bluuebunny/crossref_metadata_2025_split huggingface dataset:
Initiation of the polymerization of 1,3‐dioxolane by 2,4,5‐trisubstituted 1,3‐dioxolan‐2‐ylium salts, 1. Reaction of the initiator with the monomer. Model studies
Authors: Lukaszczyk Jan 
Published: April 2003

AbstractThe reaction of 2,4,5‐trisubstituted 1,3‐dioxolan‐2‐ylium salts with 1,3‐dioxolane results in the formation of the more reactive 1,3‐dioxolan‐2‐ylium salts monosubstituted in 2‐position and 4,5‐dimethyl‐1,3‐dioxolane. Values of the rate constants of this reversible reaction, which is supposed to precede the actual initiation process in the polymerization of 1,3‐dioxolane by trisubstituted dioxolenium salts, depend on the structure of the dioxolenium cations. Steric hindrances and positive charge delocalization effects due to the substituents in dioxolenium cations were found to reduce the rate of that reversible reaction. The trans‐isomers are less reactive than the respective cis‐isomers, while aromatic derivatives are less reactive than those with aliphatic substituents.
Polymeric prodrugs, 3. Synthesis, elimination, and whole‐body distribution of 14C‐labelled drug carrier
Authors: Azori Mária , Szinai István , Veres Zsuzsanna , Pató János , Ötvös László , Tüdős Ferenc 
Published: April 2003

AbstractAn alternating copolymer of 1‐vinyl‐2‐pyrrolidone and maleic anhydride, 14C‐labelled at the chain end, was synthetized with a mass‐average relative molecular mass M̄w = 8000. Elimination kinetics and whole‐body distribution of the copolymer in its monosodium salt form were studied in mice. Elimination of the copolymer was found to be fairly rapid and practically complete, i.e. 86,7% of it was excreted after 24 h and 95% after 56 h. Specific accumulation of the copolymer was observed in bone tissue and lacrimal gland. No appreciable accumulation occurred in the nervous system, spleen, and bone marrow. The results of elimination kinetics and the autoradiographic whole‐body distribution study were in fairly good correlation.
Polymeric prodrugs, 4. IN vitro study of the drug release on a model p‐nitroanilide bound onto polyanionic carrier
Authors: Azori Mária , Pató János , Fehérvári Flóra , Tüdős Ferene 
Published: April 2003

AbstractThe process of chymotrypsin catalysed hydrolysis of L‐phenylalanyl‐4‐nitroanilide (Phe‐NNp) residues bound via 6‐aminohexanoic acid (ϵ‐Ahx) spacer to the polyanionic carrier, poly(N‐vinylpyrrolidone‐co‐maleic acid), was studied. The initial rate of hydrolysis was measured at pH 8 as a function of mole ratio of side chains (‐ϵ‐Ahx‐Phe‐NNp) randomly distributed along the backbone. The polyanionic carrier studied shows a pronounced effect on the process, as overall kinetic parameters (kcat and Km) of ‐ϵ‐Ahx‐Phe‐NNp, attached to the polymer, differsignificantly from the respective values of the low‐molecular‐weight substrate analogue, succinyl‐ϵ‐Ahx‐Phe‐NNp. Relationship between the side chain content and the kcat/Km values, examined in the range of 1 to 20 mol‐%, exhibits a saturation‐profile. The limiting value of kcat/Km (5 · 103 1 · mol−1 · s−1) appeared to be as much as 8‐times higher than that of succinyl‐ϵ‐Ahx‐Phe‐NNp. The course of chymotrypsin catalysed hydrolysis of the polymer‐substrate bearing 20 mol‐% of side chains shows first order kinetics, with the conversion approaching asymptotically 100%. pH dependence of the maximum velocity of hydrolysis (Vm), determined in the range 5–10, shows a maximum at about pH 8. The enzyme activity profile is broadened toward acidic region.
Polymerization of ethylene with Cr[OC(CH3)3]4/Al(C2H5)2Cl as catalyst modified with some metal chlorides
Authors: Soga Kazuo , Chen Shian‐Ing , Shiono Takeshi , Doi Yoshiharu 
Published: April 2003

