bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermotropic liquid crystalline polymer. III. Synthesis and properties of poly(amide‐azomethine‐ester)
Authors: Li Chien‐Hui , Chang Teh‐Chou 
Published: April 2003

AbstractA series of novel dialdehydes as new monomers, 4,4′‐diformyl‐α,ω‐diphencarbonylalkane, 4,4′‐diformyl‐3,3′‐methoxy‐α,ω‐diphencarbonylalkane, and 4,4′‐diformyl‐3,3′‐ethoxy‐α,ω‐diphencarbonylalkane, was prepared from aliphatic diacid chloride with p‐hydroxybenzaldehyde, vanillin, and 3‐ethoxy‐4‐hydroxybenzaldehyde, respectively. A series of poly(amide‐azomethine‐ester)s was prepared by condensation of 4,4′‐diaminoanilide with 4,4′‐diformyl‐α,ω‐α,ω‐diphencarbonylalkane, 4,4′‐diformyl‐3,3′‐methoxy‐α,ω‐diphencarbonylalkane, and 4,4′‐diformyl‐3,3′‐ethoxy‐α,ω‐diphencarbonylalkane, respectively. Their thermotropic liquid crystalline properties were examined by DSC microscope observations. In most cases, the mesophase extends up to ca. 288–380°C, where thermal decomposition prevents further observation.
Investigation of the formation of poly(ethylene terephthalate) with model molecules. IV. Catalysis of the esterification of ethylene glycol with benzoic acid and of the condensation of ethylene glycol monobenzoate
Authors: Otton Jean , Ratton Serge 
Published: April 2003

AbstractThe esterfication of ethylene glycol (EG) with benzoic acid (BA) is an acid‐catalyzed reaction which leads, as a first intermediate, to ethylene glycol monobenzoate (EGMB). This compound has an OH group which is more active towards carboxylic groups than the first OH group of EG. Moreover, it is a key intermediate in the formation of sideproducts containing diethylene glycol (DEG) moieties. The condensation reaction of EGMB was particularly studied in the presence of carboxylic acids or metal derivatives as catalysts. Titanium is the most active. Sb, which is widely used in the industrial synthesis of PET, needs to be present at a high level of concentration to show an activity. The presence of carboxylic groups in the reaction medium does not affect its activity, but it is necessary to remove the ethylene glycol as soon as it is formed in order to keep it active during the condensation reaction.
Polyisobutylene‐containing block polymers by sequential monomer addition. II. Polystyrene–polyisobutylene–polystyrene triblock polymers: Synthesis, characterization, and physical properties
Authors: Kaszas G. , Puskas J. E. , Kennedy J. P. , Hager W. G. 
Published: April 2003

AbstractNew linear and three‐arm star thermoplastic elastomers (TPEs) comprising a rubbery polysobutylene (PIB) midblock flanked by glass polystyrene (PSt) blocks have been synthesized by living carbocationic polymerization in the presence of select additives by sequential monomer addition. First, isobutylene (IB) was polymerized by bi‐ and trifunctional tert‐ether (dicumyl‐ and tricumyl methoxy) initiators in conjunction with TiCl4 conintiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at −80°C. After the living, narrow molecular weight, distribution PIB (M̄w/M̄n = 1.1‐1.2) has reached the desired molecular weight, styrene (St) together with an electron pair donor (ED) and a proton trap (di‐tert‐butylpyridine, DtBP) were added to block PSt from the living chain ends. Uncontrolled initiation by protic impurities that produces PSt contamination is prevented by the use of DtBP. PSt‐PIB‐PSt blocks obtained in the absence of additives are contaminated by homopolymer and /or diblocks due to inefficient blocking and initiation by protic impurities, and exhibit poor physical properties. In contrast in the presence of the strong ED N,N‐dimethylacetamide (DMA) and DtBP the blocking of St from living PIB chain occurs efficiently and block copolymers exhibiting good mechanical properties can be prepared. Virgin TPEs can be repeatedly compression molded without deterioration of physical properties. The products exhibit a low and a high temperature Tg characteristic of phase separated PIB and PSt domains. Transmission electron microscopy of linear triblocks containing ∼ 34 wt % PSt also indicates microphase separation and suggests PSt rods dispersed in a PIB matrix.
Preparation of polymide‐imides by direct polycondensation with triphenyl phosphite. V. Aliphatic‐aromatic polyamide‐imides based on N,N′‐bis(ω‐carboxyalkyl) benzophenone‐3,3′,4,4′‐tetracarboxylic diimides
Authors: Hsiao Sheng‐Huel , Yang Chin‐Ping 
Published: April 2003

