bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(propylene sulfoxide) — a first approach to a dipolar aprotic, water‐soluble and reactive polymer
Authors: Orgeret‐Ravanat Catherine , Galin Jean‐Claude
Published: April 2003

The oxidation of atactic poly(2‐methylthiirane) (PPS, M̄w ≈ 1 – 2 · 105) to its corresponding sulfoxide (PPSO) is studied under a variety of experimental conditions: m‐chloroperbenzoic acid in homogeneous chloroform solution ( − 7°C) and hydrogen peroxide or bromine in an interfacial chloroform‐water system (20°C) lead to selective and quantitative oxidation under stoichiometric conditions with simultaneous chain degradation (M̄w (PPSO) ≈ 0,5 – 3 · 104). The high density of sulfoxide functions affords to the PPSO chain a number of specific properties such as: (a) solubility in dipolar protic (CH3OH, CHCHl3 …) and aprotic (DMF, DMSO) solvents, the polymer coils being, however, strongly associated in aqueous solution, (b) strong polarity of the bulk polymer, as shown by an “apparent local dipole moment” of about 4,1 D, (c) poor thermal stability, degradation starting at about 130°C under nitrogen, with a weight loss of 50% at 160°C (apparent activation energy Ea = 100 kJ · mol−1).
Polymères porteurs de dérivés du glycérol, 9 Modification de polyacides par des esters d'époxy‐2,3 propyle
Authors: Brosse Jean‐Claude , Razermera Faly , Soutif Jean‐Claude
Published: April 2003

Previously synthesized 2,3‐epoxypropyl esters were used to modify polymethacrylic and alginic acids. This way of synthesis led to polymers whose structure can be compared to that of polymers obtained from the reaction of acids with polymers bearing the same type of oxirane rings, the active molecule being linked to the polymer backbone through a glycerol spacer. As for the preceding studies, the reaction was investigated from a chemical and kinetical point of view with epoxypropyl esters of acetic acid and 1‐(4‐chlorobenzoyl)‐5‐methoxy‐2‐methyl‐3‐indolacetic acid (indomethacin).
Thermodynamics and high‐pressure viscosity of dilute solutions of poly(decyl methacrylate) and how the free volume influences them
Authors: Schott Nicole , Will Bernhard , Wolf B. A.
Published: April 2003

Light scattering and viscometric measurements were performed for the system isooctane/poly(decyl methacrylate) of weight‐average molecular weight M̄w = 250 000 within the concentration regime of pair interaction between the macromolecules in the temperature range from 25°C to 100°C. In case of the intrinsic viscosities [η], the pressure was varied up to 3500 bar. Under isobaric conditions, the osmotic second virial coefficients A2, the z‐average radii of gyration rz and [η] pass through a maximum, the Huggins coefficient kH through a minimum, with variation of temperature. These extrema indicate a change in the heat of dilution from endothermal at low, to exothermal at high temperature T. The calculation of the temperature dependence of the intrinsic viscosity [η] (T) for isochoric conditions does not yield a maximum, provided the pressure at the lowest temperature is chosen close to atmospheric pressure; it can, therefore, be concluded that the change in the sign of the enthalpy is in this case only due to the free volume of the system which increases markedly with increasing T. For pressures larger than ≈700 bar, maxima are always observed, no matter whether the temperature is changed isobarically or isochorically. All parameters under investigation are closely interdependent: A one‐to‐one correspondence exists between [η] and A2 at 1 bar, and kH and [η] interrelate linearly for constant T.
An investigation of the self‐aggregation process of syndiotactic poly(methyl methacrylate) in solution by using infrared spectra
Authors: Dybal Jiří , Spěváček Jiří
Published: April 2003

The time dependence of self‐aggregation of syndiotactic (s) poly(methyl methacrylate) (PMMA) in dilute toluene or CCl4 solutions was investigated using infrared (IR) spectra measurements. The IR spectra were also recorded in s‐PMMA solutions where no self‐aggregation takes place (benzene, acetonitrile). It was found that the helix conformation with a large number of units per turn (near‐tt) in aggregated s‐PMMA is formed in parallel with intermolecular interactions of ester groups of s‐sequences. The connection between the fraction of s‐sequences in the helix conformation determined for unaggregated s‐PMMA in various solvents using IR spectra and the ability of s‐PMMA to form self‐aggregates (double helix) in a certain solvent is discussed. Intersegmental contacts which occur in s‐PMMA in CCl4, i.e. in a thermodynamically poor solvent, lead to a decrease in the equilibrium aggregated fraction, to the slowing‐down of the aggregation process and to the decomposition of the majority of aggregated structures during evaporation of the solvent; their effect is similar to that of chemical crosslinking.
Molecular mobility in polystyrene‐poly(methyl vinyl ether) blends as studied by fluorescence polarization
Authors: Halary Jean‐Louis , Larbi Fadhel Ben Cheikh , Oudin Pascal , Monnerie Lucien
Published: April 2003

Molecular motions in different blends of polystyrene with poly(methyl vinyl ether) were investigated by fluorescence polarization measurements on small amounts of dimethylanthracene‐labeled polystyrene chains added to the system. The temperature dependence of the mobility parameter of the label was studied within the DSC glass transition and phase coexistence temperature range. Experimental data fit an expression of the WLF type, in which C1 and C2 values are roughly independent of blend composition and differ to a small extent from the ‘universal’ coefficients. Moreover, mobility determinations suggest the existence of composition micro‐heterogeneities in the blends below their phase coexistence temperature Tc when subjected to long annealing around Tc – 25°C or above.
Structural studies on 1,4‐cis‐poly(2‐methyl‐1,3‐pentadiene) synthesized with Nd catalysts
Authors: Cabassi Franco , Porzio William , Ricci Giovanni , Brückner Sergio , Meille Stefano V. , Porri Lido
Published: April 2003

