bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional polymers, 11. Synthesis and polymerization of 2‐(2‐hydroxy‐5‐vinylphenyl)‐2H‐benzotriazole
Authors: Yoshida Shohei , Vogl Otto 
Published: April 2003

Abstract2‐(2‐Hydroxy‐5‐vinylphenyl)‐2H‐benzotriazole (9) was prepared by a seven step synthesis in about a 25% overall yield starting fromo‐nitroaniline. Diazotization in aqueous HCl gave a diazonium salt which was coupled withp‐ethylphenol to an azo‐dye which was reduced with zinc powder in sodium hydroxide solution to 2‐(2‐hydroxy‐5‐ethylphenyl)‐2H‐benzotriazole (4). This compound was acetylated and then brominated withN‐bromosuccinimide to 2‐[2‐acetoxy‐5‐(1‐bromoethyl)phenyl]‐2H‐benzotriazole (6) which was dehydrobrominated with triethylamine in acetonitrile or tributylamine in dimethylacetamide to the vinyl compound which was hydrolyzed to9. This monomer was readily homopolymerized and copolymerized with styrene and methyl methacrylate using 2,2′‐azobis(2‐methylpropionitrile) as initiator.
Photoinitiators and photoinitiation, 3. Comparison of the photodecompositions of α‐methoxy‐ and α,α‐dimethoxydeoxybenzoin in 1,1‐diphenylethylene as model substrate
Authors: Groenenbook Cornelis J. , Hageman Hendrik J. , Overeem Ton , Weber Anton J. M. 
Published: April 2003

AbstractThe photodecomposition of α‐methoxydeoxybenzoin (1) and α,α‐dimethoxydeoxybenzoin (2) was investigated both in the absence and in the presence of 1,1‐diphenylethylene. The resulting products indicate that benzoyl radicals add to the olefinic double bond (initiation of polymerization), whereas the α‐methoxybenzyl radicals generated from 1 do not add to the olefinic double bond (no initiation), but preferentially combine with other radicals (termination of polymerization). This reaction is largely suppressed in the case of α,α‐dimethoxybenzyl radicals generated from 2 owing to sequential fragmentation into inactive methylbenzoate and highly reactive methyl radicals which add to the olefinic double bond and thus contribute to the initiation.
Interaction between polynucleotides in aqueous NaCl solution, 4. Poly(riboadenylic acid) — poly(2‐riboinosinic acid) system
Authors: Fujioka Kazuhiko , Baba Yoshihiro , Kagemoto Akihiro 
Published: April 2003

AbstractSolution properties of poly(A) and poly(I) solution at a mole ratio of poly(A) to poly(I) of 1/2 were studied by means of calorimetry and a modified differential scanning calorimetry (DSC) with the help of circular dichroism (CD) and ultraviolet (UV) spectral methods. It was found that the heat of mixing, ΔHM, depends sharply on the ionic strength. At [NaCl] < 10−2 mol · dm−3 ΔHM is nearly zero. At higher ionic strength ΔHM decreases and reaches a minimum value at [NaCl] ≈︁ 2 · 10−2 mol − dm−3. Above this ionic strength ΔHM increases again. This behavior is explained on the basis of the formation of a triplex poly(A) · poly(2I) and the transition of poly(I) from a disordered to an ordered structure with increasing ionic strength. The heat of formation, ΔH, of the poly(A) · poly(21) triplex was estimated to be ca −41 kJ per mole of base triplet. Above an NaCl concentration of 2 · 10−1 mol · dm−3 the triplex formation may be represented by the following scheme:
NMR studies of chitin and chitin derivatives
Authors: Gagnaire Didier , Saint‐Germain Jean , Vincendon Marc 
Published: April 2003

AbstractThe 13C NMR spectra of N‐acetyl‐D‐glucosamine (1) and chitobiose (2), monomer and dimer of chitin, were assigned and used to assign the 13C NMR spectra of chitin in lithium thiocyanate and in LiCl/dimethylacetamide solutions. The dissolution of chitin in formic acid was studied. IR, 13C and 1H NMR spectra show that dissolution occurs by a reaction of formic acid with chitin with the formation of formyl chitin as a statistical derivative of chitin. 13C NMR spectra of diformyl‐ and diacetylchitin were also assigned to characterize these regular polymers.
Carriers for drugs and enzymes based on copolymers of allyl glycidyl ether with acrylamide
Authors: Pitha Josef , Zawadzki Stefan , Hughes Barbara A. 
Published: April 2003

