bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR contact shifts and local conformation in poly(4‐vinylpyridine N‐oxide)‐Ni(II) complexes
Authors: Ghesquière Denis , Chachaty Claude
Published: April 2003

The 1H and 13C NMR contact shifts induced by Ni2+ ions in aqueous solutions were used to elucidate the conformation of poly[1‐(1‐oxo‐4‐pyridyl)ethylene] (1) and of the model compound 1,3‐bis(1‐oxo‐4‐pyridyl)propane (2). The equilibrium position of the pyridine N‐oxide ring relative to the adjacent methine or methylene group was deduced from the angular dependence of the hyperfine coupling of β‐protons and ‐carbons, assuming a twofold potential energy for the rotation about the C4N axis. In the case of 1 it could be shown that the dihedral angle between the plane HβCαC4 and the plane of the ring is 15±5°.
The formation of cyclic oligomers by cationic degradation of poly(phenylthiirane)
Authors: Vancraeynest Wilfried M. , Goethals Eric J.
Published: April 2003

Poly(phenylthiirane)s obtained by polymerization with different initiators were degraded to isomeric cyclic dimers 1, 2, 3, and 4 by treatment with cationic initiators. Analysis of the mixture of the four different isomers gives evidence of a fast transalkylation reaction when a cationic initiator is present in the polymer solution.
Depolarization thermocurrent of polyethylene containing additives
Authors: Lacabanne Colette , Chatain Daniel
Published: April 2003

The influence of antioxidants and ionic agents on Depolarization Thermocurrents (DTC) of low density polyethylene has been studied. Ionic agents increase the height of the potential barrier which + involved in the relaxation observed at highest temperature/lowest frequency at a given frequency/temperature (χ). The relaxations observed at lower temperature/higher frequency (β and γ) are not modified by ionic agents but by antioxidants: the activation energy of the relaxation time increases and the preexponential factor decreases for both β and γ modes. Some of the processes constituting the β and γ modes are non‐ohmic. They may be attributed to charge motions.
A study of methods for measuring the tacticity of poly(vinyl chloride) by proton magnetic resonance spectroscopy
Authors: Robinson Melvin E. R. , Bower David I. , Maddams William F. , Pyszora Henryk
Published: April 2003

60 MHz undecoupled α‐, 90 MHz undecoupled β‐, and 90 MHz decoupled α‐ and β‐proton spectra were measured for seven poly(vinyl chloride) samples, four of these being commercial type polymers, the others were prepared at +75°C, +5°C and −30°C. The results were used to assess the preferred approach to the determination of tacticity. The reproducibility of the values from different solutions of a given polymer is significantly worse than that between a series of runs on a particular solution, showing that sampling errors are larger than those from instrumental sources. Although the 60 MHz spectra were found to be unsatisfactory when interpreted on a first order basis, curve fitting methods, which were similar to those used for the other types of spectra and involved the use of reasonable assumptions for chemical shifts and coupling constants, gave results of comparable precision to those from the two types of decoupled spectra and superior to those from the undecoupled 90 MHz spectra. The preferred approach is to combine the results from α‐ and β‐proton spectra and to examine more than one solution of a given material. The applicability of Bernoullian propagation statistics was assumed in the majority of the curve fitting calculations; in the cases where this was not so the results were used to test this assumption and it has proved to be valid.
Polymerization of vinyl monomers photoinitiated by benzoylated polystyrene
Authors: Bartoň Jaroslav , Capek Ignác , Šušoliak Ondrej , Juraničová Viera
Published: April 2003

The rate of the polymerization of vinyl monomers photoinitiated (at λ = 365 nm) by benzoylated polystyrene in N,N‐dimethylformamide (DMF) decreases in the sequence vinyl acetate>acrylonitrile>methyl methacrylate ≫ styrene ≈ 0 and is related to the rate constant of propagation of the mentioned monomers. In addition to DMF, aromatic hydrocarbons (benzene, toluene, p‐xylene), cyclohexane and tetrahydrofuran were employed as hydrogen donors. The maximum polymerization rate was achieved in the system containing p‐xylene; the system with benzene turned out inefficient for the initiation of acrylonitrile polymerization. Turbidimetric titration of a soluble fraction of the acrylonitrile polymerization in DMF in presence of benzoylated polystyrene showed that the soluble fraction does not contain graft copolymers of benzoylated polystyrene with acrylonitrile. It is assumed, however, that the polyacrylonitrile in the insoluble fraction is bound to benzoylated polystyrene in the form of graft copolymers.
Synthesis of a cationic polyelectrolyte by successive quaternization of 1,4‐bis(2‐diethylaminoethyl)benzene
Authors: Kataoka Kazunori , Ohki Nobutaka , Tsuruta Teiji , Donkai Nobuo , Inagaki Hiroshi
Published: April 2003

1,4‐Bis(2‐diethylaminoethyl)benzene (4), synthesized from 1,4‐divinylbenzene (1) and diethylamine (2) with lithium diethylamide as catalyst, was successively quaternized with 1,4‐dibromobutane (5) to prepare a cationic polyelectrolyte 6 of the ionene type. Apparent molecular weights of the ionene samples were estimated by the sedimentation equilibrium method, and the result is discussed in connection with the true molecular weight. The rate constants for quaternization of first and second nitrogen atom of 4 (k1 and k2) were determined by the use of 13C NMR. It was found that the ratio of the rate constants, (k2/(k1/2)), markedly decreased in the 4/5 system, though it remained unity in the 4 ethyl bromide system.
Homopolymerisation von styrol mit titan(III)‐chlorid/alkylhalogenid‐initiatoren
Authors: Moszner Norbert , Hartmann Manfred
Published: April 2003

