bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure of poly[polytetrahydrofuran‐block‐poly(sebacoylchloride‐alt‐hexamethylenediamine)] and its role in blood compatibility
Authors: Yui Nobuhiko , Kataoka Kazunori , Sakurai Yasuhisa , Keitoku Fumio , Sanui Kohei , Ogata Naoya
Published: April 2003

The microstructure of poly[polytetrahydrofuran‐block‐poly(sebacoyl chloride‐alt‐hexamethylenediamine)]s 1–4, containing polytetrahydrofuran (PTHF) blocks of various molecular weights, and their blood compatibility were studied. These multiblock copolymers were prepared by interfacial polycondensation. The characterization of these copolymers was carried out by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical measurements, wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and electron spectroscopy for chemical analysis (ESCA). The TEM observation revealed the formation of a spherulitic structure at the copolymer surfaces, which is closely related to the homopolymer, polyamide (PA) 610. The DSC and dynamic mechanical measurements indicate the presence of distinct phase separation between PTHF and PA 610 blocks, and of the PTHF block in the copolymer being partially crystallized. The WAXD and SAXS indicate the formation of microstructures composed of crystalline and amorphous phases in the copolymer. Moreover, ESCA measurements verify that the surface chemical composition of the copolymer is identical to their bulk composition. Blood compatibility of these copolymers was evaluated by estimating platelet adhesion on the copolymer surfaces. Platelet adhesion was found to be affected by the PA 610 crystallinity, including the size and distribution of the crystalline phase in the case of the copolymers in which the PTHF blocks are completely amorphous (M̄n = 980). On the contrary, platelet adhesion at the copolymers in which the PTHF blocks are partially crystallized (M̄n ≥ 1560) depends upon the crystallinity of both PA 610 and PTHF, including the balance of crystalline (PA 610 and PTHF) and amorphous (mainly PTHF) phases. This result suggests that the balance of the crystalline and amorphous phase distribution in the copolymer is the most determinative factor for suppressing platelet adhesion at the copolymer surface.
Synthesis of liquid crystalline polyacrylates and their use in capillary gas chromatography
Authors: Naikwadi Krishnat P. , Jadhav Anita L. , Rokushika Souji , Hatano Hiroyuki , Ohshima Mitsuyosi
Published: April 2003

New enantiotropic liquid crystalline compounds based on 4‐(p‐substituted phenylazo)phenol and m‐cresol esters containing an acryloyloxy group were synthesized. Polyacrylates were prepared from these monomers by radical polymerization. The resulting polymers exhibit nematic enantioropic properties. The polyacrylates have broader nematic ranges and higher nematic to isotropic transition temperatures as compared to their corresponding monomers. The nematic range is dependent on both the lateral substituents and the terminal substituents. The laterally substituted polyacrylates gave a narrower nematic range than unsubstituted compounds. Increase in carbon number in the terminal alkyl group leads to a broader nematic range. The liquid crystalline polyacrylates could be coated uniformly on the inside of a glass capillary tubing. The coated capillary columns show an excellent selectivity in gas chromatography for the separation of isomeric compounds. The liquid crystalline stationary phases are highly stable up to 230°C without column bleeding.
Relationship between physical parameters of the solvent and its influence in stereocomplex formation
Authors: Katime Issa A. , Quintana Jose Ramon , Strazielle Claude
Published: April 2003

An extensive study on the influence of the solvent on the PMMA stereocomplex formation was made by means of laser light scattering and viscometry for the following solvents: nitroethane, cyclohexanone, aniline, 1,1,2,2‐tetrachloroethane, ethyl benzoate, 1,2‐dimethoxyethane, N,N‐dimethylacetamide, ethyl and propyl acetate, ethyl methyl and isobutyl methyl ketone, 1,2‐dichloroethane, 1,4‐dioxane, DMF, bromoform, chloroform, chlorobenzene, 1,2‐dichlorobenzene, 1,3‐dichlorobenzene, 1,1,1‐trichloroethane, and trans‐1,2‐dichloroethane. It was found that a variation in the polymer tacticity causes a change in the influence of the solvents on stereocomplex formation, e.g. in the case of chlorobenzene, 1,2‐dichlorobenzene and nitrobenzene. Further, the influence of the solvent was related with the non‐polar, polar and hydrogen bonding components of the solubility parameter, δd, δp and δh.
Study of the compatibility of poly(ethylene oxide) with polyitaconates
Authors: Quintana José R. , Radic Deodato , Cesteros Luis C. , Katime Issa A.
Published: April 2003

This paper reports on the compatibility of poly(ethylene oxide) (PEO) towards poly(monobenzyl itaconate) (PMBzl) and poly(dibenzyl itaconate) (PDBzl) in the bulk by analyzing the melting point depression of the crystalline component and the influence of the amorphous material on the crystallization kinetics of the former. The experimental data obtained suggest compatibility for the PEO/PMBzl blend and incompatibility for the PEO/PDBzl system. This behaviour is explained by specific interactions (hydrogen bonds) between the chains, and is compared with that of other polymers with similar chemical structure.
Lösungsmittel‐effekt bei der bildung von \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} (\mathop {\rm C}\limits^{\rm |} \hbox{=} \mathop {\rm C}\limits^{\rm |} \rlap{--} )_{\rm n}$\end{document} doppelbindungssequenzen in polystyrol bei bestrahlung mit langwelligem uv‐licht
Authors: Turzyński Zbigniew , Woliński Leszek
Published: April 2003

