bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, characterization and photoreaction of side‐chain liquid‐crystalline polymers and copolymers comprising alkenyloxy‐biphenyl mesogen
Authors: Kawatsuki Nobuhiro , Takatani Ken , Yamamoto Tohei , Sangen Osamu
Published: April 2003

Photoreactive (meth)acrylate monomers having mesogenic groups based on 4‐hexyloxy‐4′‐(3‐methyl‐2‐butenyloxy)biphenyl and 4‐hexyloxy‐4′‐(2‐butenyloxy)biphenyl were synthesized. Methacrylate monomers (3c, d) and acrylate monomer having 3‐methyl‐2‐butenyloxy group (3b) were polymerized by free radical mechanism; the acrylate monomer having 2‐butenyloxy group (3a) caused gelation during the polymerization. To obtain photoreactivity, 4‐benzoylphenyl (meth)acrylates were radically copolymerized with monomers 3b and 3d. Thermal behavior of (co)polymers was determined by differential scanning calorimetry, polarized optical microscopy and temperature‐controlled X‐ray analysis. (Co)polymers showed liquid‐crystalline behaviour with nematic and smectic phases. UV‐irradiation was used to photochemically crosslink copolymer films, and the resultant films were insoluble in organic solvents. The uniaxially oriented copolymer thin film was photo‐crosslinked and showed thermally stable orientation.
Complexation of polyacrylamide and poly(N‐isopropylacrylamide) with poly(acrylic acid). The temperature effect
Authors: Staikos Georges , Karayanni Katerina , Mylonas Yannis
Published: April 2003

We present potentiometric and viscometric results on the interpolymer complexation between polyacrylamide (PAAM) and poly(N‐isopropylacrylamide) (PNIPAAM) with poly(acrylic acid) (PAA) in dilute aqueous solution. A potentiometric procedure for the determination of the complex stoichiometry in monomeric units has been proposed. The temperature dependence of the strength of the complex formed has been investigated. From the results obtained it has been concluded that hydrogen bonding is the main factor stabilizing the PAAM/PAA complex, strengthened by decreasing the temperature while the much stronger PNIPAAM/PAA complex, strengthened by increasing the temperature, is stabilized by hydrophobic interaction.
Coordinative polymerization of p‐substituted phenyl glycidyl ethers, 1. Effect of electron‐donating groups
Authors: Ronda Joan Carles , Serra Angels , Cádiz Virginia
Published: April 2003

A series of p‐substituted glycidyl phenyl ethers

IUPAC nomenclature: 2,3‐epoxypropyl phenyl ether.

with electron donor groups was prepared using a multistep synthetic method. These compounds were polymerized using four of the most common aluminium‐based coordinative initiators, (C2H5)3Al/H2O (the Vandenberg catalyst), (C2H5)3Al/CH3COCH2COCH3/H2O (the Vandenberg chelate catalyst), [(CH3)2CHO&]2AlOZnOAl[OCH(CH3)2]2 (the Teyssié catalyst) and [(CH3)2CHO]3AV/ZnCI2 (the Price catalyst), all with different Lewis acid character. The influence of the electron‐donor group on the characteristics and conversion was studied. Generally speaking, both the Vandenberg and the Teyssié catalysts yield mostly an insoluble polymer fraction, whereas the Price catalyst was shown to be the most stereoselective catalyst. Moreover, the Vandenberg chelate catalyst gave the highest molecular weight, the Price catalyst the lowest. Thermal characteristics of polymers were studied by means of differential thermal analysis to obtain glass transition temperatuures, melting temperatures and fusion enthalpies.
Coordinative polymerization of p‐substituted phenyl glycidyl ethers, 2
Authors: Ronda Joan Carles , Serra Angels , Cádiz Virginia
Published: April 2003

As a complementary study of a previous work about the influence of the electronic effects of p‐substituted phenyl glycidyl ethers on the polymerization behaviour, a new series of monomers with electron‐withdrawing groups was prepared, i.e., highly reactive p‐functionalized poly(phenyl glycidyl ethers) were prepared. The polymerizations were carried out with four different aluminium‐based coordinative initiators, (C2H5)3Al/H2O (mole ratio 1:0.6) (the Vandenberg catalyst), (C2H5)3Al/CH3COCH2COCH3/H2O (mole ratio 1:1:0.5) (the Vandenberg chelate catalyst), [(CH3)2CHO]2AlOZnOAl[OCH(CH3)2]2 (the Teyssié catalyst) and [(CH3)2CHO]3Al/ZnCl2 (the Price catalyst), all with different Lewis acid character. The influence of the electron withdrawing groups on the characteristics and conversion of polymers was studied. All polymers were characterized by nuclear magnetic resonance spectroscopy showing higher tacticities when the Price catalysts was used. In some cases the degree of conversion was low due to passivation effects which were studied in several experiments.
On the polymer effect observed with macromolecular photoinitiators: A study of the viscosity effect on the starting polymerization rate
Authors: Leclercq Pascal , Buisine Jean‐Marc , Coqueret Xavier
Published: April 2003

Photopolymerizable acrylate compositions including small amounts of poly(butyl acrylate) were submitted to photocalorimetric measurements in order to investigate the effect of the mixture viscosity at zero conversion on the initial polymerization kinetics. No significant change of the initial polymerization rate profile was observed for starting viscosities ranging between 4 and 36 mPa · s and for a given concentration of low molecular weight photoinitiating system of the benzophenone‐amine type. This demonstrates that the polymer effect that leads to a higher value of the initial polymerization rate (Rp)0 when using an analogous photoinitiating system with the same content in polymeric benzophenone chromophores cannot be ascribed to the higher viscosity at zero conversion that results from the presence of the photosensitive macromolecules.
The conformational coil‐globule transition of polystyrene in cyclohexane solution
Authors: Vshivkov Sergei A. , Safronov Alexander P.
Published: April 2003

