bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of formation of bivalent metal ion complexes with poly‐U
Authors: Sorokin Victor A. , Levchenko Irina V. , Valeev Vladimir A. , Gladchenko Galina O. , Blagoi Yuri P. , Li Ren G.
Published: April 2003

Differential UV spectroscopy is employed to investigate the interaction of poly‐U with Mg2+, Ca2+, Mn2+ and Cu2+ ions in aqueous solution. Mg2+ and Mn2+ ions are observed to bind only to the polynucleotide phosphates, while Cu2+ and Ca2+ also interact with the poly‐U bases. The most probable coordination sites are O(4) and also N(3) for Cu2+ ions. N(3) is a coordination site of Cu2+ ions in UMP and uridine. The rest of the ions do not interact with the bases of the free monomers. Unlike the non‐cooperative Cu2+‐UMP binding, the ion interaction (including Ca2+) with the poly‐U bases is characterized by a positive cooperativity. The association constant of Ca2+ (45 1.mol−1) is 45 times lower than that of Cu2+.
Solid‐state 13C nuclear magnetic resonance studies of side‐group conformations in the rigid‐rod polyester poly[1,4‐phenylene 2,5‐bis(hexadecyloxy)terephthalate]
Authors: Whittaker Andrew K. , Falk Uwe , Spiess Hans Wolfgang
Published: April 2003

The 13C solid‐state NMR spectra of the aromatic polyester 1 with flexible hexadecyloxy side chains are measured at temperatures below and above its solid‐solid phase transition in order to study the conformation of the side chains. The signals due to the CH2 carbons reflect the ratio of trans and gauche conformations at the various positions along the chain. An increase in the gauche content was observed towards the end of the side chain in both phases, however, in the low temperature phase the spectra are dominated by all‐trans sequences. The solid‐solid transition, as detected by differential scanning calorimetry corresponds to a large increase in the gauche content at all positions on the side chain, except near to the rigid polymer backbone. Above the solid‐solid transition a small residual concentration of all‐trans sequences was detectable.
Water effects on the zwitterionic polymerization of cyanoacrylates
Authors: Eromosele Ighodalo C. , Pepper David C. , Ryan Bernard
Published: April 2003

This paper presents a number of qualitative and semi‐quantitative observations on the effect of small concentrations of water on the polymerizations of butyl cyanoacrylates by tertiary amines in THF. It reports also that, in the absence of other bases, large concentrations (approx. 1 mol/l) of water can cause the polymerization of ethyl cyanoacrylate, in THF, even in presence of normally inhibiting amounts (10−5 mol/l) of p‐toluenesulfonic acid. A formal kinetic scheme of a stationary‐state polymerization, initiated by hydroxyl anions, is presented and discussed.
Monoplanar small angle neutron scattering by semicrystalline polymer solids containing homogeneously distributed otherwise identical deuterated polymer molecules
Authors: Peterlin A.
Published: April 2003

The first “linear” range of inverse reduced scattering intensity of N stems in monodisperse clusters versus q2 with the initial slope R/2 is followed by a second nearly 20% steeper and 10 times wider quasi‐linear range. The difference slightly decreases with polydispersity of the clusters. This case will not be discussed here. One may deduce from the second range the fictive number N of stems and gyration radius Rcc which differ less than 10% from the true values obtained from the first “linear” range. But the fine structure of the equal monoplanar clusters on the scattering molecule may change enormously with interior gaps while keeping constant the scattering intensity in the interesting region, N and Rcc of the cluster. In the sensitive range of the first two quasi‐linear ranges all these 3 quantities are so little affected by the changes of fine structure that small angle neutron scattering (SANS) yielding N and Rcc does not permit any statement on these changes. The calculations of SANS results with some equidistant gaps which retain N and Rcc yield the same intensity distribution in the interesting range. This follows from the fact that N commands the intensity while Rcc rules not only the first but also the second quasi‐linear range. The perfect merging of the first with the second quasi‐linear ranges in the SANS of polyethylene demands a special arrangement of a single gap separating one single stem from the bulk of the active stems in the cluster.
Cinnamic acid as a comonomer in radical polymerizations
Authors: Barson C. Anthony , Bevington John C. , Huckerby Thomas N.
Published: April 2003

Cinnamic acid affects the initiation processes when methyl methacrylate is polymerized at 60°C using benzoyl peroxide as initiator. Work with peroxide doubly‐labelled with carbon‐14 and tritium has shown that the balance between benzoate and phenyl end‐groups is significantly shifted in favour of ester end‐groups. On the other hand, study involving peroxide enriched with carbon‐13 has given no evidence for the presence in the polymers of benzoate end‐groups attached to units derived from cinnamic acid. It is proposed that the acid impedes the decarboxylation of the benzoyloxy radical. Cinnamic acid copolymerizes to some extent with styrene, methyl acrylate and acrylonitrile but less readily with the related monomers having a‐methyl groups. The effect of the nature of the diluent is clearly shown for the copolymerization with styrene; the presence in the polymerizing system of N,N‐dimethylformamide at quite low concentration causes appreciably less cinnamic acid to be incorporated than when bulk monomer or solutions of monomer in toluene are used.
Etude par 1H NMR des groupements chlorométhyles du poly(chlorure de vinyle), 1. Synthèse et étude de modèles moléculaires chloro‐4 chlorométhyl‐3 heptane et trichloro‐1,2,4 pentane
Authors: Doan Huynh Dong , Pétiaud Roger , Llauro‐Darricades Marie‐France
Published: April 2003

4‐Chloro‐3‐chloromethylheptane (2) and 1,2,4‐trichloropentane (3) were synthesized and analysed by means of 1H NMR. These compounds — with two asymmetric carbon atoms — are models for two types of structure involving chloromethyl groups present in poly(vinyl chloride): short chloromethyl branches and chain end groups resulting from reinitiation by a chlorine atom. The spectra of these compounds allow a better understanding of the corresponding resonance region observed in standard PVC.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 2. Controlled syntheses of 1,1,3‐trimethyl substituted polyindanes
Authors: Dittmer Thomas , Gruber Freddy , Nuyken Oskar
Published: April 2003

