bluuebunny/crossref_metadata_2025 huggingface dataset:
Structures et propriétés diélectriques des poly(α‐acétoxystyréne)s parasubstitués
Authors: Monthéard Jean‐Pierre , Camps Marcel , Belfkira Ahmed , Chatzopoulos Michel , Granger Robert , Jorat Luc , Noyel Gérard
Published: April 2003

The relations between structure and isothermal, dielectric properties of poly(α‐acetoxystyrene)s substituted in para position by OCOCH3 (1a), OCOCH2CH3 (1b), OCOCH2CH2CH3 (1c), OCOC6H5 (1d), OCOCH2CH2Cl (1f) and OCOOCH3 (1g) were studied. The dielectric constants, at 105 Hz and 20 ± 2°C, were found to be: 3,79 (1a), 3,36 (1b), 3,18 (1c), 3,51 (1d), 3,36 (1e), 3,65 (1f) and 3,07 (1g). The polymers 1a–1g do not show any α‐ or β‐transition. Increasing bulkiness of the para substituent gives rise to a decreasing dielectric constant due to an increase of the degree of syndiotacticity, as determined from 1H and 13C NMR spectra.
Selective grafting of hydrogels onto multiphase block copolymers
Authors: De Feng Xin , Voong) (S. T. , Sun Yan Hui , Qiu Kun Yuan
Published: April 2003

Selective graft copolymerizations onto different segments of a poly(ether‐urethane) (PEU) by using two different methods, i.e. ceric salt initiation and controlled oxidation, were investigated. By ceric salt initiation the grafting takes place mainly at the hard segment, while the controlled oxidation gives grafted hydrogels at the soft segment. The effects of different factors on graft copolymerization in both methods including ceric salt concentration, monomer concentration, PEU composition and oxidation time were investigated. Another kind of multiphase block copolymers, a poly(ether‐ester), also can be graft‐copolymerized by both methods.
DRIFT study of functional group interconversions on modified silica surfaces
Authors: Davies Julian A. , Sood Anup
Published: April 2003

Treatment of surface‐activated silica gel with 4‐(chloromethyl)phenyltrimethoxysilane leads to the formation of a modified silica with pendant benzyl chloride surface functionality. Oxidation of this substrate leads to the formation of surface‐attached benzaldehyde functional groups, whereas reaction with sodium ethanethiolate generates a silica gel modified with surface thioether functionalities. Oxidation of the surface thioether groups produces substrates with pendant sulfoxide or sulfone functional groups, depending upon the reaction conditions. Silica gels with surface thioether or sulfoxide functionalities act as heterogeneous supports for transition metals and both substrates exhibit reactivity in bridge cleavage reactions of [Pt2 (μCl)2Cl2(PPh3)2]. All surface‐modified silica gels were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, in conjunction with other techniques. The DRIFT method is shown to be a powerful tool for the characterization of low volume concentration, surface‐modified, insoluble substrates.
Electrochemical polymerization of dithienylethylene, ‐butadiene, and ‐hexatriene
Authors: Tanaka Susumu , Sato Masa‐aki , Kaeriyama Kyoji
Published: April 2003

Conductive poly[(2,2′‐bithiophene‐5,5′‐diyl)‐(1,3‐butadienylene)] (1b) and poly[(2,2′‐bithiophene‐5,5′‐diyl)‐(1,3,5‐hexatrienylene)] (1c) films were obtained from the electrochemical polymerization of the corresponding α,ω‐dithienylpolyenes in the presence of Bu4NClO4 as a supporting electrolyte. These polymers were identified by their IR spectra. The current efficiency was 72 and 82%. Electrochemical polymerization of 1,2‐bis(2‐thienyl)ethylene did not give a film but a powder as product. In the UV spectrum of poly(1b), oxidized with ClO4 as counterion, three bands are observed at 350, 455 and 1 000 nm (shoulder). The last two bands dissappear in the neutral film. ESCA indicates that the S2p peak in symmetrical in the neutral film, but the oxidized films show a shoulder on the higher binding energy side of the peak. The neutral film shows an asymmetrical ESR signal, whereas that of the oxidized one is symmetrical. In air the conductivity decreases to about 20% of the initial value in 70 days, but the neutral film is quite stable.
The influence of molecular interaction on polymerization, 10. On the copolymerization of methacrylic acid with styrene
Authors: Boudevska Hrissanta , Todorova Olga
Published: April 2003

Free radical copolymerization of methacrylic acid (MA) with styrene (St) at 60°C, initiated by 2,2′‐azoisobutyronitrile (AIBN) is carried out in hydrogen‐bond forming solvents and in solvents not capable of forming hydrogen bonds but exhibiting different dielectric constants. The influence of the solvent on copolymerization reactivity ratios, rate of polymerization, composition, molecular weight and polydispersity of the copolymers obtained is shown. The reactivity ratios of methacrylic acid rMA and of styrene rSt are determined by two different methods with good agreement. The values obtained by the Kelen‐Tüdös method are as follows:

in carbon tetrachloride: rMA = 0,54 ± 0,01; rSt = 0,06 ± 0,03;

in chloroform: rMA = 0,51 ± 0,01; rSt = 0,08 ± 0,03;

in acetone: rMA = 0,43 ± 0,00; rSt = 0,65 ± 0,02;

in 1,4‐dioxane: rMA = 0,41 ± 0,02; rSt = 0,59 ± 0,05;

in acetonitrile: rMA = 0,06 ± 0,02; rSt = 0,29 ± 0,00.

