bluuebunny/crossref_metadata_2025 huggingface dataset:
Soluble poly(divinylbenzene): Reaction mechanism for the anionic polymerization of divinylbenzene with lithium diisopropylamide as catalyst
Authors: Nagasaki Yukio , Ito Hiromi , Tsuruta Teiji
Published: April 2003

This paper presents results of the studies on the mechanism of initiation, propagation and chain transfer reactions in the recently found polymerization of 1,4‐ and/or 1,3‐divinylbenzene (DVB), initiated with lithium diisopropylamide/diisopropylamine. Initiation was confirmed to take place by addition reaction of the alkylamino group to the DVB molecule. The population of the triad tacticity of the soluble poly(DVB) suggested the steric course of the polymerization to proceed according to Bernoullian statistics with respect to the diad placements, m and r. The chain transfer reaction was found to take place via the free amine, the chain transfer reactivity of a primary amine being higher than that of a secondary amine. Comparative studies on the reactivity and selectivity of sodium diisopropylamide toward styrene and DVB were also carried out with respect to lithium diisopropylamide as reference.
Anionische polymerisation von ω‐isocyanatocarbonsäuretrialkylsilylestern
Authors: Mormann Werner , Schwabe Annelene , Sikora Regina
Published: April 2003

ω‐Isocyanatopropionic and ‐butyric acid trialkylsilyl esters are converted to polyisocyanates by means of anionic polymerisation. Polymeranalogous reactions (hydrolysis, transesterification) of the silyl ester groups are possible though being limited by the occurrence of depolymerisation at elevated temperatures.
Properties of ring‐shaped polymer coils. Theoretical calculation and experimental determination of hydrodynamic parameters for ring‐shaped and linear polymer coils
Authors: Huang Jiaxian , Li Chunroung , He Binglin
Published: April 2003

Based on the ratio between the intrinsic viscosities of ring‐shaped and linear polymers [η](R)/[η](L), the relationships are deduced between the corresponding equivalent radii of coils req.(R)/req.(L), sedimentation coefficients at zero concentration S0(R)/S0(L), diffusion coefficients at zero concentration D0(R)/D0(L), friction coefficients F(R)/F(L), molecular weights from Svedberg's equation MSD(R)/MSD(L), and Flory‐Krigbaum‐Mandelkern‐Scheraga invariant β(R)/β(L). The experimental verification has been conducted with ring‐shaped polystyrene samples obtained by anionic polymerization of styrene with sodium naphthalene (sodium dihydronaphthylide) according to the multistep reaction of Hild, Kohler and Rempp.
Preferential adsorption of swollen polydimethylsiloxane (PDMS) networks and of linear PDMS in 2‐butanone/cyclohexane
Authors: Masegosa Rosa M. , Gómez‐Antón M. Rosa , Horta Arturo
Published: April 2003

Measurements of preferential adsorption, λ(ν), by differential refractometry, and of swelling equilibrium, ν3−, of polydimethylsiloxane (PDMS) networks were carried out in the solvent mixture ethyl methyl ketone (MEK) + cyclohexane (Ch), at 25°C. The preferential adsorption and the total sorption were also determined, by light scattering, for linear PDMS in the same mixed solvent. The behaviour of the system crosslinked PDMS/MEK + Ch is compared with that of the system linear PDMS (dilute solution)/MEK + Ch. The experimental values of ν3and λ are compared with those predicted by thermodynamic theory. For this comparison, new thermodynamic equations, to calculate preferential and total sorption at finite polymer concentration, are derived using the extended Flory‐Huggins model. The derived equations take into account the solvent composition dependence of interaction parameters, neglected (as an approximation) in previous works.
Polymer crystallinity and morphology in polysiloxanes. poly(tetramethyl‐p‐silphenylenesiloxane) and poly(tetramethyl‐p‐silphenylene/dimethylsiloxane) copolymers
Authors: Magill Joseph H.
Published: April 2003

The crystallinities of polysiloxane homo‐ and copolymers, measured by DSC and checked by X‐ray measurements, are presented. A wide range of crystallization conditions and molecular weight fractions were investigated. The morphological implications of crystallinity changes as a function of molecular weight are discussed in regard to other physical parameters. It is concluded that the dependence of crystallinity and X‐ray long period on molecular weight is in accord with a defect interface created via chain entanglements primarily, which are trapped during crystallization. The morphology of the specimens directly reflects their preparative history and molecular weight.
New phospholiposaccharides as model glycoconjugates. Synthesis and structural study
Authors: Santarelli Xavier , Douy André , Gallot Bernard
Published: April 2003

New phospholiposaccharides OT‐6‐DPPE and OT‐2‐DPPE were synthesized by linking the α‐amino function of the asparagine residue of the glyco‐amino acid OT from hen ovotransferrin (that contains only Man and ClcNAc residues) to the primary amino group of the polar head of 1,2‐dipalmitoylphosphatidylethanolamine (DPPE) via a suberoyl or a succinoyl bridge. The structural study by X‐ray diffraction showed that the phospholiposaccharide OT‐6‐DPPE exhibits a lamellar structure in concentrated aqueous solution and in the dry state at room temperature; in this lamellar structure, the paraffinic chains are crystallized, hexagonally packed, and tilted as in the Lβ, structure of synthetic phospholipids, while the saccharidic chain adopts an “Y‐shaped conformation”, A comparison with the previously synthesized liposaccharide OT‐16, formed by the same glyco‐amino acid OT but linked to palmitic acid and exhibiting a cubic structure in which the saccharidic chain adopts a slightly deformed “T‐shaped conformation”, shows that it is possible to induce a conformational change of the saccharidic chain of hen ovotransferrin by changing the nature of the “hydrophobic moiety” linked to the saccharidic chain.
Interpenetrating polymer networks based on castor oil, 1
Authors: Patel Mayur , Patel Raman , Suthar Bhikhu
Published: April 2003

