bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthèse d'un monomère styrénique à substituant phosphonique. Instabilité de la forme diacide et polymérisation
Authors: Boutevin Bernard , Hamoui Bachar , Bessière Jean‐marie M.
Published: April 2003

p‐Vinylbenzyphonic acid was prepared by means of the Arbuzov reaction between triethyl phosphite and p‐chloromethylstyrene followed by silylation with bromotrimethylsilane and methanolysis. The product, which is readily cross‐linked, is stabilized as dicyclohexycylammonium salt. Radical‐initiated polymerization occurs readily; homo‐ and copolymers found are slowly cross‐linked upon releasing dicyclohexylamine.
Variation of the propagation rate coefficient with pressure and temperature in the free‐radical bulk polymerization of styrene
Authors: Buback Michael , Kuchta Frank‐Dieter
Published: April 2003

The propagation rate coefficient Kp of the free‐radical bulk polymerization of styrene is determined between 30 and 90°C up to a maximum pressure of 2800 bar. The data from pulsedlaser polymerizations and product analyses by gel‐permeation chromatography (PLP‐GPC) are adequately represented by the expression:

The conseaquences of deducing activation volumes and activation energies from kp/(L · mol−1 · s−1) or fromk*p/(kg · mol‐1 ·. S−1) are outlined.
1,3‐Oxazoline intermediates in reactive processing applications, 1. Melt grafting of poly(ethene‐co‐methacrylic acid) with 2‐substituted 1,3‐oxazolines
Authors: Müller Philipp , Wörner Christof , Mülhaupt Rolf
Published: April 2003

A novel family of functional ethene copolymers with various side chains were prepared by melt grafting of poly(ethene‐co‐methacrylic acid), containing 3,00 and 4,25 mol‐% of methacrylic acid, with 2‐substituted 1,3‐oxazolines such as 2‐phenyl‐1,3‐oxazoline, 2‐undecyl‐1,3‐oxazoline, 2‐heptadecyl‐1,3‐oxazoline, and 4‐(1,3‐oxazolin‐2‐yl)phenyl 4‐methoxybenzoate. 1H NMR and FTIR studies of the polymer microstructures revealed that carboxylic acid groups reacted with 1,3‐oxazolines within few minutes to form esteramide‐coupled side chains in very high yields. Torque of the reaction mixture, mechanical and thermal properties of the graft copolymers were measured. In the case of 2‐heptadecyl‐esteramide‐substituted polyethenes, the side‐chain cocrystallization accounted for higher crystallinity of the resulting graft copolymers.
Synthesis and characterization of photosensitive 4,4′‐bis(dimethylamino)diphenylmethyl ethers of cellulose
Authors: Heinze Thomas , Erler Ulrich , Heinze Ute , Camacho Juan , Grummt Ulrich‐Walter , Klemm Dieter
Published: April 2003

Soluble 4,4′‐bis(dimethylamino)diphenylmethyl ethers of cellulose (2) with a degree of substitution from 0,5 to 1,0 were prepared by therification of cellulose dissolved in N,N‐dimethylacetamide/LiCl. These ethers 2 show typical absorption spectra with an absorption maximum at 265 nm. While in neutral and basic medium 2 are stable, under acidic conditions a significant cleavage of the ether bonds occurs and thereby the formation of Michler's hydrol blue (absorption maximum at 604 nm). 2 was found to be photoconducting as film cast from a N,N‐dimethylformamide solution, for instance. Preliminary studies of the behavior of solutions of 2 by irradiation by means of flash photolysis and UV spectroscopy were carried out as well.
Electrochemically mediated polymerization of 2‐pentadecylaniline confined to a planar liquid‐liquid interface
Authors: Sigmund Wolfgang M. , Child Andrew D. , Reynolds John R. , Duran Randolph S.
Published: April 2003

Spreading, isotherms and polymerization of 2‐pentadecylaniline at a planar aqueous electrolyte‐organic interface were examined by monitoring the interfacial pressure employing the Wilhelmy‐plate method. These results indicate the presence of monomer confined to the interface. Application of a voltage across the interface using stainless steel electrodes results in polymerization to form an electroactive polymer. The interfacial polymerization appears to be effected by metal ions formed by oxidation of the anode that have diffused into the aqueous electrolyte. This phenomenon is dependent on the nature of the electrode material as successful polymerization was not observed with other electrode materials. The polymer formed was soluble in polar organic liquids, was green in its reduced state and blue in its oxidized state, when oxidized and reduced chemically or electrochemically as a thin film. Cyclic voltammetry of the polymer indicates one reversible redox process suggesting that there are only two different oxidation states available, i.e., the equivalent to leucoemeraldine cannot be formed with poly(2‐pentadecylaniline) in a thin film. However, the fully reduced yellow leucoemeraldine can be formed in chloroform solution by hydrazine reduction.
Polymerization of methyl methacrylate with V(acac)3 and VOCl3 in combination with methylaluminoxane
Authors: Endo Kiyoshi , Inukai Akihiro , Otsu Takayuki
Published: April 2003

The polymerization of methyl methacrylate (MMA) with V(acac)3 and VOCl3 in combination with methylaluminoxane (MAO) was investigated. The obtained polymers have a relatively narrow molecular weight distribution (M̄w/M̄n < 1,5). It was found that the isotactic triad content of the polymers increases with increasing temperature and MAO/V and MAO/MMA mole ratios. The interaction between MMA and MAO has an influence on the tacticity of radically (initiator AIBN) obtained polymers: in presence of MAO the fraction of isotactic triads (mm) is higher. The catalytic activity of MAO‐containing catalysts (V(acac)3/MAO and VOCl3/MAO) was compared with that of AlEt3‐containing catalysts (V(acac)3/AlEt3 and VOCl3/AlEt3). It was not much different, but for MAO as cocatalyst the isotacticity of the resulting PMMA's was higher, and the polydispersity lower, than with AlEt3 as cocatalyst.
Binary blends of poly(ethylene terephthalate) with thermotropic liquid‐crystalline copolyesteres: Thermal, morphological and mechanical studies
Authors: El‐Amouri Issam , Skoulios Antoine , Quentin Jean‐Pierre
Published: April 2003