(E)‐2‐Methyl‐1,3‐pentadiene was polymerized with the AlEt2Cl‐Nd(OCOC7H15)3‐Al(iBu)3 system to a polymer consisting of 98–99% 1,4‐cis‐structure. The crude polymer was fractionated by successive extractions with boiling diethyl ether, heptane and toluene. Examination of the soluble fractions and of the residue to toluene extraction by NMR, X‐ray and DSC techniques indicated that the crude polymer consists of macromolecules differing in stereoregularity. Evidence is reported that the crystalline residue after the toluene extraction has a 1,4‐cis‐isotactic structure. The existence of two different crystalline phases is shown and the respective cell parameters have been determined. α‐Phase: a = 10,74, b = 13,04, c = 7,87 Å (−120°C), space group Pbca, Z = 8, Dc = 1,00 g · cm−3. β‐phase: a = 9,30, b = 7,73, c = 7,90 Å (25°C), space group P212121Z = 4, Dc = 0,96 g · cm−3.
The structure of one crystalline form of isotactic 1,4‐cis‐poly(2‐methyl‐1,3‐pentadiene). An application of the rietveld method
Authors: Brückner Sergio , Meille Stefano V. , Porzio William , Ricci Giovanni
Published: April 2003

Crystalline polymers of (E)‐2‐methyl‐1,3‐pentadiene, consisting almost exclusively of 1,4‐cis units, obtained with the ternarycatalytic system AlEt2Cl‐Nd(OCOC7H15)3‐Al(iBu)3, exhibit two different crystalline forms. In this study, we determine the crystal structure of the form showing the highest melting point (175°C) through X‐ray diffraction data from stretched and unstretched samples. Diffraction data from an unstretched (powder) sample were used to carry out a refinement procedure based on the Rietveld method. The space group is orthorhombic Pbca, the cell constants are a = 10,74, b = 13,04, c = 7,87 Å, and the polymer is isotactic.
Nematic‐nematic immiscibility and induced smectic a phases in mixtures with liquid‐crystalline side‐chain polymers
Authors: Achard Marie‐France , Sigaud Gilles , Keller Patrick , Hardouin Francis
Published: April 2003

Two non‐ideal kinds of behaviour for solutions of liquid‐crystalline side‐chain polymer (LC polymer) solutes in nematic solvents of low molecular weight (LMW) are investigated, viz. immiscibility and induced smectic A phases. The former property already observed in the nematic state of some polysiloxanes is extended to polymethacrylates (or polyacrylates) leading to the conclusion that immiscibility is strongly influenced by the chemical structure of the whole macromolecule. The latter property responds in the same way as the former to molecular modifications, suggesting that they can be connected somehow.
Formation and structural characteristics of loosely crosslinked styrene‐divinylbenzene networks
Authors: Okay Oǧuz
Published: April 2003

The free‐radical copolymerization of styrene with small quantities of a commercial DVB (conc.: 0,35 to 0,53 mol‐% DVB) was carried out at 70°C in bulk or in concentrated toluene solution. The extent of the crosslinking reactions beyond the gel point and the structural characteristics of the resulting networks were examined using equilibrium swelling in toluene and gel fraction measurements. The copolymerization reactions yield loosely crosslinked networks together with varying amounts of soluble polymer. The experimental results concerning the formation of the networks and their properties can be explained using the kinetic mechanism of the copolymerization reaction and neglecting cyclization. At a low degree of initial dilution, two opposing effects of the diluent, namely dilution and plasticizing effects, were found to determine the properties of the networks. Calculations using the theory of rubber elasticity indicate that considerable amounts of free chain ends are present in the networks. The crosslinking efficiency was found to decrease, but the size of the primary chains and that of the network chains increase with increasing degree of initial dilution.
Effect of flexible spacers in liquid crystalline copolyesters containing a non‐linear biphenol moiety
Authors: Zhang Weisheng , Jin Jung‐Il , Lenz Robert W.
Published: April 2003

A series of copolyesters 2 containing both linear mesogenic and non‐linear non‐mesogenic aromatic ester units was prepared and characterized for the ability of the latter to either modify or destabilize the liquid‐crystalline (LC) properties of the former. The mesogenic units were formed from the reaction of 1,4‐phenylene diacetate (3) with 4,4′‐decamethylenedioxydibenzoic acid (5), whereas the non‐mesogenic units were formed from reaction of the latter monomer with the diacetate of the non‐linear biphenol, sulfonylbis(1,4′‐phenylene) diacetate (4). The presence of the flexible spacer in each unit allows the copolyesters to form a nematic phase even at a content of non‐mesogenic units as high as approximately 80 mole‐%. Copolyester compositions with mesogenic unit contents approaching this limit for LC behavior appear to form melts which contain both nematic and isotropic phases below the isotropization transitions.
Oxidation of poly(2,2‐dimethyltrimethylene sulfide) in solution
Authors: Lazcano Silvia , Marco Carlos , Fatou José G. , Bello Antonio
Published: April 2003

Oxidation of poly(2,2‐dimethyltrimethylene sulfide) was carried out in chloroform solution at 25°C using trifluoroacetic acid and hydrogen peroxide. Six samples were obtained with weight fractions of sulfoxide comonomer ranging between 0,11 and 0,58, without any content of sulfone groups. When it is attempted to obtain samples with more than 60% of sulfoxide units, sulfone groups are formed. 1H NMR data show the reaction to take place in a random way. Copolymers exhibit only one glass transition temperature which increases with the number of sulfoxide units, The extrapolated glass transition temperature for the theoretical polysulfoxide corresponds to a value in the range of 261 to 264 K.
Studies on the adsorption of anionic dyes on chitosan
Authors: Maghami Ghobad G. , Roberts George A. F.
Published: April 2003

