bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and properties of polyamides from glucosamine and glucose derivatives
Authors: Thiem Joachim , Bachmann Frank 
Published: April 2003

AbstractStarting from D‐glucosamine, the synthesis of various differently modified methyl and benzyl 2,6‐diaminosaccharides 11, 12, 17 and 18 was accomplished. Interfacial and solution polycondensation of those diamino derivates with aromatic and aliphatic acyl chlorides yielded polyamides 34, 35, 36 and 37a–d which were characterized by 1H NMR spectroscopy and their inherent viscosities. The presence of an anomeric benzyl group in 12 did not decrease the reactivity of the 2‐amino function. The free hydroxy functions in polyamides 35a–b were acetylated to give polyamides 39a–b. Partially blocked polyamides 36a–d had similar properties as unprotected polyamides 34–35a–d. Under corresponding conditions di‐O‐acylated diaminosaccharide 18 gave only oligomer. Number‐average molecular weights were obtained from gel‐permeation chromatography to be 10300 < M̄n < 24000 (interfacial polycondensation), corresponding to number‐average degrees of polymerization up to P̄n = 64, whereas polycondensation in solution afforded only M̄n values between 2000 and 3000. Starting with D‐glucose the synthesis of a C‐glycosidic diaminosaccharide 28 was developed. This reacted to polyamides 38a–d which showed thermal stability up to 280°C.
Polyéthers aromatiques à motifs azoïques, 2. Note sur I'hétéropolycondensation en milieu basique du azobenzène‐4,4′‐diol avec le 1,4‐bis(chlorométhyl)‐2,5‐diméthylbenzène
Authors: Radu Stelian 
Published: April 2003

AbstractThe influence of the concentration of the reactants (bis(chloromethyl) derivative, NaOH) and of the reaction time upon the intrinsic viscosity and the yield of the polymers synthesized by the heteropolycondensation of sodium azobenzene‐4,4′‐diolate with 1,4‐bis(chloromethyl)‐2,5‐dimethylbenzene is presented. The optimum conditions of polymer synthesis are established.
Synthesis of uniform poly(aspartic acids)
Authors: Rao Vanga S. , Lapointe Philippe , McGregor Donald N. 
Published: April 2003

AbstractPoly(aspartic acids) of different chain lengths (11, 14, 18, 24, 30, 52, 58, ≈ 115) were prepared, for the use in aminoglycoside‐induced nephrotoxicity inhibition studies, some in their pure L‐ or D‐configuration and in pure α‐linkage form by the polymerization of α‐amino acid N‐carboxyanhydride (NCA) derivatives with a variety of dialkyl aspartate molecules as primary amine initiators. The primary amine chosen served as an internal reference in the 1H NMR spectrum for the estimation of the degree of polymerization (chain length) in these molecules. Poly(aspartic acids) with varying amounts of D and L asymmetric centres and in pure α‐linkage from were also prepared. Poly[(α‐co‐β)(L‐co‐D) aspartic acid] was prepared by a simplified thermal polymerization procedure for biological studies and also to study the tacticity effects in its 13C NMR spectrum. A qualitative correlation was demonstrated between the retention times from gel‐permeation chromatographic analysis and the 1H NMR method used to estimate the polymer chain length.
New polymer syntheses, 64. Thermotropic polyesters derived from 4,4′‐biphenyldiol and terephthalic acids with one long aralkoxy side chain
Authors: Kricheldorf Hans R. , Bürger Rolf 
Published: April 2003