1,1,3‐Trimethyl substituted polyindanes were synthesized in the presence of Brønsted acids (H2SO4, CF3COOH) or Lewis acids (BCl3, AlCl3) using 1,4‐diisopropenylbenzene (1), 1,4‐bis(1‐hydroxy‐1‐methylethyl)benzene (2) or 1,4‐bis(1‐chloro‐1‐methylethyl)benzene (3) as monomers. The effects of experimental conditions on yields, molar masses and polymer structure were studied in detail with respect to monomer and initiator used, their concentrations, reaction time and experimental procedure. It was shown, that polymerization temperatures above the ceiling temperature and low monomer concentrations favour the formation of indane units. However, in particular the uniformity of the polymer structure is sensitive to the experimental conditions, mainly to the initiator and to the procedure used. DSC measurements on the polymers proved the remarkable heat‐resistance of polyindanes (Tdec. ≥ 450°C; Tg ≈ 210°C). The thermal properties were related to the polymer structure and were compared with those of some commercial polymers.
“Porcupine” polymers and double‐star polymers
Authors: Taromi Faramarz Afshar , Rempp Paul
Published: April 2003

Anionic block copolymerization of styrene and divinylbenzene is known to lead to the formation of star‐shaped macromolecules. This “arm‐first” method has been widely used and studied. The present paper is devoted to two special aspects of this method: The first is concerned with the efficiency of the protection exerted by the arms on the crosslinked core, preventing gelation of the reaction medium. A number of “porcupine” polymers involving bulky cores, fitted with a large number of arms, were synthesized and characterized. The second deals with the possibility of using the “living” carbanionic sites present in the cores, either for purpose of functionalization, or to grow new branches from the core. The presence of remaining unsaturations in the core was evidenced. This is a drawback, since the possibility for “transverse” bonds to be formed results in couplings, inducing gelation.
Synthesis and antitumor activity of chitosan carrying 5‐fluorouracils
Authors: Ouchi Tatsuro , Banba Toshio , Fujimoto Mitsuo , Hamamoto Shigeki
Published: April 2003

In order to provide a polymeric drug of 5‐fluorouracil (5FU) with reduced side‐effects, having affinity for tumor cells and exhibiting high antitumor activity, four kinds of chitosan derivatives were synthesized carrying 5FUs through some kinds of spacers via ether, amide, ester, or carbamoyl bonds. The release behaviors of 5FU and 5FU residues were studied in vitro at 37°C in various aqueous media. The antitumor activity was tested against p‐388 lymphocytic leukemia in female CDF1 mice in vivo by intraperitoneal injection of the polymeric drugs followed by intraperitoneal injection of the leukemia cells (i. p./i. p.). Chitosan fixing 5FU at 2‐position through a hexamethylene spacer and carbamoyl linkages (9) exhibits a higher effect with respect to prolongation of life than free 5FU. The chitosan‐5FU conjugates obtained do not display acute toxicity in the high dose range.
Synthesis, polymerization and copolymerization of a new organotin monomer. Application of a copolymer as catalyst for reductive dehalogenation of alkyl halides
Authors: Endo Takeshi , Kawamoto Hiroshi , Takata Toshikazu
Published: April 2003

A new organotin monomer, N‐[3‐(tributylstannyl)propyl]methacrylamide (5) was synthesized in 49% yield by hydrostannylation of acrylonitrile with tributyltin hydride and subsequent reduction of the resulting 3‐tributylstannylpropionitrile (3) with lithium aluminium hydride into 3‐tributylstannylpropylamine (4) which reacted with methacryloyl chloride to afford 5. Polymerization of 5 and copolymerization of 5 with styrene gave homopolymer 6 and copolymer 7, respectively. In a model study on the stability toward solvolysis, N‐(3‐tributylstannylpropyl)propionamide (8) showed no reactivity, whereas the corresponding ester derivative, 3‐tributylstannylpropyl propionate (9), easily reacted with ethanol to release the tin moiety. Monobromostannyl derivative 10, formed by the reaction of 7 with bromine, showed the catalytic activity in the reductive debromonation of dodecyl bromide with sodium borohydride under photoirradiation conditions at room temperature.
13C Nuclear magnetic resonance characterization of poly(propylene) prepared with homogeneous catalysts
Authors: Cheng H. N. , Ewen John A.
Published: April 2003

The minor resonances in the 13C NMR spectrum of poly(propylene) prepared with soluble Group 4 metallocene/methylalumoxane catalysts are fully characterized. The 13C shifts for regioirregular sequences, chain‐end structures, and 1,3‐propylene adduct are obtained for both isotactic and atactic components. In both components the dominating mechanism is 1,2‐insertion, with much lower amounts of 2,1‐insertion and 1,3‐insertion depending on the catalysts used. The isotactic component is stereoregular in all insertion modes. In the atactic components random stereosequences are observed. The regiostructures suggest that the propagation step is catalyticsite controlled even for the atactic component.
Polymerization by [3 + 2] cycloaddition, 3. Polyimides
Authors: Nuyken Oskar , Maier Gerhard , Burger Klaus , Albet Angels Serra i
Published: April 2003