Equilibrium adsorption measurements of three anionic dyes on chitosan, under acid conditions, show that there is a 1 : 1 stoichiometry for the interaction of sulfonic acid groups on the dyes with protonated amine groups of the chitosan for mono‐, di‐ and trisulfonated dyes. Comparison of the extents of N‐acetylation calculated from equilibrium dye adsorption values with those determined by IR spectroscopy, for a series of chitosan samples covering a wide range of N‐acetylation values, demonstrates that equilibrium adsorption measurements may be used for the analysis of chitin and chitosan.
Polymerization by [3 + 2]‐cycloaddition
Authors: Nuyken Oskar , Maier Gerhard , Burger Klaus
Published: April 2003

The reaction of hexafluoroacetone azine (1) with dienes 13a–d was used to synthesize polymers 14a–d of a new type with diazabicylooctanediyl units in the main chain. The influence of the structure of the diolefins on the solubility of these polymers was investigated. The soluble oligomers were characterized thoroughly by 1H NMR, 13C NMR, 19F NMR, IR and MS.
Synthesis and hydrolysis of esters from amylose and nicotinoyl chloride
Authors: Sánchez‐Chaves M. , Arranz F.
Published: April 2003

The modification reaction of amylose with nicotinoyl chloride using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on polymer, nicotinoyl chloride and pyridine was found. The activation energy was found to be 32,2 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound is dependent upon the hydrophilic character of the modified amylose polymers, the temperature as well as the pH value of the medium.
Influence of the chemical constitution of the polymer backbone on the phase behaviour of liquid‐crystalline side‐chain polymers with side‐on fixed mesogenic groups
Authors: Hessel Friedrich , Finkelmann Heino
Published: April 2003

The synthesis and phase behaviour of liquid‐crystalline acrylates and chloroacrylates with side‐on fixed mesogenic groups are described. Polymers which have similar mesogenic groups but whose polymer backbones differ in chemical constitution exhibit identical liquid‐crystalline to isotropic phase transformation temperatures (Tc). The glass transition temperature (Tg) decreases with increasing flexibility of the main chain and with increasing length of the terminal groups of the mesogenic side groups. All polymers with side‐on fixed mesogenic groups exhibit a nematic phase. The domain texture indicates biaxial nematic phase behaviour. In copolymers consisting of mesogenic and non‐mesogenic monomers, nematic phase behaviour is still observed, Tc is strongly depressed, and Tg is similar to that of the non‐mesogenic homopolymer.
Copolymers obtained by means of anionic ring‐opening polymerization. Poly(2,2‐dimethyltrimethylene carbonate‐tapered‐ϵ‐caprolactone)
Authors: Keul Helmut , Höcker Hartwig , Leitz Edgar , Ott Karl‐Heinz , Morbitzer Leo
Published: April 2003

The anionic ring‐opening polymerization of mixtures of 2,2‐dimethyltrimethylene carbonate and ϵ‐caprolactone in toluene as solvent, with sec‐butyllithium or potassium dihydronaphthylide as initiator, results in the formation of polymers of the (A‐X‐B)n type, where A represents a poly(2,2‐dimethyltrimethylene carbonate) block, B represents a poly(ϵ‐caprolactone) block and X stands for a block of the two monomers with a composition gradient; n represents the number of portions by which the monomer mixture is added to the initiator or the living system. From the time‐conversion curves it follows that the reactivity of the carbonate monomer is higher than that of the lactone. This difference in reactivity of the monomers is the reason for the special polymer architecture represented by (A‐X‐B)n. The properties of these polymers depend upon the ratio of the monomers and the number n of additions. The polymers are characterized by spectroscopic, thermoanalytical, and thermomechanical measurements.
A new method for monitoring ultra‐fast photopolymerizations by real‐time infra‐red (RTIR) spectroscopy
Authors: Decker Christian , Moussa Khalil
Published: April 2003

An original method based on IR spectroscopy has been developed in order to follow real‐time photopolymerizations that take place in less than one second. Conversion versus time curves were directly recorded for various multiacrylic monomers irradiated in condensed phase, thus allowing an immediate evaluation of both the rate of polymerization and the amount of residual unsaturation in the UV‐cured polymer. This method proved well suited to study the effect on the polymerization rate of the photoinitiator efficiency, the monomer reactivity, the light intensity, the film thickness, and the O2 inhibition. The dark polymerization that develops just after the UV exposure was investigated as a function of the degree of conversion and was shown to represent up to 60% of the total process. A comparison with other methods of kinetic analysis shows the unique advantages of real‐time infra‐red (RTIR) spectroscopy which permits to follow quantitatively and in situ ultra‐fast polymerizations.
Amphiphilic properties of synthetic glycolipids based on amide linkages, 3. Temperature and concentration dependence of the reduced viscosity of gel‐forming alkyl gluconamides
Authors: Pfannemüller Beate , Kühn Ilse
Published: April 2003

In order to follow the process of aggregation, viscosity measurements in dilute aqueous solution were performed with two carbohydrate amphiphiles: (i) N‐octylgluconamide (C8‐GA) and (ii) N‐decanoyl‐N‐methylglucamide (C10‐MGA). Both compounds ten to form a gel on cooling, the former at 65°C, the latter at 10°C. Electron micrographs have shown that the gels are composed of a loose network of thin, regularly twisted helical ropes. By viscosity measurements over a wide range of temperatures and concentrations, typical changes of the reduced viscosity were observed. Results are discussed with respect to the critical micelle concentration (CMC), the Krafft point, i. e. the critical temperature of crystallization (Tc), and the cloud point (Tcp). It is concluded that micellar aggregation to rod‐shaped particles, quasi‐crystalline aggregation to highly hydrated gels, and crystallization of monomers, the latter mediated by hydrogen bonding, are involved and compete with each other.
13C NMR study of the microstructure of poly(styrene oxide)s prepared with anionic initiators
Authors: Sepulchre Maurice , Kassamaly Asmina , Moreau Michel , Spassky Nicolas
Published: April 2003

