bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase distribution chromatography (PDC) as a method for the investigation of polymers in solution, 4. Deformation concept
Authors: Greschner Georg S.
Published: April 2003

In a previous paper of the author the assumption was stated that the separation mechanism of phase distribution chromatography (PDC), based on a flow equilibrium (steady state) of the transported polymer between the mobile and the stationary phase of the polystyrene/cyclohexane PDC column, can be explained by means of a deformation of the sorbed polystyrene coils by the velocity gradient along the surface of the stationary phase of the column. In this paper this assumption is tested by means of the theory of rubber elasticity applied to the polystyrene coils sorbed on the surface of the polystyrene gel. The velocity gradient near the surface of the gel is estimated by means of the equations of Hagen‐Poiseuille and the deformation of the coil caused by this gradient is calculated from experimental data. The results show that the deformation concept can explain the PDC separation mechanism found from the measurements and published previously.
Phase behaviour and structure of polymer surfactants in aqueous solution. The occurrence of lyotropic nematic phases
Authors: Lühmann Bernd , Finkelmann Heino , Rehage Günther
Published: April 2003

The binary phase diagrams are analyzed in aqueous solutions of monomeric, non‐ionic surfactants and the corresponding polysiloxanes having attached the surfactants as side chains via the hydrophobic parts of the amphiphiles. In contrast to common surfactants these hydrophobic parts additionally contain a rigid, mesogenic biphenyl moiety. While the polymeric surfactants exhibit hexagonal and lamellar lyotropic liquid crystalline phases, similarly to the low‐molar‐mass surfactants, two important results have to be emphasized: (i) The liquid crystalline phase regions are markedly extended with respect to concentration and temperature compared with the corresponding monomers, as shown in a similar way for thermotropic polymer liquid crystals. (ii) The phase sequence of the polymorphic liquid crystalline phases can be changed by polymerization. While for the systems under investigation the monomeric surfactant exhibits a cubic phase, the polymeric surfactant shows no cubic but a nematic phase in front of the hexagonal phase at low surfactant concentration. The nematic phase of the polymeric surfactant is the first example for a nematic phase, which is formed for binary mixtures of non‐ionic surfactants and water.
Photo‐oxydation de polyéther‐block‐polyamides
Authors: Gauvin Pascal , Philippart Jean‐Louis , Lemaire Jacques , Sallet Daniel
Published: April 2003

Analytical and kinetic aspects of the photooxidation in the solid state of two polyether‐block‐polyamides 1a and 1b are described. The block copolymers studied contain different fractions of polyether segments. Nevertheless, their photooxidation presents the same features and concerns mainly the ether groups. In both thermoplastic elastomers, 1a and 1b very high stationary concentrations of hydroperoxy groups CH(OOH)OCH2 are observed (0,3 to 0,7 mol · kg−1). These hydroperoxides are, however, photounstable and thermounstable above 60°C. They are converted into hemiacetals OCH(OH)OCH2, saturated esters and formates. The hemiacetal groups are thermounstable, too, and decompose into alcohol and aldehyde groups, the latter being photoxidized in the matrix. The oxygen consumption rate, the primary hydroperoxidation rate, and the rate of accumulation of final products were determined. A mechanism including the photolysis and the thermolysis of the hydroperoxides can account for the formation of the final photoproducts (hemiacetals, esters, formates and acids).
Systèmes réactifs polyuréthannes bloqués, 3. Etude du blocage des fonctions isocyanate par le butanone‐2 oxime et de leur déblocage par 1H NMR à 350 MHz
Authors: Phai Lê Thi , Camberlin Yves , Pascault Jean‐Pierre , Pham Quang Tho
Published: April 2003

The structures of the adducts of 2‐butanone oxime (1) to different diisocyanates were determined by 1H NMR spectroscopy. The reaction of diisocyanate blocking is quantitative. The different adducts of 1 to 4,4′‐methylenediphenyl isocyanate (2), 2‐methyl‐1,4‐phenylene and 2‐methyl‐1,3‐phenylene diisocyanates (8 and 10) and to the isocyanate resulting from α‐hydro‐ω‐hydroxypoly(oxytetramethylene) and an excess of 2, dissociate upon heating to reform the starting materials. The residual water in the NMR solvent reacts partially with the regenerated diisocyanates to give primary amines and then ureas.
Synthesis of polysiloxane graft copolymers by hydrosilylation reactions
Authors: Chujo Yoshiki , Murai Kazuko , Yamashita Yuya , Okumura Yoshio
Published: April 2003

Polysiloxane‐poly(methyl methacrylate) and polysiloxane‐polystyrene graft copolymers of well‐defined structure and composition were synthesized by hydrosilylation. Polysiloxanes with SiH bonds were prepared by equilibrium ring‐opening polymerization of cyclic siloxane oligomers catalyzed by trifluoroacetic acid. Molecular weight and SiH group content were controlled by the feed ratio. Allyl‐terminated poly(methyl methacrylate) and polystyrene were prepared by the reaction of carboxyl‐terminated prepolymers with allyl glycidyl ether. The hydrosilylation reactions of SiH containing polysiloxanes with these allyl‐terminated polymers produced tailor‐made graft copolymers, which were characterized by their 1H NMR and IR spectra.
Studies on chitosan‐induced metachromasy, 2. The reversal of metachromasy by co‐solutes
Authors: Gummow Beryl D. , Roberts George A. F.
Published: April 2003

