bluuebunny/crossref_metadata_2025 huggingface dataset:
Polylactones, 11. Cationic copolymerization of glycolide with L,L‐dilactide
Authors: Kricheldorf Hans R. , Kreiser Ingrid
Published: April 2003

Copolymerizations of glycolide with L,L‐dilactide were conducted in chloroform, 1,2‐dichloroethane and nitrobenzene. Chlorosulfonic acid, triflic acid, boron trifluoride, triethyloxonium tetrafluoroborate, but mainly methyl triflate, were used as initiators. 50°C was found to be an optimum reaction temperature, because higher temperatures resulted in dark coloured products of low viscosities. The composition of the copolyesters was determined by 1H NMR spectroscopy and the sequences by 13C NMR spectroscopy. Dyad splitting of the carbonyl signals allowed an accurate calculation of average block lengths. Under all circumstances glycolide showed a higher rate of incorporation, and truely random sequences were never obtained. However, the relative reactivities of both monomers largely depend on the nature of the initiator. The best results with regard to random sequences were obtained in 1,2‐dichloroethane with methyl triflate (rG = 10,5 and rL = 0,9) and with triflic acid (rG = 14,0 and rL = 0,5). DSC measurements revealed that most samples possess crystalline domains of polyglycolide blocks. Nonetheless, many samples are soluble in hexafluoro‐2‐propanol and the amorphous samples also in dichloromethane or chloroform.
Effect of ionenes on structure and catalytic activity of cobaltphthalocyanine, 1. Visible light spectroscopic investigations
Authors: van Welzen Joke , van Herk Alex M. , German Anton L.
Published: April 2003

The structural behaviour of cobalt(II)phthalocyanine‐tetrasodium sulfonate (CoPc(NaSO3)4) (1), a catalyst used in thiol oxidation, was investigated in the presence of ionenes (poly‐quaternary ammonium salts), (2) using visible light spectroscopy. It was observed that ionenes, which have been shown to promote the catalytic activity, strongly enhance the aggregation of the cobalt complex. No cobalt site isolation occurred up to N+/Co = 105. Furthermore, a stoichiometric CoPc(NaSO3)4/ionene complex appeared to be formed with an N+/Co‐ratio of 4:1. This ratio was found to hold for ionenes with M̄n varying from 6 100 to 22 000 and charge densities from 0,8 to 1,5. As the charge density was increased, the observed CoPc(NaSO3)4 spectrum was more affected. Experiments with oxygen in alkaline solution revealed that the complex was resistant toward oxygen adduct formation in the presence of ionenes. This phenomenon is discussed in relation to the catalytic activity of the system.
Metathesis polymerization of exo,exo‐, endo, exo‐ and endo, endo‐5,6‐dimethylbicyclo[2.2.1]hept‐2‐enes; microstructure of the polymers and their hydrogenated products
Authors: Greene Ruth M. E. , Ivin Kenneth J. , McCann G. Malachy , Rooney John J.
Published: April 2003

Polymers of exo,exo‐, endo,exo, and endo,endo‐5,6‐dimethylbicyclo[2.2.1]hept‐2‐ene monomers were prepared using a selection of eight metathesis catalysts and their structures examined by 13C NMR spectroscopy. Tacticities could be determined for the polymers of the endo, endo and endo,exo monomers and for all three hydrogenated polymers. RuCl3 gave hightrans atactic polymers while ReCl5 gave high‐cis syndiotactic polymers, but WCl6/Bu4Sn gave a high‐cis atactic polymer of the endo,endo monomer. The endo,exo monomer was unusual in giving polymers of relatively low cis content (fraction of cis double bonds σc ≤ 0,3), and with strong exo,endo (XN) bias except in the case of RuCl3. The parallel with the head, tail (HT) biased polymers of 1‐methylbicyclo[2.2.1]hept‐2‐ene is noted. Polymers of the exo,exo and endo,endo monomers have a blocky cis/trans double bond distribution at moderate cis content. The results are discussed in terms of a mechanism involving propagation by metal‐carbene, metal‐carbene‐olefin and metallacyclobutane complexes.
Compositional analysis of styrene‐acrylic acid copolymers by 1H NMR
Authors: Koźluk Tomasz , Spychaj Tadeusz , Hamielec Archie
Published: April 2003

1H NMR analysis of low molecular weight styrene‐acrylic acid (St/AA) copolymers is described. Three approaches to copolymer composition determination were evaluated and these include: (i) use of the signal for the carboxylic acid protons of the original copolymers, (ii) formation of the ammonium salt of the copolymers and then use of the signal for the ammonium protons, (iii) exchange of the ammonium protons with deuterium (…COONH4 + 4D2O → … COOND4 + 4DOH) and use of the signal for the proton on DOH to estimate the number of acid groups in the original copolymer sample.
X‐ray investigations of liquid crystalline homo‐ and copolysiloxanes with paired mesogens
Authors: Diele Siegmar , Oelsner Steffi , Kuschel Frank , Hisgen Bernd , Ringsdorf Helmut , Zentel Rudolf
Published: April 2003

X‐ray scattering experiments on oriented polysiloxanes with paired mesogens and different distances between these swallow‐tailed side groups show a remarkable dependence of the smectic monolayer thickness on the degree of dilution, whereas the interplanar distance of the side groups remain nearly constant. Due to the dominating interaction of the mesogenic moieties, the flexible main chain is forced to take part in the layer formation. A packing model is proposed to explain the results of the X‐ray studies. For polymers with five or more dimethylsiloxane copolymer segments, a diffuse scattering appears in the smectic as well as in the isotropic phase. This scattering is independent of the orientation of the samples. It is probably caused by the main chain and has also been observed for the unsubstituted poly(hydrogenmethylsiloxane).
Studies in ring‐opening polymerization. The kinetics of the reactions between tungsten hexachloride and cyclopentene: A study of the metathesis initiation reaction
Authors: Amass Allan J. , Lotfipour Mahmoud , Zurimendi Jon A. , Tighe Brian J. , Thompson Cheryl
Published: April 2003