Liquid prepolyesters (PPE) were obtained from castor oil and dibasic acids, viz. oxalic, malonic, succinic, glutaric, adipic, suberic and sebacic acids. All these prepolyesters were subsequently copolymerized with acrylamide by radical polymerization initiated with benzoyl peroxide. The resulting prepolyester (PPE)/polyacrylamide (PAm) interpenetrating polymer networks (IPN's) were characterized by elemental analyses, solubility behaviour, IR spectral study, differential scanning calorimetry and thermogravimetry. The transition behaviour was analyses for one IPN by the Ozawa and the Kissinger methods for calculating the various kinetic parameters.
Polymères porteurs de dérivés du glycérol, 5. Dérivés de la progestérone
Authors: Soutif Jean‐Claude , Ouchatar Lahcen , Couvret Denis , Brosse Jean‐Claude
Published: April 2003

Glycerol was used as a very suitable compound to prepare reactive derivatives of aldehydes and ketones allowing reaction with polymerizable groups such as methacryloyl chloride. By radical polymerization of methacryloyl derivatives of acetals, synthesized from glycerol and progesterone or its models, polymers were obtained bearing on each constitutional unit a drug covalently linked by two types of bonds which can be cleaved by hydrolysis.
Studies on syntheses and permeabilities of special polymer membranes, 63 Active transport of adenine through cation exchange membranes with carboxyl groups
Authors: Uragami Tadashi , Moriyama Koichi , Yamamoto Makoto , Sugihara Mizuho
Published: April 2003

When a cation exchange membrane, prepared from poly(isobutylene‐alt‐maleic anhydride) and poly(vinyl alcohol), is fixed in a diaphragm type cell with one side of the solution being adjusted to be alkaline and the other one acidic, a metal ion is always actively transported from the alkaline side to the acidic side, but adenine is actively transported in symport or antiport with metal ions. The transport mechanism of these metal ions and of adenine is discussed in detail.
Cis/trans reactivity ratios in the ring‐opening polymerization of bicyclo[2.2.1]hept‐2‐ene; the nature of the propagating species in olefin metathesis
Authors: Greene Ruth M. E. , Hamilton James G. , Ivin Kenneth J. , Rooney John J.
Published: April 2003

The olefinic regions of the 13C NMR spectra of numerous ring‐opened polymers of bicyclo[2.2.1]hept‐2‐ene (norbornene) having cis double bond contents in the range σc = 0,32–0,86, have been analysed in detail. At least six peaks are resolved corresponding to olefinic carbons defined in terms of the double bond sequences tcc, tct + ccc, cct, ttc, ctc + ttt, ctt; for polymers of intermediate cis‐content tct and ccc are also resolved. The relative intensities of the cis‐centred triads may be accounted for in terms of a single parameter, rc, derived from the observed dyad probabilities. The relative intensities of the trans‐centred triads, however, show that at higher cis‐contents, the sequence cttc occurs with greater frequency than expected, requiring interpretation in terms of two trans‐parameters, rtt and rtc. These results show that the generally noted feature of cis/trans blockiness at moderately high cis‐content is sometimes associated with the presence of three kinetically distinct propagating species rather than two. The first is postulated to be the highly cis‐directing olefin‐metal‐carbene complex 4 in which the previously formed cis double bond remains coordinated to the metal centre; this may have both chiral and achiral forms. The second and third are postulated to be isomeric species formed by decoordination of the previously formed trans double bond from the metal centre but in which the initial ligand geometry is governed by the nature of the penultimate double bond: 3tc and 3tt are postulated to have permanent ligands with square pyramidal and octahedral symmetry, respectively. It is shown how the present results and those from related work may be rationalised in terms of this hypothesis.
Studies on the β‐form of isotactic polypropylene, 1. Characterization of the β‐form and study of the β‐α transition during heating by wide angle X‐ray diffraction
Authors: Zhou Gui‐en , He Zhi‐qun , Yu Jian‐min , Han Zhe‐wen , Shi Guan‐yi
Published: April 2003

The conditions for the formation of the β‐form of isotactic polypropylene in the presence of a β‐nucleator and the β‐α transition during heating were studied by wide angle X‐ray diffraction. A conditional crystallinity of the β‐form, X′β, and a structural disorder parameter, S, deduced from WAXD data were defined for the characterization of the β‐form in addition to the K value. The results show that X′β and S obviously depend on the content of β‐nucleator, and that the β‐α transition during heating essentially consists in the melting of the β‐form and the successive recrystallization to the α‐form.
Studies on the β‐form of isotactic polypropylene, 2. The melting behavior of predominantly β‐form samples
Authors: Shi Guan‐yi , Huang Bin , Cao You‐hong , He Zhi‐qun , Han Zhe‐wen
Published: April 2003

Effects of crystallization conditions, heating rate, and isothermal annealing on the melting behavior of isotactic polypropylene samples with predominantly β‐form were studied by differential scanning calorimetry. The results show that the β‐form of these samples has a higher thermal stability and a lower recrystallization ability to the α‐form after melting than the β‐form of other samples.
Synthesis of networks in solution, 2. Influence of the primary molecular weight on the kinetics of crosslinking
Authors: Stadler Reimund , Freitas Liane L. De Lucca , Jacobi Marly Maldaner
Published: April 2003