The influence of co‐solutes on the chitosan‐induced changes in the visible spectrum of the anionic dye C.I. Acid Orange 7 is studied. Addition of neutral electrolytes brings about reversal of the spectral changes, as does the addition of alcohols, urea or excess chitosan. The ease of reversal by electrolyte varies with variation in either the anion or the cation but there are no readily explained trends. The effectiveness of alcohols increases with increasing hydrophobic character, the order being methanol < ethanol < 1‐propanol, whilst the effect of urea is comparable to that of ethanol. Chitosan‐induced metachromasy is also reversed by raising the solution temperature, the spectrum reverting to that of the metachromatic state on cooling down to room temperature. These results confirm that the metachromasy induced in the visible spectra of solutions of some anionic dyes by addition of chitosan is the same as that induced by anionic polyelectrolytes in the spectra of a number of cationic dyes.
Polymerization of styrene and methyl methacrylate by 2,5‐dimethyl‐2,5‐dihydroperoxyhexane, 1. Bulk polymerization
Authors: Baysal Bahattin M. , Bayramli Erdal , Yürük Hüseyin , Hazer Baki
Published: April 2003

A new polymerization initiator 2,5‐dimethyl‐2,5‐dihydroperoxyhexane is used as an initiator for the polymerization of styrene and methyl methacrylate at 80°C. It is found that the rates of initiation for this initiator lie in‐between those of di‐tert‐butyl peroxide and benzoyl peroxide for both monomers. The kinetic results show good agreement between dilatometric and gravimetric measurements for the polymerization of styrene. However, mostly oligomers were obtained at high initiator concentrations with methyl methacrylate. A narrow molecular weight distribution is observed from stress‐relaxation measurements for the polystyrene samples obtained at high conversions.
Emulsion copolymerization of acrylonitrile and butyl acrylate, 2. Effect of a radical scavenger on the rate of copolymerization and the copolymer composition
Authors: Capek Ignác , Bartoň Jaroslav
Published: April 2003

Random copolymers of acrylonitrile and butyl acrylate, covering two sets of compositions, are synthetized by emulsion copolymerization conducted to both low and high conversions. The copolymer formed at low conversion is enriched with acrylonitrile. Addition of a small amount of hydroquinone, however, suppresses the formation of copolymer enriched with acrylonitrile, i.e., the formation of copolymer more homogeneous in composition is favoured. Moreover, the effect of a radical scavenger on the kinetic parameters of the emulsion copolymerization is analyzed. In the presence of a small amount of hydroquinone the molecular weight of copolymer is somewhat increased when compared with that prepared without hydroquinone. In addition, the rate of copolymerization unexpectedly decreases with increasing emulsifier concentration. It is supposed that the recipe ingredients themselves and their reaction products or/and intermediates participate in termination reactions within the monomer swollen polymer particles and probably within the emulsified monomer droplets. The initiation of the emulsion copolymerization of acrylonitrile and butyl acrylate is a two‐step process. The first step starts in the aqueous phase by the primary radicals from the water‐soluble initiator and acrylonitrile. The second step occurs in the monomer‐swollen emulsifier micelles by water‐soluble and ‐insoluble radicals (primary and macroradicals) and by radicals derived from the recipe ingredients.
Characterization of butadiene‐acrylonitrile‐methacrylic acid terpolymer by 13C and 1H NMR
Authors: Kanakavel Meenakshisundaram , Sebastian Thazhathuvettoor V.
Published: April 2003

The proton noise‐decoupled 13C NMR spectra were used to characterize the terpolymer of butadiene (BD), acrylonitrile (AN), and methacrylic acid (MMA) prepared by emulsion polymerisation. Assignments for the various triads of butadiene units adjacent to acrylonitrile in the terpolymer were made by comparing the olefinic and aliphatic carbon resonances of a butadiene (B)‐acrylonitrile (A) copolymer. Measurement of intensities of olefinic resonances in the nitrile environment for the terpolymer gives information about the BBB, BBA, ABB and ABA triads distribution, BBA and ABA being predominant. The intensities of methylene carbon resonances of the various triads for BD units connected to AN show a similar trend. The relative populations of various triads calculated from the peak intensities show that the terpolymer has a random structure. The assignments pertaining to BD units were made by comparison with 13C resonances of polybutadiene. The distribution of trans‐1,4‐, cis‐1,4‐ and 1,2‐units in the terpolymer indicates that the terpolymer has a random structure.
Preparation of 4‐tert‐butyloxocalix[n]arenes and their properties as UV‐absorbers
Authors: Ninagawa Akira , Cho Kazuhiro , Matsuda Haruo
Published: April 2003

5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxy‐2‐oxocalix[4]arene (4a), 5,11,17,23,29,35‐hexa‐tert‐butyl‐37,38,39,40,41,42‐hexahydroxy‐2‐oxocalix[6]arene (4b), and octa‐tert‐butyl‐octahydroxy‐trioxocalix[8]arene (4c) were synthesized via 4‐tert‐butylcalix[4]‐, [6]‐ and [8]arenes from 4‐tert‐butylphenol as a starting material. 5,5′‐Di‐tert‐butyl‐2,2′‐dihydroxybenzophenone (7) was synthesized via 5,5′‐di‐tert‐butyl‐2,2′‐dimethoxybenzophenone (6) from bis(5‐tert‐butyl‐2‐methoxyphenyl)methane (5). 1,4‐Dioxane solutions of 4a, 4b, 4c, 6, and 7 were irradiated. The photostabilities of 4b and 4c were found to be better than those of 4a, 6, and 7. A poly(vinyl chloride) film, containing 0,06 mmol/g of 4b, was found to be most stable against photoxidation.
Ion‐conducting grafted polypropylene film, 1. Controlled oxidation of a polypropylene film for volume grafting
Authors: Narȩbska Anna , Bukowski Zbigniew
Published: April 2003