Changes of reactivity ratios depending on the medium are explained on the basis of the results from IR and 1H NMR spectroscopy and gel permeation chromatography (GPC).
Effect of alcohols on the thermal denaturation and aggregation of arachin at pH 3,6
Authors: Kella Navin Kumar D. , Rao M. S. Sivaraja
Published: April 2003

The effects of three simple aliphatic alcohols, viz., methanol, ethanol and 1‐propanol, on the thermal denaturation and protein‐protein interactions of arachin at pH 3,6 were studied by melting temperature, electrophoresis, UV difference and fluorescence spectral measurements. Alcohols increase the heat‐induced protein‐protein interactions as shown by gel melting temperature and electrophoretic measurements. UV difference and fluorescence spectral measurements revealed that the addition of alcohols to arachin, before and after heating and cooling, enhances its denaturation. The probable explanation for the promotive effect of alcohols on the thermal denaturation and aggregation of arachin is discussed.
NMR study of poly(phthalidylidenearylene)s
Authors: Zolotukhin Mikhail G. , Panasenko Anatoly A. , Sultanova Venera S. , Sedova Elvira A. , Spirikhin Leonid V. , Khalilov Leonard M. , Salazkin Sergei N. , Rafikov Sagid R.
Published: April 2003

The structure of poly(phthalidylidenearylene)s, synthesized by electrophilic substitution reactions, was studied using 1H and 13C NMR spectroscopy. Homopolycondensation of 3‐aryl‐3‐chlorophthalides 1a – d in nitrobenzene leads to para‐substituted linear polymers 2a – d, whereas polycondensation of phthaloyl dichloride and bis[4‐(3‐chloro‐3‐phthalidyl)phenyl] ether (6) with diphenyl ether results in polymers 5 containing irregular units.
On the reactivity of phosphonyl radicals towards olefinic compounds
Authors: Sumiyoshi Takashi , Schnabel Wolfram
Published: April 2003

Phosphonyl radicals of the structure OṖR1 (R2) with R1 and R2: C6H5(1); C6H5, OCH(CH3)2(2); CH3, OCH3(4) and OC2H5(5) were generated by UV‐photolysis of appropriate acylphosphine oxides or acylphosphonates which are effective initiators of the free radical polymerization of olefinic compounds. All five radicals are very reactive towards monomers such as methacrylonitrile, styrene and methyl methacrylate (k = 5 · 107 to 2 · 108 1 · mol−1 · s−1), as was found by employing laser flash photolysis techniques. In the cases of acrylonitrile, methyl acrylate, butyl vinyl ether, and vinyl acetate k ranged from 106–107 1 · mol−1 · s−1. The high reactivity of the radicals 1 – 5 is due to their tetrahedral structure. The Q‐e scheme of Alfrey and Price proved useful to recognize trends in the dependence of k on the chemical nature of both phosphonyl radicals and monomers.
Mechanism of chain propagation in “living” polypropylene synthesis. 1H and 13C NMR analyses of chain‐end structures
Authors: Doi Yoshiharu , Nozawa Fumie , Murata Masahide , Suzuki Sigeo , Soga Kazuo
Published: April 2003

The mechanism of chain propagation in the living coordination polymerization of propene initiated by the soluble V(acac)3/Al(C2H5)2Cl catalyst was studied by 1H and 13C NMR analyses of iodine‐terminated polypropylenes of low molecular weights (Mn = 630 to 3200). A vanadium‐carbon bond in the living polypropylene end reacts quantitatively with the iodine molecule to yield a new iodine‐polymer bond. The 1H and 13C NMR analyses of iodine‐bonded polypropylene provide direct evidence on the stereochemistry of the first and last inserted propylene units and the structure of the living polypropylene end.
Preparation and characterization of poly[oxy(2,6‐dimethyl‐1,4‐phenylene)] with functional end groups
Authors: Risse Wilhelm , Heitz Walter , Freitag Dieter , Bottenbruch Ludwig
Published: April 2003

The oxidative polymerization of 2,6‐dimethylphenol (1) and the halogen displacement polymerization of 4‐halo‐2,6‐dimethylphenols (4) yielded poly[oxy(2,6‐dimethyl‐1,4‐phenylene)] (2) with one phenolic end group. 2,2′,6,6′‐Tetramethyl‐4,4′‐isopropylidenediphenol (9a) was used as comonomer in both polymerization reactions to obtain polymer 10a, containing two phenolic end groups. Polymers of different molecular weight were synthesized by variation of the mole ratio of the comonomers. The polymers were characterized by GPC, NMR spectroscopy and end group analysis.
Copolymerization of styrene with α‐chloromaleic anhydride, 2. Spontaneous copolymerization in 1,4‐dioxane
Authors: Nagai Katsutoshi , Akiyama Kazuhiko , Kuramoto Noriyuki
Published: April 2003

α‐Chloromaleic anhydride (CMA) copolymerizes spontaneously with styrene (ST) at a higher rate than maleic anhydride (MA), and α,α′ ‐dichloromaleic anhydride (DCMA) does not copolymerize, even in the presence of a radical initiator. The results obtained from the copolymerization of ST with CMA in 1,4‐dioxane in the absence of a radical initiator are as follows: the copolymerization is strongly accelerated by UV‐irradiation; the monomer reactivity ratios of ST and CMA at 60°C are 0,06 and 0,00, respectively; the over‐all activation energy of the copolymerization is 77,4 kJ · mol−1 (18,5 kcal · mol−1); the maximum rate of copolymerization at a constant total monomer concentration is observed at a mole fraction of ST of 0,4 to 0,5. The rate of copolymerization at equimolar feed composition is of second order with respect to the total monomer concentration. From the results obtained here and shown in the preceding paper, it was inferred that initiating radicals for the spontaneous copolymerization are formed through a charge transfer (CT) complex between the comonomers.
Use of organophosphorus(V) sulfides for the modification of propene polymerization catalysts
Authors: Karayannis Nicholas M. , Lee Sam S.
Published: April 2003