The reaction between hexafluoroacetone azine and bis(bicyclo[2.2.1]hept‐5‐en‐2,3‐dicarboximide)s (5 and 6) (dinadimides) (mole ratio 1:1) yields polymers with number‐average molar masses between M̄n = 1700 and M̄n = 5700 depending on the reactants. The possible isomeric structures of the polymers are discussed in detail. From steric considerations which are supported by 13C and 19F NMR spectral data the number of realized isomers is reduced from sixteen to only three (12, 13 and 14). In contrast to these results, hexafluoroacetone azine and dimaleimides do not react to form polymers. This is explained on the basis of a spontaneous rearrangement of the primarily formed 1:1 adduct to 1 H‐pyrazolines.
Supported propene polymerization catalysts, 1. Supports derived from magnesium dialkyl‐sterically hindered aromatic ester complexes
Authors: Johnson Bryce V. , Karayannis Nicholas M. , Hoppin Charles R. , Ornellas Linda , Khelghatian Habet M.
Published: April 2003

New, highly active supported propene polymerization catalysts are prepared by activating supports derived from Mg dialkyl complexes with sterically hindered aromatic esters, such as ethyl 2,6‐dimethylbenzoate (6a), ethyl 2,4‐6‐trimethylbenzoate (7), or isopropyl benzoate (2b). The support is precipitated by reacting a hexane solution of the Mg dialkyl complex with SiCl4 and then activated by treatment with TiCl4 and diisobutylphthalate in chlorobenzene. Optimized catalysts of this type prepared from Mg dialkyl complex with 7 realize yields of 16–17 kg polypropylene/g catalyst in 2 h hexane slurry polymerizations at 70°C, 10,2 atm, with less than 1% boiling hexane extractables and 0,41–0,43 g/ml polymer powder bulk density. The cocatalyst‐external modifier package used consists of Al(C2H5)3‐dimethoxydiphenylsilane. The polymer produced is characterized by a narrow particle size distribution, which renders the title catalysts suitable for use in both slurry and solventless propene polymerization processes.
Molecular design for missile drug: Synthesis of adriamycin conjugated with immunoglobulin G using poly(ethylene glycol)‐block‐poly(aspartic acid) as intermediate carrier
Authors: Yokoyama Masayuki , Inoue Shohei , Kataoka Kazunori , Yui Nobuhiko , Okano Teruo , Sakurai Yasuhisa
Published: April 2003

Synthesis of a novel conjugate of anticancer drug adriamycin, poly(ethylene glycol)‐block‐poly(aspartic acid), and immunoglobulin G is reported. Poly(ethylene glycol)‐block‐poly(aspartic acid), binding adriamycin on the poly(aspartic acid) chain, showed an excellent water‐solubility despite the introduction of a large amount of strongly hydrophobic adriamycin, and was found to form a micellar structure in aqueous solution. Efficient coupling between poly(ethylene glycol)‐block‐poly(aspartic acid) binding adriamycin and immunoglobulin G was achieved via disulfide linkages.
Reductive transformations, 12. Poly(9,10‐anthrylenetrimethylene) as an efficient electron acceptor
Authors: Bender Dietmar , Przybylski Michael , Müllen Klaus
Published: April 2003

Poly(9,10‐dihydroanthrylenetrimethylene) (2) comprises a novel chain‐type structure in which 9,10‐dihydroanthracene units are linked by flexible spacer groups. Upon dehydrogenation with sulfur at elevated temperature, polymer 2 is converted into the corresponding polyanthrylene system 3. NMR‐ and UV‐spectroscopic data provide firm evidence for the dehydrogenation process. The polymer 3 was subjected to reduction with active lithium, and the resulting polyanions were characterized by NMR spectroscopy and by quenching experiments. It appears that each anthracene unit of the chain can be charged with two electrons.
Photosensitive polymers bearing iminooxysulfonyl groups. A water soluble positive‐type photoresist
Authors: Shirai Masamitsu , Katsuta Nobuyuki , Tsunooka Masahiro , Tanaka Makoto , Nishijima Kanji
Published: April 2003

Photosensitive polymers were synthesized by the copolymerization of 4‐(9‐fluorenylideneiminooxysulfonyl)styrene (1) with 2‐dimethylaminoethyl methacrylate (2), 2‐diethylaminoethyl methacrylate (3), or methacrylic acid (4). On irradiation with UV light the decomposition of monomeric units of 1 (A) in the polymers led to the formation of sulfo groups in their side chain. Although the quantum yield of photodecomposition of units A was found to be independent of the fraction of units A in the copolymers, it is dependent on the polymer structure in the film. Effects of the fraction of units A in the copolymers and of the polymer structure on the photoinduced dissolution of the polymers in water were studied.
Polymerization initiated by the redox system hydrogensulfite/oxygen, 1. Polymerization of acrylic acid
Authors: Igarashi Tadashi , Kondo Akihiro , Tsushima Rikio , Aoki Shuzo
Published: April 2003

The polymerization of acrylic acid in water by the redox initiation system hydrogensulfite/oxygen was found to proceed fast to give oligomers in high yield, in spite of introducing a large amount of oxygen known as a strong radical inhibitor. In the polymerization system, the concentration of oxygen was kept at a very low level on account of the rapid reaction of hydrogensulfite with oxygen. At high concentration of hydrogensulfite, both hydrogensulfite oxidation rate (Rox) and polymerization rate (Rp) vary with the flow rate of air. Rp is proportional to the square root of Rox, suggesting that the termination is a bimolecular reaction, a radical intermediate formed from hydrogensulfite oxidation being the initiator of this polymerization system. Hydrogen was found to behave as a chain transfer agent, and its chain transfer constant is 0,15 at pH 6,9 and 25°C.
Synthesis an characterization of polyanhydrides containing amido groups
Authors: Hartmann Manfred , Schulz Volker
Published: April 2003

4,4′‐Alkane‐ and oxaalkanedioyldiiminodibenzoic acids (3a–e) were prepared from 4‐aminobenzoic acid and various alkanedioyl and oxaalkanedioyl chlorides (2a–e). A series of polyanhydrides having both hydrolytically labile anhydride linkages and anilide units (4a–k) was prepared by polycondensation of the diacids 3a–k at 150–170°C via acetic mixed anhydrides, using different methods. Molecular weights, glass transition temperatures, and solubilities of the polyanhydrides were found to be dependent upon the reaction conditions and the structure of the monomers used. The highest molecular weight (Mn = 12400) was obtained by thermal polycondensation of isolated acetic mixed anhydride prepolymers formed on the reaction of the diacids 3b, 3c, and 3i with acetic anhydride.
Macromonomers of acrylates by group transfer polymerization
Authors: Witkowski Reiner , Bandermann Friedhelm
Published: April 2003