AbstractPolymerization of ethylene was carried out in toluene using the homogeneous catalytic system Cr[OC(CH3)3]4/Al(C2H5)2Cl, combined with various metal chlorides (MtClx). The polymerization activity was found to be strongly dependent upon the MtClx used. A clear correlation was found between the activity and the elctronegativity X(Mtx+) of the metal ion in MtClx. MtClx containing metal ions with X(Mtx+) < 8,5 (electronegativity of the active Cr2+) show a markedly increased activity, whereas those with X(Mtx+) > 8,5 have a rather decreased activity. Thus, for example, the catalyst combined with MgCl2 shows very high activity to give a linear polyethylene with a remarkably high molecular weight and narrow molecular weight distribution. A plausible mechanism for the enhancement of the activity by suitable MtClx is proposed on the basis of these results.
Investigation on the microstructure of poly(cyclohexyl α‐chloroacrylate)s using 500 MHz 1H and 25 MHz 13C NMR
Authors: Pathak Chandrashekhar P. , Patni Mahendra J. , Babu Gaddam N. , Chien James C. W. 
Published: April 2003

AbstractThe tacticity of poly(cyclohexyl α‐chloroacrylate) (PCCA) was studied by 500 MHz 1H and 25 MHz 13C NMR spectroscopy. The influence of the polymer configuration was observed at three different carbon resonances: The backbone methylene carbon, the carbonyl carbon and the quaternary carbon. Tetrad tacticities of PCCA measured from the resonance of the backbone methylene carbon were in good agreement with tetrad values obtained by 1H NMR. The polymer obtained was syndiotactic rich and obeyed Bernoullian statistics in its tacticity distribution.
Kinetics of polyamidation in solution, 1. Model reaction of monomers
Authors: Weißkopf Klaus , Meyerhoff Günther 
Published: April 2003

AbstractThe aminolysis of diphenyl terephthalate by means of hexylamine was studied in dimethyl sulfoxide as a model reaction for polyamidation. The kinetic analysis showed that the two ester groups of the diphenyl ester do not react independently. Furthermore, the reaction of the first ester group was of mixed second and third order, while the reaction of the second ester group contained only a second order term. The rate constants found were used to determine the Arrhenius activation parameters.
Black crazes — white crazes?
Authors: Gebizlioglu Osman S. , Cohen Robert E. , Argon Ali S. 
Published: April 2003

AbstractThe origin of the curious “inverted contrast” often observed in transmission electron micrographs of crazes in rubber‐toughened thermoplastics was determined by using scanning transmission electron microscopy with X‐ray fluorescence analysis. The “black crazes” seen in the micrographs contain high concentrations of osmium metal which is introduced through OsO4 used to stain the rubber phase. Treatment of stained sections with a strong oxidizing agent (NaIO4) removes a sufficient amount of osmium to reveal the commonly observed tufty craze microstructure with the expected contrast of light crazes in a darker background.
Acylation products of N‐acyllactams and their activation effect in the anionic polymerization of lactams
Authors: Stehlíček Jaroslav , Valter Bohumír , Šebenda Jan 
Published: April 2003

AbstractBenzoylation of metalated N‐benzoyllactams, derived from 7‐, 9‐ and 13‐membered lactams, gives rise to both N‐benzoylenol esters (1) and N,2‐dibenzoyllactams (3), whereas in the case of derivatives of 5‐ and 6‐membered lactams only products 3 by C‐acylation in position 2 were isolated. In the propionylation of N‐benzoyl‐ or N‐propionyl‐6‐hexanelactam, only products of O‐acylation were formed. The aminolysis of 3 gave rise to 2‐benzoyllactams (4). For selected compounds of type 1–4 the activation effect in the anionic polymerization of 6‐hexanelactam was found to be comparable with that of N‐acyllactams. The equilibrium acidities in DMSO were measured for 3 and 4.
Chain conformation and compatibility in polymer blends. A small‐angle X‐ray scattering study of the system poly(propylene glycol)‐poly(methyl methacrylate)
Authors: Macchi Edgardo M. , Liberman Susana A. , Gomes Ailton S. 
Published: April 2003

