bluuebunny/crossref_metadata_2025 huggingface dataset:
MgCl2‐supported Ziegler‐Natta catalysts: Synthesis and X‐ray diffraction characterization of some MgCl2‐Lewis base adducts
Authors: Noto Vito Di , Marigo Antonio , Viviani Maria , Marega Carla , Bresadola Silvano , Zannetti Roberto
Published: April 2003

Some adducts of MgCl2 and Lewis bases (or donors) B were examined, having a composition MgCl2 · 2B, where B = Ethyl (Et) formate, Et acetate, Et propionate, Et benzoate, Et crotonate, acetone, 2‐butanone and EtOH. The crystallographic investigation of these adducts, carried out on polycrystalline powders and some single crystals, shows some remarkable structural analogies for all examined donors. In particular, the X‐ray diffraction patterns of the adducts indicate the total absence of the close‐packing of chlorine which characterizes α‐MgCl2 and the presence of covalent Cl‐Mg‐Cl chains. The obtained data are correlated with the preparation of active supports for Ziegler‐Natta olefin polymerization: after total elimination of B, a disordered structure of MgCl2 is obtained, which is coincident with the reported one for the mechanically activated (by ball‐milling) MgCl2 and previously described both in the scientific and in the patent literature.
Highly oxygen‐permeable copoly(methacrylate/siloxane)s with perfluoroalkyl ester groups
Authors: Koßmehl Gerhard , Fluthwedel Andrea , Schäfer Horst
Published: April 2003

Basic materials for contact lenses were obtained by radical copolymerization of linear α,ω‐bis(methacryloyloxy)‐terminated oligo‐ and poly(dimethylsiloxane)s, methyl methacrylate and 2,2,3,3,4,4,4‐heptafuorobutyl methacrylate. Oxygen permeabilities, contact angles and ball indentation hardness were determined.
Effect of the internal/external donor pair in high‐yield catalysts for propylene polymerization, 2. Polymerization results
Authors: Barbè Pier Camillo , Noristi Luciano , Baruzzi Giovanni
Published: April 2003

The behaviour in propylene polymerization of catalysts containing ethyl benzoate/methyl p‐toluate (EB/MPT) or dibutyl phthalate/triethoxy(phenyl)silane (DBP/EPS) as internal/external donor pairs was investigated. Comparing catalyst composition with performance, it appears that no qualitative difference exists in the role of MPT and EPS, both acting as poisons of atactic sites and activators of isotactic sites. A higher efficiency of EPS is evident. On the contrary, a difference can be found between the internal donors EB and DBP/DBP seems not directly involved in the formation of isotactic centers as EB. These results, though obtained under conditions leading to much lower activities than usual for the catalysts considered, can be assumed to describe the general behaviour of the donor pairs investigated when the polymerization is carried out in the absence of hydrogen.
Studies of the free‐radical reaction kinetics and of the influence of lewis acids on the copolymerization of acrylonitrile with furan compounds
Authors: Chau Chun‐Wah , Fawcett Allan H. , Mulemwa Jane N. , Poon Lai Wo , Surgenor Avril , Tan Chu‐Eng
Published: April 2003

We found that furan and alkyl‐substituted furans function as slowly reacting monomers rather than retarders or inhibitors in free‐radical copolymerization reactions with acrylonitrile. The effect of the presence of Lewis acids was examined: some cause an ionic reaction of the furan ring, one (SO2) acts as an inhibitor, and others enhance the entry of the furan into the copolymer, increase the yield and molecular weight, and for 2‐methylfuran cause a new type of furan residue to form by promoting a hydrogen abstraction reaction.
Synthesis of poly(vinyl ether)s with perfluoroalkyl pendant groups
Authors: Höpken Jens , Möller Martin , Lee Myongsoo , Percec Virgil
Published: April 2003

2‐Perfluoro(alkyl)ethyl vinyl ethers, F(CF2)nCH2CH2OCHCH2, (n = 6 or 8), were synthesized and polymerized by means of cationic initiators (HI/ZnI2 and CF3SO3H/(CH3)2S). The perfluorohexyl‐substituted poly(vinyl ether) is completely amorphous. The polymer with perfluorooctyl segments shows side chain crystallization with a disordering transition. For the corresponding perfluorooctyl monomer a liquid‐crystalline phase was observed before melting. Copolymerization experiments of the flurocarbon‐segmented monomers with a vinyl ether containing a cyanobiphenyl group in the side chain did not give homogeneous copolymers. This is attributed to the slower rate of polymerization of the fluorinated vinyl ethers as compared with the liquid‐crystalline comonomer.
Oligomerization of oxiranes in the presence of phosphorus acids, 2. Kinetics of addition of ethylene oxide to phosphoric and phosphorous acid
Authors: Biela Tadeusz , Szymanski Ryszard , Kubisa Przemyslaw
Published: April 2003

Kinetics of addition of ethylene oxide to the POH groups in phosphorous (H3PO3) and phosphoric acid (H3PO4) were studied. The reaction is catalysed by the POH groups themselves, presumably by formation of hydrogen‐bonded complexes with ethylene oxide. The values of apparent rate constants of reactions involving subsequent POH groups were determined. The apparent reactivity of POH increases with increasing number of OCH2CH2OH substituents present in the reacting molecule. This has been attributed to the formation of intramolecular hydrogen bonds influencing the reactivity of the POH groups. Mechanistic implications and the distribution of products are discussed in connection with the observed kinetic dependences.
The effect of chain transfer agent on the entry of free radicals in emulsion polymerization
Authors: Maxwell Ian A. , Morrison Bradley R. , Napper Donald H. , Gilbert Robert G.
Published: April 2003