Bifunctional initiators for group transfer polymerization (GTP) were prepared, substituted by a vinyl, 2‐propyl, isoprenyl (2‐methylene‐3‐butenyl) or 4‐vinylphenyl group at the ketene acetal CC double bond. All initiators initiated GTP of methyl methacrylate in tetrahydrofuran with tris(piperdino)sulfonium bifluoride or tetrabutylammonium cyanide as catalysts to yield macromonomers with low polydispersities. It is recommended to perform GTP as the first step, since the silyl groups of the initiators give side reactions with active species of other polymerization systems. Macromonomers from isoprenyl ‐ or 4‐vinylphenyl‐substituted initiators could be radically copolymerized with styrene to yield graft copolymers. The copolymerization of acrylic macromonomers derived from the other two initiators has yet to be established.
Bifunctional initiators for group transfer polymerization
Authors: Steinbrecht Karin , Bandermann Friedhelm
Published: April 2003

Bifunctional initiators of group transfer polymerization (GTP) were prepared in which two silyl ketene acetal groups are linked by an oligomethylene bridge, either at their CC double bond or at their alkoxy groups. Their bifunctionality was proven for polymers of methyl methacrylate (MMA) prepared with initiators of the latter type in tetrahydrofuran (THF) with tetrabutylammonium cyanide, (C4H9)4NCN, as catalyst. Hydrolysis after complete conversion of monomer yielded chains exhibiting only half of the molecular weight of the original polymer. GTP of MMA with the new initiators in THF with (C4H9)4NCN is “living”, as could be established by the increase of number‐average molecular weights after repeated monomer addition, providing the opportunity of production of ABA block copolymers of MMA and acrylates.
Group transfer polymerization of methyl methacrylate and methyl acrylate in tetrahydrofuran with tris(piperidino)sulfonium bifluoride as catalyst
Authors: Schubert Walter , Sitz Hans‐Dieter , Bandermann Friedhelm
Published: April 2003

Group transfer polymerization of methyl methacrylate and methyl acrylate with (1‐methoxy‐2‐methyl‐1‐propenyloxy)trimethylsilane and (1‐methoxy‐1‐propenyloxy)trimethylsilane as initiators, respectively, and tris(piperidino)sulfonium bifluoride as catalyst in tetrahydrofuran as solvent was investigated. While the former system nearly behaves like a living system, in the latter system side reactions between the active centres and the catalyst are of greater importance and limit monomer conversion in some cases. The character of the side reactions could be revealed by NMR and GC/MS measurements. Number‐average molecular weights and polydispersities, as determined by gel permeation chromatography, show that tailoring of polymers with definite chain lengths and relatively narrow molecular weight distributions is only possible in the methyl methacrylate system. Reaction rates were proven to be very high, even at very low catalyst concentrations. Therefore, with respect to isothermicity in an industrial reactor, tris(piperidino)‐sulfonium bifluoride seems to be too active as catalyst in group transfer polymerization.
Haloaldehyde polymers, 34. 1H and 13C NMR spectra of chloral oligomers prepared by lithium tert‐butoxide initiation and the assignment of the meso/racemo addition products of the dimers
Authors: Hatada Koichi , Ute Koichi , Nakano Tamaki , Vass Frantisek , Vogl Otto
Published: April 2003

1H and 13C NMR spectra of the mixture of chloral oligomers prepared by initiation with lithium tert‐butoxide were examined in detail. 1H and 13C NMR signals due to meso and racemo diastereomers of the dimer fraction were unequivocally assigned through the 13C‐1H COSY spectrum and the 13C NMR spectra with low‐power selective 1H‐decoupling. The two‐dimensional NOESY spectrum showed correlation peaks between the signals due to the methine (acetal) protons of the neighbouring chloral monomeric units of the most abundant isomers in the trimer and tetramer fractions. The 1H NOE enhancements and 3JCH coupling constants were measured for the dimers; the results confirmed the meso/racemo assignments based on earlier conformational analysis.
Investigation of the aminolysis of p‐nitrophenyl esters of (meth)acryloylaminophenoxyacetic acids and their copolymers with N‐(2‐hydroxypropyl)methacrylamide by 6‐aminopenicillanic acid
Authors: Solovskij M. V. , Ulbrich K. , Nazarova O. V. , Zubko N. V. , Panarin E. F. , Kopeček J.
Published: April 2003

Copolymers of N‐(2‐hydroxypropyl)methacrylamide with p‐nitrophenyl esters of (meth)acryloylaminophenoxyacetic acids were prepared and characterized. The aminolysis of monomeric and polymeric p‐nitrophenyl esters by 6‐aminopenicillanic acid was studied. The aminolysis rate was structure‐dependent. Acryloyl derivatives were more reactive than methacryloyl derivatives. In both cases, the ortho‐derivatives were more reactive than the para‐derivatives. This phenomenon can be explained by the formation of an intramolecular hydrogen bond in the ortho‐derivatives. The synthetic methods studied are suitable for the binding of biologically active compounds containing an aliphatic amino group to polymeric carriers.
Structural studies on chitosan and other chitin derivatives
Authors: Grant Stuart , Blair Hal S. , McKay Gordon
Published: April 2003

