bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization in inverse microemulsions, 1. Homopolymerizations of water‐ and oil‐soluble monomers in inverse microemulsions
Authors: Vašková Viera , Juraničová Viera , Bartoň Jaroslav
Published: April 2003

Homopolymerization of acrylamide (AAM) as well as of methyl methacrylate (MMA) in inverse microemulsions was studied and compared with the homopolymerization of these monomers in homogeneous systems. Initiators with various solubilities in water were used. Homopolymerization of AAM in inverse microemulsion was found to be an extremely fast reaction independent of the type of the initiator used. It is assumed that polymerization takes place predominantly in the interlayer between the aqueous phase and the oil phase. In the case of MMA the homopolymerization in inverse emulsion is a relatively slow process. It is assumed that polymerization of MMA in the systems studied takes place in the oil macrophase.
Thermo‐oxidative degradation of polyamide 6 and polyamide 6,6. Structure of UV/VIS‐active chromophores
Authors: Karstens Ties , Rossbach Volker
Published: April 2003

In heat‐treated polyamide 6 and polyamide 6,6 fibres UV/VIS‐active chromophores are found, which originate from two different sources: one type of chromophore (structured UV spectrum) arises during polycondensation and the spinning of the fibres (molten phase), the other (nonstructured UV spectrum) occurs as a result of a thermo‐oxidation is based on conjugated oligoenimies , as is shown by a combination of UV/VIS spectroscopy and fluorescence excitation and emission spectroscopy with chemical analysis. The concentration of the various oligoenimine species depends upon the temperature and duration of the thermooxidation. For a temperature of 160°C and a duration of 2 hours, for example, the following oligoenimine concentrations were found (UV spectroscopy with computer‐aided evaluation): for i = 0: 44; i = 1: 13; i = 2: 4; i = 3: 1; i = 4: 0,3 (values expressed in mmol/kg).
Unvernetzte epoxide‐amin‐additionspolymere, 32. Hochmolekulare polykationen vom michler‐hydrolblau‐typ und ihre dielektrische charakterisierung
Authors: Klee Joachim , Hörhold Hans‐Heinrich , Kremer Friedrich
Published: April 2003

A high‐molecular‐weight poly(leuco base) (Mn = 11000–18000) was obtained by addition polymerization of N,N′‐dibenzyl‐4,4′‐methylenedianiline (2) and 2,2‐bis[4‐(2,3‐epoxypropoxy)‐phenyl]propane (diglycidyl ether of Bisphenol A) (1).

The oxidation of this addition polymer with chloroanil, iodine, bromine, chlorine or antimony pentachloride results in polymeric dyes (absorption at λ = 620 nm) containing units of the “Michler Hydrolblau” type. The dielectric behavior in the frequency range 102 Hz up to 107 Hz shows a dependence of the conductivity on the temperature. Polymer 4c exhibits a conductivity of σ = 6 · 10−6 S/cm at 134,3°C and 106 Hz.
Synthesis and mesomorphic properties of a semiflexible polyester based on 4,4′‐sebacoyldioxydibenzoyl chloride and methylhydroquinone
Authors: Costa Giovanna , Trefiletti Vincenzo , Valenti Barbara , Gallot Bernard
Published: April 2003

Many samples of a semiflexible thermotropic polyester were synthesized by low‐temperature solution polycondensation of 2‐methylhydroquinone (5) and 4,4′‐sebacoyldioxydibenzoyl chloride (4) and characterized by polarizing microscopy, differential scanning calorimetry and X‐ray diffraction. The influence of some experimental parameters, such as polymerization temperature, tertiary amine and monomer concentration, on polymer yields and molecular weights was studied. Thermal behaviour, in terms of thermal stability of the polyesters and range of mesophase stability, was investigated as a function of the molecular weight of the samples. Thermal treatments and X‐ray diffraction at different temperatures were performed to achieve a better understanding of the transitions characteristic of this polyester. All the samples give a nematic phase; on as‐polymerized specimens a solid‐solid transition was also detected.
Crosslinking reactions of polyphenylene type polymers containing acetyl end‐groups with o‐carboranylmethoxy‐containing organosilazanes
Authors: Teplyakov Mikhail M. , Khotina Irina A. , Dmitrenko Alla V. , Korshak Vasili V. , Ismailov Boris A. , Myakushev Victor D.
Published: April 2003

Carborane‐containing oligoorganosilazanes (COS) (20 to 60 wt.‐%) prepared by coammonolysis of (o‐carboranylmethoxy)dichloro(phenyl)silane and trichloro(phenyl)silane (COS 1), or 1‐chloro‐1‐phenyl‐1‐sila‐2,7‐dioxa‐4,5‐(1,2‐carborano)cycloheptane and dichloro(dimethyl)‐silane (COS 2), were used to crosslink polyphenylene type prepolymers on the basis of 4,4′‐oxydiacetophenone and acetophenone (FPP‐1). This allowed the reduction of the crosslinking temperature of FPP‐1 by 100–150°C, retaining a high heat resistance of the final crosslinked polymer. Octamethylcyclotetrasilazane (15 wt.‐%) was used to crosslink the carborane‐containing prepolymers on the basis of 1,2‐bis[4‐(4‐acetylphenoxy)phenyl]‐o‐carborane and acetophenone (FPP‐2) and 1,2‐bis(4‐acetylbenzyl)‐o‐carborane and acetophenone (FPP‐3). At 350°C a polymer was formed with a gel fraction amounting to 94%.
Liquid‐crystalline poly(4‐hydroxybenzoate)s with phenethyl side chains
Authors: Vogel Wilfried , Heitz Walter
Published: April 2003