The kinetics of the crosslinking reaction of 4,4′‐[methylenebis(1,4‐phenylene)]‐di‐1,2,4‐triazoline‐3,5‐dione with polybutadienes of narrow molecular weight distribution was studied. At high conversions deviations from the kinetic scheme of a series of first order reactions was observed. The deviations were analyzed by introducing a “retardation” function which includes all informations on the changes in the reaction kinetics. The retardation function was calculated from the experimental data and depends on the polymer concentration and the primary molecular weight. The onset of the deviations in the kinetic behaviour is correlated to the local segment concentration which was calculated assuming unperturbed dimensions of the coils in the semidilute state. Sterical hindrances in the formation of the transition state complex in the gel appear to be of main importance for the observed results.
Decomposition of 18‐crown‐6 solutions in tetrahydrofuran containing dissolved potassium
Authors: Jedliński Zbigniew , Stolarzewicz Andrzej , Grobelny Zbigniew
Published: April 2003

Dipotassium polyoxaalkane‐α,ω‐diolates (1–5) and ethylene were found to be formed in the decomposition reaction of solutions of 18‐crown‐6 in tetrahydrofuran containing dissolved potassium. A mechanism of that decomposition process due to the action of the potassium anion is proposed.
Synthesis of 3′,5′‐bis(morpholinomethyl)‐4′‐hydroxy‐ and 3′,5′‐bis(4‐methyl‐1‐piperazinylmethyl)‐4′‐hydroxymethacrylanilide. Copolymerization and metal ion binding properties of monomers and copolymers
Authors: Ritter Helmut , Rodewald Stephan
Published: April 2003

4′‐Hydroxymethacrylanilide was modified by Mannich reaction with morpholine/formaldehyde and 1‐methyl‐piperazine/formaldehyde, respectively. The interaction of the resulting monomers 3 and 4 and their corresponding copolymers with acrylamide (5 and 6) with Cu2 + ions was studied by photometric methods. Incorporation of the aminomethylated phenol derivatives 3 and 4 in an acrylamide‐methylene diacrylamide network system was performed to yield a product which selectively adsorbs Cu2+ in the presence of Ni2+, Co2+, Cd2+ and Ca2+ ions.
Synthesis of homologues of deoxyribouridylic acid in preparative amounts using the triester method
Authors: Schott Herbert , Biedersee Heidereich v. , von Sonntag Clemens , Schulte‐Frohlinde Dietrich
Published: April 2003

The homologous oligodeoxyribouridylic acids dU2, dU4, dU8and dU16were chemically synthesized in amounts of 70 to 800 mg by block condensation using the phosphotriester method. The partially protected hydroxyl and phosphate components were condensed without any protection for the nucleobase uracil, using a mixture of 2,4,6‐triisopropylbenzenesulfonyl chloride and tetrazole in anhydrous pyridine as condensing agent. Demonstrable side reactions of the uracil residue occur under this condensation conditions. However, this undesired derivatisation of uracil residues is totally eliminated by a simple deamination of the deblocked oligodeoxyribouridylic acids. After synthesis, cleavage of the protecting groups and column chromatographical fractionation using QAE‐Sephadex, the oligodeoxyribouridylic acids were deaminated and obtained as pure products, as was positively evidenced by “fingerprints”.
Molecular design of multicomponent polymer systems, 13. Control of the morphology of polyethylene/polystyrene blends by block copolymers
Authors: Fayt Roger , Jerome Robert , Teyssié Philippe
Published: April 2003

As investigated by optical and electron microscopy, the observed morphology of the meltblended polyethylene/polystyrene pair unambiguously supports the interfacial activity of poly(hydrogenated butadiene‐b‐styrene) copolymers. The phase size is significantly reduced, the interfacial adhesion is dramatically increased and the phase dispersion is firmly stabilized against coalescence during subsequent processing. Diblock copolymers with a balanced composition are the most efficient interfacial agents in such an extent that only small amounts (1–2 wt.‐%) are required to obtain homogeneous and stable phase dispersions. The emulsification concept applied to melt‐blended immiscible polymers appears to be a powerful technique to prepare valuable polymer alloys.
Characterization of cellulose ethers by 13C NMR, 1. Studies of high molecular weight polymers in solution and in the solid state
Authors: Hjertberg Thomas , Zadorecki Pawel , Arwidsson Margareta
Published: April 2003

Carbon‐13 NMR was used to investigate the structure of a cellulose derivative, ethyl‐O‐(hydroxyethyl)cellulose (EHEC). Analysis of high molecular weight samples in solution showed that the line widths of the main chain carbon resonances are very sensitive to the concentration of the solution. Above a certain concentration, excessive broadening occurs due to gel formation, which makes a quantitative evaluation of the degree of substitution difficult. If the concentration is decreased below the critical value for gel formation, the use of NMR parameters suitable for quantitative measurements (no NOE and long pulse intervals) leads to excessively long accumulation times. Spectra of solid samples obtained by cross‐polarization magic angle spinning (CP‐MAS) NMR exhibit better defined resonances of the main‐chain carbons than do the spectra of solutions with concentrations above the critical value for gel formation. Variable contact time experiments with a specific sample indicated that a suitable contact time should be 400 μs. The quantitative evaluation of the total degree of substitution by CP‐MAS NMR yielded values in agreement with those obtained by GC‐analysis.
The homopolymerization of 2,3‐dimethyl‐1,3‐butadiene and the copolymerization of 1,3‐butadiene/2,3‐dimethyl‐1,3‐butadiene using the catalyst system AlEt2Cl‐Co(acac)2. A structural investigation of the products
Authors: Cabassi Franco , Italia Salvatore , Giarrusso Antonino , Porri Lido
Published: April 2003

