bluuebunny/crossref_metadata_2025 huggingface dataset:
Anionic living polymerization of β‐propiolactone initiated with crowned potassium methacrylate: Macromonomers and their copolymers with butyl acrylate
Authors: Sosnowski Stanisław , Stomkowski Stanisław , Penczek Stanisław , Arkhipovich Georgii N. , Kazanskii Konstantin S.
Published: April 2003

The polymerization of β‐propiolactone (βPL) with crowned K+ counterion has been shown previously to be a living process. This behaviour was used to prepare macromonomers of poly(βPL) with the methacryloyl reactive group. Poly(βPL) is known to be a crystalline polymer; thus, copolymers of poly(βPL) macromonomers with butyl acrylate gave graft copolymers with properties stemming from this ability. Selected mechanical properties of the copolymers are close to those of acrylic rubbers reinforced with fillers.
Synthesis of unsaturated oligoesters containing maleoyl and/or fumaroyl units via the intermediate isourea salts
Authors: Joos Betina , Schmidts Beate , Funke Werner
Published: April 2003

Unsaturated oligoesters with carboxylic acid end groups were prepared from maleic and/or fumaric acid and 1,6‐hexanediol. The oligomers with molar masses between 700 and 1 100 were synthesized from smaller ester units via the corresponding isoureas, applying the carbodiimide method. Three oligoesters with uniform molar masses and chemical structures were obtained in excellent yields. They were characterized by gel permeation chromatography, infrared spectroscopic analysis, elemental analysis and by determination of their acid numbers.
Three‐phase carboxylation reactions of poly(chloromethylstyrene) beads with sodium nitrite
Authors: Howang K. T. , Takahashi M. , Iwamoto K. , Senō M.
Published: April 2003

The formation of carboxylic acid groups (carboxyl + ester groups) was found in a threephase reaction of crosslinked poly(chloromethylstyrene) beads with an excess amount of sodium nitrite in immiscible solvents of benzene and water with tetrabutylammonium bromide as a phase transfer catalyst (PTC), and the dependence of carboxylic acid yield on the experimental conditions was studied. The product contains hydroxyl groups and ester bonds besides carboxyl groups. It was tentatively considered that the carboxyl groups are produced by direct oxidation of chloromethylstyrene groups by nitrous anions. Nitrous anions do not only act as a nucleophile but also as an oxidative reagent in this case.
Compatibilité de polymères porteurs de groupements amides tertiaires avec le poly(difluoro‐1,1 éthylène). Etude par enthalpimétrie différentielle
Authors: Galin Monique
Published: April 2003

The miscibility of poly(1,1‐difluoroethylene) (1) with poly(N‐vinyl‐2‐pyrrolidone) poly(N‐methyl‐N‐vinylacetamide) and poly(N,N‐dimethylacrylamide), containingtert‐amido groups, was investigated by differential scanning calorimetry. Amorphous homogeneous blends were obtained whenever the weight fractions of polymer1is less than 0,7. The dependence of the single glass transition temperature (Tg) versus composition may be readily analyzed either through the Gordon‐Taylor equation (high values of thekparameter, suggesting strong specific interactions between the homopolymers) or by means of the Couchman relation (no adjustable parameter). The broadening of the glass transition range and the variation of the increment of specific heat atTgfor the blends are discussed.
Electrochemistry of thin polypyrrole films
Authors: Wernet Wolfgang , Wegner Gerhard
Published: April 2003

Thin polypyrrole (PP) films with octanesulfonate, dodecylsulfate and polystyrenesulfonate counterions were electrochemically switched between the conducting oxidized and the insulating neutral state in various electrolytes. In propionitrile under rigorous exclusion of oxygen and water PP can be cycled more than a thousand times without an appreciable decrease in electrochemical capacity. In an aqueous medium this process becomes irreversible after less than a hundred scans, the effect being strongly influenced by the pH of the electrolyte. Furthermore a pronounced dependence of the available charge upon the time (t5) between subsequent scans is found. It is known that treatment of PP films by a base leads to a remarkable decrease in conductivity. A mechanism which explains the loss of conductivity is proposed, in addition the possible occurrences of irreversible chemical changes as side reactions during electrochemical cycling is discussed.
A study on the states of ethyl benzoate and TiCl4 in MgCl2‐supported high‐yield catalysts
Authors: Terano Minoru , Kataoka Takuo , Keii Tominaga
Published: April 2003

The states of ethyl benzoate (EB) and TiCl4 in the primary types of MgCl2‐supported catalysts were studied by thermogravimetry/differential thermal analysis (TG‐DTA) in combination with other methods. The results obtained by all experiments indicate that TiCl4 and EB in the MgCl2‐supported high‐yield catalysts interact only with MgCl2, leaving no vacant sites on TiCl4.
Synthesis and characterization of biaxial nematic side chain polymers with laterally attached mesogenic groups
Authors: Hessel Friedrich , Herr Rolf‐Peter , Finkelmann Heino
Published: April 2003

The synthesis and characterization of liquid crystalline side chain polymers with mesogenic groups laterally attached to the polymer main chain are described. By variation of the terminal group, mesogenic moiety or spacer length, a change in the glass transition temperature, the nematic to isotropic transformation temperature and the stability of the nematic phase can be achieved. With increasing length of terminal groups, a distinct odd‐even effect of the nematic to isotropic phase transformation temperature and also a strong decrease of the glass transition temperature is observed. Macroscopic homeotropic alignment can be achieved in an electric or magnetic field. Conoscopic investigations show optical biaxial behavior of the nematic phase. A chiral nematic copolymer is the first example of a thermotropic biaxial cholesteric phase.
Synthese und Komplexierungseigenschaften von monomeren und polymeren 5‐Methacryloylaminosalicylsäure‐Derivaten
Authors: Lange Kai , Ritter Helmut
Published: April 2003