The model of Maxwell et al. (Macromolecules 24, 1629 (1991)) for initiator efficiencies in emulsion polymerization has been extended to take into account the effect of added chain transfer agent (CTA). The model supposes that the rate‐determining step for radical entry into latex particles is aqueous‐phase propagation of the primary free radicals to a critical chain length z required for entry (forming species such as .MzSO, where M is a monomer entity and peroxodisulfate S2O is the initiator). The effect of CTA on the entry rate is assumed to occur by facilitating the production of aqueous‐phase free‐radical species (CTA.) by transfer between species such as .MzSO (where n < z) and CTA in the aqueous phase. The CTA. will be formed at a reasonable rate provided the CTA is not too water‐insoluble (e.g. C12H25SH); it should also be capable of entering the latex particles rapidly because of its relative insolubility. If the monomer‐derived .MnSO tend to suffer aqueous‐phase termination rather than entry, the overall rate of entry (and hence initiator efficiency) will be increased. This can explain the accelerating effect of intermediate molecular weight CTA's on emulsion polymerization of monomers such as butadiene, where z is large and hence initiator efficiency is very low in the absence of CTA, because most .MnSO undergo termination rather than entry into the latex particles.
Copolymerization of ethylene and propene with soluble TiCl3 catalyst systems
Authors: Makino Kenya , Tsuda Kazuichi , Takaki Mikio
Published: April 2003

For random copolymerization of ethylene and propene, the catalytic activity was studied of various catalyst systems consisting of TiCl3 prepared by reduction of TiCl4 with hydrogen. The extent of reduction of TiCl4 markedly affects the activity of the catalyst. Furthermore, the combination of solvent and donor affects the activity, and 1,2‐dichloroethane and dibutyl ether (DBE) was found to be the most favourable combination. Metal halides (MXn) such as VCl4 and VOCl3 enhance the activity of the TiCl3 catalyst. Concerning the co‐catalyst, triisobutylaluminium results in the highest activity. As a whole, both the catalytic activity of these catalyst systems and the structure of the resulting copolymer are largely dependent on the solubility of the catalyst system. The copolymer obtained with a soluble TiCl3 · DBE · Al(isobutyl)3 system is highly isotactic in the PPP triad and has a lower content of inversion than a copolymer prepared with a conventional VOCl3 catalyst system. Moreover, the copolymer obtained with the above TiCl3 catalyst has superior physical properties, especially tensile properties, in comparison with the copolymer obtained with the conventional VOCl3.
Copolymers prepared on the basis of isopropenyl derivatives of o‐carborane
Authors: Teplyakov Michail M. , Khotina Irina A. , Sakharova Antonina A. , Mel'nik Olga A. , Papkov Vladimir S. , Kvachev Jurie P.
Published: April 2003

New mono‐ and bifunctional isopropenyl derivatives of o‐carborane were synthesized according to the Witting reaction, from the corresponding acetyl derivatives and methylenetriphenylphosphorane. The radical copolymerization with methyl methacrylate was investigated and thermal and thermomechanical characteristics of the obtained copolymers were studied. In copolymers prepared on the basis of a monofunctional carborane‐containing monomer, the increase of glass transition temperature takes practically a linear course with increasing boron content. In crosslinked copolymers the presence of o‐carborane fragments leads to the widening of the glass transition temperature range, predominantly at low temperatures, irrespective of the type of bifunctional monomer used.
Solvent effects on free‐radical polymerization, 3. Solvent effect on polymerization rate of methyl methacrylate and N‐vinyl‐2‐pyrrolidone
Authors: Czerwinski Wojciech K.
Published: April 2003

The homopolymerizations of methyl methacrylate (MMA) in N‐methyl‐2‐pyrrolidone (NMP) and of N‐vinyl‐2‐pyrrolidone (NVP) in methyl isobutyrate (MiB) were investigated at 60°C using AIBN as initiator. Reaction rate and dynamic viscosity of the medium were determined as function of monomer dilution. It follows from the estimated monomer exponent n that MMA reacts in NMP faster (n = 0,739) and NVP in MiB slower (n = 1,495) in comparison with reaction rates obtained from the direct proportionality of monomer concentration. The observed deviation was quantitatively separated in partial deviations caused by chain initiation, propagation and termination. It was found that the viscosity effect on chain termination plays a dominant role in the global solvent effect. Chain propagation is influenced by electron donor‐acceptor interactions between monomers and solvent.
Influence of thionoesters on the degree of polymerization of styrene, methyl acrylate, methyl methacrylate and vinyl acetate
Authors: Meijs Gordon F. , Rizzardo Ezio , Le Tam P. T. , Chen Yi‐Chi
Published: April 2003

The aromatic thionoester 3 (benzyl thionobenzoate) was an effective chain transfer agent in polymerizations of styrene (Cx = 1,0) and methyl acrylate (Cx = 1,2) at 60°C. This activity was close to the ideal for obtaining narrow molecular‐weight distributions in batch polymerizations. The thionoester 3 showed no activity in polymerizations of methyl methacrylate, but was too reactive to be useful in vinyl acetate polymerizations. Ring‐substituted thionoesters 9‐11 and 14 and 1H NMR spectroscopy of the resulting polymers were used to establish the type and quantity of end‐groups. The thionoester 12 was used to produce low‐molecular‐weight polystyrene that was terminated at one end with a hydroxy group and at the other end by a thioloester moiety.
Polymerization of 1‐alkynes initiated by transition metal carbene complexes, 3. Kinetics and mechanism of the propagation reaction
Authors: Fontanille Michel , Lucas Christine , Soum Alain
Published: April 2003