The complex series of reactions that takes place between WCl6 and cyclopentene was studied spectroscopically. The products of reaction remain soluble when chlorobenzene is used as solvent. A number of intermediates was observed and the kinetics of formation and removal of these was studied in detail. A complex series of reactions was postulated to account for these changes and the significance of each reaction to the overall scheme was determined by computer simulation of the changes that occur. One of the products has particular significance in the scheme of reactions since it is believed that this species is eventually responsible for the monometallic initiation of the polymerization of cyclopentene. The reaction was also studied gas chromatographically when it was shown that the reaction is accompanied by the formation of a complex mixture of products. One of these products was shown to have the mass spectrum that would be expected of 3‐chlorocyclopentene and a reaction scheme that would account for its formation is postulated. The reactions involved in the generation of centres active towards the formation of polypentenamer were considered for both monometallic and bimetallic (WCl6/AlR3) catalyst.
On the polymerization of 2‐isopropenylnaphthalene, 8. Reactivity and structure of the living species at different temperatures
Authors: Rhein Thomas , Boileau Sylvie , Schulz Rolf C.
Published: April 2003

ESR spectroscopic analyses of the deep‐green solutions of living poly(2‐isopropenylnaphthalene) [poly(2‐IPN)] in THF at −80°C provided no evidence of the presence of radical anions as long as butyllithium (BuLi) was used as initiator. In contrast to this finding, radicals could indeed be detected if the polymerization was performed with metallic potassium in THF. These radicals were found to be only stable at low temperatures. UV/VIS spectra of solutions of 2‐IPN in THF or toluene and of catalytic quantities of BuLi were recorded at temperatures between −45 and +20°C. On heating to >0°C, the colour of the deep‐green solution changes irreversibly to reddish‐brown, and this colour change is associated with a spontaneous deactivation of the living poly(2‐IPN). End‐capping reactions with anthracene derivatives and the block copolymerization with hexamethylcyclotrisiloxane gave a first idea of the reactivity and structure of the species present in the reddish‐brown solution. A suggestion is made for the deactivation mechanism.
The use of pressure dilatometry for studying phase separation in polymer mixtures
Authors: Walsh David J. , Zoller Paul
Published: April 2003

It has been shown that it is possible to use pressure dilatometry (also known as pressure‐volume‐temperature (PVT) techniques) to follow the phase separation of a polymer blend. PVT data have been obtained for polyether sulfone, poly(ethylene oxide) and blends of the two over a range of compositions. For the pure polymers one can observe the glass transition and melting transitions, respectively. In the case of the blends the volume expansion accompanying phase separation on heating can be seen along with the different thermal expansion coefficients of the generated two phase structures. One can also observe the effect of pressure in elevating the temperature of phase separation.
Exoemission of polymers induced by deformation and fracture: High density polyethylene
Authors: Fuhrmann Jürgen , Scherer Günter H. , Nick Leo
Published: April 2003

The deformation‐induced exoemission of high density polyethylene stressed uniaxially is a true, intrinsic polymer property, i.e., not resulting from other experimental parameters, e.g., atmospheric gases, adsorbed layers, surface charges, and other extrinsic influences. The processes which originate tribostimulated exoemission are irreversible and depend strongly on the deformation ratio. The occurrence of exoemission is correlated with molecular fracture processes. The energy distribution of the emitted negatively charged particles exhibits a narrow maximum in the range of 5 to 15 eV (8·10−19to 24·10−19J).
Quaternization of poly(N‐tert‐butyliminoethylene)
Authors: Goethals Eric J. , Vandevelde Marleen , Dierick Anneke , Rigole Wilfried
Published: April 2003

Poly(N‐tert‐butyliminoethylene) was quaternized with several agents. Only the very reactive methyl trifluoromethanesulfonate allowed to attain relatively high quaternization degrees after short reaction times. The maximum degree of quaternization was 0,44. This was attributed to the complete lack of reactivity of amino functions which have a quaternized neighbour. By means of 1H NMR spectroscopy it was possible to measure the fractions of the different triads and . Analysis, by means of Monte Carlo calculations, of the relative amount of these triads as a function of the degree of quaternization lead to the conclusion that the reactivity of the first, second and third nitrogen next to an ammonium function is 0,0,20 and 0,57, respectively, the reactivity of a nitrogen in an ammonium‐free chain being 1. This shows that the electrostatic deactivation exerts its action to at least nine atoms away from the charged atom. The quaternized polymer is unstable even at room temperature. After a few days the formation of isobutene is observed.
Kinetische analyse der copolymerisationsgeschwindigkeit von N‐vinyl‐2‐pyrrolidon mit styrol und methylmethacrylat
Authors: Braun Dietrich , Czerwinski Wojciech K.
Published: April 2003

The polymerization rate of two binary monomer systems styrene (St)/N‐vinyl‐2‐pyrrolidone (NVP) and NVP/methyl methacrylate (MMA) was investigated dilatometrically in bulk at 60°C with AIBN as initiator. While the copolymerization rate of the system St/NVP can be satisfactorily described by means of the classical reaction model, this is not the case for the system NVP/MMA. This deviation from the classical model can be explained by a charge‐transfer interaction between NVP and MMA which was measured by means of 1H and 13C NMR spectroscopy.
Préparation et caractérisation des poly(o‐chlorométhylstyrène), poly(m‐chlorométhylstyrène) et poly(p‐chlorométhylstyrène). Etudes des résonances magnétiques nucléaires 1H NMR et 13C NMR. Application à l'étude d'une résine de type merrifield
Authors: Monthéard Jean‐Pierre , Camps Marcel , Boinon Bernard , Tabet Driss Ainad , Pham Quang Tho
Published: April 2003