Chitosan films were prepared by casting from solutions in dilute acetic acid containing methanol, acetone, or dimethyl sulfoxide. Induced changes in the structural orientation of the molecules within the film were studied by wide angle X‐ray diffraction, and it was shown that the presence of a high concentration of organic solvent in solution altered the crystal structure of the resultant films, rendering them insoluble in water. Benzoylated and butyrylated derivatives of chitin and chitosan were prepared and characterised by infrared spectroscopy. Films of these derivatives were prepared by casting from a number of organic solvents and water, and the structures examined in more detail by wide angle X‐ray diffraction. The introduction of the aliphatic and aromatic groups to the polysaccharide backbone was thus shown to disrupt the natural orientation of the polymer chains; the solubility of the acylated derivatives is discussed with respect to these structural changes.
Synthesis and characterization of phthalocyaninatocobalt (II) covalently bound to polyorganosiloxane
Authors: Nemoto Nobukatsu , Asano Makoto , Asakura Tetsuya , Ueno Yukihiko , Ikeda Koji , Takamiya Nobuo
Published: April 2003

Polyorganosiloxane containing phthalocyaninatocobalt(II) in the side chain (PCPMSTACo(II)Pc) (4) was synthesized from poly[(3‐carboxypropyl)methylsiloxane] (PCPMS) (1) and 2,9,16,23‐tetraaminophthalocyaninatocobalt(II) (TACo(II)Pc) (3). The wavelength of maximum absorption of TACo(II)Pc in PCPMS‐TACo(II)Pc in solution of N,N‐dimethylformamide (DMF) is shifted depending on the polymer environment. From UV/VIS spectra of PCPMS‐TACo(II)Pc, most of the phthalocyanine moieties in PCPMS‐TACo(II)Pc may be expected to exist monomeric in methanol as well as in DMF. The glass transition temperature (Tg) of PCPMS‐TACo(II)Pc is high compared with that of PCPMS and the maximum Tg is 50°C. Further, the formation of a crosslinked film is reported, and in this film most of the phthalocyanine moieties may be expected to exist dimeric as concluded from the UV/VIS spectrum. This dimer formation and intramolecular bridges between TACo(II)Pc and carboxyl groups are considered to influence Tg, because they reduce the mobility of the main chains.
Photo‐oxydation de résines phénoliques
Authors: Rivaton Agnès , Lemaire Jacques
Published: April 2003

Analytical and kinetic aspects of photo‐oxidation in the solid state of phenolic resins (phenolformaldehyde polycondensates) are described. On the basis of Fourier‐transform infrared analysis it should be noted that resins contain, in addition to methylene‐bridged structures, ether linkages (CH2OCH2) between aromatic structures. Photochemistry of the phenolic resins involves two primary processes. Photolysis of the phenolic groups leads to the formation of quinone methide structures and photo‐oxidation of the dimethylene ether linkages to hydroperoxy groups which are photo‐ and thermo‐unstable. These hydroperoxy groups are converted into ester and formate groups.
Investigations on the decomposition of lateral perester groups in maleic anhydride copolymers
Authors: Steinert Volker , Rätzsch Manfred
Published: April 2003

The reaction of maleic anhydride (MAn) copolymers with tert‐butyl hydroperoxide results in copolymers with lateral perester and carboxyl groups. As these copolymers are of interest as initiators of free‐radical polymerization, their decomposition mechanism and their decomposition constants were investigated. Surprisingly, a dependence of the decomposition constants on the comonomer of MAn was found. The interaction of the carboxyl group with the perester group is discussed as an essential reason of the comonomer influence.
Dehydrochlorination in crystalline structures of commerical poly(vinyl chloride)
Authors: Behnisch Jürgen , Zimmermann Heinz
Published: April 2003

The polyene formation during degradation of a commercial suspension‐polymerized poly(vinyl chloride) (PVC) in the solid state is discussed with respect to the PVC texture. Above the glass transition temperature (Tg), the polyene length distribution is characterized by a high amount of very short polyenes (conjugation length i < 6) due to the dehydrochlorination in the amorphous phase, and a second population of longer polyenes (i about 14) due to dehydrochlorination in micellar (B‐type) crystals. According to the melting range of these crystals (120–180°C), the formation of longer polyenes reaches a maximum at 120°C. A third population of polyenes could be observed investigating the thermal and photolytical degradation of PVC below Tg. The absorption spectra of the degraded samples show a maximum centred at 550 nm (i = 21) due to the dehydrochlorination in the highly ordered lamellar (A‐type) crystals. This result verifies the existence of highly syndiotactic sequences in commercial PVC formed during the first stage of polymerization, as demonstrated recently. The preferential dehydrochlorination in these crystals during the initial stage of degradation of PVC below Tg should be considered when discussing the long term stability of PVC products.
Synthesis and characterization of 2‐acetoxybenzoic acid‐dextran ester conjugates
Authors: Sánchez‐Chaves Manuel , Arranz Félix , Díaz Carmen
Published: April 2003

This work deals with the modification reaction of dextran with 2‐acetoxybenzoyl chloride (acetylsalicyloyl chloride) using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. Transesterification reactions were observed when 4‐dimethylaminopyridine or pyridine were used as catalysts, with the formation of acetoxy, 2‐hydroxybenzoyloxy (salicyloyloxy) and 2‐acetoxybenzoyloxy (acetylsalicyloxy) groups. When triethylamine was used as catalyst, only acetylsalicyloyloxy groups were found to be grafted onto the polymer chain. A linear dependence of the reaction rate on the concentrations of polymer, acetylsalicyloyl chloride and triethylamine was found. The activation energy was found to be 13,8 kJ/mol.
TiCl4/MgH2‐supported Ziegler‐type catalyst system, 1. Determination of active centres
Authors: Jaber Isam A. , Fink Gerhard
Published: April 2003