An important means to decrease the melting point of LC‐polymers is the statistical arrangement of substitutents along the chain. Thermotropic liquid‐crystalline poly(4‐hydroxybenzoate)s bearing one phenethyl substituent in different positions of the monomer were synthesized via melt polycondensation. The relation between the arrangement of the substituent along the polymer backbone and the properties of the polyesters was investigated. The two homopolyesters with the substitutent either in 2‐ or 3‐position reveal highly crystalline and poorly soluble products. In contrast to this, the random copolyester is an amorphous and well soluble polymer.
Targetable photoactivatable drugs, 2. Synthesis of N‐(2‐hydroxypropyl)methacrylamide copolymeranti‐thy 1.2 antibody‐chlorin e6 conjugates and a preliminary study of their photodynamic effect on mouse splenocytes in vitro
Authors: Krinick Nancy L. , R̆íhová Blanka , Ulbrich Karel , Strohalm Jir̆í , Kopec̆ek Jindr̆ich
Published: April 2003

Two N‐(2‐hydroxypropyl)methacrylamide (HPMA, 1) copolymer‐chlorin e6‐anti‐Thy 1.2 antibody conjugates were synthesized. They differ in the method of antibody binding. In conjugate 11, the polyclonal anti‐Thy 1.2 antibody was bound via Nϵ‐amino groups of lysine residues. Conjugate 14 contained anti‐Thy‐1.2 antibodies bound via oxidized carbohydrate groups present near the hinge region in the Fc part of the antibody molecule. The photodynamic activity of these conjugates towards mouse splenocytes in vitro was compared with the activity of a nontargetable HPMA copolymer‐chlorin e6 conjugate (15) and free chlorin e6. Whereas free chlorin e6 was cytotoxic both when kept in the dark and when splenocytes were irradiated, the binding of the drug to HPMA copolymers considerably decreased its cytotoxicity in the dark. Conjugates 11 and 14 containing targeting polyclonal anti‐Thy 1.2 antibodies were more biologically active compared to the nontargetable conjugate 15. Conjugate 14, which contained anti‐Thy 1.2 antibodies bound at a specific location was the most active both in its photodynamic effect on viability of splenocytes and/or suppression of the primary antibody response of mouse splenocytes towards sheep red blood cells in vitro. The results demonstrate the importance of the chemistry of antibody binding on the biological activity of targetable polymeric drugs.
Interaction between DNA and biometal ions. Variations of structural and macromolecular parameters
Authors: Kornilova Svetlana V. , Blagoi Yuri P. , Shkorbatov Alexander G.
Published: April 2003

The interaction of Mg2+, Ca2+, Mn2+, and Cu2+ ions with the DNA macromolecule is studied in a wide range of ionic strengths, 2 · 10−4 to 10−1 mol · 1−1. It is shown that the observed considerable changes in the intrinsic viscosity and the excluded volume parameter of DNA are due to the screening of the phosphate groups and nitrogen bases of DNA during the direct binding of the ions. The bivalent ion binding to DNA leads to suppression of the effects of the long‐range interactions in the macromolecules at concentrations two or three orders of magnitude lower than those for monovalent ions. The intrinsic viscosity and the excluded volume parameter are universally dependent on the ion binding degree.
Molecular structure of plasticizers and antiplasticization
Authors: Suvorova Anna I. , Hannanova Elvira G.
Published: April 2003

Plasticization of the polycarbonate of bisphenol A (1) by dibutyl 4,4′‐ethylenedibenzoate (2) and dibutyl 4,4′‐stilbenedicarboxylate (3) was studied in order to establish the influence of the molecular rigidity on the antiplasticization phenomenon. UV spectroscopy, dielectric and mechanical properties proved that a rigid trans‐configuration of the “plasticizer” molecules and a strong interaction enhance antiplasticization.
Model reactions of pyridinecarboxylic acids with glycidyl phenyl ether
Authors: Hsu Ying Gev , Chen Keng Ming
Published: April 2003

The reactions of 3‐pyridinecarboxylic acid (nicotinic acid, NA) and 4‐pyridinecarboxylic acid (isonicotinic acid, ISNA) with 2,3‐epoxypropyl phenyl either (glycidyl phenyl ether, GPE) were studied by means of high performance liquid chromatography (HPLC). It is found that both reactions involve two‐step mechanisms and have induction periods. Two products, pyridinium salt and ester, are obtained in each study. The formation of pyridinium salt is the cause of the occurrence of the induction period. After the induction period, the kinetics of the reaction is second order. Pyridinium ions do not form complexes with carboxylate ions of pyridinecarboxylates but form activated complexes with the hydrogen‐bonded complexes of pyridinecarboxylic acids and GPE to activate the esterification reactions. The mechanisms of the reactions are discussed in detail.
Polymeric prodrugs, 8. Synthesis and hydrolytic behaviour of dextran‐bound anticancer agents
Authors: Móra Melinda , Pató János
Published: April 2003

3‐Chloro‐2‐hydroxypropyl ether of dextran (3a) and succinyldextran (4a) were prepared and used for coupling the anticancer agents 6‐purinethiol and 5‐fluorouracil. The “in vitro” drug liberation was measured at pH 7,2 and 8,8. The release rate from the dextran conjugates was compared with that of the poly(1‐vinyl‐2‐pyrrolidone‐co‐maleic acid) derivatives of these drugs. The effect of the macromolecular chain on the hydrolytic behaviour of the polymer‐bound drugs was clearly detected.
Polylactones, 19. Anionic polymerization of L‐lactide in solution
Authors: Kricheldorf Hans R. , Kreiser‐Saunders Ingrid
Published: April 2003