The tacticity and the nature of irregularities and end‐groups in poly(styrene oxide) samples prepared using potassium alcoholates and anionic coordinated systems as initiators were studied by 13C NMR at 62,89 MHz. It was found that the polymerization initiated with potassium alcoholates fits a first‐order Markov propagation model. Head‐to‐head (HH) and tail‐to‐tail (T‐T) irregularities are detected in all the samples studied, but more than 95% of the opening of the oxirane ring occurs in the β‐position with potassium alcoholates as initiators while about 10% of α‐scission may be observed with coordinated systems. Secondary hydroxyl terminal groups and initiator moieties are identified in polymers prepared with potassium alcoholates. Poly(styrene oxide) was found to undergo chain‐scission by aging at 25°C. Among the various structures produced by the oxidative degradation process, benzoate and secondary hydroxyl groups are identified.
Direct method of synthesis of polyureas by N‐acylphosphoramidites
Authors: Rokicki Gabriel
Published: April 2003

Polyureas and polythioureas were prepared under mild conditions by direct polycondensation of carbon dioxide and carbon disulfide, respectively, with diamines in the presence of diethyl N‐acetyl‐N‐methylphosphoramidite or its analogs containing an active PN bond. The influence of the substituents in the phosphoramidite, of the CO2 pressure, solvent, organic base and diamine structure on the yield and inherent viscosity of the polymer was investigated. A reaction mechanism involving the intermediate formation of a mixed anhydride of dialkylphosphorous and alkyl(aryl)carbamic acid is discussed.
Etude de la diaddition de l'acétate d'allyle sur les télogènes chlorofluorés possédant deux groupements CCl3 en extrémité de chaîne
Authors: Améduri Bruno , Boutevin Bernard , Lecrom Christophe , Pietrasanta Yves , Parsy Roland
Published: April 2003

The redox catalyzed addition of compounds such as Cl3CCF2CCl3 and Cl3CCF2CCl2CH2CHClCH2OCOCH3 to allyl acetate was studied with the purpose of obtaining telechelic products. RuCl2[P(C6H5)3]3 was used as catalyst, and its action was compared to that of cooper‐ or iron‐based catalysts. The products were isolated and their structures studied by means of 13C, 19F and 1H NMR spectroscopy. The reaction mechanism was studied to improve the yield of the diaddition product for its utilisation as monomer in polycondensation reactions. It was found that the low reactivity for a second addition is not due to the presence of a chlorine atom in β‐position of the acetate function. When allyl acetate was replaced by allyl bromide or chloride in the first addition, the second addition to allyl acetate occurred normally.
A λ5‐cylotriphosphazene with nitroxyl groups as model for a paramagnetic poly(organo‐λ5‐phosphazene)
Authors: Dulog Lothar , Möhler Hans
Published: April 2003

Reaction of hexachlorocyclotriphosphazene (syst. name: 2,2,4,4,6,6‐hexachloro‐1,3,5,2λ5,4λ5,6λ5‐triazatriphosphorine) (1) with 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (2a) gave the hexa‐substituted λ5‐cyclotriphosphazene 3a. Electron paramagnetic resonance spectra at low concentrations (10−5 mol/L) showed a singlet only (no triplet) due to spin‐spin exchange in the molecule. The paramagnetic molar susceptibility amounts to 7229 · 10−6 cm3/mol at 300 K and does not depend on the magnetic field strength. 3a obeyed the Curie‐Weiss law between 36 and 296 K demonstrating that there is no antiferromagnetic spin exchange.
X‐ray diffraction study on the phase behaviour of a liquid‐crystalline side‐group polymethacrylate with biphenylyl mesogen moieties
Authors: Zugenmaier Peter , Menzel Henning
Published: April 2003

X‐ray investigations at different temperatures of a polymethacrylate 1 with biphenylyl moieties as side‐group mesogens reveal structural changes at 100°C for a quenched sample of the polymer which cannot be detected by differential scanning calorimetry (DSC). A low‐order smectic phase exists between 136 and 157°C, and an isotropic phase above 157°C. The side groups are much shorter than the observed thickness of the smectic layers. Models are discussed which can account for these spacings. The phase sequence for normally cooled and at 120°C annealed samples is represented by crystalline or higher‐order smectic, low‐order smectic, isotropic. Different structures in the solid state are detected for the two differently prepared samples.
Interfacial synthesis of group IVB metalorganic polymers
Authors: Shen Hongkang , Wei Rongbao , Liang Ya , Lin Lin , Liu Meizhu , Xue Qifeng
Published: April 2003

Alkyl, alkenyl, and alkoxy substituted dicyclopentadienyltitanium (or zirconium) dichlorides were condensed with diacids, hydroxyacids or diphenols to give metal containing polyesters, poly(ether‐ester)s, and polyethers, most of them being new. Experimental parameters were investigated, including stirring rate, reaction time, reaction temperature, steric hindrance, ratio of reactants, and reactivity of the reactants. Determinations of color‐change temperatures, solubilities and molecular weights were carried out as well as TG, DTG and IR spectroscopy of the resulting polymers.
Photoinitiators and photoinitiation, 9 Photoinitiators for radical polymerization which counter oxygen‐inhibition
Authors: Hageman Hendrik J. , Jansen Leonardus G. J.
Published: April 2003