Determination of active centres using TiCl4/MgH2‐supported catalyst system in ethylene polymerization is reported. A radio‐tagging technique, whereby 14CO is used to label the polymerization active centres, is employed. Optimization of the 14CO/Ti ratio showed that the polymer radioactivity remained constant after a 14CO/Ti ratio of about 8 was attained. At the optimal 14CO/Ti ratio, it is found that up to 14% of the titanium on the catalyst surface are active in polymerizations at 40°C, 10 min reaction time, and 30 min contact time period of 14CO with the polymerization medium. Moreover, the value of the corresponding propagation rate constant, Kp, was found to be about 230 dm3/(mol·s).
Alignment processes in a smectogenic side‐chain liquid‐crystal copolymer
Authors: Kozak Andrzej , Moura‐Ramos Joaquim J. , Simon George P. , Williams Graham
Published: April 2003

The dielectric properties of the siloxane side‐chain liquid‐crystal (LC) copolymer 1 were investigated using high‐frequency techniques. The copolymer could be aligned homeotropically either by cooling from the melt with the aligning electric field on or by application of the field whilst the sample was in the LC state. Using the latter method the kinetics of the homeotropic alignment process could be determined. Samples of different purity were used and the kinetics and steady‐state properties compared and a strong dependence on polymer purity was found in both cases. Fuoss‐Kirkwood deconvolution of the relaxation peaks allowed examination of the fundamental motion of the mesogenic units.
Effects of ionenes on structure and catalytic activity of cobaltphthalocyanine, 5. The catalytic role of cobaltphthalocyanine aggregates
Authors: van Welzen Joke , van Herk Alex M. , German Anton L.
Published: April 2003

The interaction of several ionenes with tetrasodium phthalocyaninatocobalttetrasulfonate (1) was investigated spectrophotometrically, both in the unreduced and reduced state. The 2,10‐ and 2,12‐ionenes 2d, e appeared to induce monomerization of the phthalocyanine moiety, especially of the reduced form which is ascribed to hydrophobic effects. All other ionenes studied strongly induced aggregation of the cobalt complex. Kinetic thiol oxidation experiments revealed large differences between the macromolecular effects of the hydrophobic 2,10‐ionene 2d and the hydrophilic ionenes. These phenomena are explained by the different catalytic activity of phthalocyanine in its monomeric and aggregated form.
On the probability of the existence of periodical substructures in cellulose
Authors: Stoll Manfred , Fengel Dietrich
Published: April 2003

Linters cellulose was degraded in an inert and water‐free atmosphere using thermic and ultrasonic energy. The fragments were nitrated and fractionated by precipitation. A mathematical analysis of the degree of polymerization (DP) values of the differential and individual fractions resulted in a common denominator of 40 for all DPs of degraded celluloses. Also, the value of 120 occurs very frequently. Similar results were found for a series of 33 industrial pulps and some other celluloses. The smallest units in higher molecular‐weight celluloses are multiples of 40 or 120 in the range of 360 to 720. The results and the calculations of this study suggest that preformed substructures obviously exist in the cellulose of higher plants which are independent of the origin of the cellulose. The sizes of the resistant substructures seem to be independent of the kind of degradation applied.
Poly(vinylsaccharide)s, 5. Synthesis and characterization of poly(vinylsaccharide)s of the amide type with disaccharides in the side chain
Authors: Klein Joachim , Begli Alireza Haji
Published: April 2003

The synthesis of well‐defined monovinylsaccharide monomers containing disaccharide units is described. Four different monomers, N‐disaccharide‐substituted acryl‐ and methacrylamides, were prepared and polymerized to the corresponding polymers by free‐radical polymerization in aqueous solution using different initiator systems. The influence of the structural differences of the disaccharide units on the solution properties was studied by viscosity and light scattering measurements. A comparison with known poly(vinylsaccharide)s with monosaccharides in the side chain is made.
Crystallization and thermal behaviour of blends of isotactic polypropylene and hydrogenated oligo(cyclopentadiene)
Authors: Martuscelli Ezio , Silvestre Clara , Canetti Maurizio , de Lalla Claudia , Bonfatti Anna , Seves Alberto
Published: April 2003

The crystallization and the thermal behaviour of thin films of isotactic polypropylene/hydrogenated oligo(cyclopentadiene) of low molecular weight (iPP/HOCP) are studied using optical microscopy and differential scanning calorimetry (DSC). The spherulite growth rate, the overall crystallization rate and the equilibrium melting temperature of iPP are decreased by the addition of HOCP to iPP. This leads to the hypothesis that iPP and HOCP form a miscible blend in the amorphous phase. This hypothesis is also supported by the detection of a single blend‐composition‐dependent glass transition temperature of each blend as determined by DSC.
Vinyl polymers containing amido and carboxyl groups as side substituents, 2. Thermodynamic and fourier‐transform infrared spectroscopic studies for the protonation of poly(N‐acryloylglycine) and poly(N‐acryloyl‐6‐aminocaproic acid)
Authors: Barbucci Rolando , Casolaro Mario , Magnani Agnese
Published: April 2003

Synthetic poly(N‐acryloylglycine) (poly[1‐(carboxymethylcarbamoyl)ethylene], 1a) and poly‐(N‐acryloyl‐6‐aminocaproic acid) (poly{1‐[5‐(carboxypentyl)carbamoyl]ethylene}, 1b) were studied in aqueous solution by thermodynamic (potentiometry, calorimetry) and Fouriertransform infrared (FT‐IR) spectroscopic methods. The values of the basicity constant (log K), calculated with the Henderson‐Hasselbalch equation, relative to the protonation of the carboxylate group, decreases with increasing degree of protonation (a), while the enthalpy changes are “real” for both polymers. The increased length of the lateral aliphatic chain causes a decrease in the polyelectrolyte effect and a greater entropy change ΔS° of protonation due to liberation of water molecules. At low pH the FT‐IR spectra reveal a strong band at 1 628 cm−1 for polymer 1b which does not occur in the spectra of polymer 1a. At this pH the more compact macromolecular structure of 1b may favour interactions among the amido groups of several monomeric units.
Spontaneous copolymerization of 1‐(2‐hydroxyethyl)aziridine with β‐butyrolactone, 14
Authors: Rivas Bernabé L. , Canessa Guido S. , Pooley Sonia A.
Published: April 2003