The homopolymerization of 2,3‐dimethyl‐1,3‐butadiene with the catalyst system AlEt2Cl‐Co(acac)2 affords polymers consisting of about 81% cis‐1,4‐units and 19% 1,2‐units. The copolymerization of 1,3‐butadiene/2,3‐dimethyl‐1,3‐butadiene using the same system is of the ideal type and the composition of the copolymers is practically identical with that of the monomer mixture. The structure of the copolymers depends on their composition. The butadiene units, which are more than 95% cis‐1,4 in the homopolymer, become partially 1,2 in the copolymers; their amount increases with increasing dimethylbutadiene content. Conversely, the fraction of dimethylbutadiene units with 1,2‐structure decreases in the copolymers with increasing butadiene content. In the copolymers containing more than 50% of butadiene, the dimethylbutadiene units are practically all cis‐1,4. The analysis of sequence distribution shows that the 1,2‐butadiene units in the copolymers are not randomly distributed but are mostly adjacent to dimethylbutadiene units. The results obtained with dimethylbutadiene are compared with those reported for the homopolymerization of isoprene and the copolymerization of isoprene/butadiene using the same catalyst system.
Complex formation of polyampholyte with proton‐accepting polymers through hydrogen bonding
Authors: Abe Koji , Hasegawa Mutsuko , Senoh Saburo
Published: April 2003

Polyampholytes, copolymers of methacrylic acid and 2‐dimethylaminoethyl methacrylate [C(MA‐AM)x] of various composition, were synthesized. Their isoelectric points (pI) are in the range 5 < pH < 7. Undissociated methacrylic acid residues in the copolymers can interact with ether oxygens of poly(ethylene glycol) (PEG) and ketone groups of poly(N‐vinyl‐2‐pyrrolidone) (PVPo) in the acidic pH region through hydrogen bonding. However, only copolymers having more than about 60 mol‐% of methacrylic acid residues form complexes with PVPo and high molecular weight PEG. The composition of the obtained complexes is 1:1 (mole ratio of methacrylic acid residues of the copolymer to repeating units of PVPo and PEG).
The monomer content of polymers from bis(hydroxyethyl) terephthalate
Authors: Elias Hans‐Georg
Published: April 2003

The monomer content in polymers from bis(hydroxyethyl) terephthalate was previously found by Challa to be up to 63% higher than predicted by the classic equations of Flory. A reexamination shows that the apparent anomaly is caused by the approximative nature of the Flory equations which neglect the molar mass of the leaving molecules. Comparison of the experimental data with the predictions of the rigorous theory lowers the difference between experiment and theory significantly. The remaining differences scatter too much to allow any conclusions about a molar mass dependence of equilibrium or rate constants.
DNA protonation at low ionic strength of solution
Authors: Sorokin Victor A. , Gladchenko Galina O. , Valeev Vladimir A.
Published: April 2003

UV differential spectroscopy and thermal denaturation were applied to investigate the protonation of native (6 °C) and denatured (70 °C) DNA at 10−3M of Na+ in the range of pH 7,0 to 3,85. A decrease in the pH was found to deteriorate the thermal stability of DNA and to narrow the range of the helix‐coil transition due to preferential destabilization of G + C pairs. The pH dependence of the degree of helicity for native DNA is non‐monotonic and agrees with the protonation model proposed by Courtois et al. The proton binding to the bases is anticooperative for native DNA and noncooperative for denatured DNA. The ionization of the bases is characterized by pK′ = 4,7 for helical and by pK′ = 5,2 for coil DNA.
Reversible copolymerization at equilibrium
Authors: Szymański Ryszard
Published: April 2003

The relationships for copolymer composition and microstructure in reversible copolymerization at equilibrium are derived. They allow to predict the comonomer equilibrium concentrations and the structure of the copolymer at equilibrium if the initial state and equilibrium constants are known and provided that [I] ≪ [M1]0 + [M2]0 ‐ [M1]e ‐ [M2]e.
Polymerization of propene in the presence of MgCl2‐supported Ziegler‐Natta catalysts, 2. Effects of the co‐catalyst composition
Authors: Busico Vincenzo , Corradini Paolo , De Martino Luigi , Proto Antonio , Albizzati Enrico
Published: April 2003

As a part of a study on the polymerization of propene in the presence of MgCl2‐supported catalysts, new results were obtained when polymerizing at variable ethyl benzoate (EB)/alkylaluminium and alkylaluminium/Ti mole ratios. The pre‐treatment of MgCl2 with the Lewis base is essential to achieve high stereoregularities without an unacceptable decrease of polymerization rate, apparently because it prevents the formation of nonstereospecific active sites of low Lewis acidity, which require high EB/alkylaluminium mole ratios in the co‐catalyst in order to be poisoned. The data may be explained in the framework of a model of catalytic sites preliminarily presented in Part 1 of this series.
Liquid crystalline polyesters with 1,4‐cyclohexylene units
Authors: Braun Dietrich , Schülke Ulrike
Published: April 2003

A new series of liquid crystalline polyesters (5a – f) containing 1,4‐cyclohexylene dibenzoate moieties as mesogenic units in the main chain was prepared and characterized. The rigid segments in the polymers are connected by α,ω‐alkanedioyl units containing 4–8 or 10 methylene groups.
Properties of polyelectrolyte complexes containing poly(N‐tert‐butylaziridine)
Authors: Kabanov Victor A. , Zezin Alexander B. , Rogacheva Valentina B. , Grishina Nadajda V. , Goethals Eric J. , Van de Velde Marleen
Published: April 2003