1‐Alkanesulfonic and 4‐alkylbenzenesulfonic esters of α‐hydroxymethylbenzoin were shown to photoinitiate the polymerization and crosslinking of acrylates. The overall rate of polymerization in bulk and of crosslinking in solution, respectively, proved to be constant within each series of homologues. However, in thin films in an air atmosphere, the overall rate of crosslinking (curing rate) proved to increase with increasing alkyl chain‐length within each series of homologues. Moreover, the curing rate obtained with the 1‐hexanesulfonic ester and its higher homologues substantially surpassed the curing rates obtained with a number of established photoinitiators, provided a small amount of an alkali metal salt (preferably a lithium salt) is present. The curing mechanism of the sulfonic esters of α‐hydroxymethylbenzoin and the role of the alkali metal salt are explained.
Extremely highly isospecific polymerization of olefins using solvay‐type TiCl3 and Cp2TiMe2 as catalyst
Authors: Soga Kazuo , Yanagihara Hisayoshi
Published: April 2003

Polymerizations of various olefins (ethylene, propene, 1‐butene, 4‐methyl‐1‐pentene,1‐hexene, and 1‐octene) were carried out using the Solvay‐type TiCl3 catalyst combined with Cp2TiMe2. The polymers produced were characterized by DSC, solvent fractionation, GPC, and 13C NMR. It was found that the present catalyst gives linear polyethylene without ethyl branches and extremely highly isotactic poly(α‐olefins) containing very few steric defects. The catalyst seems to be most isospecific among the Ziegler‐Natta catalysts reported so far.
Microdomain control in graft copolymer and polymer blends by means of epitaxial growth
Authors: Ishizu Koji , Mitsutani Kenji
Published: April 2003

Poly(vinyl acetate) (PVAc) and poly(tert‐butyl methacrylate) (PBMA) macromonomers with vinyl end‐groups were synthesized by radical or anionic polymerizations. 4‐Vinylpyridine (4VP)/vinyl acetate (VAc) and 4VP/tert‐butyl methacrylate (BMA) graft copolymers were prepared by radical copolymerization of these macromonomers with 4VP as a comonomer. The 4VP/vinyl alcohol (VA) graft copolymer was derived from alkaline hydrolysis of 4VP/VAc graft copolymer. After having fixed the microdomains of 4VP/VA graft copolymer film, the solution of graft copolymer (or polymer blends) was cast on a support film of 4VP/VA graft copolymer. It was shown that the domain structure of the upper layer is governed by epitaxial growth of the microdomain pattern of the support film surface.
Synthesis of star‐shaped poly(ethylene oxide)
Authors: Gnanou Yves , Lutz Pierre , Rempp Paul
Published: April 2003

Three different methods to synthesize star‐shaped poly(ethylene oxide) are discussed in the present article. In all three cases, the branches are grown from a plurifunctional initiator. It is established that even though the early stages of the polymerization occur in heterogeneous phase, the consequences on the polymers formed are of minor importance. The most significant method is a core‐first process, involving multifunctional poly‐DVB cores as the initiating species, made anionically in dilute solution. Although strong association phenomena are occurring during the growth of the branches, star‐shaped poly(ethylene oxide)s with a high number of functionalized branches are obtained. The polymers arising from all three methods were characterized accurately.
Heterogene polymeranaloge Reaktionen zwischen Polybutadienepoxiden und anorganischen Feststoffoberflächen
Authors: Heublein Günther , Heublein Brigitte , Hortschansky Peter , Schütz Heidrun , Flammersheim Hans‐Jürgen
Published: April 2003

Heterogeneous, polymeranalogous reactions between polybutadieneepoxides (PBDE) and inorganic surfaces (SiO2, Al2O3, hydroxyapatite) were investigated. The composition of the resulting composites was determined by gravimetric methods and expressed as “degree of reaction” (RG). Interface reactions could be followed by spectroscopic methods and by differential scanning calorimetry. The results of the reaction mechanisms are discussed. Infrared and 13C solid state NMR studies suggest that the PBDE macromolecules are linked by bonds to the SiO2 surface and by and bonds to the Al2O3 surface.
In situ photopolymerization of an oriented liquid‐crystalline acrylate, 2
Authors: Broer Dirk J. , Mol Grietje N. , Challa Ger
Published: April 2003

During the photo‐initiated free‐radical bulk polymerization of 4‐biphenylyl 4‐(6‐acryloyloxy‐hexyloxy)benzoate (1) in the liquid‐crystalline state, the ordering is maintained, leading to an oriented liquid‐crystalline side‐chain polymer. The course of the photopolymerization depends on the phase of monomer1. In the monotropic smetic‐A and in the monotropic nematic phase the polymerization rate and conversion are affected by crystallization during polymerization. In the stable nematic phase the bulk polymerization is fast and complete. In this temperature region the transition from nematic1to smectic poly(1) is passed during which temporary segregation may occur, affecting the molecular ordering. Starting with isotropic1, the polymerization proceeds considerably more slowly.
Propene polymerization with MgCl2‐supported transition metal catalysts activated by Cp2MtMe2(Mt = Ti, V, Zr, Hf)
Authors: Soga Kazuo , Uozumi Toshiya , Yanagihara Hisayoshi
Published: April 2003

Several kinds of MgCl2‐supported catalysts were prepared by grinding the mixtures of MgCl2 and MtCln(MtCln = TiCl4, ZrCl4, HfCl4, VCl3). Polymerization of propene was conducted at 40°C and 1 atm with these solid catalysts by using Cp2MtMe2 (Mt = Ti, Zr, Hf, V) as cocatalyst. Polymerization took place only with the use of the TiCl4/MgCl2 catalyst. Both the activity and isospecificity were found to strongly depend upon the cocatalyst used. The polymers produced were fractionated with boiling heptane and analyzed by means of 13C NMR, the results of which suggested the existence of two types of catalytic centers, isospecific and aspecific. Plausible models of these catalytic centers are proposed.
Evaluation of olefin reactivity ratios over highly isospecific Ziegler‐Natta catalyst
Authors: Soga Kazuo , Yanagihara Hisayoshi , Lee Dong‐ho
Published: April 2003

