bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permeability of solutes through hydrated polymer membranes. Part II. Permeability of water soluble organic solutes
Authors: Yasuda H. , Ikenberry L. D. , Lamaze C. E. 
Published: April 2003

AbstractThe diffusive permeabilities, P, of sodium chloride, urea, creatinine, secobarbital and bis‐hydroxyethyl terephthalate through water swollen polymer membranes were studied. The linear dependence of log P on the reciprocal of the volume fraction of water in the water swollen membrane, 1/H, (reported in Part I) was also found for those solutes investigated. The negative slope of the plot was found to increase with increasing size of solute. Ionic charge of the membrane phase was found to decrease the permeability of ionized solutes from values for neutral membranes and changes the permeability ratios of solutes. The permeability of highly ionized solutes, such as sodium chloride, are reduced by either positive or negative charge on the membrane phase; however, the permeability of weakly ionized organic solutes is affected mainly by membrane charge identical to the organic ions, and the effect of counter ions was found to be small.
Circular dichroism of soybean trypsin inhibitor and its derivatives
Authors: Jirgensons Bruno , Kawabata Makoto , Capetillo Sylvia 
Published: April 2003

AbstractCircular dichroism (CD) of soybean trypsin inhibitor (STI, the „KUNITZ inhibitor”︁)and some of its derivatives was studied in the spectral region of 185 to 320 mμ. Acetylation and succinylation, as well as denaturation with 6 M guanidine hydrochloride resulted in small changes in the CD spectra. In strongly acid solutions at pH 1.8 to 2.0 was observed a decrease of the amplitude of the positive COTTON effect at 226 mμ and a shift of this band to 230 mμ. Remarkable changes were observed in the CD spectra after cleavage of the disulfide bonds of STI either by reduction or sulfitolysis. The positive band at 226 mμ thereby disappeared, the negative bands around 240–300 mμ were modified and the amplitude of the strong negative COTTON effect at 200 mμ was diminished by the cleavage of the disulfide bonds. Reconstitution of the disulfide bonds lead to CD patterns resembling those of the native protein. The antitryptic activity of all chemically modified samples was significantly lowered.
Polymères thermostables. VIII. Les poly‐N‐aroylanthranilamides et leurs produits de condensation
Authors: Rabilloud Par Guy , Sillion Bernard , Gaudemaris Gabriel De 
Published: April 2003

AbstractOn a étudié la condensation des bis‐o‐aminoamides aromatiques sur des dihalogénures d'acide qui conduit à des poly‐N‐aroylanthranilamides de poids moléculaire élevé. Lorsque ces polymères sont soumis à un traitement thermique entre 250 et 400°C, on observe deux réactions avec élimination d'eau et d'ammoniac. Le dégagement d'eau correspond à la cyclisation attendue en quinazolone‐4, le dégagement d'ammoniac peut s'expliquer par la formation de liaisons imides intermoléculaires. L'examen de ces réactions thermiques sur des composés modèles confirme cette hypothèse. La stabilité thermique de ces polymères complexes est assez bonne: on observe un début de décomposition à 400°C en atmosphère d'argon et à 350–380°C à l'air.
Strahlenchemische Copolymerisation des Styrols mit Vinylchlorid. II. Pyrolyse der Styrol‐Vinylchlorid‐Copolymeren im Feldionen‐Massenspektrometer
Authors: Ryska Von M. , Schüddemage H.‐D. R. , Hummel D. O. 
Published: April 2003

