bluuebunny/crossref_metadata_2025 huggingface dataset:
Détermination expérimentale des rapports de réactivité en copolymérisation: compariaison des méthodes d'Alfrey, Bohrer et Mark et de Tidwell et Mortimer
Authors: Bauduin Gérard , Boutevin Bernard , Belbachir Mohamed , Meghabar Rachid
Published: April 2003

The experimental methods for determining the copolymerization reactivity ratios r1 and r2 according to Tidwell and Mortimer (T.M.) on the one hand and according to Alfrey, Bohrer and Mark (A.B.M.), on the other hand are compared, using four examples. It is shown that they do not differ in principle: they are both curve‐fitting methods by the least‐squares technique. However, contrary to the systematical approach of A.B.M., the regression calculation of T.M. allows to estimate quantitatively the reliability of the numerical values of r1 and r2 determined.
Hydrodynamic properties of poly(1‐vinyl‐2‐pyrrolidone) molecules in dilute solution
Authors: Pavlov Georges M. , Panarin Evguenij F. , Korneeva Evgueniya V. , Kurochkin Constantin V. , Baikov Vadim E. , Ushakova Vera N.
Published: April 2003

The translational diffusion coefficient D0, the sedimentation coefficient S0, and the intrinsic viscosity [η] of samples and fractions of poly(1‐vinyl‐2‐pyrrolidone) were measured in a 0,1 M solution of sodium acetate in the molecular weight range 2 ≤ M · 10−3 ≤ 2200. For M > 4 · 104 the following relationships were obtained: [η] = 8,86 · 10−5 · M0,74, D0 = 2,42 · 10−4 · M−0,58, and S0 = 2,14 · 10−15 ·. M0,42. For M < 4 · 104 the corresponding relations are [η] = 5,0 · 10−4 · M0,56, D0 = 1,29 · 10‐4 · M−0,52 and S0 = 1,15 · 10−15 · M0,48. The hydrodynamic invariant is A0 = (3,2 ± 0,25) · 10−17 J · K−1 · mol−1/3 and the sedimentation parameter βs = (1,3 ± 0,17) · 107 mol−1/3. The temperature coefficient of the intrinsic viscosity is negative, viz. Δ ln[η]/ΔT = −6,3. 10M−3 K−1. The evaluation of the length of the Kuhn segment A and the hydrodynamic diameter d of chains representing the molecules of PVP in solution was conducted on the basis of the theory for the hydrodynamic properties of a wormlike necklace taking into account the excluded volume effects. The values of A agree with those obtained from the Burchard‐Stockmayer‐Fixman and Cowie‐Bywater equations, A = (2,1 ± 0,3) nm and d = (0,5 ± 0,13) nm.
Emulsion polymerization of styrene in the presence of poly(oxyethylene)‐poly(oxypropylene) block copolymers
Authors: Hergeth Wolf‐Dieter , Bloß Peter , Biedenweg Frank , Abendroth Peter , Schmutzler Klaus , Wartewig Siegfried
Published: April 2003

Poly(oxyethylene)‐block‐poly(oxypropylene)‐block‐poly(oxyethylene) copolymers were applied as nonionic surfactants in styrene emulsion polymerization. The clouding phenomenon of the surfactant in the aqueous phase and the resulting characteristic partition of the block copolymer between aqueous and organic phase result in two particularities of this system compared with classical emulsion polymerization: (i) bimodal particle size distribution, and (ii) unusual dependence of reaction rate on temperature.
Side‐chain liquid‐crystalline polyacrylates containing heterocyclic mesogenic groups, 1. Influence of the substituent and the number of phenyl groups on the mesomorphous properties
Authors: Legrand Cécile , Bunel Claude , Borgne Alain Le , Lacoudre Nelly , Spassky Nicolas , Vairon Jean‐Pierre
Published: April 2003

Synthesis and preliminary results on the characterization of liquid‐crystalline polyacrylates with trans‐1,3‐dioxane‐2,5‐diyl group in the side chain are presented. A stabilization of the mesophases occurs when two phenyl groups are present in the mesogenic moiety. All polymers with three rings exhibit SA mesophases except for poly(6‐[trans‐2‐(4‐(4‐methoxybenzoyloxy)phenyl)1,3‐dioxane‐5‐yl]hexyl acrylate) which presents a nematic phase over 200°C and is potentially useful as host matrix for applications in non‐linear optics.
Chirality of poly(vinyl compounds), 13. Sterical requirements in analogues of trityl methacrylate for the preparation of optically active, single‐sense helical polymers
Authors: Wulff Günter , Wu Yonghua
Published: April 2003

Trityl methacrylate possesses two different substituents at the olefinic double bond. The larger one containing the trityl group forms the outside sphere of the helix in the corresponding polymers. In this paper the role of the second, smaller substituent is discussed. For this purpose four new monomers, methyl α‐(trityloxymethyl)acrylate (5), ethyl α‐(trityloxymethyl)acrylate (6), α‐(trityloxymethyl)styrene (7), and trityl α‐ethylacrylate (3), were prepared. Polymerization experiments showed that this substituent should be of minimum size to obtain a stable helix. More extended substituents though do not fit into the helical arrangement and therefore neither anionic nor radical polymerization was achieved.
Plastic‐rubber composite, 1. The polymer‐polymer interdiffusion at the phase boundary of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) and polystyrene
Authors: Machate Christina , Lohmar Jörg , Dröscher Michael
Published: April 2003

