bluuebunny/crossref_metadata_2025_split huggingface dataset:
The cationic polymerization of 3‐chloro‐2‐methyl‐1‐propene
Authors: Marek Miroslav , Roman Michael , Doskočilová Danica , Pokorný Svatopluk 
Published: April 2003

AbstractThe polymerization of 3‐chloro‐2‐methyl‐1‐propene was investigated at temperatures between 0 and −80°C, using AlCl3 and AlBr3 as initiators. The molecular weights of the resulting oily products depend on the polymerization temperature and varied in the range of the number‐average molecular weight M̄n = 400–620. The course of polymerization was studied and the characteristic groupings in the oligomeris were identified by means of 1H NMR and 13C NMR spectroscopy. Based on the results the mechanism of partial reactions was discussed to explain the new type of propagation in the cationic polymerization.
Liquid crystalline polyurethanes, 1. Polyurethanes based on 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]diphenylethanol
Authors: Tanaka Mamoru , Nakaya Tadao 
Published: April 2003

AbstractPolyurethanes were synthesized from 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]diphenylethanol (3) with diisocyanates such as hexamethylene diisocyanate (4a), 4,4′‐methylenedicyclohexyl isocyanate (4b), 1,3‐cyclohexylenedimethyl isocyanate (4c), 2,4‐toluylene diisocyanate (4d) and 4,4′‐methylenediphenyl isocyanate (4e), and their thermal properties were investigated. The resulting polymers show a liquid crystalline state at 206–230, 160–216, 186–226 and 144–204°C, respectively, and the polymer obtained from 4e has a melting point at 272°C, determined by DSC and polarizing microscopy.
The reaction of nitroxyl radicals with hydroperoxides
Authors: Dulog Lothar , Bleher Rolf 
Published: April 2003

AbstractIn presence of traces of strong acids 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (2) induces the decomposition of hydroperoxides such as tert‐butyl hydroperoxide (1) and cumene hydroperoxide (CHP). 2 disproportionates in presence of hydrogen chloride into 1‐hydroxy‐2,2,6,6‐tetramethylpiperidine (5) and 2,2,6,6‐tetramethyl‐1‐oxopiperidinium chloride (4). This oxammonium salt is the active component which catalyses the decomposition of the hydroperoxide 1 by forming alkylperoxy radicals and the hydroxylamine derivative 5. The peroxy radicals are converted into alkyloxy radicals and molecular oxygen, and the oxyradicals regenerate 2 and an alcohol. The concentration of 2 remains constant through the whole period of the reaction. If 1 is present in an excess over 2 and the oxammonium salt 4, additional protons are needed to decompose the hydroperoxides.
Polymères thiocarboxyliques, 5. Synthèse de poly(oxyéthylène)s à fonction dithioester terminale. Application au traitement de cellules d'électrophorèse
Authors: Perlier Sylvie , Levesque Guy , Depraétère Pierre 
Published: April 2003

AbstractPoly(oxyethylene)s with dithioster end groups were obtained from mono‐ and dihydroxyl terminated commercial polymers by reaction with dimethyl chloroacetamide, subsequent thionation of the amide group, and usual conversion of the thioamides into the dithioesters 14, 15 and 20, 21. The best results were obtained in the syntheses of the S‐carboxymethyl dithioesters (15 and 21). The resulting reactive poly(oxyethylene)s were grafted upon silica tubes and electrophoresis cells, previously activated by aminopropylsilanization. These graftings result in lowering of the surface potential of the tubes and in suppression of the electro‐osmosis flow in an electrophoresis cell tested with a TiO2 standard sample.
Polymer blends based on mesomorphic components, 1. Properties of poly(tetramethylene terephthalate)/poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) blends
Authors: Pracella Mariano , Dainelli Dario , Galli Giancarlo , Chiellini Emo 
Published: April 2003