The synthesis of monomeric and polymeric 5‐methacryloylaminosalicylic acid derivatives is described. The interaction of these ligands with Fe(III), Ti (IV) and Ca(II) ions was investigated by photometric, conductometric and viscosimetric measurements.
Polyethers for biomedical applications. Polymerization of propylene oxide by organozinc/organotin catalysts
Authors: Bots Jan Gert , van der Does Leen , Bantjes Adriaan , Boersma Jaap
Published: April 2003

The polymerization of propylene oxide to obtain a high‐molecular‐weight polymer with an atactic structure required for the application as artificial blood vessels was investigated using combinations of organozinc and organotin compounds as catalyst. The composition of the most active catalyst, resulting from the reaction of diphenyltin sulfide with bis(3‐dimethyl‐aminopropyl)zinc, was found to be R(C6H5)2Sn(SZn)2R with R = (CH2)3N(CH3)2. Using this catalyst, an anionic coordination polymerization was observed with neither stereoselectivity nor living type or cationic features. At low catalyst concentration (0,03 mol‐% Zn) a high‐molecular‐weight poly(propylene oxide) (PPOX) was obtained in 80–90% yield (Mw = 500000; 40% isotactic). Lowering of the catalyst concentration and increasing the polymerization temperature changed the kinetics and the stereochemistry of the polymerization leading to polymers of lower molecular weight and to a decrease in the isotactic PPOX fraction to 20%, probably due to an association of the catalytic species.
Polymerization of 2‐diethylamino‐1,3,2‐dioxaphosphorinane, 2. Kinetics
Authors: Kałużyński Krzysztof , Penczek Stanisław
Published: April 2003

Kinetic studies of the anionic polymerization of 2‐diethylamino‐1,3,2‐dioxaphosphorinane were performed in THF solution with (CH3)3SiO−K+ as initiator at temperatures close to r.t. Initiation involves nucleophilic attack of the anion on P atom in the monomer molecule. Breaking of the PO bond leads to an alcoholate anion as the growing species. Polymerization was shown to proceed via macroion‐pairs and to be nearly living; e.g. at r.t. for every 250 propagations there is one termination. Rate constant of propagation k = 3,4 ± 0,31·mol−1·s−1 at 25°C, ΔH = 13,3 kcal·mol−1 and ΔS = −32,2 cal·mol−1·K−1. The ratio k/k was determined by solving a kinetic scheme involving propagation and termination. It was shown that termination consists in the alcoholate anion attack on P in either polymer or monomer molecule with expulsion of (C2H5)2N− anion and formation of a PO bond. The dialkylamide anions cannot reinitiate polymerization. In solving the kinetic scheme it was assumed that termination involving both polymer and monomer proceeds with rate constants equal to each other.
Photo‐oxydation du polystyrène à grandes longueurs d'onde (λ > 300 nm) et à 60°c
Authors: Khalil Zahi , Michaille Sylvie , Lemaire Jacques
Published: April 2003

An analytical and kinetic study of the photo‐oxidation of polystyrene in the solid state carried out at long wavelengths (λ > 300 nm) is reported. The concentration of the primary hydroperoxides has been determined throughout photo‐oxidation using chemical titrations. IR and FTIR spectrometry were used to analyze the hydroxylated and carbonylated intermediate groups formed. Hydrogen‐bonded alcohols (3540 cm−1), aromatic ketones (1690 cm−1), and unsaturated esters (1725 cm−1) were observed. The UV‐absorbing products formed in the photo‐oxidation enter a photothermal equilibrium; this allows to select only two structures to account for the yellowing of photooxidized polystyrene.
Poly(3‐dodecyl‐2,5‐thiophenediyl), a soluble and conducting polythiophene
Authors: Sato Masa‐aki , Tanaka Susumu , Kaeriyama Kyoji
Published: April 2003

Poly(3‐dodecyl‐2,5‐thiophenediyl)(PDDT) films were prepared by means of electrochemical polymerization of 3‐dodecylthiophene. PDDT is soluble in benzene, chloroform and tetrahydronaphthalene, and oxidized PDDT is soluble in tetrahydronaphthalene. The degree of polymerization was found to be 90 and the conductivity of an as‐grown film, containing hexafluorophosphate anion, is 67 S/cm. While the cyclic voltammograms of an as‐grown film have two anodic peaks and two cathodic peaks, those of a film cast from an oxidized polymer solution has one anodic peak and one cathodic peak. Two peaks would correspond to two conjugation length. Oxidized PDDT is partly soluble in chloroform, retaining oxidized states. UV‐near infrared spectra in solution were compared with those in a solid film. The energy of the interband transition was found to be much higher in the solution than in the film. The results indicate a rigid oxidized part and a flexible neutral part in the polymer chain. The concentration dependence of the spectra indicates that oxidized PDDT does not aggregate in solution.
Retardation of the TiCl3·1/3 AlCl3/AlEt2Cl catalyzed propylene polymerization by allene and its relevance to the determination of the number of active centers
Authors: Kratochvíla Jan , Mejzlík Jiří
Published: April 2003