AbstractCopolymerization of acrylamide with allyl glycidyl ether yielded water soluble polymers containing an epoxy group; addition of a crosslinking agent, N,N′‐methylenebis(acrylamide), to the copolymerization mixtures resulted in the formation of similar though water insoluble polymers. Condensation of a potent beta‐adrenergic antagonist AlmH, which contains a reactive amino group, with a polymer containing an epoxy group yeilded a pharmacologically active polymer. The polymer containing the epoxy group was also converted, by reaction with sodium thiosulfate and subsequent reduction, into a mecapto groups containing polymer which was also water soluble. The latter polymer was converted by condensation with a beta‐adrenergic antagonist AlmCOCH2Br, which contains a reactive bromoacetamido group, into a pharmacologically active polymer.
Polymethacrylic acid derivatives, 3. Potentiometric and conductimetric titrations of poly‐[N‐methacryloyl‐L‐alanine‐co‐N‐phenylmethacrylamide] and poly[methacrylic acid‐co‐benzyl methacrylate]
Authors: Morcellet‐Sauvage Joëlle , Morcellet Michel , Loucheux Claude 
Published: April 2003

AbstractThe compact → coil conformational transition of two series of hydrophilic‐hydrophobic copolymers derived from poly(methacrylic acid) was studied by potentiometric and conductimetric titrations. The samples used were poly(N‐methacryloylalanine‐co‐N‐phenylmethacrylamide) containing up to 50 mole‐% of the hydrophobic residue (P series) and poly(methacrylic acid‐co‐benzyl methacrylate) containing up to 25 mole‐% of the hydrophobic residue (S series). The determination of the free enthalpy of the transition and of the domain of the degree of ionization in which the transition occurs, show inportant differences in the behaviour of the two series of copolymers. These differences are explained by an entropy‐enthalpy compensation for the S series due to strong hydrophobic interactions between the aromatic side chains. Conductimetric titrations allow, in some cases, the determination of the degree of ionization at the beginning and at the end of the conformational transition.
Stereocontrol in the free radical polymerization of N‐vinylcarbazole
Authors: Terrell David R. , Evers Fritjof 
Published: April 2003

AbstractThe free radical polymerization of N‐vinylcarbazole (VK) was investigated in hexane, nonane, toluene, HMPT, DMF, DMAC, and DMSO. Isotactic propagation was found to be energetically favoured by between 1500 and 4600 J · mol−1 for all the solvents investigated, although the entropy difference between syndiotactic and isotactic propagation strongly favoured syndiotactic propagation by between 11 and 20 J · mol−1K−1. Variation in the steric microstructure between an isotactic mole fraction of 0,25 and 0,47 was obtained by varying the polymerization temperature and solvent. The activation enthalpy differences between isotactic and syndiotactic propagation (ΔH≠s/i − ΔH≠i/s), for the free radical polymerization of methyl methacrylate (MMA) and VK were compared and the steric configurations involved in the propagation process considered. It was concluded that electronic interaction between radical and monomer appeared to determine the energetic preference of the growing chain for isotactic or syndiotactic propagation in free radical propagation. This energetic preference was correlated with the e‐factor in the Q − e scale. Data for the free radical polymerization of VK, MMA, and vinyl trifluoroacetate showed that solvent polarity has a weak influence on the energetic preference of the growing chain for isotactic or syndiotactic propagation. This energetic preference was correlated with the π* solvent polarity scale.
Studies on formaldehyde resins, 19. General base catalysis in hydroxymethylation of melamine with formaldehyde
Authors: Sato Kenji , Konakahara Takeo , Kawashima Mikio 
Published: April 2003

AbstractHydroxymethylation of melamine with formaldehyde to form N‐(hydroxymethyl)melamine (2,4‐diamino‐6‐hydroxymethylamino‐1,3,5‐triazine) was investigated kinetically by the use of hydrogen phosphate/phosphate buffers in aqueous media at pH 11 − 12. This reaction was found to follow a general base catalysis which results from the kinetic investigation, showing that the reaction takes place by a concerted mechanism involving base, melamine, and formaldehyde. This mechanism differs from that of the base catalyzed hydroxymethylation of phenol or benzamide with formaldehyde, because the acidic phenol and benzamide easily form their conjugate bases by addition of the basic catalyst in a preceding equilibrium step.
Heat capacity of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene)
Authors: Jauhiainen Tuure‐Pekka 
Published: April 2003