AbstractFive diimide‐dicarboxylic acids were prepared from benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride and glycine, β‐analine, 4‐aminobutyric acid, 6‐aminocaproic acid, and 11‐aminoundecanoic acid. New aromatic‐aliphatic polyamide‐imides were prepared by the direct polycondensation of these diacids with aromatic diamines using triphenyl phosphite in N‐methyl‐2‐pyrrolidone (NMP)–Pyridine solution in the presence of calcium chloride. The resulting polymers were characterized by inherent viscosity, infrared spectra, elemental analyses, solubility, differential scanning calorimetry (DSC), thermogravimetry, and wideangle x‐ray diffraction measurements.
Synthesis and characterization of random poly(amide‐sulfonamide)s. II. Polymers from unsymmetrical diamine monomers
Authors: Adduci Jerry M. , Rochanapruk Theverak 
Published: April 2003

AbstractNovel poly(amide‐sulfonamide)s have been prepared by reacting terephthalic, isophthalic, and sebacic acid and their acid chlorides with variously substituted diamines containing preformed sulfonamide linkages utilizing solution polymerization techniques. Inherent viscosities of the prepared polymers varied from 0.22 to 1.21 dL/g. Those having inherent viscosities greater than 0.4 dL/g formed clear, tough, flexible films. Glass transition temperatures ranged from 87 to 273°C. Thermogravimetric analyses of the polymers showed moderate thermal stability.
Mechanistic study on mechanochemical polymerization of acrylamide
Authors: Kuzuya Masayuki , Kondo Shin‐Ichi , Noguchi Akihiro , Noda Nahoko 
Published: April 2003

AbstractThe ESR study of the radicals formed in mechanochemical polymerization of acrylamide (AAM) was undertaken. The nature of the radical formation was compared with the mechano‐radical formation produced by mechanical fracture of polyacrylamide (PAAM). The structure of radicals formed were all identified to be an end‐chain radical, equivalent to a polymer‐chain propagating radical. The computer simulation disclosed that the observed spectra of the propagating radical can be approximated essentially by two kinds of component spectra, a large amount of triplet, and a small amount of quarter (a triplet of doublets). Thus, the existence of two major conformers in a single end‐chain radical has been proposed. The ESR kinetics of the radical formation were further studied and its correlation with the nature of polymerization (the changes in molecular weight and polymer conversion) was discussed.
Polymer precursor synthesis of alumina fibers
Authors: Chien James C. W. , Yang Yingsong , Martinez J. R. , Dong Sizhong , Telluri Venkatesh , Jakus Karl 
Published: April 2003

AbstractHigh strength alumina fibers were fabricated with a polymer precursor process which was monitored with 13C‐NMR, elemental analysis, gas evolution, SEM, and X‐ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i‐propanoyl groups in molar ratios of 0.2 : 0.8 to 0.4 : 0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320–350°C, and then calcined at 950°C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.
High activity magnesium chloride supported catalysts for olefin polymerization. XXIX. Molecular basis of hydrogen activation of magnesium chloride supported Ziegler–Natta catalysts
Authors: Chien James C. W. , Nozaki Takashi 
Published: April 2003

AbstractHydrogen (pH2 = 72 torr) increases the rate of propylene polymerization by a MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4‐AlEt3/methyl‐p‐toluate catalyst (CW‐catalyst) by two‐to three‐fold which corresponds closely with the increase in the number of active sites as counted by radiolabeling with tritiated methanol. The oxidation states of titanium in decene polymerizations by the CW‐catalyst were determined as a function of time of polymerization (tp). In the absence of H2, all [Ti+n] for n = 2, 3, 4 remain constant during a batch polymerization. In the presence of H2 and within 5 min of tp, [Ti+2] decreases by an amount, corresponding to 15% of the total titanium and [Ti+3] increases by the same amount, while [Ti+4] is not changed. Therefore, three‐fourths of the H2 activation result from oxidative addition processes. The remaining one‐fourth of the H2 activation may be attributed to the activation of previously deactivated Ti+3 ions by hydrogenolysis. Monomer converts some of the EPR silent Ti+3 sites to EPR observable species resulting in their activation.
A multitechnique surface analytical study of a segmented block copolymer poly(ether‐urethane) modified through an H2O radio frequency glow discharge
Authors: Vargo Terrence G. , Hook Daniel J. , Gardella Joseph A. , Eberhardt Mary A. , Meyer Anne E. , Baier Robert E. 
Published: April 2003