The oxidation of a polypropylene (PP) film was studied with respect to activation for volume grafting. To attain the content of peroxides adequate for an intended graft level, the five oxidation variables: temperature, time, oxygen pressure and concentrations of initiator and surfactant were optimized. For a statistical analysis, the experiments were planned according to a hyper‐graeco‐latin square. The relation between the reaction variables and the ratio of peroxides and hydroperoxides within the polymer was determined. The distribution of the oxygencontaining products inside the peroxidized PP film was monitored by transmission and attenuated total reflection in the infrared region. The optimum variables enable an oxidation of PP to a desired degree, with peroxide groups uniformly distributed throughout the film, and at minor disturbance of the mechanical characteristics of the material.
Ion‐conducting grafted polypropylene film, 2. Volume grafting of polypropylene and gradient composition of poly(propylene‐g‐acrylic acid)
Authors: Nareska Anna , Bukowski Zbigniew
Published: April 2003

Grafting of acrylic acid onto a pre‐activated polypropylene film was investigated, varying the concentrations of monomer and Fe2+ ‐ions, the polymerization time and temperature. Experiments were planned according to a scheme of a latin square, and statistical analyses were performed for the optimization of the grafting variables. The concentration of ferrous ions was found to be the most significant variable for the graft level. At low concentration, ferrous ions act as activator of grafting but no grafting takes place at relatively high concentrations. The distribution of grafted poly(acrylic acid) within a PP film was examined by microphotometry of the coloured slides of the film. The grafted layer of PP reaches the center only at about 30% of grafted poly(acrylic acid) and up to 70% the distribution of grafted poly(acrylic acid) is still non‐uniform with a decreasing amount of the polyacid from the surface to the center. The film samples containing 30% of grafted poly(acrylic acid) already show conductivity in alkaline media and are interesting ion conducting materials.
Cinétiques de télomérisation, 5. Détermination des degrés de polymérisation moyens cumulés dans les réactions de télomérisation et de polymérisation radicalaires
Authors: Boutevin Bernard , Piétrasanta Yves
Published: April 2003

Two principal methods are described for the determination of the cumulative number‐average and weight‐average degrees of polymerization in polymerization and telomerization reactions. The first method for the calculation of both quantities uses the ratio of monomer concentration and concentration of radicals created. In the second the instantaneous number‐average degrees of polymerization of short intervals of monomer conversion are added up. A comparison of the two methods is given and an application is studied for redox telomerization of ethyl acrylate with carbon tetrachloride.
Mechanism of ring‐opening polymerization of 1‐methylbicyclo[2.2.1]hept‐2‐ene using metathesis catalysts
Authors: Hamilton James G. , Ivin Kenneth J. , McCann G. Malachy , Rooney John J.
Published: April 2003

Polymers of the title monomer have been made using 24 different metathesis catalysts, based on Nb, Mo, W, Re, Ru, Os and Ir compounds. Their structure, determined by 13C NMR spectroscopy, varies from all‐cis (ReCl5) to all‐trans (RuCl3, OsCl3) and from fully biased (head‐tail) to unbiased. The bias stems partly from an inability to from head‐head dyads containing cis double bonds and partly from the dipolar interaction between the propagating metal‐carbene complex and the monomer in forming the [2 + 2] transition state. Arguments are presented to show that the formation of biased polymers proceeds largely through a metal carbene species in which the last‐added monomeric unit has its methyl group adjacent to the metal centre (PH). In high‐cis polymers the sequences of three double bonds are such as to indicate that a kinetic distinction must be made between species in which the previous double bond formed was cis or trans (PHc or PHt), consistent with the observation that high‐cis polymers of related monomers have a blocky cis/trans distribution.
Use of the DEPT pulse sequence to facilitate the 13C NMR structural analysis of lignins
Authors: Bardet Michel , Foray Marie‐Françoise , Robert Danielle
Published: April 2003

One of the multipulse sequences in FT 13C NMR, the DEPT pulse sequence, was used to decrease the complexity and to improve the information content of 13C NMR spectra of macromolecules such as milled wood lignins (MWL) extracted from hardwoods (Birch and Aspen MWL). This sequence gives the possibility to edit subspectra selectively for CH, CH2 and CH3 carbons, and benefits from a large intensity enhancement for the carbon atom signals, due to polarization transfer. Thus, it is possible to discriminate precisely between quaternary and tertiary aromatic carbon atoms and to show unambiguously the presence of p‐hydroxybenzoate structures in Aspen MWL and their absence in Birch MWL. In addition, the DEPT sequence has made possible the observation of signals which, with classical experiments, are overlapped by others signals, either partially, like the C‐γ signal of syringaresinol units or completely like the C‐α signal in cinnamaldehyde units. Preliminary results indicate that quantitative data might be obtained from the edited spectra.
Synthesis of an electron‐acceptor polymer and its charge transfer complex with an electron‐donor polymer
Authors: Abe Koji , Haibara Susumu , Itoh Yoshihiro , Senoh Saburo
Published: April 2003

A polymeric charge‐transfer complex (CT complex) was prepared from poly(N‐vinylcarbazole) (PVCz) as an electron‐donor polymer and poly[2‐(methacryloyloxy)ethyl 4,5,7‐trinitro‐9‐oxo‐2‐fluorenecarboxylate] [poly(1)] as an electron‐aceptor polymer. Equilibrium constants, K, and thermodynamic parameters for the polymeric CT complex formation and for monomeric model systems were determined. The mole ratio of the components in the CT complex is 1:1 except for the system ethylcarbazole (EtCz)‐poly(1). K decreases in the following order: PVCz‐poly(1) > EtCz‐1 > PVCz‐1 ≫ EtCz‐poly(1). The difference in K is mainly due to the entropy term.
Reversible oxygen‐binding to poly(ethyleneimine)‐cobalt complexes in aqueous solution
Authors: Nishide Hiroyuki , Yoshioka Hiroshi , Wang Shen‐guo , Tsuchida Eishun
Published: April 2003