AbstractA new class of monosubstituted terephthalic acids was prepared from commercial dimethyl nitroterephthalate by a three‐step procedure. This procedure consists of the nucleophilic substitution of the nitrogroup by 4‐mercaptophenol followed by alkylation of the phenolic OH group and saponification of the dimethylester groups. Four polyesters were prepared by polycondensation of 4,4′‐biphenyldiol or its bis(trimethylsilyl) ether with four new substituted terephthaloyl chlorides. The “silyl method” was found to give the highest molecular weights. All polyesters are semicrystalline and form nematic melts. In three cases the melting points range from 250 to 275°C. All polyesters are soluble in a variety of organic solvents.
Copolymers of ethyl p‐vinylbenzenesulfonate for the preparation of polyelectrolytes of reproducible ion content
Authors: Woeste Govert , Meyer Wolfgang H. , Wegner Gerhard 
Published: April 2003

AbstractEthyl p‐vinylbenzenesulfonate (ESS) for which a new synthesis is described has been copolymerized with vinylcarbazole, styrene, p‐methylstyrene and p‐bromostyrene in N,N‐dimethylformamide at 60°C using azoisobutyronitrile as initiator. Copolymer compositions and copolymerization parameters have been evaluated. Q, e‐values for ESS are 4,19 and ‐0,11. Thermal properties of the copolymers have been investigated by differential scanning calorimetry and thermogravimetric analysis. Polyelectrolytes have been prepared either by polymer analogous hydrolysis of the sulfonic acid esters followed by conversion of the free acids into alkali metal salts or by using the alkylating properties of the esters towards tertiary amines or pyridines to form the appropriate sulfonic acid ammonium or pyridinium salts. The latter method offers the opportunity to synthesize polyelectrolytes with a well defined content of chromophores.
Stopped‐flow fourier transform infrared studies in polymer chemistry
Authors: Brittain William J. , Aquino Eugene C. , Dicker Ira B. , Brunelle Daniel J. 
Published: April 2003

AbstractThe application of stopped‐flow FT‐IR spectroscopy to group transfer polymerization (GTP) and cyclic oligomeric carbonate formation is described. The influence of catalyst structure, propagating end stereochemistry and degree of polymerization (DP) on the rate of monomer addition was examined for GTP. Also, the major GTP termination process was identified and characterized. Model reactions were used to study the kinetics of acyl ammonium salt formation and subsequent conversion to urethane. These results were used to further develop the mechanism of bisphenol A‐bischloroformate macrocyclization.
Chemical structure of plasticizers, compatibility of components and phase equilibrium in plasticized cellulose diacetate
Authors: Suvorova Anna I. , Demchik Lyudmila Yu. , Peshekhonova Aza L. , Sdobnikova Olga A. 
Published: April 2003

AbstractThe phase equilibrium of plasticized polymer systems on the basis of cellulose diacetate and ethylene glycol esters of dibasic aliphatic acids (from oxalic acid to 1,10‐decanedicarboxylic acid) was studied and the solubility parameters and the thermodynamic interaction parameters of the components were calculated. It is shown that an increase in molecular weight of the plasticizers leads to a lower miscibility of the components, a fact which is reflected in a regular rise of the upper critical solution temperature (UCST), a tendency of the systems for gelation, a decrease of the solubility parameter of the plasticizer δ1, and a growth of the interaction parameters χH and χ12. The results are discussed in terms of the existing theories for polymer solutions.
The role of additives for the improvement of δ‐TiCl3 catalyst performance
Authors: Maria Luiz Claudio de Santa , Coutinho Fernanda M. B. , Alencar Cláudia 
Published: April 2003

AbstractThe influence of ethylaluminium compounds (AIEt3 and AICIEt2) modified by 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT), tributylamine (TBA) and triphenylphosphine (TPP) on the polymerization of propene was investigated using catalysts based on TiCI3 modified by internal Lewis bases. Two catalysts were employed in this study, one (Cat. A) was prepared by the reduction of TiCI4 complexed with dibutyl ether (DBE)—mole ratio DBE/TiCI4 = 0,67—with AlClEt2 and the other one (Cat. B) was prepared in the same way, but a second internal base (ethyl benzoate (EB)) was added in a mole ratio EB/TiCl3 = 0,04. Activity and stereospecificity of the catalyst systems were strongly affected by these modified cocatalysts. The role of the modifiers is discussed.
Intramolecular interaction of chain molecules: Second osmotic virial coefficients and intrinsic vicosities
Authors: Wolf B. A. 
Published: April 2003

