bluuebunny/crossref_metadata_2025_split huggingface dataset:
A kinetic study of the emulsion copolymerization of N,N′‐methylenebis(acrylamide) and an unsaturated polyester
Authors: Capek Igńc , Funke Werner 
Published: April 2003

AbstractThe emulsion copolymerization of N,N′‐methylenebis(acrylamide) (MBA) and an unsaturated polyester (UP) initiated by potassium peroxodisulfate was kinetically investigated at 50°C by conventional gravimetric and dilatometric methods. The rate of polymerization, the size of latex particles and the number of polymer particles were determined as a function of MBA concentration. The rate of MBA polymerization was found to be proportional to the 0,8th (at 0–15% conversion) and 0,9th (at 20–40% conversion) order with respect to [MBA] at 0,0231 mol · dm−3 of UP. The values of the reaction order on the monomer concentration are discussed in terms of homogeneous and emulsion polymerization and crosslinking effects. The rate of UP polymerization in the emulsion copolymerization of MBA and UP does not depend on the total monomer concentration. The specific rate of MBA (or UP) polymerization increases with increasing monomer concentration and reaches a maximum at a certain concentration of monomer. The size of polymer particles decreases and the number of particles increases with increasing UP fraction. The stability of polymer particles increases with increasing UP fraction in the monomer feed. The ratio (kp/kt0,5)0 of the relative rate constants for propagation kp and termination kt calculated for the MBA or UP polymerizations at zero conversion increases with increasing MBA concentration. The growth of the polymer particles proceeds via polymerization in particles and by interparticle crosslinking reactions.
Crystallinity of uniform tri(oxyalkylene)s
Authors: Bedells Alison D. , Booth Colin , Viras K. 
Published: April 2003

AbstractThe crystallinities of uniform $ {\rm HO}\rlap{--} [\left( {{\rm CH}_2 } \right)_x {\rm O\rlap{--} ]}_{\rm 3} {\rm H} $ with x = 3 to 6, were investigated by small‐angle X‐ray diffraction, low‐frequency Raman spectroscopy, infra‐red spectroscopy and differential scanning calorimetry. It is shown that the C4 to C6 trimers adopt a trans‐planar conformation in their layer crystals, whereas the C3 trimer adopts a different chain conformation. In all cases the hydroxy end groups are extensively hydrogen bonded.
Oligomerization of 1‐hexene initiated by Zr(OnPr)4‐AlEt2Cl, 2. Mechanistic aspects
Authors: Liu Hua Qin , Deffieux Alain , Sigwalt Pierre 
Published: April 2003

AbstractThe mechanistic aspects of 1‐hexene oligomerization, initiated by Zr(OnPr)4‐AlEt2Cl at 20°C, are discussed on the basis of the product structures and distributions, the stability and reactivity of Mt‐alkyls (Mt = metal) formed during 1‐hexene oligomerization, the reaction behaviour of an internal olefin (cis‐2‐hexene) and the investigation of interactions between Zr (OnPr)4‐AlEt2Cl. After comparing the different possible initation routes for 1‐hexene oligomerization, a mechanism via insertion of 1‐hexene into Al‐alkyl bonds activated by zirconium is proposed. It was found that the olefin addition is not regiospecific. Primary addition into a linear alkyl‐metal bond leads to an olefin insertion, whereas secondary addition only leads to elimination; when α‐ or β‐ branched alkyl‐metal bonds are involved, only transfer to monomer takes place.
Synthesis and properties of polyamides derived from anhydro‐ and dianhydroalditols
Authors: Thiem Joachim , Bachmann Frank 
Published: April 2003

AbstractThe three isomeric 1,4:3,6‐dianhydroalditols with D‐gluco‐ (2), D‐manno‐ (11) and L‐ido (17) configuration and both 1,4‐anhydroalditols with threo (22) and erythro (27) configuration were efficiently transformed into the corresponding diamino derivatives. Interfacial polycondensation of these chiral heterocyclic diamines with purchasable aromatic and aliphatic carboxylic acid chlorides gave polyamides 35 and 36a–f, 37, 38 and 39a–d. The polymers were characterized using IR and 1H/13C NMR spectroscopy. Number‐average molecular weights were obtained from gel‐permeation chromatography to be M̄n ≈ 5000–25000 corresponding to a number‐average degree of polymerization up to P̄n ≈ 100. Inherent viscosities were measured, and differential scanning calorimetry gave information on the thermal properties of the polymers.
Kinetic and ESR studies of the radical‐initiated polymerization of N‐(2,6‐dimethylphenyl)itaconimide
Authors: Sato Tsuneyuki , Takarada Akira , Tanaka Hitoshi , Ota Tadatoshi 
Published: April 2003