Ortho‐, méta‐ and para‐chloromethylstyrene were polymerized and their 1H NMR and 13C NMR spectra were studied. The knowledge of the chemical shifts, especially those in 13C NMR, allows the analysis of poly(o‐‐chloromethylstyrene‐co‐m‐‐chloromethylstyrene) and of a Merrifield‐type resin which was prepared by a terpolymerization reaction of styrene, chloromethylstyrene and divinylbenzene.
Polylactones 12. Cationic polymerization of 2,2‐dimethyltrimethylene carbonate
Authors: Kricheldorf Hans R. , Dunsing Ruth , Albet Angels Serra i
Published: April 2003

The polymerization of 2,2‐dimethyltrimethylene carbonate (1) was initiated with borontrifluoride etherate, trifluoromethanesulfonic acid (triflic acid), methyl triflate and ethyl fluorosulfate. The reaction was studied at 20, 50, 80 and 120°C in 1,2‐dichloroethane and nitrobenzene. Methyl triflate and triflic acid turned out to be the most reactive initiators. Yet, due to “black biting” degradation, yields > 80% were never obtained. With BF3 etherate yields up to 98% and molecular weights (M̄n) up to 5200 g/mol were found. From 1H NMR and IR spectra it can be deduced that methyl triflate alkylates the exocyclic oxygen (carbonyl group) and the resulting carbenium ion reacts with its counterion by ring‐opening of the alkyl‐oxygen bond. The oligomers and polymers formed in this way initially possess methyl (or ethyl) carbonate groups at one end and triflate groups at the other end of the chain. Elemental analyses and IR spectra prove that no carbon dioxide is lost in the course of the cationic polymerization. DSC measurements showed that crystallinity and melting points of poly(1) largely depend on the polymerization conditions in contrast to the glass transition temperature.
Réactivité du groupement N‐(époxy‐2,3 propyl)‐N‐méthylamino vis‐à‐vis d'amines aromatiques à l'état fondu. Etude des mécanismes et des chemins réactionnels
Authors: Grenier‐Loustalot Marie‐Florence , Orozco Laurence , Grenier Philippe
Published: April 2003

Mechanism and kinetics of the reactions of N‐(2,3‐epoxypropyl)‐N‐methylaniline (1) with aniline or 4,4′‐sulfonyldianiline (3) were investigated using high performance liquid chromatography and 13C FT NMR under different conditions (110–172°C). Comparison of 1 with its derivatives shows that the activity of the 2,3‐epoxypropyl group in such epoxides depends on the structure and the substituents at the benzene ring; etherification may occur already before the secondary amine is consumed.
Study of the molecular structure of ethylene‐propylene copolymers obtained with catalysts of different composition
Authors: Yechevskaya Lyudmila G. , Bukatov Gennadii D. , Zakharov Vladimir A. , Nosov Andrey V.
Published: April 2003

The monomer composition and sequence distribution in ethylene‐propylene copolymers (EPCs) obtained with supported titanium/magnesium (TMC) and vanadium/magnesium (VMC) catalysts as well as with titanium trichloride was studied by means of 13C NMR spectroscopy. Based on these data ethylene‐propylene reactivity ratios were determined. The EPCs obtained on these catalysts are inhomogeneous in composition; the soluble fractions contain larger amounts of propylene. The microstructures of copolymers obtained on TMCs and TiCl3 are similar. For EPCs obtained on VMCs, propylene “head‐to‐head” or “tail‐to‐tail” inversions and a more homogeneous distribution of propylene are observed.
Functionalization of poly(methyl methacrylate) by free radical polymerization, 1. Transfer with functional thiols
Authors: Clouet Gilbert , Knipper Magali
Published: April 2003

Chain transfer constants (Ctr) for three phosphonated thiols in methyl methacrylate (MMA) polymerization at 60°C were determined from measurements of the degree of polymerization. These thiols were: diethyl 2‐mercaptoethyl phosphate (1), diethyl 2‐mercaptoethylamidophosphate (2), and tetraethyl mercaptomethylethylene bis(phosphate) (3). Transfer efficiencies of the thiols were found to be dependent upon their structures. The Ctr value of thiol 2 with MMA was the lowest in the present series, which can be attributed to a possible charged tautomeric form which eventually may reduce the electron density on the thiol, thus rendering the chain transfer reaction with the PMMA radical less feasible. Ctr values of thiol 1 were evaluated at 55, 60, 65, 70 and 75°C. This thiol behaves as an “azeotropic” transfer agent for MMA at 96°C.
Copolymerization at equilibrium. General treatment
Authors: Szymański Ryszard
Published: April 2003

The relationships for copolymerization of any number of comonomers at equilibrium are derived. The presented sets of equations allow to predict the comonomers equilibrium concentrations and the copolymer structure, as well as the equilibrium concentrations of polymers of any length and their composition, provided the initial state and equilibrium constants are known. If the ratio of concentrations of active centers and copolymer composition at equilibrium are known, the relationships allow to determine the equilibrium constants for homo‐ and cross‐propagations.
Photoprocesses in statistical, end‐labelled, and block copolymers containing naphthalene chromophores
Authors: Chen Liusheng , Winnik Mitchell A. , Al‐Takrity Emaad Taha Bakir , Jenkins Aubrey D. , Walton David R. M.
Published: April 2003

Fluorescence spectroscopy in highly dilute solutions has been used to study the emission from naphthyl groups attached to poly(methyl methacrylate) molecules prepared by (i) free‐radical polymerization, giving an essentially random distribution of naphthyl groups along the chain, and (ii) anionic polymerization, producing polymers with naphthyl groups in terminal units only. The influence of molecular architecture on the fluorescence is discussed. In particular it is shown that it is possible to incorporate one single naphthyl group at one end of a polymer chain but that attempts to introduce a controlled greater number lead to a product with a distribution of naphthyl‐group constents.
Fourier transform infrared spectroscopic study of polyacetylene, 1. Spectral assignment and characteristics of Z/E (“cis”/“trans”) geometric isomers
Authors: Chen Zhongxin , Liu Min , Shi Mingxiao , Shen Zhiquan , Hummel Dietrich O.
Published: April 2003

An FTIR spectroscopic study was carried out for rare‐earth polyacetylenes

IUPAC name: poly(vinylene).