The polymerization of styrene initiated by titanium(III) chloride/alkyl halide redox systems was studied. Among the alkyl halides examined, the highest rate of polymerization was found in the system titanium(III) chloride/carbon tetrachloride. The polymerization rate can be described by the equation Rp=k·[Ti(III)]0,5·[CCl4]0,5·[St]1,0. The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 57,3 kJ/mol. It was found that titanium(III) chloride/chloroacetic acid systems, too, could initiate the polymerization of styrene.
Bestimmung von sequenzlängenverteilungen hydrierter polyalkenylene durch metathese‐abbau, 1. Homogen hydriertes polybutadien
Authors: Ast Wolfgang , Zott Christian , Kerber Robert
Published: April 2003

Partially hydrogenated 1,4‐polybutadiene is degraded into GC‐detectable reaction products after olefin‐metathesis with 4‐octene in the presence of WCI6/(CH3)4Sn. 1,4‐polybutadiene is homogeneously hydrogenated with p‐toluenesulfonohydrazide and serves as copolymer with non‐hydrogenated and hydrogenated repeating units. Hydrogenated sequences up to an undecade are detectable. The experimental monomer sequence length distribution agrees satisfactorily with the theoretical one calculated under the assumption of an ideal statistical copolymer.
Syntheses of polyamides containing theophylline and thymine
Authors: Hattori Masahira , Kinoshita Masayoshi
Published: April 2003

2‐(1,3‐Dimethyl‐2,6‐dioxo‐2,6‐dihydropurin‐7‐yl)methylsuccinic acid (2a) and 2‐(5‐methyl‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐yl)methylsuccinic acid (2b) were synthesized via the addition reaction of theophylline and thymine, respectively, to dimethyl methylenesuccinate, followed by hydrolysis of the resulting ester. The dicarboxylic acid derivatives 2a and 2b were further converted to their di‐p‐nitrophenyl esters 3a and 3b, which were allowed to polycondense with diamines such as 1,6‐diaminohexane, 1,2‐diaminoethane, 3‐aminomethylbenzylamine, and piperazine in solutions. The resulting polyamides are white powders with molecular weights in the range of about 2000–6000. The DP of the polyamides varies with the kind of diamines and solvent used. All polyamides are soluble in DMSO and formic acid, the polyamides deriving from esters 3a and 3b and 1,2‐diaminoethane and piperazine are also soluble in water.
Epoxydation de copolymères triséquencés styrène‐isoprene‐styrène par l'acide monoperoxyphtalique
Authors: Pinazzi Christian , Guillaume Pierre , Reyx Danièle
Published: April 2003

Styrene isoprene styrene copolymers (SIS) modified by epoxidizing were investigated in order to obtain adhesive materials. Influences of experimental parameters (concentrations, solvents, compositions of SIS) are shown for epoxidation with monoperoxyphtalic acid at a yield of modification lower than 50%.
Synthesis and exchange reactions of biodegradable drug‐binding matrices
Authors: Ferruti Paolo , Tanzi Maria Cristina , Vaccaroni Francesco
Published: April 2003

Succinic esters of starch and dextrane (STS and DTS) have been prepared and transformed into the corresponding imidazolides. These are difficult to isolate in a pure state. Without previous isolation, however, they react smoothly with alcohols or amines giving the corresponding polymeric esters or amides. STS benzotriazolide has also been prepared, and isolated in a pure state. It has been found to have the same reactivity towards alcohols and amines than other previously described polymeric benzotriazolides. These results demonstrate that STS or DTS activated amides offer new opportunities to prepare polymer drug adducts with a main backbone degradable to safe metabolites in the body fluids.
Effects of mechanical stress on the reactivity of polymers: Shear degradation of polyacrylamide and dextran
Authors: Basedow Arno Max , Ebert Klaus Heinrich , Hunger Hartmut
Published: April 2003

The mechanical degradation of polyacrylamide and dextran and the acid hydrolysis of dextran at different pH values is investigated in concentrated solutions in high shear laminar flow fields. The kinetics of degradation of polyacrylamide show that the reaction is first order, the rate constants of degradation are proportional to the molecular weight, and the polymer molecules are broken preferentially near the center of the chain. It is found that shear stress is the controlling factor of the degradation process, the rate constants increasing in poor solvents and with decreasing temperatures. The limiting molecular weight is a direct function of the shear stress. For dextran a transition range exists in which shear degradation is favored by hydrogen ions at pH values at which no hydrolysis occurs in the absence of a shearing field.
Solution properties and flexibility of poly(2‐biphenylyl methacrylate)
Authors: Alexopoulos John , Hadjichristidis Nikos
Published: April 2003

Dilute solution properties of poly(2‐biphenylyl methacrylate), (poly[1‐(2‐biphenylyloxycarbonyl)‐1‐methylethylene], POB) were studied by viscosity, sedimentation, light scattering and osmotic pressure in different solvents. The solvent dependence of intrinsic viscosity, [η], Huggins constant, KH, Mark‐Houwink exponent, a, and expansion factor, αη, is very weak, although the chemical nature of the solvents is quite different (CHCl3, tetrahydrofuran, benzene, 1,4‐dioxane). For poly(4‐biphenylyl methacrylate) (poly[1‐(4‐biphenylyloxycarbonyl)‐1‐methylethylene], PPB) and other aromatic polymethacrylates the changes of [η], KH, a and aη are very high. The unperturbed dimensions calculated from viscometric and light scattering data by different methods, are in excellent agreement with one another and good agreement with those obtained from sedimentation data. POB has a higher flexibility factor (σ = 2,8) than PPB (σ = 2,7). In our opinion this is due to the fact that the 2‐biphenylyl group is closer to the main chain than the 4‐biphenylyl group. The very high value of σ explains the weak solvent dependence of [η], KH, a and αη in the case of poly(2‐biphenylyl methacrylate).
Potentiometric and viscometric study of the conformational transitions of 2‐hydroxyethyl methacrylate‐methacrylic acid copolymers
Authors: Prokopová Eva , Štol Miroslav , Knižáková Eva , Bohdanecký Miloslav
Published: April 2003

