bluuebunny/crossref_metadata_2025_split huggingface dataset:
Homogeneous polyesters of predetermined length, composition, and sequence: Model synthesis of alternating glycolic‐acid‐co‐(L)‐lactic‐acid oligomers
Authors: Huang Bin , Hermes Matthew E. 
Published: April 2003

AbstractMethods for making monodisperse polyester copolymers of predetermined length, com‐position, and sequence are reported. Alternating oligomers of (L)‐lactic‐co‐glycolic acid (La‐co‐Gl), isosteric with polypeptides, are prepared by solution methods of protecting, coupling, and deprotecting alcohol and acid groups. The carboxylic acid is protected by benzyl ester formation and released by hydrogenation. The hydroxyl group is protected as the methoxyethoxyethyl ether and deprotected with sodium iodide and trimethylsilyl chlo‐ride. Coupling uses dicyclohexylcarbodiimide. End‐capped alternating oligomers containing (GILa)4 and (GILa)8 show polymer properties. They are noncrystalline oils that exhibit discernable Tg. The conformation of GILa and LaGl diads in the polyesters is shown to be similar to isosteric peptide diads GlyAla and AlaGly. Exactly structured, monodisperse polyesters suggest a chemical parallel to proteins. Designed struc‐tural templates combining sheet‐form (Gl)n and helical (La)n segments are at‐tractive synthesis targets. The solution preparations reported here can be applied, but it is suggested that biosynthetic methods for introducing single ester units into peptide chains be adapted to synthesize precisely fashioned polyesters. © 1995 John Wiley & Sons, Inc.
Crowned polyacetylene. I. Synthesis and characterization of poly(4′‐ethynylbenzo‐15‐crown‐5)
Authors: Kakuchi Toyoji , Matsunami Shigeyuki , Kamimura Hiroyuki , Ishii Fumiaki , Uesaka Takahiro , Yokota Kazuaki 
Published: April 2003

Abstract4′‐Ethynylbenzo‐15‐crown‐5 (EB15C5) polymerized with high yields in the presence of (bicyclo[2.2.1] hepta‐2,5‐diene) rhodium(I) chloride dimer and triethylamine as a cocatalyst in chloroform at 30°C. Common catalysts for the polymerization of substituted acetylenes, WCl6 and MoCl5, did not produce any polymer from EB15C5. The structure of the main chain for poly(4′‐ethynylbenzo‐15‐crown‐5) (PEB15C5) was determined to be predomi‐nantly cis form, based upon the relatively sharp signals attributed to the main chain atoms that was observed in the 1H and 13C NMR spectra. The cation‐binding properties of PEB15C5 are very similar to that of poly(4′‐vinylbenzo‐15‐crown‐5), and the selectivity is in the order of K+> Rb+ ≫ Cs+ ⋙ Na+, Li+. The electrical conductivity of PEB15C5 increased from 1.3 × 10−10 to 1.3 × 10−6 S. cm−1, when the polymer was doped with iodine. © 1995 John Wiley & Sons, Inc.
Complex‐radical terpolymerization of allylglycidyl ether, maleic anhydride, and methyl methacrylate: Design of self‐crosslinking macromolecules
Authors: Yürük Hüseyin , Rzaev Zakir M. O. , Akovali Güneri 
Published: April 2003

AbstractRadical copolymerization of donor–acceptor monomers, i.e., allylglycidyl ether (AGE), maleic anhydride (MA) and methyl methacrylate (MMA) are studied, where binary copolymerization of AGE...MA complex with MMA is obtained. Constants of charge transfer complex formation (Kc) and copolymerization (r1 and r2) are determined by 1H‐NMR and Kelen‐Tüdöş methods, respectively. It is found that synthesized film‐forming terpolymers with free epoxy and anhydride groups on side chain of macro‐molecules are being crosslinked easily under the effect of temperature and/or UV‐ir‐radiation. Observed crosslinking effect is proved by the DTA, TGA, and IR spectroscopic analyses. It is shown that complex‐radical terpolymerization is very convenient method for the designing of reactive functional macromolecules of linear structure with self‐crosslinking properties which can serve as a basis for the use in photolithographic applications. © 1995 John Wiley & Sons, Inc.
Preparation and properties of alkylated poly(styrene‐graft‐ethylene oxide)
Authors: Jannasch Patric , Wesslén Bengt 
Published: April 2003