AbstractPolystyrol, Polyvinylchlorid, Mischungen dieser Polymeren und Styrol/Vinylchlorid‐Copolymere, die unter verschiedenen Bedingungen (s. Teil I) hergestellt worden waren, wurden im Feldionenmassenspektrometer pyrolysiert. Während die Pyrolyse der Polymermischungen praktisch die gleichen Belegungen von Massenzahlen ergibt wie die Feldionenmassenpyrogramme der Homopolymeren, treten in den Copolymeren zusätzlich in großer Menge Fragmente mit Massenzahlen zwischen 100 und 250 auf. Nach der Intensität des Phenylbutadiens (MZ = 130), das sich aus benachbarten Monomereinheiten des Styrols und des Vinylchlorids bildet, wurde der Blockcharakter der einzelnen Polymerproben beurteilt. Die Ergebnisse wurden mit den kinetischen und den IR‐Untersuchungen verglichen. Durch langsame Pyrolyse bei niedrigen Temperaturen (350–400°C) wurde gezeigt, daß der thermische Abbau innerhalb der Vinylchloridsequenzen der Polymerkette beginnt.
A new model for the fold surfaces of polyethylene single crystals
Authors: Blackadder David A. , Roberts Trevor L. 
Published: April 2003

AbstractThe long‐standing debate concerning the perfection of single crystals of polyethylene has centred on the problem of formulating an acceptable model for the fold‐containing surfaces of the crystals. The literature offers very strong experimental evidence for the presence of a distinctive surface layer of significant volume characterized by the resemblance between some of its properties and those expected for amorphous polymer, notably the density as estimated by extrapolation from molten polymer. This surface layer has indeed come to be called amorphous, and its presence is apparently incompatible with other equally convincing evidence for high regularity at the surface. The new model proposed here is based on the supposition that it is neither necessary nor correct to endow the density‐deficient surface layer with all the properties of truly amorphous material; on the contrary, the surface layer must certainly have a low density but it may also possess considerable structural regularity including re‐entrant folds. The new model appears to be compatible with all the evidence including the experimental results presented in the paper. These concern the effect of crystallization temperature and solvent on density.
Anionic polymerization of ε‐caprolactam with lithium aluminum hydride and with N‐acetyl‐caprolactam and phenyl isocyanate activators
Authors: Solomon O. , Oprescu Cr. 
Published: April 2003

AbstractThe anionic polymerization of ε‐caprolactam in the presence of lithium aluminum hydride proceeds similarly as other processes initiated by various organometallic and hydride catalysts.When using N‐acetylcaprolactam or phenyl isocyanate as activators, the course of polymerization changes completely. Thus the polymerization can be carried out at low temperatures near the melting point of caprolactam, and the molecular weights, formed during polymerization, are stabilized.
Einfluß der thermischen vorgeschichte auf die eigenschaften von polyvinylchlorid
Authors: Illers Von K.‐H. 
Published: April 2003

AbstractDer Einfluß einer Temperung auf den Zustand von technischem Polyvinylchlorid wird zunächst durch kalorimetrische Messungen untersucht. Eine Temperung unterhalb der Glastemperatur führt infolge von Enthalpie‐Relaxation zu Zustandsänderungen, die nicht eine Erhöhung der Ordnung der amorphen Bereiche im Sinne zunehmender Kristallinität bedeuten, sondern durch eine Verringerung der Leerstellen‐Konzentration bedingt sind. Die Enthalpie‐Relaxation äußert sich bei kalorimetrischen Untersuchungen darin, daß je nach dem Verhältnis von Aufheiz‐ und Abkühlgeschwindigkeit der cp‐Stufe bei der Glastemperatur ein endothermes Maximum („Überhitzungs‐Maximum”︁) unmittelbar überlagert ist oder daß bei scharf abgeschreckten Proben am unteren Ende des Glasübergangs‐Bereiches der Stufe ein Maximum oder Minimum vorgelagert ist. Die Überhitzungsenthalpie, die ein quantitatives Maß für die bei der Temperung abgelaufenen Zustandsänderungen ist, ist stark von der angewandten Aufheizgeschwindigkeit abhängig. Der Glas‐Übergang beginnt bei um so tieferen Temperaturen, je schärfer Polyvinylchlorid von oberhalb der Glastemperatur abgeschreckt wird. Den gleichen Befund erhält man aus dynamisch‐mechanischen Untersuchungen.Das untersuchte Polyvinylchlorid ist partiell kristallin. Die beim langsamen Abkühlen aus der Schmelze gebildeten Kristalle schmelzen beim Aufheizen im Temperaturbereich zwischen 115 und 205°C. Die Schmelzwärme beträgt ca. 2 cal/g. Durch scharfes Abschrecken läßt sich die Kristallinität verringern. Beim nachfolgenden Aufheizen findet in diesem Fall eine Nachkristallisation statt. Eine nachträgliche Temperung oberhalb der Glastemperatur führt auch bei langsam aus der Schmelze kristallisiertem Polyvinylchlorid zu einer Nachkristallisation. Die bei dieser Nachkristallisation gebildeten Kristalle ergeben beim Aufheizen ein endothermes Schmelzmaximum, dessen Fläche (Schmelzwärme) von der Heizgeschwindigkeit unabhängig ist und das immer oberhalb der Glastemperatur‐Stufe, und zwar ca. 25°C oberhalb der jeweiligen Tempertemperatur (Temperzeit 1–2 Stdn.), liegt. Es steht in keinem ursächlichen Zusammenhang mit dem durch Temperung unterhalb der Glastemperatur hervorgerufenen Überhitzungs‐Maximum.Die Diffusion von Flüssigkeiten und die Permeation von Gasen hängen stark von der thermischen Vorgeschichte ab. Durch Temperung sowohl oberhalb als auch unterhalb der Glastemperatur steigt die im Zugversuch ermittelte Streck‐Spannung an, und die Bruchdehnung fällt stark ab. Die oberhalb und unterhalb der Glastemperatur erzielten Veränderungen beruhen jedoch auf zwei verschiedenen Ursachen.
Kinetic studies on the polymerization of 1.3.6‐trioxocane catalyzed by triethyl oxonium tetrafluoroborate
Authors: Okada Masahiko , Kozawa Shigeyuki , Yamashita Yuya 
Published: April 2003