AbstractThe thermodynamic compatibility of dilute, solid solutions of poly(propylene glycol) (PPG) (mass‐average molar mass M̄w = 3900 g/mol) in poly(methyl methacrylate) (PMMA) (M̄w = 550000 g/mol) was investigated by means of small‐angle X‐ray scattering. The results of the analysis show that PPG is molecularly dispersed in the solid, amorphous matrix of PMMA, and that the molecules display the typical statistical coil macroconformation of polymers in dilute, liquid solution, whereby the numerical value of the second virial coefficient seems to point to the unperturbed nature of the coils. This behaviour, consistent with the concept of “interpenetration of segments”, is in total agreement with the experimentally measured compositional variation of the glass transition temperature of the blends.
Caractérisation et propriétés rhéologiques en milieu dilué et à l'état fondu des poly(téréphtalate d'éthylène)s linéaires et ramifiés
Authors: Langla Bernard , Strazielle Claude 
Published: April 2003

AbstractDilute solutions of linear and branched poly(ethylene terephthalate) (PETP) samples were investigated in various solvents (or mixed solvents) by osmometry, light scattering and viscometry. Branched PETP samples were obtained with the polyfunctional comonomers trimethylolpropane (functionality f = 3) and pentaerythritol (f = 4). For the branched samples, we determined the index of branching g' and compared the experimental results with polycondensation theory in order to estimate the average number of branches per molecule. Finally, the melt viscosity (at 290°C) of branched PETP was measured and compared with the melt viscosity of linear PETP.
Kinetics and mechanism of inhibition of an antioxidant type inhibitor in free radical vinyl copolymerizations
Authors: Chen Show‐An , Tsai Lii‐Chyuan 
Published: April 2003

AbstractInhibition mechanism and kinetics for an antioxidant type inhibitor, which can function only in the presence of oxygen, in the copolymerization of styrene and methyl methacrylate (MMA) are proposed. Experimental studies of the homopolymerizations with hydroquinone (HQ) and p‐tert‐butylpyrocatechol (TBC) as inhibitor at 50–70°C and of the copolymerization with HQ as inhibitor at 60°C show a good fit of the equations proposed and are self‐consistent, except for the homopolymerization system MMA/TBC, in which TBC can function also as an inhibitor even after the depletion of oxygen. The copolymerization system styrene (1)/MMA (2)/HQ shows a synergistic effect, positive for the rate of oxygen consumption and negative for the inhibition time. This can be attributed to the favored cross‐propagation of the peroxyl radicals, R1 O and R2 O, with the comonomers as indicated by the found reactivity ratios (both < 1; r1 = 0,275, r2 = 0,314). Detailed calculations using the proposed kinetic equations indicate that, if the cross‐propagation is not favored, the inhibition time will show a positive synergistic effect.
Equilibrium polymerization with reversible termination
Authors: Cai Gang‐feng , Yan De‐yue 
Published: April 2003

AbstractThree cases of equilibrium polymerization with reversible impurity termination or spontaneous termination were studied theoretically. The expressions for the molecular weight distribution function, the number‐ and weight‐average degrees of polymerization, and other molecular parameters were rigorously derived. The numerical results reveal that reversible termination has only a slight influence on the molecular weight distribution of the polymer formed under equilibrium conditions.
The acid‐catalyzed degradation of cellulose in the range of medium and low degrees of polymerization
Authors: Marx‐Figini Marianne 
Published: April 2003