The retardation of the TiCl3/AlEt2Cl catalyzed propylene polymerization by allene was studied. On the basis of the results, a mechanism of the competitive chemisorption on active centers was proposed. A non‐linear dependence of the polymerization rate on the amount of allene consumed can be described in terms of the existence of two types of active centers, their numbers being 2 and 20 mmol·mol, respectively, differing very substantially in the adsorption coefficients. Copolymerization of propylene with allene was investigated, using the above catalytic system. Assuming identical active centers, the following copolymerization parameters were obtained: r1 = 0,66 ± 0,66 and r2 = 40 ± 30. Based on these results, the consumption of allene by copolymerization during the retardation of propylene polymerization was described in quantitative terms.
Metathesis degradation of partially phenylated 1,4‐polybutadiene
Authors: Stelzer Franz , Hummel Klaus , Graimann Christof , Hobisch Josefine , Martl Michael G.
Published: April 2003

1,4‐Polybutadiene was partially phenylated in allyl position by bromination with N‐bromosuccinimide and subsequent Grignard‐Wurtz reaction with phenylmagnesium bromide. Substitution was to a certain degree coupled with double bond shift. The polymer structure was investigated via metathesis degradation with (E)‐4‐octene. The degradation products were identified by means of a GC/MS system and determined by GC. Cases of isomerism of products with one phenyl group were investigated. A metathesis product with two phenyl groups in one constitutional unit was found. A distribution function, based on a statistical scission of the macromolecules, was used for evaluations at different metathesis reaction times. Proofs of the reduced reactivity of CC double bonds in the neighbourhood of substituents were received. The yields of the different constitutional units in metathesis products were determined. These were compared with the results of computer simulations in a simplified model. The validity of computer simulations was thereby confirmed.
Synthesis of high‐molecular‐weight poly(L‐lactide) initiated with tin 2‐ethylhexanoate
Authors: Leenslag Jan W. , Pennings Albert J.
Published: April 2003

The bulk polymerization of L,L‐dilactide was studied as a function of polymerization temperature (Tp), time and concentration of catalyst (tin 2‐ethylhexanoate). Poly(L‐lactide) (PLLA), with the highest value of intrinsic viscosity ([η] = 13 dl · g−1; M̄v ≈ 1 · 106) and heat of fusion (ΔHm = 64,7 J · g−1), was synthesized at a low catalyst concentration (0,015 wt.‐%) and at the lowest Tp studied (100°C), just above the melting point of L,L‐dilactide (98°C). The ceiling temperature of PLLA was found to be 275°C, as deduced from an M̄v max. − Tp curve. The M̄w/M̄n ratios of as‐polymerized PLLA samples ranged from 2 to 3. Fractions of PLLA with M̄v max. were already present at 50% conversion. The experimental results support a proposed nonionic insertion polymerization mechanism. Polymerization at 100–140°C resulted in early crystallization of PLLA leading to a rather untangled polymer and microporous (pores up to 100 nm) sample texture.
Effect of bound water on structural change of regenerated cellulose
Authors: Hatakeyama Tatsuko , Ikeda Yoshimitsu , Hatakeyama Hyoe
Published: April 2003

Phase transition of water sorbed in regenerated cellulose (II), for water contents ranging from 0 to 1,0 (water/dry cellulose, g/g), was investigated by differential scanning calorimetry (DSC). It was found that the amount of water bound to each glucose unit is ca. 3 mol considering that water diffuses only into the amorphous region of cellulose. The increase of this amount by adding excess water to cellulose suggests that the amorphous region of cellulose II increases in the presence of water. The transient state, at a water content ranging from 0,4 to 0,6, where the intermolecular distance expands, is reflected in an intermediate crystallization at a temperature between the crystallization of free water and freezing bound water. Mechanical properties of cellulose II under moist conditions were related to the results obtained by DSC. Further, the strength at break of cellulose II was compared with that of natural cellulose (I). The strength of cellulose II decreases in presence of bound water, whereas that of cellulose I increases. Based on the comparison of the results of DSC and mechanical properties of cellulose I and II, the difference is attributed to the structural change of the amorphous region when water molecules are bound to the hydroxyl groups of cellulose. The defect or internal strain of the amorphous region of cellulose I decreases and the molecular chain is transformed into a more regular arrangement when water molecules break hydrogen bonds. On the other hand, the amorphous chain of cellulose II takes a more released and expanded arrangement in presence of water molecules which break hydrogen bonds in the crystalline region of cellulose II. The decrease of crystallinity was observed by x‐ray diffraction.
Synthesis and thermodynamic studies on the protonation of a new polymeric amino diacid
Authors: Fini Adamo , Casolaro Mario , Nocentini Mila , Barbucci Rolando , Laus Michele
Published: April 2003

A linear poly(amido‐amine) carrying a malonic acid moiety in the side chain of the repeating unit was synthesized and characterized. Its behaviour in aqueous solution was investigated by potentiometric, viscometric and calorimetric techniques. The basicity constant relative to the tertiary nitrogen atom decreases linearly by increasing the overall degree of protonation, while the tendency of each carboxylate ion to accept a proton is influenced by the presence of the neighbouring negative charge. The change of the basicity constants with the degree of protonation is due to entropic terms leading to energetics of protonation independent of the degree of protonation.
Synthesis and tacticity characterization of a novel series of liquid crystalline side chain polymers with oligo(ethylene oxide) spacers
Authors: Duran Randolph , Gramain Philippe
Published: April 2003

A novel series of liquid crystalline side chain polymers containing oligo(ethylene oxide) spacers was synthesized and characterized. These included acrylates, methacrylates, and methacrylate copolymers. Although all polymers were polymerized free radically, NMR tacticity studies showed a systematic variation of the observed tacticity of the methacrylate series, the isotactic content decreasing with increasing spacer length. The data indicate that the spacer length and mesogenic group play a role in determining microstructure during polymerization.
Structure and amounts of counter ions in polypyrrole films prepared from aqueous solutions of sodium tosylate
Authors: Shen Yueqiang , Qiu Jinjin , Qian Renyuan , Carneiro Kim
Published: April 2003