Upon irradiation with long‐wave range UV light of degassed chlorine‐containing solutions of polystyrene conjugated double bonds \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} (\mathop {\rm C}\limits^{\rm |} \hbox{=} \mathop {\rm C}\limits^{\rm |} \rlap{--} )_{\rm n}$\end{document} are formed along the polystyrene chain. The kinetics of their formation and their sequence lengths depend on the solvent. Aside from isolated CC double bonds sequences of \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} (\mathop {\rm C}\limits^{\rm |} \hbox{=} \mathop {\rm C}\limits^{\rm |} \rlap{--} )_{\rm n}$\end{document} with n = 2 to n = 5 are formed.
Morphological study of melt‐crystallized linear low‐density polyethylene by transmission electron microscopy
Authors: Hosoda Satoru , Kojima Keitaro , Furuta Motonobu
Published: April 2003

The morphology of the lamellae in non‐isothermally crystallized linear low‐density polyethylene (LLDPE), conventional high‐pressure low‐density polyethylene (HP‐LDPE), and a high‐density polyethylene (HDPE) sample was investigated by transmission electron microscopy (TEM). LLDPE exhibits clearly two different types of lamellae, i.e., thick, long, and straight lamellae like those of HDPE, and thin, short, and curved lamellae which grow among the former ones. Also LLDPE shows the broadest distribution of the values for the lamella thickness among the three types of polyethylenes mentioned. The average lamella thickness decreases in the order HDPE > LLDPE > HP‐LDPE. Fractions were used to study the effects of the kind and the degree of short chain branching (SCB) and of the molecular weight in the range from 4100 to 3,1·105. SCB has a predominant influence on the lamella thickness as well as on the shape, while the molecular weight does not largely affect lamella thickness but affects the shape of the lamellae. Further it was revealed from TEM observation that the isobutyl branch decreases lamella thickness more effectively than does the ethyl branch. This is in accordance with results from small‐angle X‐ray and differential scanning calorimetry measurements.
Analyse du photoviellissement des materiaux polymères par évolution de la perméabilité aux gaz
Authors: Philippart Jean‐Louis , Gardette Jean‐Luc
Published: April 2003

The variations of diffusion constants and permeability for carbon dioxide, oxygen and nitrogen in poly(ether‐block‐amide)s were measured during the photooxidation of the polymer. The determination of these constants appears to be a sensitive criteria to characterize the photooxidative evolution of polymers. The decrease of the diffusion constant, observed in the course of photooxidation, is interpreted by the formation of chemical crosslinks and by the existence of physical interactions between primary hydroperoxidic photoproducts. Several treatments were developed which modify the nature of these oxidized groups; the evolution of diffusion constants is related to the modification of the interactions between these groups.
Cinétiques de télomérisation, 7. Calcul de k/kTe en polymérisation radicalaire de divers monomères
Authors: Boutevin Bernard , Piétrasanta Yves
Published: April 2003

In contrast to the usual method of determination of the principle ratio in radical polymerization, k/kTe, which is based on the comparison of the rate of polymerization with the concentration of initiator, a method was used consisting in the representation of loge([M]0/[M]) versus (1 − e−kdt/2). The results obtained with styrene, vinyl acetate, acrylic acid, methacrylic acid, and 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate (1) were found to be in good agreement with those already obtained by the other method.
Structural analysis of alkene/maleic anhydride copolymers
Authors: Rätzsch Manfred , Zschoche Stefan , Steinert Volker , Schlothauer Klaus
Published: April 2003

Structural investigations on maleic anhydride (MAn) copolymers with ethene, propene and styrene, their products of hydrolysis, and their methyl half‐esters by means of 13C NMR spectroscopy are presented. The spectra of 2,3‐diethylsuccinic acid and its anhydrides in the erythro‐ and threo‐configuration and of butylsuccinic acid and its anhydride were obtained and compared with the spectra of the copolymers. In each case the results show the formation of both threo(trans)‐ and erythro(cis)‐structures. At a polymerization temperature of 60°C the proportions were 88% threo to 12% erythro for ethene/MAn copolymers and 80% threo to 20% erythro for propene/MAn copolymers, a ratio which was confirmed also by the hydrolyzed forms. Copolymerization at 150°C leads, in the case of propene/MAn, to 67% threo and 33% erythro. The production of ethene/MA copolymer via the copolymerization of ethene and fumaric acid half‐ester and its saponification to ethene/fumaric acid leads to a ratio of 38% threo to 62% erythro. These results are in accordance with the thermal stabilities of the configurations. In the case of styrene/MAn copolymer it is not possible to obtain a unique interpretation of the configurations from the spectra. For the conversion of propene/MAn and styrene/MAn copolymers by means of methanol to half‐esters it can be derived from the 13C NMR spectra how many of the half‐ester moieties are obtained in the neighbourhood of the methyl and phenyl groups, respectively, of the olefin.
Solution and membrane properties of zwitterionic polymers
Authors: Itoh Yoshihiro , Abe Koji , Senoh Saburo
Published: April 2003

The aqueous solution properties of poly(4‐vinylpyridinium sulfopropylbetaine) (PVPyPS, systematic name: poly{1‐[1‐(3‐sulfonatopropyl)pyridinium‐4‐yl]ethylene} (1)) and poly(3‐methacryloylethoxycarbonylpyridinium sulfopropylbetaine) (PMAPS, systematic name: poly{1‐methyl‐1‐[2‐[1‐(3‐sulfonatopropyl)pyridinium‐3‐ylcarbonyloxy]ethoxycarbonyl]ethylene} (2)) are investigated. Polymers 1 and 2 are soluble only in salt solutions and their intrinsic viscosity increases with increasing salt concentration, this being a common property of poly(sulfobetaine)s. Hydrogel membranes containing PVPyPS are opaque in pure water but become transparent in salt solution.
Kinetics of the free radical copolymerization of diethyl maleate with styrene
Authors: Braun Dietrich , Cei Gustavo
Published: April 2003