The copolymerization of 1‐(2‐hydroxyethyl)aziridine (1) as nucleophilic monomer with β‐butyrolactone (2) as electrophilic monomer without initiator in solution at 45°C was investigated. Copolymers were characterized by IR and 1H NMR spectroscopy. By elemental analyses it could be shown that their compositions depend on the monomer ratio in the feed. From the copolymer composition and 1H NMR spectra it was possible to suggest four probable copolymer structures.
Analysis of fluorinated polymers: Several approaches by wide‐line nuclear magnetic resonance
Authors: Lutringer Gilbert , Meurer Bernard , Weill Gilbert
Published: April 2003

Two different ways of analyzing the composition of insoluble, partly hydrogenated, partly fluorinated copolymers by NMR are described. The first relies on a quantitative comparison of 1H and 19F free induction decays, as observed in the solid state, with those of reference samples. The second relies on medium resolution spectra which can be achieved, thanks to the large scale of 19F chemical shifts, on softening of the samples at high temperature. A special probe working up to 400°C was built for this purpose. The two methods are in good agreement in the case of vinylidene fluoride (VF2)/tetrafluoroethylene (VF4) copolymers, leading to a determination of the rectivity ratios; the special usefulness of the second method is illustrated by the identification of a third comonomer in VF2/VF4 terpolymers.
UV‐induced polymerization of maleimides in solution
Authors: Aida Hiroshi , Takase Iwao , Nozi Takashi
Published: April 2003

Maleimide and N‐ethylmaleimide were irradiated in various solvents with a high pressure mercury lamp at 30°C. The polymerization of maleimides is promoted in the presence of hydrogen donating solvents such as tetrahydrofuran, 1,4‐dioxane, ethanol and basic solvents such as dimethylformamide, dimethyl acetamide, pyridine. ESR spectra suggest that a radical mechanism is responsible for the polymerization in the former solvents and an anionic mechanism in the latter solvents.
Graph theory of configurational and viscoelastic properties of polymers, 6. The square radii distribution functions of copolymer chains
Authors: Yang Yuliang
Published: April 2003

The general expression of square radii distribution functions for copolymer chains is derived in this paper. Particularly, the distribution function of the sum of two random orthogonal components, S, for cyclic AB alternate block copolymer chains is derived, and it can be reduced to the case of cyclic homopolymer chain when δ = mA/mB = 1.
Solution studies of chitosan 6‐O‐sulfate
Authors: Terbojevich Maria , Carraro Claudio , Cosani Alessandro , Focher Bonaventura , Naggi Anna Maria , Torri Giangiacomo
Published: April 2003

Commercial chitosan, and highly deacetylated congeners thereof, can be selectively and extensively sulfated at the O‐6 level. Either a 2:1 mixture of sulfuric and chlorosulfonic acid (Method I) or a pyridine‐SO3 complex, following protection of the 2‐NH2 and 3‐OH groups with copper ions (Method II), can be used. The properties of sulfated chitosan with different degrees of acetylation are studied at pH conditions which promote a polyampholyte structure. Light scattering and intrinsic viscosity ([η]) measurements of chitosan 6‐O‐sulfate with a degree of acetylation of 20%, prepared by Method II, indicate the presence of molecular and structural heterogeneity, probably due to ordered structures in highly acetylated regions of the parent chitosan. This hypothesis is confirmed by the NMR analysis of the fragments obtained by depolymerization with nitrous acid. The heterogeneity is not observable in compounds obtained by Method I and in highly deacetylated chitosan 6‐O‐sulfate. The [η] increase of the polyampholyte on decreasing ionic strength can be explained in terms of a more rigid conformation stabilized by electrostatic interactions between the sulfate groups and the protonated amino groups on neighbouring residues.
Structural chemistry of polymerizable monomers, 4. Crystal and molecular structure of N‐methyldimethacrylamide and its effects on the initial stage of solid‐state cyclopolymerization
Authors: Higuchi Taiichi , Kodaira Toshiyuki
Published: April 2003

The structure of N‐methyldimethacrylamide was solved by direct methods and refined to a discrepancy index (reliability factor) R = 0,055 and weighted discrepancy index Rw = 0,068. C9H13NO2, relative molecular mass Mr = 167,21, monoclinic, C 2/c, a = 11,882 (1), b = 8,130 (1), c = 10,079 (1) Å, β = 94,21 (1)°, V = 971,0 (1) Å3, Dcal (Z = 4) = 1,143, D obs = 1,16 Mg · m−3, μ(MOKa) = 0,087 mm−1, mp 364 K, colourless needle crystal by sublimation. The molecule has a crystallographic C2 symmetry. The shortest spacing between vinyl carbon atoms in the molecule is 2,908 (2) Å (C(3)…C(3′)). Planes of two intramolecular vinyl groups assume a dihedral angle of 40,6 (4)°. It seems that the location of the vinyl carbon atoms allows an intramolecular closure in the initiation process, that is, tail‐to‐tail cyclization as observed. The subsequent solid‐state reaction probably proceeds through dimerization predominantly along a plane near the (101) plane in the lattice.
Protection and polymerization of functional monomers, 14. Anionic living polymerization of 4‐[N,N‐bis(trimethylsilyl)‐aminomethyl]styrene and 4‐{2‐[N,N‐bis(trimethylsilyl)amino]ethyl}styrene
Authors: Suzuki Ken , Hirao Akira , Nakahama Seiichi
Published: April 2003