The recently found catalyst system, composed of Solvay‐type TiCl3 and (RCp)2TiMe2, producing extremely high isospecific polyolefins, was used for copolymerizations of ethylene with various α‐olefins (propene, 1‐butene,1‐hexene and 4‐methyl‐1‐pentene) to obtain monomer reactivity ratios for isospecific centers. It was found that no homopolymer was formed actually. Using the copolymer composition obtained by 13C NMR, the monomer reactivity ratios were calculated according to the Fineman‐Ross and Kelen‐Tüdős method. For the ethylene/propene pair the same values of reactivity ratio were also obtained from the diad distribution of comonomers. The relative reactivity of these olefins was found to decrease in the following order; ethylene > propene > 1‐butene > 1‐hexene > 4‐methyl‐1‐pentene.
Anionic block polymerization initiated by potassium solutions, 2. Synthesis of poly(2‐oxetanone)‐block‐polystyrene‐block‐poly(2‐oxetanone)
Authors: Jedliński Zbigniew , Kurcok Piotr , Adamus Grazyna
Published: April 2003

The block polymerization of styrene with 2‐oxetanone (β‐propiolactone) proceeds fast with a yield of more than 90%, in the presence of potassium solutions in THF containing 18‐crown‐6. Poly(2‐oxetanone)‐block‐polystyrene‐block‐poly(2‐oxetanone) ABA triblock polymers having the expected molecular mass and composition are formed. Their glass transition and melting temperatures as well as their melting enthalpies determined by DSC show a strict correlation with block polymer composition. The mechanism of this block polymerization involving acyloxygen and alkyl‐oxygen bond scission in 2‐oxetanone is in good agreement with previous results of the homopolymerization of β‐lactones by alkali metal solutions abounding in potassium anions.
Controllable specific interaction and miscibility in polymer blends, 1. Hydrogen bonding and morphology
Authors: Cao Xianyi , Jiang Ming , Yu Tongyin
Published: April 2003

This paper concentrates on the effect of introducing hydrogen bonding into otherwise immiscible blends on their miscibility and morphology. 1,1,1,3,3,3‐Hexafluoro‐2‐hydroxypropyl‐containing units are incorporated in polystyrene which is then mixed with carbonyl‐containing polymers such as poly(methyl methacrylate) and poly(butyl acrylate). The infrared study confirms the formation of hydrogen bonding and shows that the frequency shifts of hydroxyl stretching caused by the H‐bonds are independent on whether the hydroxyl‐containing units are in the monomer or connected to polystyrene or polyisoprene chains and whether they are randomly distributed along the chains or only located at the ends of the polymers. Hydrogen bonding in the blends dramatically enhances miscibility judged by differential scanning calorimetry and transmission electron miscroscopy (TEM). TEM observations reveal apparent and regular variations of the morphology in the blends with the content of the hydroxyl‐containing groups, which implies that the morphological features of the blends, such as size of the dispersed phase, or extent of interpenetrating between the components are controllable simply by changing the structure and/or amount of the introduced groups forming the specific interaction in the blends.
Compatibility of poly(ethylene oxide) and poly(methyl methacrylate) chains in solutions of their blends, diblock and triblock copolymers
Authors: Wohlfarth Christian , Regener Erhard , Rätzsch Margit T.
Published: April 2003

Solvent activity data were obtained from vapour pressure measurements at 50°C, 70°C, 100°C and reduced to χ‐functions in systems consisting of benzene or toluene on the one hand and blends or block copolymers of poly(ethylene oxide) and poly(methyl methacrylate) on the other. The χBC‐values are negative for all polymer subsystems, but miscibility on a segmental scale is somewhat different for block copolymers and blends. χBC depends on the concentration of solvent and is mainly influenced by the Δχ‐effect in solution and correlated with the syndiotacticity of the PMMA chains. There is only a small influence of temperature and blend composition or block ratio.
Effect of the degree of saponification on the rheological and thermal properties of poly(vinyl alcohol) gels
Authors: Watase Mineo , Nishinari Katsuyoshi
Published: April 2003

The rheological and thermal properties of poly(vinyl alcohol) (PVA) gels prepared through freezing‐thawing cycles were studied, in order to clarify the relation between structure and functional properties. The breaking strength of PVA gels increases with increasing the degree of saponification (DS), i.e. the degree of deacetylation, while the breaking deformation decreases. The endothermic differential scanning calorimetry (DSC) peak accompanying the transition from gel to sol shifts to higher temperatures with increasing concentration and DS. The endothermic enthalpy as a function of concentration increases gradually up to 25 wt.‐%, then it increases rapidly for PVA with DS = 96,0,97,5 and 98,5 mol‐%. A sharp diffraction peak is observed in the X‐ray pattern for PVA gels with DS = 99,9 mol‐% but not for PVA gels with DS = 96,0 mol‐%. All results from rheology, DSC and X‐ray analysis show that only a slight increase in DS from 96,0 mol‐% to 97,5 mol‐% promotes the formation of ordered regions in PVA remarkably.
Determination of the reinitiation constants and other kinetic parameters of free‐radical polymerization by gas‐chromatography/mass spectrometry
Authors: Farina Mario , Silvestro Giuseppe Di , Sozzani Piero
Published: April 2003