Studies of various organophosphorus(V) sulfides, including esters of thiophosphoric acid and triorganophosphine sulfides, were evaluated as propene polymerization catalyst modifiers. Among these, triethyl thiophosphate (1a) leads to the best activity‐stereospecificity combinations. Higher alkyl or aryl esters of thiophosphoric acid lead to higher catalyst activities but significantly poorer stereospecificities, relative to 1a, while the latter modifier is advantageous over triaryl‐ or tris(diakylamino)phosphorus sulfides, as far as both activity and stereospecificity are concerned. Organophosphorus(V) sulfides appear to be better modifiers in general than the corresponding oxides. No straightforward correlations of the modifying effects of the preceding compounds to the inductive and steric effects of the substituents on phosphorus were possible, as some of these compounds (namely the thiophosphoryl or phosphoryl alkyl esters) may undergo dealkylation reactions with the components of the catalyst system, yielding alkyl chloride, traces of HCl and alkene, and polymeric metal (Ti3+ or Al3+) complexes with anionic R2POS− ligands. A number of binary modifier (1a plus an additional modifier) packages with attractive performance characteristics were developed. Evaluations of these systems in 2 h bulk propylene polymerizations showed that use of triphenylantimony oxide (8) as additional modifier leads to the best overall catalyst performance (yield: 2636 g/g AA TiCl3; hexane extractables: 0,80%). With the 1a‐collidine (9) modifier package, comparable stereospecificity but substantially lower catalyst activity were realized, while use of bis(tributylin) sulfide (6), tributyl phosphite (7) or 2,5‐dimethyltetrahydrofuran (10) as additional modifiers led to good yields (2650–3000 g/g AA TiCl3) but more than double (1,70–2,00%) the hexane extractables, relative to the 1a–8 modifier system.
Phase separations in binary mixtures of nematic liquid crystal side chain polymers and low‐molar‐mass nematic liquid crystals, 1. Influence of the chemical constitution of the low‐molar‐mass component
Authors: Benthack‐Thoms Heidi , Finkelmann Heino
Published: April 2003

Phase diagrams of binary mixtures consisting of a liquid crystal (LC) side chain polymer and low‐molar‐mass liquid crystal compounds are investigated. The pure components are very similar in their chemical constitution and contain the same mesogenic moiety. Both components exhibit a nematic phase. Their miscibility behaviour is drastically influenced by varying the alkyl chain length of the substituent of the low‐molar‐mass LC. With increasing length of the substituent the miscibility becomes smaller in the nematic and also in the isotropic phase and a phase separation takes place with two nematic or two isotropic phases of different composition coexisting.
Aqueous polymerization of vinyl monomers in the presence of surfactants, 2. Methacrylamide
Authors: Bartoň Jaroslav , Juraničová Viera , Vašková Viera
Published: April 2003

The kinetics of the polymerization of methacrylamide initiated by potassium peroxodisulfate in water and 2,2′‐azoisobutyronitrile (AIBN) in a water/ethanol mixture (mass ratio 9/1) were studied in the presence of the emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polymethacrylamide, but it showed no effect on the polymerization rate. The transfer constant to the emulsifier determined amounts to 1,8 · 10−2. The polymerization rate is proportional to the square root of the potassium peroxodisulfate concentration and to the first power of the methacrylamide concentration. During initiation by AIBN, the exponent of the concentration of AIBN in an equation expressing the dependence of the polymerization rate on AIBN concentration amounts to 0,82; the exponent of methacrylamide concentration is equal to 1. The activation energy for the polymerization initiated by K2S2O8 is 67 kJ · mol−1, whereas for the polymerization initiated by AIBN it is 44,0 kJ · mol−1.
Thermotropic liquid‐crystalline polymers, 17. Liquid‐crystalline ordering in the melts of comb‐like macromolecules with mesogenic groups in the side chain. A theoretical model
Authors: Vasilenko Sergei V. , Shibaev Valery P. , Khokhlov Alexei R.
Published: April 2003

A theory of orientational ordering in the melts of comb‐like polymers containing mesogenic groups in the side chains is proposed. A variant of the lattice method is used, which was developed in our previous publication for the analysis of the liquid‐crystalline transition in thermotropic polymers with mesogenic groups in the main chain. A full phase diagram for the system under consideration is constructed and the properties of the corresponding phase transition are determined. It is shown that for polymers with mesogenic groups in the side chain the dependence of the behaviour of the macromolecular main chain on the ordering of the mesogenic groups is much weaker than in the case of linear polymers with mesogenic groups in the main chain.
Polymerizable monolayers derived from crown ether surfactants
Authors: Winter Hans‐Jörg , Manecke Georg
Published: April 2003

Starting from dibenzo‐18‐crown‐6, 1,10‐diaza‐18‐crown‐6 and 1,7‐diaza‐15‐crown‐5, several crown ether surfactants were synthesized. They all form stable monolayers on water. The methacryloyloxy derivative of 1,10‐bis(3‐dodecyloxy‐2‐hydroxypropyl)‐1,10‐diaza‐18‐crown‐6, 2c, could be polymerized in the monolayer by UV irradiation. This polymerizable crown ether surfactant also forms synthetic vesicles by sonication in water.
Nachweis von teilverträglichkeit in den phasengrenzflächen von polymergemischen mittels IR‐spektroskopie
Authors: Könnecke Klaus
Published: April 2003

Among the various methods for determining compatibility in polymer blends infrared spectroscopy, especially the FT IR method, because of its sensitivity, is a rather simple tool to detect specific interactions as a necessary condition for compatibility in polymer blends. As a special advantage, in addition to hints for compatibility, from FT IR spectroscopy informations about the functional groups involved are obtained. By means of FT IR spectroscopy in blends of poly(oxymethylene) (POM) and polymers with ester groups like poly(methyl methacrylate) (PMMA) or poly(tetramethylene terephthalate) (PBTP) the existence of intermolecular interactions between carbonyl groups and the oxygen atoms of POM can be shown. This gives a possibility to detect very weak interactions which cannot be seen with the usual compatibility methods. Nevertheless, such weak interactions may enhance properties like processing behavior or toughness by an increased adhesion between the brittle matrix polymer and the dispersed elastomer phase in impact modified polymer systems.
Adsorption of poly(4‐tert‐butylphenyl methacrylate) on silica from THF/water
Authors: Gargallo Ligia , Radić Deodato , Sarasúa Manuel
Published: April 2003