The free radical copolymerization of diethyl maleate (M1) with styrene (M3) was studied in bulk at 60°C with azoisobutyronitrile as initiator. In order to compute the reactivity ratios, we determined the copolymer composition by microanalysis of the carbon content. The evaluation of the data was carried out according to two procedures; the Kelen‐Tüdös linearization method and the non‐linear least‐squares of Tidwell and Mortimer. The ratios obtained with the latter, r13 = 0,001 and r31 = 6,592, yielded a better fit. Different kinetic models were tested to describe the observed dependence of reaction rate on monomer mixture composition. The experimental results could be successfully described according to a kinetic model that assumes diffusion control of the termination reaction. The resulting kinetic equation contains two parameters whose values were determined from the experimental copolymerization rates. The value of one of these parameters could be obtained also from homopolymerization data for styrene. This proves that the parameters have physical significance and are not arbitrary quantities chosen to fit the experimental results.
Calculation of the integral chemical distribution of block copolymers
Authors: Pallaske Ulrich , Kuhn Rainer
Published: April 2003

Calculations show for an anionic block copolymerization under ideal conditions that the integral chemical distribution of a block copolymer (with given number‐average molar mass and average chemical composition) should be independent of the number of blocks in the copolymer and thus independent of the way in which the monomers are added during polymerization. Calculations for block copolymers consisting of styrene and butadiene are given to illustrate the decrease of the width of the chemical distribution with increasing molar mass. The chemical distributions of styrene‐butadiene block copolymers determined experimentally by successive fractional demixing with demixing solvents are consistently broader than the calculated ones. This must be attributed to association equilibria of the initiator and of the living polymer chains and also to termination reactions of the polymer chains. The theoretically expected narrow chemical distributions can be obtained approximately by head and tail fractional demixing of the copolymers with demixing solvents.
Reactivity of N‐alkylated cyclic iminoether salts having vinyl groups, 2. Polymerization and copolymerization of 2‐isopropenyl‐3‐methyl‐2‐oxazolinium salts
Authors: Miyamoto Masatoshi , Sano Yoshiyuki , Kimura Yoshiharu , Saegusa Takeo
Published: April 2003

3‐Methyl‐2‐isopropenyl‐2‐oxazolinium salts (4a, b) were prepared by alkylation of 2‐isopropenyl‐2‐oxazoline (2). Their preparation is much easier than that of their vinyl analogues, 3‐methyl‐2‐vinyl‐2‐oxazolinium salts, which cannot be isolated due to their high tendency to polymerization. 4a, however, was found, to show a low tendency toward radical and anionic polymerization, but it can be smoothly radically copolymerized with some vinyl monomers. The copolymerization parameters of 4a were determined and discussed in comparison with those of 2.
Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution
Authors: Koch Horst , Laschewsky André , Ringsdorf Helmut , Teng Kang
Published: April 2003

Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid‐like compounds with photoreactive units undergo self‐organization to form monolayers at the gas‐water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single‐chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single‐chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
Some spectral and thermal contributions to the curing of new epoxy compounds with aromatic diamines
Authors: Serra Angels , Cádiz Virginia , Martínez Pedro‐Alberto , Mantecón Ana
Published: April 2003

The curing reaction of the new bis(2,3‐epoxypropyl) 4,4′‐carbonyldi‐ω‐phthalimidoalkanoates 1a–c was studied with several aromatic diamines 2a–c as curing agents. The process was followed by means of spectrophotometric techniques. The influence of the nature of the curing agent on the reaction rate was examined. The adduct formation yielding first chain extension, is the first step of the reaction, followed by crosslinking, once the gel point has been reached. The products obtained were found to be rather thermostable.
Composition‐properties relationships in propene‐ethene random copolymers obtained with high‐yield Ziegler‐Natta supported catalysts
Authors: Avella Maurizio , Martuscelli Ezio , Volpe Gaetano Della , Segre Annalaura , Rossi Enrico , Simonazzi Tonino
Published: April 2003

The crystallization and thermal behaviour of crystallizable random propene/ethene copolymers (P‐co‐E) was systematically investigated. Index of crystallinity and, index of γ‐form, enthalpy and entropy of fusion, equilibrium melting temperature, spherulite growth rate, and overall kinetic rate constant were determined and correlated with the overall ethene content and with the concentration of specific chemical defects as determined by 13C NMR analysis (PEP, EPP, EPE triads). The samples of the copolymers, obtained with very‐high‐yield Ziegler‐Natta catalysts, were characterized by IR, 13C NMR, wide angle X‐ray scattering, and differential scanning calorimetry.
Synthesis and thermodynamic studies of two new polymers carrying amido and amino groups in the side chains
Authors: Barbucci Rolando , Casolaro Mario , Nocentini Mila , Reginato Gianna , Ferruti Paolo
Published: April 2003

Two linear vinyl polymers carrying amido and primary amino groups in the side chains were synthesized and characterized. Their behaviour in aqueous solution was investigated by potentiometric, viscometric and calorimetric techniques. In both cases, the basicity constants show a linear dependence on the degree of protonation α, while the enthalpy values of protonation do not. The thermodynamic results demonstrate the important role of hydrophobic interactions on the protonation process.
Hydroxytelechelic polybutadiene, 9. Kinetics of reactions in solution and in bulk between radically obtained hydroxytelechelic polybutadiene and propyl and phenyl isocyanate studied by 1H NMR
Authors: Descheres Isabelle , Pham Quang Tho
Published: April 2003