AbstractThe kinetics of the polymerization of 1.3.6‐trioxocane was studied in 1.2‐dichloroethane by using triethyl oxonium tetrafluoroborate as a catalyst. The number average molecular weight of the polymer remains almost constant throughout the polymerization, indicating that the rate of initiation is considerably slower than that of propagation and that the polymerization is accompanied by some chain breaking reactions. On the basis of product analysis of the equimolar reaction of the monomer and the catalyst, a mechanism of chain scission reactions is proposed.
Vinyl polymerization. 235. Free radicals in the polymerization of vinyl monomers initiated by GOMBERG's and its relatad reactions
Authors: Kinoshita Masayoshi , Yoshizumi Nobuo , Imoto Minoru 
Published: April 2003

AbstractFree radicals derived from the GOMBERG's reaction of arylmethyl halides such as benzyldiphenylmethyl‐, and tritylbromide and chloride, with silver powder or mercury can initiate the radical polymerization and copolymerization of styrene, methyl methacrylate, acrylonitrile, vinyl chloride, and vinyl acetate. The orders of initiating abilities of halides in the polymerization of styrene and methyl methacrylate were as follows; for bromides, benzyl‐ > diphenylmethyl‐ > trityl‐, and for chlorides, diphenylmethyl‐ > benzyl‐ > trityl‐, when silver was used as metal component, while the order for the both halides is diphenylmethyl‐ > benzyl‐ > trityl‐ with mercury. These results were understood by the competition of the reactivities of halides to metal with those of the derived radicals to monomer. The over‐all polymerization rate of the system styrene/silver/benzyl bromide was proportional to monomer concentration, square root of halide concentration, and square root of the amount of added but insoluble silver powder.The radical‐like composition curves of styrene‐methyl methacrylate copolymers and the inhibition of polymerization by verdazyl, a stable free radical, show that these polymerization systems include radical propagation step. Hexaphenylethane and 1.1.2.2‐tetraphenylethane were isolated from the reaction systems, trityl halide/silver and diphenylmethyl chloride/silver or mercury, respectively. Recombination products of verdazyl with diphenylmethyl radical and benzyl radical were also isolated, but not N‐trityl‐verdazyl. Tracer study with benzyl bromide‐7−14C showed the incorporation of benzyl fragments in the obtained polymer.
Cationic polymerisation of exo‐2‐methyl‐7‐oxabicyclo‐[2.2.1]‐heptane: The catalytic system fecl3—socl2
Authors: Giusti P. , Fiorentino U. , Turchi G. , Andruzzi F. , Magagnini P. L. 
Published: April 2003