AbstractThe heat capacities of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) were measured from 160 to 480 K using a differential scanning calorimeter (DSC) interfaced to a computer for data collection and processing. The values for the heat capacities between 160 and 420 K were tabulated. Below 280 K they depend only slightly on the molar mass, whereas above 280 K the conformational changes of the end groups have a noticeable effect. Wunderlich's addition scheme for the calculation of heat capacities from the empirical group contributions gives results that agree within ± 1% with the experimental data. The heat capacity jump ΔCp at Tg depends inversely on the molar mass. Wunderlich's “bead” model for ΔCp values is discussed for poly(oxy‐2,6‐disubstituted‐1,4‐phenylene).
Thermal expansion of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene)
Authors: Jauhiainen Tuure‐Pekka 
Published: April 2003

AbstractThe thermal expansion coefficient of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene), PPOO, was measured from 150 to 500 K, using a thermomechanical analyzer connected to a computer for the data handling. Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), PPO, and some brominated poly(oxy‐2,6‐disubstituted‐1,4‐phenylene)s were studied as reference materials. The apparent glass transition temperatures of the high molar mass polymers were 456 K for PPOO and 487 K for PPO, and the changes in cubic thermal expansion coefficients at Tg were 6,01 · 10−4 K−1 for PPOO and 4,23 · 10−4 K−1 for PPO. The activation of the β‐relaxation was found for PPOO at 260 K and attributed to the hindered torsional oscillations of the backbone phenylene groups. Another transition was found at 160 − 170 K and interpreted as the γ‐relaxation due to the oscillatory motion of the methoxy groups. Reasons for the differences in the thermal expansion behaviour of PPOO and PPO are discussed.
Cyclopolymerization of N‐methacryloyl‐N‐methylcrotonamide
Authors: Yamada Bunichiro , Saya Toshiaki , Ohya Takahiro , Otsu Takayuki 
Published: April 2003

AbstractN‐Methacryloyl‐N‐methylcrotonamide (MMCA) was prepared by the reaction of methacryloyl chloride with N‐methylcrotonamide. While N,N‐disubstituted methacrylamide and crotonamide, which can be considered as structual moieties of MMCA, do not homopolymerize, nevertheless MMCA yielded a homopolymer consisting of 5‐membered cyclic repeating units. MMCA was found to be more reactive than N‐propyldimethacrylamide in copolymerization with styrene and methyl methacrylate. Since the polymer radical adds to the methacrylamide moiety, the steric hindrance of a β‐methyl group in the crotonamide moiety must be less significant than that of the α‐methyl group of the methacrylamide moiety in the dimethacrylamide. The 5‐membered ring formation during the polymerization of MMCA was facilitated by the favorable conformation of the three carbon atoms concerned in the ring closure to achieve coplanarity, which is required for the fast 5‐membered ring closure. The coplanarity of the three carbon atoms and reluctance to homopolymerize of the reacting double bonds seem to be the minimum requirements for forming of a polymer consisting of solely 5‐membered cyclic repeating units.
Dynamic mechanical properties of polyurethane networks containing sodium tetraphenylborate, 2. The modulus dependence on temperature, frequency, and salt concentration
Authors: Killis Andréas , Le Nest Jean‐François , Gandini Alessandro , Cheradame Hervé 
Published: April 2003

AbstractThe viscoelastic behaviour of polyether‐based polyurethane networks containing sodium tetraphenylborate was investigated by means of dynamic mechanical measurements. A quantitative analysis of the storage modulus dependence on temperature, frequency, and salt concentration gives rise to three superposition correlations, viz. frequency‐temperature, frequency‐concentration, and concentration‐temperature. The frequency‐temperature superposition follows a WLF behaviour, while the other two are approximately linear expressions particularly well verified in the zone of the transition state.
Crystallinity of methylene‐oxyethylene‐methylene triblock oligomers derived from nonaethylene glycol
Authors: Domszy Roman C. , Booth Colin 
Published: April 2003

AbstractBlock oligomers of general formula CH3(CH2)nO[CH2CH2O]9(CH2)nCH3 where n = 0 to 25 have been prepared. All blocks are monodisperse. Examination of their crystallinity (by differential scanning calorimetry, X‐ray scattering, infra‐red and Raman spectroscopy) shows that, within defined limits (n > 9, crystallisation temperature high), the block oligomers can crystallise completely. A likely structure is 7/2 helical monoclinic oxyethylene blocks and planar zigzag low density methylene blocks, with the oxyethylene helices normal to the lamella end‐planes and the methylene chains titled.
Copolymerization of methyl acrylate with isobutylene in the presence of lewis acids
Authors: Florjanczyk Zbigniew , Kuran Witold , Langwald Norbert , Sitkowska Jadwiga 
Published: April 2003

