η2 form is so in the case of 4‐methyl‐1,3‐pentadiene.
XPS analysis of poly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] film surfaces exposed to an allylamine low‐pressure plasma
Authors: Mas André , Jaaba Hassan , Schué François , Belu Anna M. , Kassis Camille M. , Linton Richard W. , Desimone Joseph M.
Published: April 2003

Homogeneous and stable layers were deposited through allylamine plasma polymerization (75 W, 100 Pa, 15 min) onto poly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] (91 : 9 wt.‐%) (P(HB‐co‐9%HV)) film surfaces, XPS analysis using take‐off angles of 20° and 70° and performed 10 days and 20 days after plasma treatment gives information on the composition (in atom%) of the modified surface: C, 62.74; N, 19.60; O, 17.65. The unexpected oxygen percentage is weaker if argon plasma pretreatment (25 W, 40 Pa, 5 min) is applied. Then, a succinct mechanism is proposed. The study of changes in element ratios and binding energy values shows that the majority of incorporated functional groups seem to be amide and imine groups.
New polymer syntheses, 92. Biodegradable, thermotropic copolyesters derived from β‐(4‐hydroxyphenyl)propionic acid
Authors: Kricheldorf Hans R. , Stukenbrock Thomas
Published: April 2003

Binary copolyesters were prepared by polycondensation of the trimethylsilylester of acetylated β‐(4‐hydroxyphenyl)propionic acid (HPPA) with acetylated 4‐hydroxybenzoic acid (HBA), vanillic acid (VA), 6‐hydroxy‐2‐naphthoic acid (HNA), 4‐hydroxycinnamic acid (HCA) or 4′‐hydroxybiphenyl‐4‐carboxylic acid (HBCA). Only the binary copolyester derived from 4‐hydroxybenzoic acid proved to be enantiotropic nematic, whereas all other binary copolyesters were more or less crystalline and infusible. Furthermore eight ternary copolyesters were prepared, which all proved to be soluble and thermotropic. 13C NMR spectroscopy proved a random nature of the sequences of the copolyesters, which were only obtained when transesterification catalysts such as Ti(OiPr)4 or MgO were used for the polycondensations. Optical microscopy revealed that five of the eight copolyesters form a homogeneous nematic phase above 220 or 250°C. However, in three cases the nematic melt contained crystalline particles which did not melt below 400°C. According to the WAXS powder patterns and DSC measurements most binary and ternary copolyesters are semicrystalline and form an imperfect orthorhombic crystal lattice. In three cases, the solid phase is best described as a hexagonal columnar mesophase.
A new photoinitiator system based on p‐nitroaniline in the presence of aliphatic tertiary amines
Authors: Costela Angel , García‐Moreno Inmaculada , Dabrio Javier , Sastre Roberto
Published: April 2003

Several kinetic aspects of the polymerization of dodecyl acrylate photoinitiated with p‐nitroaniline in the presence of an aliphatic tertiary amine, either 2‐(N,N‐diethylamino)ethanol or 2‐(N,N‐dimethylamino)ethyl methacrylate, acting as coinitiator, were studied. Under low absorption conditions, the rate of polymerization was found to be proportional to the square‐root of the incident light intensity, the initiator and the coinitiator concentrations. The polymerization behaviour was analyzed also under aerobic conditions. Under identical irradiation conditions, both initiation and polymerization processes present higher rates and quantum yields than those obtained with conventional aromatic ketone photoinitiators.
ABC triblock polyampholytes containing a neutral hydrophobic block, a polyacid and a polybase
Authors: Giebeler Ellen , Stadler Reimund
Published: April 2003

Well defined ABC triblock copolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(tert‐butyl methacrylate) and polystyrene‐block‐poly(4‐vinylpyridine)‐block‐poly(tert‐butyl methacrylate) were synthesized by sequential living anionic polymerization in tetrahydrofuran. Triblock copolymers with narrow molecular weight distribution were obtained. Hydrolysis of the poly(tert‐butyl methacrylate) block yields polystyrene‐block‐polyvinylpyridine‐block‐poly(methacrylic acid) which demonstrates pH‐dependent solution properties. Interpolymer complexation of the polyvinylpyridine and poly(methacrylic acid) blocks in the micellar solution is studied in dependence of the pH in solution by potentiometric, conductometric and turbidimetric titration, and in bulk by FTIR spectroscopy.
All‐trans oligomers of 2,5‐dialkyl‐1,4‐phenylenevinylenes–metathesis preparation and characterization
Authors: Thorn‐Csányi Emma , Kraxner Peter
Published: April 2003