The anionic polymerization of L‐lactide was studied with four potential initiators of different basicity: potassium benzoate, potassium phenoxide, potassium tert‐butoxide and butyllithium. Regardless of the solvent, only the two most basic initiators proved to be reactive enough to initiate and maintain the polymerization. This result and the formation of benzyloxy end‐groups upon addition of benzyl bromide prove that the polymerizations proceed via alkoxide chain ends. Absence of initiator fragments in the isolated polylactide chains suggests that initiation mainly involves deprotonation of L‐lactide, whereas nucleophilic substitution only occurs to a minor extent. Furthermore, optical rotation measurements indicate that both the initiator and the alkoxide chain end cause partial racemization regardless of solvent and temperature. Furthermore, it was found that reagents such as triethylamine, pyridine or potassium benzoate which are not reactive enough to initiate polymerization, are basic enough to cause partial racemization of L‐lactide by deprotonation.
Alkoxy substituted liquid‐crystalline aromatic copolyesters
Authors: Schleeh Thomas , Kßmehl Gerhard , Hinrichsen Georg
Published: April 2003

The increasing exchange of 2,5‐dipentyloxyterephthaloyl units by terephthaloyl units, studied up to 60 mole‐%, influences the chemical and physical behaviour of the corresponding copolyesters. The copolyesters with an exchange of 30 mole‐% and more become insoluble in chloroform and dichloromethane. The decomposition temperatures increase and the copolyesters show a better long‐time thermal stability. The melting and clearing intervals shift to higher temperatures. The low temperature liquid‐crystalline (LC) phase, which can be seen very well in the HT05‐100 samples, disappears continuously with the increase of the terephthaloyl content. The solid to LC (high temperature phase) transition enthalpies decrease linearly with increasing terephthaloyl content.
Die ermittlung der protonierungsgleichgewichtskonstanten von ankergruppen komplexbildender ionenaustauscherharze
Authors: Huhn Gernot , Müller Helmut , Krauß Dieter , Schwachula Gerhard , Szabadka Ödön
Published: April 2003

A previously derived equation for the calculation of the protonation constants of immobilized ligands is used for a description of the protonation equilibria of chelating resins containing iminodiacetic acid groups. The equilibrium protonation constants of technical and of pure ion exchange resins were determined. Data obtained from the pH titration curve, and measurements of counter ion and water uptake were used to calculate the three steps of protonation at 298 K. The obtained values of the equilibrium protonation constants were correlated with properties of the investigated resins like composition and degree of crosslinking.
Reversible immobilization of drugs on a hydrogel matrix, 2. Diffusion of free chloramphenicol from poly(2‐hydroxyethyl methacrylate) hydrogels
Authors: Yean Leanirith , Bunel Claude , Vairon Jean‐Pierre
Published: April 2003

The diffusional behaviour of chloramphenicol

D‐(–)‐threo‐N‐[2‐hydroxyl‐1‐hydroxymethyl‐2‐(4‐nitrophenyl)ethyl]dichloroacetamide.

(1) from poly(2‐hydroxyethyl methacrylate) (pHEMA) hydrogels is reported. The drug was trapped in the matrix cross‐linked with various amounts of ethylene dimethacrylate (0,5–18 mol‐%), and the diffusion was followed from disc‐shaped slabs at swelling equilibrium in water (phosphate buffer, pH 7) at 37°C. The diffusion obeys the second Fick law and is rapid (D ≈ 10−8 cm2 s−1) in the case of the slightly crosslinked hydrogels used for corneal lenses. The diffusion coefficients decrease almost exponentially with increasing cross‐linking ratio, and the process appears predominantly controlled by the free volume contribution of the diluent rather than by the sieving of the network.
Multiple melting temperatures of poly(3,3‐diethylthietane)
Authors: Marco Carlos , Lazcano Silvia , Fatou José G.
Published: April 2003

The melting behaviour of semicrystalline poly(3,3‐diethylthiethane) (PDET), was studied by differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), small‐angle light scattering (SALS), and thermooptical analysis (TOA). Two samples of number‐average molecular weights 6,0 · 104 and 1,8 · 105 and rather narrow molecular weight distributions (ratio of weight‐to number‐average molecular weights M̄w/M̄n = 1,3) were analyzed. When PDET is isothermally crystallized from the molten state in the range 275–333 K, the calorimetric curves show one or two melting endotherms, depending on crystallization temperature (Tc) and heating rate. WAXS analysis shows conclusively that polymorphism is absent. It was shown that the melting behaviour of PDET is being dictated by processes of melting and recrystallization occurring during the experimental analysis.
Polyanion‐polykation‐komplexe mit saccharid‐substituierten polyacrylsäuren und polyvinylaminen
Authors: Kötz Joachim , Philipp Burkart , Pfannemüller Beate
Published: April 2003

Samples of saccharide‐substituted poly(acrylic acid) and polyvinylamine varying in DS and length of the saccharide side chains were investigated with regard to their polyelectrolyte character by determining their pK0a values and by a potentiometric, conductometric and turbidimetric titration with an oppositely charged polyelectrolyte. Criteria employed for the evaluation of these “symplex titrations” were the ratio of cationic to anionic groups at the endpoint and the course of the turbidimetric curve classified according to several schematized curve types. From the results obtained it can be concluded that substitution by saccharide side chains in the case of poly(acrylic acid) impedes Coulombic interaction to some extent only by steric hindrance, while in the case of the substituted polyvinylamines also intermolecular H‐bonds between the amino groups and the saccharide side chains have to be taken into account.
Asymmetric induction polymerization of monomer salts prepared from 1,3‐butadiene‐1‐carboxylic acid and optically active amines
Authors: Yamaguchi Hidemasa , Iwama Tetsuroh , Hayashi Toshio , Doiuchi Tohru
Published: April 2003