A comprehensive study of the 1‐heptyne polymerization initiated by a carbene complex of tungsten was carried out. Kinetic orders, apparent rate constants and thermodynamic parameters of the propagation step were determined. The structure of the organic products appearing simultaneously with the polymer during the reaction was identified by NMR and mass spectrometry. According to the experimental data, a mechanism of the propagation reaction is proposed: the propagating species derive from an initial active carbenic complex formed consequently by the insertion of the first monomer molecule into the [CW] bond of the initiator. Then, these active centres give, through a steady‐state process, active high‐polymeric chains. In competition with the normal insertion of the monomer molecules, termination and transfer reactions occur, including or not the monomer and/or the polymeric chain.
Potassium ion‐based polyurethane anionomers: effects of emulsification on structure and physical properties
Authors: Chen Show‐An , Hsu Jen‐Sung
Published: April 2003

A polyurethane was prepared using poly(oxytetramethylene) as soft segments, 4,4′‐methylenedi(phenyl isocyanate) as diisocyanate and 2,2‐bis(hydroxymethyl)propionic acid as chain extender, and then ionized with potassium hydroxide to yield the potassium ion‐based PU anionomer. The resulting PU anionomer solution in ethyl methyl ketone was emulsified by continuous addition of water. In the unionized film, soft segment crystallites are not present. Ionization creates soft segment crystallites and produces increased cohesion in the hard domains, which leads to an increase in both tensile strength and elongation at break. Emulsification of the PU ionomer solution leads to slightly increased phase separation. During the emulsification, conductivity and viscosity variations show that water is first adsorbed on the surface of the hard‐segment microionic lattices and then enters into the disordered hard domains. The morphology of the unionized film shows that the hard domains are dispersed in the soft domains and tha the size of hard domains increases greatly after the ionization. After dispersion, the hard segments originally distributed in the dispersed phase undergo phase inversion and adopt a morphology of interwoven soft and hard domains. Compared with other PU anionomers, the present system is branched rather than linear, as reflected in the good mechanical properties of the present system.
Crystallization kinetics of β‐phase poly(propylene)
Authors: Shi Guan‐yi , Zhang Xiao‐dong , Qiu Zhi‐xue
Published: April 2003

Crystal growth rates of spherulites of β‐phase poly(propylene)s and of an ethylene/propene block copolymer, crystallized from the melt, have been investigated in the temperature range of 122 to 146°C. On the basis of the regime theory, a transition between regime II and III is found at ΔT ≈ 37–43,5 K. The nucleation constant for β‐phase poly(propylene)based on the current theory of crystal growth was determined, and the fold surface free energy of β‐phase poly(propylene) was estimated from the nucleation constant for different samples to lie between 48,2 and 55,2 erg/cm2 (1 erg = 10−7 J).
Synthesis of mainly linear poly(dichlorophenylene oxide)s by thermal polymerization in solution
Authors: Şanlt Oya , Kisakürek Duygu
Published: April 2003

Thermal decomposition of bis(4‐bromo‐2,6‐dichlorophenoxo)‐(N,N,N',N'‐tetramethylethy‐lenediamiene)copper(II) complex in toluene, bis(4‐bromo‐2,6‐dichlorophenoxo)(N,N‐dimethyl‐formamide)copper(II) complex in N,N‐dimethylformamide and bis(4‐bromo‐2,6‐dichlorophenoxo)(dimethyl sulfoxide)copper(II) complex in dimethyl sulfoxide was achieved at 70°C. 4‐Bromo‐2,6‐dichlorophenol derivatives prefer 1,4‐addition to 1,2‐addition, leading to highly linear polymers irrespective of the substituted ligands. The complexes were characterized by IR spectroscopy and C, H, N elemental analysis. The characterization of the synthesized polymers were achieved by 1H NMR, 13C NMR and IR spectroscopy. The highest polymer yield was obtained from the decomposition of bis(4‐bromo‐2,6‐dichlorophenoxo)(N,N,N',N'‐tetramethyl‐ethylenediamine)copper(II) complex.
Analysis of the linear methods of determining copolymerization reactivity ratios, 13. A critical application of penultimate model (r2 = 0) to radical copolymerization data of styrene
Authors: Kelen Tibor , Tüdős Ferenc , Turcsanyi Béla , Braun Dietrich , Czerwinski Wojciech K.
Published: April 2003

In an until now widest study of the penultimate effect the reactivity ratios of 66 published styrene copolymerization systems showing a non‐classical behaviour have been reviewed. For the alternating systems a simplified two‐parameter penultimate model with r2 = r′ = 0 was applied. The systems were classified into 2 groups: 1. alternating and 2. non‐alternating systems. 32 systems of the first group have been reevaluated. r‐Values, together with their 95% confidence limits have been calculated. The confidence parameter δ′ and the “efficiency factor” of planning Q, suitable for classification of the systems, have been applied. In this number 23 (72%) systems yielded linear Kelen‐Tüdős‐plots (13 belong to class I, 10 to class I!). 5 (16%) systems were assigned to class II (non‐adequacy of the penultimate model possible) and 4 (12%) to class III, where the experimental data are inconsistent and the r‐values meaningless.
Physically interpenetrating networks in polyurethane ionomers/poly(vinyl alcohol) blends
Authors: Hsu Jen‐Sung , Su Fu‐Hu , Chen Show‐An
Published: April 2003