Adsorption studies of poly(4‐tert‐butylphenyl methacrylate) (PBPh) on silica from a binary solvent (THF/water) are reported. In order to investigate the influence of the composition of the binary solvent on the adsorption of the polymer on a special silica with hydrophobic surface, measurements of the adsorption isotherms were carried out using Aerosil R‐972. The adsorption isotherm of PBPh for the hydrophobic silica/THF solution interface exhibits higher values than the isotherms for hydrophobic silica/aqueous THF solution interfaces. The amount of adsorbed polymer decreases when the water content of the binary mixture increases. The results are discussed in relation to the effects of preferential adsorption of one of the solvents by the polymer.
A theoretical study of conformations and electronic band structures for two benzoxazole polymers
Authors: Nayak Kasinath , Mark James E.
Published: April 2003

The extended Hückel method within the tight‐binding approximation was applied to two benzoxazole polymers of a type much studied because of their excellent mechanical properties. Specifically, band structure calculations were carried out in part to identify the most stable conformation of the polymers in the crystalline state. In the preferred conformation of one polymer the rotational angle between the bibenzoxazole groups is 20°, and that between the bibenzoxazole group and the p‐phenylene group is 0°. The other polymer consists simply of benzoxazole groups, and these are predicted to be coplanar. The above conformational predictions are in excellent agreement with the results of both experimental and theoretical studies on relevant model compounds. In addition, the band gaps in the axial direction were found to be 1,86 and 2,31 eV, respectively, and these values are close to the corresponding experimental values 1,4 to 1,8 eV reported for trans‐polyacetylene. In both benzoxazole polymers the band gap was found to increase with increase in nonplanarity due to the concomitant reduction in charge delocalization.
Morphology, crystallization and thermal behaviour of poly(ethylene oxide)/poly(vinyl acetate) blends
Authors: Martuscelli Ezio , Silvestre Clara , Gismondi Carla
Published: April 2003

Blends of poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc) show a unique value of the glass transition temperature, intermediate between that of plain polymers. The addition of PVAc to PEO causes a depression in both the spherulite growth rate (G) and the overall kinetic rate constant (Kn). Such depression is larger at higher undercooling and, at a given crystallization temperature, it increases with the content of PVAc. The experimental G and Kn data were analyzed by means of latest kinetic theories in order to determine the influence of composition on the process of surface secondary nucleation. The melt behaviour of PEO/PVAc blends cannot be explained only in terms of diluent effects due to the compatibility of the components in the melt. Especially, at lower undercooling it is likely that annealing and morphological effects must also be taken into account. The morphology of thin films of blends, isothermally crystallized from melt, suggests that an amorphous mixed phase (PEO + PVAc) is formed in interlamellar regions. It was found that plain PEO crystals grow according to a regime I process of surface secondary nucleation while in the case of blends the crystals of PEO grow via regime II mechanism.
Polymeric phthalocyanines and their precursors, 7. Synthesis and analytical characterization of polymers from 1,2,4,5‐benzenetetracarboxylic acid derivatives
Authors: Wöhrle Dieter , Preußner Elke
Published: April 2003

Structurally uniform polymeric phthalocyanines 5a–e, containing imido end groups, were synthesized by reaction of different derivatives of 1,2,4,5‐benzenetetracarboxylic acid, 2a–d, with metal salts, urea and a catalyst. 5a–e were converted into polymers 3, 4 and 6, containing anhydride, carboxylic acid and amido end groups, respectively. IR and UV/VIS spectroscopy were used as appropriate methods for describing end groups and structural uniformity. It could be shown that the octasubstituted phthalocyanines 7–10 and not the phthalocyanine 1 must be considered as the low‐molecular‐weight analogues. The number of phthalocyanine units in the polymers was found to be ⩾ 9. The determination of the real molecular weights is not possible, due to the low solubility of the polymers.
Blockcopolymere aus 2‐Isopropenylnaphthalin und Hexamethylcyclotrisiloxan, 7
Authors: Rhein Thomas , Schulz Rolf C.
Published: April 2003

Anionic polymerization of 2‐isopropenylnaphthalene (2‐IPN), with butyllithium in THF at −78°C was terminated with ethylene oxide and the resulting terminal alkoxide was used to initiate the polymerization of hexamethylcyclotrisiloxane (D3) at +40°C. This led to the formation of AB‐block copolymers which were coupled to ABBA‐block copolymers by addition of dichlorodimethylsilane. ABBA‐blockcopolymers were obtained with contents of polymethylsiloxane (poly(DMS)) between 77 and 84% of weight and block molecular weights between 1 700 and 27 000 (poly(2‐IPN)) and 13 000 and 240 000 (poly(DMS)). Phase separation in polymer films casted from different solvents was studied by electron microscopy and by DSC measurements. The block copolymers behave as elastomers in the temperature range from −40 to +190°C. Above 290°C depolymerization of poly(2‐IPN) starts.
Functional monomers and polymers, 127. Application of polymer‐bound nucleic acid bases to high performance liquid chromatography
Authors: Yu Yan Sheng , Kondo Koichi , Takemoto Kiichi
Published: April 2003

Nucleic acid bases and their derivatives, such as cytosine, hypoxanthine and guanine, were linked successfully to polyethyleneimine coated silicagel. These resins were found to separate nucleic acid bases, nucleosides, nucleotides and other purine derivatives efficiently in aqueous solution by means of high performance liquid chromatography.
Changes in molecular structure of ultra‐high molecular weight polyethylene hostalen GUR upon ageing of its solutions at elevated temperature
Authors: Quadrat Otakar , Horská Jitka , Stejskal Jaroslav
Published: April 2003