The dependence of the apparent dissociation constant and of intrinsic viscosity on the degree of dissociation of 2‐hydroxyethyl methacrylate‐methacrylic acid copolymers was investigated. It was found that the conformational transition indicated in the potentiometric titration was distinct only with copolymers containing at least ca. 48 mole% of methacrylic acid. The transition is probably related with the local configurational and conformational structure while being uncorrelated with the transition of the coiled form of the macromolecule into the expanded one.
Functional monomers and polymers, 56. Effects of ionic strength on the structure of Cu(II)· poly(vinylimidazole) and Cu(II)· imidazole complexes in aqueous solution
Authors: Sato M. , Kondo K. , Takemoto K.
Published: April 2003

The effect of ionic strength on the structure of Cu(II) complexes of imidazole and poly(4(5)‐vinylimidazole) in aqueous solution was studied by viscometric, spectrophotometric, and electron spin resonance (ESR) techniques. Frequency of the center of the absorption band in visible region (λmax) and ESR spectra of the polymeric Cu(II) complex were different from those of the low‐molecular‐weight Cu(II) complex. The spectra of polymeric Cu(II) complex were different in the presence of sodium perchlorate, but it was not the case for the low‐molecular‐weight Cu(II) complex. The reduced viscosity of the polymeric Cu(II) complex and the polymeric ligand decreased with a rise of the concentration of sodium perchlorate. It was proposed that the conformational change in the polymeric ligand resulted in a structural change of the Cu(II). poly(4(5)‐vinylimidazole) complex.
Solubility and polymer‐solvent interaction parameters of 1,2‐polybutadiene
Authors: Yamashita Shinzo , Minoura Yuji , Maekawa Etsuji
Published: April 2003

The dilute solution behavior of 1,2‐polybutadiene newly developed was not anomalous within the range of crystallinity up to 25%. Therefore, the solubility and polymer‐solvent interaction parameters could be determined by means of usual measurements of dilute polymer solutions. The former has been estimated from viscosity measurement proposed by Mangaraj. The latter was determined using the second virial coefficient obtained from osmotic pressure and light‐scattering measurements.
Absorption of low molecular weight compounds in aqueous dispersions of polymer‐oligomer particles, 2. A two step swelling process of polymer particles giving an enormous increase in absorption capacity
Authors: Ugelstad John , Kaggerud Kari Herder , Hansen Finn Knut , Berge Arvid
Published: April 2003

A novel method for preparation of stable emulsions of slightly water soluble compounds is described. The method implies that the slightly water soluble compound diffuses through water and becomes absorbed into polymer particles which in a previous step have been brought to absorb a water insoluble, relatively low molecular weight compound. By this two step swelling process the polymer particles can be brought to absorb more than 100 times their own volume of the low molecular weight compounds to form stable o/w emulsions of the latter, with high oil content, and with a droplet size and size distribution which is completely determined by the size of the polymer particles in the latex applied initially. Monodisperse emulsions with large droplet size could easily be prepared. When the slightly water soluble compound added in the second step is a vinyl monomer which may subsequently be polymerized, the method represents a seed technique which is especially favourable for preparation of latexes with large particles size, including monodisperse latexes, with high solid content.
Poly(allylbenzene). Dielectric properties
Authors: Boiteux Gisèle , Seytre Gérard , Berticat Philippe , Merle Gérard , Dubois Jean‐Claude
Published: April 2003

Poly(allylbenzene) or poly(3‐phenyl‐1‐propene) belongs to the family of poly‐α‐olefin polymers of known mechanical properties. After synthesis and characterization, the dielectric behaviour of this polymer was determined over a wide temperature range (−32°C to 107°C) at frequencies from 20Hz to 10kHz. The results contribute to the study of the relaxation spectroscopy of poly‐α‐olefins.
La fusion et la cristallisation de la poly(α,α‐diéthyl‐β‐propiolactone): Comparaison avec d'autres polylactones
Authors: Normand Yves , Aubin Madeleine , Prud'homme Robert E.
Published: April 2003

Measurements of crystallization kinetics were made for a sample of poly(α,α‐diethyl‐β‐propiolactone) (DEPL) (syst. name: poly(oxy‐2,2‐diethyl‐1‐oxotrimethylene)). An Avrami exponent of 2 was found indicating a two‐dimensional growth rate of the crystal, following a pre‐determined and heterogeneous nucleation mode. Two melting peaks were found for most samples. The second melting peak (at high temperatures) is probably due to the re‐crystallization of part of the sample initially present under the first melting peak. A value of 21kJ.mol−1 was also determined for the heat of fusion of DEPL by the diluent method. This value leads to a degree of crystallinity of 17% which is about four times smaller than that found for poly(pivalolactone) (syst. name: poly(oxy‐2,2‐dimethyl‐1‐oxotrimethylene)). We have also determined an equilibrium melting temperature of 531 K for this polymer and an entropy of fusion of 40J.mol−1. K−1. Finally, the surface free energies σ and σe for the lamellar crystals were found to be 12.10−7J.cm−2 and 72.10−7J.cm−2, respectively.
Synthesis of 1,3,6,8‐tetraphenyloctane as a tetramer model for polystyrene
Authors: Clouet Gilbert , Brossas Jean
Published: April 2003

The styrene tetramer, 1,3,6,8‐tetraphenyloctane (5), was prepared by addition of styrene and phenethyl bromide (4) in a 1:1 mole ratio to a stirred suspension of lithium in tetrahydrofuran. The reaction was found to proceed via 1,4‐diphenyl‐1,4‐butanediyldilithium (3), which reacts “in situ” with the alkyl halide 4 to give the tetramer 5. Mass and NMR spectra were found to be in agreement with the proposed structures.
Solution properties of poly(N‐isopropylacrylamide)
Authors: Chiantore Oscar , Guaita Marino , Trossarelli Luigi
Published: April 2003