A series of conducting polypyrrole films was prepared from aqueous TsONa solution of different concentrations, and investigated by means of elemental analyses and scanning electron microscopy. The results show that the different concentrations of the supporting electrolyte TsONa do not only cause different amounts of counter ions in the film, but also cause a different structure and morphology of the film.
The synthesis of poly(allylamine) containing covalently bound cyclodextrin and its catalytic effect in the hydrolysis of phenyl esters
Authors: Seo Toshihiro , Kajihara Taketoshi , Iijima Toshiro
Published: April 2003

A poly(allylamine) {poly[1‐(aminomethyl)ethylene]} (2) containing covalently bound β‐cyclodextrin (CD) residues (3) was synthesized. The inclusion ability of CD was enhanced in this polymer 3. A pronounced catalytic acceleration of the hydrolysis of p‐ and m‐nitrophenyl acetate by 3 as compared with that of 2 indicates the cooperative effect of CD and amino groups on the polymer chains.
The optical‐configuration parameter for ethene‐propene copolymers
Authors: Saiz Enrique , Mark J. E.
Published: April 2003

Rotational isomeric state theory is used to predict values of the optical‐configuration parameter Δa for ethene‐propene copolymers as a function of chemical composition, chemical sequence distribution, and stereochemical structure of the propylene sequences. The calculations are based on information available for ethene and propene homopolymers, and on the model used to interpret the unperturbed dimensions of these copolymers. Values of Δa were generally found to decrease significantly with increase in the fraction of propylene units, but to be relatively insensitive to chemical sequence distribution and stereochemical structure. The extent of their agreement with experiment is consistent with comparisons previously reported for a variety of homopolymers. It is intermediate to the poor agreement generally obtained for symmetric chains (such as polyethylene) and the satisfactory agreement generally obtained for asymmetric chains (such as polypropylene).
Rheological and thermal properties of carrageenan gels. Effect of sulfate content
Authors: Watase Mineo , Nishinari Katsuyoshi
Published: April 2003

Dynamic viscoelasticity and differential scanning calorimetry (DSC) measurements were carried out in order to examine the effect of sulfate content on the gelling mechanism of concentrated kappa‐ and iota‐carrageenan solutions. Alkaline pre‐treatment was very effective to enhance the gelling ability of kappa‐carrageenan. The melting temperature of the gels and the temperature at which elastic modulus begins to decrease rapidly were shifted to higher temperatures with increasing concentration of gels. Elastic modulus increased with increasing concentration, while endothermic enthalpy showed a maximum at a certain concentration. The effect of thermal history on DSC behavior was also examined.
Molecular weight dependence of interaction parameter and demixing concentration in polymer‐polymer‐good solvent systems. comparison with theory
Authors: Kaddour Latifa Ould , Anasagasti Maria Soledad , Strazielle Claude
Published: April 2003

The dependence of the interaction parameter χAB between two unlike polymers A and B and of their demixing concentration cK on their molecular weight is investigated. The experiments were performed by means of light scattering (spinodal and “optical theta” conditions) on two polymer pairs: polydimethylsiloxane‐polystyrene and polydimethylsiloxane‐poly(methyl methacrylate) in various thermodynamically good solvents. The results are in agreement with the predictions of new scaling laws (χAB ∼ M−0,46 and cK ∼ M−0,63) derived from renormalization group calculations.
An unexpected mode of cationic oligomerization of 1‐vinyl‐4,5,6,7‐tetrahydroindole
Authors: Trofimov Boris Alexandrovich , Morozova Ludmila Vasil'evna , Sigalov Mark Vladimirovich , Mikhaleva Al'bina Ivanovna , Markova Marina Viktorovna
Published: April 2003

1‐Vinyl‐4,5,6,7‐tetrahydroindole in the presence of Brønsted acids (HCl, H2SO4, HOAc) and Lewis acids (BF3 · OEt2, FeCl3, TiCl3, SnCl4, SiCl4, Et3SiCl, Me2, PhMeSiCl2) undergoes an alternative oligomerization involving both the double bond and the α‐position of the pyrrole ring to form the dimer 1‐vinyl‐2‐[1‐(4,5,6,7‐tetrahydro‐1‐indolyl)ethyl]‐4,5,6,7‐tetrahydroindole in a yield up to 68% and oligomers of the same backbone, soluble (major product) and insoluble (minor product) in hot hexane, the latter being enriched by oxidized and hydrolyzed tetrahydroindole units. The molecular weights of the former oligomers were assessed from 1H NMR spectra to range from 1000 to 2000.
Synthesis of poly(ϵ‐caprolactone) macromonomers
Authors: Gnanou Yves , Rempp Paul
Published: April 2003

Macromonomers of poly(ϵ‐caprolactone) were synthesized according to a two‐step method. ω‐Hydroxypolycaprolactone was first obtained by protonic deactivation of the growing alkoxide site, under conditions such as to minimize the draw‐backs of anionic polymerization of ϵ‐caprolactone: slow initiation with respect to propagation, occurrence of reshuffling and backbiting reactions. In a second stage, the polymer was fitted with an endstanding unsaturation, according to methods derived from peptide chemistry. The macromonomers obtained were characterized accurately (control of MWD, functionalization).
Structural variations of DNA + Mn2+ complexes during helix‐coil transition
Authors: Sorokin Victor A. , Fedorov Vladimir F. , Leontiev Victor S. , Blagoi Yuri P. , Galkin Vladimir L.
Published: April 2003