AbstractPoly(styrene‐graft‐ethylene oxide), having alkyl chains (C12 or C18) on the polystyrene main chain or on the poly(ethylene oxide) (PEO) side chains, were synthesized. The main chain was alkylated by first ionizing amide groups in a styrene/acrylamide copolymer with tert‐butoxide, and then using the amide anions as sites for reactions with 1‐bromoalkanes. An excess of amide anions was used in the reaction, and the remaining anions were subsequently utilized as initiator sites for the anionic polymerization of ethylene oxide (EO). Synthesis of poly(styrene‐graft‐ethylene oxide) with alkylated side chains was accomplished by polymerization of EO onto the ionized styrene/acrylamide copolymer, followed by an alkylation of the terminal alkoxide anions with 1‐bromoalkanes. The alkylated graft copolymers were structurally characterized by using elemental analysis, 1H NMR, GPC, and IR spectroscopy. DSC analysis showed that only graft copolymers with PEO contents exceeding about 50 wt % and side chain crystallinities comparable to those of homo‐PEO. Main chain alkylated graft copolymers generally had higher crystalinities, as compared to nonalkylated and side chain alkylated samples. The graft copolymers absorbed water corresponding to one water molecule per EO unit at low PEO contents. The water absorption increased progressively at PEO contents above 30 wt % for main chain alkylated samples and above 50 wt % for non‐alkylated samples. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of 3‐phenylethynyl endcapped matrix resins
Authors: Jayaraman S. , Srinivasan R. , McGrath J. E. 
Published: April 2003

AbstractThe synthesis of 3‐phenylethynylphenol, and its applicability as a high temperature cross‐linking endcap for high Tg polyarylene ethers is described. It was synthesized in high yields and purity using the palladium catalyzed coupling reaction between the protected 3‐bromo or iodo phenol and phenylacetylene. The yield of the reaction was found to be highly dependent on the structure of the halide used, the reaction temperature, and the concentration of phenylacetylene. The use of the protected phenol in the palladium catalyzed reaction was also extended to the high yield synthesis of 3‐ethynylphenol and protected 4‐ethynylphenols. The complete synthesis of 3‐phenylethynylphenol, 3‐ethynylphenol, and protected 4‐ethynylphenol in high yields has been demonstrated and is discussed herein. Three new phenylethynyl functionalized arylene ether matrix resins have been synthesized in high yields and purity by reacting 3‐phenylethynylphenol with 4,4′‐dichlorodiphenyl sulfone, 4,4′‐difluorobenzophenone, and bis(4‐fluorophenyl)phenyl phosphine oxide, via nucleophilic poly(arylene ether) synthesis conditions. These low molecular weight materials undergo thermally induced chain extension/branching to yield an insoluble three‐dimensional network at reaction temperatures of around 380°C. The low molecular weight arylene ethers endcapped with the phenylethynyl group demonstrate excellent flow characteristics and a wide processing window of about 250°C. Crosslinking of the 4,4′‐bis(3‐phenylethynyl phenoxy)diphenyl sulfone system for 30 min at 350°C in air afforded a Tg value of 265°C by differential scanning calorimetry measurements. Trace metal analysis for palladium and copper showed absence of these metals that would otherwise detract from the excellent thermal stability. The synthesis and characterization of these phenylethynyl endcapped arylene ether matrix resins is discussed. © 1995 John Wiley & Sons, Inc.
Poly(ethylene oxide)/poly(2vinylpyridne)/lithium perchlorate blends as solid polymer electrolytes: Composition/property/structure interrelationship
Authors: Li Jean , Pratt Lawrence M. , Khan Ishrat M. 
Published: April 2003

AbstractPoly(ethylene oxide) (MW 600,000)/poly(2vinylpyridine) (MW 200,000)/LiClO4 blends have been prepared by the solution blending process. The ionic conductivities of the blends containing lower weight fractions (15, 17.5, 20 and 22.5%) of poly (2vinylpyridine) initially increases as the salt content is increased, reaches a maximum at an ethylene oxide/Li+ mole ratio of 10 and decreases as the salt content is further increased. Blends, which have higher weight fractions of poly(2vinylpyridine) (25 and 35%) display different electric behavior, i.e., the ionic conductivity continously increased as the salt content is increased to an ethylene oxide/Li+ mole ratio of 2. Thermal, 7Li solidstate NMR and semiempirical MNDO molecular orbital studies indicate that this contrasting behavior may be explained by the structure and ratios of the solvates (mixed solvate or homosolvate) of LiClO4 present in the blends. © 1995 John Wiley & Sons, Inc.
Chain extension of polyesters PET and PBT with N,N′‐bis (glycidyl ester) pyromellitimides. I
Authors: Bikiaris Demetris N. , Karayannidis George P. 
Published: April 2003