Interpolymer reactions between poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA) and poly(N‐tert‐butylaziridine) (PTBA) were studied and compared with the corresponding reactions of these polyacids with linear polyethyleneimine (LPEI). In aqueous alkaline and salt media the presence of the bulky non‐polar N‐substituent in the main chain of PTBA results in a decrease of stability of polyacid‐PTBA polyelectrolyte complexes. LPEI, which forms stronger salt bonds with PAA, substitutes PTBA in the PAA‐PTBA polyelectrolyte complexes. Addition of simple salts to aqueous solutions of non‐stoichiometric polyelectrolyte complexes (N‐PEC) PAA‐PTBA and PMAA‐PTBA at room temperature causes a phase separation due to macromolecular exchange and disproportionation reactions. At elevated temperatures (T = 40 ‐ 60 °C), however, the macromolecular exchange between different N‐PEC particles does not occur and phase separation in aqueous salt solution of the N‐PEC's PAA‐PTBA, PMAA‐PTBA is not observed. This is attributed to hydrophobic interactions in polyacid‐PTBA complexes due to the presence of the tert‐butyl groups in the latter.
Influence of various apolar groups in polycationic polyorganosiloxanes upon polyion complexation with poly(methacrylic acid)
Authors: Nozuyama Kiyoshi , Ueno Yukihiko , Kato Takashi , Sekine Yoshiro
Published: April 2003

Polyion complexes are formed from poly(methacrylic acid) and polycationic polyorganosiloxanes modified with various apolar groups in the main chain or in the side chains. Potentiometric titration measurements with solutions of the complexes indicate that the chemical structure of the composed polycation influences complexation in aqueous solution. From a binding study with methyl orange, it is seen that the electrostatic interaction of the polyion complexes is enhanced by an increase of the hydrophobicity in the composed polycations. In water/ethanol solutions, however, such a tendency is not observed.
Polymerization of α‐olefins in the presence of δ‐TiCl3/Al(CH3)3: Chain propagation rate constants for ethylene and propene
Authors: Ammendola Paolo , Zambelli Adolfo , Oliva Leone , Tancredi Teodorico
Published: April 2003

The chain propagation rate constants for the polymerization of ethylene and propene in the presence of δ‐TiCl3/Al(CH3)3 at 22 °C are determined by means of a 13C NMR analysis of suitable block copolymers. The numerical values of the rate constants are compared with those previously reported.
Electroinitiated polymerization of maleic anhydride
Authors: Pattanayak Nirmal K. , Nayak Bimbadhar
Published: April 2003

The electroinitiated polymerization of maleic anhydride was studied in N,N‐dimethylformamide medium using sodium acetate (saturated solution) as the electrolyte. A dark brown polymer is formed only after the passage of an electrical current. Its yield increases in the presence of the electrolyte and depends on several factors such as the magnitude of the current flow, the duration of the electrolysis, the temperature of the cell solution and the monomer concentration. Split‐cell experiments showed that the polymer is formed in the anode compartment from a red coloured precursor, which is generated in the cathode compartment, but subsequently migrates to the anode compartment. The IR spectrum suggests that the polymer is mainly a cis‐poly(vinyleneketoanhydride), containing also other moieties in the chain such as cyclopentanone and maleic anhydride.
Synthetic polymers containing sugar residues, 8. Novel polyureas from 2,6‐diamino‐2,6‐dideoxy‐d‐gulose and diisocyanates
Authors: Kurita Keisuke , Murakami Kaori , Kobayashi Koichiro , Takahashi Mitsunori , Koyama Yoshiyuki
Published: April 2003

A diamino monosaccharide, 2,6‐diamino‐2,6‐dideoxy‐D‐gulose (7), was prepared as a new difunctional sugar monomer with high reaction selectivity, to synthesize a new type of linear polyureas containing sugar residues in the main chain. As a result of a study of the polymerization conditions, the polymerization of the diaminogulose 7 with diisocyanates 8a‐d was successfully carried out in N,N‐dimethylacetamide or hexamethylphosphoric triamide without blocking the hydroxyl groups. The resulting polyureas 9a‐d show inherent viscosities in the range 0,16–0,62 dl · g−1 in dichloroacetic acid. Some properties were studied, including solubility and crystallinity.
Practical approach to termination kinetics in radical copolymerization
Authors: Chee Kam K.
Published: April 2003

A novel expression has been developed for the instantaneous rate of radical copolymerization, Rp, based on a combined form of the diffusion‐controlled and terminal models of copolymerization. This treatment introduces a characteristic parameter, θ, which can be correlated to the monomer feed composition, β, empirically. In this connection, two equations have been proposed for θ, to cope with the drastic change in the Rp versus β relationships when the θ values drop below unity. The validity of these two‐parameter formulations are positively tested by the rate data of a number of representative copolymerizations, including the ideal and alternating systems. It is found that the present approach to Rp is more practical, adaptable, and reliable than the other contemporary kinetic schemes of binary copolymerization reactions.
Dégradation contrôlée des polyisoprènes‐1,4 par le couple phénylhydrazine/oxygène, 3. Molécules modèles de structures phénylhydrazone conjuguées
Authors: Filho Eurico de Barros Lobo , Reyx Danièle , Campistron Irène , Casals Pierre‐François
Published: April 2003

In order to identify phenylhydrazone structures in the reaction products of oxidized polyisoprene or its models with phenylhydrazine, the UV, 1H NMR, 13C NMR and MS spectra as well as the steric exclusion chromatography parameters were determined for phenylhydrazones derived from aldehydes and ketones, selected as models of conjugated carbonyl structures, which could result from the oxidation of polyisoprene units. By comparison with possible coexistent structures, inclusively phenylhydrazones of non‐conjugated carbonyl derivatives, oxidized polyisoprene structures can be identified.
A novel synthesis of polystyrene macromonomers
Authors: Nagasaki Yukio , Tsuruta Teiji
Published: April 2003