The phase diagram of a monodisperse high molecular weight polystyrene (Mw = 3.3 · 106, Mw/Mn < 1.06) solution in cyclohexane was thoroughly studied by means of light scattering, cloud point, coexisting phases volume ratio, coexisting phases composition and scanning calorimetry methods, and binodal and spinodal curves were obtained. Coordinates of the UCST (T = 306.2 K, ϕ2 = 1.88 · 10−2) determined by different methods were similar. It was found that the first‐order phase transition curve obtained by calorimetric scanning at 10−6 K/s accurately fits the spinodal of the system within the concentration range of semidilute and concentrated solutions and has a horizontal part in dilute solutions where the temperature of phase transition was found to be 303.86 K, independently of concentration. At the same temperature a deflection point was found on the concentrated branch of the spinodal. The results were taken as calorimetric evidence of a coil‐globule phase transition in the polystyrene solution. It was shown that the collapse of the polystyrene coils takes place in the metastable system between the binodal and the spinodal in the same way as in the homogeneous solution above the binodal.
A new kinetic interpretation of the styrene microemulsion polymerization
Authors: Nomura Mamoru , Suzuki Kiyoshi
Published: April 2003

The polymerization of styrene initiated by potassium peroxodisulfate was conducted at 50°C in oil‐in‐water microemulsions using sodium lauryl sulfate and 1‐pentanol as emulsifier and cosurfactant, respectively. Based on the experimental findings that both particle size and molecular weight of the polymers are almost independent of styrene conversion and the initial initiator concentration, a kinetic scheme of the microemulsion polymerization of styrene is proposed, which assumes that (1) particle nucleation occurs in monomer‐swollen micelles and almost all the radicals in the water phase enter the monomer‐swollen micelles and finally initiate polymerization therein, (2) with negligible radical termination in the water phase and (3) with negligible radical entry into the preformed polymer particles, and accordingly, (4) all chain‐stopping events in the active polymer particles are chain transfer reactions to monomer. Based on this kinetic scheme, a simple kinetic model is proposed, which can explain fairly well the progress of styrene microemulsion polymerization in the initial stage.
Living polymerization of substituted acetylenes by a novel ternary catalyst, MoOCl4Et2ZnEtOH
Authors: Hayano Shigetaka , Masuda Toshio
Published: April 2003

A novel molybdenum oxytetrachloride (MoOCl4)‐based ternary catalyst, molybdenum oxytetrachloride/diethylzinc/ethanol (MoOCl4Et2ZnEtOH), induces the living polymerization of o‐(trifluoromethyl)phenylacetylene. A catalyst composition of MoOCl4:Et2Zn: EtOH (mole ratio = 1:1:3) and anisole as polymerization solvent are favorable. The ratio of weight‐ to number‐average molecular weights Mw/Mn of the polymer was as small as 1,03, and the initiator efficiency was 8%. Living polymerization was verified by multistage polymerization. The polymerization proceeded in a living fashion in the temperature range from 0 to 30°C. The catalyst yielded polymers with small Mw/Mn values also from other phenylacetylenes with bulky ortho substituents and 1‐chloro‐1‐octyne.
Polyurethane networks based on α,ω‐dihydroxytelechelic and on random hydroxyl‐functionalized side chain poly(2‐chloroethyl vinyl ether)s: Synthesis and investigation of mechanical properties
Authors: Bennevault Véronique , Richard Gilles , Deffieux Alain
Published: April 2003

This paper reports on the synthesis and characterization of polyurethane networks based on an α,ω‐dihydroxytelechelic poly(2‐chloroethyl vinyl ether) (PCEVE precursor, type I) and on PCEVE with 2‐hydroxyethyl groups statistically distributed along the chains (PCEVE precursor, type II). The different hydroxyl‐functional polymer precursors were synthesized via “living” cationic polymerization of CEVE to allow the control of molecular weights, molecular weight distributions, as well as, for the dihydroxytelechelic precursor, the chain end functionality. PCEVE precursors of type II were obtained by derivatization of a small fraction of 2‐chloroethyl side groups into 2‐hydroxyethyl groups, using polymer analogous reactions.

The mechanical properties of the corresponding PCEVE‐polyurethane (PU) networks were investigated. Data are analyzed in terms of precursor structure and average chain length between crosslinks. The mechanical properties of the PCEVE‐PU networks are also compared to those of PU networks based on hydroxyl‐terminated polybutadiene (HTPB) prepared according to the same experimental procedure. It was found that the networks based on PCEVE have higher toughness to break and higher elongation properties.
Polymers from coumarins, 3. Design and synthesis of novel fully aromatic coumarin‐containing polyesters
Authors: Fomine Serguei , Delgado Carmen , Fomina Lioudmila , Gaviño Ruben , Ogawa Takeshi
Published: April 2003

A novel coumarin‐containing monomer 6‐[4‐acetoxyphenyl]coumarin‐3‐carboxylic acid (5) was prepared and characterized. It was copolymerized by high‐temperature polycondensation with m‐acetoxybenzoic acid (11) to give copolymers with Mn of 5 300–18 000, soluble in common organic solvents and containing up to 40 mol‐% of monomer 5. All copolymers were amorphous, with Tg increasing with monomer 5 ratio (from 147 to 162°C) and high optical quality films preparable by solution casting from chloroform. All polymers show strong photoemission in the blue‐green region and some of them present electroluminescence.
Ethylene polymerizations with disiloxane‐bridged indenyl and cyclopentadienyl metallocene catalysts
Authors: Wang Baiquan , Su Liming , Xu Shansheng , Feng Ru , Zhou Xiuzhoug , He Dawei
Published: April 2003

ansa‐Tetramethyldisiloxane‐bridged indenyl, tetrahydroindenyl and cyclopentadienyl zirconium complexes 1–4 were prepared. The pure rac‐1–3 and meso‐1–2 complexes were separated by fractional crystallization. Indenyl complexes, both rac‐1 and meso‐1, in the presence of methylaluminoxane (MAO), have very high activities for ethylene polymerization. The molecular weight of polyethylene produced with rac‐1 is extremely high and significantly dependent on polymerization temperature. The tert‐butyl‐substituted cyclopentadienyl complex exhibits low activity and produces polyethylene of low molecular weight.
Copolymerization of poly(propylene) macromonomer with ethylene by (tert‐butanamide)dimethyl(tetramethyl‐η5‐cyclopentadienyl)silanetitanium dichloride/methylaluminoxane catalyst
Authors: Shiono Takeshi , Moriki Yuji , Ikeda Tomiki , Soga Kazuo
Published: April 2003