AbstractThe polymerization of N‐(2,6‐dimethylphenyl)itaconimide (1) with azoisobutyronitrile (2) was studied in tetrahydrofuran (THF) kinetically and spectroscopically with the electron spin resonance (ESR) method. The polymerization rate (Rp) at 50°C is given by the equation: Rp = K[2]0,5 · [1]2,1. The overall activation energy of the polymerization was calculated to be 91 kJ/mol. The number‐average molecular weight of poly(1) was in the range of 3500–6500. From an ESR study, the polymerization system was found to involve ESR‐observable propagating polymer radicals of 1 under the actual polymerization conditions. Using the polymer radical concentration, the rate constants of propagation (kp) and termination (kt) were determined at 50°C. kp (24–27 L · mol−1 · s−1) is almost independent of monomer concentration. On the other hand, kt (3,8 · 104–2,0 · 105 L · mol−1 · s−1) increases with decreasing monomer concentration, which seems mainly responsible for the high dependence of Rp on monomer concentration. Thermogravimetric results showed that thermal degradation of poly(1) occurs rapidly at temperatures higher than 360°C and the residue at 500°C was 12% of the initial polymer. For the copolymerization of 1 (M1) with styrene (M2) at 50°C in THF the following copolymerization parameters were found; r1 = 0,29, r2 = 0,08, Q1 = 2,6, and e1 = +1,1.
Liquid‐crystalline polymers containing macrocyclic polyethers, 2. Side‐chain liquid‐crystalline copolysiloxanes containing mesogenic units based on 1,3‐dioxane‐2,5‐diyl and benzo[15]‐crown‐5
Authors: Hsiue Ging‐Ho , Wen Jiunn‐Shyang , Hsu Chain‐Shu 
Published: April 2003

AbstractSynthesis and characterization of a series of copolysiloxanes containing crown ether and trans‐1,3‐dioxane based mesogens are presented. The phase behaviour of the copolymers was studied using differential scanning calorimetry and optical polarizing microscopy and compared with the phase behaviour of the corresponding copolysiloxane‐containing crown ether and biphenyl‐based mesogens. Two copolysiloxanes containing trans‐2‐(benzo‐[15]crown‐5)‐5‐(ω‐alkan‐1‐yloxy)‐1,3‐dioxane side groups present no liquid‐crystalline behaviour. The other four copolysiloxanes exhibit a nematic mesophase and undergo side‐chain crystallization at low temperature. Two of the four copolysiloxanes which contain a trans‐1,3‐dioxane‐2,5‐diyl group in the mesogenic unit present lower isotropization temperatures and narrower mesophase ranges than the other two. This result reveals that replacing a phenyl ring in the mesogenic unit of a liquid‐crystalline polymer by a trans‐1,3‐dioxane ring will decrease the thermal stability of the mesophase exhibited by this polymer.
Mechanism of whisker growth of poly(4‐hydroxybenzoate)
Authors: Taesler Christian , Petermann Jürgen , Kricheldorf Hans R. , Schwarz Gert 
Published: April 2003

AbstractNeedle‐like crystals (whiskers) of poly(4‐hydroxybenzoate) were prepared by thermal condensation of 4‐acetoxybenzoic acid in Marlotherm‐S® at 300, 350 and 400°C. In addition to the temperature, also reaction time and concentration were varied. Wide‐angle X‐ray scattering powder patterns show that the “300°C whiskers” contain nearly equimolar fractions of orthorhombic modifications I and II, “350°C whiskers” and “400°C whiskers” only consist of modification I. Differential scanning calorimetry measurements revealed a phase transition at 325, 346 and 359°C for the “300°C”, “350°C” and “400°C whiskers”, respectively. Electron microscopy shows that with increasing conversion the thickness of the whiskers passes through a maximum. The previously proposed whisker growth model along a central screw was not confirmed and a new crystal growth model is proposed.
Catalytic hydrolysis of phenyl esters in cyclodextrin/poly(allylamine) systems
Authors: Seo Toshihiro , Kajihara Taketoshi , Miwa Keishi , Iijima Toshiro 
Published: April 2003