The interdiffusion of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (PPE) and polystyrene (PS) sequences is the key step in the formation of the commonly called plastic‐rubber composite (Kunststoff‐Kautschuk‐Verbund, K&K‐V). This new process bonds PPE and poly(styrene‐co‐butadiene) rubber (SBR) during the vulcanization of the rubber, without the aid of any adhesive. As PPE and PS are fully mutually compatible polymers, polymer‐polymer interdiffusion takes place readily. PS was therefore used as a model system. Electron microscopy clearly demonstrates that the kinetics of the diffusion process are determined by the faster diffusing PS. This was studied in the temperature range of 180°C to 260°C. The interdiffusion coefficients are of the order of 10−13 to 10−10 cm2 · s−1. These are significantly higher than the selfdiffusion coefficients of PPE and PS, which are 10−15 and 10−12 cm2 · s−1, respectively. The interdiffusion coefficients are dependent on temperature and inversely proportional to the PS molecular weight, for PS molecular weights higher than the entanglement value. The diffusion process follows Fick's law. The interdiffusion coefficient is not, or is only weakly, dependent on the concentration. The interdiffusion of PS samples of molecular weights below the entanglement value is observed by a newly developed method based on Fourier transform infrared spectroscopy with attenuated total reflection technique (FTIR‐ATR). In this low‐molecular‐weight region, interdiffusion coefficients as high as 10−7 cm2·s−1 are obtained.
Plastic‐rubber composite, 2. Polymer‐polymer interdiffusion at the phase boundary of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) and poly(styrene‐co‐butadiene)
Authors: Machate Christina , Lohmar Jörg , Dröscher Michael
Published: April 2003

Interdiffusion of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (PPE) and polystyrene (PS) sequences is the key step in the formation of the so‐called plastic‐rubber composite (Kunststoff‐Kautschuk‐Verbund, K & K‐V). This new process links PPE and poly(styrene‐co‐butadiene) rubber (SBR) during the vulcanization of the rubber, without the aid of any adhesives. Polystyrene‐block‐polybutadiene (SB) is used as model for SBR. As PPE and polystyrene (PS) are fully mutually compatible polymers, polymer‐polymer interdiffusion occurs easily for PPE and the PS blocks. This is shown by electron microscopy. The thickness of the interdiffusion zone correlates to the PS block length. The respective butadiene block forms a layer on top of the interdiffusion zone. SBR with a high styrene content of at least 71 wt.‐% is also compatible with PPE. The interdiffusion kinetics of the system PPE‐SBR follows Fickian behaviour. The diffusion coefficients are smaller than for the system PPE‐PS. Although PPE and SBR with lower PS content, as it is used for the K & K‐V, are not compatible, interdiffusion occurs at the phase boundary. The thickness of the diffusion zone depends on the styrene content of the SBR. For SBR samples with 40 and 23,5 wt.‐% styrene, zones of 50 and 15 nm thickness are found.
Preparation of bisupported catalysts for ethylene polymerization
Authors: Pasquet Véronique , Spitz Roger
Published: April 2003

SiO2‐MgCl2 supports were prepared thermally at moderate temperature. The preparation was improved by the use of an additive stabilizing MgCl2‐ammonium chloride. The best supports contain less than 5 wt.‐% Mg with about 2/3 of Mg as MgCl2 and keep most of the porous properties of the starting silica. Bisupported catalysts obtained after TiCl4 impregnation (2–4 wt.‐% Ti) present high activities and productivities in gas‐phase ethylene polymerization and copolymerization.
Ring‐opening metathesis polymerization of norbornenes with organosilicon substituents. Gas permeability of polymers obtained
Authors: Finkelshtein E. Sh. , Makovetskii K. L. , Yampol'skii Yu. P. , Portnykh E. B. , Ostrovskaya I. Ya. , Kaliuzhnyi N. E. , Pritula N. A. , Gol'berg A. I. , Yatsenko M. S. , Platé N. A.
Published: April 2003

Polymers of norbornenes with SiMe3 and Si(Me2)CH2SiMe3 groups were synthesized and mass transfer properties of the polymers were studied. Ring‐opening polymerizations of these monomers were realized in the presence of homogeneous WCl6‐based and heterogeneous Re2O7‐based metathesis catalysts. Introduction of silicon‐containing groups in the polynorbornene main chain results in a drastic increase of the permeability (P) and diffusion (D) coefficients for different biatomic and multiatomic gases. Comparison of polymers having SiMe3 and Si(Me2)CH2SiMe3 substituents shows lower permeability and diffusion coefficients in the latter case. The combination of transport properties (Pi values) and separation factors aij = Pi/Pj of the two new silicon‐containing polynorbornenes permits one to consider them as representatives of the most permeable and sufficiently permselective group of polymers. Transport properties of the polymers studied were analysed on the basis of the free volume approach.
Haloaldehyde polymers, 43.. Structure of 2‐bornyloxy‐terminated chloral oligomers
Authors: Ute Koichi , Oka Ken‐ichi , Kashiyama Masaharu , Hatada Koichi , Xi Fu , Vogl Otto
Published: April 2003

Oligomerization of trichloroacetaldehyde (chloral) was carried out with the lithium salt of (1 S, 2 R, 4 S)‐(–)‐borneol as the initiator. The unimer and dimer fractions consisted of two and four diastereomers, respectively; the individual isomers were isolated from the fractions by crystallization from methanol or by high performance liquid chromatography. The X‐ray single‐crystal analysis showed that the major isomer in the unimer fraction is the (R)‐form which has the acetal carbon in (R)‐configuration. The diastereomeric ratios were determined by 1H NMR as R/S = 57/43 for the unimers and RS/SR/RR/SS = 34/25/23/18 for the dimers. The conformations of the meso‐dimers [(R,R)‐ and (S,S)‐isomers] in the crystalline form corresponded to a half turn of the 41‐helix of isotactic polychloral, whereas the conformations of the racemo‐dimers (the (R,S)‐ and (S,R)‐isomers) were different from the helical structure in the crystal and in solution. The trimer fraction consisted of six of the eight possible diastereomers; among these isomers, the mm isomers (the (R,R,R)‐ and (S,S,S)‐isomers) were highly predominant. The amount of the (R,R,R)‐trimer formed was only slightly larger than that of the (S,S,S)‐isomer. (a) Part 42, cf. G. D. Jaycox, O. Vogl, J. Am. Chem. Soc., submitted.
Partiell acetylierte cellulose — synthese und bestimmung der substituentenverteilung mit hilfe der 1H NMR‐spektroskopie
Authors: Deus Carsten , Friebolin Horst , Siefert Egon
Published: April 2003