Binary mixtures of a thermoplastic engineering poly(ethylene terephthalate) (PETP) with a thermotropic liquid‐crystalline random copolyester (PCL) were prepared by melt blending the polymers in a screw extruder or by precipitating them from a solution in a common solvent. Differential scanning calorimetry and polarizing optical microscopy were used to study their thermal and morphological properties as a function of temperature and composition. At high temperature, the blends rich in PETP are isotropic liquids, those rich in PCL are nematic fluids, and those of intermediate compositions are formed of two phases in equilibrium, one liquid‐isotropic and one nematic. At low temperature, the blends are generally biphasic, with the two component polymers crystallized. The presence of crystallized PCL proved not to act as a nucleating agent towards the crystallization of PETP from the melt. A schematic phase diagram was drawn to summarize the thermal and morphological behaviour of the blends. Scanning electron microscopy studies of injection moulded samples revealed the presence of highly oriented fibrils when the composition exceeded roughly 50 wt.‐% in PCL. The bending elastic modulus of the injected blends with 75 wt.‐% of PCL surpasses that of the pure PCL, probably due to the presence of oriented high‐molecular‐weight PETP molecules. The particular dependence of the mechanical rigidity upon the concentration of PCL permits easily to determine conditions for the thermoforming of PETP.
On the time‐concentration superposition of the linear viscoelastic properties of plasticized polystyrene melts using the free volume concept
Authors: Schausberger Alois , Ahrer Iris V.
Published: April 2003

Plasticizing agents are known to shift the material functions of polymer melts like raised temperatures to shorter times and to higher frequencies. The influence of dioctyl sebacate, dioctyl phthalate and bibenzyl on the viscoelastic properties of polystyrene melts is sized by shift factors which can be evaluated very exactly from the dynamic moduli in the rubber‐like liquid region. Besides, these shift possibilities enable us to enlarge the experimental window to the low frequency region for some decades. The typical diluent effect caused by the additives is quite similar to the one caused by not entangled polymer molecules. The lowering of the plateau modulus, i. e., the shift on the modul axis, is found to be equal to the square of the weight fraction of the polymer. The reduction of the relaxation times, i. e., the shift on the time or frequency axis, mainly is due to the increased fraction of free volume accounted for by A/Mn,c, where A rates the fraction created by one mole additive and A/Mn,c is the number‐average of the molar masses of polymer and additive. The influence of the free volume on the relaxation times is calculated with the aid of a Doolittle equation. The Concentration dependence of the time‐temperature shift factors is also accounted for by A/Mn,c. Therefore, besides the parameter A, only the three parameters used in (and known by) the analysis of the time‐temperature superposition principle, i. e., the fraction of free volume of the pure polymer (f), the thermal expansion coefficient of f (αf) and the Doolittle parameter B, are needed for the calculation of the temperature‐dependent time‐concentration shift factors and of the concentration‐dependent time‐temperature shift factors as well.
Use of fluorescence to study inverse microemulsion polymerization of acrylamide
Authors: Lacík Igor , Bartoň Jaroslav , Warr Gregory G.
Published: April 2003

Steady‐state fluorescence was used to study the polymerization of acrylamide (AAM) in inverse microemulsions comprising water/bis(2‐(ethylhexyl)sodium) sulfosuccinate (AOT)/toluene in order to investigate the AAM depletion from various loci of microemulsion in the process of polymerization. AAM has the role of both reactive monomer and consurfactant in this microemulsion, and also acts as a quencher for the indole fluorescent probes: 1,2‐dimethylindole, indole and L‐tryptophan. These were selectively placed within various loci of the microemulsion (toluene, interphase and water phase), enabling us to follow the depletion of AAM by monitoring the fluorescence of each probe during polymerization. The obtained results show a monotonic decrease of the AAM concentration regardless of the probe localization in the microemulsion polymerization system.
Characterization of DEAE‐dextran by means of light scattering and combined size‐exclusion chromatography/low‐angle laser light scattering/viscometry
Authors: Hanselmann Ralf , Burchard Walther , Lemmes Rolf , Schwengers Dieter
Published: April 2003

Ten DEAE (2‐(diethylamino)ethyl) dextran samples were investigated by means of static and dynamic light scattering, viscometry and size‐exclusion chromatography (SEC) in combination with on‐line small‐angle laser light scattering (LALLS) and viscometry (VISC). In dilute solution the behavior of DEAE‐dextran was compared with that of unsubstituted dextran and the molecular weight M dependences of the radius of gyration Rg, hydrodynamic radius Rh, intrinsic viscosity [η], second virial coefficient A2 and z‐average diffusion coefficient Dz were determined. The relationships for DEAE‐dextran dissolved in a 0,8 molar sodium nitrate solution were nearly the same as for dextran dissolved in water with 0,05 wt.‐% sodium azide and gave the same exponents. The molecular weight dependence of the intrinsic viscosity cannot be described by a Kuhn‐Mark‐Houwink relationship with a constant exponent. The slope in the plot of log [η] versus log M decreases with increasing molecular weight which indicates the occurrence of branching. By means of SEC/LALLS/VISC measurements the molecular weight distributions were determined. The distributions were calculated (1) directly from the light scattering signal, (2) from a calibration line obtained by light scattering data of a DEAE‐dextran sample with a broad distribution and (3) from the intrinsic viscosity distribution obtained by the on‐line viscosity/refractive index detector in combination with the [η]‐M relationship. In order to get the correct molecular‐weight dependence of the intrinsic viscosity it is necessary to determine the molecular weight distribution directly by LALLS (technique 1) and to combine this with the appropriate intrinsic viscosity data from the viscometer. Only the third technique, which is an extension of technique 1, gave satisfactory results over the whole molecular weight region observed.
Functionalized initiators for group transfer and metal‐free anionic polymerization for the synthesis of macromonomers: overview and new results
Authors: Bandermann Friedhelm , Beckelmann Dirk , Broska Dirk , Fieberg Andreas , Roloff Thorsten , Wolters Dieter
Published: April 2003