AbstractThe acid‐catalyzed degradation of cotton cellulose with number‐average degrees of polymerization DPn < 2000 was studied, using a 0,5 M aqueous KHSO4 solution as degradation agent and applying throughout a degradation temperature of 60°C. The data obtained show, contrary to what happens for the same molecular weight range at 40°C, a systematic decrease of the reaction rate, the initial reaction rate being the lower, the lower the initial degree of polymerization. For DPn ≲ 350 a simultaneous decrease of the capability of the cellulose to form derivatives had been observed, manifesting itself in a systematic decrease of the ratio of the intrinsic viscosities of cellulose nitrate in acetone and of the unsubstituted cellulose in Cu‐ethylenediamine [η]./[η] with the time of degradation. The molecular weight distribution, as far as investigated, seems to retain the character of a most probable distribution also at very extended stages of the degradation. A preliminary hypothesis is put forward stating that beginning with a certain DPn going downwards supermolecular rearrangements may occur provoking a systematic decrease of the accessibility of the cellulose against degradation and also derivatization agents.
Microdomain control of block copolymers by epitaxy in mesophases
Authors: Ishizu Koji , Hayashi Takeo , Fukutomi Takashi 
Published: April 2003

AbstractPoly(vinyl alcohol(VA)‐b‐4‐vinylpyridine(4VP))s were prepared by mechanochemical scission of PVA in the presence of 4VP monomer under ultrasonic irradiation. After establishing the morphology of a particular specimen of these block copolymers, a solution of well‐defined poly(styrene(ST)‐b‐4VP), prepared by anionic living polymerization, was cast on the above mentioned specimen being used as a support membrane. It is shown that the microdomain structure of poly(ST‐b‐4VP) may be governed by epitaxial growth of the microdomain pattern of the support membrane surface.
Polymerization of allyl esters of unsaturated acids, 12. Cyclopolymerization of methyl 2‐methylallyl fumarate
Authors: Urushido Kunio , Iwasaki Fujiko , Matsumoto Akira , Oiwa Masayoshi 
Published: April 2003

AbstractThe kinetics of radical‐initiated cyclopolymerization of methyl 2‐methylallyl fumarate (MMAF) was investigated and compared with the polymerization results of allyl methyl fumarate (AMF). In the former, the extent of cyclization and five‐membered ring formation were enhanced. The cyclization constants KA and KV, the ratio of the rate constant of the unimolecular cyclization reaction to that of the bimolecular propagation reaction of the uncyclized 2‐methylallylic and fumaric radicals, were estimated to be 3,1 and 3,0 mol · dm−3, respectively. On the basis of these results the formation mode and the sequence distribution of the structural units of the polymer produced are discussed in detail; the low probability for fumaric vinyl addition and high probability for the succession of cyclic structures are calculated for poly(MMAF) as opposed to those of poly(AMF). The cyclopolymerizability and five‐membered ring formation are enhanced at elevated temperature. These results are discussed from the standpoint of the steric effect on cyclopolymerizability.
Anionic polymerization of fluorine‐containing vinyl monomers, 4. ‘Ate’ complex initiated polymerizations of fluoroalkyl acrylates and methacrylates
Authors: Narita Tadashi , Hagiwara Tokio , Hamana Hiroshi , Goto Masaru 
Published: April 2003

AbstractAnionic polymerizations of 2,2,2‐trifluoroethyl acrylate (1a), 2,2,2‐trifluoroethyl methacrylate (1b), 2,2,2‐trifluoro‐1‐trifluoromethylethyl acrylate (2a) and 2,2,2‐trifluoro‐1‐trifluoromethylethyl methacrylate (2b) were carried out with several ate complexes as initiators. LiZnC4H9(C2H5)2 was found to initiate the polymerization of methacrylates to produce the corresponding polymers in high yields. LiAlC4H9(C2H5)3 also showed appreciably high initiation reactivity for the polymerization of methacrylates. Ate complexes containing alkaline earth metals, except magnesium, were inactive for the polymerization of these four monomers. Polymers of 2a, which are generally not obtained with typical anionic initiators such as butyllithium or organomagnesium compounds, were produced with LiAlC4H9(C2H5)3 and MgZn(C2H5)4 as initiators, though the yield of the polymers was only 40%.
Multinuclear macromolecular metal complexes, 5. Synthesis of a binuclear copper schiff's base complex covalently bound to poly(vinylamine)
Authors: Kurose Akio , Masuda Etsuko , Hanabusa Kenji , Shirai Hirofusa , Hayakawa Tadao , Hojo Nobumasa 
Published: April 2003