Partially acetylated cellulose was synthesized by homogeneous acidic and basic saponification of cellulose triacetate (fully acetylated cellulose) and by homogeneous acetylation of cellulose dissolved in molten N‐ethyl‐pyridinium chloride. The result of 1H NMR spectroscopic investigations was that acetylation and acid saponification lead to products with different esterification of the hydroxy groups at C2, C3 and C6 whilst basic saponification leads to uniform acetylation. Furthermore, the solubility of the cellulose acetates depends on the method of preparation.
Synthesis of SH‐ and NCO‐terminated thiocarbamate prepolymers
Authors: Klemm Elisabeth , Stöckl Cornelia
Published: April 2003

The addition reaction of 3,6‐dioxaoctane‐1,8‐dithiol with various diisocyanates, proceeding by addition of 1,4‐diazabicyclo[2.2.2.]octane as basic catalyst, was investigated. That way, NCO‐and SH‐terminated linear thiocarbamate telechelics (containing NHCOS‐groups) were synthesized. The structures were evaluated by IR and 13C NMR spectroscopy. Results show that side reactions of the NH protons with isocyanate (forming allophanates) can be excluded. The NCO‐terminated prepolymers are suitable to be used as participants in common isocyanate reactions. Thus, by treating with allyl alcohol, 2‐hydroxyethyl methacrylate or diallylamine, they can be transformed into telechelics with olefinic end‐groups (5, 6, 7). The products were characterized by their number‐average mol. wts. (VPO) and elemental analysis, and the expected chemical structures were confirmed by characteristic absorption bands.
Phase transitions in Nylons 8, 10 and 12 crystallized from solutions
Authors: Cojazzi Gianna , Fichera Anna Maria , Malta Viscardo , Zannetti Roberto
Published: April 2003

The peculiar structural modifications of Nylons 8, 10 and 12 prepared by crystallization from solutions and reported as α*, were studied by differential scanning calorimetry (DSC) and thermomicroscopy, supported also by some X‐ray diffraction (XRD) measurements. The results indicate that the phase transition shown by the α*‐forms of the Nylon 8–12 series exhibits the characteristics of a melting immediately followed by crystallization into γ‐form, rather than of a α* → γ solid‐solid transition. When the γ‐crystallization is concluded, the melting of this form takes place. DSC and XRD data demonstrate that the α* → γ transition is irreversible. The changes in the DSC traces of the Nylon 8 – 12 series were interpreted as indicative of a gradual stability increase of the α‐form in comparison with the corresponding α*‐form, depending on the increase of the number of methylene groups in the repeating unit.
Polymérisation induite sous irradiation laser visible, 4. Le système éosine/photoamorceur ultra‐violet/amine
Authors: Fouassier Jean P. , Chesneau Eliane
Published: April 2003

A study of the photoinitiating system eosin/UV‐photoinitiator/amine has been carried out through time resolved laser spectroscopy. Rates of polymerization of methyl methacrylate have been determined. A model for the photoinitiation step is proposed: the efficient role played by the UV‐photoinitiator is mainly explained in terms of interactions in the excited states; a small contribution to a decrease of the termination reactions of the growing polymer chains by eosinderived radicals is also shown.
Boundary between acceleration and suppression effects of α‐substituent on polymerization and copolymerization of ethyl α‐(halomethyl)acrylates
Authors: Yamada Bunichiro , Otsu Takayuki
Published: April 2003

Radical polymerization and copolymerization behaviour of ethyl α‐(halomethyl)acrylates was examined. Among them the bromomethylacrylate did not yield a homopolymer nor a copolymer because of fast chain transfer to the monomer. The chloromethylacrylate (ECMA) polymerized slower to form a lower molecular weight polymer than the fluoromethylacrylate (EFMA). In the copolymerizations with styrene and methyl methacrylate, ECMA was less reactive than EFMA owing to the steric effect of the slightly larger chloromethyl group. The reactivity of EFMA in the copolymerization was enhanced by the polar and resonance effects of the α‐substituent, prevailing over the steric effect. Characterization of the polymers by NMR spectroscopy and thermogravimetric analysis revealed the existence of steric congestion caused by the halomethyl groups in both polymers.
Anionic polymerization of fluorine‐containing vinyl monomers, 10. Studies on anionic polymerization reactivity of hexafluoro‐1,3‐butadiene
Authors: Narita Tadashi , Hagiwara Tokio , Hamana Hiroshi , Sezaki Mahito , Kezuka Namie , Nakagawa Kazuyuki , Nagai Akira , Nishimura Shin , Takahashi Akio
Published: April 2003

Hexafluoro‐1,3‐butadiene (HFBD), which can be hardly polymerized under radical polymerization conditions, was polymerized with caesium and rubidium compounds as initiators. Among the initiators examined, caesium fluoride, tert‐C4H9OCs, Cs+ (α‐methylstyrene)n2− Cs +, caesium naphthalene (C10H8°Cs+), tert‐C4H9ORb, Rb+ (α‐methylstyrene)n2−Rb+ and rubidium naphthalene (C10H8°Rb+) show surprisingly high activity. Polymerization of HFBD with typical anionic polymerization initiators possessing lithium and sodium as counter cations failed. The ionic radius of the counter cations may thus be important in the anionic polymerization of HFBD. The investigation of the initiation reaction supported the anionic polymerization mechanism. Poly(HFBD) obtained is a white powdery substance which is insoluble in any solvent. Poly(HFBD) possesses a 1,4 microstructure in the main chain as derived from solid‐state 13C NMR and infrared spectra. High thermostability of poly(HFBD) was confirmed by differential scanning calorimetric analysis.
Calculation of average molecular properties during nonlinear, living copolymerization
Authors: Macosko Christopher W. , Miller Douglas R.
Published: April 2003