(PA) containing both Z (“cis”) and E (“trans”)

We distinguish formally between configurations (Z, E = “cis”, “trans”) and conformations (cis, trans), though in the case of poly(vinylene) the physical quality is virtually the same.

geometric isomers. Spectral assignments were made by the study of PA samples with different Z/E ratios and by referring to the known assignment of the IR spectrum of PA obtained with Ti(OC4H9)4·Al(C2H5)3. The conjugation effect of Z or E CHCH sequences and their length distribution in PA are investigated by spectral subtraction and peak separation. It is shown that the frequency of v(CH) (out‐of‐plane deformation) is located in the regions 741 to 747 cm−1 and 940 to 1014 cm−1 for Z‐ and E‐PA, respectively, depending on the conjugation length. At the beginning of thermal isomerization of Z‐PA, long Z sequences are interrupted quite frequently; this causes a shift of v(CH) towards higher frequencies. In high E‐PA obtained by thermal isomerization of Z‐PA, uninterrupted long E sequences persist. This demonstrates that a crosslinking reaction between PA chains is not conspicuous during the thermal isomerization process.
Precipitation‐crystallization of poly(1,4‐phenyleneterephthalamide) from nematic solution
Authors: Chen Shouxi , Jin Yongze , Qian Renyuan , Cai Liying
Published: April 2003

Precipitation‐crystallization of poly(1,4‐phenyleneterephthalamide) (PPTA) from sheared nematic solutions was studied by polarized light microscopy. Three kinds of morphological structures, viz. spherulite, shish‐kebab, and band structures were observed in films prepared from sheared anisotropic solutions. An exhaustive study of the band structure by using various techniques to prepare the samples for electron microscopy was made. The results obtained indicated that the morphology of the band structure is composed of fibrils bent in a zigzag manner and highly oriented along the shearing direction of the molecular chains in the neighbouring bands with the angle ±14° as measured from selected‐area electron diffraction. A finer periodical structure of 300 Å arranged along the zigzag fibrils was observed.
Heats of dilution of poly[styrene‐ran‐(butyl methacrylate)] solutions measured with an automatic flow microcalorimeter
Authors: Kyohmen Masayuki , Inoue Keizo , Baba Yoshihiro , Kagemoto Akihiro , Beatty Charles L.
Published: April 2003

In order to obtain information about the thermodynamic behaviour of copolymers in solution, we built an automatic flow microcalorimeter equipped with a computer that satisfies the requirements of accuracy, reliability, and rapidity for the measurement of heats of dilution of copolymer solutions. By using this apparatus, the heats of dilution of the random copolymer, poly[styrene‐ran‐(butyl methacrylate)] in ethyl methyl ketone solutions were measured at 298 K. Furthermore, light scattering of the copolymer and its constituent homopolymer solutions was measured at 298 K. From the combination of the heat of dilution and the light scattering results, thermodynamic and intramolecular interaction parameters of the copolymer chain were determined.
Reactivity of vinyl monomers in the copolymerization and terpolymerization with sulfur dioxide
Authors: Florjańczyk Zbigniew , Floriańczyk Tadeusz , Kłopotek Beata B.
Published: April 2003

The relative reactivities of vinyl monomers in low‐temperature copolymerizations and terpolymerizations with SO2 in the presence of tert‐butyl hydroperoxide as initiator were compared. The highest copolymerization rates were found in systems containing an electron‐donor monomer of low resonance stabilization, and the resulting products have an alternating structure. In reactions with monomers of high resonance stabilization and electron‐acceptor properties, mainly homopropagation of the comonomer proceeds. In the terpolymerization of SO2 with two electron‐donor monomers, the relative reactivity of monomers depends mainly on their resonance stabilization. In the terpolymerization in systems SO2/electron‐donor monomer/electron‐acceptor monomer the relative reactivity of acceptor monomers decreases with increasing inductive effect in the molecule.
Precursors of hydrophilic polymers, 8. The structure of copolymers of 2‐dimethylaminoethyl methacrylate and 2‐methacryloyloxyethyltrimethylammonium iodide
Authors: Přádný Martin , Ševčík Stanislav
Published: April 2003

Quaternization reactions of poly(2‐dimethylaminoethyl methacrylate) using methyl iodide were carried out up to 50% conversion in 18 chemically different solvents. Copolymers which contain moderate hydrophilic 2‐dimethylaminoethoxycarbonyl groups and strongly hydrophilic 2‐trimethylammoniumethoxycarbonyl iodide groups were obtained. Potentiometric titration showed that in some solvents the reaction proceeds by the zip mechanism, i.e. copolymers with a predominantly block structure are formed, while in other solvents the reaction proceeds along the macromolecular chain randomly, that is, giving rise to statistical copolymers.
Lichtstreubefunde zur Kettenspaltung von Polystyrol in sauerstoffreien CCl4‐ und CHCl3‐Lösungen bei Lichteinwirkung der Wellenlängen λ ≥ 270 nm
Authors: Woliński Leszek , Turzyński Zbigniew , Witkowski Konrad
Published: April 2003