Chiral monomer salts, prepared from 1,3‐butadiene‐1‐carboxylic acid (BuCOOH) and optically active 1‐cyclohexylethyl‐ or bornylamines (CyA, BoA), were polymerized in methanol with AIBN. The obtained optically active polymer salts (Poly‐1(BoA) and Poly‐1(CyA)) were deaminated by repeated reprecipitation. The deaminated polymers (Poly‐2(BoA) and Poly‐2(CyA)) were optically inactive. In the case of the salt from optically active 1‐phenylethylamine (PhA) and BuCOOH (PhA/BuCOOH), Poly‐2(PhA) was still optically active even after the removal of PhA from Poly‐1 (PhA). Furthermore, PhA/BuCOOH was polymerized in the mixed solvent of methanol/benzene of methanol/chloroform. From the optical behavior of Poly‐2 and the 1H NMR spectra of the monomer salts, the role of the phenyl ring in the monomer salt on the asymmetric induction polymerization is discussed.
Soft‐segment crystallization and properties of copoly(ether‐ester) elastomers
Authors: Lembicz Franciszek , Slonecki Jerzy
Published: April 2003

Differential scanning calorimetry, dynamical mechanical, and spin probe measurements were conducted to study relaxation and soft‐segment crystallization phenomena in block copoly(ether‐ester) elastomers obtained through transesterification and melt polycondensation of dimethyl terephthalate, 1,4‐butanediol and poly(ethylene oxide). The elastomers investigated differed both in molecular weight of the poly(ethylene oxide) used as well as in their ratio of hard to soft segments. It was found that a crystallization process of the soft‐segment phase does not occur for oligoethers with a molecular weight lower than 1000. The spin probe method can be used to monitor the melting process and additionally it supplies information on the relaxation processes taking place in the amorphous part of the soft phase. Some data on the crystallization of the rigid phase are also given.
Observation of the conformation and structure of some liquid‐crystal polymers by small‐angle neutron scattering
Authors: Pépy Gérard , Noirez Laurence , Keller Patrick , Lambert Marianne , Moussa Fernande , Cotton Jean‐Pierre , Strazielle Claude , Lapp Alain , Hardouin Francis , Mauzac Monique , Richard Hélène
Published: April 2003

The conformation of the backbone and the structure of the mesogenic groups of some liquidcrystal polymethacrylates and polysiloxanes were determined by small‐ and low‐angle scattering of neutrons. A strong magnetic field aligned the mesomorphic monodomains. For most samples and phases the polymer backbone adopts an oblate shape versus the mesogenic director. The observation of several diffuse spots together with Bragg peaks allows to propose models for the structure of these samples.
Synthesis and characterisation of chiral nematic liquid‐crystalline copolymers with the chiral centre in the flexible spacer
Authors: Cowie John M. G. , Hunter Hugh W.
Published: April 2003

The synthesis and characterisation of a series of novel chiral nematic liquid‐crystalline combbranch copolymers having the chiral centre in the flexible spacer are described. The copolymers, prepared from the chiral monomer (S)‐2‐(4′‐cyano‐4‐biphenylyloxy)‐1‐methylethyl methacrylate (7) and the nematogenic monomer 4‐cyanophenyl 4‐(6‐acryloyloxyhexyloxy)benzoate (8), were found to form planar textures which display bright reflection colours at low chiral monomer feed values. These coloured textures could be stored reversibly by cooling below Tg.
Epoxy prepolymers cured with boron trifluoride‐amine complexes, 1. Influence of the amine on the curing window
Authors: Bouillon Nelly , Pascault Jean‐Pierre , Tighzert Lan
Published: April 2003

Different pure complexes were synthesized by an interchange reaction of BF3‐etherate with amines in dichloromethane. All of the resulting complexes are solid, but they can be dissolved in a low‐molecular‐weight poly(ethylene oxide) to favour their use as initiators. DSC analysis demonstrated strong interactions between the BF3‐complex and the polyether. This is probably caused by the formation of hydrogen bonding between the hydrogens of the amine and the ether groups. The reactivity of amine complexes was characterized by reaction with the epoxy prepolymer. The reactivity increases with decreasing basicity of the amine, showing a relationship between the initiation and propagation of the expoxy homopolymerization and the stability of the complex. A slight influence on the reaction temperatures by the amount of polyether is observed, but the glass transition temperature of the epoxy network decreases when a large excess is used.
Epoxy prepolymers cured with boron trifluoride‐amine complexes, 2. Polymerization mechanisms
Authors: Bouillon Nelly , Pascault Jean‐Pierre , Tighzert Lan
Published: April 2003

The kinetics of the polymerization of phenoxymethyloxirane (6) initiated by the BF3 complex of 4‐chloroaniline (7) solubilized in oligo(ethylene oxide) of molecular weight 300 (PEO) is characterized by an initial induction period, followed by a propagation step with a rate Rp = k [6] · [7]0,32 · [PEO]−0,55. The length of the induction period decreases with [7] and increases with [PEO]. However, Rp increases with [7] and decreases with [PEO]. The reaction can be explained by the activated monomer mechanism.
Epoxy prepolymers cured with boron trifluoride‐amine complexes, 3. Polymerization mechanism of a prepolymer containing epoxy groups
Authors: Bouillon Nelly , Pascault Jean‐Pierre , Tighzert Lan
Published: April 2003

The reaction of a diepoxy prepolymer (2) initiated by the BF3‐complex of 4‐chloroaniline (3), solubilized in poly(ethylene oxide) (PEO) of molecular weight 300, was studied. An initial induction period was observed, followed by a pseudo‐stationary stage with decreasing reaction rate due to gelation. In the pseudo‐stationary stage, the homopolymerization rate is given by the expression: Rp = k[2]1 · [3]·−0,55 · [PEO]·0,57. In addition to 2, we also used a Novolac prepolymer 4. Different networks were prepared and analyzed by thermal and mechanical techniques, and their water‐absorption rates were measured.
Morphology and phase transition study of polymers with discotic mesogens
Authors: Hsu Tsuey‐Chen , Hüser Bernhard , Pakula Tadeusz , Spiess Hans Wolfgang , Stamm Manfred
Published: April 2003