Describing network formation during chainwise polymerization is more complex than for stepwise (condensation) systems. The kinetics of chain growth must be combined with probability laws for random linking between chains. This approach is used to derive molecular weight averages, gel point and sol fraction during living, anionic copolymerization of vinyl with divinyl monomers. Comparison of predicted molecular weight and gel point to experimental values from Worsfold (1970), Lutz, Beinert and Rempp (1982) and others indicate that a significant amount of intramolecular linking or cyclization occurs in this system.
Star polymers and block copolymers of 2‐oxazolines using chloroformates as initiators
Authors: Dworak Andrzej , Schulz Rolf C.
Published: April 2003

Polyfunctional chloroformates were applied to the polymerization of 2‐phenyl‐2‐oxazoline and 2‐methyl‐2‐oxazoline. The use of a trifunctional initiator, viz. the chloroformate of 2,2‐bis(hydroxymethyl)‐1‐butanol, led to three‐arm star polymers of 2‐oxazolines. Two macromolecular initiators, viz. poly(ethylene oxide) with two chloroformate end groups (α‐chloroformyl‐ω‐chloroformyloxypoly(oxyethylene)) with number‐average molar masses 350 g/mol ≤ M̄n ≤ 6000 g/mol and α‐chloroformyl‐ω‐methoxypoly(oxyethylene) with M̄n = 350 and 750 g/mol were applied for the synthesis of poly(2‐oxazoline)‐block‐poly(ethylene oxide)‐block‐poly(2‐oxazoline) and poly(2‐oxazoline)‐block‐poly(ethylene oxide) copolymers, respectively.
Oligomerization of oxiranes in the presence of phosphoric acid. Kinetics of model reaction
Authors: Biela Tadeusz , Kubisa Przemysław
Published: April 2003

The kinetics of the reaction between ethylene oxide and diethyl phosphoric acid (diethyl hydrogen phosphate) was studied in order to elucidate the mechanism of addition of oxiranes to phosphoric acid, the first reaction leading to phosphorus‐containing polyols. It was shown that the reaction proceeds by addition of the activated ethylene oxide molecule to the POH bond. Due to the low ionisation constant of the acid, activation via formation of the secondary oxonium ion plays a minor role, and the reaction proceeds mainly with participation of hydrogen‐bonded complexes.
Thermal transition and frequency response of the dielectric behaviour of some cellulosic substances
Authors: Abdel‐Moteleb Mohamed Magdy
Published: April 2003

The real part of the relative permittivity ϵ′r of some cellulosic materials contaminated with commercial impurities and NaCl (determined as weight percent ash contents), and that of the purified fibres, as well as their hydrolysed residues, free of such contaminations, was measured in the frequency range 102 Hz ≤ f ≤ 105 Hz and in the temperature range 283,15 K ≤ T ≤ 333,15 K. Additional measurements of the imaginary part of relative permittivity ϵ″r have been carried out in the same frequency and temperature ranges for hydrocellulose samples free of inorganic impurities and contaminated with NaCl. The results obtained show that the variation with temperature of the relative permittivity of the samples examined exhibits a change in slope in the vicinity of 303,15 K except for hydrocellulose samples free of impurities. They further show that the presence of inorganic contaminations has a significant effect on the magnitude of the relative permittivity and its variation with temperature, particularly at low frequency. In the case of samples contaminated with inorganic impurities, interfacial polarization is responsible for the anomalous dielectric behaviour observed with the examined samples.
Characterization and detection of polyanions by direct polyelectrolyte titration
Authors: Wassmer Karl‐Heinz , Schroeder Ulrich , Horn Dieter
Published: April 2003

A novel technique is described for the investigation of polyanions by direct polyelectrolyte titration. In connection with a specially developed phototitrator, an extremely high sensitivity can be reached using 3,6‐ionene bromide as cationic titrant and eriochrome black T as metachromatic indicator for end‐point detection. This enables both the determination of charge densities for polymer characterization as well as the detection of polymers in aqueous solution down to trace concentrations of 10 μg/L. Monovalent salt ions do not interfere with the titration up to concentrations of about 0,1 mol/L. Potential interference of divalent metal ions can be prevented by adding ethylenediaminetetraacetic acid (EDTA) as chelating agent. The applicability of the method was proved by measuring charge densities of poly(sodium acrylate) (NaPAA) in the concentration range of 0,01 to 10 mg/L and of poly(potassium vinyl sulfate) (KPVS). As expected, the charge density of NaPAA decreases with a pH decrease from 11 to 7, whereas the charge density of KPVS is independent of pH.
Triblock copolymers via thermal “macroiniferters”: Block copolymers of ethyl acrylate with methyl methacrylate or styrene
Authors: Nair Chethrappilly Reghunadhan , Richou Marie Christine , Clouet Gilbert
Published: April 2003