The copolymerization of ethylene and a poly(propylene) macromonomer, the number‐average polymerization degree (Pn) of which was about 11, was conducted with (tert‐butanamide)dimethyl(tetramethyl‐η5‐cyclopentadienyl)silanetitanium dichloride (CGC‐Ti) combined with methylaluminoxane. The rate of ethylene consumption is increased by adding the macromonomer when copolymerization was carried out at 40°C, whereas such rate enhancement could not be observed at 90°C. It was found that the increase of ethylene polymerization rate is accompanied by the incorporation of the macromonomer. Based on differential scanning calorimetry (DSC) and 13C NMR measurements of the produced polymers, it was proved that the poly(propylene) macromonomer was copolymerized with the present CGC‐Ti catalyst and the Pn value of the macromonomer incorporated in the copolymer does not influence the conversion of the macromonomer.
Polyelectrolyte multilayers containing photoreactive groups
Authors: Laschewsky André , Wischerhoff Erik , Bertrand Patrick , Delcorte Arnaud
Published: April 2003

The synthesis of a photocrosslinkable polycation and its use in the assembly of alternating polyelectrolyte multilayers are described. Characterization by UV/VIS spectroscopy and time‐of‐flight secondary ion mass spectroscopy (ToF‐SIMS) reveals the influence of the crosslinking on the physical properties of the build‐ups. Remarkably, the assembly of such multilayer structures is not only possible on hydrophilic substrates, but also on apolar poly(propylene). In this case, the crosslinkable polycation turns out to be especially useful to obtain stable, solvent resistant coatings.
Synthesis and characterization of poly[3‐(6‐tetra‐hydropyran‐2‐yloxyhexyl)‐2,5‐thienylene]
Authors: Bolognesi Alberto , Mendichi Raniero , Schieroni Alberto , Villa Daniela , Ahumada Oscar
Published: April 2003

The synthesis of poly[3‐(6‐tetrahydropyran‐2‐yloxyhexyl)‐2,5‐thienylene] has been performed with a nickel catalyst, obtaining a highly regioregular polymer. The deprotection of the pyranyl function restores the OH group giving a polymer which is not soluble in the usual organic solvents but soluble in 1‐methyl‐2‐pyrrolidone, indicating that no crosslinks are present. The protected form was characterised by means of GPC, 1H NMR, FTIR and UV‐Vis spectroscopy and was found to give Langmuir‐Blodgett multilayered structures.
Zur Katalyse der stereospezifischen Butadienpolymerisation mit den Katalysatorsystemen aus Nd(η3‐C3H5)3 · dioxan und methylaluminoxan (MAO) sowie Hexaisobutylaluminoxan (HIBAO)
Authors: Maiwald Steffen , Weißenborn Helga , Windisch Heike , Sommer Christian , Müller Gert , Taube Rudolf
Published: April 2003

The activation of the tris(allyl)neodymium complex Nd(η3‐C3H5)3 · dioxane with alkylaluminoxanes (MAO or HIBAO) results in highly selective catalysts for the 1,4‐cis‐polymerization of butadiene (cis‐selectivity up to 80%). Under standard conditions (50°C, toluene), the turnover frequency (TOF) of the catalyst/MAO system amounts to 10–15000 mol butadiene/(mol Nd · h). Molecular weight determinations indicate the formation of only one polymer chain per neodymium center as in a living polymerization reaction, and for the catalyst/HIBAO system the rate law rp = kp [Nd][C4H6] with kp = 8,7 · 10−2 mol/(L · s) (at 25°C) has been derived. As the catalytically active species, a cationic monobutenyl neodymium(III) complex is discussed, which is stabilized through coordinative interaction with the counter anion as well as the growing polybutadiene chain. This cationic complex reacts under insertion with butadiene in a bimolecular fashion.
A novel orientation material for liquid crystals based on modified ladder‐like polysiloxanes
Authors: Tang Yongxing , Cui Li , Xie Ping , Zhang Rongben , Zhang Zhiyong , Wan Boquan
Published: April 2003

A new orientation material for liquid crystals (LCs) based on modified ladder‐like polysiloxanes (LPSs) is investigated. The curing temperature (150–200°C) of these grafted LPSs is much lower than that of the traditionally used polyimides (PIs) (250–300°C). The pre‐tilt angles of a nematic liquid crystal (LC), 4‐pentyl‐4′‐cyanobiphenyl (5CB), are between 2–8°, depending on the rubbing conditions and the side chains. Annealing experiments at 100°C and 180°C demonstrated that the stability of these orientation films is quite well.
Gelation of aqueous solutions of diblock copolymers of ethylene oxide and D,L‐lactide
Authors: Tanodekaew Siriporn , Godward John , Heatley Frank , Booth Colin
Published: April 2003

The thermally‐reversible gelation of aqueous solutions of diblock copolymers of ethylene oxide (E) and D,L‐lactide (L), E42L12, E38L16, E39L20, E41L26, E78L14 and E77L26, has been studied using gelation temperature measurements, polarised light microscopy and NMR spectroscopy. The solutions showed a high temperature gel‐sol boundary but no low temperature gel‐sol boundary. Polarised light microscopy showed that the gel phase was isotropic, and the dependence of sol‐gel temperature on concentration suggested that the micelles were prolate ellipsoidal, rather then spherical. NMR spectroscopy showed that below ca. 60°C, the L block in the micelle core become highly restricted. It is tentatively suggested that this is due to the L blocks forming an ordered structure, thus explaining the absence of a low temperature gel‐sol boundary.
Chain conformation and packing of isopentylcellulose in thin films
Authors: Fakirov Christo , Lieser Günter , Wegner Gerhard
Published: April 2003