The discotic liquid‐crystalline polymers poly[oxy(3,7,10,11‐tetrapentoxy‐2,6‐triphenylenediyl)‐oxycarbonyltetradecamethylenecarbonyl] (1), containing discotic mesogenic groups in the main chain and poly[methyl(3,6,7,10,11‐pentapentoxy‐2‐triphenylenyloxyundecyl)siloxane] (2) with disc‐like groups attached to the polymer chain by flexible spacers, are studied by X‐ray diffraction, solid‐state nuclear magnetic resonance, differential scanning calorimetry and dynamic mechanical measurements, in order to determine the dynamic and structural transitions. It is shown that low‐temperature softening in both polymers is caused by the mobility of short aliphatic side chains attached to the discotic units. Once formed, the columnar mesomorphic structure is stable up to the temperature of isotropization. For the main‐chain polymer, a third transition is observed in samples quenched from the melt. The transition is related to the mobility of the main chain in an amorphous structure, where the discotic units are not organized in columns.
Miscibility in blends of random copolymers of styrene and acrylontrile with block copolymers of styrene and methyl methacrylate
Authors: Kressler Jörg , Karasz Frank E. , Kammer Hans‐Werner , Morgenstern Ute
Published: April 2003

Phase behavior in blends of random copolymers of styrene and acrylonitrile with block copolymers of styrene and methyl methacrylate was studied by light scattering, light microscopy and glass transition temperature measurements. The results are compared with those of respective blends containing random copolymers of styrene and methyl methacrylate. In terms of macrophase separation, the block copolymers display a more extended miscibility domain with styrene/acrylonitrile copolymers than the random copolymers. However, the extent of the miscibility domain varies as a function of temperature. Unlike the random copolymer blends, all blends containing block copolymers exhibit lower critical solution temperature behavior. Finally, it is established that the systems studied here undergo spinodal decomposition leading to macrophase separation.
Enantioselective hydro‐oligomerization (protio‐ or deuterio‐) of α‐olefins
Authors: Pino Piero , Galimberti Maurizio , Prada Paolo , Consiglio Giambattista
Published: April 2003

The enantioselective protio(deuterio)oligomerization of propene, 1‐pentene and 4‐methyl‐1‐pentene was carried out with the diastereomerically pure catalyst precursor (−)‐(R)‐ethylenebis [1–3a,7a‐η‐(4,5,6,7‐tetrahydro‐1‐indenyl)]zirconium (S)‐1,1′‐bis‐2‐naphtholate (3) and/or with (−)‐(R)‐ethylene [1–3a,7a‐η‐bis(4,5,6,7‐tetrahydro‐1‐indenyl]dimethylzirconium (1) in the presence of methylalumoxanes. The enantioselectivity of both reactions which take place (deuteration and oligomerization) is from fair to high and essentially independent of the catalyst precursor. In the hydrooligomerization the enantioface of the olefinic monomer which prevailingly reacts is from a geometric point of view the same for all three substrates. In the case of 1‐pentene and 4‐methyl‐1‐pentene the enantioface prevailing embedded in the oligomers is opposite to that prevailingly deuterated. The significance of the growing chain for enantioface selection during stereospecific polymerization is thus emphasized.
Model networks based on poly(1,3‐dioxolane)
Authors: Franta Emile , Gérard Eric , Gnanou Yves , Reibel Léonard , Rempp Paul
Published: April 2003

Polyurethane networks whose elastic chains are constituted of hydrophilic poly(1,3‐dioxolane) of well‐defined molecular weight were synthesized using an end‐linking process. The poly(1,3‐dioxolane) (PDXL) precursor polymers, fitted with OH functions at both chain ends, were prepared cationically in the presence of ethylene glycol. The latter compound is involved in the initiation reaction and provides the OH functions at the chain ends. The end‐linking process, leading to the formation of the poly(1,3‐dioxolane) network, involves the reaction of the precursor with a stoichiometric amount of a plurifunctional isocyanate, under conditions that minimize defects. The swelling behavior of the poly(1,3‐dioxolane) networks is compared with that of poly(ethylene oxide) networks previously studied.
Evaluation of individual rate constants from the chain‐length distribution of polymer samples prepared by intermittent (rotating sector) photopolymerization, 3. Theoretical foundations for termination by disproportionation
Authors: Zifferer Gerhard , Olaj Oskar Friedrich
Published: April 2003

The chain‐length distribution and its moments were calculated for a periodically interrupted photopolymerization with termination by disproportionation and negligible chain transfer. For a wide range of experimental conditions, which are readily accessible in the overwhelming majority of cases, the position of the first point of inflection in the chain‐length distribution corresponds exactly to the quantity kp [M]t0, kp representing propagation rate constant, M monomer and t0 the period length. Thus kp can be directly evaluated from the chain‐length distribution of the polymer. Together with the ratio k/kt, kt being the termination rate constant, calculated from the rate and weight‐average degree of polymerization according to a universal relationship—the validity of which is also verified — resolution into the individual rate constants is easily accomplished. The dependence on experimental conditions of the ratio weight‐ to number‐average degrees of polymerization Pw/Pn, which is a measure of the width of the molecular weight distribution of the polymer formed, is discussed.
Synthesis and rheological study of some maleic acid and fumaric acid stereoregular polyesters, 5. Structural study by 1H and 13C NMR of random, multi‐block and alternating unsaturated copolyesters from fumaric, maleic and phthalic acid potassium salts and 1,4‐dibromobutane
Authors: Sepulchre Marie‐Odile , Moreau Michel , Sepulchre Maurice , Djonlagić Jasna , Jaćović Mihailo S.
Published: April 2003

