bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of linear poly(4‐vinylbenzaldehyde) by means of anionic living polymerization of 1,3‐dimethyl‐2‐(4‐vinylphenyl)imidazolidine and subsequent hydrolysis
Authors: Hirao Akira , Ishino Yoshiaki , Nakahama Seiichi
Published: April 2003

Poly(4‐vinylbenzaldehyde)s (4) of known chain lengths and of narrow molecular weight distributions (M̄w/M̄n ≈ 1,1) were synthesized by means of anionic living polymerization of 1,3‐dimethyl‐2‐(4‐vinylphenyl)imidazolidine (1) with oligo[α‐methylstyryl]potassium (2) and subsequent acid hydrolysis to remove the imidazolidine protective group. The living polymer of 1 can initiate further polymerization of α‐methylstyrene, resulting in the preparation of a triblock copolymer of the type poly[α‐methylstyrene‐b‐(4‐vinylbenzaldehyde)‐b‐α‐methylstyrene] in quantitative yield after hydrolysis.
Generation of free radicals in poly(N‐vinylcarbazole) by thermal decomposition of peroxides
Authors: Hlouškova Zuzana , Szöcs František
Published: April 2003

Radicals of poly(N‐vinylcarbazole) (PNVC), generated by thermal decomposition of peroxides, were studied by ESR. Apart from the known cation radical on nitrogen, formed in the process of ion‐radical decomposition of dibenzoyl peroxide, a carbon radical is observed on the main chain. The radical is formed by homolytic decomposition of dicumyl peroxide and is observed only when the system is subjected to high pressure. The mechanism of peroxide decomposition and of formation of PNVC radicals is discussed.
Studies on carboxymethylcellulose: Conductivity measurements of solutions, 2
Authors: Trivedi Harikrishna C. , Patel Raman D.
Published: April 2003

The conductivity behaviour of carboxymethylcellulose (CMC) solutions was studied using different types of neutralizing reagents (LiOH, NaOH, KOH); the following order of conductance of CMC solutions was observed: Li+ < Na+ < K+. This conductance behaviour of CMC solutions with respect to the size of counterions is explained qualitatively as well as quantitatively. Binding of Li+, Na+ and K+ ions onto the polymer molecule and the influence of the degree of substitution, ,DS, on the conductivity of CMC were also investigated. The conductivity of CMC solutions as well as the fraction of bound counterions increase with increasing DS, at a given degree of neutralization (α) for each type of counterion. The effect of DS on the polymer charge fraction, i/s, is in line with the counterion condensation phenomena of Oosawa. The results regarding the dependence of the equivalent conductance of the polyion, Δp, on DS are compared with literature data.
Enzyme‐synthetic polyampholyte systems
Authors: Dupommier Alain , Merle‐Aubry Liliane , Merle Yves , Sélégny Eric
Published: April 2003

Polyampholytes, prepared by copolymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate and methacrylic acid, increase the urease activity over a large pH range, when the acid content is between 24 and 68 mol‐%, while the activity of the enzyme is inhibited by polyampholytes having more than 84 mol‐% of methacrylic acid groups. The enzyme reaction induces conformational changes of the polyampholyte chain resulting from a pH increase due to the formation of ammonium carbonate. The contraction of the macromolecule was followed by viscometry and by the volume change of a cross‐linked analogous polyampholyte gel.
Struktur und eigenschaften der copolymere aus 1,3,5‐trioxan und 1‐chlor‐2,3‐epoxypropan, 1. Festkörpereigenschaften der copolymerkristalle
Authors: Michnev Bontcho , Mateva Rosa
Published: April 2003

Changes in melting temperature, melting enthalpy and volume of the elementary cell of 1,3,5‐trioxane/1‐chloro‐2,3‐epoxypropane copolymers were investigated as function of the concentration of the comonomeric units involved.
Struktur und eigenschaften der copolymere aus 1,3,5‐trioxan und 1‐chlor‐2,3‐epoxypropan, 2. Morphologie der copolymerkristalle
Authors: Michnev Bontcho , Mateva Rosa
Published: April 2003

The morphology of copolymers from 1,3,5‐trioxane and 1‐chloro‐2,3‐epoxypropane was studied as function of polymerization time and amount of 1‐chloro‐2,3‐epoxypropane. Considerable changes of the morphology were observed when trespassing certain mole fractions of 1‐chloro‐2,3‐epoxypropane monomeric units in the copolymer chain.
Two‐Phase(water/organic) free radical polymerization of water‐soluble vinyl monomers using lipophilic acylated β‐cyclodextrins as initiator carrier
Authors: Ryoshi Hiroto , Kunieda Norio , Kinoshita Masayoshi
Published: April 2003