Multilayers of isopentylcellulose (systematic name: tri‐O‐isopentyl cellulose, IPC) were investigated by means of electron diffraction. Only the persubstituted cellulose ether showed some order in a multilayer as deposited. IPCs of lower degree of substitution (DS) form ordered layers when annealed at temperatures ≤150°C. IPC molecules adopt helix conformation; the lattices show in this temperature range 3‐fold screw axes. From analogy with known structures of cellulose derivatives we suggest left‐handed 32‐helices. At a temperature of about 210°C IPC multilayers undergo a transition into the liquid‐crystalline state and the feature of a stack of individual layers disappears. This was investigated for an IPC of DS = 3. By subsequent cooling a phase transition into a highly crystalline state takes place. From the huge increase of the crystalline density from initially 1.02 g/cm3 in the multilayer system to 1.40 g/cm3 in the bulk crystal at ambient temperature after having passed the liquid‐crystalline state we infer that the transition of the layered system into the liquid‐crystalline state is accompanied by selection of adjacent chains according to their polarity. Simultaneously the chain conformation is changed into a 4‐fold screw with 2 symmetry related chemical repeats forming the asymmetrical unit. Such a chain conformation is not known for other cellulose derivatives, only trimethylamylose adopts a similar conformation with a distorted 43‐helix.
Light‐scattering study of random disorder in liquid crystalline elastomers
Authors: Clarke S. M. , Nishikawa E. , Finkelmann H. , Terentjev E. M.
Published: April 2003

We report on the structural study of a non‐uniform (polydomain) director texture in nematic and smectic liquid crystalline elastomers. Polarised light scattering is used to probe the equilibrium director correlations in the region of transition under stress between the opaque polydomain material and the transparent, macroscopically monodomain elastomer. A characteristic four‐peak scattering image is obtained in this transient region. The lobes of intensity are oriented along and perpendicular to the axes of crossed polarisers, with anisotropy along the direction of principal extension. We propose a theoretical model, based on the competition between the random disordering field due to the network crosslinks and the external aligning field
Cold crystallization and polymorphism in an oligo(aryl ether ketone)
Authors: Rueda Daniel R. , Zolotukhin Mikhail G.
Published: April 2003

1,3‐Bis(4‐phenoxybenzoyl)benzene(1)was crystallized from the glassy state at different temperatures,Tc, above the glass transition temperature (Tg= 24°C). Analysis of X‐ray diffractograms and DSC thermograms revealed a new polymorphism: a one‐dimensional order phase (G1) and a new crystal phase (G2). In both cases the molecules adopt a linear extended conformation. G1 appears for 30°C <Tc< 35°C and its structure is like that of a smectic phase A with the molecular axis normal to the layer planes. Upon thermal treatment above 35°C G1 converts into the crystal phase G2 which shows an inproving lateral packing of the molecules upon heating. G1 and G2 show melting temperatures around 88 and 98°C, respectively. Provided that the thermal treatment of the cold crystallizing sample is done under ambient conditions, G2 converts into the most stable crystal phase 2 (Tm= 130°C). Similar thermal treatments carried out inside a DSC calorimeter under dry N2‐flow are not capable of provoking the change in the molecular conformation (from a linear extended to a V‐conformation) involved in the crystal phase transition of G2 to phase 2.
Silica supported zirconocenes and Al‐based cocatalysts: surface metal loading and catalytic activity
Authors: dos Santos João Henrique Zimnoch , Dorneles Silvio , Stedile Fernanda Chiarello , Dupont Jairton , de Camargo Forte Maria Madalena , Baumvol Israel Jacob Rabin
Published: April 2003

The Zr surface loading from Cp2ZrCl2 toluene solutions on different kinds of commercial silicas (Grace 948, 952 and 956) was determined by Rutherford backscattering spectrometry. In all silicas, a saturation trend was observed with increasing amount of metal in the initial solution, the largest Zr loading value (1 wt.‐%) being observed for silica Grace 948. Solid surface areas were determined by the BET method before and after metallocene immobilization, revealing that the values do not change after zirconocene impregnation. Two different kinds of cocatalyst were used, methylaluminoxane and trimethylaluminium. The aluminium loading on silica Grace 948 was determined using the 27Al(p,γ)28Si nuclear reaction and titrometry, both showing that methylaluminoxane leads to an “Al grafting” four times more efficient than does trimethylaluminium. Finally, the catalytic activity of these systems was tested in the polymerization of ethylene. The supported catalysts were shown to be active, specially using the low cost trimethylaluminium as a cocatalyst. The polymers obtained with the supported systems exhibited a higher molecular weight than those obtained with the homogeneous system.
A convenient route to poly(methylphenylsilane)‐graft‐polystyrene copolymers
Authors: Jones Richard G. , Holder Simon J.
Published: April 2003

A graft copolymer of polystyrene on poly(methylphenylsilylene) was conveniently synthesised by using the bromomethyl groups of bromomethylated poly(methylphenylsilylene) as initiating sites for the bulk polymerisation of styrene by an atom transfer radical mechanism.
Temperature‐influenced ordering of mesogens in comb‐like liquid‐crystalline poly(methylsiloxane) macromolecules with side groups consisting of “phenyl benzoate” moieties in solution
Authors: Lavrenko Peter , Yevlampieva Natalia , Okatova Olga , Kolbina Galina , Olbrich Michael
Published: April 2003