AbstractThe nature of the acceleration period which is found in the polymerisation of exo‐2‐methyl‐7‐oxabicyclo‐[2.2.1]‐heptane with FeCl3—SOCl2, when R = [FeCl3]/[SOCl2] is above a certain limit, has been investigated. By means of a conductometric study of the reactions occurring in C2H4Cl2/diethylether mixture (6:1 by volume), between FeCl3 and SOCl2, it has been possible to show that this acceleration period is related to a slow formation of ionic species, from which the chain carriers are formed.When the catalyst/cocatalyst mixture was allowed to stand until equilibrium was attained before it was added to the monomer solution, no acceleration period was detectable.The kinetic study of the polymerisation was then extended to the whole range of catalyst/cocatalyst ratios. It has been shown that the ion SO2⊕ which is present when [FeCl3] is higher than [SOCl2] is not able to initiate the polymerisation. If R is ⪖ 5 there is no polymerisation, whatever the [FeCl3]. If R is less than 5 but more than about 2, the polymerisation practically stops at partial conversion. When R is well below 1 the time‐conversion curves give good second order plots indicating a stationary state condition.
Studies on organometallic compounds as polymerization catalysts. V. Mechanism of propylene oxide polymerization initiated by zinc dialkoxide
Authors: Ishimori Michihiro , Hsiue Ginho , Tsuruta Teiji 
Published: April 2003

AbstractA method of preparation of a lattice‐disordered (or amorphous) zinc dimethoxide was explored, involving the reaction of diethylzinc with methanol under reflux in methanol solution. The amorphous zinc dimethoxide thus obtained, showed extremely high activity for propylene oxide polymerization. This polymerization is of living type and follows a first order rate law for the disappearance of monomer. The activity of the amorphous zinc dialkoxide decreases in the presence of ethylzinc alkoxide or alcohol. On change of solvent, the polymerization rate is found to depend on coordination strength of solvent, rather than on its dielectric constant. Polymerization of propylene oxide catalyzed by the diethylzinc/alcohol system is discussed in terms of a coordinate anionic mechanism.
Amphotere ionenaustauscher (teil IV)
Authors: Manecke Von Georg , Stockhausen Klaus , Gergs Peter 
Published: April 2003

AbstractDurch Kondensation von Polyäthylenimin mit Formaldehyd und phosphoriger Säure wurde ein polymerer Komplexbildner synthetisiert, der Methylphosphonsäuregruppen am Polyäthylenimingrundgerüst enthält. Durch Umsetzung von vernetztem Polyäthylenimin mit Formaldehyd und phosphoriger Säure wurde ein neuer amphoterer Ionenaustauscher von hoher mechanischer und chemischer Stabilität erhalten. Sowoh! mit vernetztem als auch mit unvernetztem Polyäthylenimin konnte bei dieser Kondensationsreaktion ein Umsetzungsgrad von 50% (bezogen auf eingesetztes Polyäthylenimin) nicht überschritten werden.Das Ionenbindungsvermögen für Cu2⊕, Zn2⊕ Ni2⊕ und Mg2⊕ des amphoteren Ionenaustauschers wurde untersucht. Kupferbindungsvermögen bei pH 6 : 6,0 m Val/g. Die Untersuchung der Quellbarkeit des Austauschers in Abhängigkeit vom pH‐Wert ergab eine sehr geringe pH‐Abhängigkeit der Quellung.Die Vernetzung des Polyäthylenimins wurde erstmalig mit 1.4‐Bis‐(chlormethyl)‐benzol durchgeführt. Das so vernetzte Polyäthylenimin stellt einen schwach basischen Ionenaustauscher mit sehr guten mechanischen und chemischen Eigenschaften dar. Die pH‐Abhängigkeit der Quellung und das Kupferbindungsvermögen wurden bestimmt.
Salt‐catalyzed reaction of phenyl glycidyl ether with silk fibroin
Authors: Tanaka Yoshio , Shiozaki Hideki 
Published: April 2003