AbstractBlends of poly(tetramethylene terephthalate) [poly(butylene terephthalate) (PBT)] with a liquid crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) (HTH 10), obtained by solution precipitation, were characterized by optical microscopy, X‐ray diffraction and differential calorimetry. The morphology and phase behaviour of the blends are sensibly influenced by the composition. X‐ray data support the existence of separated crystal phase of the two polymers only for HTH10 contents higher than 30 wt.‐%. An increase of the clearing temperature of the original blends is found with decreasing concentration of the mesomorphic polymer in the range 100 to 30 wt.‐%. On cooling from the isotropic melt, a single crystallization process is observed, whose temperature decreases with increasing amount of HTH10. A large depression of the melting temperature of PBT is found in the composition range 0 to 50 wt.‐% of HTH10. Blends quenched from the isotropic state exhibit one single glass transition temperature, intermediate between those of the starting polymers. The results suggest the occurrence of miscibility phenomena of PBT and HTH10 in the amorphouse phase.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 3. UV absorption study of methylated styrene‐methacrylic acid and styrene‐acrylic acid copolymers
Authors: Wojtczak Zbigniew , S̀witała Maria 
Published: April 2003

AbstractThe microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers prepared in emulsion was studied by UV absorption measurements of their methylated derivatives. For comparative purpose random and graft‐block copolymers were also studied. Hypochromic effects at 259, 262, 264,5 and 269 nm are observed for both random and emulsion copolymers. The dependence of hypochromism at 269 nm on the content of methylated acid units suggests a similar microstructure of random and emulsion copolymers containing up to about 30 mol‐% of acid and differences in the microstructure of emulsion and random copolymers containing greater amounts of acid, especially in case of styrene‐acrylic acid copolymers. Moreover, it is found that UV absorption measurements may be used as a method of estimating the sequence length of styrene units in the copolymers.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 4. 1H NMR study of phenyl rings in methylated styrenemethacrylic acid and styrene‐acrylic acid copolymers
Authors: S̀witała Maria , Wojtczak Zbigniew 
Published: April 2003

AbstractThe sequence distribution in methacrylic acid‐styrene and acrylic acid‐styrene copolymers of various composition prepared in benzene and emusion were studied by using the aromatic proton region in the 1H NMR spectra of methylated copolymers. A digital computer was used to resolve overlapping peaks, and one Lorentzian and two Gaussian curves were fitted for their approximation. The study of random copolymers shows that styrene sequences as small as two and three units are contained. The run numbers and number‐average sequence lengths of styrene calculated for emulsion methacrylic acid‐styrene and acrylic acid‐styrene copolymers show that these copolymers do not have long sequences of styrene units.
Miscibility of mixtures from partially hydrolyzed poly(vinyl acetate) and poly(N‐vinyl‐2‐pyrrolidone)
Authors: Eguiazábal José I. , Calahorra Elena , Cortázar Mila , Guzmán Gonzalo M. 
Published: April 2003

AbstractPolymers with different compositions of vinyl alcohol and vinyl acetate units (P(VA‐VAc)), obtained by alcoholysis of poly(vinyl acetate) with sodium methoxide, were mixed with poly(N‐vinyl‐2‐pyrrolidone) (PVP). The miscibility was studied observing glass transition temperatures by differential scanning calorimetry (DSC). The calorimetric results indicate that for vinyl alcohol unit contents in P(VA‐VAc) of roughly 70 wt.‐% or more, P(VA‐VAc)/PVP blends are fully miscible, whereas blends obtained from P(VA‐VAc) with vinyl alcohol contents lower than the above mentioned values are only partially miscible or even immiscible. The miscibility is attributed to hydrogen bond interactions between hydroxyl groups in P(VA‐VAc) and the carbonyl group of PVP.
Dielectric properties of a liquid crystalline siloxane copolymer
Authors: Pranoto Hendro , Bormuth Franz‐Josef , Haase Wolfgang , Kiechle Ulrich , Finkelmann Heino 
Published: April 2003

AbstractAn investigation on the molecular dynamics of a liquid crystalline side chain polymer using the dielectric relaxation method on oriented samples in the frequency range of 0,1 to 10 000 kHz is presented. The compound under investigation is a polysiloxane copolymer with two different mesogenic side chains and a phase sequence glassy‐smectic A‐nematic‐isotropic. Three main relaxation processes are found and assigned to the rotation of the side chains around the main chain, the glass transition process coupled with side chain motions, and a local motion in the glassy state, respectively. Evidence is found for a layered arrangement of the polymer main chain in the smectic phase and for a parallel correlation between the transverse components of the dipole moments.
The effect of cyclotetramer on the melting and crystallization behavior of poly(ethylene terephthalate)
Authors: Yu Tongyin , Bu Haishan , Jin Yimin 
Published: April 2003