Comb‐like poly(methylsiloxane) macromolecules P4, P6, and P11, with side groups consisting of “phenyl benzoate” moieties and different alkyl spacers (from 4 to 11 C‐atoms) between the backbone and the mesogenic side groups have been synthesized and investigated as well as low‐molar‐mass compounds M4, M6, and M11, as model molecules analogous to side chains of the macromolecule. The liquid‐crystalline phase transition temperatures have been determined. Mobility of the mesogens and the macromolecule as a whole in dilute solution was studied in external fields (electric and mechanical shear field). In dilute solution under the influence of a sinusoidal electric field, the polymer behaviour is typical of flexible‐chain polymer molecules where each mesogenic unit is oriented independently of the other ones. This is in contrast to the effect observed in a mechanical shear flow field. The Maxwell constant in positive for the solutions of compounds M4, M6, M11 and negative in polymers P4, P6, P11. This indicates the orientation of the macromolecule as a whole in the shear flow field, the mesogenic group main axis being oriented in the direction preferably normal to the macromolecular axis of primary polarizability. Temperature effects are also discussed.
Mesogenic azomethine based diepoxides – monomers for the synthesis of “liquid crystal” thermoset networks
Authors: Mormann Werner , Bröcher Markus , Schwarz Petra
Published: April 2003

A series of azomethine linked di‐ and triaromatic (diad and triad) mesogenic diepoxides was synthesized. The easy accessibility of the corresponding bisphenols from suitable aminophenols, hydroxybenzaldehydes, terephthalaldehyde, and p‐phenylenediamine allows to investigate the influence of substituents and of the arrangement of aromatic rings in the mesogenic core on the thermal and phase behaviour. The unsubstituted triad terephthaldialdehyde based diepoxide forms a smectic mesophase while all the others exert nematic mesophases. Melting points of the unsubstituted triad diepoxides are around 200°C being lowered by the introduction of methyl substituents. The greatest decrease (m.p. about 130°C) is caused by a methyl or a chloro substituent in the central ring, while the clearing point decreases from 260°C for the unsubstituted compounds to app. 230°C.
Bis(cyclopentadienyl)zirconium dichloride supported on zeolites for ethylene polymerization
Authors: Marques Maria De Fátima V. , Henriques Cristiane A. , Monteiro José Luiz F. , Menezes Sonia M. C. , Coutinho Fernanda M. B.
Published: April 2003

Y zeolites with different sodium contents and a sodium mordenite were evaluated as support for bis(cyclopentadienyl)zirconium dichloride as catalyst for ethylene polymerization. The results showed that, although the activities of the supported catalysts were lower than that of the homogeneous system, the average molecular weight of the polyethylene produced from the former was in general much higher than that of the polymer produced in solution. Contrary to the expected trend if the specific area was the dominant factor for catalyst activity, the best catalyst was the one supported on NaM zeolite. Thus, our results indicate that the concentration of framework aluminium atoms is the dominant factor, but that the contribution of the external surface is also important.
Liquid crystalline main chain polymers containing the ferrocene unit as a side group, 2. Variation of the spacer length
Authors: Wilbert Götz , Traud Simone , Zentel Rudolf
Published: April 2003

Four new ω‐ferrocenylalkyl diethyl malonates with varying length of the alkyl group from 4 to 10 methylene units were incorporated via Ti(OiPr)4‐catalyzed copolymerization into smectic liquid crystalline main‐chain polymers in contents of about 10 mol‐%. As mesogenic unit 4,4′‐bis(6‐hydroxyhexyloxy)azoxybenzene was used as diol component and diethyl phenyl malonate as diester component. Polymer analogous oxidation of the ferrocene units leads to liquid crystalline ionomers, which also form smectic phases. The ferrocene containing polymers were investigated in the oxidized and non‐oxidized state of the ferrocene unit. Differential scanning calorimetry (DSC) data show a shift towards higher phase transition temperatures after oxidation, which is in agreement with the behaviour of classical ionomers. Small angle X‐ray scattering (SAXS) experiments show an excess scattering to small angles, which is a hint for dispersed particles in the polymer matrix (ionic clusters). In one polymer series the ferrocene content was varied. Increasing the ferrocene content changes the type of the LC phase from smectic A to nematic presumably because of the bulkiness of the neutral ferrocene group. It is, however, possible to restore the smectic A phase by an oxidation of the ferrocene units to ferrocenium ions. This is a result of microphase separation in ionic domains and non‐ionic domains, which supports the formation of layered structures.
Studies of lyotropic liquid crystalline mesophases of some novel regioselective substituted cellulose derivatives, 2. Structural and optical properties
Authors: Derleth Christina , Zugenmaier Peter
Published: April 2003

Regioselective substituted cellulose phenyl urethanes form lyotropic liquid crystalline mesophases in highly concentrated solutions with certain solvents. The structural and optical properties strongly depend on the site of substitution, e.g., 2‐, 3‐, 6‐position of the glucose residues as well as on the specific substitution of the phenyl ring of the carbamate group by fluorine, chlorine or methyl as compared to hydrogen and on the external parameters as concentration and temperature. By variation of the carbamate side groups a change of the helicoidal twist sense of the cholesteric structure is achieved leading to a compensation of left‐ and right‐handed twists that is to a quasi‐nematic structure. The experimental optical rotatory power can be described following theoretical considerations of de Vries by introducing a dispersion and a damping term.
Investigation of the initiation reaction of isoprene polymerization with 2‐ethylhexylsodium in heptane
Authors: Pakuro Natalia I. , Arest‐Yakubovich Alexander A. , Shcheglova Larisa V.
Published: April 2003

The kinetics of the initiation of isoprene polymerization in heptane with the hydrocarbon‐soluble alkylsodium compound 2‐ethylhexylsodium was studied. Initiation rates were estimated from the induction period and by measuring UV spectra of polyisoprenyl‐sodium (λmax = 304 nm) during the course of polymerization. The initiation reaction is first order in initiator both in the course of the reaction and with respect to the starting concentration of the initiator. The same result is obtained when 2‐ethylhexyllithium is used. The initiation rate constants are: ki = 1,6 · 10−3 and 5,5 · 10−4 L/(mol · s) for sodium and lithium compounds at 26°C, respectively. Aggregated forms of organoalkali compounds are suggested to take part in the initiation reaction of isoprene polymerization.
Free radical polymerisation studies of 4‐substituted styrenes, 2. Termination and chain transfer in the polymerisation of styrene, 4‐methoxystyrene and 4‐methylstyrene
Authors: Berry Robert William Huxley , Ludlow Andrew John , Mazza Robert John
Published: April 2003