The acylated β‐cyclodextrins, heptakis(2,3,6‐tri‐O‐acetyl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐obutyryl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐butyryl)‐β‐cyclodextrin, and heptakis(2,3,6‐tri‐O‐pivaloyl)‐β‐cyclodextrin, cause a marked increase in the rate of polymerization of water‐ soluble vinyl monomers using water insoluble initiators in the two‐phase system consisting of water and an organic solvent (chloroform/ligroin, volume ratio 1 : 4). A plausible mechanism for this polymerization is proposed: The lipophilic acylated cyclodextrin acts as an initiator carrrier from the organic to the aqueous phase where polymerization takes place.
Study on the modification of soluble poly(epichlorohydrin) with 2‐mercaptoethanol and thioglycolic acid
Authors: Lamot Ryszard
Published: April 2003

From 1‐chloro‐2,3‐epoxypropane (epichlorohydrin), soluble poly(epichlorohydrin)s were prepared with molar masses in the range of 3,7 · 104 to 1,7 · 105 g/mol, using a complex of epichlorohydrin with hexaamminecalcium. These poly(epichlorohydrin)s were modified by reaction with 2‐mercaptoethanol or thioglycolic acid. The yields of these reactions range between 40 and 60%. The drop of molecular weight due to modification oscillate between 3,8 and 48,1%. The structure of the modified polymers was confirmed by elemental analyses, thermogravimetric and mass spectroscopic investigations. These chemical modifications carried out with poly(epichlorohydrin)s lead to water‐soluble products.
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

The 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

An 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

The 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

Polymerization 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

The 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

The 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

The 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

Benzoylation 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

The 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

Dilute 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

Inhibition 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

Three 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

The 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

Poly(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

The 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

Anionic 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

A 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

Chloramphenicol (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

Phospholipids 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

Tributyl 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

The 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

The 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

In 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

The 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.
Composite model calculation of the mechanical properties of polypropylene
Authors: Biswas Prabir K. , Sengupta Shyamal , Basu Asok N.
Published: April 2003

The theoretical interpretation of the anisotropic elastic properties of polypropylene is given. It was found that none of the existing models provide a unified description of the mechanical and optical properties of ultradrawn polypropylene. The composite model proposed by the authors, which takes into account the change in orientation and crystallinity on drawing, was applied to investigate the elastic moduli data of polypropylene for a wide range of temperature (−40 to 110°C) and over the entire drawing ratio range. The relationship between θ and θ′, the angles made by the C‐axis of the composite unit with drawing direction, was found to be adequately described by the relation tan θ = ϕ(n) tan θ′. It was further observed that ϕ(n) in the above relation obtained from birefringence data predicts the correct orientational changes on drawing for the temperature range −40 to 24°C. This makes the evaluation of mechanical properties possible without introducing any arbitrary parameter. However, it is noticed that a particular analytical form of ϕ(n) with two parameters is quite successful in interpreting the mechanical properties data over the entire temperature range. The abrupt changes of the parameters at certain temperatures seem to be correlated with the β‐relaxation and glass transition temperature.
On the physics of collapse of isolated polymer chains
Authors: Dayantis Jean
Published: April 2003

It is shown that Di Marzio's probability distribution does not provide a complete solution to the chain collapse problem insofar as compact globules are considered.
Reusable heterogeneous catalysts of α‐amino acid racemization, 2. Factors affecting the activity of heterogeneous catalysts based on strongly basic anion exchangers in OH− form and 4‐hydroxy‐3‐formylbenzenesulfonic acid (5‐sulfosalicylaldehyde)
Authors: Belokon' Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Belikov Vasili M.
Published: April 2003

The kinetics of (S)‐Ala racemization on heterogeneous catalysts based on eight strongly basic anion exchangers modified with 4‐hydroxy‐3‐formylbenzenesulfonic acid (5‐sulfosalicylaldehyde) (SSA) in the presence of Cu(II) ions at 25 °C was studied. The “internal capacity” value f = mp/(V0 — Vp) was introduced to characterize the polymers, (mp : number of quaternary ammonium groups of the polymer sample, V0 : total volume of the swollen polymer, Vp : volume of the inert polymeric matrix). The correlation of the observed first‐order rate constants of (S)‐Ala racemization with the f values of the anion exchangers was established. According to this correlation the selected anion exchangers could be divided into two types with respect to the chemical nature of the groups attached to the quaternary nitrogen atom. The chemical nature, physical structure and the degree of cross‐linking of the polymeric matrix do not affect the correlation. Anion exchangers of the first type have at least one ß‐hydroxyalkyl substituent at the