Cobalt(II) complexes of poly(ethyleneimine)s 1 in aqueous solution are able to form with oxygen a μ‐peroxo adduct as is evidenced from stoichiometry and spectral properties. The oxygen adduct of Co/1 is characterized by its higher rate constant and activation entropy of the oxygen dissociation step, in comparison with those of the low‐molecular‐weight analogue Co/tetraethylenepentamine (2). This is related with the smaller affinity of Co/1 to oxygen and the reversibility in oxygen‐binding. The dissociation of the oxygen molecule coordinated to and bridged with Co/1 is facilitated by a distortion of its μ‐peroxo structure due to electrostatic repulsion of polycationic 1.
Thermotropic polyesters, 2. Synthesis of regular polyesters from aromatic dicarboxylic acids and phenols or aliphatic diols, and study of their mesomorphic properties
Authors: Bilibin Alexander Yu. , Tenkovtsev Andrey V. , Piraner Olga N. , Pashkovsky Evgenii E. , Skorokhodov Serguei S.
Published: April 2003

Several series of thermotropic liquid‐crystalline polyesters, based on 4‐chlorocarbonyl phenyl esters of aromatic dicarboxylic acids (1–4) and phenols or aliphatic diols, were synthesized and studied by polarizing microscopy and differential scanning calorimetry (DSC). A relationship between geometry of mesogenic moiety and stability of mesophase formed by the polymers was established. The effect of both the length and chemical structure of the flexible fragments on the mesomorphic properties was revealed for polyesters obtained from aliphatic diols. Several polymers were obtained whose temperatures of transition into the liquid crystalline state were found to be below 100°C. Two series of low‐molecular‐weight liquid‐crystalline compounds were synthesized to compare their properties with those of the polymers of similar structure. Most of the low‐molecular‐weight analogs have not been described so far. They predominantly form a smectic type mesophase.
Zur Bestimmung der Porenstruktur wassergequollener Cellulosefasern
Authors: Bredereck Karl , Schick Willi Adolf , Bader Evelyn
Published: April 2003

The pore structure of various water‐swollen fibers of cotton and regenerated cellulose was investigated by means of fiber penetration studies with saccharides and dextrans. From the data the volumes of the pores were obtained and average pore diameters and surface areas calculated assuming a slit pore geometry. There are difficulties in interpreting the results with respect to pore‐size distribution. It is shown that the surface areas are suitable parameters of the fiber structure for describing equilibrium dye adsorption of direct dyes in cellulose fibers. From this a simple dying method results for characterizing the pore structure of cellulose materials.
Infrared spectroscopic studies on polyethylene, 6. Linear low density polymers
Authors: Maddams William F. , Woolmington Jacqueline
Published: April 2003

The infrared spectra of five linear low density polyethylenes, containing methyl, ethyl, butyl, isobutyl and hexyl branches, respectively, were measured. Particular interest attaches to the region 800–1200 cm−1 where the spectra, although weak, show significant differences. The findings of an earlier study on the methyl rocking mode, in the vicinity of 900 cm−1, are confirmed and extended. In particular, no band was detected for the ethyl branched polymer and it must be an order of magnitude weaker than for methyl, butyl and hexyl branches. Conversely, it is displaced in frequency and is markedly stronger for isobutyl branches. The methyl wagging mode band is at about 1 150 cm−1 with the methyl branched polymer. It is relatively broad and probably consists of two overlapping components, specific for methyl branches in crystalline and amorphous regions. This mode is not of detectable intensity for ethyl, butyl and hexyl branches but, as with the rocking mode, it is anomalously strong for isobutyl branches.
Evaluation of infrared spectroscopic techniques for analysing chitosan
Authors: Domszy Julian G. , Roberts George A. F.
Published: April 2003

The use of the 3450 cm−1 absorption band as an internal standard in the determination of the extent of N‐acetylation of chitosan from the absorbance of the amide I band at 1655 cm−1 was studied. The results show that the technique gives consistent results that are relatively unaffected by whether the sample is air‐dried or oven‐dried. A number of chitosan samples, covering the range of N‐acetyl values from 14% to 72% were analysed by three techniques: infrared spectroscopy using the ratio A1655/A3450, hydrobromide salt titration and residual salicylaldehyde determination. There is a very good correlation between the results from infrared spectroscopy and those from the other two analytical techniques, confirming the validity of the former technique.
Small angle neutron scattering (SANS) of cyclic and linear polystyrene in toluene
Authors: Ragnetti Maurizio , Geiser Doris , Höcker Hartwig , Oberthür Radulf C.
Published: April 2003

Samples of ring and open chain polystyrene in dilute perdeuterated toluene solution were measured by small angle neutron scattering up to a value of the scattering vector Q = 2 nm−1. The molar masses 12000 ≤ M/(g/mol) ≤ 22000, the mean square radii of gyration 〈R2〉 and the second virial coefficients A2 of the samples were determined. The results are compared to theories which describe the dependencies 〈R2〉 = f(M) and A2 = f(M) for both cyclic and linear chain molecules. A qualitative agreement between theory and experiment is obtained.
Polymorphism in poly(3,3‐dimethyloxetane)
Authors: Pérez Ernesto , Fatou José G. , Bello Antonio , Merino Juan Carlos , Pastor José M , De Saja José A.
Published: April 2003