The concept of macro iniferter (MI) was applied to realize the synthesis of triblock copolymers of ethyl acrylate (EA) with styrene (St) or methyl methacrylate (MMA), with EA forming the end blocks. The syntheses involved 3 steps. Secondary amine terminated poly(ethyl acrylate) was synthesisted by polymerization of EA in presence of butyl‐(2‐mercaptoethyl)ammonium chloride as a functional chain‐transfer agent. The macroamine so obtained was converted to the macrothiuram disulfide by reaction with CS2 and I2. Thermal polymerization of MMA or St in presence of this macroiniferter led to the respective triblock copolymers. The kinetics of polymerization of MMA and styrene using MI and two different chain lengths was done in limited concentration ranges. The kinetic parameters indicated that the iniferter action was not affected by the incorporation of the thiuram disulfide groups in the polymer backbone. Triblock copolymers of differing block lengths of hard and soft segments could be prepared by varying the chain length of the macroamine and the concentration of the iniferter in the reaction system. The copolymers were characterized by GPC analysis and spectral or elemental analyses. In the case of St, analysis showed formation of perfect triblocks, whereas for MMA, tendencies to form diblocks were observed on increasing the chain length of the iniferter‐forming block. DSC analyses showed demixing of the soft EA block and the hard central blocks.
13C NMR characterization of ethylene oxide/propylene oxide adducts
Authors: Gronski Wolfram , Hellmann Günther , Wilsch‐Irrgang Anneliese
Published: April 2003

Analytical studies are essential if ethylene oxide (EO)/propylene oxide (PO) adducts are to be comprehensively characterized. Because hardly any detailed information on their structure has previously been available, studies were carried out to assess the value of the information obtained by 13C NMR spectroscopy. The complex identification of the signals undertaken permitted detailed conclusions to be drawn about the structure of these products. The following structure parameters can be determined: Differentiation between random and block copolymers, persistence ratio (measure of the deviation from a fully random statistics), mean sequence lengths of EO/PO sequences, number of blocks per 100 monomeric units, triad probabilities, and starter and end‐groups.
Lichtinduzierte polymer‐ und polymerisationsreaktionen, 44. Zur kinetik der radikalischen photopolymerisation mehrfunktioneller acrylate in polymeren bindemitteln
Authors: Timpe Hans‐Joachim , Strehmel Bernd
Published: April 2003

With calorimetric measurements the kinetics of the free‐radical polymerization of various diacrylates in several polymeric binders have been investigated. The reaction was initiated by radicals formed through photolysis of α‐isopropoxydeoxybenzoin. In each case, the polymerization rate depends on the conversion degree. Mainly, this fact results from changes in the termination mechanism of the polymerization chain reaction. By means of the light intensity exponent such mechanistical changes can be quantitatively followed. Both, the results obtained by stationary and non‐stationary irradiation experiments lead to the same conclusions. The properties of the polymeric binders possess a stronger influence on the kinetics compared with the structural changes of the diacrylates used.
Polymer‐bound porphyrins and their precursors, 10. Syntheses and photoredox properties of water‐soluble polymers with covalently bonded zinc tetraphenylporphyrin
Authors: Wöhrle Dieter , Paliuras Mihail , Okura Ichiro
Published: April 2003

Positively or negatively charged as well as uncharged water‐soluble polymers 2a – d, 6a – c, 7a – e and positively charged crosslinked polymers 3a, b containing covalently bonded moieties of the substituted zinc tetraphenylporphyrin 1a were prepared. In addition, positively charged polymers 4a – c with covalently bonded viologen, and 5 with covalently bonded 1a and viologen at one and the same polymer chain were obtained. The triplet lifetimes in water of different 1a‐ bonded linear polymers 2a – d, 6a – c, and 7a – e are not influenced by the kind of polymer environment. The photoredox activites in water of the polymers containing moieties of 1a in the presence of methylviologen and 2‐mercaptoethanol under irradiation with visible light are higher as compared with low‐molecular‐weight, positively or negatively charged porphyrins 1b, c. The influence of the amount of polymer‐bonded porphyrin and the molecular weight of a polymer on the photoredox activity is exemplarily described. Polymers 4a – c with viologen moieties as acceptor are more efficient than the low‐moleular‐weight methylviologen. The highest photoredox activities were observed with polymer 5 containing moieties of 1a and viologen. In the presence of the enzyme hydrogenase formation of hydrogen occurs.
Structural modifications of poly(1,4‐phenylenevinylene) to soluble, fusible, liquid‐crystalline products
Authors: Martelock Heidi , Greiner Andreas , Heitz Walter
Published: April 2003

The synthesis, solubility, and thermal behavior of soluble, fusible, liquid‐crystalline derivatives of poly(1,4‐phenylenevinylene) (1) is described. The improved solubility and fusibility were accomplished by reducing interchain interactions without change of the rigid rod‐like character. The interchain interactions were lowered by decreasing the structural regularity of the repeating units. The synthesis of derivatives of 1 was accomplished by the palladium‐catalyzed coupling of dihalogenoarenes and ethylene to avoid cis‐vinylene units. Irreversible crosslinking was observed from fusible products on annealing above the softening point.
1H and 13C NMR sturctural investigation of some titanium alkoxide‐magnesium halide complexes as Ziegler‐Natta catalyst precursors
Authors: Abis Luigi , Bacchilega Giancarlo , Spera Silvia , Zucchini Umberto , Dall'Occo Tiziano
Published: April 2003

Several [Ti2(OR)8MtX2]2 complexes were prepared from MtX2 (Mt = Mg, Zn; X = Cl, Br, I) and Ti(OR)4 (R = ethyl, propyl, butyl). 1H and 13C NMR in toluene‐d8 solution and cross‐polarization/magic‐angle spinning (CP/MAS) 13C NMR spectra were taken of some complexes. The obtained spectra allowed to deduce their molecular structure in solution and to compare them with that of [Ti2(OC2H5) 8Cl]2Mg2Cl2 obtained by single‐crystal X‐ray diffraction analysis.
Polymerization in inverse microemulsions, 2. Copolymerization of water‐ and oil‐soluble monomers initiated by 2,2′‐azoisobutyronitrile
Authors: Vas̆ková Viera , Juranic̆ová Viera , Barton̆ Jaroslav
Published: April 2003