AbstractRecent work in our laboratories has fully characterized the surface region of a segmented poly(ether‐urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi‐analytical‐technique approach is used to elucidate changes in these PEU surfaces induced through an H2O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi‐permanent over a time period of 6 months.
Catalytic epoxidation of polyisobutylene‐co‐isoprene with hydrogen peroxide
Authors: Jian Xigao , Hay Allan S. 
Published: April 2003

AbstractPolyisobutylene‐co‐isoprene (PIBI) can be epoxidized with hydrogen peroxide in the presence of methyltrioctylammonium tetrakis (diperoxotungsto) phosphate(3‐) as the catalyst in a biphasic system. The effects of the reaction time and temperature, the ratio of the organic phase to the aqueous phase, the concentration of the catalyst and polymer and stirring intensity, respectively, are studied on the conversion of double bonds to oxirane groups. 1H‐NMR analysis confirms the absence of ring opening side reactions in this epoxidation reaction system. The kinetics of the reaction are discussed. The rate constants are measured at four temperatures and the activation energy for the reaction is determined as 54.2kJ/mol. The optimum reaction temperature is about 60°C.
Polyepichlorohydrin diols free of cyclics: Synthesis and characterization
Authors: Biedron Tadeusz , Kubisa Przemyslaw , Penczek Stanislaw 
Published: April 2003

AbstractPolymerization of epichlorohydrin (ECH) in the presence of diols, catalyzed by Lewis or protic acids, proceeds by activated monomer mechanism (AMM), i.e., by subsequent additions of protonated monomer molecules to the terminal hydroxyl groups of the growing chain. As opposed to the typical active chain end mechanism, side reactions, including cyclization, are strongly suppressed in the polymerization by AMM and well‐defined linear product are obtained. It follows from kinetic considerations, that in order to achieve the high contribution of AMM, the reaction should be carried out at low instantaneous concentration of monomer, and this can be accomplished by slowly adding ECH to the reaction mixture. Using this approach, polyepichlorophydrin diols have been prepared in the M̄n ∼ 2500 products with DPn = [M]0/[I]0 can be obtained practically free of cyclic by‐products with the yields approaching quantitative. Polyepichlorohydrin diols obtained by AM polymerization are strictly bifunctional, regular head‐to‐tail polymers containing mainly (≥ 95%) secondary hydroxyl and groups.
Chemical modification of polymers: Catalytic hydroformylation and hydroxymethylation of styrene–butadiene copolymers
Authors: Sibtain F. , Rempel G. L. 
Published: April 2003

AbstractStyrene‐butadiene (SB) copolymers can be readily hydroformylated to various degrees of conversion under mild conditions with HRh(CO) (PHh3)3 as the catalyst. Utilization of a novel automated gas consumption apparatus allows fairly reliable control of the degree of formyl loading and the preparation of infrared calibration curves for various SB‐copolymers. In a subsequent reaction, also under homogeneous conditions, the hydroformylated SB‐copolymers can be hydrogenated with HRuCI (CO) (PPh3)3 to give overall hydroxymethylated polymers. The transformations were characterized by infrared, 13C‐, and 1H‐NMR spectroscopy.
Synthesis of poly(dimethylsiloxane) oligomers with pendant amine groups via co‐equilibration anionic polymerization reactions
Authors: Spinu M. , McGrath J. E. 
Published: April 2003