The helix‐coil transition in Phage T2 DNA in the presence of 6,4 · 10−3 mol/l Mn2+ is studied using light scattering and UV spectroscopy. The transition range is about 0,5°C. Near the temperature of the end of melting Tf the molecular weight Mw and the radius of gyration Rz of the complex are observed to decrease to about one half. At a temperature 0,1–0,25°C higher than Tf, Mw and Rz pass through a minimum, which implies that aggregation is preceded by unwinding of DNA strands. Thus, rise in temperature rather than Mn2+ ‐induced aggregation causes DNA + Mn2+ melting.
Critical chain lengths in polystyrene bulk diffusion
Authors: Antonietti Markus , Fölsch Karl Josef , Sillescu Hans
Published: April 2003

Diffusion coefficients D of singly and doubly end‐labeled polystyrenes (PS) with molecular weights in the range 6500 ≤ M ≤ 75400 were measured in a PS matrix of molecular weight M′ = 111000, and in matrices with M′ = M. At 212°C, we find no influence of the label. In a power‐law description D = D0 · M−α · M′−β we find α = 2,0 for M′ = 111000 and α + β = 2,4 for M = M′. The crossover to Rouse‐like behavior for short‐M chains is at Me ≈ 18000 for the former (high M′), and at Mc ≈ 33000 in the latter (M′ = M) case. At 185°C, we find a more complex scaling behavior and different D values for singly and doubly labeled PS.
A fourier transform infrared and nuclear magnetic resonance study of cyclized natural rubber
Authors: Patterson Dwight Juan , Koenig Jack L.
Published: April 2003

Fourier transform infrared (FTIR), 1H NMR, and 13C NMR have been used to characterize the structure of natural rubber cyclized with p‐toluenesulfonic acid. The samples studied were only partially cyclized. The cyclized portions contained both mobile and rigid domains. Crosslinking occurred during the cyclization reaction. The cyclized samples showed a distribution of functionalities including some oxidation products. All three types of olefinic segmented end groups were formed during cyclization (di‐, tri‐, and tetrasubstituted olefins). The loss of the exocyclic species leads to the formation of cross‐linked networks.
Self‐diffusion coefficient of flexible‐chain polymers in solution and in the melt
Authors: Budtov Vladilen P.
Published: April 2003

A theory was developed for predicting the self‐diffusion coefficients Dp of macromolecules and of oligomers in solution and in the melt. For moderate‐concentration ranges account was taken of decreasing intramolecular hydrodynamic interaction with increasing concentration. In the high‐concentration range the scaling theory was used. The dependence of Dp on concentration, molecular weight, and quality of the solvent was described by a common relationship as a function of √c[η] with mass concentration c and intrinsic viscosity [η]. If the dependence is considered in the form Dp ∝ cβ, then the value of the exponent β varies between 0 and 2. If the dependence of the local viscosity is taken into account, then β is greater than 2. An analysis of the relationships of Dp for oligomers and polymers in melts was also conducted. The theoretical results obtained describe quantitatively the available experimental data. These results were used for the interpretation of the decreasing decay rate of macroradicals with increasing conversion (gel effect).
Zur theoretischen beschreibung der kinetik der radikalischen terpolymerisation von styrol mit N‐vinyl‐2‐pyrrolidon und methylmethacrylat anhand des klassischen copolymerisationsmodells
Authors: Quella Ferdinand , Czerwinski Wojciech K. , Braun Dietrich
Published: April 2003

The polymerization rate of the ternary monomer system, styrene, N‐vinyl‐2‐pyrrolidone, and methyl methacrylate, was investigated in bulk at 60°C with AIBN as initiator. The results were interpreted by means of the well known classical reaction model and a newly derived simplified reaction model. The classical rate equation describes the reaction rate correctly in general, however, supplementary assumptions are needed for this special monomer system. The simplified reaction model is useful to estimate the terpolymerization rate, if initiation rates for the monomer mixtures are not known.
Addition of the 1‐cyano‐1‐methylethyl radical to α‐methylstyrene
Authors: Behari Kunj , Bevington John C. , Huckerby Thomas N.
Published: April 2003

1‐Cyano‐1‐methylethyl end‐groups in copolymers of α‐methylstyrene (MST) with methyl methacrylate (MMA) and with styrene (STY) have been examined by 13C NMR; the end‐groups have been derived from initiators suitably enriched with carbon‐13. It has been shown that at 60°C MST closely resembles STY in reactivity towards the 1‐cyano‐1‐methylethyl radical. MST is 1,89 times as reactive as MMA towards the radical at 40°C; the corresponding factors at 60 and 100°C are 1,69 and 1,55, respectively. There is no evidence for reversibility in the reaction of MST with the 1‐cyano‐1‐methylethyl radical.
Polymer strength and chain conformation
Authors: He Tianbai
Published: April 2003

It is found that the expected maximum strength of polymers is not proportional to the number of polymer chains per unit area. Under uniaxial stressing only part of polymer chains, i.e., overstressed chains, contribute to the strength of the polymer. The number of overstressed chains obtained here for some polymers is consistent with the results of electron paramagnetic resonance and stress‐Fourier‐transform IR measurements: (a) Polymers with all‐trans conformation of their chains have more overstressed chains than those with helix conformation; (b) in the case of polymers with helix conformation, those with smaller side groups have more overstressed chains. Under uniaxial stress, the polymer chains change their conformation from gauche to trans which results in a relief of stress. Polymer with helix conformation thus have less overstressed chains and, hence, lower strength than polymers with all‐trans conformation.
Polymer‐bound derivatives of sarcolysin and their antitumour activity against mouse and human leukaemia in vitro
Authors: Ulbrich Karel , Zacharieva Ekaterina I. , Kopeček Jindřich , Hume Isabella C. , Duncan Ruth
Published: April 2003