Vinylphenyloxy‐ and allyloxy‐substituted silyl ketene acetals are presented as new functionalized initiators for group transfer polymerization (GTP). All initiators initiated GTP of butyl acrylate in tetrahydrofuran with tetrabutylammonium cyanide as catalyst to yield butyl acrylate macromonomers with number‐average molecular weights somewhat lower than those calculated for an ideal living polymerization and with polydispersities of about 1,8–2,6. For the metal‐free anionic polymerization, functionalized initiators were obtained introducing allyloxy and vinylbenzyl groups into tetrabutylammonium diethyl malonate. Both compounds initiated a very rapid polymerization of butyl acrylate in tetrahydrofuran with high monomer conversion. The number‐average molecular weights of the macromonomers, produced in a semi‐batch procedure, reached nearly theoretical values, the polydispersities were about 1,2. In all macromonomers the functionality with respect to terminal vinyl and allyl groups was near one, so that they can be used with other monomers to form graft copolymers, e. g., in a free‐radical polymerization.
Study of 1,4‐bis(propylaminomalonylamino)butane as a model compound for nylons n,3
Authors: Navarro Eloísa , Puiggalí Jordi , Subirana Juan A.
Published: April 2003

We are presently studying n,3 nylons, which have an unusual hydrogen bonding system. In order to determine their structure with greater precision, we have synthesized and determined by X‐ray diffraction the structure of a dimer of the repeating unit of nylon 4,3, namely, 1,4‐bis(propylaminomalonylamino)butane (pMBMp). This compound crystallizes in the triclinic system, space group P1 with a = 4,65, b = 4,91, c = 24,47 Å; α = 85,3, β = 89,7 and γ = 61,9°. The malonyl residues of pMBMp are related by an inversion center, with torsional angles about the methylene bonds of each malonyl residue in the range 110–115° (or the equivalent negative values). A. conformation TS̄(T)3ST was found for the butylenediamide unit. These results give support to the crystalline structure proposed for nylons n,3.
A novel synthesis and characterization of phenylacetylene end‐capped poly(aryl ether sulfone) and poly(aryl ether ketone) oligomers
Authors: Kozuch Mathew , Schaffer Angela , Bhatnagar Atul , Phulpagar Stanley , Mohanty Dillip K.
Published: April 2003

A series of controlled molecular weight poly(aryl ether sulfone) oligomers with benzophenone moieties at the chain termini were prepared. The two carbonyl groups at the chain ends were converted to ethynyl groups by using trimethylsilyldiazomethane/BuLi in tetrahydrofuran. Reactions of 4,4′‐isopropylidenediphenol with 4,4′‐difluorobenzophenone and 4‐fluorophenylphenylacetylene as the end‐capping reagent in N,N‐dimelthylacetamide afforded the desired poly(aryl ether ketone) oligomers Both sulfone and ketone containing oligomeric polyethers undergo crosslinking reactions at elevated temperatures.
Allyl reactivity in group transfer copolymerization
Authors: Öncül‐Koç Ayşegül , Catalgil‐Giz Huceste
Published: April 2003

Statistical copolymers of allyl methacrylates with methyl and ethyl methacrylates are synthesized. Moderate conversions are used. Reactivity ratios are calculated by linearised methods which take composition drift into account as well as by non‐linear least‐squares approximation. For the allyl methacrylate/methyl methacrylate system, rallyl values obtained by various methods are between 1,62 and 1,60 and rmethyl values between 0,36 and 0,34. For the allyl methacrylate/ethyl methacrylate system, rallyl values are between 1,37 and 1,16 and rethyl values between 0,40 and 0,47.
Synthesis and characterization of novel side‐chain liquid crystalline polycarbonates, 2. Polycondensation of mesogenic diols and diphosgene
Authors: Jansen John , den Ridder Patrick , Addink Rudolf , Mijs Wim
Published: April 2003

A series of new side‐chain liquid crystalline polymers was prepared with a polycarbonate backbone, bearing (E)‐4′‐nitrostilbene mesogenic groups, connected to the backbone by spacers of different length. The polymers were synthesized in 1,4‐dioxane by polycondensation of diphosgene and diol monomers with the general structure 2‐[ω‐(4′‐nitrostilben‐4‐ylcxy)alkyloxy]‐1,3‐propanediol in the presence of pyridine as a proton trap and catalyst. The mesomorphic properties of all monomers, polymers and intermediates were studied by polarized optical microscopy and differential scanning calorimetry (DSC). The polymers were also studied by X‐ray diffraction of non‐oriented and oriented samples (fibres). All monomers were liquid crystalline with nematic and/or smectic phases. For the polymers a clear relation was found between spacer length and glass transition temperature (Tg), which decreases with increasing spacer length and between spacer length and clearing temperature, which increases with increasing spacer length. X‐ray diffraction measurements indicated the presence of a smectic A double layer structure (SAd) for all polymers at room temperature, with an antiparallel of overlapping mesogenic groups. A distinct difference in the orientation of the mesogens was found when fibres were drawn from the smectic phase or from the nematic or isotropic phase. In the first case the mesogenic groups were oriented perpendicular to the fibre axis and in the second case the mesogenic groups were oriented parallel to the fibre axis. By gel‐permeation chromatography (GPC) measurements of heated samples and by thermogravimetric analysis (TGA) and DSC the polymers were found to be thermally stable up to temperatures well above their clearing point.
NMR study of miscibility and morphology of polyimide/polyimide blends
Authors: Feng Hanqiao , Ye Chaochui , Zhang Ping , Sun Zhenhua , Feng Zhiliu
Published: April 2003