Lithium diisopropylamide (2) was found to undergo a metalation reaction with 4‐methylstyrene (1) to form 4‐vinylbenzyllithium (3), but to induce neither addition reaction nor vinyl polymerization. The equilibrium constant between 2 and 3 in THF was calculated to be 0,54 at 20°C. The 4‐vinylbenzyllithium formed initiates the polymerization of styrene derivatives to form oligomers. The resulting oligomers have a polymerizable vinyl group at the chain end quantitatively and can be regarded as a “macromonomer”. Synthesis of polystyrene, having a primary amino group at the chain end, was carried out through the reaction of polystyrene macromonomer with N‐methylethylenediamine. More than 97% of polystyrene were aminated within 6 h reaction.
The copolymerization of maleic anhydride with propene and isobutene
Authors: Arnold Manfred , Rätzsch Manfred
Published: April 2003

Alternating copolymers were obtained by radical copolymerization of propene (Pr) and isobutene (IB) with maleic anhydride. Both polymers (Pr and IB) do not homopolymerize under the applied reaction conditions. The copolymerization rates were determined.
Kinetics of the copolymerization of styrene with maleic anhydride in ethyl methyl ketone
Authors: Chen Show‐An , Chang Gwo‐Yang
Published: April 2003

The copolymerization of styrene and maleic anhydride in ethyl methyl ketone as solvent and with benzoyl peroxide as initiator at 60–80°C in the entire feed composition range was studied. The resulting copolymers appear to have negative and positive deviations from alternation as determined by use of elemental analysis. The experimental data were found to fit a three‐reactivity‐ratio copolymer composition equation from the penultimate model. The inclusion of the reactivity ratio, kSM (=kSMM/kSMS), in addition to rSS (=kSSS/kSSM) and rMS (=kMSS/kMSM), allows prediction of a positive deviation from the alternation, i.e. the mole fraction of maleic anhydride in the copolymer being higher than 0,5.
Polylactones, 8. Mechanism of the cationic polymerization of L,L‐dilactide
Authors: Kricheldorf Hans R. , Dunsing Ruth
Published: April 2003

Various acidic compounds were tested as potential initiators of the cationic polymerization of L,L‐dilactide. Regardless of solvent and temperature only trifluoromethanesulfonic acid and methyl triflate proved to be useful initiators. With methyl triflate as initiator L,L‐dilactide polymerizes faster than diglycolide, whereas diglycolide is more reactive when anionic or complexing initiators are used. Initiation with methyl triflate yields poly(L‐lactide) with methyl ester endgroups indicating that the chain growth proceeds via cleavage of the alkyl‐oxygen bond. At polymerization temperatures > 100°C the resulting poly(L‐lactide) is 100% optically active indicating that the chain growth does not proceed via free carbenium ions, but via triflate ester endgroups. All attemps to identify cyclic dioxocarbenium ions as reaction intermediates failed, because propagation is much faster than initiation. However, in nitromethane oligomers with triflate ester endgroups were detected. For comparison the reaction of γ‐valerolactone with methyl triflate was studied by means of IR and 1H NMR spectroscopy. Methylation of the exocyclic oxygen yielding a cyclic dioxocarbenium ion was found to be the sole reaction.
Synthesis of a new antithrombogenic block copolymer containing fluorinated segments: poly(nonafluorohexyl acrylate‐b‐styrene)
Authors: Akemi Hitoshi , Aoyagi Takao , Shinohara Isao , Okano Teruo , Kataoka Kazunori , Sakurai Yasuhisa
Published: April 2003

Two types of block copolymers, 3a and 3b, were synthesized from α‐hydro‐ω‐(2‐hydroxyethylthio)poly[1‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyloxycarbonyl)ethylene] (1a) or α‐hydro‐ω‐(2‐aminoethylthio)poly[1‐(hexyloxycarbonyl)ethylene] (1b) and α,ω‐bis(4‐cyanatophenylthio)‐poly(1‐phenylethylene) (2), respectively, and the adhesion of blood platelets to these polymer surfaces was evaluated. Adhesion and activation of platelets were found to be effectively suppressed at the lamellar‐microdomain surface of block copolymer 3a, having a surface free energy gap between microdomains of about 20 dyn/cm, whereas no such a suppression was observed for the microdomain structured surface of block copolymer 3b with a small surface free energy gap between the microdomains. Further, a random copolymer from nonafluorohexyl acrylate and styrene without microdomain structure does not suppress the adhesion and activation of platelets. From these results, it was concluded that the microdomain morphology and the surface free energy gap between microdomain is important to produce antithrombogenicity.
Rheological properties of liquid‐crystalline side‐group polymers in the isotropic, nematic, and smectic states
Authors: Zentel Rudolf , Wu Jishan
Published: April 2003

The melt viscosity of seven liquid‐crystalline side‐group polymers with polyacrylate and polysiloxane main chains is measured as a function of shear rate and temperature. In the isotropic and also in the nematic phase none or only a very small dependence of the melt viscosity on shear rate is observed for the shear rates investigated. The melt viscosity in the nematic phase is higher than that in the isotropic phase. This is contrary to the results for liquid crystalline mainchain polymers and points to the fact, that there is no resulting orientation in shear flow of liquid‐crystalline side‐group polymers in the nematic phase. In the smectic phase the melt viscosity is very high and strongly shear‐rate dependent. These results are compared with dielectric relaxation measurements on polymethacrylates and a polychloroacrylate.
Dynamic mechanical behaviour and phase separation of mixtures of polysulfone with bis[4‐(4‐ethynylphenoxy)phenyl]‐sulfone or poly(phenylene sulfide)
Authors: Zeng Hanmin , Mai Kancheng
Published: April 2003