A series of N‐(2‐hydroxypropyl)methacrylamide (HPMA) copolymers containing different oligopeptide side‐chains terminated in an alkylating anticancer agent‐sarcolysin isopropyl ester (SL‐OiP) and occasionally fucosylamine were synthetized. In the first step reactive polymeric precursors were prepared by radical precipitation copolymerization of HPMA with p‐nitrophenyl esters of N‐methacryloylated dipeptides (Gly‐Phe or Gly‐Leu). In the second step the former were aminolyzed with a dipeptide or amino acid derivatives of SL‐OiP, thus forming tripeptide or tetrapeptide side‐chains terminated in SL‐OiP. Two of the polymers synthetized contained also fucosylamine as the terminal moiety, which was introduced as a targeting moiety, able to interact with fucose‐specific membrane receptors of mouse leukaemia L 1210 cells. These polymers were synthetized by consecutive aminolysis of reactive polymeric precursors with fucosylamine and SL‐OiP derivatives. To test the influence of the oligopeptide side‐chain structure on the rate of drug release, the polymers synthetized were incubated with a mixture of lysosomal enzymes isolated from rat liver (tritosomes) and with cathepsin B. The relationship between the structure of polymer bound anticancer drugs and their biological activity was determined in vitro by their effect on the growth of mouse leukaemia L 1210 cells and human lymphoblastoid leukaemia (CCRF) cells. The results demonstrate the potential of these compounds as new types of targetable anticancer agents.
Enthalpy of polymerisation of 7‐oxabicyclo[4.1.0]heptane
Authors: Andruzzi Fulvio , Shaofeng Li , Pilcher Geoffrey , Heatley Frank
Published: April 2003

The enthalpies of combustion in oxygen at 298, 15 K of 7‐oxabicyclo[4.1.0]heptane, ΔH(1) = −3 624,9 ± 0,6 kJ·mol−1, and of poly(oxy‐1,2‐cyclohexylene), ΔH(am) = −3528,2 ± 1,4 kJ · mol−1 were measured by high‐precision bomb calorimetry. The enthalpy of polymerisation was derived, ΔH(1→am) = −96,7 ± 1,5 kJ·mol−1. Polymer samples from three separate preparations were found to be indistinguishable in their enthalpies of combustion and in their 13C NMR spectra.
Spectral simulation and characterization of polymers from ethene and propene by 13C NMR
Authors: Cheng H. N. , Bennett Mark A.
Published: April 2003

A general treatment is devised for the 13C NMR spectral analysis of copolymers involving ethene and propene. The basis of the method is the computerized “synthetic approach” proposed earlier (Anal. Chem.) 56, 2320 (1984) and entails the use of first‐order Markovian statistics, Monte Carlo polymer chain generation, spectral prediction, and spectral simulation. By this means, copolymer and homopolymer spectra of increasing complexity are readily simulated. The method is shown to accommodate all structural types (viz. stereosequences, regiosequences, and polymer chain ends) and provides good results for atactic poly(propylene), irregular poly(propylene), isotactic ethene/propene copolymers, ethene/propene rubbers, and ethene/propene oils.
Thermodynamics of random copolymer mixtures
Authors: Panayiotou Constantinos G.
Published: April 2003

The lattice‐fluid theory of polymer solutions, previously applied to homopolymer‐solvent and homopolymer‐homopolymer mixtures, is now extended to random copolymer mixtures. A generalized, though simple, formalism is presented which is valid for binary copolymer mixtures, each copolymer having any number of different monomeric units (groups). Mixtures of a homopolymer with a random copolymer are treated as a special subcase. Particular emphasis is given to the phase stability of copolymer mixtures. Equations for the spinodal and the critical point are presented. The model is applied satisfactorily to various cases which attracted special attention in recent studies on the miscibility of copolymer mixtures.
Solid state and solution characterization of caprolactam cyclic dimer, a by‐product in the synthesis of nylon 6
Authors: Di Silvestro Giuseppe , Sozzani Piero , Brückner Sergio , Malpezzi Luciana , Guaita Cesare
Published: April 2003

The dimer of ϵ‐caprolactam (1,8‐diazacyclotetradecan‐2,9‐dione), an impurity always present in industrial nylon 6, was characterized by mass spectrometry and solution 13C NMR analysis. DSC and X‐ray diffraction lead to the complete description of the behavior of two crystalline phases: the one stable at room temperature and showing a transition to the other form at 244°C; the second one, more symmetrical, melting at 347°C and slowly converting to the first one at temperatures below 200°C. Both structures are stabilized by intermolecular hydrogen bonds, and the transition is due to conformational changes (from G+TTG− to G+G+TG+ on the aliphatic sequence and from eclipsed to ≈90° on the NCH2 bonds) which can be taken into account in the discussion about the tight chain folding of nylon 6.
Thermal crosslinking of styrene/p‐methylstyrene copolymers
Authors: Schröder Ulrich K. O.
Published: April 2003