The miscibility and morphology of polyimide/polyimide blends, PEI‐E/PTI‐E

PEI‐E: poly(ether imide‐ether), PTI‐E: poly(thioetherimide‐ether), PBPI‐E: poly(biphthalimide‐ether); cf. exptl. part.

and PBPI‐E/PTI‐E, have been studied by means of 13C CPMAS NMR technique. The results indicate that PEI‐E/PTI‐E blends are miscible on a molecular level, but molecular aggregation exists in pure PBPI‐E specimen as well as PBPI‐E/PTI‐E blends with high content of PBPI‐E, which vanishes in the blends with high content of PTI‐E. When the content of PBPI‐E is higher than that of PTI‐E, the addition of PTI‐E to PBPI‐E has almost no effect on the size of the PBPI‐E rigid domains, but has a large effect on the populations of the PBPI‐E rigid domains. It is the intermolecular charge‐transfer interaction that plays a critical role in the miscibility of PEI‐E/PTI‐E and PBPI‐E/PTI‐E blends.
Preparation, properties and complex formation ability of poly(ether‐ester)s of poly(ethylene glycol)s and 2,6‐pyridinedicarboxylic acid
Authors: Ignatova Milena , Manolova Nevena , Rashkov Iliya , Sepulchre Maurice , Spassky Nicolas
Published: April 2003

Poly(ether‐ester)s of poly(ethylene glycol)s (PEGs) and 2,6‐pyridinedicarboxylic acid (PDA) were synthesized by polycondensation of PDA and PEG in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine and by polycondensation of acyl chloride of PDA and PEG in the presence of triethylamine at 45°C. The polymers were characterized by GPC, UV, IR and 1H and 13C NMR spectroscopy. The complex formation between poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMA) and the poly(ether‐ester)s was studied. It occurs below the critical polyether chain length necessary for complex formation because of the stabilizing effect of the PDA hydrophobic residues.
Optically active polymers bearing side‐chain photochromic moieties: synthesis and chiroptical properties of methacrylic and acrylic homopolymers with pendant L‐lactic acid or L‐alanine residues connected to trans‐4‐aminoazobenzene
Authors: Angiolini Luigi , Caretti Daniele , Carlini Carlo , Salatelli Elisabetta
Published: April 2003

Novel optically active monomers such as trans‐(S)‐4‐(2‐methacryloylaminopropano‐ylamino)azobenzene, trans‐(S)‐4‐(2‐methacryloyloxypropanoylamino)azobenzene, and trans‐(S)‐4‐(2‐acryloylaminopropanoylamino)azobenzene have been prepared and homopolymerized by free radical initiation. Circular dichroism spectra of the resulting polymeric systems, as compared with those obtained for the corresponding low molecular weight analogues, purposely synthesized, allow one to suggest that the macromolecules assume in solution conformations with different homogeneity and prevailing chirality, depending on their structural requirements and solvent interactions.
Synthesis and characterization of isotactic cis‐1,4‐poly(3‐methyl‐1,3‐pentadiene)
Authors: Ricci Giovanni , Zetta Lucia , Porri Lido , Meille Stefano Valdo
Published: April 2003

3‐Methyl‐1,3‐pentadiene has been polymerized with the Al(C2H5)2Cl/Nd(OCOC7H15)3/Al[CH2CH(CH3)2]3 system to crystalline polymers consisting essentially of cis‐1,4 units (≥80%). NMR examination has shown that the polymers have an isotactic structure. This conclusion was confirmed by X‐ray analyses, which further indicated that cis‐1,4 isotactic poly(3‐methyl‐1,3‐pentadiene) exists in polymorphic modifications.
Structural changes induced by thermal treatments on emptied and filled clathrates of syndiotactic polystyrene
Authors: Manfredi Carla , De Rosa Claudio , Guerra Gaetano , Rapacciuolo Mariateresa , Auriemma Finizia , Corradini Paolo
Published: April 2003

The solvent molecules included in the clathrates (δ‐form) of syndiotactic polystyrene (s‐PS) are removed by suitable extraction procedures. An emptied δ‐form is produced which is different from the known γ‐form obtained by heating. The structural changes induced by thermal treatments on emptied and filled clathrates of s‐PS, have been followed by thermogravimetry, X‐ray diffraction analysis, differential scanning calorimetry and Fourier‐transform infrared spectroscopy. It is shown that, under suitable conditions, the emptied clathrates can be transformed into a mesomorphic form, which retains the chains in the helical conformation. This “helical” mesomorphic form, different from the previously known “planar” mesomorphic form, crystallizes by thermal treatments into the “helical” crystalline γ‐form.
Equation‐of‐state parameters of poly(vinyl acetate) as function of molecular weight
Authors: Casarino P. , Brunacci A. , Pedemonte E.
Published: April 2003