Three series of blends of polyurethane ionomers (PUI) with poly(vinyl alcohol) (PVA) were prepared by mixing aqueous PUI emulsions with aqueous PVA solutions and then allowing them to dry. The characterization of the blends of various compositions was carried out using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry and tensile‐elongation testing. It was found that poly(ether‐urethane) cationomer (Cat‐Et)/PVA‐1 and poly(ether‐urethane) anionomer (An‐Et)/PVA‐2 blends exhibit a positive synergistic effect with respect to the tensile strength and that the amorphous phase of PVA is at least partially compatible with both the disordered hard domains and the soft domains of the ionomers. For the former blends, this behaviour is due to the formation of hydrogen bonding with the glycolate anions and ether groups, and for the latter blends to the formation of hydrogen bonds with the ether groups. For poly(ester‐urethane) cationomer (Cat‐Es)/PVA‐3 blends, there is no hydrogen bonding between these two components and no synergistic effect in the tensile strength after blending. Physically interpenetrating polymer networks (IPNs) are expected to occur in the former two blends, but not in the latter one.
Acylation of hydroxyl groups in polymers with carbonic acid derivatives in the presence of tertiary amines
Authors: Boeden Hans‐Friedrich , Büttner Werner , Rupprich Christian , Büttner Dorothea , Heinrich Sigrun , Becker Manfred , Holtzhauer Martin
Published: April 2003

Symmetrical carbonates were formed when the corresponding carbonochloridates containing electron‐withdrawing groups were converted with tertiary amines in dry solvents at room temperature. 5‐Norbornene‐2,3‐dicarboximido carbonochloridate (1) and bis(5‐norbornene‐2,3‐dicarboximido) carbonate (5) were used for acylation of OH groups in polymers in the presence of tertiary amines under anhydrous conditions. The influence of the amounts of 1 and 5, the kind and amount of amines, the organic solvent, the reaction time and temperature on the yield of the active carbonate 7 was investigated using bead cellulose as polymer. The reaction based on the catalysis by strongly nucleophilic amines such as 4‐dimethylaminopyridine (DMAP) was optimized for preparation of acylated polymers. The formation of cross‐linking and cyclic carbonates 9 and 10, respectively, was observed as a side reaction. It was shown that carbonates 9 and 10 can also be obtained as the main products of acylation. The preparation of 9 was also carried out by treating 7 with an excess of DMAP. Examples are presented for the transesterification of 7 with compounds containing OH groups. The acylated polymers were characterized by a specific titration method, UV/VIS and IR spectroscopy. The mechanism of the DMAP‐catalyzed acylation of polymers is discussed.
The higher homologues of triphenylamine: Model compounds for poly(N‐phenyl‐1,4‐phenyleneamine)
Authors: Strohriegl Peter , Jesberger Gabrile , Heinze Jürgen , Moll Thomas
Published: April 2003

Well‐defined model compounds of poly(N‐phenyl‐1,4‐phenleneamine)(2), the dimer5, the trimer6and the tetramer7, were prepared by stepwise synthesis. Cyclic voltametry and the mass spectra demonstrate the high stability of the radical cations from the model compounds. The UV spectra show that there is some conjugation through the lone electron pair at the nitrogen atom, but the amount of conjugation is rather small. Oligo(N‐phenyl‐1,4‐phenyleneamine)(2)with an average degree of polymerization of 10 was prepared by metalation ofN,N′‐diphenyl‐1,4‐phenylenediamine and subsequent reaction with 1,4‐diiodobenzene.
Enhanced electrochromic stability of polyaniline in polyaniline‐matrix polymer composite films in aprotic medium
Authors: Morita Mitsuyuki , Hashida Isao
Published: April 2003

Electrochromic behavior and stability in aprotic medium of polyaniline composite films prepared by chemical oxidative polymerization at gas/liquid interface were investigated. The results are compared with chemically and electrochemically snythesized polyaniline homogeneous films. The polyaniline composite films show almost the same electrochromic behavior as the homogeneous films. The behavior is due to a two‐step oxidation mechanism, which is different from that in aqueous medium, especially in the second oxidation process. Degradation of polyaniline in aprotic medium is due to the partial formation of the electrochemically inactive quinonediimine structure in the higher oxidized state. The degradation is restrained by hybridization with an appropriate matrix polymer. The stabilization of the electrochromic behavior of polyaniline depends on molecular weight and pKa of the matrix polymer.
Synthesis of a new family of poly(amido‐amine)s carrying poly(oxyethylene) side chains
Authors: Vansteenkiste Stefan , Schacht Etienne , Ranucci Elisabetta , Ferruti Paolo
Published: April 2003

A new class of water‐soluble poly(amido‐amine)s (PAA's) carrying poly(oxyethylene) (PEO) side chains were synthesized following two distinct pathways. The first route consists in the direct stepgrowth polymerization through addition in water of an equimolar amount of α‐(2‐aminoethyl)‐ω‐methoxypoly(oxyethylene) (6) of well‐defined molecular weight to 1,4‐bis(acryloyl)‐piperazine (7). Furthermore, this reaction was performed in the presence of an excess of the bisacrylmonomer 7, resulting in a new bisacrylic macromonomer (9) of PEO. In the second route this bisadduc 9 was then polymerized with piperazine (10), yielding a PEO‐grafted PAA. The structures of both polymers were characterized by means of 1H NMR. Viscosity and vapour pressure osmometric measurements revealed that the molecular weights in both cases were fairly low (M̄n ≈ 3 000).
Copolymerization of epoxides and five‐membered cyclic carbonates in the presence of zinc coordination catalysts
Authors: Kuran Witold , Listoś Tomasz
Published: April 2003