The photodegradation of polystyrene (PS) in deoxygenated solutions of CCl4 and CHCl3 by irradiation with ultraviolet light of wavelengths λ ≥ 270 nm is investigated by quasielastic and integral light scattering techniques. Molar mass distributions w(M), number‐ and weight‐average molar masses M̄n and M̄w as well as the average number of chain scissions per macromolecule x(t) as a function of the time of irradiation t were determined. The results obtained prove that efficient photodegradation occurs in CCl4‐ and CHCl3‐solutions of PS, although measurable changes in molar mass of irradiated PS starts to occur only after several hours of irradiation.
ESR determination of rate constants for the radical polymerization of methyl phenethyl itaconate
Authors: Sato Tsuneyuki , Morino Kazutaka , Tanaka Hitoshi , Ota Tadatoshi
Published: April 2003

Phenethyl 2‐(methoxycarbonylmethyl)acrylate (methyl penethyl itaconate) (1) was prepared and its polymerization with dimethyl 2,2′‐azoisobutyrate (2) was investigated kinetically in benzene. The polymerization rate (Rp) was found to be expressed by Rp = k·[2]0,5·[1]1,8 (at 50°C). Further, a higher dependence of Rp (2nd order) on the concentration of 1 was observed at 61°C. The overall activation energy of the polymerization was calculated to be a low value of 50,3 kJ/mol. The initiator efficiency (f) of 2 was determined to be 0,48 to 0,22 at 50°Cand 0,50 to 0,28 at 61°C. f decreases with increasing monomer concentration due to the high viscosity of 1. The poly(1) radical is stable enough to be observable by ESR at high temperatures (50–60°C). Rate constants of propagation (kp) and termination (kt) were estimated using the poly(1) radical concentration determined by ESR. kp [6,0 to 121/(mol·s) at 50°Cand 7,1 to 15 1/(mol·s) at 61°C] shows a trend to increase with the concentration of 1. On the other hand, kt [2,9·104 to 17·1041/(mol·s) at 50°Cand 6,9·104 to 45·1041/(mol. s) at 61°C] decreases with increasing MPI concentration. This behavior is responsible for the high order with respect to monomer concentration. Copolymerization of 1 (M1) with styrene (M2) at 50°Cgave the following results: r1 = 0,36, r2 = 0,40, Q1 = 0,82 and e1 = + 0,59. Using the above results, the rate constants of the cross‐propagations were estimated to be k12 = 22 1/(mol·s) and k21 = 308 1/(mol·s) at 50°C.
Photocrosslinking behavior of poly(vinyl alcohol)s with pendent styrylpyridinium or styrylquinolinium groups
Authors: Ichimura Kunihiro
Published: April 2003

Poly(vinyl alcohols) (PVA's) with pendent styrylpyridinium (SbQ), styrylquinolinium (QQ), or oxystyrylquinolinium (OQQ) exhibit anomalously high photosensitivity, even if the content of photosensitive groups is very low. This phenomenon was studied by measuring the sensitivity to crosslinking quantitatively using monochromatic light. When the content of SbQ or OQQ exceeds ca. 1 mol‐%, the photoinduced gelation behaviour was found to be in the line with Charlesby's equation, suggesting that the absorbed light energy leads specifically to interamacromolecular photodimerization of SbQ or OQQ. Under these circumstances, the quantum efficiency for the photodimerization of SbQ and OQQ was estimated to be in the ranges of 0,31–0,37 and 0,10–0,17, respectively. The applicability of PVA‐SbQ to water‐developable photoresists for microfabrications is discussed. The sensitivity characteristics of PVA having OQQ and analogous groups is also mentioned in view of the application to Ar laser resists.
Calculation of domain sizes in block copolymers with broad interphase
Authors: Bühler Fritz , Gronski Wolfram
Published: April 2003

The domain dimensions of poly(styrene‐b‐isoprene) diblock copolymers with polyisoprene spheres in a continuous polystyrene matrix, in which the interphase is broadened by a random poly(isoprene‐co‐styrene) copolymer block, are significantly smaller than in unmodified block copolymers. The depression of domain sizes and the reduced exponent of the molecular weight dependence in these systems are calculated on the basis of Helfand's theory in which the surface and the conformational entropy were appropriately modified. The domain dimensions of unmodified block copolymers, for which hitherto larger than experimental radii were predicted by the original theory, are also in good agreement if calculated by the proposed phenomenological approach.
Spezifische Adsorbentien für das Peptidantibiotika synthetisierende Enzymsystem Gramicidin S Synthetase, 2. Kupplung niedermolekularer Spacer/Ligand‐Verbindungen mit reaktiven polymeren Trägern und Untersuchung der Adsorptionswechselwirkung dieser polymeren Produkte mit Gramcidin S Synthetase
Authors: Schlünsen Jürgen , Manecke George , Schröter‐Kermani Christa , Kleinkauf Horst
Published: April 2003

The inhibition constants (KI) of aliphatic and aromatic amide derivatives of phenylalanine and proline for GS1 and GS2 of the enzyme system gramicidin S synthetase were determined. These compounds act as competitive inhibitors. Some of these compounds (spacer/ligand compounds) were reacted with epoxy‐activated Sekpharose 6B or with crosslinked poly(vinyl alcohol). The resulting—for GS1 or GS2 more or less specific—adsorption materials, were used for the purification of these multi‐enzyme systems.
The dynamic mechanical properties of poly(alkyl 2‐cyanoacrylates)
Authors: Cheung King H. , Guthrie John , Otterburn Michael S. , Rooney John M.
Published: April 2003