The dynamic mechanical behaviour and microphase‐separation structure of polysulfone blends with bis[4‐(4‐ethynylphenoxy)phenyl]sulfone and with poly(phenylene sulfide) were investigated using torsional braid analysis and scanning electron microscopy. The experimental results showed that the size and shape of dynamic mechanical damping peaks and the structure characteristics of polysulfone blends with sulfur‐containing polymers do not only depend on the chemical and physical nature and the weight fractions of the two components but also on conditions of thermal treatment leading to cross‐linking reactions. In these multi‐component polymer systems, the initially compatible mixture turns into an incompatible two‐phase system during heating.
Shrinkage force and molecular orientation in polyacrylonitrile fibers
Authors: Henrici‐Olivé Gisela , Olivé Salvador , Frushour Bruce G.
Published: April 2003

A correlation between sonic modulus and shrinkage force was found for fibers spun from copolymers of acrylonitrile and other vinyl monomers. Using this correlation, the orientation factor as defined by Moseley can be calculated from a single shrinkage force measurement, permitting a fast and reliable characterization of fibers and spinning conditions. Equipment and modus operandi are described.
13C NMR characterization of a new ethylene‐propene copolymer obtained with a high yield titanium catalyst
Authors: Abis Luigi , Bacchilega Giancarlo , Milani Federico
Published: April 2003

A detailed microstructural characterization of ethylene‐propene copolymers, obtained with a high yield Ti‐catalyst and showing elastomeric properties, was carried out by 13C NMR spectroscopy. These copolymers show no inversions in propene insertion, a tendency to form blocks of ethylene and propylene, and the presence of both isotactic and atactic blocks of propylene. Furthermore, in these polymers the reactivity ratio product (r1 · r2) and the experimental versus calculated triad distribution point to the presence of components which are heterogeneous with respect to the monomer distribution and composition. 13C NMR analysis of fractions, separated by hexane and ether, supports the above hypothesis.
Liquid crystalline elastomers based on liquid crystalline side group, main chain and combined polymers
Authors: Zentel Rudolf , Reckert Gertrude
Published: April 2003

Covalently crosslinked liquid crystalline networks with elastic properties were prepared in isotropic solution from linear liquid crystalline polymers. As linear precursors for the networks were used: (i) polymers with the mesogenic groups in the side groups (polyacrylates and polymethacrylates), (ii) polymers with the mesogenic groups in the main chain (polymalonates) and (iii) polymers with the mesogenic groups in main chain and side groups (“combined liquid crystalline polymers”). In all crosslinked polymers the liquid crystalline phases of the linear polymers are retained. For low degrees of crosslinking (≤2 mol‐%) the phase transition temperatures remain nearly unchanged. These elastomers are very soft above Tg and can be easily stretched for more than 100%. For higher degrees of crosslinking the phase transition temperatures are reduced.
Radical polymerization of methyl methacrylate and methyl acrylate in the presence of an oligomer of 2‐methoxy‐4‐vinylphenol
Authors: Ito Katsukiyo
Published: April 2003

Methyl methacrylate (MMA) and methyl acrylate (MA) were polymerized in the presence of an oligomer of 2‐methoxy‐4‐vinylphenol (OMVP) with a double bond at its end. It is shown by means of the UV spectra and the kinetic treatment that the double bond disappears by hydrogen transfer from the growing polymer chain to OMVP and that the OMVP radical formed propagates further. In the polymerization of MMA, the transfer rate is comparable with the termination rate if [OMVP] ≤ 0,52 mol · 1−1. In the polymerization of MA, the transfer rate is very much higher than the termination rate for [OMVP] ≥ 0,016 mol · 1−1. It is suggested that each PMA chain carries one OMVP unit at the end.
Exciplex laser‐induced polymerization of pure ethylene at high pressure
Authors: Brackemann Holger , Buback Michael , Vögele Hans‐Peter
Published: April 2003

Pure ethylene is photo‐polymerized with an exciplex laser on the KrF line (248 nm) at temperatures from 190°C to 230°C and for pressures up to 3 200 bar. The radical reaction is directly monitored via quantitative high‐pressure high‐temperature near infrared spectroscopy. Toward higher densities and temperatures, the overall quantum yield increases and up to several thousand ethylene molecules are polymerized by one absorbed laser photon. A kinetic scheme is presented which adequately describes the polymerization kinetics as a function of temperature, overall density, laser pulse energy, and conversion. Termination rate coefficient kt is found to decrease in the initial polymerization period, whereas a single value of kt is sufficient to represent kinetic data in the extended conversion range from 20% to 70%.
Influence des conditions de fusion et de cristallisation sur la morphologie superstructurale du polypropylène isotactique cristallisé au dessus de 130°C
Authors: Idrissi Mohamed Oulad Bouyahya , Chabert Bernard , Guillet Jacques
Published: April 2003

The morphology of polypropylene samples cooled from the melt and then isothermally crystallized above 130°C, was studied by optical polarization microscopy. If the temperature of the melt is raised above 175°C, the spherulitic superstructure is fully destroyed. Isothermal crystallization involves negative or positive birefringence which mainly depends on the temperature of crystallization (above or below 130°C). If the temperature of the melt is raised to 172°C, that is to say at a temperature at which no birefringence is detectable, isothermal crystallization leads to negative spherulites above 155°C and to positive ones below 155°C. If the melt is heated between 172°C and 175°C, crystalline lamellae are partially destroyed and they further lead to crystallization of small positive spherulites, which are located inside the initial spherulitic superstructure. These observations are explained in terms of a quadritic arrangement of the lamellae of crystallized polypropylene. Moreover, the crystallization temperature of 155°C appears as a true transition temperature beyond which tangential lamellae cannot exist; this always implies negative birefringence of the spherulites, whatever the melting conditions are.
Synthesis of high‐molecular‐weight polysuccinamides by polycondensation of active succinates with diamines
Authors: Katsarava Ramaz D. , Kharadze Darejan P. , Avalishvili Lamara M.
Published: April 2003