AbstractThree N,N′‐bis (glycidyl ester imide) of pyromellitic acid (diepoxides) were prepared and were used as chain extenders for poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). The typical reaction conditions for the coupling of the polyester macromolecules were heating with the chain extender under argon atmosphere above the melting temperature (280°C for PET and 250°C for PBT) for several minutes. The Characterization of the samples, obtained at variable residence times in the reactor, was based on solution viscosity measurements and carboxyl and hydroxyl end‐group determinations. Two of the diepoxides used gave satisfactory results. Starting from a PET having intrinsic viscosity [η] = 0.60 dL/g, and carboxyl content CC = 42 eq/106 g, one could obtain PET with [η] = 1.15 dL/g and CC = 16 eq/106 g within 30 min at 280°C. Analogous results were observed for PBT. The hydroxyl content of polyester in all cases was increased. When the quantity of the chain extender used was higher than that theoretically required for its reaction with all carboxyl end groups of the polyester, this resulted in some gel formation indicative of crosslinking. © 1995 John Wiley & Sons, Inc.
Quantitative nuclear magnetic resonance imaging of liquids in swelling polymers
Authors: Hyde Thomas M. , Gladden Lynn F. , Mackley Malcolm R. , Gao Ping 
Published: April 2003

AbstractThe variation of nuclear magnetic resonance (NMR) relaxation parameters (T1,T2) within a polymer during swelling, limits the absolute accuracy with which liquid concentration profiles can be obtained using NMR imaging. In this article a study of the diffusion of decalin into ultra‐high molecular weight polyethylene (UHMWPE) is reported. The study illustrates the use of a method of analysis whereby quantitative solvent profiles can be obtained from data influenced by bothT1andT2contrast effects. AT1andT2map are obtained at a point in the uptake of liquid where the greatest range in liquid concentration is obtained at a point in the uptake of liquid where the greatest range in liquid concentration is observed. The intensity of signal corresponding to liquid in the polymer is compared to that of pure liquid in a reference sample, and correlations forT1andT2values versus signal intensity are used to deconvolve relaxation contrast, to yield the true liquid concentration. The technique was used to study the effect of degree of crosslinking of UHMWPE on the swelling kinetics and decalin transport within the polymer. A spin‐echo imaging technique was used with a recycle delay approximately equal to the average spin‐lattice relaxation time of the liquid, and an echo time approximately half the average spin‐spin relaxation time. Under these conditions the relaxation contrast was significant, yet the mass uptake data derived from the concentration profiles obtained, using the method of analysis described, agreed well with gravimetric data. © 1995 John Wiley & Sons, Inc.
Role of polycation promoters in the cobalt(II) phthalocyaninetetracarboxylic and ‐octacarboxylic acid‐catalyzed autoxidation of mercaptoethanol
Authors: Schipper Eugène T. W. M. , Heuts Johan P. A. , Pinckaers Ralph P. M. , Piet Pieter , German Anton L. 
Published: April 2003

AbstractThe promoting effects of 2,4‐ionene on the cobalt(II) phthalocyaninetetracarboxylic acid‐[CoPc(COOH)4] and cobalt(II) phthalocyanineoctacarboxylic acid‐[CoPc(COOH)8] cata‐lyzed autoxidation of 2‐mercaptoethanol were studied. Dimerization of the CoPc(COOH)4 catalyst, combined with the disappearance of the catalytically inactive μ‐peroxo complex and the appearance of substrate enrichment in the presence of 2,4‐ionene, results in a 40‐fold enhancement of the oxidation rate as compared with the polymer‐free system. UV‐VIS spectroscopy indicates that CoPc(COOH)8 is incapable of forming μ‐peroxo complexes or 2,4‐ionene‐induced dimeric catalyst species under normal reaction conditions. Thus, it was possible to study exclusively the ionene‐induced effect of substrate enrichment. Addition of 2,4‐ionene to an aqueous CoPc(COOH)8 solution results in an activity enhancement by a factor of 2‐3, which can be ascribed to substrate enrichment. Additionally, using mono‐disperse ionene oligomers showed a molecular weight dependence of 2,4‐ionene on the catalytic activity of CoPc(COOH)8, as was observed for the conventional 2,4‐ionene/cobalt phthalocyaninetetrasodiumsulfonate system. The optimal polycation/catalyst ratios of both systems decrease with increasing chain length of 2,4‐ionene, until a constant value is reached. This leads to the conclusion that the optimal polymer/catalyst ratios are predominantly determined by substrate enrichment. © 1995 John Wiley & Sons, Inc.
Thermotropic liquid crystalline polymers with low thermal transitions. II. Low melting thermotropic liquid crystalline homo‐ and co‐polyesters
Authors: Sacripante Guerino , Ober Cristopher K. , Bluhm Terry , Panettoni Mario , Alexandru Lupu 
Published: April 2003