AbstractIn the course of polycondensation of terephthaloyl chloride and ethylene glycol with subsequent baking, a cyclotetramer (M4) was isolated as a by‐product besides poly(ethylene terephthalate) (PET) and was identified by means of DSC, IR, GC‐MS and elemental analysis. The effects of this cyclotetramer M4 on the crystallization and on the morphological behavior of PET in the absence of residual catalyst were studied. It was found that M4 is soluble in the polymer melt. Thus, it only serves as a diluent and does not show any nucleation effect on the crystallization of PET.
Dependence of the kerr constants of benzene, p‐dioxane and poly(oxydiethylene terephthalate) on temperature
Authors: Mendicuti Francisco , Saiz Enrique 
Published: April 2003

AbstractThe Kerr constants of benzene, p‐dioxane, and of poly(oxydiethylene terephthalate) (PDET) in p‐dioxane solution were measured at several temperatures. As in the case of some other pure liquids reported in the literature, the values obtained for benzene and p‐dioxane are fitted by equations of the type mK = a + b · T−1 with a = (0,3 ± 0,6) · 10−26 m5 · V−2 · mol−1 and b = (16,0 ± 1,8) · 10−24 m5 · V−2 · mol−1 · K for benzene and a = (3,9 ± 0,9) · 10−26, b = −(8,2 ± 2,6) · 10−24, in the same units, for p‐dioxane. The values of the mean molar Kerr constant per repeating unit 〈mK〉/x extrapolated to infinite dilution in the case of PDET yield a values of d(〈mK〉/x)/dT = (13,5 ± 0,9) · 10−27 m5 · V−2 · mol−1 · K−1, in excellent agreement with the calculated result of 13,2 · 10−27 (in the same units) reported in the literature.
Stress‐optical behavior of atactic polypropylene networks upon elongation
Authors: DeBolt Lawrence C. , Riande Evaristo 
Published: April 2003

AbstractElastomeric networks prepared from atactic polypropylene were crosslinked with γ‐irradiation. The stress‐optical behavior of the unswollen networks was studied over a variety of elongation ratios and temperatures. At constant length, the stress f/A increases markedly at the glass transition temperature Tg, but the value of Tg does not change discernibly with increasing elongation. The unswollen networks exhibit negative birefringence for values of the elongation ratio λ below 1,8; however, for values of λ > 1,8, the birefringence becomes positive. This behavior was attributed to the presence of crystallites in the unswollen networks. Polypropylene networks, swollen with 1,3,5‐triethylbenzene and tetradecane, were also studied with regard to their stress‐temperature and birefringence‐temperature relationships. Whereas both the birefringence and stress of elongated networks swollen with the former solvent show a linear dependence on temperature, the birefringence of elongated networks swollen with tetradecane exhibits an anomalous increase at low temperatures which was attributed to poorly developed crystallinity. Values of the birefringence and stress corresponding to swollen networks were used to calculate the values of the optical configuration parameter Δa and its temperature coefficient. Theoretical calculations carried out with the rotational isomeric state model were used to evaluate Δa as a function of the stereoregularity of the chains. It was found that Δa decreases as the proportion of meso diads Pm increases, remaining almost constant for values of Pm > 0,7. The theoretical results of Δa and d In Δa/dT obtained for Pm > 0,4 reproduce very satisfactorily the experimental results obtained on the networks swollen with 1,3,5‐triethylbenzene.
Synthesis of polymers containing pyromellitdiimide and benzimidazole or pyrrolobenzimidazole moieties and of their corresponding model compounds
Authors: Yang Chin‐Ping 
Published: April 2003

AbstractSome new polymers and model compounds were obtained from the reaction of 2‐phthalimidosuccinic anhydride (5) or 2,2′‐pyromellitdiimidodisuccinic anhydride (10). The way of the ring‐opening reaction of the anhydrides was found to depend on the solvents used. In some polar solvents such as DMSO, DMAC, NMP and DMF, β‐orientation occurs, but in THF, 1,4‐dioxane or acetone α‐orientation is preferred, which can be followed quantitatively by NMR spectroscopy. Subsequent dehydration to the pyrrolobenzimidazoles was found to proceed via the corresponding benzimidazolylcarboxylic acids rather than via the cyclic imides, the formation of the β‐from being faster than that of the α‐form. Polymer 24, containing pyromellitdiimide and pyrrolobenzimidazole moieties in the main chain, was synthesized by a three‐step reaction starting with 10 and 3,3′‐diaminobenzidine (8). In the first step, the poly(aminoanilic acid) (12), containing pyromellitdiimide rings, was prepared in a polar solvent. In the second step, condensation to the corresponding poly(imidoimidazolylpropionic acid) (20) was carried out thermally in solution or in solid state at 80–160°C. In the final step, the conversion into polymer 24 was performed by heating at a higher temperature or at reflux in acetic anhydride. The structures of the polymers were identified spectroscopically by comparison of the IR and NMR spectra with those of the corresponding model compounds.
Darstellung oligomerer und polymerer Cyclohexanokronenether
Authors: Blasius Ewald , Klein Wolfgang 
Published: April 2003