Thermal crosslinking of polydisperse styrene/p‐methylstyrene copolymers with compositions of between 0 and 100 mol‐% of styrene and weight‐average molecular weights of about 300000 was investigated under oxygen‐free conditions at 260°C and 275°C. At these temperatures the formation of oligomers was negligible. The reaction products were analysed by gel permeation chromatography and by swelling experiments. Two competing reactions — degradation and crosslinking — were found which occur to an extent proportional to copolymer composition. By comparing the properties of the treated copolymer samples—molecular weights, amount and characteristics of the gel—with the properties of pure poly(p‐methylstyrene) samples degraded at 275°C it can be concluded that samples with 83 mol‐% and 79 mol‐% of styrene treated at 275°C and 260°C, respectively, should remain unchanged with respect to molecular weight and composition, because degradation and crosslinking compensate each other. In the samples containing less styrene crosslinking predominates. The ratio of the reaction rates determined experimentally agrees well with the value calculated from the reaction rates of the homopolymers given in the literature. A simple radical‐chain mechanism is proposed that explains the experimental results.
Stereoelective polymerization of propylene oxide with a chiral aluminium alkoxide initiator
Authors: Haubenstock Howard , Panchalingam Vaithilingam , Odian George
Published: April 2003

The polymerization of propylene oxide (PO) was studied with an initiator prepared by the reaction of (R)‐(−)‐3,3‐dimethyl‐1,2‐butanediol (1) with aluminium hydride. When mixed with zinc chloride in a 1:1 mole ratio, the initiator was found to be highly reactive and also stereoelective in the polymerization of PO, preferentially incorporating (R)‐(+)‐PO into the polymer chain. Analysis of the polymer structure by 13C NMR spectroscopy showed that chlorine, hydroxyl and alkoxy end groups, derived from the initiator, were present. Fractionation of poly(propylene oxide) (PPO) in acetone at −30°Cgave about 10% insoluble PPO, shown to be isotactic by 13C NMR. The soluble, largely atactic fraction contained irregular head‐to‐head (h,h) and tail‐to‐tail (t,t) structures. In the absence of coinitiator zinc chloride the PPO product was completely soluble in acetone at −30°Cand contained a greater proportion of irregular h,h and t,t structure.
Polyesters prepared by polycondensation in the presence of carbodiimides, 1. Preparation of polyesters from aliphatic dicarboxylic acids and diols under mild conditions
Authors: Panayotov Ivan M. , Belcheva Nadya , Tsvetanov Christo
Published: April 2003

The possibility of the preparation of aliphatic polyesters from dicarboxylic acids and diols by polycondensation in the presence of carbodimides under mild conditions was investigated. The following three possible routes were checked: the polycondensation of dicarboxylic acids with diols in the presence of 4‐dimethylaminopyridine, the polycondensation of dicarboxylic acids with diisourea derivatives and the polycondensation in the presence of pyridine and p‐toluenesulfonic acid. The last method was found to give polyesters with high molecular weights in good yields. This carbodiimide method can be utilized in the synthesis of biodegradable and surface active aliphatic polyesters.
Water‐insoluble dextrans by grafting, 3. Reaction of dextran with butyl isocyanate. Chemical hydrolysis
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Martínez Rafael
Published: April 2003

The modification reaction of dextran with butyl isocyanate using 1,4‐diaza[2.2.2]bicyclooctane as catalyst was studied. 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 the concentrations of polymer, butyl isocyanate and catalyst was found. The activation energy was found to be 38,5 kJ/mol (9,2 kcal/mol). The homogeneous hydrolysis in alkaline medium was found to be first order with respect to both the base and the butyl urethane concentrations. The activation energy, obtained for the base catalyzed homogeneous hydrolysis, was 83,7 kJ/mol (20,0 kcal/mol). The heterogeneous hydrolysis of a water insoluble modified dextran (degree of substitution = 0,72) showed that no hydrolysis takes place under the applied conditions.
Design of vinyl functional copolymers with main chain chirality through chemical modifications
Authors: Wulff Günter , Dhal Pradeep K.
Published: April 2003

Optically active poly(styrene‐co‐methyl methacrylate) and poly(styrene‐co‐methacrylonitrile) were obtained by means of asymmetric copolymerization of 3,4‐cyclohexylidene‐D‐mannitol‐1,2; 5,6‐bis{O‐[(4‐vinylphenyl)boronate]} (1) with methyl methacrylate and methacrylonitrile, respectively, removal of the D‐mannitol template and splitting off boric acid from the resulting copolymers. By polymer analogous reactions, various functional groups were introduced to obtain optically active functional vinyl copolymers. The polymers were characterized by spectral and other analytical methods.
Deuteron NMR study of molecular motion and phase behaviour in a polymer model membrane
Authors: Ebelhäuser Rainer , Spiess Hans Wolfgang
Published: April 2003

Pulsed 2H NMR was used to study the molecular mobility of a polymer model membrane. The polymerizable lipid analogue consists of a quaternary ammonium ion with two C18 alkyl chains and a methacryloyl moiety attached to the hydrophilic head group via an alkyl spacer. The bilayer spacing as obtained from small angle X‐ray scattering was found to be 3 nm in the lamellar Lβ gel phase of the monomer and 3,5 nm in the polymer indicating an interdigitated structure. The molecular mobility in both the monomer and the polymer below and above the phase transition Lβ → Lα was investigated by the NMR lineshapes and the transverse relaxation time T2 at five positions of the monomeric unit: a methylene group of the spacer, the head group and three methylene groups of the alkyl chains (1‐, 2‐, and 7‐position). In contrast to the monomer a pronounced motional gradient was observed in the polymer, where the spacer is almost completely immobilized, whereas the mobility in the middle of the hydrophobic chains is largely retained. A quantitative analysis of the NMR lineshapes shows a gradual increase of molecular mobility in the polymer above the phase transition due to an increase in both the jump rate and the number of conformational transitions.
Molecular motions in a liquid‐crystalline lipid bilayer. Molecular dynamics simulation
Authors: Khalatur Pavel G. , Pavlov Alexander S. , Balabaev Nikolai K.
Published: April 2003