Anion exchangers of the second type have

(CH3)3 cationic groups. Catalysts prepared with the first type anion exchangers have greater activity as compared with catalysts based on the second type anion exchangers with the same f values. The increase in activity of heterogeneous catalysts can be partially attributed to the 10 to 68 fold increase in OH− concentration in the internal phase of the catalysts as compared to the model homogeneous system, which contains the same amounts of the components as the heterogeneous one. Moreover, an additional acceleration is observed in the heterogeneous racemization as compared to the homogeneous one, ca. 5 fold for the second type anion exchangers and ca. 14 fold for the first type anion exchangers.
New polymeric phosphonato‐, phosphinato‐ and carboxybetaïnes, 1. Syntheses and characterization by IR spectroscopy
Authors: Hamaide Thierry , Germanaud Laurent , Perchec Pierre Le
Published: April 2003

Neutral phosphonato‐, phosphinato‐, and carboxybetaïne moieties linked to various polymer supports, poly(styrene‐co‐4‐vinylpyridine) and poly(styrene‐co‐4‐dimethylaminomethylstyrene), were synthesized by a two step sequence. These products were characterized by means of FTIR analysis. Complexing properties towards transition metal salts are outlined.
Poly(ethylene glycol)s containing enzymatically degradable bonds
Authors: Ulbrich Karel , Strohalm Jiří , Kopeček Jindřich
Published: April 2003

The possibility to use poly(ethylene glycol) (PEG) as a synthetic, water‐soluble polymeric carrier of biologically active compounds was investigated. The relationship between structure of oligopeptide (amino acid)‐PEG conjugates and their hydrolysis catalyzed by chymotrypsin was studied. Two types of derivatives were synthesized: Derivatives of PEG 2000, containing an oligopeptide sequence terminating in p‐nitroaniline (drug model) and higher molecular weight derivatives of PEG 2000 containing in the main chain enzymatically and hydrolytically degradable bonds. The rates of chymotrypsin catalyzed release of p‐nitroaniline at pH 8,0 and 25°C were determined over a range of substrate concentrations to derive values for kcat and KM. The influence of the length and detailed structure of the oligopeptide sequence on the rate of hydrolysis was demonstrated. Comparison with copolymers of N‐(2‐hydroxypropyl)methacrylamide and poly(maleic anhydride‐co‐vinylpyrrolidone) showed that the sterical hindrance of the formation of the enzyme‐substrate complex is much less pronounced in the PEG‐oligopeptide conjugates. The latter conclusion is also valid in the case of cleavage of PEG derivatives which contain enzymatically degradable bonds in the main chain. The incorporation of a single amino acid residue (phenylalanine) into the main PEG chain is sufficient to make the polymer susceptible to chymotrypsin catalyzed hydrolysis.
Thermal properties of poly(2‐carboxyethylmethylsiloxane)‐poly(dimethylsiloxane) complexes
Authors: Ohyanagi Manshi , Kanai Hiroyuki , Takashima Tetsuo , Ikeda Koji , Sekine Yoshiro
Published: April 2003

The thermal properties of complexes between poly(2‐carboxyethylmethylsiloxane) and poly‐(dimethylsiloxane) are investigated. The results of DSC measurements indicate that the first‐order transition of the complexes is affected by the amount of poly(dimethylsiloxane) in the complex. From dynamic viscoelasticity measurements, it is inferred that the complex exhibits entropy elasticity due to a network structure maintained by hydrogen bonds.
Diffusion of TiO2 probe particles through a poly(ethylene oxide) melt
Authors: Lin Thy‐Hou
Published: April 2003