Specific volume, thermal expansion coefficient and thermal pressure coefficient are measured for poly(vinyl acetate) of different molecular weights. From these data the Flory equation‐of‐state characteristic parameters v*, T* and p* are determined. Comments on theoretical expectations and experimental behaviour are made.
Untersuchungen zur irreversibilität von Netzwerkentschlaufungen beim Fließen von Polymerschmelzen
Authors: Ehrecke Petra , Wagner Manfred H.
Published: April 2003

Experimental and theoretical investigations of stress relaxation after “double‐step” shear experiments lead to a better understanding of the irreversibility assumption of polymer melts. Here we compare measurements of shear stress relaxation for a branched polyethylene and a (linear) polyisobutene melt to theoretical predictions of Wagner's first and second equation and to a molecular theory of Doi. None of these theories is able to describe all the results of the measurements. These investigations demonstrate, however, what types of “double‐step” shear experiments are most sensitive to the irreversible disentanglement of polymer melts.
Study of the propagation centre in the anionic polymerization of (meth)acrylic monomers, 5. Nuclear magnetic resonance study of the model dimer in tetrahydrofuran
Authors: Kříž Jaroslav , Dybal Jiří , Lochmann Lubomír , Janata Miroslav , Vlček Petr
Published: April 2003

Di‐tert‐butyl 2‐lithio‐2,4,4‐trimethylglutarate (1) as a model of the living dimer of tert‐butyl methacrylate was studied in deuterated tetrahydrofuran (THF‐d8) solution by 6Li, 7Li, 1H and 13C NMR. In agreement with earlier observations from infrared spectroscopy and with quantum chemical ab initio and semiempirical self‐consistent field calculations, 1 is shown to have a strong tendency to an intramolecular coordination of Li to the penultimate ester carbonyl group. The competing linear form of 1 (with uncoordinated penultimate ester group) is shown to exist due to its stabilization by self‐aggregation to form a dimer of 1. In contrast to the monomeric form of 1, the dimer does not bind THF into a specific solvate. Given the entropy‐driven solvation at low temperatures, the occurrence of the dimeric aggregate is enhanced by higher temperature and concentration of 1. Both the cyclic and linear form of 1 are shown to exist in at least two different conformers and various solvation states. Their mutual exchange is several orders of magnitude slower than the anionic propagation reaction of tert‐butyl methacrylate.
Synthesis and properties of polyamides and poly(amideimide)s based on 4,4′‐[1,4(or 1,3)‐phenylenebis(isopropylidene‐1,4‐phenyleneoxy)]dianiline
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Fan Jr‐Chen
Published: April 2003

The diamines 4,4′‐[1,4(or 1,3)‐phenylenebis(isopropylidene‐1,4‐phenyleneoxy)]dianiline (p‐3 and m‐3) were synthesized in two steps from the condensation of 4,4′‐[1,4(or 1,3)‐phenylenediisopropylidene]diphenol (p‐1 and m‐1) and p‐chloronitrobenzene in the presence of K2CO3 in N,N‐dimethylformamide (DMF), giving the corresponding bis(4‐nitrophenoxy) compounds, followed by reduction with the hydrazine/Pd‐C system. A series of aromatic polyamides, aliphatic‐aromatic polyamides, and poly(amide‐imide)s were prepared by the direct polycondensation of the diamines with aromatic or aliphatic dicarboxylic acids and phthalimide unit‐bearing dicarboxylic acids in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. In addition, two series of polyamides were prepared from terephthalic acid or isophthalic acid and aromatic diamines with isopropylidene and/or ether linking groups between the phenylene units, and the structure‐property relationships of these polyamides were studied. Almost all the resultant polymers were amorphous in nature and could be solution‐cast into transparent, tough, and flexible films. Most of the polymers exhibited moderately high thermal stability. Thus, they are considered as new candidates for processable high‐performance polymeric materials.
A study of the thermal degradation of poly(mono‐n‐alkyl itaconates)
Authors: Velada José L. , Cesteros Carlos , Madoz Ana , Katime Issa
Published: April 2003

The thermal degradation of the first six members of poly(mono‐n‐alkyl itaconates) by thermogravimetry (TG), differential scanning calorimetry (DSC), Fourier Transform infrared (FTIR) and FTIR evolved gas analysis (FTIR‐EGA) was studied. The degradation mechanism involves cyclic anhydride formation followed by crosslinking due to the linear anhydride formation. In both processes water and/or alcohol evolution was detected. Also, decarboxylation processes take place on all polymers at high temperatures ( > 180°C). A mechanism of the degradation process is proposed.
Synthesis and liquid crystalline properties of azobenzene‐containing poly(vinyl ether)s with narrow molar mass distribution
Authors: Chiellini Emo , Galli Giancarlo , Bignozzi Maria Chiara , Angeloni Sante A. , Fagnani Marco , Laus Michele
Published: April 2003

A series of new liquid crystalline (LC) poly(vinyl ether)s with different molar masses was synthesized via a two‐step procedure involving the preparation of functional matrices by living cationic polymerization of an ω‐chloroalkyl vinyl ether monomer followed by a grafting reaction of an azobenzene mesogenic unit onto them. By appropriately adjusting the experimental conditions, it was possible to predetermine the molar mass characteristics of the LC polymers. Each of the parent and modified poly(vinyl ether)s had a narrow molar mass distribution. The LC polymers were semicrystalline and formed a nematic mesophase, enantiotropic or monotropic in character. The transition temperatures increased with increasing molar mass up to a limiting value and then remained nearly constant. Accordingly, poly(vinyl ether)s with predetermined molar mass and narrow molar mass distribution could be prepared.
Dipolar correlation and activation energies for the subglass relaxations of chains with asymmetric side groups
Authors: Díaz‐Calleja Ricardo , Riande Evaristo
Published: April 2003