The results of a molecular dynamics study of a lipid bilayer are discussed. As a model we consider an ensemble of 2 × 10 flexible chains consisting of 16 groups in a box with lateral (x, y) periodicity conditions. The chains interact with each other and with the aqueous medium. Terminal groups are bound near to the bilayer surfaces by a harmonic potential. All numerical results are compared with those obtained for an isotropic polymer liquid with the same density as for the bilayer. From a study of the order parameters we conclude that the bilayer is in the liquid‐crystalline state with the chains expanding in the z‐direction normal to the surfaces. Segmental order parameters are in reasonable agreement with experimental NMR data. Dynamic properties discussed include the frequency spectrum of the velocity autocorrelation function of particles, the incoherent dynamic structure factor, dielectric absorption, and luminescence polarization. It is found that compared with the bulk polymer liquid, the molecular motions in the bilayer are quite different. Such features arise mainly from existing strong correlations in the bilayer and from a different molecular organization of the chains in the bilayer and in the bulk liquid.
Polymerization of lactams, 80. Anionic polymerization of lactams accelerated with N‐iminolactams, 1 2‐pyrrolidone
Authors: Brožek Jiří , Řehák Petr , Marek Miroslav , Roda Jan , Králíček Jaroslav
Published: April 2003

The anionic polymerization of 2‐pyrrolidone (PD) was initiated with the potassium salt of PD at 30–50°C and accelerated with the following N‐iminolactams (NIL): 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone (1), 1‐(1‐azacyclohept‐1‐en‐2‐yl)‐2‐pyrrolidone (2), 1‐(1‐azacyclonon‐1‐en‐2‐yl)‐2‐pyrrolidone (4), 1‐(1‐azacyclohept‐1‐en‐2‐yl)‐1‐ azacycloheptan‐2‐one (3) and 1‐(phenyliminomethyl)‐2‐pyrrolidone (5). The polymerizations exhibit formal kinetics of zero order with respect to the monomer with substantially differing apparent rate constants depending on the type of NIL used. The same limit conversions are attained in all cases. The possible role of NIL in the polymerization system is discussed.
Terpolymerization of maleic anhydride, styrene and electron‐acceptor monomers
Authors: Florjańczyk Zbigniew , Krawiec Włodzimierz
Published: April 2003

The free‐radical terpolymerization of maleic anhydride, styrene, and acrylic monomers such as acrylonitrile, methyl acrylate and methyl methacrylate was studied. The alternating copolymerization of maleic anhydride with styrene was found to be favored in those systems. Contrary to theoretical predictions, maleic anhydride is more reactive than styrene in ternary systems. The relative reactivity of the acrylic monomers studied was found to decrease in the order: methyl methacrylate ≥ methyl acrylate > acrylonitrile. In the presence of a Lewis acid, such as ZnCl2 or C2H5AlCl2, the relative reactivity of acrylic monomers increases and at the respective complexing agent concentration the copropagation of the acrylic monomer with styrene can dominate. On the basis of the results obtained, some aspects of the mechanism of alternating propagation in systems comprising an electron‐donor monomer and two electron‐acceptor monomers are discussed.
Polymérisation de monomères carbonates de vinyle
Authors: Freire Maria Telma Gomes , Danicher Louis , Lambla Morand
Published: April 2003

Free‐radical polymerizations of several aliphatic and aromatic N‐substituted vinyl carbonates are described. The bulk polymerization was initiated at 35°C with di‐tert‐butylcylohexyl peroxydicarbonate yielding high‐molecular‐weight poly(vinyl carbonate)s. The structure of these polymers was examined by FTIR spectroscopy and the molecular weight by GPC. The effects of the substituents on the physical properties of the resulting polymers were studied. A comparison of the properties with those of similar compounds described in the literature was made.
In‐situ photopolymerization of an oriented liquid‐crystalline acrylate
Authors: Broer Dirk J. , Finkelmann Heino , Kondo Katsumi
Published: April 2003

The photoinitiated polymerization of 4‐biphenylyl 4‐(6‐acryloyloxyhexyloxy)benzoate (1) in its oriented liquid‐crystalline state was studied. Monomer1has a thermotropic nematic phase between 88°C and 98°C, a monotropic nematic phase between 76°C and 88°C, and a monotropic smectic phase below 76°C. The orientation of1was established in a glass cell provided with a rubber polyimide coating and characterized by birefringence measurements. During polymerization both the birefringence and the liquid‐crystalline transition temperatures increase, indicating that the orientation was maintained. The oriented poly(1) is polycrystalline at room temperature, becomes smectic at 90°C, nematic at 172°C, and isotropic at 190°C. The order parameter of the nematic poly(1) is lower than that of the nematic monomer1at equal reduced temperatures.
Interference effects from liquid‐crystalline block copolymers: Matrix method and analytical approach
Authors: Bonart Richard , Dietrich Johann , Zott Hans
Published: April 2003

In order to calculate the interference effects from liquid‐crystalline block copolymers, Biswas and Blackwell have presented an elegant matrix method. For the cases where an analogous, analytical approach can be made, we show that the matrix method leads to the same result as the analytical method. In addition to the conventional reciprocal lattice with reciprocal lattice points at h2π/〈c〉, where 〈c〉 is the average periodicity, one has to consider three further reciprocal lattices with reciprocal lattice points h′2π/cA, h″2π/cB, and h″′2π/(cB + cB). cB and cB are the lengths of the comonomer units. This method will be illustrated by model calculations for p‐benzoate/biphenyl‐4,4′‐diylisophthalate copolyesters

Poly[(isophthalic acid‐alt‐biphenyl‐4,4′‐diol)‐co‐4‐hydroxybenzoic acid].

. Further, interesting possibilities of the matrix method will not be treated here.