Copolymerization of the water‐soluble monomer acrylamide (AAM) with the oil‐soluble monomer methyl methacrylate (MMA) and/or styrene (St) in inverse microemulsion initiated with 2,2′‐azoisobutyronitrile was studied. It was found that the overall polymerization rate increases with increasing mole fraction of AAM in the comonomer mixture, while the composition of the product changes only slightly. The copolymerization process is a typical “dead‐end” polymerization where the limiting conversion corresponds to the AAM concentration in the comonomer mixture. The concentration of MMA, resp. St at the locus of copolymerization was calculated as a function of the AAM mole fraction in the comonomer mixture.
Thin film processing of nonlinear optical materials, 2. Comb‐like polymers containing nonlinear optical active pendant groups
Authors: Mandal Braja K. , Takahashi Toru , Maeda Mutsumi , Kumar Sai , Blumstein Alexandre , Tripathy Sukant
Published: April 2003

The synthesis and characterization of new homopolymers and copolymers containing π‐extended (azomethine) active moieties separated by flexible methylene spacers are reported. All synthesized monomers and polymers show spectroscopic properties (nuclear magnetic resonance, infrared, ultraviolet) in accordance with the proposed structures. The inherent solubility of the polymers in common organic solvents permits the determination of the molecular weight distribution from gel‐permeation chromatography. The thermal characteristics of the polymers are also described.
Polyimides derived from ether ketone diamines
Authors: Rao Vattikuti L. , Bijimol Jacob
Published: April 2003

Polyimides were prepared from the reaction of two aromatic dianhydrides with two diamines containing carbonyl and ether connecting groups between the aromatic rings. The diamines were prepared from the reaction of 4‐aminophenol or (3‐aminophenol) with an activated aromatic difluoro compound (4,4′‐difluorobenzophenone) in the presence of potassium carbonate. Some of these polyimides were shown to be semicrystalline as evidenced by wide‐angle X‐ray diffraction. Glass transition temperatures were observed between 203 and 242°C. All polyimides were found to be thermally stable up to 400–450°C with a char yield of about 50–60% at 900°C. The effect of the structure on the properties of polyimides, such as crystallinity, glass transition temperature and thermal behaviour, is discussed.
Surface tensions of liquid‐crystalline and isotropic polymer melts
Authors: Uzman Mehmet , Song Bihai , Runke Thomas , Cackovic Hinko , Springer Jürgen
Published: April 2003

The surface tensions (γ) of a branched polyethylene and two side‐group liquid‐crystalline (lc) polyacrylates were measured in the isotropic, nematic and smectic states by the pendant‐drop method. The surface tension vs. Temperature characteristics of the lc polyacrylates studied show anomalous behaviour. The slope in the isotropic state is initially negative but changes its sign near the isotropic‐nematic transition. The increase of γ with decreasing temperature is regained in the nematic phase, until at the nematic‐smectic transition the surface tension of the lc polymers discontinuously jumps to higher values and shows a very low temperature coefficient. The observed features have been found to be partly in agreement with the results of surface tension measurements on low‐molar‐mass liquid crystals, which indicates that the surface properties of the lc polymers are governed by the mesogenic side groups.
Dynamic fourier transform infrared spectroscopy of liquid‐crystalline elastomers
Authors: Bräuchler Martin , Boeffel Christine , Spiess Hans Wolfgang
Published: April 2003

The influence of mechanical deformation on the orientation behaviour of the phenyl benzoate mesogenic groups in polyacrylate‐ and polymethacrylate‐based liquid‐crystalline (l. c.) elastomers with spacers of six methylene units is investigated as a function of temperature and time by means of linear‐dichroism infrared spectroscopy. The mesogens in the polymethacrylate elastomers preferably align perpendicular to the stretching direction and show a biaxial phase with homeotropic orientation. The changes in sample geometry, especially the film‐thickness variation during deformation, are studied. The orientation behaviour of the mesogens in the polyacrylate elastomers is different in the nematic and smectic phase. On stretching, the mesogens align parallel in the nematic and perpendicular to the stretching direction in the smectic phase. The orientation of a film stretched in the smectic phase, however, changes to be parallel to the stretching direction if its temperature is raised once above the smectic‐to‐nematic transition temperature. The dynamics of reorientation of the mesogens strongly depends on temperature. With high mobility of the mesogens no phase lag between deformation and orientation can be detected on a timescale of 100 ms. The orientation behaviour of l. c. elastomers is very complex and depends on many parameters, each of which is important.
Synthesis of poly(2‐ethyl‐2‐hydroxymethyltrimethylene carbonate)
Authors: Kühling Steffen , Keul Helmut , Höcker Hartwig , Buysch Hans‐Josef , Schön Norbert
Published: April 2003

2‐Ethyl‐2‐hydroxymethyltrimethylene carbonate (5‐ethyl‐5‐hydroxymethyl‐1,3‐dioxan‐2‐one) (1) was treated with trimethylsilyl chloride, benzyl chloroformate and phenyl isocyanate to give the corresponding 5,5‐disubstituted 1,3‐dioxan‐2‐ones 2, 3 and 4. These monomers were subjected to anionic ring‐opening polymerization reactions with lithium alcoholates as initiators. The polymers obtained usually exhibit linear structure; under special conditions slightly branched polymers were obtained. Poly(2) and poly(3) were subjected to polymer‐analogous reactions—hydrolysis and hydrogenation—by which the protective groups are removed and poly(1) was obtained. The hydroxyl groups in poly(1) are susceptible to a polymer‐analogous reaction. Poly(4) obtained by reaction of poly(1) with phenyl isocyanate was identical with poly(4) obtained by ring‐opening polymerization of the corresponding monomer 4. All these new monomers were characterized by means of 1H and 13C NMR spectroscopy as well as elemental analysis. The polymers were analyzed with respect to their primary structure, their molecular weight and molecular weight distribution. The thermal properties of some of the polymers are discussed.
Cationic polymerization of methoxyallene with Lewis acids
Authors: Takahashi Tatsuya , Yokozawa Tsutomu , Endo Takeshi
Published: April 2003