The kinetics of the reactions of radically obtained hydroxytelechelic polybutadiene (Arco R45M) with propyl isocyanate and phenyl isocyanate were studied by 1H NMR at high field. The reactivities of the three alcohol functions of Arco R45M were found to be different. The three individual reactions follow a 3rd order law and are accelerated by autocatalysis. There is competition between (OH, OH) auto‐association and (free OH + isocyanate) reactions. As a consequence, rate constants are strongly affected by (OH, OH) association phenomena.
Structure of 2,2,5,5,6,6,9,9‐octamethyl‐2,5,6,9‐tetrasiladecane, a structural precursor of poly[(tetramethyldisilanediyl)ethylene]
Authors: Ovchinnikov Yuri E. , Shklover Valeri E. , Struchkov Yuri T. , Polyakov Yuri P. , Gusel'nikov Leonid E.
Published: April 2003

In order to obtain information for suggesting the most likely molecular and crystal structure of poly[(tetramethyldisilanediyl)ethylene] (PTMDSE) an X‐ray study of the structural precursor 2,2,5,5,6,6,9,9‐octamethyl‐2,5,6,9‐tetrasiladecane (TSD) is carried out. The TDS molecule is centrosymmetric, the CSiCCSiSiCCSiC chain having an almost planar all‐trans conformation. In the crystal of TSD one can distinguish molecular layers parallel to the a b plane; the long axes of the TSD molecules form an angle of 24,4° with the layer plane; intermolecular contacts in layers are shorter, on the average, than interlayer contacts.
Polymeric prodrugs, 5. Dextran‐bound antirheumatic agent naproxen
Authors: Azori Mária , Pató János , Csákvári Éva , Tüdős Ferenc
Published: April 2003

The dextran‐bound antirheumatic agent, Naproxen [(+)‐2‐(6‐methoxy‐2‐naphtyl)propionic acid] (3) was synthesized by linking the 2‐aminoethyl ester of Naproxen to the oxydized dextran via an alkylamine bond. The hydrolytic stabilities of modified dextrans were examined viscometrically. The drug release from polymeric prodrug samples containing 68–172 mg of Naproxen per g product was followed at 37°C by automatic titration at pH 8,4. The first order kinetic constant of hydrolysis, k1, was determined to be 2,46(±0,4) · 10−6 s−1. Acute toxicity tests showed no toxic effect on CFLP mice administered intraperitoneally 300 mg/kg of dextran‐bound Naproxen.
Polymeric schiff's base chelates and their precursors, 9. Synthesis of covalently and coordinatively bound polymeric chelates and their dioxygen binding in the solid state
Authors: Wöhrle Dieter , Bohlen Heike , Blum Johannes K.
Published: April 2003

Covalently bound polymeric cobalt chelates 5 of Co(salen) type were synthesized by copolymerization of 2‐hydroxy‐5‐vinylbenzaldehyde (2) with 4‐vinylpyridine and subsequent polymeranalogous reactions. Coordinatively bound polymeric chelates 6 were obtained from Co(salen) and poly(4‐vinylpyridine) or its copolymer with styrene. Dioxygen binding studies (volumetric measurements and ESR spectroscopy) revealed that mononuclear superoxo complexes are formed reversibly.
On the rate and activation parameters for the primary decomposition of a quaternary ammonium persulfate in moderately polar organic solvents
Authors: Ghosh N. N. , Gupta G. N. , Mandal B. M.
Published: April 2003

The activation energy for the primary decomposition of ionpaired trioctylmethylammonium persulfate in moderately polar organic solvents was found to be about one half the value for the persulfate ion decomposition in aqueous alkaline media. However, its effect on the primary decompostion rate of the former is largely offset by the lowered entropy of activation, which adopts a negative value. The results indicate that the activated state is more ionic than the ground state. A tentative structure of the activated state which involves an intra‐ionic triple ion is proposed to account for the observed results.
Thermally stable sulfonic acid resins
Authors: Brouwer Dirk M. , van de Vondervoort Elizabeth M.
Published: April 2003

Polystyrene‐divinylbenzene resins 2 and 3 containing carboxysulfoalkyl groups were prepared by Michael addition of phenyl ethylenesulfonate to the reaction products of the chloromethylated resins with cyanide and diethyl malonate, respectively. They display an unusually high thermal stability in water: less than 5–10% loss of SO3H after 100 hat 200°C. Their catalytic activities (hydrolysis of sucrose), expressed per equivalent of SO3H, are twice as high as those of corresponding ring‐sulfonated resins.
Different chromotropic behaviour of DNA and RNA and of poly(adenylic acid) and poly(uridylic acid) with the dye pinacyanol chloride
Authors: Pal Medini Kanta , Ghosh Bijan Kumar
Published: April 2003