Changes in solutions of ultra‐high molecular weight polyethylene Hostalen GUR in 1,2,4‐trichlorobenzene with time were studied by means of viscometry and light scattering. The decrease of viscosity during ageing indicates that both the degradation of polyethylene chains and destroying of aggregates may occur. The former fact makes questionable the ultra‐high molecular weight character of the sample.
Hydrodynamic behaviour of 1,4‐trans‐polyisoprene
Authors: Chaturvedi Prakash N. , Patel Chiman K.
Published: April 2003

The unperturbed dimensions of 1,4‐trans‐polyisoprene (TPIP) were estimated using various [η] – Mw extrapolation methods. The results of various methods agree very closely, however, the solvent‐polymer interaction parameter, B, assumes different values from method to method. The polymer chains are found to assume random coil structure in solvents like benzene, toluene and cyclohexane. A more compact coiled structure is found in hexane. This was further substantiated by estimation of the excluded volume per segment: 7,3 Å3 in good solvents and 4,0 Å3 in hexane. On a relative scale, the stiffness parameters for TPIP chains were found to be: σ = 1,26 and C∞ = 5,99 for the expanded coil configuration, and σ = 1,11 and C∞ = 4,46 for the compact coil configuration, which is smaller than the literature data. If the latter are corrected for molecular heterogeneity, the agreement with the present data is excellent. The temperature coefficient of the unperturbed dimensions also supports this results.
Complexes of polyelectrolytes with the enzymes pepsin and α‐chymotrypsin
Authors: Lawton John B. , Mekras Christos I.
Published: April 2003

It was shown that both the enzymes pepsin and α‐chymotrypsin will displace the anionic dye Eosin Y from complexes of the dye with the polycations protamine or polybrene. The dyerelease was monitored fluorimetrically and was found to be strongly time‐dependent. At equilibrium, pepsin released all the bound dye from both polycation‐dye complexes when the mole ratio of pepsin to base moles of polycation were 1 : 10 for protamine and 1 : 13 for polybrene. α‐Chymotrypsin did not release all the bound dye, but appeared to form definite complexes with the polycations. The existence of the complexes between the enzymes and the polycations was correlated with the fact that the polycations are inhibitors of the enzymes. Additionally, it has been shown that pepsin releases Acridine Orange (AO) from a poly(vinyl sulfate) (PVS)‐AO complex. The mole ratio of pepsin to base moles of PVS was found to be 1 : 2,5. Cooperative binding constants were also evaluated for each dye‐polyion system.
Synthesis of a new chelate resin for uranium adsorption from seawater. Polystyrene resin containing two amide oxime functions in the repeating unit
Authors: Kise Hideo , Sato Hisayuki
Published: April 2003

Dicyanoethylated polystyrene, poly{1‐[4‐(2,2‐dicyanoethyl)phenyl]ethylene} (2), which was obtained from the reaction of chloromethylated polystyrene, poly[1‐(4‐chloromethylphenyl)‐ethylene] (1) with malononitrile under phase transfer reaction conditions, was treated with hydroxylamine in methanol to afford a polystyrene resin 3 with two amide oxime functions in the repeating unit. Resins 3 exhibit a higher adsorptivity of uranium in seawater than a corresponding resin 5 with one amide oxime function in the repeating unit. The effective adsorption of uranyl ions by resins 3 is attributed to the close proximity of the two amide oxime functions in the styrene monomeric unit, which can effectively coordinate to a uranyl ion.
N‐substituted methacrylamide copolymers. Novel membranous material for carbon kidney
Authors: Li Xue‐fen , Wang Shen‐guo , Li Zhi‐fen , Gu Han‐qing , Xu Shu‐tao , Liu Xiao‐bing , Zhang He‐shun , Yu Sung‐ting , Ma Teng‐xiang
Published: April 2003

Copolymers of N‐substituted methacrylamide (1a, b), new biomaterials, were synthesized to be used as encapsulating membranes of carbon kidney. In order to obtain a copolymer with a suitable hydrophilic property, the aminolysis of styrene‐methyl methacrylate (St‐MMA) copolymer with N‐(2‐hydroxyethyl)ethylenediamine was carried out under various conditions. The occurrence of aminolysis was confirmed by elemental analysis, IR and 1H NMR spectra. It was shown that a copolymer of N‐substituted methacrylamide with a predictable degree of hydrophilicity can be obtained by controlling the composition ratio of the St‐MMA copolymer and the degree of aminolysis of the copolymer. Hemoperfusion experiments with a living animal (dog), using a minicolumn with several types of microspheric activated carbon encapsulated with various copolymers, showed that copolymers with suitable hydrophilicity and hydrophobicity or with proper structure have a good blood compatibility. Studies with creatinine, uric acid and vitamin B12 showed that microspheric activated carbon, encapsulated with N‐substituted methacrylamide copolymers of proper hydrophilicity and structure, has a good penetration property, and that detaching of activated carbon particles is effectively prevented.
Thermal analysis of the phase transitions of poly(p‐xylylene)
Authors: Kirkpatrick Donald E. , Wunderlich Bernhard
Published: April 2003

Differential scanning calorimetry is used to analyze the phase transitions of various heat‐treated poly(p‐xylylene)s, polymerized from 78 to 296 K. The data were extrapolated, as needed, to completely amorphous or completely crystalline polymer. The glass transition was found to be at 286 K; the increase in heat capacity at the glass transition is 37,6 J · K−1 · mol−1. The crystals of the α polymorph change at 504 K to the β1 polymorph (enthalpy of transition of 5,0 kJ · mol−1), then, at 560 K to the β2 polymorph (enthalpy of transition of 1,5 kJ · mol−1), and finally at 700 K to the isotropic melt (heat of transition of 10,0 kJ · mol−1). Both the β1 and β2 polymorphs are assumed to be conformationally disordered (condis crystals). The reversibility of the transitions, annealing peaks, crystallization on heating, abnormally high heat capacities of β1 crystals, and abnormally low heat capacities of α crystals are discussed.
The structure and time evolution of a cellulose sheet in the nascent fibril produced by acetobacter xylinum
Authors: Kai Akira , Koseki Tomoki
Published: April 2003