AbstractCyclohexano anellated crown ethers, bis(phenylcyclohexano)‐18‐crown‐6 and benzo‐cyclohexano‐18‐crown‐6 with cis‐ and trans‐ configuration at the cyclohexane ring were synthesized. The phenyl substituted crown ethers react with formaldehyde to form a crosslinked resin. Depending on the reaction conditions, the benzo anellated crown ethers give soluble polymers and/or linear and cyclic oligomers. Cyclic products could be isolated. Crosslinked polymers were synthesized from benzo‐cyclohexano‐18‐crown‐6 using additionally to formaldehyde a dialdehyde or a diarly compound.
Modification of amylose with diketene
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Riofrio Alicia 
Published: April 2003

AbstractThis work deals with the modification reaction of amylose with diketene using tertiary amines as catalysts. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. A linear dependence of the reaction rate on polymer, diketene and pyridine concentrations was found. The activation energy was found to be 27,2 kJ/mol (6,5 kcal/mol). Polymeric chelates between partially modified amylose and cupric ions (Cu2+) were prepared. However, not all of the β‐keto ester groups in the partially modified amylose participate in binding the cupric ions.
Polymerisationsauslösung mit substituierten ethanen, 8. Polymerisation von styrol
Authors: Błedzki Andrzej , Braun Dietrich 
Published: April 2003

AbstractThe free radical polymerization of styrene initiated by 1,1,2,2‐tetraphenyl‐1,2‐diphenoxyethane (TPPA) can be described as a kind of dead end polymerization. At the beginning of the polymerization, mainly oligomers are formed by primary radical chain termination. These oligomers can be characterized by thin layer and gel permeation chromatography and by mass spectroscopy. With increasing conversion and decreasing initiator concentration the molecular weight of the polymers is increasing. Contrary to the polymerization of methyl methacrylate with the same initiator, in the case of styrene the formed oligomers are not able to initiate once more the polymerization because the end groups formed by initiator radicals and styrene units are rather stable at normal polymerization temperatures (60 – 100°C).
Influence of termination and transfer on molecular weight distribution of polymers, 5. Chain transfer to monomer and impurity termination
Authors: Yuan Cui‐ming , Yan De‐yue 
Published: April 2003

AbstractIn this paper, the simultaneous effect of impurity termination and chain transfer to monomer on the molecular size distribution for the anionic polymerization with instantaneous initiation was studied theoretically in detail. The rigorous expressions for the molecular size distribution function and other molecular parameters were derived from a set of kinetic differential equations by means of the non‐steady state method. In accordance with these expressions, several examples of numerical calculation are given and a comparison is made between the polymerization system with chain transfer to monomer and that without monomer transfer.
Orientation process in thermotropic comb‐like polymers
Authors: Roth Hanna , Krücke Bernd 
Published: April 2003

AbstractThe influence of magnetic fields on the orientation of comb‐like silicon polymers was investigated by NMR methods. The sensitivity of proton NMR spectroscopy to phase transitions could be proven. Glass transition temperatures could be estimated by means of the super Lorentzian line shape of the wide line NMR signals. Magnetic fields of 2,1 T in connection with special temperature programs are able to effect a macroscopic orientation of the mesogenic side groups which are connected by mobile spacers to the backbone of the flexible polymer. The state of this orientation is preserved in a broad temperature range. The order parameter is derived as a function of temperature.
Free‐radical polymerization of methyl methacrylate at very high conversions, 2. Study of the kinetics of initiation by benzoyl peroxide
Authors: Stickler Manfred , Dumont Emil 
Published: April 2003