The effect of the location of the halogen atom on the distribution of activation energies associated with the subglass relaxation of poly(o‐chlorophenyl acrylate) (POCPA) and poly(m‐chlorophenyl acrylate) (PMCPA) is studied. Poly(p‐chlorophenyl acrylate) (PPCPA) was also investigated, though not in depth due to its low dielectric activity. The high temperature and frequency dependence found for the activation energy on the high temperature side of the subglass relaxations may not correspond only to simple mechanisms associated with the ß‐process but also to more complex mechanisms associated with the glass‐rubber relaxation. Dielectric activity arising from motions about OCar bonds is responsible for the high dielectric strength exhibited by these polymers. Theoretical calculations based on the rotational isomeric state model are in fair agreement with the experimental relaxation strengths.
Synthesis of oligo[2]catenanes
Authors: Geerts Yves , Muscat Dirk , Müllen Klaus
Published: April 2003

Two new difunctionalised [2]catenanes 5 b, c have been synthesised. Oligomers 10 c, d containing interlocked rings in the main chain were prepared via Pd° coupling of 5 b with comonomers 9 c, d and degrees of polymerization of up to 8 have been reached. These materials were characterized by 1H NMR spectroscopy, fast atom bombardment‐mass spectroscopy, gel‐permeation chromatography and differential scanning calorimetry.
The curing reaction of poly(ether‐sulfone)‐modified epoxy resin
Authors: Chen Yung‐Sin , Lee Jun‐Shen , Yu Tzyy‐Lung , Chen John‐Chang , Chen Wen‐Yih , Cheng Min‐Chin
Published: April 2003

One of the useful methods to improve the toughness of epoxy resin is by mixing the resin with poly(ether‐sulfone) (PES). In the present work, two hydroxyl‐terminated PESs with molecular weights Mn = 28 600 and 4 200 were used for blending with epoxy resin. The curing reaction of diglycidyl ether/bisphenol‐A (DGEBA) with 4,4′‐diaminodiphenyl sulfone (DDS) in the presence of hydroxyl‐terminated PES was studied by means of differential scanning calorimetry (DSC) and gel‐permeation chromatography (GPC). For the DGEBA‐DDS‐PES system with a stoichiometric ratio of epoxy and amino groups the DSC experimental results showed that at a fixed molecular weight of PES the curing reaction rate decreases with increasing PES concentration. At a fixed PES concentration (in the range of between 0 and 20 wt.‐% of PES), the DGEBA‐DDS system modified with hydroxyl‐terminated PES with lower molecular weight had a faster curing reaction rate at low conversion and a slower curing reaction rate at high conversion. The GPC results showed the evidence of etherification between low‐molecular‐weight PES with epoxy resin. However, very little etherification of high‐molecular‐weight hydroxyl‐terminated PES with epoxy resin was found. Based on the experimental results, a curing reaction mechanism of DGEBA with DDS in the presence of hydroxyl‐terminated PES is proposed.
Thermodynamics of 2,2‐dimethyltrimethylene carbonate, of its bulk polymerization process and of poly(2,2‐dimethyltrimethylene carbonate) from 0 to 470 K at standard pressure
Authors: Lebedev Boris V. , Kulagina Tat'yana G. , Telnoy Vadim I. , Vasil'ev Valery G.
Published: April 2003

In the present work the thermodynamic properties of 2,2‐dimethyltrimethylene carbonate (DTC) and poly‐2,2‐dimethyltrimethylene carbonate (PDTC) were studied by precise calorimetry. In adiabatic and dynamic vacuum calorimeters the temperature dependence of the heat capacity of DTC and PDTC was studied between 5 and 470 K. Temperature and enthalpies of physical transitions were determined, and in an isothermal calorimeter energies of combustion of the above compounds were measured. From the results the thermodynamic functionsC(T),H°(T)–H°(0),S°(T),G°(T)–H°(0) were calculated for various physical states of the monomer and the polymer from 0 to 470 K. The standard enthalpies of combustion and thermochemical parameters of formation ΔH, ΔS, ΔGof the objects studied were estimated atT=298,15 K andp= 101,325 kPa. The zero entropyS(0) and configurational entropySof PDTC in the glassy state and the difference in zero enthalpies of the polymer in the glassy and crystalline statesH(0)–H(0) were estimated. The results were used to calculate the thermodynamic parameters of the bulk polymerization of DTC (ΔH, ΔS, ΔG) in the range of 0 to 420 K. It was established that for the process DTC → PDTC, ΔG< 0 if the polymer is crystalline and ΔG> 0 in the case of amorphous PDTC (glassy or liquid). The ceiling temperature isT= 500 K.
Side chain liquid crystal polymers of 2,3‐disubstituted norbornenes via ring‐opening metathesis polymerization, 1 influence of flexible spacer length m = 2 to 12 on the thermotropic behaviour
Authors: Ungerank Markus , Winkler Berthold , Eder Elisabeth , Stelzer Franz
Published: April 2003

Bis[(4′‐cyanobiphenyl‐4‐yl)oxy‐n‐alkyl]norborn‐5‐ene‐2,3‐dicarboxylates with alkyl chain lengths m = 2 – 12 were synthesized. Most of the monomers exhibit thermodynamically metastable liquid crystalline phases with respect to the crystalline phases. Polymers were prepared by ring‐opening metathesis polymerization (ROMP) using the molybdenum carbene initiator [Mo(CH‐t‐Bu) (NAr) (t‐BuO)2] (t‐Bu = tert‐butyl) with NAr = 2,6‐diisopropylaniline. All polymers show thermotropic liquid crystalline phases. Results on characteristic phases and the influence of the number of methylene units m in the flexible spacer on the thermal behaviour (glass transition temperature, isotropization temperature, odd‐even effect, enthalpy change) of these new side chain liquid crystal polymers (SCLCP's) are given. They are compared to monosubstituted polynorbornene derivatives and to SCLCP's with other backbones.
Syntheses and characterization of poly(aminophenazines)
Authors: Premasiri Ajith H. , Euler William B.
Published: April 2003