Oligomers of 2,5‐dialkyl‐1,4‐phenylenevinylenes (DR‐OPV, R = C4H9, C7H15, C10H21 and C6H11) (CyH) were prepared via metathesis polycondensation of the respective 2,5‐dialkyl‐1,4‐divinylbenzenes. The synthesis of the monomers is described. The highly active metal‐alkylidene complex Mo(NAr)(CHCMe2Ph)[OCMe(CF3)2]2 (Ar = 2,6‐dimethylphenyl) serves as a catalyst. The degree of polymerization can be controlled by variation of the solvent and by the length of the side chains, since the reaction proceeds as a precipitation polycondensation. The DR‐OPVs are bilious‐green products and, depending on the molecular weight, soluble in various solvents like toluene, THF and CHCl3. The solutions are highly fluorescent and coloured. The DR‐OPVs have vinylic end groups. The vinylene double bonds are of all‐trans configuration. Due to their rigid‐rod structure, the DR‐OPVs synthesized have a distinct tendency to crystallize in a highly ordered state, forming a sanidic layer structure.
Determination of the transfer constant of α‐thioglycerol in methyl methacrylate free‐radical polymerization
Authors: Fernández‐García Marta , Delgue Michel , Madruga Enrique López
Published: April 2003

Using the Mayo and the Clay‐Gilbert method, the transfer rate coefficient of α‐thioglycerol (TG) was determined at 50°C for the polymerization of methyl methacrylate (MMA) in a 3 mol · L−1 tetrahydrofuran solution using different amounts of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The transfer rate coefficient was found to be independent of the initiator concentration and higher by a factor of 1.6 when obtained according to the Clay‐Gilbert method compared to the Mayo method.
Synthesis and characterization of poly‐L‐lysine with controlled low molecular weight
Authors: Van Dijk‐Wolthuis Wendelmoed N. E. , van de Water Leon , van de Wetering Petra , Van Steenbergen Mies J. , Kettenes‐van den Bosch Jantien J. , Schuyl Wijnand J. W. , Hennink Wim E.
Published: April 2003

N‐Carboxy‐(Nϵ‐benzyloxycarbonyl)‐L‐lysine anhydride (Z‐L‐lysine NCA) was polymerized in dimethylformamide with triethylamine, diethylamine or hexylamine as initiator, at varying molar ratios of NCA to initiator (M/I ratio). After removal of the protecting Z‐group the resulting poly‐L‐lysine was characterized with 1H NMR and MALDI TOF MS. Both diethylamine‐ and hexylamine‐initiated polymerization yielded poly‐L‐lysine in which the initiators were incorporated at the carboxylic end of the polymer. This indicates that the NCA polymerization occurred exclusively via nucleophilic attack of the initiator on the monomer. On the other, hand, when triethylamine was used as the initiator, poly‐L‐lysine was obtained in which no triethylamine‐derived end group could be detected by MS. These polymer chains are most likely end‐capped with an N‐acyl‐2,5‐dioxopiperazine group at the carboxylic end of the polymer. Incorporation of diethylamine and hexylamine allowed determination of the degree of polymerization (DP) of the obtained polymers by 1H NMR. The DP depended linearly on the M/I ratio, for both diethylamine and hexylamine, with higher DPs for the diethylamine‐initiated poly‐L‐lysine at equal M/I ratio.
Generation of a spin polymer through a charge‐transfer complex of a ferrocenyl mesogen with tetracyanoethylene in the solid state
Authors: Tanaka Hitoshi , Mizota Kazuya
Published: April 2003

Some disubstituted ferrocenes and a polymer with flexible pendant ferrocenyl mesogens were found to form a complex with tetracyanoethylene to give a spin molecule even in the solid state at ambient temperature.
Selective synthesis of 4,4′‐biphenyldicarboxylic acid using cyclodextrin as catalyst
Authors: Hirai Hidefumi , Shiraishi Yukihide , Saito Kazuhiro
Published: April 2003

The selective carboxylation of 4‐biphenylcarboxylic acid with carbon tetrachloride in aqueous alkali to obtain 4,4′‐biphenyldicarboxylic acid was achieved by the use of ß‐cyclodextrin and copper powder II under mild conditions.
Command surfaces, 10. Novel polymethacrylates with laterally attached azobenzene groups displaying photoinduced optical anisotropy
Authors: Akiyama Haruhisa , Kudo Kazuaki , Ichimura Kunihiro
Published: April 2003