The results obtained by light scattering and viscosity measurements on unfractionated samples of poly(N‐isopropylacrylamide) dissolved in methanol and in water seem to show that the chain molecules assume different conformations in the two solvents. In methanol solutions at 25°C, poly(N‐isopropylacrylamide) (poly[1‐(N‐isopropylaminocarbonyl)ethylene]) molecules apparently behave as normal flexible chains, whereas in aqueous solutions at the same temperature the interactions between polymer molecules and the solvent seem to produce chain uncoiling toward more extended structures which become unstable at higher temperatures.
On the copolymerization of acrylonitrile with styrene in the presence of Lewis acid, 1. Effect of zinc chloride concentration
Authors: Bartoň Jaroslav , Werner Peter
Published: April 2003

The copolymerization of acrylonitrile (AN) with styrene (St) is studied in the presence of Lewis acid (LA) (zinc chloride and zinc nitrate) in homogeneous reaction system. It is revealed that the rate of copolymerization (Rp) only slightly increases with the concentration of Lewis acid in the range of ratios [LA]/[AN]≦0,01 at constant concentrations of comonomers and source of radicals, i. e. 2,2′‐azoisobutyronitrile (AIBN). An increase in Rp appears when the ratio [LA]/[AN]≧0,05 is reached. The dependence of log Rp on log [AIBN] is not linear in the systems containing Lewis acid, but is a function of both the total concentration of Lewis acid and AIBN in the reaction system. For the system St‐AN‐Zn(NO3)2 the dependence of the reciprocal value of molecular weight of copolymer on the rate of copolymerization is linear and does not exhibit the minimum found for the system St‐AN‐ZnCl2. The results of kinetic investigations are interpreted from the view‐point of the present ideas on the mechanism of copolymerization in the presence of Lewis acid.
Polyoxirannes et polythiirannes comportant un centre chiral dans la chaine latérale, 2. Polymérisation de (2RS,3S)‐ et (2S,3S)‐époxy‐1,2 méthyl‐3 pentanes
Authors: Goguelin Michel , Sepulchre Maurice
Published: April 2003

1,2‐Epoxy‐3‐methylpentanes (1) of different diastereoisomeric compositions were polymerized using anionic (tert‐BuOK, KOH), stereospecific (ZnEt2/H2O, ZnEt2/MeOH), or stereoelective (ZnEt2/R(−) 3,3‐dimethyl‐1,2‐butanediol (R( − ) DMBD)) catalysts. In all the cases a preferential incorporation of the (2R,3S) diastereoisomer in the polymer chain was observed. With anionic and coordinated anionic achiral catalysts the election was low but significant, whereas with the chiral ZnEt2/R( − ) DMBD system, in the case of the polymerization of the (2RS,3S) monomer, the election was high and corresponded to a stereoelectivity ratio of r = 4, the highest one obtained up to now for oxiranes. The observed effects are due to the presence of a chiral centre in the side chain of the monomer.
Linear oligopeptides, 55. Infrared conformational analysis of polyethyleneglycol‐bound alanine and valine homo‐L‐oligopeptides in the solid state and in solution
Authors: Bonora Gian Maria , Palumbo Manlio , Toniolo Claudio , Mutter Manfred
Published: April 2003

The IR absorption properties of three series of monodisperse, chemically and optically pure, PEG‐bound linear homo‐oligopeptides having the general formula t‐Boc‐(L‐Ala‐)1–8Gly‐OPEG, t‐Boc‐(L‐Val‐)1–7Gly‐OPEG and t‐Boc‐(L‐Val‐)2–8Gly‐OPEG‐M were investigated in the solid state and in solution. In the latter case the study was extended to solvents of largely different polarity and different concentrations. In the solid state the Ala and Val peptides from n = 5 to n = 8 assume essentially a β‐structure. The occurrence of the unusual parallel‐chain β‐conformation was suggested for the N‐deblocked Val highest peptides. The conformational analysis in deuterochloroform at high dilution showed that a much higher content of intramolecularly H‐bonded forms exist in Ala4 than in the Val4 peptides. At higher concentrations chain length, solvent, and side chain effects are all operative in determining the extent of peptide association. The influence of the bi‐ and monofunctional polymeric supports on the conformational properties of the Ala and Val homo‐oligopeptide series is also discussed. Finally, preliminary results on the relationship between reactivity of the polymer‐bound growing peptide chain during the step‐by‐step synthesis and peptide conformation are reported.
Über die kinetik der vorkondensation von ethylenglykol mit linearen α,ω‐dicarbonsäuren in der schmelze
Authors: Ueberreiter Kurt , Hager Wilhelm
Published: April 2003

The kinetics of precondensation of ethylene glycol with the dicarboxylic acids: oxalic, malonic, succinic, glutaric, adipic, and pimelic acid was investigated.

The course of the reaction was followed by weighing the reaction water. The final rate equation was found to be of 6th order. This is explained by assuming that only free–OH and COOH groups are capable of the condensation reaction, their number being given by an association equilibrium. These effects are reflected by alternating numerical values of reaction enthalpies and entropies. The idea of an association is stressed by IR‐spectroscopic measurements.
Micelle formation by AB block copolymers of polystyrene and poly(dimethylsiloxane) in n‐alkanes
Authors: Dawkins John V. , Taylor Graham
Published: April 2003

AB block copolymers of polystyrene and poly(dimethylsiloxane) have been synthesized by “living” anionic polymerisation methods. The micellar behaviour of these block copolymers in n‐alkanes has been investigated as a function of the molecular weight of the polystyrene anchor A block and of the anchor/soluble balance (ASB) calculated from the relative block lengths. Micelle sizes have been determined by electron microscopy and are shown to conform to a simple geometrical model based upon two concentric spheres, when the ASB is below 18.
Eine oligomeranaloge friessche umlagerung oligomerer 2‐acetoxy‐1,3‐phenylenmethylene
Authors: Kämmerer Hermann , Evers Heinz , Böhmer Volker
Published: April 2003