AbstractA novel macrocyclic binuclear Cu(II) complex bound to poly(vinylamine) (PVAm) was synthesized by reaction of PVAm with N,N'‐trimethylene bis(3‐formyl‐5‐methylsalicylaldiminato)dicopper (2+) diperchlorate (2) in water/acetone. Polymers containing different amounts of complex repeating units were obtained by varying the amount of 2 in the reaction mixture. The polymer complexes are soluble in water and methanol. Light‐green colored films were obtained when cast from aqueous solutions. The coordination structure around the macrocyclic complex in the polymer was characterized by infrared and electronic spectroscopy. The Cu — Cu interaction of the binuclear complex on the polymer were also studied by means of ESR measurement.
Reversible immobilization of drugs on a hydrogel matrix, 1. Synthesis of unsaturated chloramphenicol derivatives and copolymerization with 2‐hydroxyethyl methacrylate
Authors: Meslard Jean‐Claude , Yean Leanirith , Subira Franck , Vairon Jean‐Pierre 
Published: April 2003

AbstractChloramphenicol (1) was immobilized on a hydrogel matrix through different bonds, slowly hydrolyzable at neutral pH. Methacrylic esters of 1 and its acetal derivatives were prepared and copolymerized with 2‐hydroxyethyl methacrylate. Reactivity ratios and change of copolymer composition with conversion were determined. Bar and disk shaped polymers could be obtained by radical copolymerisation in bulk, which remain colourless and keep their optical properties when swollen to equilibrium in water.
Polymerizable phospholipids and their polymeric liposomes
Authors: Takane Minoru , Shigehara Kiyotaka , Tsuchida Eishun 
Published: April 2003

AbstractPhospholipids containing polymerizable itaconate moieties were synthesized and their formation of liposomes was studied. Although the itaconate phospholipids alone form rather unstable liposomes by ultrasonication, mixtures with other phospholipids such as dipalmitoyl phosphatidylcholine, bis(2,4‐octadienoyl) phosphatidylcholine or cholesterol, form stable and single‐wall, small sized liposomes. The polymerizability of itaconate phospholipids and the stabilization of such mixed liposomes are discussed.
Ziegler‐type propene polymerization catalyst systems involving tributyl phosphite as modifier
Authors: Karayannis Nicholas M. , Khelghatian Habet M. , Lee Sam S. 
Published: April 2003

AbstractTributyl phosphite (1) was studied as modifier of heterogeneous TiCl3/(C2H5)2AlCl propene polymerization catalyst systems. When used as the sole modifier, 1 was found to produce catalyst systems with substantially improved stereospecificity and only slightly depressed activity relative to the unmodified catalyst system. Binary modifier packages consisting of 1 and bis‐(tributyltin) sulfide lead, apparently through synergism, to catalyst activities surpassing that of the unmodified catalyst system and to excellent stereospecificity (hexane extractables; 1,6–2,1%). Catalyst systems modified with 1 and triphenylantimony sulfide were also demonstrated to exhibit activities approaching or even exceeding that of the unmodified catalyst system with 2,1–2,3% hexane extractables, while systems involving 1 and triethyl thiophosphate as modifiers are more stereospecific (hexane extractables: 1,80%), but somewhat less active than the preceding system. Possible interactions and reactions of 1 with the components of the catalyst system are discussed.
Photo‐oxidation of poly(p‐hydroxystyrene)
Authors: Weir Neil A. , Farahani Moran 
Published: April 2003