Various poly(alkyl 2‐cyanoacrylates) and poly(allyl 2‐cyanoacrylates) having different molecular weights have been prepared. Dynamic mechanical analysis was carried out over the temperature range 23°Cto 230°Cat a fixed frequency of 110 Hz, in order to study the effect of temperature on the storage modules, loss modulus and loss tangent of the films. From these data, the glass transition temperature of the polymers could be determined and the effect of the alkyl group on the stiffness of the polymers could be evaluated. It is shown that crosslinking occurs in the case of poly(allyl 2‐cyanoacrylates) when it is subjected to temperatures above its glass transition temperature. This crosslinking is seen as a rapid increase in the storage modulus. This increase is eliminated if the polymer samples are thermally aged prior to dynamic mechanical analysis.
X‐ray studies on diethynylbenzene derivatives in view of the solid‐state polymerization
Authors: Kai Yasushi , Yamamoto Akira , Xu Duanjun , Kasai Nobutami , Hagihara Masahiko , Yamamoto Yukio , Takahashi Shigetoshi , Hayashi Koichiro
Published: April 2003

The crystal structures of three diethynylbenzene derivatives, 3‐[2‐(3‐acetoxy‐1‐propynyl)‐4,5‐dimethylphenyl]‐2‐propynyl acetate (1a), 3‐[4‐(3‐acetoxy‐1‐propynyl)‐2,5‐dimethylphenyl]‐2‐propynyl acetate (1b), and 3‐[2‐(3‐acetoxy‐1‐propynyl)‐4,5‐dimethoxyphenyl]‐2‐propynyl acetate (2), were determined by means of X‐ray diffraction. The unique monomer packings interpret the characteristic freatures of these compounds in the solid‐state polymerization upon irradiation with γ rays.
Polymerization of lactams, 81. Anionic polymerization of lactams accelerated with N‐iminolactams, 2 ϵ‐caprolactam (6‐hexanelactam)
Authors: Brožek Jiří , Marek Miroslav , Roda Jan , Králíček Jaroslav
Published: April 2003

The anionic polymerization of ϵ‐caprolactam (CL), initiated with the sodium or potassium salt of CL, was shown to be accelerated with 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 (3), 1‐(1‐azacyclohept‐1‐en‐2‐yl)‐1‐azacycloheptan‐2‐one (4) and 1‐(phenyliminomethyl)‐2‐pyrrolidone (5), both above the below the melting temperature of the polymer (150‐230°C). The postpolymerization of the product was followed at 180°C for certain cases.
Polymerization of lactams, 84. Anionic polymerization of lactams accelerated with N‐iminolactams, 3. The role of 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone in the anionic polymerization of 2‐pyrrolidone
Authors: Brožek Jiří , Roda Jan , Králíček Jaroslav
Published: April 2003

The anionic polymerization of 2‐pyrrolidone was accelerated with 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone (1), labelled with nuclide 15N. The incorporation of 1 into the polymer was followed by the change of isotope concentration, and the apparent rate constants were derived for some elementary reactions in the investigated polyreaction. The interchange reaction between 1 and monomer was also measured. 1 can be considered a slow activator, each molecule incorporating into the polymer being the precursor of a growth centre.
Zwitterionic polymerization of butyl cyanoacrylate by triphenylphosphine and pyridine
Authors: Cronin John Paul , Pepper David Charles
Published: April 2003

This paper describes a re‐examination of the kinetics and molecular weights formed in the zwitterionic polymerization of butyl cyanoacrylate by triphenylphosphine (Ph3P) and pyridine (Py) in THF, and an extension to include the solvents, diethyl ether (Et2O), dimethoxyethane (DME) and hexane. In THF, the previously observed kinetics were confirmed, yielding evidence for absence of termination, and values for rate constants for initiation (ki) and propagation (kp) with substantial agreement between the values for Kp obtained from both systems. At 20°C, the mean value found for kp in THF was 3 · 105 l · mol−1 · s−1; in Et2O, some 10 times lower, and in hexane, 10 times lower again. The temperature dependence of kp in THF was confirmed to be extremely low and anomalous; in Et2O rather greater and near‐normal, corresponding to an energy of activation of ca. 5 kcal · mol−1. A correction procedure enabled the large experimental scatter in the kp values to be reduced sufficiently to reveal trends downwards at higher concentrations of propagating species, i.e. evidence for their dissociation on dilution. In Py‐initiated polymerizations, excess of pyridinium salts did not depress kp; evidence that the propagating species are preponderately paired ions, not free. It is concluded that at 20°C these species are mainly ‘tight’ ion‐pairs in all solvents, and remain so in Et2O at all temperatures down to −80°C. In THF, over this temperature range, there is increasing solvation producing an increasing proportion of more reactive ‘solvent‐separated’ ion‐pairs. The molecular weights produced under all conditions were high (Mn usually 1 to 3 · 106). Those produced by high concentration of Ph3P did not conform to theory; others followed the ‘no‐termination’ theory as modified to allow for a small effect of transfer.
Bioactive polymers, 51. Synthesis and characterization of a macromolecular prodrug of ampicillin
Authors: Dumitriu Severian , Popa Marcel
Published: April 2003

The coupling reaction of ampicillin with the polysaccharide xanthane in DMSO, using dicyclohexylcarbodiimide as activator, was studied. To find the conditions for maximum yield a regression equation was established, describing the dependence of the yield of coupling product on the reaction parameters (drug/support mole ratio, activator/support mole ratio and duration), starting from an experimental, centrated rotable complex, second order program. The coupling product was spectroscopically characterized and the in vitro release rate of ampicillin in a weakly basic medium was established along with the determination of its antimicrobiological activity.
Structure of dimers and trimers obtained in the cationic oligomerization of propylene
Authors: Audisio Guido , Priola Aldo , Rossini Alessio
Published: April 2003