Structure and time evolution of a nascent cellulose sheet, produced by Acetobacter xylinum, were examined regarding the resistance of the nascent fibrils to alkali. It became clear that the never‐air‐dried cellulose, obtained after an incubation period of 5 min, changes its morphology after an alkali treatment at very low concentrations (ranging from 1,0 · 10−3 to 1,0 · 10−2 wt.‐%). It is subsequently transformed into cellulose II. On the other hand, although the fibril after an incubation period of 30 min seems to be in a stainable state toward sodium tungstophosphate when it was treated with 4,6 wt.‐% alkali, 70–80% of it maintains the fibrous shape. Electron diffraction experiments, involving the fibrils, indicate a cellulose I structure. Even when the sample after an incubation period of 30 min was treated with 9,6 wt.‐% alkali, about 30% of it still maintains the fibrous shape. Electron diffraction experiments, involving the fibrils, also indicate a cellulose I structure. The shape of a cellulose sheet, just after its extrusion from a cell, seems to be maintained by hydrophobic bonds. The enhancement of the resistance of cellulose toward alkali with time must be due to the development of inter‐and intramolecular hydrogen bonds in each cellulose sheet.
Modified affine law for the elastic and optical properties of low density polyethylene
Authors: Biswas Prabir K. , Sengupta Shyamal , Basu Asok N.
Published: April 2003

A unified study of the anomalous mechanical properties and birefringence of low density polyethylene (LDPE) is attempted within the frame work of the rotating element model. The present paper investigates the validity of the affine transformation rule used in the Ward model and suggests a modified affine law which is based on the consideration that the units are only reoriented and, unlike the affine law, are not deformed due to the uniaxial stretching. The relationship between the angles made by the C‐axis of the unit with the drawing direction in the undrawn state (θ) and the drawn state (θ), is deduced as sin θ = f(n) sin θ′. From the birefringence data of different polymers a two parameter relation of the form f (n) = exp [–(n – 1)α/β] is suggested. Using this new orientation function, the agreement of the predicted values of E0 and E90 for LDPE for the entire draw ratio range between temperatures of 60°C to −125°C, is quite satisfactory. An interesting feature is that the abrupt change in the values of the parameters α and β at two different temperatures may be associated with a phase transition of LDPE at an intermediate temperature.
Comparison of the cationic polymerization of octamethylcyclotetrasiloxane and hexamethylcyclotrisiloxane
Authors: Wilczek Lech , Rubinsztajn Stawomir , Chojnowski Julian
Published: April 2003

Some features of the cationic polymerization of hexamethylcyclotrisiloxane (D3) and octamethylcyclotetrasiloxane (D4) in methylene chloride in the presence of a strong protonic acid (CF3SO3H) were compared. The polymerizations of both these monomers show many similarities, which are taken as evidence for analogies in their mechanisms. In particular, in both cases the reaction is affected by the addition of a small amount of water. The role of water is interpreted in terms of its direct participation in some elementary reactions of the process. The addition of water affects also the state of hydrogen bonding association in the system. Some experimental results together with comments concerning the mechanism of ring formation in the polymerization system are included.
Axially chiral catalysts for the preparation of optically active poly(triphenylmethyl methacrylate)
Authors: Kanoh Shigeyoshi , Suda Hiroshi , Kawaguchi Naotaka , Motoi Masatoshi
Published: April 2003

A variety of axially dissymmetric diphenylylene diamines 1a — 1f were synthesized and evaluated as chiral auxiliaries for the polymerization of triphenylmethyl methacrylate with organolithium compounds such as butyllithium and lithium (±)‐N‐(1‐phenylethyl)anilide in toluene at −78°C. The catalysts containing an optically active biphenylylene derivative of tetramethyl‐ethylenediamine (1e) were found to be particularly useful for the preparation of optically active poly(triphenylmethyl methacrylate) (PTrMA). The catalysts afforded tetrahydrofuran (THF)‐soluble polymers in high yields and the polymers showed large optical rotations arising from a one‐handed helical conformation of a polymer chain. (+)‐ and (‐)‐PTrMAs were obtained by using (S)‐1e and (R)‐1e, respectively. The poly(methyl methacrylate)s derived from these PTrMAs were almost completely isotactic, but showed negligible optical rotations. The other catalysts produced mainly polymers insoluble in organic solvents; the small amounts of THF‐soluble materials showed rather low optical rotations.
Synthesis of a stereoblock poly(methyl methacrylate)
Authors: Doherty Martin A. , Hogen‐Esch Thieo E.
Published: April 2003

The sequential block copolymerization of diphenylmethyl methacrylate (DMA) and trityl methacrylate (TrMA), initiated by diphenyl methyl lithium in THF at ‐78°C followed by hydrolysis and methylation with diazomethane, leads to the formation of an isotacticsyndiotactic stereoblock poly(methylmethacrylate) (PMMA) of narrow molecular weight and block length distribution. Complete conversion of DMA is shown to be essential, since the presence of small quantities of this monomer during the polymerization of TrMA significantly lowers the isotactic content of this block. Polymerization times of at least 12 h were found to be necessary for complete polymerization of the TrMA.
Synthesis of fragments of the terminal inverted repeating units of macronuclear DNA from hypotrichous ciliates
Authors: Schott Herbert , Ruess Heinz
Published: April 2003