Quasi‐elastic light scattering (QELS) spectroscopy was for the first time used to measure the mutual diffusion coefficient Dm of titanium dioxide (TiO2) particles of 0,37 μm and 0,31 μm diameters in a poly(ethylene oxide) melt (weight‐average mol. wt. 7 500) between 85 °C and 160 °C. Dm exhibits a strong dependence on the temperature. The effective shear imposed by diffusing particles on the polymer melt was estimated through a comparison of the viscosity obtained by a cone‐and‐plate viscometer with the microviscosity calculated from the diffusion coefficients and hydrodynamic radii of the particles through the Stokes‐Einstein equation. The rate of shear found was ≥ 104 · s−1.
Kinetics of the thermal degradation of anhydrous bisphenol‐A polycarbonate/alkali metal arylcarboxylate systems in the melt
Authors: Bailly Christian , Daumerie Michel , Legras Roger , Mercier Jean P.
Published: April 2003

A kinetic study of the thermal degradation in the melt of bisphenol‐A polycarbonate in the presence of various anhydrous alkali metal arylcarboxylates is undertaken in order to assess the validity of the reaction mechanism previously established on a model system. The influence of the temperature, the concentration and the nature of the salt is studied. The results confirm the validity of the proposed kinetic model and suggest minor modifications to the reaction mechanism.
Study of the distributions of chemical composition and molecular weight in relation to the preparation method of vinyl alcohol/vinyl acetate copolymers
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Riofrio Alicia
Published: April 2003

The chemical heterogeneity of two vinyl alcohol/vinyl acetate (VAL‐VAC) copolymers prepared by partial acetylation of poly(vinyl alcohol) and by partial alkaline hydrolysis of poly(vinyl acetate), respectively, was studied by cross‐fractionation. The used solvent/non‐solvent systems were selected on the basis of cloud‐point determinations. The chemical composition distribution (CCD) and the molecular weight distribution (MWD) curves were constructed from fractionation data. The observed chemical heterogeneity was correlated with the kinetic parameters of the two different methods used for the preparation of the VAL‐VAC copolymers. Thus, squared standard deviation values

= 2,90·10−4 and

= 7,42·10−4 were found for the two VAL‐VAC copolymers prepared by acetylation and hydrolysis, respectively. These results are in agreement with theoretical predictions. The cumulative data were fitted by the two‐parameters MWD functions of Tung and of Wesslau.
The effect of branching on the Huggins coefficient of statistical styrene/butadiene copolymers
Authors: Reddy Gandavarapu Venkataramana , Petrus Vladimír , Bohdanecký Miloslav
Published: April 2003

The Huggins coefficient kH of solutions of statistical styrene/butadiene copolymers in cyclohexane (at 25 °C) and 2‐pentanone (theta temperature 21 °C) is discussed. With an increase in branching the values of

(i. e. kH at the theta temperature) increase from 0,5 to 0,73. Lower values in cyclohexane (good solvent) correlate with the viscosity expansion factor αη3, and the dependence is well fitted by the equation

where

is a function of the degree of branching, whereas C″0 only slightly exceeds the value found for linear polymers.
On the nature of the active centres in the anionic polymerization of methacrylonitrile, 3. Interaction with lithium tert‐butoxide
Authors: Adler Hans‐Jürgen , Lochmann Lubomir , Dotcheva Dobrinka T. , Tsvetanov Christo B.
Published: April 2003

The interaction between lithium tert‐butoxide (t‐BuOLi) and the active centres in the anionic oligomerization of acrylonitrile was studied by IR spectroscopy and conductometrically. α‐Lithiated isobutyronitrile and 1,3,3‐trimethylglutaronitrile were used as model compounds. t‐BuOLi forms complexes with these active centres in a 1:1 and/or 2:1 stoichiometry.
Elastic and photoelastic properties of polyisoprene networks — applicability and bounds of theories
Authors: Gleim Wolfgang , Oppermann Wilhelm , Rehage Günther
Published: April 2003

Measurements of stress and birefringence of networks of natural rubber and cis‐1,4‐polyisoprene deformed by simple elongation are reported. The experimental results are compared with theoretical calculations. It is found that the stress‐strain relation is in accordance with the empirical Mooney‐Rivlin equation. The constants 2 C1 and 2 C2 increase linearly with temperature indicating that both reflect essentially entropic elasticity. From theories dealing with the origin of the Mooney‐Rivlin behaviour, neither the entanglement concept nor the fluctuation or packing concept alone may account for the elastic behaviour observed. The photoelastic investigations prove the well‐known proportionality of stress and birefringence.
The morphology and structure of undoped and I2‐doped polyacetylene‐polybutadiene graft copolymer films
Authors: Bolognesi Alberto , Catellani Marinella , Destri Silvia , Porzio William , Meille Stefano Valdo , Pedemonte Enrico
Published: April 2003