AbstractIn a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two‐step process: In the first step the molecules are detached from each other by the addition of solvent—keeping their dimensions constant—and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra‐molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two‐parameter approach yields A2 = A + σ M−(1−a) for the dependence of A2 on the molecular weight M of the polymer; a is the exponent of the Kuhn‐Mark‐Houwink equation and σ a parameter measuring the effects associated with the second step (becoming zero if the coil dimensions do not depend on polymer concentration). A test of the above relation by means of published material demonstrates its superiority over other two parameter theories: It can describe the actually measured A2(M) well down into the region of oligomers without an additional parameter and it comprises the conceptual advantage of explaining experimental observations concerning ∂A2/∂M > 0 or ∂A2/∂M ≈ 0 for high A2 values.
Non‐destructive determination of the residual monomer content in polymers by Raman spectroscopy
Authors: Dywan Frank , Hartmann Brigitte , Klauer Stefan , Lechner Manfred D. , Rupp Romano A. , Wöhlecke Manfred 
Published: April 2003

AbstractBy a comparative study and by calibration, Raman spectroscopy is established as a non‐destructive method for the determination of the monomer concentration in solid poly(methyl methacrylate) samples. Although the effect of the internal field on the refractive index and on the Raman intensity of a polymer solution in a monomer is considered, the Raman scattering cross section of the carbonyl stretching vibration of the monomer turns out to be more than twice as large as that of the polymer.
Composites from furfuryl alcohol and inorganic solids by cationic initiation, 2. Spectroscopic studies of poly(furfuryl alcohol)‐silica composites obtained by trifluoroacetic acid initiation
Authors: Spange Stefan , Schütz Heidrun , Martinez Ricardo 
Published: April 2003

AbstractFurfuryl alcohol polymerizes in a suspension of dispersed inorganic solids such as silica in 1,2‐dichloroethane using trifluoroacetic acid as initiator. Depending on the experimental conditions the reactions load to (1) agglomeration of particles, (2) composite and soluble polymer formation, (3) composite formation. The chemical structure of the soluble polymers is not regular but the furfurylic sequence is predominant. The polymer grafted on the surface of the solid is a strongly reticulated poly(furfuryl alcohol), which also possesses conjugated double bonds that are involved in an acid‐base equilibrium with trifluoroacetic acid.
Linear‐temperature programmed pyrolysis of thermoresistant polymers — mass and FTIR spectrometries, 2. Aromatic polyesters and copolyesters
Authors: Hummel Dieter O. , Neuhoff Ulrich , Bretz Anke , Düssel Heinz‐Jürgen 
Published: April 2003

AbstractLinear‐temperature controlled pyrolysis with subsequent analysis of the pyrolyzates (volatiles and residue) by 18 V electron‐impact mass spectrometry (EIMS) and FTIR spectrometry, respectively, yields optimal informations on the thermal degradation mechanisms of heat‐resistant polymers. In the present paper results with aromatic polyesters are reported. Poly(4‐oxybenzoyl) firstly (675 K) releases residual educt (acetoxybenzoic acid), solvent (hexahydroterphenyl), phenol and oligomers. In the temperature range of maximum decomposition (Tmax = 815 K) several consecutive processes take place. At 760 K, “monomer” (oxybenzoyl) and two series of oligomers with different endgroups are set free. At 815 K, formation of phenol, and at 845 K. formation of diphenyl ether are the dominating process. The maxima of CO2 and CO release are at 790 K and 825 K, respectively. In the residue, diaryl ketone, 9‐fluorenone and phenolic structures were observed. Mechanisms including Fries‐analogue rearrangements are discussed. A typical poly‐(4‐oxybenzoyl‐ran‐2‐oxy‐6‐naphthoyl) (“Vectra A 950”) with 73 mol‐% oxybenzoyl units produced, during the “evaporation phase” (640 K) and in addition to oxybenzoyl “monomer” and oligomers, oxynaphthoyl and a series of hetero‐fragments containing one oxynaphthoyl unit and one or two oxybenzoyl units. At 785 K (close to Tmax), the formation of phenol, CO2, CO and oxybenzoyl was predominant. In the residue, the formation of diaryl ketone, dibenzofuran and 9‐fluorenone structures was observed. Mechanisms are discussed in analogy to the degradation of poly(4‐oxybenzoyl).
Polylactones 26. Lithium alkoxide‐initiated polymerizations of L‐lactide
Authors: Kricheldorf Hans R. , Boettcher Caroline 
Published: April 2003