The bulk polymerisation of styrene, 4‐methoxystyrene and 4‐methylstyrene was investigated at 60°C using 2,2′‐azoisobutyronitrile (AIBN) as the initiator. Initial rates (Ri0) and efficiencies (f) of initiation were calculated from the radioactive content of the polymer obtained by labelling the initiator as either [methyl‐14C4]AIBN or [cyano‐14C2]AIBN. Rates of polymerisation determined gravimetrically are in good agreement with rates determined by the dilatometer technique. An empirical linear relationship between the number of initiator fragments and the degree of monomer conversion was noted. Factors affecting the termination of polymer radicals are discussed and compared with other published work. The polymerisation reaction is terminated predominantly by combination in the case of all three monomers, and chain transfer constants to initiator and to monomer are of the order of 10−3 and 10−5, respectively.
New comblike copolymers of controlled structure and dimensions obtained by grafting by polystyryllithium onto poly(chloroethyl vinyl ether) chains
Authors: Schappacher Michel , Deffieux Alain
Published: April 2003

The grafting reaction of polystyrene branches onto poly(chloroethyl vinyl ether) (PCEVE) chains, based on the deactivation of polystyryl (PS) carbanionic ends onto chloroethyl ether functions has been investigated. The selectivity of the coupling is very high and allows the almost complete substitution of the chloride group of the CEVE units by PS chains with molar masses up to 15 000. The main side reaction observed is the deactivation of some PS chains, at the very beginning of the reaction. It is attributed mainly to impurities present in the PCEVE solution. Since the PCEVE polymer backbone and the PS grafts can be prepared by both living cationic and anionic polymerization, it is possible to synthesize poly(CEVE‐g‐styrene) copolymers possessing both a backbone with controlled dimensions and an adjustable number of branches having precise length and narrow molar mass distribution. The synthesis and the characteristics of comblike poly[(chloroethyl vinyl ether)‐g‐styrene]s are described.
Photochemical reactions of polystyrenes ring‐substituted with thiocyanato groups
Authors: Kern Wolfgang , Hobisch Josefine , Hummel Klaus
Published: April 2003

The photochemistry of poly(2‐vinylphenyl thiocyanate) (P(2‐VPT)), poly(3‐vinylphenyl thiocyanate) (P(3‐VPT)) and poly(4‐vinylphenyl thiocyanate) (P(4‐VPT)) is investigated under 254 nm UV light. Poly(4‐bromostyrene) (P(4‐BrSt)) is used as reference material. Experiments with phenyl thiocyanate show that the main photoreaction is a cleavage into cyano and phenylthio radicals which also occurs in the polymers. Photo‐crosslinking data for the polymers P(2‐VPT), P(3‐VPT) and P(4‐VPT) are evaluated with the Charlesby‐Pinner relation. For P(2‐VPT), P(3‐VPT) and P(4‐VPT) the qunatum efficiencies ΦCL of crosslinking are 0.018, 0.029 and 0.021, the quantum efficiencies ΦCL of chain scission are 9 · 10−4, 37 · 10−4 and 6 · 10−4. P(2‐VPT), P(3‐VPT) and P(4‐VPT) rank among the most sensitive negative resists in the polystyrene series. Hammett's σ constants for SCN substituents are determined (3‐SCN: σ = 0.50, 4‐SCN: σ = 0.45). However, a general correlation between the ΦCL or ΦCS values of ring‐substituted polystyrenes and Hammett's σ constants of the substituents is not found.
Atomic force microscopy of the banded structure of lyotropic polymers
Authors: Fischer Hartmut , Miles Mervyn J. , Odell Jeffrey A.
Published: April 2003

No Abtract.
Enantioselective isotactic alternating copolymerization of styrene and 4‐methylstyrene with carbon monoxide catalyzed by a cationic bioxazoline pd(II) complex
Authors: Bartolini Stefano , Carfagna Carla , Musco Alfredo
Published: April 2003

The cationic bioxazoline Pd(II) complex 2 catalyzes the alternating copolymerization of carbon monoxide with styrene and 4‐methylstyrene, respectively, to yield a highly isotactic optically active polymer at room temperature and low carbon monoxide pressure (1–4 atm).
Length of chain segment motion needed for crystallization
Authors: Qian Renyuan , Wu Zhicai , Xue Zhaohong , Yan Ruifang
Published: April 2003

The length of chain segment motion needed for the crystallization of guttapercha from rubbery state was found to be around 180 CC bonds of the backbone chain. Thus, the crystallization process from the rubbery state or from the melt is not through chain folding, and the solidification model is a more appropriate physical picture of the process.
Polymerization of acetylenes carrying precursors of aminyl radicals
Authors: Dulog Lothar , Bognar Peter
Published: April 2003

In the search for organic ferromagnets polymers with a conjugated backbone and pendant persistent radicals are one route of interest. The synthesis of poly[4‐(4‐ethynylphenyl)‐2′,4′,6′‐trinitro‐2,6‐diphenyldiphenylamine] (p‐3) and poly[4‐(3‐ethynylphenyl)‐2′,4′,6′‐trinitro‐2,6‐diphenyldiphenylamine] (m‐3) as precursors of polyradicals are described. A dinuclear rhodium cyclooctadiene chloride complex as polymerization catalyst was used to yield polymers with molecular weights (gel‐permeation chromatography) of 100 000 for m‐3 and 210 000 for p‐3.
Miscibility of poly(vinyl chloride) with chitin derivatives having poly(2‐methyl‐2‐oxazoline) side chains
Authors: Aoi Keigo , Takasu Akinori , Okada Masahiko
Published: April 2003