The morphological and structural aspects of a novel polyacetylene‐polybutadiene (PA‐PB) graft copolymer film were investigated by means of transmission electron microscopy (TEM), electron diffraction (ED), and wide angle X‐ray diffraction (WAXS). Moreover, the evolution of these properties upon I2‐vapour doping of the cast films was followed. Finally, correlations between morphology, structure, and conductivity were drawn, suggesting a possible mechanism of conduction in this material.
A new experimental device for sensitive birefringence measurements
Authors: Bühler Fritz , Stadler Reimund , Gronski Wolfram
Published: April 2003

A double beam detection method for the measurement of birefringence in stretching experiments of polymers is developed. By this method a noise free intensity signal is measured allowing a sensitive determination of the absolute birefringence. The efficiency of the experimental device is tested using cis‐1,4‐polybutadiene and butyl‐rubber networks.
Orientation behaviour of rod‐like cross‐link molecules in elastomeric networks
Authors: Stadler Reimund , Bühler Fritz , Gronski Wolfram
Published: April 2003

cis‐1,4‐Polybutadiene and butyl‐rubber were cross‐linked in solution by a tetrafunctional enophilic cross‐linking agent, 4,4′‐methylenebis(1,4‐phenylene)di‐1,2,4‐triazoline‐3,5‐dione, possessing a rod‐like structure. The stress optical coefficients of the networks vary linearly with cross‐link concentration. The smaller concentration dependence for polybutadiene shows that a high fraction of cross‐link molecules are incorporated into the network chains as elastically ineffective cross‐links by formation of loops during the cross‐linking reaction. By combination of the stress optical data of both kinds of networks, the orientation function of elastically effective cross‐linkages is shown to be greater by a factor of about 8 than the orientation parameter of elastically ineffective cross‐link molecules in chains. From the effectivity of the cross‐linking reaction and the Mooney Rivlin constants 2C1 the memory factors of the networks were determined. They show that the compression of the networks in the dry state is considerably smaller than calculated by the polymer concentration during cross‐linking.
Electrical properties of linear poly(ester‐urethane)s, 1. D.C. conductivity
Authors: Rehage Günter , Lamour Richard , Fuhrmann Jürgen , Wilhelm Thomas
Published: April 2003

The steady‐state D.C. currents of linear poly(ester‐urethane)s with different hard to soft segment ratios were investigated. With increasing hard to soft segment ratios, the conductivity was found to increase and the field strength, where ohmic currents change to space charge limited currents, is significantly lowered. Five distinct regions of different thermal activation energy were observed as a function of temperature. With increasing temperature, the thermal activation energy is decreased. Stretched poly(ester‐urethane)s show lower conductivity due to segregation of hard and soft segments. The results are discussed in terms of polymer structure and are correlated with well‐known morphological phenomena in polyurethanes.
Phase separation in mixed liposomes of dipalmitoyl phosphatidylcholine and di‐2,4‐octadecadiene phosphatidylcholine
Authors: Tsuchida Eishun , Seki Noriko , Ohno Hiroyuki
Published: April 2003

Mixed liposomes were prepared from a mixture of lipids having saturated acyl chains (1,2‐dipalmitoyl‐3‐phosphatidylcholine; DPPC) and unsaturated ones (1,2‐bis(2,4‐octadecadienoyl)‐3‐phosphatidylcholine; DODPC) in order to analyze their phase separation behaviours. The phase transition behaviour was analyzed by fluorescence depolarization and differential scanning calorimetry. Transition temperatures of DPPC and DODPC are 42 and 18°C, respectively. In mixed liposome systems, two transition temperatures were clearly observed by both techniques. These results strongly suggest that these two different kinds of lipids do not dissolve homogeneously but form clusters (phase separation). DODPC molecules are polymerized by UV‐irradiation. Polymerization was confirmed by the decrease of the characteristic absorption band for diene groups. Phase separation was also observed in the polymerized mixed membrane and was directly confirmed by freeze‐fracture transmission electron microscopy.
Dissociation constant of poly(ethylene oxide) macroion pairs in nitrobenzene
Authors: Martinez Armando , Mijangos Fernando , León Luis Manuel
Published: April 2003

The great stability of the cationic polymerization system, ethylene oxide/nitrobenzene, from an electrochemical point of view, was investigatd as well as the assumption that the stable salts of triphenylmethylium and the macroion pair have the same dissociation constant. The value was determined to be 9,4 · 10−3 mol · 1−1 at 293 K in nitrobenzene.