The cationic polymerization of methoxyallene (1) was carried out with some Lewis acids at −50°C in dichloromethane. BF3OEt2 was found to be an effective catalyst for the cationic polymerization of 1. From analyses of 1H and 13C NMR spectra, the obtained polymers consist of units with the 1,2‐double bond of 1 being opened, although the 2,3‐double bond is consumed also to an amount of 24 to 43 mol‐%. This decrease in 2,3‐double bond content in the polymer may be attributed to intramolecular cyclization of the propagating cation and/or the intermolecular reaction of the propagating cation with polymer to produce a graft polymer. Moderately polar solvents such as dichloromethane proved to be best suited for obtaining polymers with high double bond content.
Polymérisation induite sous irradiation laser visible, 5. Le système éosine/amine/sel de iodonium
Authors: Fouassier Jean P. , Chesneau Eliane
Published: April 2003

A study was conducted of the excited states of the combination eosine/amine/iodonium salt through time‐resolved laser spectroscopy, of the photolysis products formed under light exposure, and of the rates of polymerization. It allows the process to be precised and discussed. It is apparent that the iodonium salt has no effect on the initiation step of the polymerization reaction but sharply decreases the termination reactions. The formation of a complex between eosine and the iodonium salt is suggested; this complex is destroyed in the presence of amine.
Optical investigations on a liquid‐crystalline side‐chain polymer with biaxial nematic and biaxial smectic A phase
Authors: Leube Hartmann Friedrich , Finkelmann Heino
Published: April 2003

A liquid‐crystalline side‐chain polymer with laterally incorporated naphthalene groups in the mesogenic moiety is investigated in binary mixtures with an optical uniaxial low‐molar‐mass liquid crystal. Mixtures with up to 50 mol‐% content of the monomeric liquid crystal show a biaxial nematic phase. At lower temperatures a new biaxial smectic phase is observed, which corresponds to the smectic A phase. The angles between the optical axes are measured in dependence of temperature and mixture composition. Starting from the neat polymer, the angles decrease in the nematic as well as in the smectic phase with increasing mole fraction of the uniaxial liquid crystal. From the results a phase transformation uniaxial nematic to biaxial nematic can be inferred.
Transitional properties of liquid‐crystalline side‐chain polymers derived from poly(p‐hydroxystyrene)
Authors: Attard George S. , Dave Jayrang S. , Wallington Andrea , Imrie Corrie T. , Karasz Frank E.
Published: April 2003

A series of liquid‐crystalline polystyrene derivatives with ω‐(4‐(4‐fluorophenylazo)phenoxy)‐alkoxy pendant groups have been synthesized and characterized. Homologues with four or more methylene units in the spacer chain exhibit smectic liquid‐crystalline phases, while the homologue with three methylene units forms an amorphous glass. The smectic A‐isotropic (SA‐I) transition temperatures show a marked odd‐even effect as a function of the parity of the spacer chain. This odd‐even behaviour is also found in the variation of ΔS/R at the SA‐I transition across the series. A marked hysteresis between the transition temperatures determined on heating and the transition temperatures determined on cooling is observed. A molecular interpretation of these phenomena is proposed.
A study of interface reaction during composite formation between polybutadiene epoxide and highly dispersed silica or alumina
Authors: Hortschansky Peter , Heublein Günther
Published: April 2003

This paper reports on interface reactions between polybutadiene epoxide (PBDE) and highly dispersed oxides (SiO2, Al2O3) during composite formation. Mechanisms of these reactions are discussed in dependence on the nature and concentration of active surface species (Brönsted‐ and Lewis‐acid sites). Conclusions regarding the macroconformations of chemisorbed PBDE in the system PBDE/SiO2 can be drawn by determination of interface conversion between epoxide and silanol groups.
Polymers with sulfinyl and oxyethylene constitutional units as catalysts of nucleophilic substitution reactions
Authors: Valter Bohumír , Masař Bohumil , Janout Václav , Hrudková Hana , Čefelín Pavel , Tur Dzidra R. , Vinogradova Svetlana V.
Published: April 2003

The catalytic activity of polystyrene‐ and polyphosphazene‐supported monosulfoxides and oligo(oxyethylene)s was investigated in the Williamson alkylation of sodium phenoxide with 1‐bromooctane in 1,4‐dioxane at 75°C. Polymer‐supported monosulfoxides are less efficient than low‐molecular‐weight species. Polymer‐supported oligo(oxyethylene)s with pseudo‐crown‐ether structures show a polymer effect, which may even be stressed by the presence of onium units in the side chains.
Redox‐chemical investigations of soluble oligo(p‐phenylene)s
Authors: Bohnen Angelika , Heitz Walter , Müllen Klaus , Räder Hans‐Joachim , Schenk Rainer
Published: April 2003

The chemical and electrochemical reductions of two series of oligo(p‐phenylene)s with different substitution patterns are investigated. The resulting anionic species are characterized on the one hand using NMR spectroscopy and quenching experiments obtaining dianions in the case of terphenyls and quaterphenyls. On the other hand, cyclic voltammetric experiments were carried out with the results that compounds with substitution only in the terminal rings behave as typical conjugated oligomers, and substituents in the middle rings disturb the conjugation and alter the mechanism of electron transfer. Further, the charge distribution, the stereodynamic behaviour and the redox potentials are examined as a function of chain length and substitution. The reduction of the title compounds shows that only the substitution of terminal phenyl rings leads to suitable model compounds for the doping of poly(p‐phenylene).
Modification of silicone surface by graft polymerization of acrylamide with corona discharge
Authors: Okada Toshiyuki , Ikada Yoshito
Published: April 2003