High‐molecular‐weight, film‐ and fiber‐forming polysuccinamides were synthesized by polycondensation of active diesters of succinic acid with hexamethylenediamine or dodecamethylenediamine under mild conditions. By kinetic investigations it was established that the formation of high‐molecular‐weight polysuccinamides is connected with a low rate of chain‐terminating formation of a cyclic imide and its nearly complete suppression by chain‐growth aminolysis reaction.
Precursors of hydrophilic polymers, 6. Preferential sorption of water on poly[2‐(dimethylamino)ethyl methacrylate] in ethanol/water mixtures
Authors: Přádný Martin , Ševčík Stanislav
Published: April 2003

The study deals with the kinetic behaviour of atactic and isotactic poly[2‐(dimethylamino)‐ethyl methacrylate] (PDAEM) and of low‐molecular‐weight tertiary amines in the quaternization by low‐molecular‐weight alkyl iodides (Mentschutkin's reaction) in water/ethanol solution at 60°C. Unlike quaternization of PDAEM with methyl iodide and 2‐iodoethanol, in the cases of the other alkyl iodides the rate constant of quaternization depends on the initial concentration of the alkyl iodide. The rate constant decreases with increasing concentration of the alkyl iodides. The effect becomes more pronounced in a reaction medium containing 43 wt.‐% of water in a mixture with ethanol as compared to azeotropic ethanol. Such behaviour is attributed to the fact that in solution of a water/ethanolic mixture the tertiary amines investigated in this study are preferentially solvated by water.
Nuclear magnetic resonance studies on polymer carbanions, 5. Polystyryl carbanion with lithium as counter cation and its dimer model compounds
Authors: Matsuzaki Kei , Ishihara Ken , Shinohara Yoshinao , Kanai Taiichi
Published: April 2003

Oligostyryllithium was synthesized by the reaction of sec‐butyllithium with styrene in diethyl ether at −40°C. Dimer model anions (counter cations: Li and K) of the growing chain ends were synthesized by metallation of 1‐methoxy‐1,3‐diphenylpropane. The structures of the lithium compounds were corroborated by 13C NMR spectroscopy and compared with those of the potassium compounds. As for polystyryllithium and its model compounds, the charge density on the α‐carbon increased and that on the phenyl ring of the growing end decreased with increasing molecular weight, while, in polystyrylpotassium and its model compounds, the charge density on the α‐carbon increased and the one on the phenyl ring did not change with increasing molecular weight. The temperature change of the 1H NMR spectrum of oligostyryllithium in diethyl ether indicated rotation around the C‐1Cα bond at lower temperatures than in tetrahydrofuran, but the activation energy was the same in both solvents. T1 values of the phenyl carbons in model compound 2b were one to two orders of magnitude shorter than those of the protonated compound.
Molmassenabhängigkeit der Geschwindigkeitskonstanten der Adsorption von Polybutylmethacrylat aus Cyclohexan
Authors: Wochnowski Horst , Dzeick‐Pickuth Astrid
Published: April 2003

The kinetics of adsoprtion of poly(butyl methacrylate) on iron powder from cyclohexane as solvent is determined by measuring the polymer concentration during adsorption for different molecular weights. There is an inverse relationship between the rate constant of adsorption k and the molecular weight of polymer. This corroborates theoretical results, which involve the quality of solvent: k ∼ 1/M2a where a is the Kuhn‐Mark‐Houwink exponent. Thus it is possible to determine the quality of solvent by investigations of adsorption using polymers of various molecular weight. Good coincidence with the a‐value received from viscosity data via the Kuhn‐Mark‐Houwink relationship is achieved in the case of cyclohexane.
On the entropy of single flexible polymer chains
Authors: Cifra Peter , Romanov Andrej
Published: April 2003

The existence of a new universal exponent λ in the expression for the number of possible configurations of a flexible self‐avoiding polymer chain is connected to the excluded volume in the chain and rationalized on the basis of loop exlcusion in stepwise growth, N→N + 1, of the chain consisting of N segments. An approximative analytical expression is given for λ. For three‐dimensional chains the theoretical expression gives the value of the exponent obtained from analysis of enumeration data on the number of self‐avoiding chains, while for twodimensional chains λ is underestimated.
Are there covalent active species in the polymerization of styrene initiated by trifluoromethanesulfonic acid?
Authors: Matyjaszewski Krzysztof , Sigwalt Pierre
Published: April 2003

Polymerization of styrene by perchloric and trifluoromethanesulfonic acids has been assumed previously to proceed via a pseudo‐cationic mechanism. We found that for the latter system the trifluoromethanesulfonate ester is not stable. Attempts to observe the model 1‐phenylethylester were unsuccessful even at −78°C. In the reaction between 1‐phenylethyl bromide and AgSO3CF3 a very rapid alkylation of the aromatic rings occurs. In the reaction between 1‐phenylethanol and (CF3SO2)2O a very rapid reaction between the intermediate ester (or ion) and the alcohol leads to the formation of the corresponding ether. A reaction carried out with the optically active alcohol indicates that no more than 4% of the intermediate species might have reacted with the alcohol as ester before racemization (i.e. ionization). The macromolecular ester does not seem to be much more stable and in 19F NMR spectra only the acid was observed. An attempt at the formation of a block copolymer with N‐tert‐butylaziridine give zero or very low yield, contrarily to results previously observed with perchloric acid. An analysis of some former results on polymerization kinetics and of the new data given in this paper show no real evidence in favor of the pseudo‐cationic polymerization of styrene in CH2Cl2, initiated by CF3SO3H. The various data may be explained more satisfactorily by a more classical ionic mechanism. Triflic acid can reversibly protonate olefins due to the affinity of the triflate anion being higher for a proton than for a secondary or tertiary carbon atom; this is sufficient to explain the extremely low concentration of ionic species.