AbstractLithium alkoxide‐initiated polymerizations of L‐lactide were conducted in toluene at 50°C. The initiator solutions were prepared in situ from butyllithium and benzyl alcohol, 1‐tetradecanol, diethylene glycol monobutyl ether or poly(ethylene glycol) monomethyl ether. These lithium alkoxides initiate the polymerization via nucleophilic attack, forming alkyl ester end‐groups as evidenced by 1H NMR spectroscopy. High yields, high molecular weights and a relatively high optical purity (up to 95%) of the isolated poly(L‐lactide) may be obtained.
Evaluation of the kinetic parameters for styrene polymerization and their chain length dependence by kinetic simulation and pulsed laser photolysis
Authors: Deady Mark , Mau Albert W. H. , Moad Graeme , Spurling Thomas H. 
Published: April 2003

AbstractPulsed laser photolysis (PLP) has been employed to determine propagation rate constants kp for styrene polymerization in benzene over a wider temperature range (20−80°C) than previously converd. It is proposed that a small chain length dependence of kp (overall) may, in part, be a consequence of a marked chain length dependence of kp for the first few propagation steps [i.e. kp(1) > kp(2) < kp(3) ≥ kp(≥4)]. The propagation rate constant for styrene polymerization is given by the expression: In kp = 16,09 − 28950/(RT) (overall) or In kp = 16,47 − 30084/(RT) (chain length ≥ 4). Kinetic simulation has been applied both as an aid in data analysis and to demonstrate the reliability of the PLP technique for evaluation of propagation rate constants (kp) in radical polymerization. This has been achieved by examining the sensitivity of the molecular weight distribution of polymers formed in PLP experiments to the values of the kinetic parameters associated with polymerization and their chain length dependence. The termination rate constants (kt = kc + kd) and the ratio of combination to disproportionation (kc: kd) markedly affect the molecular weight distribution of polymer formed in PLP experiments. The prospects for evaluating the values of kt, its chain length dependence and kc : kd by direct analysis of the molecular weight distribution are discussed in the light of these results.
Kinetic and ESR studies on the radical polymerization. radical‐initiated copolymerization of the diethyl itaconate‐SnCl4 complex and styrene
Authors: Nakamura Hiroyuki , Seno Makiko , Tanaka Hitoshi , Sato Tsuneyuki 
Published: April 2003