AbstractThermotropic liquid crystalline (TLC) polymers with low melt transitions are useful for imaging technologies. This is the first report describing thermotropic liquid crystalline copolyesters of low melt transitions comprised of a mesogen with up to three different spacer moieties. We have noted that the smectic mesophase range decreased with increasing amounts of different spacer moieties, without altering the isotropic transition and thereby leading to a broader nematic range. © 1995 John Wiley & Sons, Inc.
The preparation and characterization of poly(urethane–peo‐polar siloxane) complexes as polymer electrolytes
Authors: Hewitt David G. , Jing Lin 
Published: April 2003

AbstractA series of novel poly(urethane‐PEO‐polar siloxane) copolymers and their complexes with LiClO4 were prepared for assessment as polymer electrolytes and characterized by IR, GPC, and DSC, and their ionic conductivity and thermal stability were tested. The incorporation of polar siloxanes into U‐PEO greatly increased conductivity. The highest conductivity was 2.6 × 10−5 S cm−1 at 25°C. The correlation between Tg, conductivity, and the ratio of siloxane to PEO as well as stability of the polymers are discussed. © 1995 John Wiley & Sons, Inc.
Studies on thermotropic liquid crystalline elastomers. I. Synthesis and properties of poly (amide‐ester) elastomers
Authors: Sun Shih‐Jieh , Chang Teh‐Chou 
Published: April 2003

AbstractThree series of novel poly(amide‐ester) (PAE) elastomers were prepared by direct poly‐condensation from terephthalic acid (TPA), polyols (Mn = 1000 or 2000), and various diamines. The structures and thermal properties of the synthesized PAEs were examined by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), differential scanning calo‐rimetry (DSC), thermal optical polarized microscopy, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of kinds and amount of diamines and the molecular weight of polyols on the thermal properties of PAEs were studied. By introducing long flexible spacers (PE‐1000 or PE‐2000) into the polymer main chain, all polymers showed two‐phase morphology under the thermal optical microscopic observation. It was interesting that most of the synthesized polymers exhibited only one melting transition corresponding to the soft segments. The melting transition of hard segments could not be detected due to decomposition of the soft segments. However, a thermotropic liquid crystalline PAE (TLCPAE) prepared from methylhydroquinone and 2‐chloro‐5‐methyl‐phenylenediamine with PE‐1000 could be obtained by lowering the melting transition temperature of the hard segment. © 1995 John Wiley & Sons, Inc.
Polymers of carbonic acid. XIV. High molecular weight poly(trimethylene carbonate) by ring‐opening polymerization with butyltin chlorides as initiators
Authors: Kricheldorf Hans R. , Weegen‐Schulz Bettina 
Published: April 2003

AbstractNumerous BuSnCl, Bu2SnCl, and Bu3SnCl‐initiated polymerizations of cyclo(tri‐methylene carbonate) (TMC) were conducted in bulk. In addition to the initiator, reaction time, temperature, and monomer/initiator (M/I) ratio were varied. Yields above 90% were obtained with all three initiators, but their reactivities decrease in the order BuSnCl3 > Bu2SnCl2 > Bu3SnCl. The maximum molecular weights decrease in the same order. With BuSnCl3 Mws up to 250,000 were obtained. These molecular weights were determined by GPC on the basis of the universal calibration method. In this connection Mark‐Houwink equations for two solvents, tetrahydrofuran (THF) and CH2Cl2 were determined and compared with literature data. Furthermore, mechanistic aspects were studied. 1H‐ and 13C‐ NMR spectra revealed that BuSnCl3 forms complexes with the CO‐group of TMC, whereas Bu2SnCl3 do not cause NMR spectroscopic effects. Kinetic studies in chloroform and nitrobenzene and a comparison with Bu3SnOMe suggest that at least BuSnCl3 initiates a cationic mechanism. However, in contrast to SnCl4 (or SnBr4), BuSnCl3 does not cause decarboxylation. Regardless of the initiator 1H‐NMR spectroscopy revealed CH2OH and CH2CI endgroups in all cases. © 1995 John Wiley & Sons, Inc.
Liquid‐Crystalline copolymers and polymer blends containing electron donor and acceptor groups: Effects of mesogenic structures on the smectic phase and the miscibility
Authors: Kosaka Yozo , Uryu Toshiyuki 
Published: April 2003