Alkylene oxides like ethylene oxide (1a) and propylene oxide (1b) were reacted with alkylene carbonates like ethylene carbonate (2a) and propylene carbonate (2b) in the presence of catalysts based on diethylzine and polyphenols (pyrogallol, 4‐tert‐butylcatechin) and catalysts based on diethylzinc‐phenol at temperatures in the range of 35–100°C. Reaction products were characterized by means of elemental analysis, IR, 1H NMR and 13C NMR spectroscopy and molecular weight determinations. The products appeared to be the respective low‐molecular‐weight copolymers – poly[oxyalkylene‐co‐(alkylene carbonate)]s: poly[oxyethylene‐co‐(ethylene carbonate)] (3 aa), poly[oxyethylene‐co‐(propylene carbonate)] (3 ab), poly[oxypropylene‐co‐(ethylene carbonate)] (3 ba) and poly[oxypropylene‐co‐(propylene carbonate)] (3 bb). Copolymers obtained with diethylzinc‐polyphenol catalysts were of higher molecular weight than those obtained with diethylzinc‐phenol catalysts. They contained more than 50 mol‐% of alkylene oxide units. Predominant head‐to‐tail arrangement of these units including those connected via carbonate linkages was observed by means of NMR spectroscopy in the case of 3 bb.
Viscometric characterization of poly(oxyethylene)‐block‐poly(oxypropylene)‐block‐poly(oxyethylene) in aqueous solution
Authors: Bloß Peter , Hergeth Wolf‐Dieter , Wohlfarth Christian , Wartewig Siegfried
Published: April 2003

Viscometric measurements were carried out to characterize poly(oxyethylene)‐block‐poly‐(oxypropy1ene)‐block‐poly(oxyethy1ene) (POE‐POP‐POE) in aqueous solution. The results were discussed in terms of a core‐shell model of intramolecular phase separation which is based on (i) the selectivity of the solvent water, and (ii) the incompatibility of the POE and POP blocks. The interaction between the two blocks was analysed by vapour pressure osmometry and vapour sorption investigations.

The results are:

The two homopolymer blocks (POE and POP) forming the triblock copolymer are incompatible with each other as vapour pressure osmometry and vapour sorption measurements using ethylbenzene as solvent have shown. This incompatibility of the blocks as well as the selectivity of the solvent water with respect to the different blocks causes the intramolecular (and intermolecular) phase separation of the copolymers in aqueous solution.

The viscometric data of the aqueous block copolymer solutions can be discussed in terms of the generally accepted core‐shell model. This model for the structure of the self‐organized molecules includes POP gel core (“melt”) surrounded by solvated POE shell. A quantitative analysis according to this simplified view shows that the hydrodynamic volume of the copolymer molecules is determined by the POE blocks. In the temperature range ϑ > 30°C, the influence of the POP block on the molecular dimensions is negligible, whereas at ϑ < 30°C the contributions of the POP and POE to the molecular volume are comparable.

Kuhn's statistical segment length of POE in the triblock molecules comprises about 4–5 monomeric units. The theta temperature of the triblock copolymer molecules is nearly identical to that of pure POE ((369 ± 3)K).
Utilisation de l'analyse viscoélastique dynamique à l'étude de la cristallisation isotherme du poly(téréphtalate d'ethylène) amorphe. Application à des composites unidirectionnels avec fibres de verre
Authors: Gauthier Catherine , Chailan Jean‐François , Chauchard Jacques
Published: April 2003

Dynamic viscoelastic analysis was used to continuously follow the “cold crystallisation” of poly(ethylene terephthalate) (PET) test bars. Samples which were cut from an amorphous PET sheet were heated to a given temperature in a hot cell. The evolution of the real part of the modulus not only allows the kinetic crystallisation parameters but also the nucleation and growth characteristics to be determined. This method was applied to unidirectional PET/glass fibre composite strips. Thus, the influence of the glass fibres on the morphological and kinetic characteristics of the matrix crystallisation has been investigated.
Magnesium stearate based titanium catalyst systems for propene polymerization
Authors: Gupta Virendra Kumar
Published: April 2003

Supported titanium catalysts are prepared by chlorination of magnesium stearate with silicon tetrachloride (Mg, Ti‐S) or titanium tetrachloride (Mg, Ti‐T) followed by treatment of the product with diisobutyl phthalate and titanium tetrachloride. The data indicate that the change in the nature of the chlorinating compound affects the composition as well as physical characteristics of the catalysts. The results of propene polymerization show that the Mg, Ti‐T/AlEt3 catalyst system has about 50% more productivity and higher isospecificity as compared to the Mg, Ti‐S/AlEt3 system. Furthermore, the isospecificity of the Mg, Ti‐T/AlEt3 system is independent of polymerization time, whereas the Mg, Ti‐S/AlEt3 system shows a change of isospecificity with time. Addition of an external Lewis base and cocatalyst [triethoxy(phenyl)silane with triethyl‐aluminium] to the Mg, Ti‐T catalyst substantially improves the isospecificity of the system.
Terpolymer relationships and ternary azeotropes
Authors: Ham George E.
Published: April 2003

A paper by Quella which appeared in this journal (Makromol. Chem. 190, 1445 (1989)) criticized a 1983 publication by this author. Quella has suggested that my paper postulating the non‐existence of ternary azeotropes “is contradicted on the basis of mathematical solutions and further experimental results from other authors.” The present paper is in response to Quella.
Addition of oxiranes to the acids of phosphorus. Direction of ring opening
Authors: Biela Tadeusz , Kubisa Przemyslaw , Penczek Stanislaw
Published: April 2003

The proportion of the α‐ and β‐ring opening in the addition of unsymmetrically substituted oxiranes to POH acids namely diethyl phosphoric acid, phosphorous acid, and phosphoric acid, was established. Ring opening of propylene oxide does not depend on the number of the POH groups in the acid and, for di‐ and trifunctional acids, does not depend on the degree of substitution. After this first reaction of addition the formed hydroxyl groups add the oxirane molecules and the phosphorus‐containing polyethers are formed. All of the propylene oxide additions exhibit a ratio of α/β‐ring openings of 1:1. For the higher substituted oxiranes the proportion of the attack on the least substituted carbon atom increases, reaching for 1,1‐dimethyloxirane up to 90% of α‐addition (almost exclusive formation of the tertiary alcohol).
Emulsion copolymerization of vinyl chloride with butyl acrylate
Authors: Capek Ignac , Mrázek Zdenek
Published: April 2003