α‐Hydro‐ω‐hydroxypoly(5‐chloro‐2‐hydroxy‐1,3‐phenylenemethylene)s (1a, b), the oligomeric condensation products from 4‐chloro‐2,6‐bis(hydroxymethyl)phenol and 4‐chlorophenol with hydrochloric acid in 1,4‐dioxane, could be completely dehalogenated at room temperature and atmospheric pressure with hydrogene/Raney‐Ni. The resulting oligomers 2a, b were esterified with acetic anhydride, and the esters 3a, b were subjected to a oligomer analogous Fries rearrangement to form the linear α‐hydro‐ω‐hydroxypoly(5‐acetyl‐2‐hydroxy‐1,3‐phenylenemethylene)s 4a and 4b. The characterization of the products was mainly done by spectroscopic methods.
Application of spin trapping technique to radical polymerization, 18. Initiation mechanism of vinyl polymerization with N,N‐dimethylaniline N‐oxide/acid anhydride systems
Authors: Sato Tsuneyuki , Kita Shinji , Otsu Takayuki
Published: April 2003

The mechanism of radical formation from the radical initiator systems N,N‐dimethylaniline N‐oxide (DMAO)/acid anhydride, was investigated by spin trapping technique. 2‐Methyl‐2‐nitrosopropane (BNO) was used as spin trapping reagent. In the DMAO/acetic anhydride system, both methyl and N‐methylanilinomethyl radicals were trapped by BNO as the corresponding amine N‐oxyl radicals. However, only ethyl and undecyl radicals were trapped from DMAO/propionic anhydride and from DMAO/lauric anhydride system, respectively. In the DMAO/benzoic anhydride system, the amine N‐oxyl radical derived from N‐methylanilinomethyl radical and another amine N‐oxyl radical were observed. The latter one is likely to be derived from a radical formed by hydrogen abstraction from the methyl group of DMAO by a benzoyloxyl radical. When the concentrations of DMAO and benzoic anhydride were lowered, phenyl radical was also trapped. From these findings, the initiation mechanism of vinyl polymerization with the DMAO/acid anhydride systems was proposed and discussed.
Thermodynamic studies on hemoglobin solutions
Authors: Nakajima Kuniyasu , Baba Yoshihiro , Kagemoto Akihiro , Fujishiro Ryoichi
Published: April 2003

The heat of solution and the osmotic pressure of bovin hemoglobin in aqueous solution have been measured at 298 K using a twin microcalorimeter and an osmometer. The heat of association, ΔH, from calorimetric measurement and the association equilibrium constant, K, from osmometric measurement have been estimated, respectively. Also the thermodynamic quantities of the hemoglobin molecule which associates from 2αβ to the original α2β2 form are calculated. In all systems of the hemoglobin solutions, the value of dissociation equilibrium constant, K', calculated as the reciprocal of K, and that of ΔH seem to be of comparable order to those determined by the other investigators.
Oxidation and chlorination of atactic polypropylene under γ‐irradiation
Authors: Omichi Hideki , Hagiwara Miyuki , Araki Kunio
Published: April 2003

Atactic polypropylene was irradiated in vacuo, in O2, and in Cl2 with 60Co γ‐rays, and changes in polymer structure were investigated by means of IR and ESR measurements of the irradiated polymer and by mass spectrometry of gaseous products. The irradiation in vacuo mainly produced H2 with small amounts of lower hydrocarbons (C1 – C3). As a radical product, only an alkyl radical was observed. The increase in IR absorption at 886 cm−1 indicated the formation of vinylidene unsaturation. The irradiation in O2 produced oxygenated products such as CO, CO2, and H2O with a reduced amount of H2. In the irradiation in Cl2, HCI was a main gaseous product. The existence of CCl bonds and a small amount of polyenyl groups in the irradiated polymer indicated that the radiation‐induced chlorination of APP was partly followed by elimination of HCl through a zip mechanism.
Linear oligopeptides, 60. Synthesis by the liquid‐phase method and characterization by amino acid analyses of two complete monodispersed homologous series derived from L‐alanine (to the octapeptide) and L‐valine (to the hexapeptide)
Authors: Bonora Gain Maria , Toniolo Claudio
Published: April 2003

The synthesis by the liquid‐phase method of the two complete, monodispersed homo‐oligopeptide series having the general formula t‐Boc\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}(\ {\rm L} - {\rm X}\rlap{---} )$\end{document}nGly‐OPEG (I:X=Ala, n=1‐8; II: X = Val, n = 1–6) is described. The chemical purity of the various products was assessed by thin layer chromatography and amino acid analyses. The influence of chain length and steric effects on the formation of peptide bonds and their stability to acid hydrolysis is also illustrated.
Formaldehyde polymers, 26. Syntheses and condensations of substituted triphenoxy and triphenyl derivatives of 1,3,5‐triazine
Authors: Ninagawa Akira , Kawazoe Masao , Matsuda Haruo
Published: April 2003

2,4,6‐Tris(4‐hydroxymethyl‐2,6‐dimethylphenoxy)‐1,3,5‐triazine (4a), 2,4,6‐tris(2,6‐dimethylphenoxy)‐1,3,5‐triazine (4b), and 2,4,6‐triphenoxy‐1,3,5‐triazine (4c) were synthesized by reactions of 2,4,6‐trichloro‐1,3,5‐triazine (3) with 4‐hydroxymethyl‐2,6‐dimethylphenol (2), 2,6‐dimethylphenol (1), and phenol, respectively, in the presence of metallic sodium or sodium hydroxide. 2,4,6‐Tris(4‐hydroxyphenyl)‐1,3,5‐triazine (4d) was prepared by trimerization of p‐cyanophenol. The condensation polymerization of 4a and cocondensations of 4a, with the other 1,3,5‐triazine derivatives or with novolak resin were carried out in the presence of p‐toluenesulfonic acid at 200°C. In the cocondensations of 4a with 4b, 4c, 4d, 2,4,6‐tris(2‐hydroxyphenyl)‐1,3,5‐triazine (4e) or with novolak resin, the reactivity of the comonomers was found to decrease in the order: novolak resin ≫4e≥4c>4b>4d. The disappearance of the absorption band belonging to the hydroxymethyl group as well as the appearance of the carbonyl absorptions could be observed in the IR spectrum of the condensation resins, however, only small intensities of carbonyl absorptions in the spectrum of the cocondensation product of 4a with novolak resin. The thermal decomposition of the resins was determined by thermogravimetry.
Syntheses of polyamides containing uracil and adenine
Authors: Hattori Masahira , Kinoshita Masayoshi
Published: April 2003