AbstractSide‐chain liquid‐crystalline copolymers and polymer blends containing an electron‐donating (carbazolylmethylene)aniline group and electron‐accepting nitrophenyl groups with various central linking groups between aromatic groups in the mesogenic units, i.e., NCH, CHCH, NN, and COO, were prepared to examine effects of the mesogenic structure on thermal behaviours. The most remarkable effects of the central linking group on the thermal properties and the miscibility were observed for the polymer blends. The 1:1 miscible polymer blends were prepared from the electron‐donating polymer containing (carbazolylmethylene)aniline group (PM6Cz) and the electron‐accepting polymers with similar central linking groups, i.e., NCH, CHCH, and NN. For example, the 1: 1 polymer blend of PM6Cz and the electron‐accepting polymer containing the nitrostilbene group induced a smectic phase from 73 to 207°C. This isotropic temperature was 46°C higher than the calculated value (161°C) based on the composition without the electron donor‐acceptor interaction. On the other hand, the 1: 1 polymer blend of PM6Cz and the electron‐accepting polymer containing the nitrophenylbenzoate group showed phase separation. Thus, the remarkable thermal stability and the miscibility of the polymer blends containing the electron donor and acceptor groups might be caused by planar structures between the mesogenic side groups which have similar central linking groups through the electron donor‐acceptor interaction. A similar tendency was seen for copolymers and binary mixtures of both low‐molecular‐weight compounds containing the same mesogenic groups. © 1995 John Wiley & Sons, Inc.
Preparation and control of surface properties of monodisperse micrometer size beads by dispersion copolymerization of styrene and butyl methacrylate in polar media
Authors: Horák Daniel , Švec FrantiŠek , Fréchet Jean M. J. 
Published: April 2003

AbstractThe dispersion copolymerization of styrene and butyl methacrylate in ethanol‐water medium to afford micrometer‐size monodisperse beads has been investigated. Hydroxypropyl cel‐lulose, poly (acrylic acid), and poly (vinylpyrrolidone) have been used as steric stabilizers, benzoyl peroxide and azobisisobutyronitrile as initiators. A novel steric stabilizing system consisting of a mixture of poly (acrylic acid) and hydroxypropyl cellulose has also been shown to lead to monodisperse beads for which the surface charge can be controlled by the relative ratio of steric stabilizers. The effect of several variables, such as the solvency of the medium, the concentration of co‐monomers, the reaction temperature, and the type of steric stabilizer and initiator used on the bead size and size distribution are discussed. © 1995 John Wiley & Sons, Inc.
Synthesis of a novel optically active nylon‐1 polymer: Anionic polymerization of L‐leucine methyl ester isocyanate
Authors: Sanda Fumio , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractSynthesis and anionic polymerization of the isocyanate of L‐leucine methyl ester (LeuMI) were carried out. LeuMI was prepared by the reaction of L‐leucine methyl ester hydrochloride with phosgene. Anionic polymerization of LeuMI was carried out at –50°C in dimethyl‐formamide (DMF) using sodium methoxide, potassium tert‐butoxide, methyllithium, or sodium cyanide under a nitrogen atmosphere. The obtained polymers were insoluble in common organic solvents such as DMF, tetrahydrofuran, chloroform, and dimethyl sulfoxide, but were soluble in trifluoroacetic acid. Further, anionic copolymerization of LeuMI with n‐butyl isocyanate (BI) was also carried out to observe that the smaller the content of LeuMI unit in the copolymer was, the larger the specific rotation of the polymer. From the circular dichroic spectral analyses of the polymers it was confirmed that the capability of helix formation of poly (LeuMI) was smaller than poly(BI). The relaxation of the helical structure of the polymer in trifluoroacetic acid solution was observed, and the smaller the content of LeuMI unit in the copolymer was, the faster the relaxation of the helical structure. © 1995 John Wiley & Sons, Inc.