The emulsion copolymerization of vinyl chloride and butyl acrylate initiated by ammonium peroxodisulfate at 60°C in the presence of an anionic emulsifier was investigated. Random copolymers of butyl acrylate and vinyl chloride covering several sets of monomer compositions were synthesized by emulsion copolymerization conducted to both low and high conversions. The rate of butyl acrylate polymerization at medium conversion was found to be proportional to the 0,5 and 1,0 power of the butyl acrylate concentration for the system with and without vinyl chloride. The overall rate of poymerization was found to decrease with increasing vinyl chloride concentration in the monomer feed. The particle size increases with increasing vinyl chloride monomer concentration in the monomer feed and conversion. The decrease in molecular weight of butyl acrylate/vinyl chloride copolymer is accompanied with the incease of vinyl chloride concentration in the monomer feed and of conversion. The results are discussed in terms of radical desorption, particle nucleation and the dependence of the equilibrium monomer concentration on the reactor pressure.
Electric characteristics of polycation perchlorate composites as a solid electrolyte and its application
Authors: Ishizawa Ryosyo , Seki Miharu , Kadoi Kiyoaki , Yosomiya Ryutoku
Published: April 2003

Polycation perchlorate composites have excellent film‐forming properties and high ionic conductivity. The ionic conductivity at 40°C is of the order of 10−7−10−5S·cm−1, depending on the kind of perchlorate. The temperature dependence of the ionic conductivity follows the Williams‐Landel‐Ferry relationship. Furthermore, the electrochemical polymerization of pyrrole using polycation perchlorate composites as a solid electrolyte produces bilayer composite films.
Styrene polymerization in oil‐in‐water microemulsions: kinetics of polymerization
Authors: Gan L. M. , Chew C. H. , Lye I.
Published: April 2003

Microemulsion polymerization of styrene was carried out in water, hexadecyltrimethylammonium bromide or sodium dodecyl sulfate, and butyl carbitol (system. name: 2‐(2‐butoxyethoxy)ethanol) using water‐soluble potassium peroxodisulfate (KPS) or oil‐soluble 2,2′‐azoisobutyronitrile (AIBN) as initiator. The latexes have been stable for one year. The effects of temperature, initiator and monomer concentrations on the polymerization kinetics were investigated. The polymerization rates were measured by dilatometry and show two stages (nucleation and growth). A longer nucleation period was found in the polymerization initiated by KPS as compared to AIBN. The initial polymerization rate varied with the 0,47 power of KPS concentration and the 0,39 power of AIBN concentration. The activation energy of the polymerization was found to be relatively low (ca. 50 kJ/mol) for the system initiated with AIBN and about 90 kJ/mol for the KPS‐initiated system. Molecular weights of polystyrene of several millions were obtained in all cases, especially for systems initiated with AIBN. The latex particles were nearly spherical with an average particle diameter of about 25 nm. The mechanism of polymerization in the oil‐in‐water microemulsion is discussed.
Synthesis and properties of water‐soluble polyphosphazenes with aminoalcoholic functions
Authors: Crommen Jan H. L. , Vandorpe Joke , Schacht Etienne H.
Published: April 2003

Phosphazene polymers with 2‐(trimethylsiloxy)ethylamino, 3‐(trimethylsiloxy)propylamino and 2,3‐bis(trimethylsiloxy)propylamino substituents are described. These polymers have been prepared by reaction of the corresponding hydroxy‐protected aminoalcohol with poly(dichlorophosphazene). Total halogen replacement was achieved only with the 2‐(trimethylsiloxy)ethylamino and 3‐(trimethylsiloxy)propylamino groups. Replacement of remaining chlorine was achieved by subsequent introduction of glycine ethyl ester groups as co‐substituents. The trimethyl silyl‐protecting groups were removed by reaction of the polymer with tetrabutylammonium fluoride. This yielded water‐soluble degradable polyphosphazene derivatives with 2‐(hydroxyethyl)amino, 3‐(hydroxypropyl)amino or 2,3‐(dihydroxypropyl)amino substituents. The structures and physical properties of the prepared polymers were investigated using NMR, IR, and thermal analyses. The hydrolytical degradation of the final water‐soluble polymers was also evaluated. A significant reduction in reduced viscosity and the release of 3‐amino‐1‐propanol was observed during incubation in water at 37°C of the polyphosphazene derivative substituted with 3‐(hydroxypropyl)amino groups.
High‐molecular‐weight polyethylene: growth reactions at bis(dichloroaluminium)ethane and trialkylaluminium
Authors: Martin Heinz , Bretinger Helmut
Published: April 2003

When the temperature of the reaction of 1,1‐bis(dichloroaluminium)ethane or trialkylaluminium with ethylene is reduced to room temperature, polyethylenes with a largely linear structure having molecular weights between 300 000 and 9300 000 are produced. The stepwise addition of trialkylaluminium to ethylene then leads to highly crystalline products having melting ranges around 140°C. The reaction is no longer accompanied by the displacement reaction forming a‐olefins.
Effect of the alkyl residues on the glass transition temperature of methacrylonitrile/alkyl methacrylate copolymers
Authors: Román Julio San , Vázquez Blanca , Valero Miguel , Guzmán Gonzalo Martín
Published: April 2003