2‐(2,4‐Dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐yl)methylsuccinic acid (2a) and 2‐(6‐aminopurin‐9‐yl)methylsuccinic acid (2b) were synthesized through the addition reaction of uracil and adenine, respectively, to dimethyl methylenesuccinate, followed by hydrolysis of the resulting dimethyl esters. Dicarboxylic acid 2a was further converted to the corresponding di‐p‐nitrophenyl ester 3a and dicarboxylic acid 2b was converted to the di(cyanomethyl) ester 3b. The active esters 3a and 3b were polycondensed with diamines such as 1,2‐diaminoethane, 1,6‐diaminohexane, 4‐aminomethylbenzylamine, and piperazine in solution, giving polyamides containing uracil and adenine as the side group. The polyamides were found to have molecular weights in the range of about 1000–5000. The polyamides derived from 1,2‐diaminoethane and piperazine were soluble in water.
Synthetic polymers containing sugar residues, 2. Synthesis and properties of poly(urea‐urethane)s derived from D‐glucosamine and diisocyanates
Authors: Kurita Keisuke , Hirakawa Nobuhiko , Iwakura Yoshio
Published: April 2003

Poly(urea‐urethane)s containing D‐glucosamine residues in the main chain were prepared by direct addition polymerization of D‐glucosamine and diisocyanates. The polymerization reaction proceeded smoothly in N,N‐dimethylacetamide or hexamethylphosphoric triamide under certain conditions without blocking the excess hydroxy groups. The resulting poly(urea‐urethane)s were all soluble in polar solvents and had inherent viscosities of up to 1,27 dl·g−1. These polymers had D‐glucosamine residues with three pendant hydroxy groups in each unit, and they exhibited good reactivity toward acetylation and also very high water absorption.
Acrylonitrile copolymerization. Sequence distribution in acrylonitrile‐styrene copolymers by 13C NMR: Conversion and solvent effects
Authors: Pichot Christian , Pham Quang‐tho
Published: April 2003

Copolymers of acrylonitrile (A) and styrene (S) were synthetized in either N,N‐dimethylformamide (DMF) or toluene by free radical polymerization. Their sequence distribution was studied by 13C NMR at 25, 2 MHz. The observed sequence distributions follow first order Markov statistics and may be calculated using the set of reactivity ratios rA = 0,13 and rs = 0,36 (DMF) or 0,40 (toluene) provided the copolymers remain soluble during polymerization. The reactivity ratios were calculated graphically from the experimental triad distributions observed by 13C NMR using the method of Chiang et al. Deviations from first order Markov statistics were observed for heterogeneous polymerizations or for acrylonitrile rich initial monomer mixtures in DMF. No influence of steric hindrance on the cotacticity of the copolymer chain was noticed within the resolving power of our instrument.
Regiospecificity of titanium‐based catalyst system for propene polymerization
Authors: Doi Yoshiharu
Published: April 2003

The sequence distribution of inverted monomeric units in the stereoirregular polypropylenes, prepared with the TiCl4/Al(C2H5)3 catalyst system, has been examined by 13C NMR. Observed dyad and triad sequence distributions were in good agreement with those calculated from first‐order Markov statistics. The regioselectivity of an inserting propene seems to depend not only on the polarity of the active carbon‐titanium bond but also on the steric effects of the last propylene unit of a growing chain.
Synthesis of polyaminoquinones by vinylogous nucleophilic substitution polymerization of 2,5‐disubstituted p‐benzoquinones with diamines
Authors: Ueda Mitsuru , Sakai Naoyuki , Imai Yoshio
Published: April 2003

Vinylogous nucleophilic substitution polymerization of 2,5‐dihydroxy‐p‐benzoquinone and 2,5‐dimethoxy‐p‐benzoquinone with various diamines in m‐cresol afforded polyaminoquinones with inherent viscosities as high as 0,5 dl.g−1 in quantitative yields. The polyaminoquinones, except for the polymer derived from 1,3‐bis(aminomethyl)benzene, were partially soluble or practically insoluble in organic solvents, but were solubilized by alkaline hydrosulfite reduction. Thermal analyses showed an initial weight loss at around 200°C in both air and nitrogen atmospheres, followed by gradual decomposition.
Thermal decomposition of flame retardant acrylonitrile copolymers investigated by direct pyrolysis in the mass spectrometer
Authors: Ballistreri A. , Foti S. , Montaudo G. , Pappalardo S. , Scamporrino E. , Arnesano A. , Calgari S.
Published: April 2003

The thermal behaviour of copolymers of acrylonitrile containing vinylidene chloride (VC2), 1‐bromo‐1‐chloroethylene (VCB), vinyl bromide (VB) units and Sb2O3, was investigated by gradually increasing the temperature of a polymer sample placed in the ion source of a mass spectrometer (MS). The resulting pyrolytic processes (time‐temperature resolved) were analyzed by detecting the volatile decomposition products formed. Sb‐halogenated species were detected in the mass spectra of the thermal decomposition products of the copolymers, and their presence is interpreted as the result of antimony‐halogen hydracids interactions during the pyrolysis.
Photochemical reactions in commercial poly(oxy(2,6‐dimethyl)‐1,4‐phenylene)
Authors: Allen Norman S. , McKellar John F.
Published: April 2003