GC‐MS analysis of oligomers obtained by using a high concentration of chain transfer agents permits the identification and determination of the concentrations of all the compounds formed in the early propagation steps. From these data the exact structure of the starting chain end and the evaluation of a series of kinetic and probabilistic parameters can be obtained, thus allowing a more detailed description of the polymerization mechanism. Applying this method to the copolymerization of styrene (1) and methyl methacrylate (2), a value of 6 was obtained for the ratio of the reinitiation rate constants kr1/kr2 in the presence of 1‐butanethiol at 60°C.
Synthèse de polysiloxanes téléchéliques, 1. Synthèse de diols et diépoxydes
Authors: Boutevin Bernard , Youssef Boulos
Published: April 2003

Telechelic poly(dimethylsiloxane)s (4, 5, 6) with acetoxy, hydroxyl or 2,3‐epoxypropoxy functions as end groups were synthesized. As starting materials chloro‐3‐acetoxy‐[or 3‐(2,3)‐epoxypropoxy]‐propyldimethylsilanes (2 and 3) were prepared by hydrosilylation of the corresponding allylic derivatives with chlorodimethylsilane, and subsequently condensed with α‐hydro‐ω‐hydroxyoligo‐ (or poly‐) dimethylsiloxanes (1b – d) in the presence of pyridine. The hydroxyl derivatives 5a – d were obtained by hydrolysis of the acetoxy derivatives, and the 3‐(2,3‐epoxypropoxy)propyl derivatives 6a, b by reaction of the diols with 1‐chloro‐2,3‐epoxypropane.
Synthèse de polysiloxanes téléchéliques, 2. Synthèse de diamines aromatiques
Authors: Boutevin Bernard , Robin J. J.
Published: April 2003

Telechelic aromatic diamines (11) containing an oligo‐ or polysiloxane chain were prepared in a 4‐step synthesis. In the first step 1‐allyloxy‐4‐nitrobenzene (6) was synthesized and subsequently hydrosilylated with chlorodimethylsilane. In the third step the product (7) was hydrolyzed or condensed with α‐hydro‐β‐hydroxyoligo‐ or polydimethylsiloxane (9a or 9b). In the last step the nitro groups were reduced into amino groups. The steps were controlled by means of 1H and 29Si NMR spectroscopy.
Polymerization of bis[4‐bis(2,3‐epoxypropyl)aminophenyl]methane. Identification of new derivatives of 3‐hydroxy‐1,2,3,4‐tetrahydroquinoline
Authors: Costes Bruno , Reyx Danièle , Platzer Nicole
Published: April 2003

Bis[4‐bis(2,3‐epoxypropylamino)phenyl]methane (3) was shown to undergo homopolymerization when heated without or with an accelerator such as N,N‐dimethylbenzylamine (10). When 3 was polymerized without accelerator, no ether formation was found. A new type of curing process involving opening of the epoxy ring by reaction at the phenyl ring in ortho position to the tertiary amino substituent allows one to explain the formation of compounds containing the 3‐hydroxy‐1,2,3,4‐tetrahydroquinoline moiety. The corresponding derivatives 4–7 were isolated for the first time and their structures established by different spectroscopic methods such as 1H, 13C, 2D δ‐δ NMR, and FT‐IR. Intermolecular reaction at the orthocarbon of the tertiary amino group with an epoxy group may explain the resin formation by curing 3 without accelerator. Polymerization of 3 with accelerator 10 led to polyetherification. This result may be explained in terms of difference in the reactivity of the tertiary amines 3 and 10 towards the epoxy group. The former gives an unstable “zwitterion” by reaction at the nucleophilic carbon, subsequently leading to the stable hydroquinoline system by proton transfer. The latter also gives an unstable “zwitterion” by reaction at the nucleophilic nitrogen, however, it induces epoxy ring‐opening polymerization due to the lack of intramolecular stabilization. Moreover, the results suggest that the hydroxyl functions, formed in the absence of an accelerator, do not react with epoxides under the studied conditions.
Chromatographic cross‐fractionation of statistical copolymers of styrene and 2‐methoxyethyl methacrylate
Authors: Glöckner Gottfried , Stejskal Jaroslav , Kratochvíl Pavel
Published: April 2003

Chromatographic cross‐fractionation (CCF) by preparative size‐exclusion chromatography (SEC) and gradient high‐performance liquid chromatography was applied to stat‐copoly‐(styrene/2‐methoxyethyl methacrylate). Two specimens were analyzed, which had been polymerized from the same batch of monomer mixture in benzene solution to either low or high conversion (10,1 or 86,4 mass‐%, respectively). The initial monomer mixture contained more styrene (76,7 mass‐%) than the azeotropic one (39,4%). The integral chemical composition distribution (CCD) of the low‐conversion sample agreed with the theoretical curve, whereas the calculated CCD of the high‐conversion specimen was broader than the one determined experimentally. The contour map of the low‐conversion sample exhibited the tapering effect of molar mass predicted by theory. The corresponding map of the high‐conversion sample showed that the composition shift towards the initial monomer ratio induced production of macromolecules of higher molar mass.
Azo polymers — syntheses and reactions, 3. Photolysis of monomeric and polymeric azo compounds
Authors: Nuyken Oskar , Weidner Richard , Dörner Barbara , Grunow Arthur
Published: April 2003

Unsymmetrical azo compounds of the general structure m‐RC6H4NNC(OCOCH3) (R1) (R2) (2–4), in which R stands for H, CH3, CHCH2 or a polymeric residue, were irradiated with light of λ ≥ 330 nm. Depending on the substituents R1 and R2 and the reaction temperature trans‐cis isomerization or/and decomposition was observed. Polymers containing azo groups and CC‐double bonds can be crosslinked by irradiation.
Chain extension of poly(dimethylsiloxane) having hydroxyl or vinyl terminal groups
Authors: Shara Mohammed A. , Mark James E.
Published: April 2003