A structural investigation was carried out on the product of the cationic oligomerization of propylene with the aim of identifying the main isomers present in the dimer and trimer fractions. BF3‐proton donor complexes were used as cationic catalysts. The different isomers, after hydrogenation, were separated by GLC analysis and identified by GC‐MS analysis after comparison with reference products. The structures of the obtained isomers give clear evidence that hydride and methanide shifts may be operative. The influence of the experimental conditions (temperature, type of catalyst) in obtaining the various isomers was evaluated. The number of isomers, mainly those due to methanide shift, increases with increasing reaction temperature. The identified oligomer structures give indications about the chemistry of the first steps of the cationic oligomerization of propylene.
Polyadditions of diisocyanatodiketenes, 3‐(ω‐isocyanatoalkyl)‐4‐(ω‐isocyanatoalkyliden)‐2‐oxetanones, and polymeranalogous reactions with the resulting polymers
Authors: Mormann Werner , Hoffmann Silke
Published: April 2003

Reactions of diisocyanatodiketenes, 3‐(ω‐isocyanatoalkyl)‐4‐(ω‐isocyanatoalkylidene)‐2‐oxetanones (3a–c), with oligomeric diols (4 or 5) as well as 1,4‐butanediol afforded linear polyurethanes containing reactive diketene moieties. From these poly(diketene‐urethane)s polymeranalogues products were prepared by reaction with ethanol, ammonia, water or acetic acid. The resulting polyurethanes containing ß‐ketoester, ß‐ketoamide or keton moieties were characterized by IR spectroscopy, viscosimetry, differential scanning calorimetry and size exclusion chromatography. The properties of the products based on diols 4 or 5 are mainly determined by the oligomeric diols, whereas the (modified) diisocyanate part has a great influence e.g. on the thermal behaviour of the polyurethanes.
ß‐helices of D,L‐alternating valine peptides
Authors: Lorenzi Gian Paolo , Tomasic Lera
Published: April 2003

New conformational data for members of the series Boc‐(D‐Val)m‐(L‐Val‐D‐Val)(n‐m)/2‐OMe (m = 0 or 1; n = total number of residues) are presented and used together with earlier results to formulate general conclusions regarding types and relative stabilities of ß‐helices formed by D,L‐alternating valine peptides. The helices, single‐ or double‐stranded, are of the tightest geometry, the single‐stranded helices having only 4,4 residues per turn(ß4,4 ‐helices) and the double‐stranded ones only about 5,6 residues per turn (↑↓ß5,6‐and ↑↑ß5,6‐helices). The double‐stranded helices are of the type with the highest possible number of interstrand H‐bonds [2(n‐1)] and the antiparallel ones are always strongly preferred. In chloroform solution right‐and left‐handed ß4,4‐helices and left‐handed ↑↓ß5,6 and ↑↑szlig;5,6‐helices are formed by the oligovalines studied with different preferences depending on the peptide chain length and on the parity of the number (odd or even) of residues. The reasons for these preferences are discussed.
Siloxane networks swollen in chloroform/diethyl ether. Divergent preferential adsorption
Authors: Gomez‐Anton Maria Rosa , Masegosa Rosa Maria , Horta Arturo
Published: April 2003

Total solvent sorption and preferential adsorption by networks of poly(methylphenylsiloxane) (PMPS) and of poly(dimethylsiloxane) (PDMS) were determined in the mixture chloroform/diethyl ether. This liquid mixture has a negative GE. The swelling degree of the networks was found to vary linearly with mixed solvent composition (Cl3CH volume fraction ϕ), contrary to what is expected in view of GE < 0. The preferential adsorption by PDMS shows an inversion which is of the divergent type (preferential adsorption of the liquid in major proportion in the mixture). With PMPS no inversion was observed, Cl3CH is always preferentially adsorbed, but the trend is also divergent (with the inversion point displaced to ϕ = 0). The unexpected behaviour of the swelling degree and the displacement of the inversion in preferential adsorption are attributed to strong attractive interactions of the siloxane backbone with the two solvents, and of phenyl groups (in PMPS) with Cl3CH. The intrinsic viscosity of linear PMPS at infinite dilution was determined in the same mixed solvent, in order to check the possible influence of the polymer concentration. Comparison with network swelling shows a similar behaviour.
Photo‐crosslinking of polymers containing pendant epoxy groups
Authors: Tomoi Masao , Oda Hidehiro , Kakiuchi Hiroshi
Published: April 2003

The photo‐crosslinking of polymers containing pendant epoxy groups was carried out at room temp. in the presence of a photosensitive sulfonium salt which is an initiator of cationic polymerization. The crosslinking reactivity of the epoxide‐containing polymers was found to depend on the mobilities of both the backbone of the polymers and the pendant epoxy groups, and on the epoxide structure. The introduction of spacer chains between the polymer backbone and the epoxy groups increases the mobilities of the backbone and the epoxides, resulting in an increases crosslinking reactivity. The introduction of a methyl group at the epoxy ring of the polymers with glass transition temp. (Tg) lower than room temp. enhances the crosslinking reactivity, whereas it diminishes the reactivity for the polymers with Tg higher than room temp. This result can be explained by assuming that the presence of the methyl group results not only in an increase of the epoxide reactivity due to both the inductive effect of the methyl group and the increased ring strain, but also the decreased mobility of the epoxy groups. Thus, the reactivity of the rubbery polymers is principally controlled by the intrinsic reactivity of the epoxides, and the reactivity of the rigid polymers is mainly controlled by the mobility of the reactive sites.
Emulsion copolymerization of acrylonitrile and butyl acrylate, 7. Effect of concentration and type of emulsifier on polymerization kinetics
Authors: Capek Ignác , Mlynárová Márie , Bartoň Jaroslav
Published: April 2003