AbstractThe hydrolysis of phenyl esters in systems containing poly(allylamine) {poly[1‐(aminomethyl)‐ethylene]} (1) carrying pendant β‐cyclodextrin (CD) moieties with selective inclusion ability was investigated. In the mixture of 1 (or its N‐benzyl derivative) with CD, CD retards the hydrolysis of p‐nitrophenyl acetate. It was estimated that the substrate which is included in CD is difficult to be attacked by 1, and in the case of N‐benzylated poly(allylamine) there occurs competitive inhibition with CD. On the other hand, poly(allylamine) containing covalently bound CD (2) has much higher hydrolysis activity for various phenyl esters than 1 and shows a kinetics of Michaelis‐Menten type. In the case of p‐nitrophenyl hexanoate and p‐nitrophenyl benzoate, high substrate inclusion and a change in catalytic ability were observed. It was also shown that polymer 2 develops a remarkable catalytic effect for p‐nitrophenyl L‐N‐acetylphenylalanine ester for which CD and 1 alone show no catalytic activity. It is suggested that a highly selective recognition of the substrate by the CD side group and an effective cooperative action between (1) amino group and CD, and (2) two neighbouring CD rings on the polymer chains occur.
Synthesis and characterization of a homologous series of chiral smectic C side‐chain polymers
Authors: Messner Bernfried , Finkelmann Heino 
Published: April 2003

AbstractThe synthesis and characterization of a homologous series of liquid‐crystalline side‐chain polymers with a chiral smectic C phase are described. The polymer backbone consists of methacrylate monomeric units which link the mesogenic moieties of the chiral cinnamic acid 2S‐ (−)‐4‐(2‐chloro‐4‐methylpentanoyloxy)phenyl ester via a flexible spacer of six to eleven CH2 groups. The influence of this variation on this variation on transition temperatures, phase structure and range of the l. c. phases is studied. In contrast to the monomers, the chiral smectic C phase of the polymers is significantly broadened with respect to the temperature regime and can be vitrified in the glassy state.
Synthesis of a liquid‐crystalline polysiloxane with a diol mesogen in the side chain
Authors: Staufer Günter , Lattermann Günter 
Published: April 2003

AbstractThe synthesis and thermal behaviour of a cis,cis‐(3,5‐dihydroxycyclohexyl) 3,4,5‐tris(alkoxy)‐benzoate, functionalized by one terminal C‐C double bond is described. Its mesophase of the hexagonal columnar type is formed by a “supramolecular” unit, consisting of six single molecules aggregated via hydrogen bonding. Subsequently, a liquid‐crystalline side‐chain polymer with a siloxane backbone was synthesized. Its mesophase behaviour, investigated by means of differential scanning calorimetry (DSC) measurements and polarizing microscopy, is discussed.
Synthesis and properties of well‐defined multiblock copolymers: polystyrene‐block‐polydimethylsiloxane
Authors: Dems Andrzej , Strobin Grażyna 
Published: April 2003

AbstractPolystyrene (PS)‐polydimethylsiloxane (PDMS) triblock copolymers with well‐defined block lengths and silanol reactive end‐groups were synthesized by anionic polymerization as prepolymers for condensation reactions. Multiblock PS‐PDMS copolymers characterized by molecular and chemical homogeneity could be obtained either by self condensation of the silanol groups of by reaction with dichlorodimethylsilane. The kinetic constants, the activation energy, the extent of reaction and the molecular characteristics of the multiblock copolymers were determined as a function of the molecular weight of the prepolymer, the water content of the reaction medium and the concentration of HCl acting as catalyst in the dehydration reaction. The kinetic constants and the ultimate extent of the reaction could be correlated to the molecular weight of the prepolymer and to the viscosity of the reaction medium. DSC measurements of the multiblock copolymers show clearly the presence of two‐phase materials with mechanical properties depending on the PDMS content.
Effect of SnCl4 on the radical‐initiated polymerization of diethyl itaconate: Kinetical and ESR studies
Authors: Sato Tsuneyuki , Nakamura Hiroyuki , Tanaka Hitoshi , Ota Tadatoshi 
Published: April 2003