A detailed study of the polymorphism of poly(3,3‐dimethyloxetane) was carried out by differential scanning calorimetry and X‐ray diffraction. From the relaxed melt state, two modifications, Form II (monoclinic) and Form III (orthorhombic), are separately obtained depending on crystallization temperature. When the crystallization is accomplished for a given modification, this one is stable at any temperature below its melting temperature. However, if the crystallization of a given modification is not complete, the other modification can be crystallized from the amorphous phase. Thus, a possibility of obtaining both forms exists. The kinetic and thermodynamic factors which govern this process are analyzed. The free energies were calculated and the conclusion is that modification II is thermodynamically the most stable one at all temperatures below its melting point.
Enzymatic splitting of side chains in soluble polymers. The effect of length and structure of the side chain
Authors: Labský Jiří , Mikeš František , Blahník Aleš , Vyprachtický Drahomír
Published: April 2003

A series of soluble polymers was prepared by copolymerization of the 4‐nitrophenol ester of N‐methacryloylated ω‐amino acids (1a – i), of N‐methacryloyldiglycine (2b), of 6‐(N‐methacryloylglycylamino)‐ and of 6‐(N‐methacryloylglycylglycylamino)hexanoic acid (3a and 3b) with N‐(2‐hydroxypropyl)methacrylamide (HPMA). The resulting polymers contained roughly 3 mol‐% of nitrophenol groups. Polymeranalogous reaction with 4′‐nitro L‐phenylalanineanilide (4a) or with its N‐glycyl and N‐glycylglycyl derivates (4b and 4c), yielded polymers which at the end of their side chain of various length and structure had a bond degradable with chymotrypsin. The rate of enzymatic hydrolysis was investigated as a function of the length and structure of side chain. It was found that in copolymers possessing side chains formed by ω‐amino acid residues, the rate of hydrolysis increases with increasing length of the side chain. The rate of cleavage of the peptide bond has a maximum value for a spacer that possesses six methylene groups. With increasing length of the side chain the rate of hydrolysis again decreases. A similar dependence was observed for side chains formed by dipeptides of ω‐amino acids and glycine. In copolymers with oligoglycine side chains, the rate of enzymatic hydrolysis also increases with increasing length of side chain. In other types of side chains formed by combination of hydrophobic and hydrophilic segments, a number of factors become operative which affect the rate of enzymatic hydrolysis and are very difficult to specify.
Functional monomers and polymers, 129. Asymmetric robinson cyclization reaction catalyzed by polymer‐bound L‐proline
Authors: Kondo Koichi , Yamano Toru , Takemoto Kiichi
Published: April 2003

The asymmetric Robinson cyclization reaction was studied by using polymer‐bound L‐prolines as catalysts, in which the degree of crosslinking, the content of proline and the spacers of binding L‐proline to the polymers were varied. Incorporation of a spacer for binding the L‐proline moiety onto a polymer support was found to improve the catalytic efficiency considerably, which is reflected by the value of enantiomeric excess.
Peptide synthesis by using polymer‐supported N‐acylphosphoramidites
Authors: Kawanobe Wataru , Yamaguchi Kazuo , Nakahama Seiichi , Yamazaki Noboru
Published: April 2003

Diethoxyphosphino‐substituted acetamides (1 and 2) and the polymer gel bearing dialkoxy‐phosphino groups (3,4, and 5) were prepared by reaction of chlorophosphites with acetamide and crosslinked polyacrylamides, respectively, in the presence of triethylamine. By using 1,2 and the polymer as condensing reagents, various peptides were synthesized directly from N‐protected amino acids and amino acid esters in high yields with little racemization. The highly crosslinked polymeric reagents simplified the procedure and were recycled by treatment with chlorophosphites.
Copolymerization of styrene with α‐chloromaleic anhydride, 1. Mechanism of the radical‐initiated copolymerization in 1,4‐dioxane
Authors: Nagai Katsutoshi , Akiyama Kazuhiko , Kuramoto Noriyuki
Published: April 2003

The radical‐initiated copolymerization of styrene (ST) with α‐chloromaleic anhydride (CMA) in 1,4‐dioxane was investigated. The formation of a 1:1 charge transfer (CT) complex between the comonomers in 1,4‐dioxane at 25°C was confirmed by UV‐spectroscopic studies, and the formation constant was found to be near zero, indicating that the complex is of contact type. An alternating copolymer was obtained by copolymerization over a relatively wide range of feed composition, and the monomer reactivity ratios, rST and rCMA, were found to be 0,07 and 0,00, respectively, at 60°C. The copolymerization at a constant total monomer concentration showed a maximum rate at a styrene mole fraction of 0,4 in the feed. The copolymerization was interpreted by a consecutive monomer addition mechanism without taking into account a participation of the CT complex in the propagation.
Caractérisation et étude physicochimique du polydiméthylsiloxane en bon solvant
Authors: Lapp Alain , Herz Jean , Strazielle Claude
Published: April 2003

The physicochemical properties of a series of polydimethylsiloxane were investigated in dilute solution of toluene by viscosity, light scattering and on‐line light scattering/gel permeation chromatography (LS‐GPC). The viscosity law is determined, in order to compare GPC data and LS‐GPC. The disagreement between these data is explained in terms of cohesion energy. The light scattering data are corrected for polymolecularity effects, in order to determine the excluded volume exponent v and the value of the interpenetration function ψ in the asymptotic domain. These values are in good agreement with the critical exponents obtained using the argument relying on renormalization theory.
Aqueous polymerization of vinyl monomers in the presence of surfactants, 1. Acrylamide
Authors: Bartoň Jaroslav , Juraničová Viera , Vašková Viera
Published: April 2003

The kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in water were studied in the presence of the anion‐active emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polyacrylamide, but it showed no effect on the rate of polymerization. The transfer constants to the emulsifier and the initiator were determined and amounted to of 3,6 · 10−3 and 5 · 10−3. The ratio of rate constants of termination and propagation kt / kp2 = 6,9 · 10−2 mol · dm−3 · s, determined for the polymerization of acrylamide in the presence of the emulsifier, is almost identical with the value for the polymerization without emulsifier. Thus, propagation and termination reactions of the potassium peroxodisulfate initiated polymerization of acrylamide in water are not influenced by the emulsifier.
4‐(α,α‐dimethylbenzyl)phenyl methacrylate, 1. Synthesis and crystal structure
Authors: Viersen Frits Jan , Tan Y. Yong , van Bolhuis Fré , Zwiers Renso J. M.
Published: April 2003

4‐(α,α‐dimethylbenzyl)phenyl methacrylate (1) was prepared by reaction of 4‐(α,α‐dimethylbenzyl)phenol and methacryloyl chloride in ether. By careful crystallization from ether large monoclinic crystals could be obtained with the following crystal data: a = 6,622 (2) Å, b = 12,578 (2) Å, c = 9,892 (3) Å, β = 99,86° (3), Dc = 1,147 g · cm−3, V = 811,1 Å3, M = 280,4, λ = 0,7107 Å, μ = (Mo Kα) = 0,7 cm−1, F(000) = 300, space group P21, Z = 2. Attempts to polymerize the monomer (m.p. 46–48°C) by γ‐irradiation at ambient temperature gave only a small amount of a crosslinked product.
Assoziationsgleichgewicht und kettenstatistik bei der H‐brücken‐assoziation von N‐methylacetamid in tetrachlorkohlenstoff
Authors: Hummel Helmut , Bonart Richard
Published: April 2003

We have shown by a band separation technique that the IR spectrum of N‐methylacetamide in CCl4 contains four absorption bands in the amide I region. Three of them are assigned to CO groups of trans and cis monomers and free end‐groups of associates, respectively. The fourth band stems from associated CO groups. In the NH‐region only two bands, due to free and associated NH groups, are detectable. The findings can be explained in terms of intra‐ and intermolecular interactions. The equilibrium association constants are discussed, and it is shown that the length distribution of the associates does not follow the Schulz‐Flory law.
A study on the mechanism of polymorphic transition β→α in isotactic polypropylene
Authors: Garbarczyk Józef
Published: April 2003

The analysis of the potential energy of the crystal lattice of isotactic polypropylene during the β→α phase transition was carried out. This transformation was realized by rotations and translations within a collection of 10 iPP helices. The lattice energy was calculated by means of the atom‐atom potential method. Results and analysis of the data allow to propose a two‐stage mechanism polymorphic transformation rotation of helices being the first stage. This mechanism is discussed in relation to physico‐chemical conditions of the formation of the β‐modification and also with regard to changes of certain physical properties observed in iPP during the β→α phase transition.
Polymeric phthalocyanines and their precursors, 6. Synthesis and analytical characterization of some octasubstituted phthalocyanines
Authors: Wöhrle Dieter , Hündorf Uwe
Published: April 2003

Starting with 2,3,9,10,16,17,23,24‐phthalocyanineoctacarbonitrile (3a) different octa‐substituted phthalocyanines 4a–7a and 3b–7b with carboxylic acid, anhydride, imido and amido groups were prepared. IR and UV/VIS spectra are discussed in detail and compared with unsubstituted phthalocyanine (1). 3–7 may be considered as low molecular weight analogues of polymeric phthalocyanines 2 with different end groups.
Polymeric phthalocyanines and their precursors, 8. Synthesis and analytical characterization of polymers from 1,2,4,5‐benzenetetracarbonitrile
Authors: Wöhrle Dieter , Marose Ulrich , Knoop Renate
Published: April 2003

Polymers 3 were prepared by reaction of 1,2,4,5‐benzenetetracarbonitrile (2) or 2,3,9,10,16,17,23,24‐(29H, 31H)‐phthalocyanineoctacarbonitrile (5a) with various metal salts or metals. The polymer structures were investigated by comparing their IR and UV/VIS spectra with those of 5. Structurally uniform polymeric phthalocyanines 3 with a number of phthalocyanine units Pc ⩾ 8, containing only nitrile end groups, were obtained from 2 or 5a with various copper salts. By saponification of 3 polymers (Pc ⩾ 3) with carboxylic acid end groups were obtained. The reactions of 2 or 5a with other metal salts or metals yielded polymers of varying structural uniformity. Metal free 3a was also synthesized.
Moisture‐curable rubbers, 3. Moisture‐cure of chlorosulfonated polyethylene
Authors: Yamada Akira , Shiokaramatsu Yoshiyuki , Yamashita Shinzo
Published: April 2003

Chlorosulfonated polyethylene (CSM) was grafted with 3‐aminopropyltriethoxysilane (APS) and the product was cured by exposing to moisture and by using dibutyltin dilaurate (DBTDL) as catalyst for condensation. The moisture‐cured product showed a tensile strength of 7,8 MPa when the amount of APS added was 0,5 equivalent to the amount of chlorosulfonyl groups. The rate constant of the reaction of CSM with APS was found to be 8,5 · 10−2 l · mol−1 · s−1 at 100°C in toluene, which is 850 times higher than that of the reaction of chlorinated butyl rubber with APS. The activation energy and the frequency factor of the reaction were 89 kJ · mol−1 and 2,0 · 1011 l · mol−1 · s−1, respectively. The activation energy of the moisture‐cure of APS‐grafted CSM was determined to be 44 kJ · mol−1.
Heparinizable materials, 5. Preparation and FTIR characterization of polyurethane surfaces grafted with heparin‐complexing poly(amido‐amine) chains
Authors: Barbucci Rolando , Benvenuti Manuela , Casini Giuliana , Ferruti Paolo , Nocentini Mila
Published: April 2003