The cyanine dye pinacyanol chloride (PCYN) distinguishes various polyanions by exhibiting two distinct types of absorption spectra of the dye‐polyanion system. This dye can also differentiate between the biopolymers DNA and RNA, as well as between poly(adenylic acid) (poly‐A) and poly(uridylic acid) (poly‐U). The dye‐RNA spectra are independent of polymer/dye (P / D) ratio and show a sharp peak at 490 nm and a very broad band around 560 nm indicating not well organized aggregation of dye cations bound to the polymer. The spectra of the dye‐DNA system are similar only at low P / D, but with increase in DNA concentration a sharp band appears at 560 nm with disappearance of the peak at 490 nm. The poly‐U/PCYN system resembles the RNA‐PCYN system and the poly‐A/PCYN system resembles the DNA‐PCYN system. These differences are interpreted to arise from the preferential binding of the dye to purine bases rather than to pyrimidine bases, and from the partial intercalation of the dye within the DNA helix at high P / D. The sharp band at 560 nm of DNA‐PCYN at high P / D is due to dimerization of PCYN — the major, if not the only, state of aggregation of the dye induced by DNA at high P / D.
Divalent cation‐induced permeability regulation of polymer membrane with permeating pathway of a synthetic polypeptide
Authors: Maeda Mizuo , Aoyama Masato , Inoue Shohei
Published: April 2003

Regulation of solute permeability induced by divalent cations was performed in a polymer membrane with transmembrane permeating pathway (“channel”) of a synthetic polypeptide. The membrane material was a poly(butyl methacrylate) (backbone)/poly(L‐glutamic acid) (branch) graft copolymer. Permeability of phenyl‐1,2‐ethanediol was remarkably reduced in the presence of divalent cations such as Ca2+ and recovered by addition of ethylenediaminetetraacetic acid (EDTA). Infrared spectra of the membrane demonstrated a reversible change of the structure of pathway‐composing polypeptide chains induced alternationgly by Ca2+ and EDTA.
Ziegler‐Natta polymerization of propene: Cooperative effects of titanium ligands on the steric control of the first addition of monomer
Authors: Tritto Incoronata , Sacchi Maria Carmela , Locatelli Paolo
Published: April 2003

A 13C NMR analysis of the methyl and ethyl end‐groups in isotactic polypropylene, prepared in the presence of TiCl3‐ and Til3‐based catalysts, was performed and the isotactic regularity of the first propylene unit added to the Ti—alkyl bond was measured. In the presence of the catalyst Til3/Al(13CH2CH3)3 the stereoregulating effects derived from the ethyl and iodine ligands are cooperative, so that the addition of the first monomeric unit is as isotactic as the following propagation steps. A comparison of the chain end‐groups of polypropylene obtained in the presence of different catalysts shows that the extent of steric control upon insertion of the first monomer molecule results not only from the presence of alkyl titanium ligands larger than methyl and of titanium halide ligands larger than chlorine, but also from mutual ligand interactions.
Influence of termination and transfer on molecular weight distribution of polymers, 2. Radical‐radical termination and monomer chain transfer
Authors: Yan De‐yue , Cai Gang‐feng , Lan Zhi‐da
Published: April 2003

A non‐steady state kinetic treatment is rigorously performed for the free radical polymerization with instantaneous initiation, monomer chain transfer and radical‐radical termination. An explicit derivation of the molecular weight distribution function is given, and the expressions for other molecular parameters are provided. By means of the formulae given in this paper, the values of the molecular parameters of the polymer generated can be calculated from the initial conditions of polymerization and monomer conversion or reaction time.
Revival and modification of an ancient osmotic pressure equation
Authors: Schulz G. V. , Stockmayer Walter H.
Published: April 2003

An osmotic pressure equation proposed over 50 years ago is found to be consistent with the des Cloizeaux scaling relation for semi‐dilute polymer solutions in good solvents. With a physically plausible modification, the equation can also give a satisfactory representation of dilute solutions and of the cross‐over to the semi‐dilute regime.
The crystal and molecular structure of an asymmetric diacetylene monomer, 6‐(4‐dimethylaminobenzoyloxy)‐2,4‐hexadiynyl 3,5‐dinitrobenzoate
Authors: Vlasse Marcus , Koetzle Thomas F.
Published: April 2003

The crystal and molecular structure of an asymmetric diacetylene derivative, 6‐(4‐dimethylaminobenzoyloxy)‐2,4‐hexadiynyl 3,5‐dinitrobenzoate (1), was determined from x‐ray diffraction data. The crystals are monoclinic, P21/c with Z = 4 in a unit cell having dimensions, a = 11,116 (1) Å, b = 13,429 (2) Å, c = 14,672 (3) Å, β = 106,84 (6)°. The structure was solved by direct methods and refined by least‐squares techniques to an RF of 6,2% for 1 991 independent reflections. The diacetylene backbone chains are almost perfectly parallel to the ac‐plane; however, they are displaced from each other in the [010] direction. The solid‐state polymerization mechanism is discussed with respect to the geometric disposition of the diacetylene chains, which in this crystal are too far apart to permit polymerization by means of 1,4‐addition, consistent with the Baughman mechanistic model.
Liquid crystalline polymers, 1. Synthesis and structure‐properties relationship in some liquid crystalline polyetheresters
Authors: Jedliński Zbigniew , Franek Jan , Kuziw Piotr
Published: April 2003

Liquid crystalline aromatic‐aliphatic polyetheresters with mesogenic groups of different isomeric structures and flexible oligo(oxyethylene) spacers in the backbone were synthesized and their properties were studied. The influence of the mesogenic group structure, spacer length and nature of bonds linking the mesogenic groups and the spacers, on the phase transition temperatures was elucidated. On the basis of optical textures, observed in the polarizing microscope, smectic or nematic melts were found to be present in the polymers studied, depending on the mesogenic group structure.
The cationic polymerization of 3‐chloro‐2‐methyl‐1‐propene
Authors: Marek Miroslav , Roman Michael , Doskočilová Danica , Pokorný Svatopluk
Published: April 2003