The four fragments of the terminal inverted repeating units of macronuclear DNA from hypotrichous ciliates d(A4C4), d(C4A4C4), d(A4C4A4C4) and d(C4A4C4A4C4) were synthesized in preparative amounts (300 mg) by block condensation using the phosphotriester procedure. At first, partially protected nucleosides and mononucleotides were condensed to dimeric blocks using 2,4,6‐triisopropylbenzenesulfonyl chloride and N‐methylimidazole. Longer blocks were synthesized from the dimers using 2,4,6‐triisopropylbenzenesulfonyl chloride and tetrazole. After each condensation the reaction mixture was fractionated using a silica gel column and a step gradient. After synthesis, cleavage of the protecting groups and gelchromatographical separation, d(A4C4) and d(A4C4A4C4) were obtained already as pure substances. On the other hand, having cleaved the protecting groups partially or totally, d(C4A4C4) and d(C4A4C4A4C4) were separated first on QAE‐Sephadex by a salt gradient in 7 M urea. The remaining impurities were removed by preparative reversed phase HPLC. Sequence as well as purity of the DNA fragments were proved by partial enzymatic degradation and two‐dimensional chromatography of the hydrolysates (fingerprint).
Solubility parameter of poly(1,3‐dioxepane)
Authors: Marco Carlos , Bello Antonio , Fatou José G. , Garza Justino
Published: April 2003

Intrinsic viscosity measurements and turbidimetric titrations were made on poly(1,3‐dioxepane) in a series of solvents to determine the solubility parameter δ. The Flory‐Huggins interaction parameter was also used for the same purpose. A value of δ = 9,2 cal1/2 · cm−3/2 was obtained and compared with that calculated from empirical methods. The three‐dimensional solubility parameter approach was also applied in order to obtain informations about the effect of chemical structure on the solubility behaviour.
Struktur und eigenschaften der copolymere aus 1,3,5‐trioxan und 1‐chlor‐2,3‐epoxypropan, 3. Tempereffekte bei copolymerkristallen
Authors: Michnev Bontcho , Mateva Rosa
Published: April 2003

Annealing of copolymer crystals from 1,3,5‐trioxane and 1‐chloro‐2,3‐epoxypropane (epichlorohydrin (ECH)) was conducted in a differential calorimeter (DSC) and the changes in enthalpy and entropy as well as the shape of the melting curves were observed. The changes in melting enthalpy and the shape of the melting curves were found to depend characteristically on the content of epichlorohydrin comonomeric units in the copolymers. A model for the changes of the crystal by annealing is suggested.
Propene polymerization on titanium‐magnesium catalysts, 4. ESR study of TI3+ ions
Authors: Sergeev Sergei A. , Poluboyarov Vladimir A. , Zakharov Vladimir A. , Anufrienko Vladimir F. , Bukatov Gennadii D.
Published: April 2003

The role of Ti3+ ions in titanium‐magnesium catalysts of various composition, TiCl4/MgCl2 + AlR3, TiCl4/MgCl2 + Al(i‐Bu)3 + EB, TiCl4/EB/MgCl2 + Al(i‐Bu)3 and TiCl4/EB/MgCl2 + Al(i‐Bu)3 + EB, was studied by means of ESR. The ESR data and the catalytic properties were compared. It could be shown that the introduction of ethyl benzoate (EB) leads to an increase of stereospecificity, to a considerable increase of the portion of Ti3+ ions which can be observed by ESR, to the appearance of several new signals in the ESR spectra and to an increase of the portion of titanium in solution, removed from the solid catalyst during the interaction with the organoaluminium cocatalyst. Titanium ions are found mainly in the particles or surface associates whose Ti3+ ions produce no signals in the ESR spectra, Ti3+ ions observed by ESR are found to be inactive centers of polymerization. The active centers appear to be localized in highly dispersed particles or surface associates of TiCl3, formed on the MgCl2 surface and are not revealed in the ESR spectra. Increasing stereospecificity in the presence of EB is assumed to be caused by deactivation of non‐stereospecific active centers with ethyl benzoate.
Aqueous polymerization of vinyl monomers in the presence of surfactants, 3. System: Acrylamide/poly(butyl acrylate) latex
Authors: Bartoň Jaroslav , Vašková Viera , Juraničová Viera
Published: April 2003

The kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in aqueous medium is studied in the presence of poly(butyl acrylate) latex. The rate of acrylamide polymerization increases with the concentration of the latex in the reaction system. The increase is especially pronounced at concentrations of solid latex higher than 100 g per dm3 of polymerization mixture. The activation energy of the acrylamide polymerization in the presence of poly(butyl acrylate) latex is 85,8 kJ · mol−1. This value is substantially higher than the value of 70,7 kJ · mol−1 found for the activation energy of the polymerization of acrylamide in the absence of poly(butyl acrylate) latex. A set of reactions is proposed and the equation describing the simultaneous homopolymerization of acrylamide and grafting of poly(butyl acrylate) latex with acrylamide is derived.
Synthesis and thermotropic properties of new mesogenic diacrylate monomers
Authors: Galli Giancarlo , Laus Michele , Angeloni Annino S.
Published: April 2003

A new class of mesogenic α,ω‐alkylene bis[4‐(4‐acryloyloxybenzoyloxy)benzoate]s 1a — 1g were synthesized and studied for their mesophase behaviour. The thermodynamic parameters of the isotropization transition Ti, ΔHi and ΔSi show distinct odd‐even alternations and demonstrate that the thermotropic liquid crystalline properties in homologous series of mesogens can not be a continuous function of the length of the inner spacer segment. It is anticipated that the investigated diacrylates are of value as precursors of thermotropic semiflexible polymers, crosslinking agents for mesomorphic polymer networks and low molecular weight twin model compounds.
Synthesis of water‐soluble polysaccharides and their antitumor activity, 2. Branched polysaccharides from curdlan and curdlan acetate
Authors: Matsuzaki Kei , Yamamoto Iwao , Sato Takaya , Oshima Ryuichi
Published: April 2003