The oxidative polymerization of o‐phenylenediamine was studied under a variety of conditions. At room temperature the reaction of o‐phenylenediamine with ammonium persulfate in HCl acid medium gives a dimer, 2,3‐diaminophenazine. The same reaction at 70°C results in a trimer with an open structure, [3‐amino‐2(3,4‐diaminophenylamino)]‐phenazine hydrochloride. At 118°C, the oxidative polymerization in glacial acetic acid medium gives poly(aminophenazine) acetate, analogous to polyaniline. However, either because of the atactic nature of the polymer and the consequences of this on the stability of charge carriers or because protonation occurs at localized amines, no electrical conductivity was found.
Diacetylene‐containing polymers, 8. Synthesis and characterization of novel high molecular weight diacetylene‐containing poly(ester‐co‐urethanes)
Authors: Fomine Sergei , Posada Imelda , Ogawa Takeshi
Published: April 2003

Novel high molecular weight diacetylene (DA) — containing polymers, poly{[bis(3‐butynyl) 3,5‐diynylene sebacate]‐co‐[bis(3‐butynyl) hexamethylenedicarbamate]}s, were synthesized and characterized. The copolymers were found to be semicrystalline and their degree of crystallinity went through a minimum due to a random composition of the copolymers. The copolymers containing less than 40 mol‐% of bis(3‐butynyl) hexamethylene‐dicarbamate (2) were found to be thermoplastic. The glass transition temperature of the copolymers tends to increase with increasing monomer 2 content. All the copolymers underwent topochemical cross‐polymerization on electron‐beam irradiation or heating in the solid state and the maximum of the visible absorption spectra of the cross‐polymerized copolymers showed a long wavelength shift with increasing monomer 2 content. Upon introduction of 10 mol‐% of the urethane monomer 2 the tensile strength of the copolymer increases from 250 MPa to 280 MPa.
New polyurethanes based on diphenylmethane diisocyanate and 1,4:3,6‐dianhydrosorbitol, 1. Model kinetic studies and characterization of the hard segment
Authors: Cognet‐Georjon Estelle , Méchin Françoise , Pascault Jean‐Pierre
Published: April 2003

1,4:3,6‐Dianhydrosorbitol (DAS) seems to be an interesting reagent for the synthesis of polyurethanes. In the present work, the kinetics of the reaction of DAS with a monoisocyanate (p‐tolyl isocyanate, p‐TI) and with a diisocyanate (4,4′‐diphenylmethane diisocyanate, MDI) were studied with the help of a chromatographic method (size exclusion chromatography, SEC). When the condensation reaction is performed in tetrahydrofuran (THF) solution, with dibutyltin dilaurate (SnDBDL) as catalyst, DAS exhibits two equireactive hydroxyl groups. The reaction rate can be well described by a second‐order equation modified to include catalysis by the formed urethane functions. MDI and DAS were then condensed using two different experimental procedures (bulk and solution polycondensation in THF, in the presence of SnDBDL), and the characteristics of the resulting polyurethanes were compared. Bulk polycondensation led to an amorphous polymer, whereas the polyurethane prepared in solution was semi‐crystalline. In both cases, we obtained a very high glass transition temperature ( ≈ 186°C). The synthesis of samples with various polymerization degrees gave a better understanding of the molecular weight distribution of segmented polyurethanes based on MDI and DAS.
New ferrocene‐containing copolyesters
Authors: Wilbert Götz , Wiesemann Amadeus , Zentel Rudolf
Published: April 2003

We have synthesized four new ferrocene monomers (three diols and one diester). The redox potential of these ferrocene derivatives varies between 0 mV and 230 mV due to different degrees of ring alkylation. Amorphous and liquid crystalline copolyesters were prepared with these monomers in the polymer main chain. Cyclovoltammetric measurements show that the redox potential of the ferrocene units is increased by about 40 mV upon polymer formation (esterification). Since the ester group is 4 to 6 σ‐bonds away from the ferrocene unit this increase is probably caused by some charge‐transfer interaction through space. First rheological measurements show an unusual rubber‐like behaviour of the ferrocene‐containing copolyesters.
Light scattering peaks from aqueous solutions of acrylamideacrylic acid copolymers
Authors: Boudenne Nawel , François Jeanne
Published: April 2003

Aqueous solutions of acrylamide‐acrylic acid copolymers of high molecular weight have been investigated by light scattering. It was shown that a scattering peak can be obtained if the samples used have been prepared by alcaline hydrolysis of polyacrylamide and if the solutions are filtered and sonicated. In the range of the lower concentrations, the position of this peak, q*, is found to vary with the polymer concentration C, as C1/3, and to be independent of the charge density. The addition of very small amounts of salt provokes the disappearance of the peak. A phase diagram (charge density versus concentration of the polymer) has been established. It shows that these experiments were carried out in a concentration range intermediate between the dilute and the semidilute regimes (transition regime). The experimental scaling laws however correspond to the theoretical predictions for the dilute regime. Moreover, the q* values are much lower than those calculated by the random phase approximation theories.
Copolymerization of ethylene with 1‐hexene and 1‐octene: correlation between type of catalyst and comonomer incorporated
Authors: Quijada Raul , Dupont Jairton , Miranda Márcia S. Lacerda , Scipioni Rosângela B. , Galland Griselda B.
Published: April 2003