AbstractThe effect of SnCl4 on the polymerization of diethyl itaconate (1) with dimethyl 2,2′‐azoisobutyrate (2) in benzene was investigated kinetically and ESR spectroscopically. The polymerization rate (Rp) at 50°C shows a flat maximum on varying the SnCl4 concentration. The molecular weight of the resulting polymer decreases with increasing SnCl4 concentration. The overall activation energy of the polymerization is lowered from 52 to 33 kJ · mol−1 by the presence of SnCl4, (0,342 mol · L−1). An NMR study revealed that 1 and SnCl4 form 1:1 and 2:1 complexes with a large stability constant in benzene. The propagating polymer radicals in the absence and presence of SnCl4 are ESR‐observable as a five‐line spectrum under the actual polymerization conditions. The complexed polymer radicals show further three‐line splitting due to two methylene hydrogens of the ethyl ester group. The polymer radical concentration increases with the SnCl4 concentration. The rate constant (kp) of propagation was determined using Rp and the polymer radical concentration. kp (6,3–2,9 L · mol−1 · s−1 at 50°C) decreases with increasing SnCl4 concentration. The presence of SnCl4 (0,342 mol · L−1) reduces the activation energy of propagation from 29 to 21 kJ · mol−1. The rate constant (kt) of termination was estimated from the decay curve of the polymer radicals, kt (3,1–1,1 · 105 L · mol−1 s−1) also decreases with the SnCl4 concentration. The activation energies of termination in the absence and presence of SnCl4 (0,342 mol · L−1) are 30 and 24 kJ · mol−1, respectively. Suppression of propagation and termination by SnCl4 seems to be explicable in terms of an entropy factor.
Quasi‐elastic light scattering by polystyrene‐poly(methyl methacrylate) diblock copolymer solutions in a non‐selective solvent in the vicinity of the overlap concentration
Authors: Haïda Houcine , Lingelser Jean‐Paul , Gallot Yves , Duval Michel 
Published: April 2003

AbstractThe dynamic properties of a styrene (S)‐methyl methacrylate (MMA) diblock copolymer in semidilute solutions of toluene have been investigated by quasi‐elastic light scattering. One relaxation mode has been found in the low‐concentration regime near the overlap concentration C*. This mode is identified as the cooperative mode which is observed in semidilute solutions of the equivalent polystyrene (PS) homopolymer. A second mode appears simultaneously at higher concentrations. This slower diffusive mode is ascribed to the diffusion of the center of mass of the clusters formed by the copolymer molecules. The fast structural mode which is predicted by the theory1–3 is not observed. It is suggested that this mode, which must have a small amplitude, is hidden by the other two relaxation modes.
The synthesis of siloxane‐based polymers containing photoactive cinnamate moieties
Authors: Barley Susan H. , Gilbert Andrew , Mitchell Geoffrey R. 
Published: April 2003

AbstractThree ways of synthesizing cinnamate‐based siloxane polymers suitable for photoisomerization purposes have been employed. The route involving direct hydrosilation of the photoactive unit and a non‐photoactive alkene with the homopolymer poly(methylsiloxane) has the severe disadvantages that the polymer is coloured, crosslinking during work‐up or storage commonly occurs and also some of the cinnamate CC double bonds are reduced during the hydrosilation. This loss of the chromophore can be decreased but not eliminated by its hydrosilation with the copolymer poly(dimethylsiloxane‐co‐methylsiloxane). All of the available SiH sites are now reacted with the cinnamate ester but a low concentration of active units on the polymer is still maintained. The most successful method of preventing loss of the chromophore is best achieved by functionalising the polymer via hydrosilation with allyl acetate, followed by hydrolysis of the acetate to the alcohol and finally esterification with the acid chloride of the chromophore. This procedure in contrast to the other methods, yields the photoactive polymer as an almost colourless, mobile liquid which is stable on storage and in which no reduction of the chromophore has occurred.
Polymer thin films and interfaces characterized with evanescent light
Authors: Knoll Wolfgang 
Published: April 2003

AbstractThis paper describes the use of evanescent light for the optical characterization of polymer thin films and interfaces. Firstly, a few basic concepts of evanescent wave phenomena, including total internal reflection, plasmon surface polaritons and guided optical modes, are reviewed. It is shown that the excitation of these waves allows for a sensitive determination of the optical architecture of the interface(s) involved. This “surface light” can then be used for the same broad range of optical techniques as it is known from experimental set‐ups designed for the investigation of various optical properties of polymer samples using plane electromagnetic waves, i.e. “normal” photons. This is demonstrated for diffraction experiments, microscopic investigations, inelastic scattering, e.g. Brillouin‐ or Raman‐spectroscopies, etc. The examples given include thin polymer films prepared by spin‐coating or by the Langmuir‐Blodgett‐Kuhn technique. It is shown that properties and processes at solid‐solution interfaces can be investigated equally well, and even surfaces of bulk samples can be characterized.
Copolymerization of ethylene with propene in the presence of Ti‐Mg catalysts of different compositions
Authors: Zakharov Vladimir A. , Yechevskaya Lyudmila G. , Bukatov Gennadii D. 
Published: April 2003