The polymerization of 3‐chloro‐2‐methyl‐1‐propene was investigated at temperatures between 0 and −80°C, using AlCl3 and AlBr3 as initiators. The molecular weights of the resulting oily products depend on the polymerization temperature and varied in the range of the number‐average molecular weight M̄n = 400–620. The course of polymerization was studied and the characteristic groupings in the oligomeris were identified by means of 1H NMR and 13C NMR spectroscopy. Based on the results the mechanism of partial reactions was discussed to explain the new type of propagation in the cationic polymerization.
Liquid crystalline polyurethanes, 1. Polyurethanes based on 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]diphenylethanol
Authors: Tanaka Mamoru , Nakaya Tadao
Published: April 2003

Polyurethanes were synthesized from 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]diphenylethanol (3) with diisocyanates such as hexamethylene diisocyanate (4a), 4,4′‐methylenedicyclohexyl isocyanate (4b), 1,3‐cyclohexylenedimethyl isocyanate (4c), 2,4‐toluylene diisocyanate (4d) and 4,4′‐methylenediphenyl isocyanate (4e), and their thermal properties were investigated. The resulting polymers show a liquid crystalline state at 206–230, 160–216, 186–226 and 144–204°C, respectively, and the polymer obtained from 4e has a melting point at 272°C, determined by DSC and polarizing microscopy.
The reaction of nitroxyl radicals with hydroperoxides
Authors: Dulog Lothar , Bleher Rolf
Published: April 2003

In presence of traces of strong acids 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (2) induces the decomposition of hydroperoxides such as tert‐butyl hydroperoxide (1) and cumene hydroperoxide (CHP). 2 disproportionates in presence of hydrogen chloride into 1‐hydroxy‐2,2,6,6‐tetramethylpiperidine (5) and 2,2,6,6‐tetramethyl‐1‐oxopiperidinium chloride (4). This oxammonium salt is the active component which catalyses the decomposition of the hydroperoxide 1 by forming alkylperoxy radicals and the hydroxylamine derivative 5. The peroxy radicals are converted into alkyloxy radicals and molecular oxygen, and the oxyradicals regenerate 2 and an alcohol. The concentration of 2 remains constant through the whole period of the reaction. If 1 is present in an excess over 2 and the oxammonium salt 4, additional protons are needed to decompose the hydroperoxides.
Polymères thiocarboxyliques, 5. Synthèse de poly(oxyéthylène)s à fonction dithioester terminale. Application au traitement de cellules d'électrophorèse
Authors: Perlier Sylvie , Levesque Guy , Depraétère Pierre
Published: April 2003

Poly(oxyethylene)s with dithioster end groups were obtained from mono‐ and dihydroxyl terminated commercial polymers by reaction with dimethyl chloroacetamide, subsequent thionation of the amide group, and usual conversion of the thioamides into the dithioesters 14, 15 and 20, 21. The best results were obtained in the syntheses of the S‐carboxymethyl dithioesters (15 and 21). The resulting reactive poly(oxyethylene)s were grafted upon silica tubes and electrophoresis cells, previously activated by aminopropylsilanization. These graftings result in lowering of the surface potential of the tubes and in suppression of the electro‐osmosis flow in an electrophoresis cell tested with a TiO2 standard sample.
Polymer blends based on mesomorphic components, 1. Properties of poly(tetramethylene terephthalate)/poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) blends
Authors: Pracella Mariano , Dainelli Dario , Galli Giancarlo , Chiellini Emo
Published: April 2003

Blends of poly(tetramethylene terephthalate) [poly(butylene terephthalate) (PBT)] with a liquid crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) (HTH 10), obtained by solution precipitation, were characterized by optical microscopy, X‐ray diffraction and differential calorimetry. The morphology and phase behaviour of the blends are sensibly influenced by the composition. X‐ray data support the existence of separated crystal phase of the two polymers only for HTH10 contents higher than 30 wt.‐%. An increase of the clearing temperature of the original blends is found with decreasing concentration of the mesomorphic polymer in the range 100 to 30 wt.‐%. On cooling from the isotropic melt, a single crystallization process is observed, whose temperature decreases with increasing amount of HTH10. A large depression of the melting temperature of PBT is found in the composition range 0 to 50 wt.‐% of HTH10. Blends quenched from the isotropic state exhibit one single glass transition temperature, intermediate between those of the starting polymers. The results suggest the occurrence of miscibility phenomena of PBT and HTH10 in the amorphouse phase.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 3. UV absorption study of methylated styrene‐methacrylic acid and styrene‐acrylic acid copolymers
Authors: Wojtczak Zbigniew , S̀witała Maria
Published: April 2003

The microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers prepared in emulsion was studied by UV absorption measurements of their methylated derivatives. For comparative purpose random and graft‐block copolymers were also studied. Hypochromic effects at 259, 262, 264,5 and 269 nm are observed for both random and emulsion copolymers. The dependence of hypochromism at 269 nm on the content of methylated acid units suggests a similar microstructure of random and emulsion copolymers containing up to about 30 mol‐% of acid and differences in the microstructure of emulsion and random copolymers containing greater amounts of acid, especially in case of styrene‐acrylic acid copolymers. Moreover, it is found that UV absorption measurements may be used as a method of estimating the sequence length of styrene units in the copolymers.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 4. 1H NMR study of phenyl rings in methylated styrenemethacrylic acid and styrene‐acrylic acid copolymers
Authors: S̀witała Maria , Wojtczak Zbigniew
Published: April 2003