The sequence distribution in random, multi‐block and alternating copolyesters based on the reaction of fumaric, maleic and phthalic acid potassium salts with 1,4‐dibromobutane were examined by 1H and 13C NMR spectra. Quantitative sequence distibution results were obtained from the analysis of 13C NMR spectra. The different structures of synthesized copolyesters, expected from the experimental procedures used, were confirmed. In addition, it can be concluded that the esterification route used is irreversible and that no appreciable transesterification reaction between two different ester groups occurs in the course of the synthesis.
13C NMR studies on the relative reactivity of isocyanate groups of isophorone diisocyanate isomers
Authors: Bialas Norbert , Höcker Hartwig , Marschner Michael , Ritter Wolfgang
Published: April 2003

Model reactions of isophorone diisocyanate (IPDI (1)) with ethanol were examined using 13C NMR technique to locate the chemical shift of different urethane and isocyanate groups in the products. The reactivity of the secondary and primary isocyanate group of the IPDI isomers is catalyst‐dependent. In the presence of Lewis acids (e.g., dibutyltin dilaurate) the secondary NCO group is more reactive, while in the presence of Lewis bases (e.g., triethylamine) it is the primary one. This effect allowed the chemical shift assignment of urethane‐ and isocyanate carbonyl C atoms in adducts formed by reaction of IPDI with ethanol in mole ratio NCO:OH = 2:1. In ethyl carbamates from the main isomer the chemical shift δ = 155,93 ppm is assigned to the carbonyl C atom of the urethane group at the secondary C atom, the signal at δ = 157,07 ppm to the primary urethane group. Furthermore, it was possible to assign the signal at δ = 122,12 ppm to the primary NCO group and the signal at δ = 122,98 ppm to the secondary NCO group of isophorone diisocyanate.
Hydrogels for site‐specific oral delivery. Poly[(acrylic acid)‐co‐(butyl acrylate)] crosslinked with 4,4′‐bis(methacryloylamino)azobenzene
Authors: Přádný Martin , Kopeček Jindřich
Published: April 2003

Copolymers of acrylic acid and butyl acrylate crosslinked with 4,4′‐bis(methacryloylamino)‐azobenzene were synthesized by radical copolymerization with different amounts of acrylic acid and crosslinker. They were characterized by equilibrium degree of swelling, modulus of elasticity in compression at pH 2 and 7, and effective network density. The acido‐basic properties of crosslinked copolymers were compared with linear (soluble) ones of the same composition. The study of the dependence of the apparent dissociation constant (pKapp) on the degree of dissociation has shown that conformational transition from the compact to the random conformation of the polymeric chains occurs only in crosslinked copolymers. The high values of pKapp obtained indicate that strong Donnan effects and low polarity of environment of carboxy groups are operative in acido‐basic equilibria.
An unusual bacterial polyester with a phenyl pendant group
Authors: Fritzsche Katharina , Lenz Robert W. , Fuller R. Clinton
Published: April 2003

The microorganism Pseudomonas oleovorans is known to produce polyesters containing 3‐hydroxyalkanoate units when grown on n‐alkanes and n‐alkanoic acids under nutrient limiting conditions, but when 5‐phenylvaleric acid was supplied as the only carbon source, poly[3‐hydroxy‐5‐phenylpentanoate], a polyester with a phenyl pendant group, was produced. The optimum substrate concentrations and harvesting times were determined by measuring the change of cell growth and polymer yield during the growth. A 12‐L cell culture yielded 222,5 mg polymer/L and 25% polymer per cellular dry weight. This bacterial polymer showed an optical rotation of [α] = −24,5° ± 0,2°. The structure was corroborated by 1H NMR and 13C NMR spectroscopy. The composition of the polymer was also determined by methanolysis to the methyl ester of the repeating unit, which was subsequently analyzed by GC. By this procedure the polyester was found to be a homopolymer to the extent of at least 99%. The polyester has a glass transition at 13°C, a melting range from 54 to 69°C, and a weight‐average molecular weight of M̄w = 350000 with a polydispersity M̄w/M̄n of 3,5, as determined by GPC relative to polystyrene standards.
Crystallization of the γ‐form of isotactic poly(propylene), 2. Synchrotron radiation measurements
Authors: Marigo Antonio , Marega Carla , Zannetti Roberto , Paganetto Guglielmo , Schmidt Stephan , Zachmann Hans Gerhard
Published: April 2003

Synchrotron radiation measurements were employed in recording wide‐ and small‐angle X‐ray diffraction patterns during the crystallization of isotactic poly(propylene) in γ‐form. In particular, crystallization phenomena of this form are reported for a fraction of a random propylene‐ethylene copolymer (4 wt.‐% of ethylene) previously investigated by traditional diffraction methods. On slow cooling from the melt, the main decrease in long period L occurs between 88 and 76°C where the degree of crystallinity is almost constant. This may be explained by a flattening of lamellae.
Synthesis of arylsubstituted monomers for high‐performance polymers
Authors: Land Horst Tore , Hatke Wilfried , Greiner Andreas , Schmidt Hans‐Werner , Heitz Walter
Published: April 2003

The arylation of monomers for high‐performance polymers is described. The reaction of dibenzoyl peroxide with various 1,4‐disubstituted benzene derivatives results in phenylation. Minimization of side reactions is discussed. The Ni‐promoted reaction of Grignard compounds with iodoarenes was used to introduce the phenyl, biphenyl, and naphthyl substituent.
Release of 5‐aminosalicylic acid from bioadhesive N‐(2‐hydroxypropyl)methacrylamide copolymers by azoreductases in vitro
Authors: Kopečková Pavla , Kopeček Jindřich
Published: April 2003