Polymethacrylates with laterally attached azobenzenes were prepared to cause molecular reorientation of this chromophore in their thin films by linearly polarized irradiation with an exposure energy of less than ca. 100 mJ/cm2. A homogeneous alignment was induced by assembling a nematic liquid crystal cell using a substrate plate covered with the photoirradiated films. The alignment direction of the cell was controlled by changing the electric vector of the actinic light.
Morphology of single‐chain single crystals of poly(ethylene oxide)
Authors: Shi Songhua , Chen Erqiang , Hu Hanjie , Bu Haishan , Zhang Ze
Published: April 2003

Single‐chain particles of poly(ethylene oxide) (PEO) were prepared by spreading a 10‐4 wt.‐% solution of PEO in benzene on a hot water surface. After isothermal crystallization at 317,2 ± 0,1 K for 10 h, regular‐shaped single‐chain crystals were observed. A variety of typical morphologies were also found, and some of them are discussed on the basis of the habit of PEO crystals and various twin modes.
Curing of a rigid rod epoxy resin with an aliphatic diacid: an example of a lightly crosslinked liquid crystalline thermoset
Authors: Giamberini Marta , Amendola Eugenio , Carfagna Cosimo
Published: April 2003

By reacting a rigid rod epoxy terminated molecule (p‐bis(2,3‐epoxypropoxy)‐α‐methylstilbene) with an aliphatic carboxylic acid (decanedioic acid), a lightly crosslinked liquid crystalline network is obtained. This network exhibits a smectic‐like phase. While the mesophasic structure resulted “frozen” by the crosslinks in the case of higly crosslinked liquid crystalline epoxy resins, in this case a reversible transition from the liquid crystalline to the isotropic phase is observed. Moreover, while curing the same rigid rod epoxy molecule with amines resulted in a thermoset with a nematic structure, in this case a more ordered mesophase can be obtained. Preliminary results show that it is possible to orient macroscopically the mesogenic chains by stretching thin films above the glass transition temperature (Tg) and then quickly cooling down to the glassy state. This makes this material very attractive in the field of optical applications.
Pulsed laser terpolymerization of styrene, methyl methacrylate and methyl acrylate
Authors: Schoonbrood Harold A. S. , van den Reijen Bram , de Kock John B. L. , Manders Bart G. , van Herk Alex M. , German Anton L.
Published: April 2003

The propagation rate coefficient of the terpolymerization of styrene, methyl methacrylate and methyl acrylate in bulk was successfully determined at three different monomer compositions. The temperature was varied between 18 and 80°C. The resulting data at 50°C were not in agreement with predictions according to the terminal model with binary reactivity ratios that have been determined by fitting copolymer composition data with the terminal model. This indicates that here also the penultimate unit affects the kinetics.
Temperature‐induced phase transition behaviors of random vs. graft copolymers of N‐isopropylacrylamide and acrylic acid
Authors: Chen Guohua , Hoffman Allan S.
Published: April 2003

Graft copolymers of poly(N‐isopropylacrylamide) (PNIPAAm) on a poly(acrylic acid) backbone retain the temperature‐induced phase transition behavior of PNIPAAm over a wide range of compositions even at pH 7,4 and should be useful for sustained‐release, bioadhesive drug delivery systems at physiologic conditions.
Applying principles of polymer miscibility for thermal imaging
Authors: Schild Howard G.
Published: April 2003

Knowledge of polymer‐polymer interactions is employed to design an improved media for dye diffusion thermal transfer (D2T2). Selecting the donor and receiver sheet binder polymers to be an immiscible pair results in acceptable images free from the “sticking” during printing that is observed if these two polymers are miscible. This approach has the potential to improve upon the dye density and surface characteristics of current commercial systems.
Poly(organophosphazenes) containing azo dyes
Authors: Facchin Giacomo , Gleria Mario , Minto Francesco , Bertani Roberta , Guglielmi Massimo , Brusatin Giovanna
Published: April 2003

In this paper we describe a method for the functionalization of catenapoly[bis(4‐hydroxyphenoxy)‐λ5‐phosphazene] with diazonium salts to form new, deeply‐coloured, phosphazene copolymers containing variable amounts of azo dyes attached to the polyphosphazene skeleton. The degree of functionalization in these substrates is regulated in order not to exceed 20% of the sites available in the pristine polyphosphazene and to maintain a high percentage of unreacted, free, hydroxy groups, in the final, coloured copolymers. These species are still very reactive and able to undergo further functionalization reactions.