Chain extension of hydroxyl‐ or vinyl‐terminated poly(dimethylsiloxane) was carried out with difunctional end‐linking agents that are similar in their structure to the higher functionality end linkers used for model network formation. Values of the number‐average molecular weight of the polymers before and after chain extension were determined by gel permeation chromatography. In this way, values of the extent of reaction, p, were determined for different stoichiometric ratios, r. They were found to be in the range 0,5–1,0, with the largest values generally corresponding to r closest to unity. Increase in reaction time increases p, but increase in the amount of catalyst did not show any discernible effect. The overall results show that at least under some conditions, the analogous reactions using end linkers of functionality three or higher should produce nearly perfect model networks.
Microstructure of syndiotactic polypropylenes prepared with heterogeneous titanium‐based Ziegler‐Natta catalysts
Authors: Kakugo Masahiro , Miyatake Tatsuya , Naito Yukio , Mizunuma Kooji
Published: April 2003

Polypropylenes produced with various heterogeneous titanium‐based Ziegler‐Natta catalysts were fractionated by solvent extraction technique. The infrared analysis of the fractions indicates the presence of a crystalline syndiotactic sequence, soluble in xylene at 20°C, and boiling hexane soluble fractions of all samples examined. Highly syndiotactic polypropylene (proportion of rrrr pentad is 0,50), comparable in syndiotacticity to the syndiotactic polymer prepared at −78°C with a homogeneous vanadium catalyst, was separated from the xylenesoluble fraction of the polymer prepared with the system TiCl3‐Al(C2H5)2Cl by means of elution column fractionation. The steric irregularities are mainly rrrm and rrmr (ratio ≈ 1:1), suggesting that the propagation is controlled mainly by end‐groups. Chemical inversions, i. e., head‐to‐head or tail‐to‐tail linkages of propylene units, are practically absent, though they are seen in syndiotactic polypropylenes prepared with vanadium catalysts.
The ability of macromonomers to copolymerize: A critical review with new developments
Authors: Gnanou Yves , Lutz Pierre
Published: April 2003

The first part of this article critically examines the various studies dealing with the ability of macromonomers to copolymerize. The conclusions drawn from these investigations, concerning the influence of the molecular weight of the macromonomer on its reactivity, are contradictory. Owing to the systems selected, other parameters are also involved in the reactivity of macromonomers that make it difficult to settle the controversy. In the second part, our own results on the reactivity of macromonomers are reported. The system chosen exhibits the advantage to remove all the complicating features connected with the incompatibility between polymers. It results that the side group associated with the unsaturation plays the major role in decreasing the reactivity of the macromonomer which is shown in addition to be independent of the macromonomer chain length. The criteria allowing to predict, for a given system, the macromonomer behaviour in a copolymerization process are also given.
Spatial organization of homopolymer chains inside spherical polybutadiene domains of styrene‐butadiene diblock copolymers
Authors: Cheng Pao‐Luo , Berney Charles V. , Cohen Robert E.
Published: April 2003

Blends of perdeuterated polybutadiene and a styrene‐butadiene diblock copolymer (polystyrene‐block‐polybutadiene) were prepared by solution‐casting techniques. Small‐angle neutron scattering and transmission electron microscopy experiments on blends containing homopolymer with chain length smaller than the corresponding block sequence showed that homopolymer chains are solubilized by the spherical microdomains up to a homopolymer content of about 15 mol‐percnt;. The solubilized homopolymer is distributed in a spatially uniform manner throughout the domain volume and the radius of gyration of the homopolymer is only slightly larger than that of an unperturbed chain in bulk. At about 18 mol‐percnt;, pools of homopolymer appear outside the microdomains; the change in scattering intensities indicates that pool formation is a kinetic phenomenon rather than a thermodynamically controlled event. Experiments on blends containing longer homopolymer chains revealed a lower concentration, between 3 and 6 mol‐percnt;, for the onset of homopolymer pool formation.
Anionic polymerization of one‐ended “living” strontium‐polystyrene in tetrahydropyran in the presence of tetraglyme and in benzene
Authors: De Smedt Constant , Van Beylen Marcel
Published: April 2003

The anionic polymerization of the strontium salt of one‐ended living polystyrene (SrS2) was investigated at 20°C in tetrahydropyran (THP) in the presence of two different concentrations of added tetraglyme. Similarly to BaS2 in tetrahydrofuran (THF) and to SrS2 in THF and in pure THP, the observed pseudo‐first‐order rate constant of propagation, kobs, was nearly independent of the total concentration of salt, their values being 7,5.10−3 s−1 and 9 · 10−3 s−1, respectively, i. e. about 100 to 120 times higher than in pure THP. This indicates that the propagation occurs mainly via an increased but constant amount of free S− anions resulting from the two already known equilibria SrS2 ⇌ (SrS)+ + S−(K1) and 2 SrS2 ⇌ (SrS)+ + (SrS3)− (K2) and the equilibrium of glymation (SrS+) + G ⇌ G, (SrS)+ (Ki). A small not exactly determinable contribution of glymated ion‐pairs and/or triple ions, whose rate constants would then probably be of the order of 18 l · mol−1 · s−1 and 80 l · mol−1 · s−1, respectively, could not be excluded. The glymation constant Ki was found to be about 3 · 106 1 · mol−1, i.e., approximately 17 times greater than for the Na+ cation. Finally, a kinetic experiment with SrS2 at 20°C in pure benzene (contaminated, however, with some remaining THP from the preparation of SrS2) indicated that propagation by ion‐pairs is possible with a bimolecular apparent rate constant Kapp = 1,1 · 10−1 l · mol−1 · s−1.