The glass transition temperature of copolymers of methacrylonitrile with methyl, ethyl and butyl esters of methacrylic acid, together with those of the corresponding homopolymers, were determined by differential scanning calorimetry. The variation of the glass transition temperature (Tg) of copolymers with the composition of the samples was analyzed for each system on the basis of treatments suggested by Barton, Johnston and Suzuki‐Mathot, determining the values of the glass transition temperature of the alternating diad (Tg12). It was observed in all the cases that the alternating diad presents a flexibility higher than that expected from the combination of both kinds of monomeric units according to the Tg of the corresponding homopolymers and that the Tg12 values decrease with the length of the side chain of the methacrylate ester in the system, as the Tg values of the polymethacrylates.
Synthèse de polystyrènes chlorométhylés renfermant de nouveaux groupements tétrathiafulvalénylcarbonyloxyméthyles
Authors: Mora Henri , Fabre Jean‐Marc , Giral Louis , Montginoul Claude , Sagnes René , Schué François
Published: April 2003

In order to conserve high contrast while improving the sensitivity of microlithographic resins made up of polystyrene bearing tetrathiafulvalene (TTF) units, we prepared new polystyrenes containing tetrathiafulvalenylcarbonyloxymethyl groups which are methylated or non‐methylated. The polymers were synthesized by reaction of poly[styrene‐co‐(p‐chloromethyl‐styrene)] with the corresponding caesium tetrathiafulvalenecarboxylate. To optimize this grafting reaction, preliminary reactions were carried out with model molecules.
Crystal structure of the form I of syndiotactic poly(1‐butene)
Authors: De Rosa Claudio , Venditto Vincenzo , Guerra Gaetano , Corradini Paolo
Published: April 2003

The crystal structure of the form I of syndiotactic poly(1‐butene) is presented. According to the present analysis, chains having s(2/1)2 helical conformation are packed in an orthorhombic unit cell with a = 16,81 Å, b = 6,06 Å and c = 7,73 Å. The density is 0,96 g/cm3 with two chains in the cell (8 monomeric units), the space group is C2221. Disorder, corresponding to the statistical presence of right‐ and left‐handed helices in each site of the lattice, could be present. The space group for the completely disordered structure is Cmcm.
Copolymerization reactivities and electron structure of 2‐alkyl‐5‐vinyltetrazoles
Authors: Ivashkevich Oleg A. , Gaponik Pavel. N. , Kovalyova Tamara B. , Makarevich Nonna I. , Sushko Natalia I.
Published: April 2003

Three novel monomers: 2‐ethyl‐, 2‐isopropyl‐ and 2‐tert‐butyl‐5‐vinyltetrazole were synthesized. The copolymerizations of these monomers and 2‐methyl‐5‐vinyltetrazole with styrene and methyl methacrylate were examined and the corresponding reactivity ratios r1, r2 and the Alfrey‐Price Q, e values estimated. The obtained results, together with IR, 1H NMR and 13C NMR data and quantum‐chemical calculations of vinyltetrazole molecules by the AM‐1 method, indicate that the type and the size of the substituent does not essentially influence the reactivity of 2‐alkyl‐5‐vinyltetrazoles in radical copolymerization with vinyl monomers.
Synthesis and characterization of amphiphilic and microphase‐separated graft copolymers, 1. Synthesis and bulk characterization of polystyrene‐graft‐ω‐stearyl‐poly(ethylene oxide)
Authors: Qiu Yongxing , Yu Xiaojie , Feng Linxian , Yang Shilin
Published: April 2003

Using the rigid and hydrophobic polystyrene (PS) chain as backbone, onto which flexible and hydrophilic stearyl‐poly(ethylene oxide) (SPEO) chains are grafted, a new kind of amphiphilic, microphase‐separated graft copolymer was synthesized using the macromonomer technique. Stearyl‐poly(ethylene oxide) macromonomers with acryloyl end‐group (SPEO‐A) were prepared through an end‐group exchange reaction of α‐stearyl‐ω‐hydroxypoly(ethylene oxide) (SPEO‐OH) and acryloyl chloride in the presence of triethylamine. The radical copolymerization of styrene with SPEO‐A was carried out under various experimental conditions. Following a careful examination of their purity, the structure of the prepared copolymers was characterized by means of IR, 1H NMR and GPC analyses. A new feasible method using first derivative UV spectrometry was developed for quantitative determination of the bulk composition of the graft copolymers. Copolymers with a wide range of bulk composition and satisfactory grafting degree were obtained.
Synthese von nitrogruppenhaltigen copolymeren durch radikalische copolymerisation
Authors: Tauer Klaus , Wedel Armin , Morozova Elena M.
Published: April 2003

Radical copolymerization of a nitro group containing azo‐dye monomer (1) and methyl methacrylate leads to significantly higher polymerization rates and higher molecular weights when dispersion technique is used instead of solution polymerization. The preparation of mechanically stable coatings and free films with good mechanical properties and transparency for electro‐optical investigations is possible by a spin coating technique with the dispersion copolymers. The dye side chains of these copolymers can be poled in an electric field. The orientation of the side chains leads to a change of the light absorption in the dye absorption band. Results of m‐line spectroscopy show that the copolymers possess wave guiding properties.
External silane donors in Ziegler‐Natta catalysis. Computerbased molecular model calculations on alkoxysilanes
Authors: Härkönen Mika , Kuutti Lauri , Seppälä Jukka V.
Published: April 2003

The electronic factors of external alkoxysilane donors used in modern Ziegler‐Natta catalyst systems were estimated by quantum mechanical MNDO (modified neglect of diatomic overlap) calculations on model compounds. The calculated electron densities of oxygen atoms in alkoxy groups were plotted against the experimental activity and the isotacticity of propene polymerization. The steric hindrance and the volume of the compounds were investigated as structural factors important to the polymerization. The results indicate that the performance of the external alkoxysilane donor is affected by both electronic and structural factors. The average electron density around the electron‐donating oxygens has some influence on the deactivating power of the donor, but when the hydrocarbon part is sterically large the sterical effects apparently dominate.
On the kinetics of emulsion copolymerization of methyl methacrylate and ethyl acrylate in the presence of hydrocarbons
Authors: Capek Ignác
Published: April 2003