AbstractComonomer reactivity ratios (from kinetic and 13C NMR data), compositional homogeneity of ethylene‐propene copolymers, and molecular structure of individual fractions of the copolymers obtained with supported Ti‐Mg catalysts of different compositions were determined. The copolymerization reactivity of these systems was found to increase upon introduction of ethyl benzoate and dibutyl phthalate to the catalyst system. It was found that both lowly stereospecific and highly stereospecific catalysts have a broad distribution of active sites with respect to copolymerization reactivity. The composition of the catalysts (titanium content and stereoregulating additives) was shown to influence the reactivity ratios of the comonomers and the microstructure of the copolymers.
Untersuchungen zur Thiol/En‐Polymerisation: elektronenspinresonanzspektroskopischer Nachweis spontaner Radikalbildung
Authors: Sensfuß Steffi , Friedrich Manfred , Klemm Elisabeth 
Published: April 2003

AbstractBy means of ESR (electron spin resonance) spectroscopic investigations it is shown, that in dithiol/diene‐mixtures, in the absence of daylight and oxygen, radicals are formed spontaneously. Using the spin trapping technique and nitrosodurene (ND) as the trapping agent the existence of sulfur and carbon radicals could be proved unambiguously. Oxygen has no significant influence on the reaction. Spin trapping experiments have shown, that the aliphatic dithiols investigated do not form any traceable quantity of RS. and .OOH radicals in the presence of air. Radicals are detected only after addition of an ene‐compound.
On the determination of double‐bond contents of linear and crosslinked liquid‐crystalline polyesters including the corresponding monomers by differential pulse polarography
Authors: Peter Karin , Peter Ralf , Rätzsch Manfred 
Published: April 2003

AbstractUnsaturated liquid‐crystalline polymers are synthesized with the aim to fix the liquid‐crystalline state which causes the favourable polymer properties by means of subsequent crosslinking. The elucidation of the influence of crosslinking on the liquid‐crystalline properties of such polyesters is possible using the determination of the double‐bond content in the polymer. Because the CC bonds of fumaric acid units are determined analytically by electrochemical reduction, a polarographic determination of the double‐bond content appears to be a favourable method. The treatment of the polymeric material and the choice of a solvent system which is suitable both in respect to electroanalytical use and sufficient solvent power are of first importance.
Microspheres prepared from temperature‐sensitive graft polymers
Authors: Kitano Hiromi , Yan Changhong , Nakamura Katsunori 
Published: April 2003

AbstractPolyallylamine‐graft‐poly(N‐isopropylacrylamide) was prepared by coupling polyallylamine with poly(N‐isopropylacrylamide) (the latter with an end‐standing carboxyl group). The graft polymer obtained showed a temperature‐responsive phase transition under alkaline conditions, whereas the starting poly(N‐isopropylacrylamide) with end‐standing carboxyl group showed temperature‐sensitivity under acidic conditions. With an increase in the degree of grafting the temperature‐sensitivity of the polymer under weakly alkaline conditions increases. Microspheres were prepared by cross‐linking the graft polymers with glutaraldehyde in water‐in‐oil emulsion. Trypsin immobilized to the microspheres showed temperature‐responsiveness in its catalytic activity. The graft polymer can be used as a component of temperature‐sensitive devices in various forms.
Acrylamide‐co‐methacrylamide copolymers carrying peptide side chains: application to asymmetric catalysis
Authors: Boulahia Jalel , Carrière François , Sekiguchi Hikaru 
Published: April 2003

AbstractThe stereoselective epoxidation of chalcone, catalyzed by poly(L‐alanine) (PLA)‐grafted N‐benzylacrylamide‐co‐N‐aminopropyl methacrylamide copolymers, was carried out in the ternary system water/CCl4/polymer catalyst. The resulting oxirane was obtained with about 60% yield with an enantiomeric excess (e. e.) of 80%. A good catalytic efficiency was observed even under conditions of high dilution. When the same catalyst was used a third time, an important racemization of supported PLA gave a strong decrease of yield and e. e. values of the resulting epoxide. Better results with a lower benzylacrylamide moiety content in the copolymer backbone might be due to a higher density of PLA chains.
Telechelic polystyrene α,ω‐macrozwitterions, 1. Synthesis and characterization
Authors: Antonietti Markus , Heyne Joachim , Sillescu Hans , Lindner Peter 
Published: April 2003

AbstractTelechelic α,ω‐macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small‐angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by their scattering behaviour. Above a critical concentration being in the range of 0,05 g/cm3, an infinite aggregate is formed. Zwitterions in N,N‐dimethylformamide behave differently: due to the attenuation of dipolar forces, no clusters are formed. In this case, the behaviour in dilute solution can be described by the formation of polymeric rings consisting of one polymer molecule, only.