bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of urethane‐modified polyimides
Authors: Sendijarević Ais̆a , Sendijarević Vahid , Frisch Kurt C. , Koruga‐Lazarević Branka , Torlić Enes 
Published: April 2003

AbstractThe synthesis and properties of thermoplastic urethane‐modified polyimides, based on different isocyanates, with different concentrations of hard segments and different ratios of imide and urethane groups, were studied. The effect of catalysts, isocyanates, and temperature was investigated on model reactions leading to formation of monoimides, bisimides, and polyimides. A polymer based on 2,4‐TDI, poly(oxytetramethylene) glycol of 1000 molecular weight and pyromellitic dianhydride, with 75% of imide in the hard segments, retained about 50% of the original tensile strength at 120°C and about 30% at 150°C. Increasing the temperature up to 150°C had very little effect on the elongation of this copolymer. In general, increasing the imide concentration in the polymer structure provided better retention of stress‐strain properties at elevated temperatures.
Synthesis and characterization of novel 1,3,4‐oxadiazole‐ or 1,3,4‐thiadiazole‐containing wholly conjugated polyazomethines
Authors: Saegusa Yasuo , Sekiba Kazuhiro , Nakamura Shigeo 
Published: April 2003

AbstractA series of thermally stable and semiconducting polyazomethines containing 1,3,4‐oxadiazole or 1,3,4‐thiadiazole ring in the polymer backbone were synthesized by the simple solution poly‐condensation of dialdehydes with the preformed nuclei with aromatic diamines under mild conditions. To elucidate the structure and also structure‐property relationships of the polymers, model compounds were prepared under the same reaction conditions. These polyazomethines having a wholly conjugated system were yellow powders and had reduced viscosities up to 0.38 dL/g in concentrated sulfuric acid and electric conductivity as high as 10−11 S cm−1 at room temperature. Thermogravimetry showed that all the polymers were heat resistant up to around 400°C, in both air and nitrogen atmospheres. Their completely black colored charge‐transfer complexes were prepared by iodine‐doping of the polymers. The room temperature conductivity of the polymers was found to be markedly increased up to the orders of 10−6–10−7 S cm−1 upon doping. The highest value attained was 4.8 x 10−6 S cm−1. Comparison of electronic spectra of the polymers with those of the model compounds indicated the π‐electrons in the polymers are extensively delocalized along the polymer main chain.
Synthesis and incorporation of 4‐triethoxysilyl‐1,2‐bis(diphenylphosphino)benzene into silica gel and solgel polymers: Preparation and utilization of recyclable catalysts for alkene hydroformylation and methanol homologation
Authors: Hardee J. R. , Tunney S. E. , Frye James , Stille J. K. 
Published: April 2003

AbstractA chelating phosphine monomer, 4‐triethoxysilyl‐1,2‐bis(diphenylphosphino)benzene (9), was prepared in three steps from 2,4‐dibromoiodobenzene. Attachment of 9 to the surface of commercial silica gel, followed by chelation of rhodium, gave a catalyst which showed both undiminished activity (turnover rates of 90 atom−1 h−1) and no loss of rhodium over five recycles in the hydroformylation of styrene. Complexation of cobalt afforded a catalyst for the homologation of methanol. Monomer 9 could be incorporated into a solgel polymer produced from silicic acid in tetrahydrofuran, but low rhodium uptake and low catalytic activity suggested that few phosphine sites were available to the rhodium. The catalytically‐active species were modeled by the synthesis of cobalt and rhodium complexes containing 1,2‐bis(diphenylphosphino)benzene.
Synthesis of hydrogen‐terminated aliphatic bis(ethynyl ketone)s and aliphatic poly(enamine‐ketone)s and poly(enonesulfide)s
Authors: Wilbur J. M. , Bonner B. A. 
Published: April 2003