The emulsion copolymerization of acrylonitrile and butyl acrylate initiated by potassium peroxodisulfate (K2S2O8) in the presence of an anionic, cationic, or nonionic emulsifier has been kinetically investigated at 60°C under batch conditions by gas chromatography (GLC) and gravimetric methods. It is found convenient to define three stages of emulsion polymerization. In the range of low conversion (interval 1) are generated particles and the rate of polymerization increases with increasing polymer particle concentration. In interval 2 (ca. from 15 to 70% conversion) the number of polymer particles and the rate of polymerization (maximum) are constant. At very high conversion (above ca. 70% conversion) the monomer concentration within polymer particles decreases abruptly and the polymerization rate slows down (interval 3). The rate of polymerization in interval 2 was found to be proportional to the 0,41, 0,48, and −0,42 power of the emulsifier concentration for the anionic, nonionic, and cationic emulsifier, respectively. The dependence of the final particle number on the emulsifier concentration deviates from simple micellar theory predictions. The exponent of the emulsifier concentration decreases with increasing emulsifier concentration (for the anionic and nonionic emulsifiers). These results were explained by a coagulative nucleation mechanism. The unexpected polymerization behaviour in the presence of the cationic emulsifier was explained by the formation of a product (due to interaction of the initiator with the emulsifier).
Poly(2,4‐hexadiynylene di‐p‐toluenesulfonate)/polyethylene crystallographic interactions: A polymer decoration study
Authors: Moigne Jacques Le , Graff Sabine , Wittmann Jean‐Claude
Published: April 2003

The crystallographic interactions between the toluenesulfonate‐substituted diacetylene 2,4‐hexadiynylene di‐p‐toluenesulfonate (TS), its corresponding polymer (PTS) and polyethylene (PE) have been established in detail with the help of the polymer decoration technique. Although monomer and polymer are known to be isomorphous, the decoration patterns observed on their (100) crystal surface differ significantly, revealing some subtle structural changes on solid‐state polymerization. The single and twofold orientations obtained on TS and PTS, respectively, are discussed and shown to be of epitaxial character. The PE contact planes for the two decoration orientations are however, significantly different, since the chain packing distances at play are 5,26 Å (or 4,94 Å) and 7,47 Å, respectively. From the very close similarity in crystal structures, it is anticipated that favourable interactions may also exist in many other polydiacetylene/polymer binary systems.
Crystalline morphology of block‐copoly(oxypropylene/oxyethylene/oxypropylene) by small‐angle X‐ray and Raman scattering
Authors: Viras Fotini , Luo Yun‐Zhu , Viras Kyriakos , Mobbs Richard H. , King Terence A. , Booth Colin
Published: April 2003

Block‐copoly(oxypropylene/oxyethylene/oxypropylene)s, with central‐block lengths of 39 and 75 oxyethylene units and end‐block lengths in the range 1 to 13 oxypropylene units, were investigated in their solid states by small‐angle X‐ray diffraction and low‐frequency Raman spectroscopy, supplemented by differential scanning calorimetry. Low‐frequency Raman transitions were assigned to longitudinal modes (LAM) of either unfolded or once‐folded chains. The solid state comprised stacked monolayer lamellae in which the chains were usually tilted with respect to the lamellar end plane.
Schwefelhaltige telechele mit SH bzw. CCH‐endgruppen
Authors: Nuyken Oskar , Siebzehnrübl Florian
Published: April 2003

The reaction of 1,3‐benzenedithiol (1) with 1,4‐diethinyl‐benzene (2) at room temperature yields polymers with thio‐1,3‐phenylenethiovinylene‐1,4‐phenylenevinylene repeating units. The polymerization proceeds without addition of an initiator and without UV‐irridiation. Because of the resulting structure a radical mechanism is suggested. However, the molar mass/conversion relation shows similarities with a step‐growth polymerization. Because of this behaviour this reaction was successfully used for the preparation of telechelics in which molar mass and end groups are controlled simply by the unstoichiometric ratio of the educts.
Supported Ziegler‐Natta catalysts for propene polymerization: Grinding and co‐grinding effects on catalyst improvement
Authors: Spitz Roger , Duranel Laurent , Guyot Alain
Published: April 2003

Solid ternary MgCl2/aromatic ester (A. E.)/TiCl4 catalysts are obtained by grinding MgCl2 followed by co‐grinding MgCl2 and A. E. and then by TiCl4 impregnation. The productivity increases with grinding time up to a maximum value and the stereospecificity decreases continuously. A convenient choice of the A. E. improves the results. The productivity seems to be correlated with details of the pore size distribution. Infrared analysis of the catalyst reveals different ways of Ti‐fixation but without clear relation to the catalytic properties.
Dependence of glass‐transition temperature Tg on tacticity of poly(vinyl chloride). A preliminary study by differential scanning calorimetry
Authors: Mijangos Carmen , Martínez Gerardo , Millán José‐Luis
Published: April 2003

The glass‐transition temperature, Tg, of poly(vinyl chloride) (PVC) has been found to depend linearly on both the overall isotactic triad content and a small fraction of isotactic triads. It was previously demonstrated, that the latter react with sodium benzenethiolate at temperatures as low as −30°C, probably because they adopt a definite local conformation. In general, it was believed before that the tacticity effect on Tg occurs only for disubstituted CC‐polymers, the results obtained in this work for PVC would suggest that specific conformations of isotactic triads can also enhance the motion of chain segments in the polymer.
The gel degradation theory, 2. An experimental verification with model networks formed by the random crosslinking of monodisperse primary chains
Authors: Argyropoulos Dimitris S. , Bolker Henry I.
Published: April 2003

Model networks formed by the crosslinking of monodisperse carboxylated polystyrene chains with decamethylene glycol, were degraded by random cleavage of the crosslinks. The weight‐average molecular weights (M̄w) of the resulting soluble fractions quantitatively correlated with the gel degradation theory which is essentially the Flory‐Stockmayer gelation theory applied in reverse. As such, this paper furnishes support for the universal applicability of the gel degradation theory.