The sequence distribution in methacrylic acid‐styrene and acrylic acid‐styrene copolymers of various composition prepared in benzene and emusion were studied by using the aromatic proton region in the 1H NMR spectra of methylated copolymers. A digital computer was used to resolve overlapping peaks, and one Lorentzian and two Gaussian curves were fitted for their approximation. The study of random copolymers shows that styrene sequences as small as two and three units are contained. The run numbers and number‐average sequence lengths of styrene calculated for emulsion methacrylic acid‐styrene and acrylic acid‐styrene copolymers show that these copolymers do not have long sequences of styrene units.
Miscibility of mixtures from partially hydrolyzed poly(vinyl acetate) and poly(N‐vinyl‐2‐pyrrolidone)
Authors: Eguiazábal José I. , Calahorra Elena , Cortázar Mila , Guzmán Gonzalo M.
Published: April 2003

Polymers with different compositions of vinyl alcohol and vinyl acetate units (P(VA‐VAc)), obtained by alcoholysis of poly(vinyl acetate) with sodium methoxide, were mixed with poly(N‐vinyl‐2‐pyrrolidone) (PVP). The miscibility was studied observing glass transition temperatures by differential scanning calorimetry (DSC). The calorimetric results indicate that for vinyl alcohol unit contents in P(VA‐VAc) of roughly 70 wt.‐% or more, P(VA‐VAc)/PVP blends are fully miscible, whereas blends obtained from P(VA‐VAc) with vinyl alcohol contents lower than the above mentioned values are only partially miscible or even immiscible. The miscibility is attributed to hydrogen bond interactions between hydroxyl groups in P(VA‐VAc) and the carbonyl group of PVP.
Dielectric properties of a liquid crystalline siloxane copolymer
Authors: Pranoto Hendro , Bormuth Franz‐Josef , Haase Wolfgang , Kiechle Ulrich , Finkelmann Heino
Published: April 2003

An investigation on the molecular dynamics of a liquid crystalline side chain polymer using the dielectric relaxation method on oriented samples in the frequency range of 0,1 to 10 000 kHz is presented. The compound under investigation is a polysiloxane copolymer with two different mesogenic side chains and a phase sequence glassy‐smectic A‐nematic‐isotropic. Three main relaxation processes are found and assigned to the rotation of the side chains around the main chain, the glass transition process coupled with side chain motions, and a local motion in the glassy state, respectively. Evidence is found for a layered arrangement of the polymer main chain in the smectic phase and for a parallel correlation between the transverse components of the dipole moments.
The effect of cyclotetramer on the melting and crystallization behavior of poly(ethylene terephthalate)
Authors: Yu Tongyin , Bu Haishan , Jin Yimin
Published: April 2003

In the course of polycondensation of terephthaloyl chloride and ethylene glycol with subsequent baking, a cyclotetramer (M4) was isolated as a by‐product besides poly(ethylene terephthalate) (PET) and was identified by means of DSC, IR, GC‐MS and elemental analysis. The effects of this cyclotetramer M4 on the crystallization and on the morphological behavior of PET in the absence of residual catalyst were studied. It was found that M4 is soluble in the polymer melt. Thus, it only serves as a diluent and does not show any nucleation effect on the crystallization of PET.
Dependence of the kerr constants of benzene, p‐dioxane and poly(oxydiethylene terephthalate) on temperature
Authors: Mendicuti Francisco , Saiz Enrique
Published: April 2003

The Kerr constants of benzene, p‐dioxane, and of poly(oxydiethylene terephthalate) (PDET) in p‐dioxane solution were measured at several temperatures. As in the case of some other pure liquids reported in the literature, the values obtained for benzene and p‐dioxane are fitted by equations of the type mK = a + b · T−1 with a = (0,3 ± 0,6) · 10−26 m5 · V−2 · mol−1 and b = (16,0 ± 1,8) · 10−24 m5 · V−2 · mol−1 · K for benzene and a = (3,9 ± 0,9) · 10−26, b = −(8,2 ± 2,6) · 10−24, in the same units, for p‐dioxane. The values of the mean molar Kerr constant per repeating unit 〈mK〉/x extrapolated to infinite dilution in the case of PDET yield a values of d(〈mK〉/x)/dT = (13,5 ± 0,9) · 10−27 m5 · V−2 · mol−1 · K−1, in excellent agreement with the calculated result of 13,2 · 10−27 (in the same units) reported in the literature.
Stress‐optical behavior of atactic polypropylene networks upon elongation
Authors: DeBolt Lawrence C. , Riande Evaristo
Published: April 2003

Elastomeric networks prepared from atactic polypropylene were crosslinked with γ‐irradiation. The stress‐optical behavior of the unswollen networks was studied over a variety of elongation ratios and temperatures. At constant length, the stress f/A increases markedly at the glass transition temperature Tg, but the value of Tg does not change discernibly with increasing elongation. The unswollen networks exhibit negative birefringence for values of the elongation ratio λ below 1,8; however, for values of λ > 1,8, the birefringence becomes positive. This behavior was attributed to the presence of crystallites in the unswollen networks. Polypropylene networks, swollen with 1,3,5‐triethylbenzene and tetradecane, were also studied with regard to their stress‐temperature and birefringence‐temperature relationships. Whereas both the birefringence and stress of elongated networks swollen with the former solvent show a linear dependence on temperature, the birefringence of elongated networks swollen with tetradecane exhibits an anomalous increase at low temperatures which was attributed to poorly developed crystallinity. Values of the birefringence and stress corresponding to swollen networks were used to calculate the values of the optical configuration parameter Δa and its temperature coefficient. Theoretical calculations carried out with the rotational isomeric state model were used to evaluate Δa as a function of the stereoregularity of the chains. It was found that Δa decreases as the proportion of meso diads Pm increases, remaining almost constant for values of Pm > 0,7. The theoretical results of Δa and d In Δa/dT obtained for Pm > 0,4 reproduce very satisfactorily the experimental results obtained on the networks swollen with 1,3,5‐triethylbenzene.
Synthesis of polymers containing pyromellitdiimide and benzimidazole or pyrrolobenzimidazole moieties and of their corresponding model compounds
Authors: Yang Chin‐Ping
Published: April 2003