The behaviour of catalytic systems based on zirconium compounds for the copolymerization of ethylene with 1‐hexene and 1‐octene is reported. The metallocenes (CH3)2SiCp2ZrCl2, Cp2ZrCl2 (Cp = η5‐cyclopentadienyl), C2H4[Ind]2ZrCl2 and (Ind = η5‐indenyl) were chosen for this study. The bridged catalysts, (CH3)2SiCp2ZrCl2 and C2H4[Ind]2ZrCl2, and the metallocene Cp2ZrCl2 showed similar catalytic activities for home‐ and copolymerization of ethylene with 1‐hexene. 13C NMR analysis showed that the composition of copolymerization products depends on the catalytic system, in other words, on the ligand structure of the transition metal. Copolymers obtained using the bridged catalysts have greater incorporation of comonomer. Thermal analysis and viscosity measurements demonstrated that an increase of the comonomer concentration reduces the melting point, the crystallinity and the molecular weight of the copolymer. Results from infrared spectroscopy showed that β‐elimination is one of the possible termination reactions. The monomer reactivity ratios r were determined for all catalytic systems using Fineman‐Ross and 13C NMR methods. The values of r1 (M1 = ethylene) and r2 (M2 = α‐olefin) showed an effect of the type of metallocene and of α‐olefin on the structure of the copolymer obtained.
Stereospecific polymerization of methylthiirane in homogeneous phase, 5. Study of the interconversion between active sites
Authors: Boucard Valérie , Dumas Philippe , Sigwalt Pierre
Published: April 2003

The enantioasymmetry of polymerization reactions of racemic methylthiirane in bulk are studied, initiation being made using racemic or optically active seeds of molar weight equal to 40000, synthesized in bulk from bis(isopropyl‐S‐cysteinato)cadmium. In these conditions, active sites are enantiomers and the enantioasymmetric constant kR, measuring the preferential choice of the R antipode, is depending only on the relative number of the two types of active sites. We have observed an interconversion between the enantiomeric active sites CR* and CS*. The ratio [CR*]/[CS*] is only varying with conversion and reaches a limiting value that depends on cadmium concentration. For low cadmium concentrations, ([CR*]/[CS*])lim = 1.00, showing a complete racemization of the enantiomeric active sites, while for higher cadmium concentrations, ([CR*]/[CS*])lim = 1.07 ± 0.03. This value of 1.07 can be attributed to the presence of aggregation of dimeric species which create a chiral neighbourhood around cadmium atoms. Diastereoisomeric active sites present when active sites are born by chains of lower molar weights seem also to interconvert. The interconversion between active sites implies the presence of stereoblocks in the main chain.
Electrochemical synthesis of titanium‐based Ziegler‐Natta catalysts and their potential application in ethylene homo‐ and copolymerization
Authors: Brusson Jean‐Michel , Mortreux André , Petit Francis , Bujadoux Karel , Leprevost Benoit
Published: April 2003

Highly active Ziegler‐Natta catalysts have been synthesized using an electrochemical process in their preparation, with the aim of producing selectively titanium(III) species from TiCl4. The use of an undivided cell, an aluminium anode and a halogenated solvent (dichloromethane or 1,2‐dichloroethane), has allowed the production in situ of chloroalkyl aluminium species, by cathodic reduction of TiCl4, thus giving rise to a new Ziegler‐Natta catalytic combination. The possibility of scale up for this lectrochemical synthesis has been clearly shown. The Ti/Al system was modified so as to enhance its activity, first by adding a soluble dialkylmagnesium compound and then a soluble vanadium compound such as VOCl3. This Ti/Al/Mg/V highly active system was used under different conditions: in a hydrocarbon medium at low (80°C) and high (200°C) temperature and also under supercritical conditions in a continuous high‐pressure autoclave reactor, to produce homoor copolymers of ethylene with α‐olefins. Compared to similar heterogeneous catalysts obtained by comilling, the observed activities are shown to be very much improved, especially under high pressure and high temperature conditions. This may be related to the very narrow granular distribution centered at 2,5‐3 μm, compared to a much broader distribution (centered at 6 μm) obtained with the comilled catalyst.
Thermal degradation of polymers in the melt, 1. Characterization of volatile oligomers formed by thermal degradation of polyisobutylene
Authors: Sawaguchi Takashi , Takesue Tomoyuki , Ikemura Tadashi , Seno Manabu
Published: April 2003

Chemical structures of a number of components of volatile oligomers including (n+2)‐mers (n ≧ 0) produced by thermal degradation of polyisobutylene were systematically determined by high‐resolution capillary gas chromatogaphy/mass spectrometry (GC/MS). The total ion current (TIC) chromatogram consists of about 100 peaks ranging from dimers (2‐mers, n = 0) to dodecamers (12‐mers, n = 10) and most of the main peaks are classified into four types of terminal monoolefins: a trisubstituted olefin with a tert‐butyl end, a vinylidene olefin with a tert‐butyl end, a trisubstituted olefin with an isopropyl end, and a vinylidene olefin with an isopropyl end. The formation of these monoolefins is reasonably interpreted by intramolecular hydrogen abstractions (back‐biting) of primary and tertiary terminal macroradicals and subsequent β; scissions at the inner position of the main chain. In all the chromatograms of each (n+2)‐mer (n ≧ 1), the retention times of terminal trisubstituted types of monoolefins were shorter than those of terminal vinylidene types of monoolefins, in contrast to the elution order of dimers. The relative intensities between the interesting peaks of each (n+2)‐mer (n ≧ 1) clearly represent that back‐biting more predominantly occurs at the methylene hydrogen rather than at the methyl group consistent with the difference in the bond dissociation energy of the HC bond of interest, as opposed to the steric hindrance mechanism5,7.