AbstractThe initiation kinetics of the free‐radical polymerization of methyl methacrylate at very high monomer conversions was investigated at 80, 100, and 120°C. Using a HPLC (high performance liquid chromatography) analytical technique with UV detection, the consumption of both monomer and initiator as well as the formation of reaction products of the latter could be followed. It was found that (besides very small amounts of biphenyl and benzoic acid) phenyl benzoate is the main decomposition product. The experimental results were analyzed quantitatively with the help of a reaction scheme which takes into account the most important pathways of that complex chemical reaction system. Thus, it was found that, due to the very strong cage effect in the present polymerization system, the experimentally accessible (apparent) first order rate constant of initiator decomposition is substantially lower than that for the primary cleavage of a benzoyl peroxide molecule. Efficiencies of chain initiation were calculated to be in the range of 0,1 to 0,2 in the (nearly) glassy polymer matrix.
Simulation of coupled modification reactions of polymers, 1. Monosubstitution and double bond shift of 1,4‐polybutadiene
Authors: Hummel Klaus , Martl Michael G. 
Published: April 2003

AbstractComputer simulation is well suited for theoretical investigation of coupled modification reactions of polymers to make subsequent comparison with experimental results. The percentage of units resulting in 1,4‐polybutadiene for substitution coupled with partial double bond shift is calculated for a simplified model. In the computer program three pseudo‐random number generators are used for simulation. The substitution degree SU and the shift degree SH describe the modification. In the general case, 22 chemically different units result. Borderline cases are SH = 0 with at most 3 units and SH/SU = 1,0 with at most 12 units. A detailed investigation is carried out for the especially interesting range SU = 0,1 to 0,5 and SH/SU = 0,1 to 0,5.
The effect of units derived from diethylene glycol on crystallization kinetics of poly(ethylene terephthalate)
Authors: Yu Tongyin , Bu Haishan , Chen Jianhua , Mei Jibang , Hu Jialun 
Published: April 2003

AbstractThe effect of units derived from diethylene glycol (DEG) on the crystallization behaviour and linear growth rate of spherulites of poly(ethylene terephthalate) (PETP) free of metal catalyst residues, is studied by means of differential scanning calorimetry (DSC), small‐angle light scattering (SALS), polarized light microscopy (PLM), and transmission electron microscopy (TEM). The results show that the crystallization behaviour does not depend only on the temperature of crystallization, but also on a large scale on the content of DEG. In hot crystallization, the rate of PETP crystallization decreases with increasing DEG content; in cold crystallization, this effect is not so prominent. The higher the DEG content, the smaller is the number of nuclei and therefore the linear growth rate of PETP and, at the same time, the size of the spherulites becomes greater.
Miscibility of linear and branched polyethylene in the liquid state
Authors: Illers Karl‐Heinz , Köhnlein Ernst 
Published: April 2003

AbstractHDPE/LDPE blends and the pure components were crosslinked either by irradiation or by di‐tert‐butyl peroxide in the liquid state. The degree of crosslinkage was characterized by the reciprocal degree of swelling Q−1 (xylene, 2 h, 140°C). Above a critical degree of crosslinkage corresponding to Q−1 = 0,2 the DSC curves of HDPE/LDPE blends show only one single crystallization peak on cooling from the melt and only one single melting peak on subsequent heating. This is an unequivocal proof for the single phase structure of HDPE/LDPE blends in the liquid state. Crosslinking with Q−1 ≥ 0,2 prohibits fractional crystallization and forces the unbranched CH2 sequences of both components between the crosslinks into one crystal lattice.
Synthesis and properties of polyurethanes derived from diaminodianhydroalditols
Authors: Thiem Joachim , Lüders Harald 
Published: April 2003

AbstractThe readily accessible 1,4:3,6‐dianhydroalditols with D‐gluco‐ (1), L‐ido‐ (5) and D‐mannoconfigurations (6) were efficiently transformed into the 2,5‐diamino‐1,4:3,6‐dianhydro‐2,5‐dideoxyalditols with D‐gluco‐ (10), D‐manno‐ (13), and L‐ido‐configuration (16). Interfacial polycondensation of these chiral heterocyclic diamines as well as ethylene‐ and tetramethylene diamine with the bis(chloroformate) 3 derived from 1,4:3,6‐dianhydro‐D‐sorbitol gave the polyurethanes 17 to 21. Their number‐average molecular weights were determined to be M̄n ≈ 3000 corresponding to an average degree of polymerisation P̄n ≈ 20. Inherent viscosities were measured, and 1H NMR spectroscopy as well as DSC gave informations about the molecular structure and some polymer properties.