Binary blends of poly(vinyl chloride) (PVC) and chitin‐graft‐poly(2‐methyl‐2‐oxazoline) showed miscibility in the blend fraction range of the latter lower than ca. 10 wt.‐%. The glass transition temperature of PVC, which was determined by differential scanning calorimetry, changed to lower temperatures with increasing modified chitin contents up to 10 wt.‐%. Segmental interaction between PVC and the graft copolymer was confirmed by the carbonyl stretching band shift in the FT‐IR analysis.
Synthesis of novel functional poly[(R,S)‐ß‐hydroxybutyrate] containing phosphonoacetate end groups
Authors: Jedliński Zbigniew , Adamus Grazyna , Kowalczuk Marek
Published: April 2003

Amorphous poly[(R,S)‐ß‐hydroxybutyrate], containing both phosphonoacetate and carboxylate functional end groups, was synthesized via anionic polymerization of racemic ß‐butyro‐lactone initiated by supramolecular complexes of potassium P,P‐dimethylphosphonoacetate. The living homopolymers, with alkali metal counter ions complexed with a crown ether, were utilized for the synthesis of block copolymers via condensation reaction with alkylene dihalides. As a result of this approach, coupled block copolymers containing phosphonoacetate functional end groups were obtained.
Reaction behaviour of monomeric β‐ketoesters, 4. Polymer network formation by Michael reaction of multifunctional acetoacetates with multifunctional acrylates
Authors: Moszner Norbert , Rheinberger Volker
Published: April 2003

Based on the Michael reaction of multifunctional acetoacetates with multiacrylates, in the presence or absence of dimethacrylates, tailor made matrix materials can be prepared. This can be achieved in a one‐ or two‐step process. The Michael addition (first step) can be followed by radiation curing of excessive acrylate (second step).
Solution‐grown crystal of poly[bis(4‐isopropylphenoxy)phosphazene]
Authors: Nakamura Hitoshi , Miyata Tadakazu , Yonetake Koichiro , Masuko Toru , Kojima Morio
Published: April 2003

The structural features of poly[bis(4‐isopropylphenoxy)phosphazene] (PB(4‐ip)PP) have been studied by electron microscopy, X‐ray diffraction and differential scanning calorimetry techniques. Its orthorhombic lattice constants are determined as follows: a = 3,14 nm, b = 1,14 nm, c = 0,992 nm. The space group of this polymer is suggested to be P 212121–D, and the molecular conformation of the chains possibly to be (trans3cis)2. This polymer exhibits a crystal/crystal transition at 86°C below its T(1) transition (120°C). The thermal behavior is similar to the characteristics of poly[bis(p‐methoxyphenoxy)phosphazene].
Solvent effects in copolymerization
Authors: O'Driscoll Kenneth F. , Davis Thomas P. , Klumperman Bert , Madruga Enrique L.
Published: April 2003

Extension of the Mayo‐Lewis Model of copolymerization concerning solvent effects in free‐radical polymerization is discussed on the basis of the bootstrap and penultimate unit effects.
Olefin polymerization with titanium tetrachloride catalysts supported on surface‐modified silica
Authors: Lee Dong‐ho , Yoon Keun‐byoung , Kang Kyung‐seok
Published: April 2003

After modification of silica with benzoyl chloride (BC) to obtain BC‐modified SiO2 (BC‐SiO2), BC‐SiO2/TiCl4 and BC‐SiO2/BEM/TiCl4 catalysts were prepared by treating the BC‐SiO2 with TiCl4 directly or with butylethylmagnesium (BEM) followed by TiCl4, respectively. During the modification, BC reacts with hydroxyl groups of silica. In this way the corresponding ester is anchored on the silica surface and the CO group is coordinated with Ti and/or Mg. In addition, BEM is converted to MgCl2 in the reaction with TiCl4. These catalysts have reasonable activities for ethylene or propene polymerization.
Synthesis and characterization of polyurethanes containing cholesterol and phosphatidylcholine analogous moieties
Authors: Li Yujun , Shibata Yoshitomo , Nakaya Tadao
Published: April 2003

Several new polyurethanes containing cholesterol and phosphatidylcholine analogous moieties were synthesized by addition polymerization of 2‐[bis(2‐hydroxyethyl)methylammonio]ethyl 5‐cholesten‐3β‐yl phosphate (2) with diisocyanates such as hexamethylene diisocyanate (HDI), 2,4‐tolylene diisocyanate (TDI), 4,4′‐methylenediphenyl diisocyanate (MDI) and m‐xylylene diisocyanate (XDI), respectively. They were characterized by their IR and 1H NMR spectral data and elemental analyses. Preliminary studies suggest that these polyurethanes show the viscosity behavior of common polyelectrolytes.
Enzymes in polymer chemistry, 8 Chemoenzymatic synthesis of polymerizable 11‐methacryloyl‐aminoundecanoic ester of 1‐ and 3‐O‐methyl‐α‐D‐glucose in 6‐O‐position
Authors: Geyer Ulrike , Klemm Dieter , Pavel Konstantin , Ritter Helmut
Published: April 2003

The paper describes the regioselective esterification of a glucopyranoside and glucose derivative with 11‐methacryloylaminoundecanoic acid in the presence of a lipase from Candida antarctica. The obtained modified sugar derivatives 6‐O‐(11‐methacryloylaminoundecanoyl)‐1‐O‐methyl‐α‐D‐glucopyranoside (3 a) and 6‐O‐(11‐methacryloylaminoundecanoyl)‐3‐O‐methyl‐α‐D‐glucopyranose (3 b) were polymerized radically with AIBN as initiator.
Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 2. Kinetic investigations with methyl methacrylate in toluene
Authors: Schlaad Helmut , Müller Axel H. E.
Published: April 2003