N‐(2‐hydroxypropyl)methacrylamide (HPMA) copolymers (11a, b) containing side chains terminating in 5‐aminosalicylic acid (5‐ASA) and fucosylamine (10) were synthesized. A reactive polymeric precursor (9), a copolymer of HPMA (7) and N‐methacryloylglycylglycine p‐nitrophenyl ester (8), was consecutively aminolyzed with 5‐[4‐(2‐aminoethylcarbamoyl)phenylazo]‐salicylic acid (6) and fucosylamine (10). The latter renders the copolymers bioadhesive in the gastrointestinal tract. The release of 5‐ASA from 11a, b was studied in vitro by incubation with cell‐free extracts isolated from rat cecum, and factors influencing the degradation were determined. The rate of azo bond cleavage of 11a, b was similar to the rate of cleavage of low‐molecular‐weight substrates, methyl orange and compound 6. Addition of benzyl viologen, a low potential electron carrier, increased the rate of cleavage. At optimal benzyl viologen and substrate concentration ratios, a zero order release was observed. At higher substrate concentration, the rate of 5‐ASA release decreased.
Dynamics of photoinduced isomerization of azobenzene moieties in liquid‐crystalline polymers
Authors: Wiesner Ulrich , Antonietti Markus , Boeffel Christine , Spiess Hans Wolfgang
Published: April 2003

Forced Rayleigh scattering was used to investigate the dynamics of photoinduced isomerization of azobenzene involved in reversible holographic information storage. The studies were performed with statistical liquid‐crystalline side‐group copolymers having different concentrations of the dye, in a copolymer forming no mesophase and in a physical mixture of the dye in a liquid‐crystalline side‐group homopolymer. Two relaxation processes were found in the glassy state of these polymers, the faster one being distributed over a wide range of relaxation times ascribed mainly to reorientational relaxation of the dye as well as the glassy matrix. The second is a single exponential, ascribed to the relaxation of azobenzene back to its trans conformation. The two processes could be assigned through a control experiment using an irreversibly isomerizing dye. The results of a calculation of the angular dependence of azobenzene isomerization was compared with the experiment, in order to judge the influence of the anisotropic matrix on the relaxation process.
Solution properties of polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymers
Authors: Küçükyavuz Zühal
Published: April 2003

The conformational behaviour of polystyrene‐block‐polybutadiene‐block‐polystyrenes, ABA‐type triblock copolymers, with 50 wt.‐% of A blocks were studied by light scattering, viscometric and osmometric methods over a wide range of molecular weight. Unperturbed dimensions were found directly by light scattering in the θ solvent methyl isobutyl ketone and also estimated by extrapolation methods from intrinsic viscosity and osmometric results in toluene, a thermodynamically good solvent. Osmometric and viscometric results showed that the block copolymers form a Gaussian coil in toluene, whereas light scattering results indicated some segregation of blocks for a low‐molecular‐weight sample in the θ solvent.
Chemical synthesis and properties of tetrabutylphosphonium‐ion‐doped polyacetylene
Authors: Ignatious Francis , Mathis Claude
Published: April 2003

A direct method of introducing tetraalkylphosphonium ions into polyacetylene (PA) is described. The maximum doping levels achieved with reducing agents having various redox potentials were determined. The electrical and magnetic properties of resulting doped products were assessed. The thermal stability of this product was monitored by electrical conductivity measurements. An indirect ion‐exchange technique was devised to insert the phosphonium ion into PA. A similar method was found useful for the preparation of reduced β‐carotene, a soluble analogue of PA, containing tetraalkylphosphonium counterions. The stability of the resulting compound was also studied.
Coordination polymerization of lactides, 1. Structure determination of obtained polymers
Authors: Bero Maciej , Kasperczyk Janusz , Jedlinski Zbigniew J.
Published: April 2003

Racemic lactide was polymerized with various initiators containing Zn and Al, and the structures of the obtained polymers were determined by means of 13C NMR spectroscopy. The extent of transesterification reactions was calculated on the basis of the analysis of the methine carbon signal in the polymer 13C NMR spectra. Three groups of initiators can be distinguished in view of their influence on transesterification: ZnCl2 exhibits the strongest transesterification activity, ZnEt2 and ZnEt2/Al(OiPr)3 are among those of medium activity, and Al(acac)3 does not show transesterification activity at all.
Poly(Ether/Ester)s based on poly(tetramethylene terephthalate) and poly(ethylene glycol), 3. Effect of thermal treatment and drawing on the structure of the poly(ether/ester)s
Authors: Fakirov Stoyko , Gogeva Tanya
Published: April 2003

Annealed drawn and undrawn bristles of poly(ether/ester)s based on poly(tetramethylene terephthalate) (PTMT) and poly(ethylene glycol) PEG 1000 (in various ratios) are studied by means of small‐angle X‐ray scatering and differential scanning calorimetry (DSC). The samples with the lowest PTMT content (49 wt.‐% PTMT) show on abrupt increase of the scattering intensity and the long spacing with increasing annealing temperature Ta, this increase becoming less pronounced with increasing fraction of hard segment (PTMT). The DSC heating scans are characterized by a low‐temperature glass transition due to the soft polyether segments and a multiple melting behaviour at about 200°C due to the crystalline hard PTMT segments. The data suggest a dependence of the thermal behaviour on the chemical composition, annealing temperature, and orientation. The characteristics of the undrawn samples are similar to those of the homopolyester PTMT and the copolymers based on PTMT and poly(tetramethylene oxide). Evidence is found for an increase of phase separation with an increase of the annealing temperature. The formation of larger amorphous regions of PEG with increasing Ta determines the thermal and scattering behaviour observed.
Enlargement of the glass transition range in compatible polymer blends
Authors: Schneider Hans Adam , Cantow Hans‐Joachim , Wendland Christina , Leikauf Bernhard
Published: April 2003