AbstractThe copolymerization of methyl acrylate (MA) and isobutylene (IB) in the presence of Lewis acids (EtAlCl2, Et2AlCl, Et3Al, AlCl3, and ZnCl2) at low Lewis acid/MA mole ratio was investigated. EtAlCl2 and Et2AlCl were found to initiate the spontaneous reaction. An alternating copolymer was produced in this reaction when an excess of IB in the initial monomer feed was used. The copolymerization in the presence of Et3Al, AlCl3, and ZnCl2 did not proceed spontaneously and was initiated by dibenzoyl peroxide (BPO). In this case MA‐rich copolymers are formed even in systems containing a large excess of IB in the monomer feed. The addition of BPO to systems containing ethylaluminium chlorides strongly diminishes the tendency towards alternating propagation. It was concluded that the mode of initiation has a significant influence on the copolymer composition. The alternating copolymerization by EtAlCl2 was studied in detail in order to determine the influence of the catalyst concentration, monomer feed ratio, reaction temperature and time on the monomer conversion, copolymer composition, molecular weight and tacticity.
Functional monomers and polymers, 89. Synthesis of poly(β‐alanine) in the functional reversed micelle
Authors: Hanabusa Kenji , Shirai Hirofusa , Hojo Nobumasa , Kondo Koichi , Takemoto Kiichi 
Published: April 2003

AbstractActive β‐alanine 4‐acyl‐2‐nitrophenyl esters (5a—j) containing ω‐phenyl‐ or ω‐cyclohexyl acyl groups were prepared and their polycondensation was studied, which can take place in the reversed micelle to give poly(β‐alanine). Non‐polar solvents were suitable for the polycondensation, while no polymer was formed in protic and dipolar aprotic solvents. Esters having long linear acyl groups (5n—o) were also reactive enough to give the polymer. However, the esters containing phenyl and cyclohexyl groups (5a—j) were much more reactive and gave the polymer in high yield even if the linear acyl chain was only short.
On the kinetics and mechanism of thermal degradation of polystyrene
Authors: Ebert Klaus H. , Ederer Hanns J. , Schröder Ulrich K. O. , Hamielec Archie W. 
Published: April 2003

AbstractThe thermal degradation of polydisperse polystyrene samples with mol. wts. (M̄n) between 60000 and 22000 has been investigated at different temperatures under oxygen free conditions. Product analysis has been carried out by GPC. The experimental degradation could be simulated by a model consisting of scission and depolymerization. The dynamical behaviour of this model is expressed in a matrix from. The ratio of scission and depolymerization is constant for all polymers and different temperatures during degradation. Therefore, a master curve could be evaluated, which gives a general relation between the decrease of mol. wt. and the mass of volatiles. Finally a radical chain mechanism has been proposed in a lumped form which is consistent with the kinetic model and the experimental results.
Stoichiometric salt‐linkage formation of trimethylammonium glycol chitosan iodide with a carboxylic type ion exchanger
Authors: Kokufuta Etsuo , Fujii Susumu , Nakamura Isei 
Published: April 2003

AbstractThe adsorption of trimethylammonium glycol chitosan iodide (TGCI) on Dowex CCR‐2 resin was investigated at different pH values and resin weights. The concentration of Na+ or Ca2+ ions, released by the ion exchange reaction with TGCI, was measured by inductively coupled plasma spectroscopy. It was found that the amount of the released ions is comparable to that of the absorbed TGCI. This indicates that the salt‐linkage formation of carboxylate ions of the exchanger with ⊕N(CH3)3‐groups in TGCI follows a stoichiometric relationship. This result is discussed in connection with the form of the polymer layer adsorbed on the solid surface.
Mechanical properties of chitosan films: Effect of solvent acid
Authors: Kienzle‐Sterzer Carlos A. , Rodriguez‐Sanchez Dolores , Rha ChoKyun 
Published: April 2003

AbstractThe apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress‐relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one‐component Maxwell model.
High molecular weight derivative of trypsin‐kallikrein inhibitor for potential medical use, 1. Preparation and characterization
Authors: Saudek Vladimír , Drobník Jaroslav , Havranová Marie , Čechová Dana 
Published: April 2003