The photooxidation of commercial poly(oxy(2,6‐dimethyl)‐1,4‐phenylene) (PPO) has been examined using absorption, luminescence (fluorescence and phosphorescence) and flash photolysis techniques. A comparison of the luminescence spectra of the polymer with that of the monomer 2,6‐dimethylphenol (DMP) shows that the chromophoric species responsible for light absorption in the near ultraviolet region 290–350 nm is the unit structure of the polymer itself. The fluorescence results also show the presence of an impurity chromophore in the polymer that absorbs in the visible region 400–550 nm. The flash photolysis experiments on both PPO and DMP give direct evidence for the formation of a phenoxyl radical indicating that main chain scission at the ether linkage is a major primary process in the photodeterioration of the polymer.
Polyelectrolyte complexes, 1. The effect of pH and ionic strength on the stoichiometry of model polycation—polyanion complexes
Authors: Cundall R. B. , Lawton J. B. , Murray D. , Phillips G. O.
Published: April 2003

The interactions between model polycations and polyanions have been studied using the fluorescent dye acridine orange as a probe. The dye emission at 540 nm is quenched by the addition of polyanions, a process which is reversed by the addition of certain polycations. Techniques have been developed which enable a determination of the stoichiometry of polyelectrolyte complexes so formed between three polyanions {carboxymethylcellulose, κ‐carrageenan and poly(styrenesulfonate)} and two polycations {poly(L‐lysine hydrobromide) and poly(p‐xylylviologen dibromide)}. A one to one pairing of acidic sites with basic groups was observed over a wide range of temperature, pH and ionic strength. Deviations from unit stoichiometry in the presence of multi‐charged metal ions have been interpreted as due to conformational changes in the polyanion. Results from viscosity measurements are included which suggest the neutralisation of charged groups in the polyelectrolyte complex.
Mechanical stabilization of molecular conformation by entrapping in a polymer matrix
Authors: Belokon' Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Vitt Sergei V. , Bakhmutov Vladimir I. , Belikov Vasili M.
Published: April 2003

5‐Methacryloyl‐ and 5‐isobutyrylaminosalicylaldehydes (5a and 5b, respectively) and diastereomeric complexes of their Schiff bases with amino acids and Co(III): potassium Λ‐ and Δ‐bis‐[N‐5‐methacryloylaminosalicylidene‐(S)‐valinato]cobaltate(III) (6a, b), potassium Λ‐ and Δ‐bis[N‐5‐isobutyrylaminosalicylidene‐(S)‐norvalinato]cobaltate(III) (7a, b), potassium Λ‐ and Δ‐bis[N‐5‐methacryloylaminosalicylidene‐(S)‐norvalinato]cobaltate(III) (8a, b), have been synthesized. Copolymerization of 6–7a, b with acrylamide and N,N′‐methylenebis(acrylamide) leads to the formation of transparent hydrophilic gels in which the amino acid fragments preserve their ability of exchanging α‐hydrogen for deuterium in an alkaline medium. Comparison of the behaviour of polymer complexes ℗‐7a and ℗‐7b in the process of base‐catalyzed epimerization with their monomer analogues 8a and 8b shows that their stereoselectivity substantially changes when one goes from 8a to ℗‐7a. Such an effect may be explained by stabilization of the initial conformation of the complex molecule by the polymer matrix formed around the complex acting as a template.
Photoinitiation, 6. Copolymerization of styrene with maleic anhydride photoinitiated by the excited charge‐transfer complex styrene‐maleic anhydride
Authors: Bartoň Jaroslav , Capek Ignác , Arnold Manfred , Rätzsch Manfred
Published: April 2003

The kinetics of styrene (St) copolymerization with maleic anhydride (MA) initiated by light (at λ = 365 nm) was studied in acetone, acetonitrile, chloroform, and N,N‐dimethyl formamide at 30°C. With the exception of the chloroform containing system, the copolymerizations took place in homogeneous reaction media. The copolymerization rate Rp = −d([St] + [MA])/dt was found to be a function of the mole ratio of the comonomers in the reaction mixture. For a given ratio of comonomers Rp and the molecular weight of the resulting copolymer were found to be a function of the donor number of the solvent used for a given rate of initiation. Due to the dependence of Rp on the concentration of an equimolar mixture of both comonomers in acetone on [St] (at constant [MA]), and on [MA] (at constant [St]) the participation of the exciplex {St…acetone}* in the initiation reaction can be expected. The ratio of the overall rate constants for the propagation (k̄p) and termination (k̄t) reactions, k̄p/2k̄t, determined by a rotating sector technique, was found to depend on the composition of the comonomer mixture. The copolymerization rate is proportional to the square root of the intensity of incident light, which, together with the observed inhibition effect of oxygen points to a radical mechanism of the photoinitiated copolymerization of St with MA. In the presence of the photosensitizer benzophenone in the system St/MA/acetone an increase in Rp was observed, accompanied by a decrease in molecular weight of the copolymer in comparison with the system without benzophenone.
Pharmakologisch‐aktive polymere, 21. Orientierende Untersuchungen zur körperverteilung und Ausscheidung von poly[2‐(methylsulfinyl)ethylacrylat]en bei der Ratte
Authors: Hofmann Volker , Ringsdorf Helmut , Schaumlöffel Erich
Published: April 2003

Poly[2‐(methylsulfinyl)ethyl acrylate] (1) was synthesized as well as derivatives 14C‐labelled in side groups (6) or 14C‐labelled in the main chain (11). Polymer 11 with the 14C‐labelled main chain was fractionated by precipitation. The η‐M‐relation determined by measurements of unlabelled polymers in the ultracentrifuge for comparison was used to establish the viscosimetrically determined molecular weights of the labelled fractions. After intravenous application of aqueous solutions of the polymer in rats the excretion rate up to 72 h after treatment was ascertained to ca. 50%; the concentration in the blood serum was found to be strikingly high. A tendency to reinforced storage in organs of high phagocytose activity by growing molecular weight was observed. The tumor affinity was — if at all — low.
Polymere 2,2,6,6,‐Tetraalkylpiperidin‐Derivate, 1. Tetra‐ und Pentaalkylpiperidin‐Derivate von Polyacryl‐ und Polymethacrylestern, Polyacryl‐ und Polymethacrylamiden
Authors: Karrer Friedrich E.
Published: April 2003