AbstractThe present study describes a method of incorporating amine functional groups on poly(dimethylsiloxane) chains as pendant groups on silicon atoms. This method allows for independent control of the molecular weight and the amine content of the oligomer. The new molecular design was achieved by co‐equilibration of the cyclic tetramer octamethylcyclotetrasiloxane (D4) with a new cyclic siloxane monomer containing aliphatic amine substituents on the silicon atoms. The co‐equilibration of the two cyclic siloxanes was carried out in the presence of a silanolate catalyst, using the nonfunctionalized hexamethyldisiloxane as the end‐capper. The distribution of the molecular species at thermodynamic equilibrium and the efficiency of incorporation of siloxane units containing pendant amine functionalities into the poly(dimethylsiloxane) chains were investigated as a function of oligomer chemical composition and molecular weight.
Photochemical property of the polymer‐bearing pendant norbornadiene moiety and storage stability of the resulting quadricyclane group in the polymer
Authors: Nishikubo Tadatomi , Hijikata Chikara , Iizawa Takashi 
Published: April 2003

AbstractA polymer bearing pendant norbornadiene (NBD) moieties and a low molecular weight model compound ([2‐carbobenzyloxy‐3‐phenyl‐2,5‐norbornadiene CBPNB)], were synthesized by substitution reaction of poly(p‐chloromethylstyrene) and benzyl chloride, respectively, with the potassium salt of 3‐phenyl‐2,5‐norbornadiene‐2‐carboxylic acid. Photochemical valence isomerization and storage stabilities of the resulting polymer having corresponding pendant quadricyclane (QC) groups and the low molecular weight QC compound were investigated in dichloromethane solution. It was found that the rate of photochemical valence isomerization of the pendant NBD moiety in the polymer was the same as or slightly higher than that of CBPNB, and the storage stability of the QC group in the polymer was higher than that of the QC compound resulting from CBPNB in the solution. The photochemical reaction of the pendant NBD moiety within the polymer without catalyst proceeded quantitatively in the film state. However, the photochemical reaction of the polymer films blended with 5,10,15,20‐tetraphenyl‐21H,23H‐porphine cobalt (II) catalyst (Co‐TPP) did not proceed quantitatively, and the degree of conversion of the pendant NBD moiety in the polymer decreased with increasing amounts of Co‐TPP in the film. The QC group produced in the polymer by photo‐irradiation had excellent storage stability in the film state without Co‐TPP. On the other hand, the QC group in the polymer films blended with Co‐TPP Catalyst reverted gradually to the NBD group at room temperature.
Photooxidation of ABS of long‐wavelengths
Authors: Jouan Xavier , Gardette Jean‐Luc 
Published: April 2003

AbstractThe evolution of the photochemical degradation of ABS has been studied in conditions of long wavelength irradiation (λ's> 300 nm). The main photoproducts involved in the oxidative evolution have been identified by using FTIR spectroscopy and chemical titrations. A particular attention has been devoted to α–β unsaturated ketones that appear as secondary photoproducts. Those ketones present a low photochemical stability when exposed in the range 300–400 nm. Conditions for their formation have been experimentally studied. Formation of oxidation photoproducts has been also studied at the macroscopic level and it has been shown that their repartition in the polymer is heterogeneous. The origins of the heterogenities have been studied.
A microcomputer program for estimation of copolymerization reactivity ratios
Authors: Dube M. , Sanayei R. Amin , Penlidis A. , O'Driscoll K. F. , Reilly P. M. 
Published: April 2003

AbstractA user‐friendly program has been developed to estimate copolymerization reactivity ratios based on a nonlinear minimization algorithm. The use of an optimal experimental design for copolymerization when the Mayo–Lewis model applies is presented. The applicability of the program is demonstrated using actual and simulated experimental data.
Photodegradation of UV‐cured coatings II. Polyurethane–acrylate networks
Authors: Decker C. , Moussa K. , Bendaikha T. 
Published: April 2003