AbstractThe addition reaction of phenyl glycidyl ether (PGE) with silk fibroin was investigated in the presence of various salts in different solvents at 40–130°C. Some water was required to make the epoxide react with silk padded with various salt solutions. The reaction rate increased with the salt and PGE concentrations and reached a maximum value at a certain concentration of the salt or PGE. Padding with solutions of thiosulfate, stannate, thiocyanate, bicarbonate, and cyanide resulted in large weight gains to 12%, dry crease angles of 138°, little moisture regains and low solubilities (up to 15%) in 3 N HCl and 1 N NaOH aqueous solutions at 65°C (1 hr). Histidine, lysine, arginine, aspartic and glutamic acids, serine, and tyrosine reacted. The weight gains decreased with increasing solubility parameter of the solvents used, reached a minimum value at about 10 or at the solubility parameter of the epoxide, and then increased with the parameter. The epoxide‐silk reaction may depend on the distribution of PGE between aqueous salt and an organic solvent phases, and on the swelling of the silk fibroin in aqueous salt solution or in various organic solvents. The mechanism for this epoxide‐silk reaction was discussed in the light of the observed phenomena.
Dimensions non perturbées des chaînes macromoléculaires dans les solvants associés
Authors: Dondos Anastasios , Benoît Henri 
Published: April 2003

AbstractIn this paper a systematic study of unperturbed dimensions of poly(2‐vinyl pyridine) and polymethylmethacrylate in various polar and associated solvents is presented.Studying intrinsic viscosity as function of molecular weight and using the STOCKMAYER‐FIXMAN‐BURCHARD plot, one is able to evaluate KΘ, i.e. the unperturbed dimensions of these polymers in various solvents.As soon as the solvent is selfassociated the values of KΘ are lower than in regular solvents.An increase of temperature produces an increase in KΘ; by extrapolation to the boiling point of the solvent one obtains the classical value. Since selfassociation disappears usually at boiling temperature this result indicates that the lowering of KΘ is due to selfassociation of the solvent.This yields a very simple method for a determination of the amount of selfassociation in various solvents.These results are compared with previous results obtained in mixed solvents and a tentative qualitative explanation is presented.From the data obtained for various polymers in both solvent mixtures and selfassociated solvents it follows that the validity of the classical theories of polymer solutions is limited to the case of non polar polymers dissolved in non polar solvents.
Strukturbildung von trioxancopolymeren
Authors: Mihajlov Von M. , Terlemezjan L. 
Published: April 2003

AbstractDurch Polymerisation in Substanz wurden Copolymere aus Trioxan und Glycidyläthern ein‐ und zweiwertiger Alkohole oder Phenole, Butylvinyläther, 1.3‐Dioxolan und Styrol hergestellt.Die Bildung übermolekularer Strukturen bei der Kristallisation aus dünnen Schmelzfilmen wurde mikroskopisch untersucht. Es ergab sich, daß die Copolymeren mit nur aliphatischen comonomeren Bausteinen als typische Hedrite kristallisieren. Die durch Polymerisation von Trioxan in Gegenwart von gemischten aliphatisch‐aromatischen Monomeren erhaltenen Copolymeren neigen bei isothermer und besonders bei nichtisothermer Kristallisation zur Bildung intermediärer hedritisch‐sphärolithischer oder sphärolithischer Strukturen.
Homopolymerization of dicyclopentadiene induced by Ziegler‐Natta catalysts and by other transition metal systems
Authors: Dall'Asta G. , Motroni G. , Manetti R. , Tosi C. 
Published: April 2003

AbstractThe homopolymerization of dicyclopentadiene induced by catalysts, containing transition metals of the groups IV, V, VI, and VIII of the periodic table of elements, yields polymers having different monomeric units depending on the transition metal and on the acid base character of the catalytic system. Seven different monomeric units, some of which not observed up to now, could be assigned on the basis of infrared spectroscopic measurements. All monomeric units derive from the ring cleavage or from the addition to the double bonds of both unsaturated five‐membered rings, whereas the saturated five‐membered ring of the monomer is always retained in the polymer. In the presence of some particular catalysts the polymerization leads to products having uniform chemical structure.
Kinetics and mechanism of oxetanes polymerization catalyzed by AlR3. Part II. Non‐stationary polymerization and chain transfer to polymer
Authors: Penczek Stanislaw , Kubisa Przemyslaw 
Published: April 2003