The emulsion copolymerization of methyl methacrylate with ethyl acrylate initiated by ammonium peroxodisulfate in the presence of a blend of anionic and non‐ionic emulsifiers was investigated at 60°C. The polymerization under batch conditions was conducted to both low and high conversion. The kinetics of the emulsion copolymerization was studied in both the absence and the presence of diluents such as toluene and octane. Unexpectedly both diluents strongly reduced the rate of copolymerization. This reduction increased with increasing diluent concentration. The rate of polymerization was found to increase with increasing conversion up to high conversion. The average particle size increased very slightly with increasing concentration of the diluent. The average number of radicals per particle was found to increase with increasing conversion and to decrease with increasing diluent concentration. The decrease of the radical concentration with diluent concentration was attributed to the desorption of monomer radicals from a polymer particle and to the increase of the termination rate. It is proposed that the hydrophilicity of the monomeric radicals is the driving power of the desorption process.
Locus of interaction of dibenzoyl peroxide with radical inhibitors in inverse microemulsions
Authors: Vašková Viera , Hloušková Zuzana , Juraničová Viera , Bartoň Jaroslav
Published: April 2003

The locus of interaction of the oil‐soluble radical initiator dibenzoyl peroxide with inhibitors of various water‐solubility in inverse microemulsion toluene/water in the presence of sodium bis(2‐ethylhexyl)sulfosuccinate (AOT) was studied. It was found that the most probable locus of interaction of dibenzoyl peroxide with water‐soluble Fremy's salt, the predominantly water‐soluble 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐N‐oxyl, and/or predominantly oil‐soluble 4‐stearoyloxy‐2,2,6,6‐tetramethylpiperidin‐1‐N‐oxyl in the system under investigation in the presence and/or absence of monomers could be the interlayer between the water micropool and the toluene macrophase.
1H and 13C nuclear magnetic relaxation and molecular motion in solid poly(L‐alanine)
Authors: Fedotov Vladimir D. , Zadihanov Rustem A. , Spěváček Jiří , Straka Jaroslav
Published: April 2003

Nuclear magnetic relaxation data both for proton and for carbon‐13 nuclei in solid‐powder poly(L‐alanine) are analyzed together, in order to obtain information on the molecular motions in polypeptides. For this analysis the “model‐free” approach is used. Three types of internal motions are determined in the α‐helix conformation of the investigated polymer. An inhomogeneous distribution of correlation times is shown to be inherent in each type of motion. The first type is the methyl group rotation around the symmetry axis with correlation times of about one hundred picoseconds at room temperature. The second type are the small‐amplitude (≈10°) individual oscillations of backbone groups as well as of the axis of the methyl group, with correlation times from ten to one hundred nanoseconds at room temperature. The last type is the α‐helix backbone motion with correlation times of a few microseconds at room temperature and with amplitudes of 20° or more, which possibly represents the cooperative motion of several neighbouring groups in the main chain.
Cationic polymerization of methoxyallene with protonic acids
Authors: Takahashi Tatsuya , Yokozawa Tsutomu , Endo Takeshi
Published: April 2003

The cationic polymerization of methoxyallene (1) was carried out with some protonic acids at −50°C in dichloromethane. Polymer yield and molecular weight increase with the degree of acidity of the protonic acid (CF3CO2H < CH3SO3H < CF3SO3H), whereas the remaining double bond content in the polymer decreases with the acidity of protonic acids. Consequently, to obtain a polymer with high molecular weight and high double bond content (i. e., low degree of side reactions), the polymerization of 1 with medium acidic CH3SO3H gives the best results. It gives a highly unsaturated polymer in moderate yield, which can not be obtained with Lewis acids such as BF3OEt2.
Polymides, 2 Curing characterization and thermally induced polymerization of polyimides based on reverse Diels‐Alder reaction
Authors: Su Ching‐Yie , Lee Yu‐Der
Published: April 2003

Polyimides were prepared by the condensation of 3‐phenyltricyclo[6.2.2.02,7]‐2,11‐dodecadienne‐5,6:9,10‐tetracarboxylic dianhydride with diamines. Thermal curing of these polyimides was studied using thermogravimetry, infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectroscopy and elemental analyses. The results were compared with those of a model imide compound and a neat dimaleimide. It is proposed that the thermal curing mechanism is controlled by a reverse Diels‐Alder reaction, a three‐dimensional polymer network being formed following the degradation of the polymer. Based on these studies, a three‐dimensional structure is proposed if the curing temperature was over 330°C. The weight loss of isothermal thermogravimetry studies was tentatively used to determine the composition of the crosslinked structure and elemental analyses confirmed the results.
Photochemical behaviour of cinnamoyl‐containing crystalline polymers with comb‐like structure
Authors: Stumpe Joachim , Zaplo Olaf , Kreysig Dieter , Niemann Manfred , Ritter Helmut
Published: April 2003

Amorphous and crystalline comb‐like poly(methacrylamides) containing cinnamoyl moieties in the side chain were synthesized and characterized. On UV‐irradiation these polymers and related monomeric model compounds undergo E‐Z photoisomerization, [2 + 2] photocycloaddition and photo‐Fries rearrangement. The competition between these photoreactions was investigated in solution and solid films. The quantum yield of the photocycloaddition and the maximum of conversion of chromophores are much higher in solutions and in films for the crystalline homopolymer compared to the amorphous copolymer. The disappearance of crystallinity caused by isomerization in solution and in films caused by cycloaddition was demonstrated by means of DSC measurements. In films with side‐chain crystallinity the quantum yield of cycloaddition increases with rising temperature but falls drastically above the melting point. The crystallinity of the polymer influences photoreactivity of the cinnamoyl moiety, and, on the other side, photoisomerization and cycloaddition destroy the crystalline order.