Analysis of glass transition temperature (Tg) ranges for compatible polymer blends defined by differential thermal analysis traces for the onset temperature (Tg, i) and the final temperature (Tg, f) of the glass transition shows the well‐known increase in width when compared with the Tg ranges of the blend components. This enlargement of the Tg range is generally attributed to local composition fluctuations; from a comparison of the effects in blends of polystyrenes (PS/PS) of different molecular weights the influence of an increase of the ratio of weight‐ to number‐average molecular weights M̄w/M̄n, because of interactions between the blend components (hetero‐interactions) has to be considered, too. Poly(methyl vinyl ether) (PVME)/PS blends are characterized by a peculiar behaviour, the increase in the width of the Tg range being at least three‐fold larger than for all other blends studied. This is valid for all blends with a molecular weight of the PS component higher than 10000. Local incompatibilities suggested by enthalpy relaxation and by dynamic mechanical measurements may be responsible for the observed unusual enlargement of the Tg range in the blends with 50–75 wt.‐% PS.
Functional monomers and polymers, 192. Synthesis of N‐nitrophenylchitosan derivatives and their electrochemical properties
Authors: Ohnishi Noriaki , Kondo Koichi , Takemoto Kiichi
Published: April 2003

N ‐ Nitrophenylchitosan derivatives were prepared by the reaction of chitosan hydrochloride with 1 ‐ fluoro ‐ 4‐nitrobenzene, 1‐fluoro‐2,4‐dinitrobenzene and p‐nitrobenzaldehyde. The 2,4‐dinitrophenyl derivative, which is the only product soluble in dimethyl sulfoxide and dimethylformamide, was analyzed by two‐dimensional NMR spectroscopy. Its solution in dimethylformamide exhibits a remarkable change in color from yellow to red upon electroreduction, and the film cast from dimethylformamide solution shows similar electrochromic properties.
Computer simulation of the dynamics of branched polymers
Authors: Romantsova Irina , Taran Yurii
Published: April 2003

The dynamics of an isolated symmetrical four‐branched star‐shaped macromolecule is simulated for random (RW) and self‐avoiding walks (SAW) by a Monte Carlo algoritham. The motion of branching points is realized on a body‐centred cubic lattice by elementary moves, including 4–6 bonds of the chain. The average dimensions of the chain, the autocorrelation functions, and the translational diffusion are investigated. The algoritham for RW displays Rouse behaviour. Scaling exponents are found for SAW.
Evaluation of the equilibrium melting temperature and structure analysis of poly(ethylene oxide)/poly(methyl methacrylate) blends
Authors: Cimmino Sossio , Di Pace Emilia , Martuscelli Ezio , Silvestre Clara
Published: April 2003

By using optical microscopy, small‐angle X‐ray scattering and differential scanning calorimetry, the melting behaviour and the structural parameters of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends are determined. The equation that relates the observed melting temperature, Tm′, to the lamellar thickness is used for the determination of the equilibrium melting temperature, Tm. In the case of blends a small depression in the equilibrium melting point is observed. The depression is dependent on composition. the interaction parameter obtained from the melting point degression, by using the Nishi and Wang equation, was found to be = −0,29. The superstructural parameters are dependent on blend composition, under cooling and sample preparation.
Graft copolymers, 2. The application of group‐transfer polymerisation to the synthesis of graft copolymers
Authors: Jenkins Aubrey D. , Tsartolia Eugenia , Walton David R. M. , Horská‐Jenkins Jitka , Kratochvíl Pavel , Stejskal Jaroslav
Published: April 2003

A copolymer, containing a minor proportion of residues derived from a special monomer with particular structural features, has been synthesised and used in a subsequent grafting step in which functional groups belonging to the special monomer residues were converted into initiating centres from which grafts were grown by means of “group‐transfer” polymerisation. It is shown that this technique constitutes a satisfactory method for the synthesis of graft copolymers (or branched, i. e. comb‐like, homopolymers) free from linear homopolymer, and the procedure is applied to a specific system in which the principal backbone monomer is styrene, the special backbone monomer component is (2‐isobutyryloxy)ethyl methacrylate, and the grafting monomer is methyl methacrylate.
13C NMR analysis of poly[(m‐phenylene terephthalate)‐co‐oxybenzoate]s: Main‐chain and end‐group resonance assignments and sequence distribution
Authors: Komber Hartmut , Böhme Frank , Pospiech Doris , Rätzsch Manfred
Published: April 2003

Samples of poly[(m‐phenylene terephthalate)‐co‐oxybenzoate] with different compositions were analyzed by 13C NMR spectroscopy. Diad and triad signals could be identified and assigned. Furthermore, the signals of acetoxy, carboxy and hydroxy end‐groups were assigned. The analysis of NMR substituent effects confirms the assignment. Comparison of the calculated statistical with the experimentally determined diad and triad contents shows a slight tendency for the formation of oxybenzoate blocks in the polymer chain.
Monte Carlo simulation of tetrahedral chains, 3. Star‐shaped polymers by pivot algorithm
Authors: Zifferer Gerhard
Published: April 2003

By use of the pivot algorithum, stars with F = 3–12 arms of length n, nF = 480, and linear chains (F = 2) are generated on a tetrahedral lattice in order to test the suitability of this algorithm for star‐shaped polymers. A new configuration is obtained by rotating that part of an arm which contains the chain end around a randomly selected bond by ±120°. If no double occupancies occur, the new configuration is accepted. Otherwise, the old one is restored. The (average) acceptance fraction decreases only slightly with increasing number of arms. The probability of obtaining a new self‐avoiding configuration by a move of an arm around a bond near the centre of the star is significantly higher than the probability for a successful combination of star with F‐1 arms with a further arm. The statistical error of global properties of stars with the same total number of segments is nearly independent of the number of arms, because an increase of the autocorrelation times is approximately compensated by a decrease of mean square deviations. In principle, comparison of the data with theoretical predictions yields the same results as found for other lattice models.