AbstractThe copolymerization of diethyl itaconate(1) (M1) and styrene (2) (M2) with dimethyl 2,2′‐azoisobutyrate (3) was performed in benzene at 50°C, and the following copolymerization parameters were obtained: r1 = 0,34, r2 = 0,35, Q1 = 0,93 and el = +0,66. The copolymerization system was found to involve ESR1Electron spin resonance.
‐observed propagating polymer radicals at low monomer feed composition (f2) of 2. The apparent rate constant of termination increased rapidly with f2. The ESR‐determined values of the apparent propagation rate constant of the copolymerization were lower than those calculated on the basis of the Mayo‐Lewis model, suggesting a significant penultimate effect in the copolymerization. On the other hand, the copolymerization of the 1‐SnCl4 complex (M1) and 2 (M2) at 50°C yielded a nearly alternating copolymer independently of the monomer feed composition. The propagating polymer radicals were ESR‐observable even up to f2 = 0,8. The ESR‐determined apparent rate constant (kp) of propagation showed a maximum near f2 = 0,5. From the relationship between kp and f2, the rate constants of cross‐propagations of the present alternating copolymerization were evaluated as k12 = 483 and k21 = 510 L. mol−1 · s−1. Comparison of the k21 value and the reported propagation rate constant (209 L · mol−1 · s−1) of homopolymerization of 2 leads to the conclusion that the alternating copolymerization via free‐monomer propagation mechanism originates from a pronounced penultimate effect suppressing homopropagation of 2, but not from enhanced cross‐propagation.
Studies of the autoxidation of phenols catalyzed by the cobalt(II) complex of disodium N,N′‐bis(salicylidene)‐ethylenediamine‐5,5′ ‐disulfonate bound to colloidal anion exchange resin
Authors: Hassanein Mahmoud , Aly El‐Saied A. , Abbas Yousf A. , El‐Sigeny Samia M. 
Published: April 2003

AbstractTo overcome mass transfer limitations which are usually encountered on immobilizing active catalysts, cationic latex particles were used as support for the cobalt(II) complex of disodium N,N′‐bis(salicylidene)ethylenediamine‐5,5′‐disulfonate (1). The cationic latex 2 was prepared by emulsion copolymerization of chloromethylstyrene (m/p‐isomer mixture 60/40) and divinylbenzene (m/p‐isomer mixture) followed by treatment with trimethylamine. The latexbound catalyst from 1 and 2 was found to considerably increase the reaction rate of the autoxidation of 2,6‐di‐tert‐butylphenol in water as compared with the conventional polymer‐free system. Reaction products were identified as the oxidative coupling product 3,3′,5,5′‐tetra‐tert‐butyldiphenoquinone (3,3′,5,5′‐tetra‐tert‐butyl‐4,4′‐dioxo‐1,1′‐bicyclohexa‐2,5‐dienylidene) and 2,6‐di‐tert‐butyl‐1,4‐benzoquinone. All reactions showed an induction period before the start of dioxygen consumption. The rate of autoxidation in the three‐phase mixtures of water, latex particles, and phenol droplets was not affected significantly by the method of mixing. The reaction rate increased as the concentration of 1 increased. Increasing the partial pressure of dioxygen in the range between 0,25 and 1,0 atm (2,53. 104 – 1,01. 105 Pa) gave a small increase in rate. The colloidal latex catalyst from 1 and 2 showed some loss of activity after successive runs.
Synthesis of crowned initiators and kinetic studies of crowned benzophenone‐sensitized photopolymerization of methyl methacrylate
Authors: Yuan Lihua , Tian Baozhi , Huang Shu 
Published: April 2003

AbstractA series of crowned benzophenones (CBPs) and benzoins was synthesized. Application of CBPs as initiators for the photopolymerization of methyl methacrylate (MMA) indicated a kinetic similarity between benzophenones and crowned benzophenones. With CBPs a rate enhancement was observed which was attributed to the higher light absorptance in the presence of crown ether structure. UV spectra confirmed the existence of the crown species as end groups of the polymer chains.
Highly crosslinked chitosan gels
Authors: Tikhonov Vladimir E. , Yamskov Igor A. , Davankov Vadim A. 
Published: April 2003

AbstractChitosan was crosslinked to varying extents with bis(vinylsulfonyl)arenes as crosslinking agents in homogeneous solution. The effect of reaction conditions on the onset of gelation was investigated. The rate of gelation was shown to depend on the chitosan concentration and the structure of the crosslinking agent used. The degree of crosslinking and content of the remaining pendant double were evaluated. The obtained cnitosan gels swell both in organic solvents and in acidic aqueous solutions.
Copolymerization and copolymers of N‐(2,4,6‐tribromophenyl)maleimide with methyl acrylate and methyl methacrylate
Authors: Janović Zvonimir , Matusinović Tomislav T. , Ranogajec Franjo 
Published: April 2003