The chains of poly(amido‐amine) (1) were grafted on the surface of two different polyurethanes (2 and 3), one of which being a commercial product. All the chemical steps of the grafting reaction were monitored by chemical analysis and FTIR spectroscopy. The poly(amido‐amine) was found to be able to form a complex with heparin by electrostatic interaction. The heparin can be totally removed by using a 0,1 M NaOH solution. The heparin adsorbing capacity of the two resulting materials was biologically tested. A constant heparin/poly(amido‐amine) ratio, observed for both polyurethane samples, leads to the assumption that the complex formation reaction proceeds via a defined stoichiometry.
Model glycoconjugates consisting of biantennary N‐glycans coupled to fatty acids: Synthesis and X‐ray diffraction study
Authors: Michel Véronique , Gallot Bernard
Published: April 2003

Isolated glycopeptides of the N‐acetyllactosaminic type, typically present on cell surface membranes, were linked through their NH2‐terminus to activated palmitic acid. The method used was quantitative for negatively charges glycans and for neutral glycans. The liposaccharides thus obtained adopt, in concentrated water solutions, mesomorphic structures which were studied by X‐ray diffraction analysis. The comportment of charged and uncharged liposaccharides was compared.
Liposaccharides with a saccharidic chain of hen ovotransferrin: Synthesis, determination of the mesomorphic structure, and comparison with other liposaccharides
Authors: Santarelli Xavier , Douy André , Gallot Bernard
Published: April 2003

The amphipathic liposaccharide OT 16 was synthesized by coupling activated palmitic acid with the terminal asparagine residue of the glyco‐amino acid from hen ovotransferrin that contains only mannose and N‐acetylglucosamine residues. X‐ray diffraction showed that the liposaccharide OT 16 exhibits a liquid crystalline structure in concentrated water solution and in the dry state. This cubic structure is compared with the structure of other liposaccharides previously synthesized in order to establish the influence of the nature of the saccharidic chains on the liquid crystalline structures exhibited by amphipathic liposaccharides.
Electric field effects on a liquid‐crystalline side chain polymer with a negative dielectric anisotropy
Authors: Goozner Robert E. , Finkelmann Heino
Published: April 2003

The behavior of methacrylic side chain polymers in an electric field was observed for a homopolymer (1) exhibiting a negative dielectric anisotropy compared with a copolymer (2) of positive dielectric anisotropy. Homopolymer 1 orients spontaneously homeotropic and thus enables the determination of the threshold voltage, rise time and decay time. Based on these experimental results the bend elastic constant and viscosity coefficient were estimated using literature values for the dielectric anisotropy. With respect to the bend elastic constant and electrohydrodynamic effects (e.g. Williams Domains) the homopolymer behaves similarly to low‐molar‐mass liquid crystals, while owing to the high viscosity coefficient response times are large in magnitude.
Electrosynthesis of poly(1,4‐phenylene) catalyzed by nickel complexes
Authors: Fauvarque Jean‐François , Digua Abdelouafi , Petit Michel‐Alain , Savard Jacques
Published: April 2003

Conjugated polymers were prepared by electroreduction of aryl dihalides in presence of nickel complexes as catalysts. For instance, poly(1,4‐phenylene) was obtained from 4,4′‐dibromobiphenyl in high yield (85%). According to the coupling mechanism and to IR spectra, the chains of the polymer are expected to have regular para‐linkages and an average length ranging from 6 to 18 phenylene units. The effects of temperature, nature of monomer, catalyst and electrolyte on the yields and on the properties of the polymer were explored.
Re‐investigation of the 4‐nitrophenyl chloroformate activation of dextran. Evidence for the formation of different types of carbonate moieties
Authors: Vandoorne Filip , Vercauteren Ronny , Permentier Dirk , Schacht Etienne
Published: April 2003

Dextran was activated by reaction with 4‐nitrophenyl chloroformate. Analysis of the total carbonate content and the content of 4‐nitrophenyl carbonate moieties during the course of the reaction demonstrate the formation of different types of carbonate moieties. The 4‐nitrophenyl carbonate moieties are transformed into other carbonate structures most likely by reaction with neighbouring polymeric hydroxyls. This process is strongly enhanced by addition of a strong base.
Polymer‐supported bases, 4. Macrolide synthesis from ω‐bromocarboxylic acids using polymer‐supported 1,8‐diazabicyclo[5.4.0]undec‐7‐ene
Authors: Tomoi Masao , Watanabe Takashi , Suzuki Takayuki , Kakiuchi Hiroshi
Published: April 2003

The macrolactonization of ω‐bromocarboxylic acids was carried out in the presence of polystyrene‐supported 1,8‐diazabicyclo[5.4.0]undec‐7‐ene. The macrolide yield was found to be a function of the degree of ring substitution and of crosslinking, which governs the effective concentration of the fixed substrate within the polymeric reagent. The effect of the polystyrene matrix on the macrolide yield in the heterogeneous system was discussed by comparison with the corresponding homogeneous reaction.
Polymerisationsauslösung mit substituierten ethanen, 7. Zum mechanismus des oligomer‐starts
Authors: Błedzki Andrzej , Braun Dietrich , Tretner Hartmut
Published: April 2003

Methyl methacrylate (MMA) oligomers, obtained by radical polymerization of MMA with substituted 1,1,2,2‐tetraphenylethanes, contain one unstable C‐C bond which can be cleaved thermally under common polymerization conditions. This was shown by means of gel permeation chromatography, field desorption mass spectrometry and model compounds.
Reactivity of hydroxyl groups in cellulose towards chlorotri(p‐tolyl)methane
Authors: Jain Rajesh K. , Agnish Shadi Lal , Lal Krishan , Bhatnagar Hari L.
Published: April 2003