In order to render the surface of silicone hydrophilic without changing its bulk properties, acrylamide was grafted onto its surface. A silicone sheet was first treated with a corona discharge in air to introduce peroxides onto the surface. The concentration of peroxide introduced to the surface was determined using 2,2‐diphenyl‐1‐picrylhydrazyl and the maximum concentration was about 1,80 · 10−8 mol/cm2 when the corona discharge treatment was performed with 9 or 15 kV. Graft polymerization was allowed to proceed by heating the aqueous solution of the monomer together with the immersed silicone pretreated with the corona discharge. It was critical to throughly deaerate the silicone before and after the corona discharge treatment. Unless deaeration was sufficient, graft polymerization did not occur, irrespective of heating. The friction coefficient of the poly(acrylamide)‐grafted silicone decreased drastically, even if only a small amount of poly(acrylamide) was grafted onto the surface of the silicone. Collagen could be immobilized covalently using a water‐soluble carbodiimide, 3‐dimethylaminopropyl(ethyl)‐carbodiimide hydrochloride, when the grafted poly(acrylamide) chains were converted to poly(acrylic acid) by alkaline hydroysis, in order to introduce carboxyl groups. The maximum concentration of collagen immobilized was 4,0 μg/cm2.
The measurement of concentration and stability of weak acids and a study of the ionisation of polysaccharides using buffer capacity curves
Authors: Petzold James C. , Herrington Thelma M.
Published: April 2003

A technique using buffer capacity has been developed for evaluating the approximate pK values of the stability constant K, of polyelectrolytes. The technique has been applied to hemicellulose extracted from woodpulp (pK ≈ 3,9 (0,1 M NaCl)) and dextran (pK = 13,55 ± 0,2 (2 M NaCl)). Verification of the method has been obtained by applying it to acetic acid (pK = 4,55 ± 0,02 (0,1 M NaCl), pK = 4,70 ± 0,02 (0,001 M NaCl)) and glucose (pK = 12,00 ± 0,05 (2 M NaCl)). Glucose was found to turn peppermint green in NaOH solutions. At least 50% of the surface charge of woodpulp was found to originate from its hemicellulose coating.
Living cationic polymerization of vinyl monomers by organoaluminium halides, 7. Effect of basicity and steric hindrance of added esters on the living polymerization of isobutyl vinyl ether with C2H5AlCl2
Authors: Aoshima Sadahito , Shachi Kenji , Kobayashi Eiichi , Higashimura Toshinobu
Published: April 2003

The living cationic polymerization of isobutyl vinyl ether (IBVE) with 1‐(isobutoxy)ethyl acetate (1)/C2H5AlCl2 as initiating system in hexane at +40°C in the presence of carboxylates was investigated in regard to the effect of the basicity and the steric hindrance of the added esters on the rate and living nature of the polymerization. The effect of the basicity was evaluated by use of four p‐substituted ethyl benzoates (XC6H4COOC2H5; X: CH3O, CH3, H, Cl). Despite of the difference in basicity, all the benzoates gave living polymers with narrow molecular‐weight distributions (ratios of weight‐ to number‐average molecular weights Mw/Mn ≤ 1,1), whereas the polymerization rate depends on the p‐substituents as follows: CH3O < CH3 < H < Cl. Another series of experiments showed that the steric environment around the carbonyl group also affects the polymerization rate. Namely, using carboxylates with various carbonyl substituents (RCOOCH3; R: CH3, C2H5, (CH3)2CH, (CH3)3C), the polymerization rate increases with increasing bulkiness of the substituent R in the order: (CH3)3C > (CH3)2CH > C2H5 > CH3. These electronic and steric effects are consistent with the stabilization of the carbocation by the nucleophilic interaction of added bases. Fast living polymerization of IBVE can be obtained using the initiating system 1/C2H5AlCl2 in the presence of methyl chloroacetate, an ester with a strongly electron‐withdrawing group.
Conformation of phenyl rings in the helical chain polymer poly(triphenylmethyl methacrylate)
Authors: Wang Yuechuan , Ding Mengxian , Wang Fosong
Published: April 2003

The conformation of phenyl rings in the side groups of the helical chain polymer poly(triphenylmethyl methacrylate) (1) in solution was studied by spectroscopic methods. According to the Raman spectrum the phenyl rings of 1 and triphenylmethyl methacrylate in solution have the same depolarization ratio at 1 002 cm−1. The electronic spectra (ultraviolet and fluorescence) of 1 are similar to those of model substances, except for the “red shift” of the spectra of about 5 nm. It was concluded that the phenyl rings can rotate around the phenylC bond.
Coordination polymerization of lactides, 2. Microstructure determination of poly[(L,L‐lactide)‐co‐(ε‐caprolactone)] with 13C nuclear magnetic resonance spectroscopy
Authors: Kasperczyk Janusz , Bero Maciej
Published: April 2003

A detailed analysis of the structure of poly[(L,L‐lactide)‐co‐(ε‐caprolactone)]

IUPAC‐preferred name is dilactide:

was performed by means of high resolution 13C NMR (75 MHz) spectroscopy. The polyesters were obtained using various comonomer ratios and initiators aluminium tris(acetylacetonate) or the system Al(C2H5)3 + Zn(C2H5)2 + H2O. Signals in spectra were assigned to appropriate structural sequences. Two types of chain structure containing different sequences and depending on the initiator used in copolymerization were found.
Fabrication biocompatible de microcapsules par polymérisation ensemencée autour de microsphères d'agarose
Authors: Dupuy Bernard , Cadic Christine , Rouais François , Baquey Charles , Ducassou Dominique
Published: April 2003

A new process for microencapsulating cells is described. Cells in solution in agarose were extruded from a syringe into a paraffin‐oil containing medium. Solid microspheres were produced when the agarose gelled. A rigid interface around each bead was produced by polymerization of a latex‐seeded aqueous solution of a mixture of 5 wt.‐% acrylamide and 0,25 wt.‐% N,N‐methylenediacrylamide. Cell viability was demonstrated by radioimmunoassay of prolactin liberated from encapsulated pituitary cells.