Anionic polymerization of 4‐[N,N‐bis(trimethylsilyl)aminomethyl]styrene (1) and 4‐{2‐[N,N‐bis(trimethylsilyl)amino]ethyl}styrene (2) were carried out at −78°C in tetrahydrofuran (THF)/pentane mixtures with butyllithium, oligo(α‐methylstyryl)lithium, oligo(α‐methylstyryl)potassium, and cumylpotassium. Polymerizations of 1 and 2 proceed without chain transfer and termination reactions to give stable “living polymers” when butyllithium or oligo(α‐methylstyryl)lithium are used as initiator. The resulting polymers have predictable molecular weights and narrow molecular weight distributions (ratio of weight‐ to number‐average molecular weights, M̄w/M̄n = 1,04–1,14). Under mild acidic conditions (pH 3–5 in THF/water), cleavage of the NSi bonds in the polymers is completely achieved to give well‐defined poly(4‐aminomethyl)styrene and poly[4‐(2‐aminoethyl)styrene]. The triblock copolymers of polystyrene‐block‐poly(1)‐block‐polystyrene and polystyrene‐block‐poly(2)‐block‐polystyrene are readily prepared in quantitative yields by sequential polymerization of styrene with living poly(1) or living poly(2).
The macrocycle ⇌ copolymer equilibrium in equilibrium copolymerization
Authors: Szymański Ryszard
Published: April 2003

The relationships describing the concentrations of macrocycles of any size and composition in copolymerization at equilibrium are derived. They allow, together with presented earlier equations, prediction of all features of copolymerization system at equilibrium, provided the corresponding equilibrium constants and initial conditions are known. In the Appendix the equation for the equilibrium constant of polymerization of a composed monomer is given.
Facilitation of quantitative estimation of the composition of starch‐iodine blue by specific precipitation
Authors: Pal Medini Kanta , Pal Prasun Kumar
Published: April 2003

The fact that potassium fluoride specifically and quantitatively precipitates the blue starch‐iodine complex from an excess of starch was used for the direct estimation of the composition of starch‐iodine blue for the first time. The result shows starch‐iodine blue to be extremely stable in nature and with a definite stoichiometry regarding starch, iodine and iodide, which is in good agreement with the result computed from X‐ray data obtained with cyclodextrin in place of starch. The mole ratio of starch monomeric units/iodine atoms was found to be 2,90 and the iodine/iodide ratio 4,28. The spectra of precipitated starch‐iodine blue dissolved in water are identical with those of the original starch‐iodine blue in the UV and visible regions. 1 M KF also quantitatively precipitates the adduct of starch‐iodine blue with the dye 1,9‐dimethyl‐methylene blue (DMMB), thus facilitating the estimation of starch‐iodine and the dye adduct.
Dielectric spectroscopy on liquid‐crystalline main chain polymers with crossing mesogens
Authors: Kresse Horst , Rötz Uwe , Lindau Jürgen , Kuschel Frank
Published: April 2003

A newly synthesized series of liquid‐crystalline main chain polymers with crossing mesogens is investigated using dielectric spectroscopy. The crossing mesogenic units are endowed with hexyl as well as with CN‐wing groups. We examined the change of mobility of these crossing segments with increasing spacer length in the main chain, the relaxation behaviour at the phase transition nematic‐isotropic and the temperature dependence of the absorption intensity. The main results are: there is an alternation of the dielectric relaxation times with respect to the length of the spacer in such a way that the molecular mobility is raised in case of an odd number of methylene groups in the spacer. The steps in the relaxation frequencies at the clearing temperatures are obviously due to a change in the short‐range order caused by the formation of the nematic structure. Owing to a strong dipol‐dipol interaction between neighbouring segments, a decrease of the absorption intensity with decreasing temperature was observed. Furthermore, apart from the low‐frequency absorption a high‐frequency relaxation process could be monitored.
Zum copolymerisationsverhalten des 1,3,5‐triacryloylhexahydro‐1,3,5‐triazins
Authors: Kerber Robert , Pöllmann Klaus , Samarian Heidi , Sluka Peter
Published: April 2003

Radical homo‐ and copolymerizations of 1,3,5‐triacryloylhexahydro‐1,3,5‐triazine (1) with methyl methacrylate (MMA), styrene (S) and a‐methylstyrene (MS) were investigated at 60°C in DMF, varying the total concentrations of the monomers as well as the contents of 1. The monomer reactivity ratios were evaluated using the copolymer composition obtained by elemental analysis, according to the Kelen‐Tüdős method applying the equation of Gibbs. The resulting values for the system 1/MMA, based on the concentration of the CC double bonds, are: r1 = 0,50, rMMA = 1,76 and for the system 1/S: r1 = 0,17, rS = 1,03. Furthermore, the double bond content of the copolymers was determined by thiophenol addition showing a significant variation with the overall monomer concentration in the reaction mixtures concerned. This fact has to be considered when calculating the real monomer reactivity ratios yielding in the case of the system 1/S the values r1 = 0,43 and rS = 0,41.
New initiators for group transfer polymerization. Triphenylphosphonium‐containing ketene silyl acetals
Authors: Shen Wei‐ping , Zhu Wei‐de , Yang Ming‐fa , Wang Lan
Published: April 2003

New initiators for group transfer polymerization (GTP), triphenylphosphonium‐containing ketene silyl acetals, were synthesized by addition of triphenylphosphine and chlorotrimethylsilane to methyl acrylate or methyl methacrylate, respectively, giving 3‐methyoxy‐3‐trimethylsiloxy‐2‐propenyltriphenylphosphonium chloride (4a) and its 2‐methyl substituted derivative (4b), together with their corresponding oligomers (8). These phosphonium salts initiate GTP of ethyl acrylate using zinc halides as catalysts. The resulting polymers, containing a terminal triphenylphosphonium group, show a small polydispersity. In the presence of zinc halides, triphenylphosphine and chlorotrimethylsilane can be used directly to initiate GTP of acrylates and methacrylates. In this case triphenylphosphonium terminated polymers with a larger polydispersity are obtained.