AbstractHighly crosslinked aliphatic and aromatic polyurethane‐acrylate (PUA) coatings have been obtained by photopolymerization of multifunctional monomers. The discoloration and chemical modifications occurring upon accelerated QUV aging were monitored by UV and IR spectroscopy. The polymers were found to undergo photooxidation and loss of carbamate and phenyl groups, with lower quantum yields (10−3 mol photon−1) than in related linear polymers. Hydroxy‐phenyl benzotriazole UV‐absorbers have a limited effect on the degradation rate, at the concentration used (0.5%). Hindered amines (HALS) are substantially more effective, especially in aliphatic PUA. A 20‐fold increase in the stabilization efficiency was found with the UVA + HALS combination. Aromatic PUA are more difficult to stabilize, because of the strong absorption and photolysis of the phenyl group which yields colored products. Radical‐induced oxidation is predominant in aliphatic PUA and develops with long kinetic chains, while in aromatic PUA it competes with direct photolysis.
A comparative study on the structural changes in leucoemeraldine and emeraldine base upon doping by perchlorate
Authors: Neoh K. G. , Kang E. T. , Tan K. L. 
Published: April 2003

AbstractThe changes in the structure of leucoemeraldine (LM) and emeraldine (EM) base upon doping by perchlorate anions are studied by X‐ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy. In the case of LM, interactions of the amine nitrogens with the perchlorate anions result in a nitrogenonium ion structure analogous to that arising from the protonation of imine nitrogens in EM by HCl except the chloride anion in the latter has been replaced by the perchlorate anion. A small amount of partially ionic and covalent chlorine is also incorporated in the LM–perchlorate complexes. The maximum electrical conductivity that is achieved in these complexes is about 4 S/cm. In contrast, the maximum conductivity of the EM–perchlorate complexes is three orders of magnitude lower. The interactions of perchlorate anions with EM base result in the preferential disappearance of the imine units over the amine units.
Synthesis of aromatic polythers by Scholl reaction. IV. Homopolymerization and copolymerization of α,ω‐bis[4‐(1‐napthoxy)phenylsulfonyl]perfluoroalkanes
Authors: Percec Virgil , Wang James H. , Oishi Yoshi , Feiring Andrew E. 
Published: April 2003

AbstractPolyether sulfones containing perfluoroalkyl segments were prepared by room temperature radical‐cation polymerization (Scholl reaction) of 1,4‐bis[4‐(1‐napthoxy)phenylsulfonyl]perfluorobutane (1a) and 1,8‐bis [4‐(1‐napthoxy) phenylsulfonyl] perfluoroctane (1b) in nitrobenzene, using anhydrous ferric chloride as oxident. The homopolymerization of 1a and of 1b performed under various polymerization conditions, resulted in polymers with number average molecular weight (M̄n) up to 33,000 and 38,000 g/mol, respectively. Copolymerization of the fluorinated monomers 1a with 1b, and either 1a or 1b with 4,4′‐bis(1‐naphthoxy) diphenyl sulfone (4) and 1,5‐bis (1‐naphthoxy) pentane (5) produced copolymers of M̄n up to 18,100 g/mol. The reactivity of the various monomers was discussed on the basis of the induction and resonance stabilization effects.
Liquid crystalline properties of a series of thermotropic copolyesters containing both mesogenic and nonmesogenic units
Authors: Reddy C. Rami , Lenz Robert W. 
Published: April 2003

AbstractA series of copolymers containing triad ester mesogenic units, with pendent n‐octyl substituents, and triad ester nonmesogenic units, both with flexible spacer groups, was prepared and characterized for the effect of the nonmesogenic unit content on transition temperatures and thermodynamic parameters. The mesophase temperature range increased, but temperature, enthalpy, and entropy of isotropization decreased in a linear manner with increasing nonmesogen comonomer content. The entropy of isotropization is considered to be a quantitative measure of the degree of order of the nematic phase, but this order may include both the amount and the order parameter of the mesophase if, as proposed, both the isotropic and nematic phase exist below the isotropization temperatures of the copolymers.
Styrene–isoprene block copolymers. I. Synthesis and solution properties
Authors: Velichkova R. , Toncheva V. , Getova C. , Pavlova S. , Dubrovina L. , Gladkova E. , Ponomareva M. 
Published: April 2003

AbstractCopolymers with a different degree of distribution of styrene and isoprene blocks are prepared by anionic polymerization. The products are characterized by means of 1H‐NMR spectroscopy, GPC, viscometry, and light scattering. The results show that the copolymers are homogeneous in molecular weight and chain composition. In the investigated selective solvents, cyclohexane and base lubricating oil, and equilibrium exists between micelle aggregates and individual polymer coils. The influence of the copolymer structure on the micellization is more pronounced in cyclohexane.