Polysaccharides having β‐glycosidically linked D‐glucose branches were synthesized by condensation of 3,4,6‐tri‐O‐acetyl‐(1,2‐O‐ethylorthoacetyl)‐α‐D‐glucopyranose with activated curdlan (β‐(1→3)‐glucan) and its acetyl derivatives in boiling chlorobenzene in the presence of catalytic amounts of 2,6‐dimethylpyridinium perchlorate. The branched polysaccharides were converted into water‐soluble polysaccharides by saponification and then tested for their antitumor activity. Branched polysaccharides synthesized from unsubstituted curdlan with 60% or more branching and those from curdlan acetate with 30% or more branching are completely soluble in water. The structure of branched polysaccharides obtained from curdlan was determined from methylation analysis, and it was found that branching occurs preferentially at the C‐6 positions by β‐glycosidic linkages. Some of the synthesized branched polysaccharides with high molecular weight show high antitumor activity.
Synthesis of water‐soluble branched polysaccharides and their antitumor activity, 3. Branched polysaccharides from ivorynut mannan, ivorynut mannan acetate and konjak glucomannan
Authors: Matsuzaki Kei , Yamamoto Iwao , Sato Takaya , Oshima Ryuichi
Published: April 2003

Branched polysaccharides of ivorynut mannan (β‐(1→4)‐D‐mannopyranan) and konjak glucomannan (β‐(1→4)‐linked copolymer of D‐mannopyranose and D‐glucopyranose with side chains) having β‐glycosidically linked D‐glucose branches were synthesized by condensation of 3,4,6‐tri‐O‐acetyl‐(1,2‐O‐ethylorthoacetyl)‐β‐D‐glucopyranose with activated ivorynut mannan, ivorynut mannan acetate and konjak glucomannan. When ivorynut mannan was used as main chain polymer, a branched polysaccharide with 11% degree of branching was obtained and found to be 50% soluble in water. Branched polysaccharides from ivorynut mannan did not lead to completely water‐soluble products, even if the condensation reaction was repeated or the acetyl derivative was used as a starting polymer. A branched polysaccharide with 5−10% degree of branching obtained from konjak glucomannan was completely soluble in water with out starting from the acetylated polymer. The structure of these branched polysaccharides was determined by methylation analysis, and it was found that branching of both water‐soluble polysaccharides obtained from ivorynut mannan and konjak glucomannan occurred preferentially at the C‐6 positions. The antitumor activity of these polymers was low as compared to that of branched polysaccharides obtained from cellulose and curdlan.
Biologically active polycations, 6. Polymeric pyridinium salts with well‐defined main chain structure
Authors: Ikeda Tomiki , Hirayama Hiroki , Suzuki Kazuhiro , Yamaguchi Hideki , Tazuke Shigeo
Published: April 2003

Polyesters and polyamides with pendant N‐alkylpyridinio‐4‐ylmethyl groups and definite spacer length between the pyridinio groups were prepared. It was found that the polyesters generally exhibit higher antibacterial activity than the corresponding monomers. Furthermore, the longer the alkyl chain length attached to the nitrogen of the pyridine ring, the higher is the antimicrobial activity. Polyamides with various spacer length were fractionated by gel filtration chromatography to obtain samples with comparable average molecular weights. Antimicrobial assessment of the fractionated polyamide samples demonstrated the existence of an optimum spacer length for lethal action.
Synthèse et étude des propriétés rhéologiques de polyesters stéréoréguliers à base d'acide maléique et d'acide fumarique
Authors: Lacoudre Nelly , Leborgne Alain , Sepulchre Maurice , Spassky Nicolas , Djonlagic Jasna , Jacovic Mihailo S.
Published: April 2003

Pure poly(butylene maleate) and poly(butylene fumarate) of high molecular weights were synthesized by reaction of the corresponding caesium and potassium dicarboxylates with 1,4‐dibromobutane in 1‐methyl‐2‐pyrrolidone at 110°C. During the reaction a substantial amount of oligomeric products, consisting mainly of cyclic compounds, is formed. From the study of the rheological properties at high temperatures (175 to 240°C) it was concluded that some crosslinking occurs rather than isomerization.
Synthesis of spacer‐modified polymer supports with the aid of etherification and phase‐transfer catalytic activity of phosphonium salts derived from the polymer supports
Authors: Tomoi Masao , Shiiki Satoshi , Kakiuchi Hiroshi
Published: April 2003

Spacer‐modified polystyrene supports containing ether linkages were prepared by using chloromethylated polystyrene and 10‐undecen‐1‐ol or p‐hydroxylated polystyrene and 11‐bromo‐1‐undecene as starting materials. The polymerization of p‐(6‐bromohexyloxy)styrene gave also spacer‐modified supports. Phosphonium salts derived from the spacer‐modified polymer supports showed phase‐transfer catalytic activities comparable to those of immobilized phosphonium salts linked to polystyrene by a heptamethylene spacer.
Synthesis of poly(2‐hydroxyethyl methacrylate)‐poly(tetramethylene glycol) ABA type block copolymers and their blood compatibility
Authors: Li Xue‐fen , Chen Chuan‐fu , Li Zhi‐fen , Gu Han‐qing , Lu Mo‐zhu , Han Yu‐zhi , Liu Xiao‐bing
Published: April 2003

2‐Hydroxyethyl methacrylate was polymerized in presence of 2‐mercaptoethylamine to an amino‐semitelechelic poly(2‐hydroxyethyl methacrylate). Poly(tetramethylene glycol) was reacted with 4,4′‐methylenediphenyl diisocyanate to form a diisocyanato‐telechelic poly(tetramethylene glycol). Both prepolymers were linked together by coupling reaction between NH2 and NCO groups in DMF at 0°C, resulting in an ABA type block copolymer. The structure of the product was examined by IR, NMR and SEM. It was found that the block copolymer possesses a microphase separated structure. Animal experiments showed that this ABA type block copolymer has good blood compatibility and excellent permeability for uric poisonous substances.