A number of tetra‐ and pentaalkylpiperidine derivatives of acrylic and methacrylic acid was synthesized, polymerized, and copolymerized with several comonomers as potential UV stabilizers. In addition, by oxidation of some of these polymers and of a copolymer with peroxy compounds, polymers were obtained containing pendant nitroxyl groups. The properties of these polymers with free radical groups are discussed in relation to their spectral data.
Optically active vinyl polymers, 22. Relationship between intrinsic viscosity and molecular weight for poly‐(S)‐4‐methyl‐1‐hexene and related polymers
Authors: Neuenschwander P. , Pino P.
Published: April 2003

Isotactic poly‐(S)‐4‐methyl‐1‐hexene (PS4MH), poly‐(R,S)‐4‐methyl‐1‐hexene (PRS4MH) and poly‐4‐methyl‐1‐pentene (P4MP) were fractionated according to stereoregularity and molecular weight. The fractions obtained were characterized and the constants aη and K of the Mark‐Houwink equation calculated for thermodynamically good solvents at low temperatures and for theta solvents at high temperatures.
Properties of polyethylene‐polypropylene blends: Crystallization behavior
Authors: Martuscelli Ezio , Pracella Mariano , Avella Maurizio , Greco Roberto , Ragosta Giuseppe
Published: April 2003

The crystallization behavior of high density polyethylene/isotactic polypropylene blends (HDPE/PP) was investigated. The overall kinetics of crystallization of HDPE may be strongly influenced by the addition of a small fraction of PP. At 398 K the half crystallization time of the blend containing 10% by weight of PP is around three times larger than for pure polyethylene. This effect may be accounted for by an increase in the melt viscosity of liquid HDPE caused by PP molecules. For crystallization temperatures high enough to prevent HDPE crystallization (Tc > 400 K), the presence in the melted blends of liquid HDPE influences the crystallization of PP. In fact, the half time of crystallization of PP increases with increasing the fraction of HDPE in the blend. The kinetics show a minimum at a well defined composition (around 60% in PP) before phase inversion. The same trend is observed when the surface free energy of folding and the lamellar thickness of crystals are reported as function of composition.
Two‐Stage nature of crystallization in stretched cis‐1,4‐polybutadiene networks
Authors: Cesari Marco , Perego Giovanni , Zazzetta Alessandro , Gargani Luciano
Published: April 2003

The crystallization of cross‐linked cis‐1,4‐polybutadiene, stretched at room temperature, is investigated by wide and small angle X‐ray diffraction techniques, at temperatures ranging from −40°C to the melting point, Tm, and for extension ratios, λ, from 1 to 7,7. The experimental conditions adopted should approximate thermodynamic equilibrium. All the experimental findings, namely, crystallinity, preferred orientation of the crystalline and amorphous fractions, unit‐cell dimensions and others, are consistent with the formation of two types of crystals: one depending mainly on stretching, the other on temperature. The former is characterized by extended chain crystals with Tm higher than the isotropic melting point (T = −3°C); the latter by a lamellar (bulk‐like) morphology which is stable only below T. A slight increase of Tm occurs for λ < 3, when the axes of the crystallized chains are tilted with respect to the strain direction; only when untilted crystals are formed (λ > 3) a remarkable increase of Tm is observed as a function of λ. As a qualitative interpretation, the two‐fold crystallization mechanism is based on non‐uniform extensibility of the segments included between adjacent junctions of the network.
Solvent effect on the complex formation of poly(methacrylic acid) with proton‐accepting polymers
Authors: Ohno Hiroyuki , Nii Atsushi , Tsuchida Eishun
Published: April 2003

A pair of polymers may interact with each other through hydrogen bond and form a polymer complex. Such polymer complex formation is affected by several chemical and physical factors, especially by solvent properties. This solvent effect was studied in the complex formation of poly(methacrylic acid) with a series of proton‐accepting polymers in aprotic solvents. The extraordinary behaviour of polymer complexes in dimethyl sulfoxide was well explained in terms of the strong interaction between proton‐donating polymer and dimethyl sulfoxide. In addition, a stronger proton‐accepting polymer, viz. poly(N,N‐dimethyl‐N′,N′,N″,N″‐tetramethylenephosphoramide), was synthesized. This polymer could form a polymer complex with poly(methacrylic acid) through hydrogen bond even in dimethyl sulfoxide. Selective polymer complex formation was achieved by controlling such solvent properties.
Biomedical behavior of synthetic polyion complexes toward blood platelets
Authors: Kataoka Kazunori , Tsuruta Teiji , Akaike Toshihiro , Sakurai Yasuhisa
Published: April 2003

A group of polyion complexes (PICs) was checked as candidate for non‐thrombogenic biomaterials. To evaluate blood‐compatibility of different types of PIC, the interaction of the PICs with blood platelets was examined by passing fresh blood through a column packed with glass beads which were precoated with PIC. The course of morphological change of the platelets adhered on the surface was observed by scanning electron microscopy. The behavior (adhesion, aggregation, and deformation) of the platelets on the beads' surface was found to be significantly influenced by the mole ratio of polyanion to polycation in the PIC. The blood‐compatibility could be shown to depend also on the chemical structure of the polycation component of the PIC. Among the PICs examined, the newly synthesized PIC 5 showed the best results in terms of the number of adherent platelets and the degree of their deformation. The good blood‐compatibility of 5 is presumabley attributable to the easiness in getting to stoichiometric neutralization.