AbstractThe oxidative and photo‐oxidative degradations of poly(p‐hydroxystyrene) were investigated. The polymer undergoes slow thermal oxidation at 100°C and photo‐oxidation on irradiation with UV (wavelengths > 290 nm). The principal manifestations of degradation are O2 absorption, formation of ketonic and quinoid species, colouration (which has been attributed to quinoid compounds) and embrittlement, associated with rapid cross‐linking. Since the pure polymer is stable at 100°C and does not absorb in the long‐wave UV region, it is proposed that the degradation is initiated by thermal and photo‐decompositions of impurities. The high transfer ability of the hydroxylic proton would appear to be the origin of the quinoid compounds, the resulting phenoxyl radicals also participating in cross‐linking reactions.
Heat interaction parameter of polystyrene solutions determined by inverse gas‐liquid chromatography
Authors: Inoue Keizo , Fujii Ryo , Baba Yoshihiro , Kagemoto Akihiro , Beatty Charles L. 
Published: April 2003

AbstractThe interaction between polymer and solvent in highly concentrated polymer solutions was studied by inverse gas‐liquid chromatography as a function of the molecular weight of polymer. The heat interaction parameter was estimated for the systems polystyrene(PS)‐benzene, ‐toluene, ‐pyridine, ‐ethylbenzene, and ‐anisole. It was found that the heat interaction parameter for the concentrated polystyrene systems PS‐toluene, PS‐pyridine, and PS‐benzene exhibits a similar behavior as in the dilute polystyrene solutions determined by calorimetry at 298,15 K. Further, the heat interaction parameter in both the concentrated and dilute polymer solutions is considerably dependent on the molecular weight of polymer.
Termination processes in free radical polymerization, 5,,. The numerical solution of a kinetic scheme with chain length dependent termination
Authors: Olaj Oskar Friedrich , Zifferer Gerhard , Gleixner Günther 
Published: April 2003

AbstractIn order to assess the general consequences of an eventual chain length dependence of the bimolecular termination rate constant kt in free radical polymerization, an iterative procedure for solving the kinetic scheme was developed for this case. The iteration process is based on the equation for the propagation probability of a radical chain of length x, αx, which constitutes a cyclic definition of the α‐values,

with F(x,y) giving the functional dependence of kt = k F(x, y) on the lengths x and y of the two radicals involved in the termination process. As, in addition, αx links the stationary concentrations of radicals of adjacent length, [Rx−1] and [Rx], solving for the set of αx allows to build up the complete chain length distribution of polymer radicals from which all relevant kinetic quantities may be calculated. The following types of functional dependence have been used in practice

The case of F2, which is the slightly less realistic one, allows to separate the variables x and y in the equation for αx, thus leading to an immediate comfortable solution. Irrespective of the type of F(x, y) chosen (the differences being quantitative in nature rather than qualitative) it can be shown that nearly all the familiar relationships known from “classical” polymerization kinetics with chain length independent termination (b = 0) break down. The new relationships, however, can be cast into comparatively simple power laws. The general consequences of the concept of chain length dependent termination are discussed in some detail.
Application of the composite model for the mechanical properties of high density polyethylene
Authors: Biswas Prabir K. , Sengupta Shyamal , Basu Asok N. 
Published: April 2003

AbstractThe existing models of high density polyethylene (HDPE) fail to tackle effectively the development of mechanical anisotropy on drawing at different temperatures. This paper is concerned with the theoretical interpretation of the anisotropic elastic properties of HDPE by applying the composite model proposed by the authors. The model takes into account the change in orientation and crystallinity on drawing. As far as the orientational changes on drawing are concerned, it is seen that the pseudo affine deformation law tan θ = ϕ(n) · tan θ′ with ϕ(n) = n−3/2 is applicable at −60°C only. It is further found that the two parameter analytical form of ϕ(n) reproduces the correct orientational changes on drawing for the entire temperature range from −60 to 100°C. The agreement of the calculated values of E0 and E90 over the entire temperature range at all drawing ratios is quite satisfactory.