AbstractBovine trypsin‐kallikrein inhibitor (TKI) was bound on three different water‐soluble hydrophilic carriers derived from poly[N‐(2‐hydroxyethyl)‐D,L‐aspartamide] and containing a binding group (aromatic amine) and an additional modifying group (anionic or hydrophobic). The binding was performed by coupling of diazonium salts formed on the carrier with tyrosines in TKI. The product was characterized by means of sedimentation measurement, viscometry, electrophoresis, amino acid analysis, GPC, and antiproteolytic activity. TKI was found to be attached to the carrier by one or two tyrosines, the latter case being more frequent than it would correspond to independent random reactivity of the accessible tyrosines and the carrier molecules are crosslinked by the attached TKI. This is due to a fraction of two point attached TKI, as estimated according to a tree‐like model. All three samples preserved good activity toward trypsin and chymotrypsin.
Kinetics of the formation of salts of dibasic acids with hexamethylenediamine in 1‐propanol and bifunctional catalysis by the solvent
Authors: Amirtha Nagarajan , Ganesan Ramachandran 
Published: April 2003

AbstractThe kinetics of the reaction between hexamethylenediamine (HMD) and dibasic acids (malonic, succinic, glutaric, and adipic acid) were studied in the temperature range 18–42°C using 1‐propanol as solvent. The total order of the reaction is two, first order in HMD and first order in the dibasic acid. The stoichiometry of the reaction is 1:1 and NMR and IR spectral analyses show that the product is an organic salt with and groups present. A mechanism was proposed in which a proton is transferred from the acid molecule to the base through a solvent molecule which acts as a bifunctional catalyst (both as a proton‐acceptor and proton donor). Values of the rate constants, Arrhenius activation energies, preexponential factors, and entropies of activation are consistent with the proposed mechanism. There is a very strong evidence to show that the “half‐anion” produced in the first ionization of the dicarboxylic acids is the real reactive species.
Sorption of water in hydrophilic polymers, 2. Thermodynamics of mixing of water with poly(2‐hydroxyethyl methacrylate) and with poly[2‐(2‐hydroxyethoxy)ethyl methacrylate]
Authors: Pouchlý Julius , Beneš Svatopluk , Máša Zdeněk , Biroš Ján 
Published: April 2003

AbstractSorption isotherms and heats of immersion of water in poly(2‐hydroxyethyl methacrylate) (PHEMA) and in poly[2‐(2‐hydroxyethoxy)ethyl methacrylate] (PHEOEMA) were determined at 25°C and the Gibbs energy, enthalpy and entropy of mixing were calculated from the data. The results confirm that the physical state of the polymer plays a decisive role in the thermodynamics of sorption. At the temperature of measurement, pure PHEMA is in the glassy state and after sorption of a certain amount of water it passes into the viscoelastic state. Similar to other cases of mixing of a glassy polymer with a low‐molecular weight liquid, the entropy and enthalpy changes are negative, with contributions due to the difference between the physical states of both pure components predominating in them. The thermodynamics of liquid mixtures can be used only for PHEOEMA which at 25°C is in the viscoelastic state. The mixing of water (especially of the first additions) with PHEOEMA is exothermal, being at the same time connected with a negative residual entropy, the effect of which predominates at 25°C. As a result, the affinity of water to the polymer, expressed through a change in the Gibbs energy, is comparatively weak. This is why in this system no strongly bound water is involved, even if the ΔH and ΔS values indicate some sort of increase in ordering during mixing.
Synthesis, characterization, and electrical conductivity of polyesterification products with tetrathiafulvalene units, and their TCNQ complexes
Authors: Koßmehl Gerhard , Rohde Michael 
Published: April 2003

AbstractPolyesterification products with tetrathiafulvalene units 3a–e were prepared from tetrathiafulvalenedicarbonyl dichloride (1) and various α,ω‐diols (2a–e) containing 2 to 16 methylene groups. The red to brown products 3a–e with melting points between 235°C and 128°C are insoluble in all common organic solvents, except for 3e which is soluble in hot DMF. Molecular weights determined by vapor pressure osmometry as well as from elemental analysis data have been found to be ≥2000. The structures were proved by IR, MS, and electronic spectra. The electrical conductivities of 3a–e are between 4 . 10‐8 and 4 · 10‐13 Ω‐1· cm‐1. In TCNQ complexes the electrical conductivities are enhanced by one to five orders of magnitude.
A comment on the estimation of random branching from viscosity measurements
Authors: Mrkvičková Libuše , Quadrat Otakar 
Published: April 2003

AbstractThe hydrodynamic behaviour of polydisperse branched copolymers of methyl methacrylate with a small amount of ethylene dimethacrylate was investigated in several solvents possessing different “solvent power”. It was found that with increasing degree of branching the viscometric expansion coeficient α of these copolymers decreases compared with the expansion of the linear analogs α (before the gel point α/α ≈ 0,5). This phenomenon is demonstrated to be useful in the application of viscometry as a method of estimation or determination of branching.