AbstractPolymerization of 3.3‐bis(chloromethyl)oxetane induced by (iso‐C4H9)3Al/H2O catalytic system proceeds in chlorobenzene solution at 55–95°C in homogeneous conditions. Dilatometric study in a high vacuum system permitted to establish the following main features of the process under study : irrespectively of the [(iso‐C4H9)3Al]/[H2O] ratio or [catalyst]/[monomer] ratio a gradual acceleration at the start of reaction was observed, followed by a “linear” portion, which in turn is followed by a deceleration. The whole process can be described as the non‐stationary reaction with slow initiation, fast propagation and slow degradative chain transfer to polymer. Polymerization is externally first order on [monomer] (when the influence of initiation was excluded), first order on [H2O] until [H2O] ≤ [(iso‐C4H9)3Al]. The sigmoidal dependence with saturation of rate and degree of polymerization on [(iso‐C4H9)3Al] shows, that for [(iso‐C4H9)3Al] ≥ [H2O] the excess of (iso‐C4H9)3Al has no important influence on both polymerization kinetics as well as on the polymer P̄. The low ratio of P̄w/P̄n (lower than 1.1) indicates that the acceleration period is not due to the consumption of impurities.Approximated 10 molecules of H2O participate in the formation of one active center. This value was found by extrapolation of the plot of {Pn (theoretical)/Pn (experimental)} on [H2O] to [H2O] = 0. With increasing the ratio of [catalyst]/[monomer] the percentage of the unused catalyst also increases. Solution of the kinetic scheme as described above, with a degradative chain transfer to polymer treated as an irreversible process, led to the following absolute values of the apparent rate constants, being at 70°C equal to : ki = 1.6·10‐3 mole‐1·1·sec‐1, kp = 8.5 mole‐1·1·sec‐1, and ktr = 1.2·10‐3 mole‐1·l·sec‐1. The ktr was compared with the rate constants of the chain transfer to low molecular ethers (ktE). The ktr value is close to ktE found for β‐chloroethyl ether of a structure close to this of a polymer segment. The plot of ktE/kp on – pKa is linear with a slope expected for a cationic process.
Über polyenarylene und polyenheteroarylene. 1. Mitt.: Poly‐[thienylen‐(2.5)‐äthenamer] und einige seiner oligomeren. Synthesen, spektrales verhalten und elektrische leitfähigkeit
Authors: Kossmehl Von Gerhard , Härtel Manfred , Manecke Georg 
Published: April 2003

AbstractBei der WITTIG‐Reaktion von 2.5‐Bis‐(triphenylphosphoniomethyl)‐thiophen‐dichlorid mit Thiophen‐2.5‐dialdehyd wurde Poly‐[thienylen‐(2.5)‐äthenamer] mit endständigen Aldehydgruppen erhalten. Durch Reaktion mit 2‐(Triphenylphosphoniomethyl)‐thiophenchlorid läßt sich ein Teil der Aldehydgruppen in Thienyl‐(2)‐vinyl‐Gruppen überführen. Zum Vergleich wurden – ebenfalls mit Hilfe der WITTIG‐Reaktion – Oligomere der allgemeinen Formel R(CHCHR)nH [R = Thienyl‐(2)‐; R = Thienylen‐(2.5)‐] mit n = 1,2,3,4,6 hergestellt. Die Struktur der untersuchten Verbindungen wurde durch UV‐Spektren, sichtbare Spektren, IR‐Spektren und Massenspektren bestätigt. Zur weiteren Charakterisierung wurden Röntgenuntersuchungen herangezogen. Die Oligomeren sowie das Polymere wurden auf ihre elektrische Leitfähigkeit hin untersucht.