The kinetics of the polymerization of methyl methacrylate initiated by lithium alkyls (tert‐butyllithium or ethyl α‐lithiobutyrate) was investigated in the presence of aluminium alkyls (triethylaluminium or triisobutylaluminium) in toluene at −78°C. The rate of polymerization decreases considerably once the living dimer is formed. This suggests that the aluminate end‐group coordinates with the penultimate ester group of the polymer chain, thus decreasing reactivity. The results are at variance with an activated monomer mechanism.
Effect of photoinitiator on the molar mass distribution obtained from a pulsed laser polymerization
Authors: Bergert Ute , Beuermann Sabine , Buback Michael , Kurz Caroline H. , Russell Gregory T. , Schmaltz Claudia
Published: April 2003

The choice of the photoinitiator is not usually regarded as being as important consideration in attempting to determine the value of the propagation rate coefficient kp from a pulsed laser‐initiated polymerization (PLP). It is shown that in fact the choice of the photoinitiator can profoundly influence the success of such experiments. Specially, for a number of monomers it was found that the successful determination of kp is essentially impossible when 1,1‐azodicyclohexanecarbonitrile is employed as a photoinitiator. The likely reason for this phenomenon is discussed from which it would seem appropriate to be wary in using any azo compound as a PLP photoinitiator. From PLP experiments with a non‐azo photoinitiator, ambient pressure kp has been determined for bulk polymerization of methyl methacrylate over an extended temperature range.
On the explanation of the biphotonic processes in polyesters containing azobenzene moieties in the side chain
Authors: Ramanujam P. S. , Hvilsted Søren , Zebger Ingo , Siesler Heinz W.
Published: April 2003

An explanation for the recently observed biphotonic transitions in side‐chain polyesters with azobenzene moieties is given on the basis of experimental observations from optical and Fourier‐Transform infrared absorption spectra. We present for the first time experimental evidence that a red laser beam at 633 nm causes cis‐trans (Z—E) transitions in azobenzene.
Synthesis and properties of poly(arylene ether sulfone)s and poly(arylene ether ketones) derived from 4,4″‐dihydroxy‐o‐terphenyl
Authors: Akutsu Fumihiko , Takahashi Kenichi , Kasashima Yoshio , Inoki Mari , Naruchi Kiyoshi
Published: April 2003

Novel poly(arylene ether)s with a rigid and zigzag 4,4″‐o‐terphenyldiyl structure, introduced into the polymer backbone were synthesized by nucleophilic displacement reaction of 4,4″‐dihydroxy‐o‐terphenyl with several activated aromatic dihalides in virtually quantitative yields. The poly(arylene ether)s having high molecular weight show both good solubility in common organic solvents and high thermal stability up to 545°C. They are amorphous with glass transition temperatures of 160–200°C.
Substituent effect in anionic polymerization of β‐lactones initiated by alkali metal alkoxides
Authors: Kurcok Piotr , Matuszowicz Andrzej , Jedliński Zbigniew , Kricheldorf Hans R. , Dubois Philippe , Jérôme Robert
Published: April 2003

The influence of methyl substituent on the mechanism of the ring‐opening polymerization of β‐lactones initiated by alkali metal alkoxides is discussed. Attention has been paid to the effect of the substituent position in the monomer molecule on the ring‐opening mechanism, the 3,3‐dimethyl‐2‐oxetanone (pivalolactone), 4‐methyl‐2‐oxetanone (β‐butyrolactone) and 2‐oxetanone (β‐propiolactone) being chosen as model monomers. Moreover, it was found unexpectedly that in the case of pivalolactone polymerization, besides open‐chain polymers, cyclic oligomers are produced.
Mesophases involving highly ordered smectic phases in a polyether
Authors: Cheng Stephen Z. D. , Yoon Yeocheol , Zhang Anqiu , Savitski Edward P. , Park Jae‐Young , Percec Virgil , Chu Peihwei
Published: April 2003

Based on our differential scanning calorimetry observations, a polyether 1 synthesized from 4′‐[2‐(4‐hydroxyphenyl)propyl]‐4‐biphenylol and 1,9‐dibromononane shows multiple transition behavior during cooling and heating. Furthermore, these transition temperatures do not exhibit significant supercooling dependence. Detailed analyses of the wide‐angle X‐ray diffraction powder and fiber patterns at different temperatures have indicated that highly ordered smectic F and G phases exist in this polyether and are differentiated from traditional crystalline phases.
Synthesis and optical properties of some novel arylene‐alkynylene polymers
Authors: Mangel Timo , Eberhardt Anke , Scherf Ullrich , Bunz Uwe H. F. , Müllen Klaus
Published: April 2003

The synthesis and the optical properties of the novel aryleneethynylenes (7, 8) and arylenebutadiynylenes (10, 11) using either a Heck‐type or a Hay‐type coupling are reported. The route reported here also makes meta‐linked arylene‐alkynylenes accessible. The number‐average degree of polymerization of the obtained polymers is between 13 and 60. Some of the materials show promising optical properties (photoluminescence).
Cyclization reaction of polyacrylonitrile and poly(styrene‐co‐acrylonitrile) studied by PVT measurements
Authors: Kressler Jörg , Rudolf Bernd , Shimomai Ken , Ougizawa Toshiaki , Inoue Takashi
Published: April 2003

Pressure, volume, temperature (PVT) measurements reveal that during the intramolecular cyclization reaction of poly(acrylonitrile) (PAN) and poly(styrene‐co‐acrylonitrile) (SAN) the volume decreases. This volume contraction becomes smaller with increasing styrene content in the random copolymers and should be related to the simultaneous decrease of longer acrylonitrile homo‐sequences. The onset temperature of the cyclization reaction is raised with higher styrene contents in the random copolymers. Thus, it can be excluded that the cyclization reaction has a major influence on the discoloration process of SAN samples having relatively small acrylonitrile contents (less than 50 mol‐%) during thermal annealing below 300°C.