Some new polymers and model compounds were obtained from the reaction of 2‐phthalimidosuccinic anhydride (5) or 2,2′‐pyromellitdiimidodisuccinic anhydride (10). The way of the ring‐opening reaction of the anhydrides was found to depend on the solvents used. In some polar solvents such as DMSO, DMAC, NMP and DMF, β‐orientation occurs, but in THF, 1,4‐dioxane or acetone α‐orientation is preferred, which can be followed quantitatively by NMR spectroscopy. Subsequent dehydration to the pyrrolobenzimidazoles was found to proceed via the corresponding benzimidazolylcarboxylic acids rather than via the cyclic imides, the formation of the β‐from being faster than that of the α‐form. Polymer 24, containing pyromellitdiimide and pyrrolobenzimidazole moieties in the main chain, was synthesized by a three‐step reaction starting with 10 and 3,3′‐diaminobenzidine (8). In the first step, the poly(aminoanilic acid) (12), containing pyromellitdiimide rings, was prepared in a polar solvent. In the second step, condensation to the corresponding poly(imidoimidazolylpropionic acid) (20) was carried out thermally in solution or in solid state at 80–160°C. In the final step, the conversion into polymer 24 was performed by heating at a higher temperature or at reflux in acetic anhydride. The structures of the polymers were identified spectroscopically by comparison of the IR and NMR spectra with those of the corresponding model compounds.
Darstellung oligomerer und polymerer Cyclohexanokronenether
Authors: Blasius Ewald , Klein Wolfgang
Published: April 2003

Cyclohexano anellated crown ethers, bis(phenylcyclohexano)‐18‐crown‐6 and benzo‐cyclohexano‐18‐crown‐6 with cis‐ and trans‐ configuration at the cyclohexane ring were synthesized. The phenyl substituted crown ethers react with formaldehyde to form a crosslinked resin. Depending on the reaction conditions, the benzo anellated crown ethers give soluble polymers and/or linear and cyclic oligomers. Cyclic products could be isolated. Crosslinked polymers were synthesized from benzo‐cyclohexano‐18‐crown‐6 using additionally to formaldehyde a dialdehyde or a diarly compound.
Modification of amylose with diketene
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Riofrio Alicia
Published: April 2003

This work deals with the modification reaction of amylose with diketene using tertiary amines as catalysts. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. A linear dependence of the reaction rate on polymer, diketene and pyridine concentrations was found. The activation energy was found to be 27,2 kJ/mol (6,5 kcal/mol). Polymeric chelates between partially modified amylose and cupric ions (Cu2+) were prepared. However, not all of the β‐keto ester groups in the partially modified amylose participate in binding the cupric ions.
Polymerisationsauslösung mit substituierten ethanen, 8. Polymerisation von styrol
Authors: Błedzki Andrzej , Braun Dietrich
Published: April 2003

The free radical polymerization of styrene initiated by 1,1,2,2‐tetraphenyl‐1,2‐diphenoxyethane (TPPA) can be described as a kind of dead end polymerization. At the beginning of the polymerization, mainly oligomers are formed by primary radical chain termination. These oligomers can be characterized by thin layer and gel permeation chromatography and by mass spectroscopy. With increasing conversion and decreasing initiator concentration the molecular weight of the polymers is increasing. Contrary to the polymerization of methyl methacrylate with the same initiator, in the case of styrene the formed oligomers are not able to initiate once more the polymerization because the end groups formed by initiator radicals and styrene units are rather stable at normal polymerization temperatures (60 – 100°C).
Influence of termination and transfer on molecular weight distribution of polymers, 5. Chain transfer to monomer and impurity termination
Authors: Yuan Cui‐ming , Yan De‐yue
Published: April 2003

In this paper, the simultaneous effect of impurity termination and chain transfer to monomer on the molecular size distribution for the anionic polymerization with instantaneous initiation was studied theoretically in detail. The rigorous expressions for the molecular size distribution function and other molecular parameters were derived from a set of kinetic differential equations by means of the non‐steady state method. In accordance with these expressions, several examples of numerical calculation are given and a comparison is made between the polymerization system with chain transfer to monomer and that without monomer transfer.
Orientation process in thermotropic comb‐like polymers
Authors: Roth Hanna , Krücke Bernd
Published: April 2003

The influence of magnetic fields on the orientation of comb‐like silicon polymers was investigated by NMR methods. The sensitivity of proton NMR spectroscopy to phase transitions could be proven. Glass transition temperatures could be estimated by means of the super Lorentzian line shape of the wide line NMR signals. Magnetic fields of 2,1 T in connection with special temperature programs are able to effect a macroscopic orientation of the mesogenic side groups which are connected by mobile spacers to the backbone of the flexible polymer. The state of this orientation is preserved in a broad temperature range. The order parameter is derived as a function of temperature.