The reactivity of primary and secondary hydroxyl groups of cellulose towards chlorotri(p‐tolyl)methane in pyridine was studied in the temperature range of 60 to 100°C. The rate of reaction with the primary hydroxyl groups was found to be 43 times faster than that with the secondary hydroxyl groups of cellulose. The kinetic data showed that the reactivity of chlorotri(p‐tolyl)methane towards primary hydroxyl groups of cellulose is higher than that of chlorotriphenylmethane (trityl chloride). The energies of activation for the reaction of primary and secondary hydroxyl groups of cellulose with chlorotri(p‐tolyl)methane were found to be 39,6 and 43,1 kJ · mol−1, respectively. The reaction was observed to be pseudo first order.
A new convenient synthesis of ortho‐, meta‐ and para‐chloromethylstyrenes
Authors: Monthéard Jean‐Pierre , Camps Marcel , Chatzopoulos Michel , Pham Quang‐Tho
Published: April 2003

Ortho‐, meta‐ and para‐chloromethylstyrenes (4a – c) were prepared by a three‐step sequence starting from the commercial ortho‐, meta‐ and para‐bromobenzyl bromides (1a – c), which were transformed into the methoxymethyl derivatives (2a – c). Coupling of the corresponding Grignard compounds with vinylbromide in presence of a transition metal catalyst led to the methoxymethyl styrenes (3a – c), which were transformed into the desired products by reaction with BCl3. IR, 1H and 13C NMR spectra of the 3 isomers were studied.
Dilute solution properties of poly(allylammonium chloride) in aqueous sodium chloride solutions
Authors: Ochiai Hiroshi , Handa Miho , Matsumoto Hiromi , Moriga Toshinori , Murakami Ichiro
Published: April 2003

Ten fractions of poly(allylammonium chloride) were investigated at 25°C in sodium chloride solutions of various concentrations, cs, by viscosity and light scattering techniques. The molecular weight (Mw)‐intrinsic viscosity [η] relationships were established at four NaCl concentrations. The unperturbed dimensions estimated from the Stockmayer‐Fixman plot are independent of cs. The second virial coefficient A2 and the excluded volume parameter B as well as [η] were found to be proportional to c and to have negative values in the limit of infinite cs. In addition, it was found that the electrostatic part of the expansion factor can be expressed in terms of a reduced parameter (Mw/cs)1/2 in a fairly wide range of Mw and cs.
Ring‐opening polymerization with kinetically controlled enhancement of macrocyclic oligomers or linear macromolecules
Authors: Słomkowski Stanisław
Published: April 2003

The equilibrium and the kinetics of the ring‐opening polymerization accompanied with backbiting and end‐to‐end ring closure are analyzed using computer simulation. The influence of monomer ring strain and competition between back‐biting and end‐biting on the overall kinetic process is evaluated. The results of calculations are compared with examples from the ionic ring opening polymerization of heterocyclic monomers. It is established that in the polymerization of nonstrained monomers fast end‐biting manifests itself by an induction period. In the absence of end‐biting the polymerization of strained monomers yields a system in which the polymer concentration is temporarily higher than at equilibrium (kinetic enhancement in polymer). On the other hand, very fast end‐biting, hindered only in the case of the monomeric species by the ring strain, results in concentrations of the macrocyclics which are transitorily higher than the corresponding equilibrium concentrations (kinetic enhancement of macrocycles). The polymer synthesis with kinetically controlled concentration of cyclics is indicated.
Influence of an external magnetic field on the cross‐linking reaction of 1,4‐polybutadiene with bis(2,4‐dichlorobenzoyl) peroxide
Authors: Martl Michael G. , Schaller Raimund , Hummel Klaus
Published: April 2003

The cross‐linking of (Z)‐1,4‐polybutadiene with bis(2,4‐dichlorobenzoyl) peroxide was investigated between 80 and 100°C under the influence of an external magnetic field (flux density: 1 Tesla) and also without magnetic field. The cross‐linking density was determined by measuring the equilibrium swelling in toluene at 25°C. The statistical evaluation showed that the magnetic field causes a decrease in the cross‐link density. No influence of the magnetic field on the kinetics of the reaction was observed. The results are discussed in terms of the radical pair theory.
Synthesis of novel ordered poly(ester‐amide)s
Authors: Gopal Jayalakshmi , Srinivasan Mahalingam
Published: April 2003

Five different completely aromatic, ordered poly(ester‐amide)s 6a — e were prepared from diphenols 5 and 4,4′‐carbonyliminodibenzoyl dichloride (3). This bifunctional “amide‐acid chloride” was synthesized in two steps by oxidation of 4,4′‐dimethylbenzanilide (1) with permanganate under neutral conditions and subsequent reaction with thionyl chloride. The polymers obtained were characterized by IR spectroscopy and viscosity measurements. Their physical properties like density, solubility, and thermal behaviour were also studied.
Polymers with tertiary amino groups obtained by the reaction between chloromethylated polystyrene and 3‐alkylaminopropionitrile
Authors: Drǎgan Stela , Bǎrboiu Virgil , Csergö Doina , Petrariu Ioan , Dima Mihai
Published: April 2003

Polymers with tertiary amino groups were obtained by reaction of chloromethylated polystyrene (CMPS) with 3‐alkylaminopropionitriles (2a — e). The resulting polymers 3a — e were characterized by elemental analyses, IR and 1H NMR spectra. Kinetic investigation showed that the reaction is characterized by two rate constants, the rate change taking place at a conversion of 45–50%. Viscosimetric studies of the hydrochlorides of polymers 3a — e in water and methanol showed that they behave as polyelectrolytes only in methanol. The abnormal behaviour of water solutions was explained by hydrolysis reaction. To prove the conclusions on the molecular structures of 3a — e and the reactivity of CMPS, a study of the reaction of benzyl chloride with the same amines was performed.