AbstractN‐(2,4,6‐Tribromophenyi)maleimide (TBPMI) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in toluene solution using 2,2′‐azoisobutyronitrile as free‐radical initiation. The copolymerization reactivity ratios were found to be for the system TBPMI/MA r1 = 0,095 ± 0,045 (TBPMI) and r2 = 2,17 ± 0,142 (MA) and for the system TBPMI/MMA r1 = 0,037 ± 0,042 (TBPMI) and r2 = 4,32 ± 0,230 (MMA); Q and e values were also calculated. The initial rate of copolymerization, Rp, for TBPMI/MA sharply decreases as the content of TBPMI in the monomer mixture increases but the composition of the feed does not have a strong influence on Rp for the TBPMI/MMA copolymerization system. The course of copolymerization to high conversion is characterized by an increase of conversion up to a mole fraction of TBPMI of 0,7 in the monomer mixture, when MA was used as the comonomer. An opposite behaviour was found with MMA. Its copolymers show a considerable increase of thermal stability as well as of the glass transition temperatures with increasing TBPMI content.
Multi‐detector size‐exclusion chromatography: a novel approach to calibration eliminating lag time estimation
Authors: Suddaby Kevin G. , Sanayei Ramin A. , O'Driscoll Kenneth F. , Rudin Alfred 
Published: April 2003

AbstractIn order to obtain the correct calibration of molecular‐weight sensitive detectors (such as on‐line viscometers or light scattering detectors) in size‐exclusion chromatography, it is necessary to account for the (molecular) non‐uniformity of the calibration standards. This is true even in the case of the narrow molecular weight distribution standards typically commercially available for calibration. Methods of taking this non‐uniformity into consideration are presented. For a multi‐detector size‐exclusion chromatography system calibrated in this way, independent calibration curves can be established for each detector. Thus, at a given hydrodynamic volume, corresponding signals from the different detectors can be obtained. This eliminates the need to estimate additional parameters such as interdetector volumes or lag times for matching signals from different detectors. The practicability of this approach in the analysis of (molecularly) non‐uniform polymers is demonstrated by combining on‐line viscometer and concentration signals (to obtain intrinsic viscosity versus molecular weight information) for two different polymers, viz. polystyrene and poly(methyl methacrylate). The resultant intrinsic viscosity versus molecular weight data is then compared to that predicted from the literature.
Temperature‐responsive graft copolymers for immobilization of enzymes
Authors: Takeuchi Shigeya , Omodaka Izumi , Hasegawa Kiyoshi , Maeda Yasushi , Kitano Hiromi 
Published: April 2003

AbstractA graft copolymer was prepared by coupling of poly(acrylic acid‐co‐acrylamide) (monomer ratio 1:8,5) with poly(N‐isopropylacrylamide) (PIPA) having an amino group at its end. The copolymer with the graft chains obtained [poly(AA‐co‐AAm)‐g‐PIPA] showed a temperature‐responsive phase transition at 34°C in water, and at 26°C in 1‐propanol/water (8:92 vol.‐%). Lipase from wheat germ was covalently bound to the graft copolymer using a water‐soluble carbodimide. The Arrhenius plots of the catalytic activity of the lipase immobilized to poly(AA‐co‐AAm)‐g‐PIPA had a bending point around 25 – 30°C in 1‐propanol/water (8:92 vol.‐%), which is consistent with the temperature‐responsiveness of the carrier polymer. As for lipase immobilized to the graft copolymer poly(AA)‐g‐PIPA, on the contrary, there was no bending point in the temperature dependence of the catalytic activity, probably due to electrostatic repulsion between acrylic acid residues, which perturbs the aggregation of PIPA side chains. The graft copolymer prepared here can be used as a component of temperature‐sensitive devices in various forms.