AbstractHydrogen‐terminated aliphatic bis(ethynyl ketone)s (H‐ABEKs): 1,9‐decadiyne‐3,8‐dione (3a) and 1,13‐tetradecadiyne‐3,12‐dione (3b) were prepared by the Friedel‐Crafts reaction of bis(trimethylsilyl) acetylene (BTMSA) with adipoyl chloride and sebacoyl chloride, followed by desilylation with an aqueous buffer solution. Aliphatic poly(enamine‐ketone)s (APEKs) and aliphatic poly(enonesulfide)s (APESs) were prepared in nearly quantitative yield by the nucleophilic addition polymerization of 3a,b with various diamines and dithiols in N,N‐dimethylformamide (DMF) and m‐cresol at room temperature during 14‐22 h. Aromatic diamines and dithiols gave polymers that were soluble only in m‐cresol. Primary diamines gave exclusively APEKs with the cis (Z) configuration. Dithiols gave APESs which contained more cis (Z) than trans (E) configurations. The inherent viscosities (ηinh) of the APEKs ranged from 0.05 to 0.73 dL/g. The APESs gave ηinh ranging from 0.36 to 2.21 dL/g.
Syntheses and properties of halato‐telechelic polyurethane‐ureas from divalent metal salts of p‐aminobenzoic acid, diamine, dialkylene glycols, and diisocyanate
Authors: Matsuda Hideaki , Takechi Shigetoshi 
Published: April 2003

AbstractHalato‐telechelic polyurethane‐ureas were synthesized from divalent metal salts of p‐aminobenzoic acid, 4,4′‐diaminodiphenylmethane (4,4′‐methylenedianiline, MDA), dialkylene glycols, and 2,4‐toluylene diisocyanate (TDI). As the divalent metal, Mg and Ca were used, and diethylene glycol and dipropylene glycol were the glycols used. The halatotelechelic polyurethane‐ureas obtained showed better solubilities in dimethylformamide (DMF) and dimethylsulfoxide (DMSO) than previously reported halato‐telechelic polyureas from the metal salts, MDA, and TDI. The reduced viscosities of the polyurethane‐ureas in DMF and DMSO were very low at very low concentrations but increased as the concentration increased. The increase was higher in DMF having lower dielectric constant, due to lower depression of ionic association. Introducing the metal into the urethane‐urea backbone resulted in a considerable decrease in decomposition temperature. In dynamic mechanical property measurements, they exhibited no sharp decrease in relative shear modulus and no peak of tan δ, probably due to aggregation of ionic groups in the polymer main chain.
Semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate
Authors: Urquiola Belen , Arzamendi Gurutze , Leiza José R. , Zamora Aranzazu , Asua José M. , Delgado Joaquín , El‐Aasser Mohamed S. , Vanderhoff John W. 
Published: April 2003

AbstractThe semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate was investigated. The effect of type of process (starved process versus semi‐starved process), type of feed (neat monomer addition versus monomer emulsion addition), amount of seed initially charged in the reactor, and feed rate on the time evolution of the overall conversion, copolymer composition, and polymer particle size was analyzed. It was found that, in the case of the starved process, both monomers, but mainly vinyl acetate, accumulated in the reactor. The preferential accumulation of vinyle acetate resulted in a drift of the copolymer composition. Both monomers accumulation and copolymer composition drift were reduced by increasing the amount of seed initially charged in the reactor and by decreasing the feed rate. For the semi‐starved process, it was found that a vinyl aceatate rich copolymer was formed when a low methyl acrylate feed was used, whereas a methyl acrylate rich copolymer was obtained at high methyl acrylate feed rates. For both starved process and semi‐starved process, the total number of polymer particles, after an initial increase, reached a plateau value which was the same in all of the experiments carried out. These results were analyzed by means of a mathematical model developed for this system.
Polymerization of 1‐methylthio‐1‐alkynes and polymer properties
Authors: Matsumoto Tatsuhiko , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractPolymerization of 1‐methylthio‐1‐alkynes (MeSCCR; R = Et, n‐Bu, n‐C6H13, and n‐C8H17) was studied by use of transition metal catalysts. A 1 : 2 mixture of MoCl5 and Ph3SiH provided polymers having M̄w over 1 × 105 in 30–50% yields from these monomers. The length of the alkyl group hardly affected the polymerization. The monomer, MeSCC‐n‐C6H13, showed low reactivity in homopolymerization, but higher reactivity than that of MeCC‐n‐C5H11 in copolymerization. Poly(1‐methylthio‐1‐alkyne)s were colorless solids, and those with long alkyl pendants (R = n‐C6H13, n‐C8H17) were soluble in various organic solvents. The present polymers were thermally more stable than poly(2‐alkyne)s, the corresponding hydrocarbon polymers.
The effect of polymer structure on the efficiency of acid generation from triarylsulfonium salts
Authors: McKean Dennis R. , Schaedeli Ulrich P. , Kasai Paul H. , Macdonald Scott A. 
Published: April 2003

AbstractThe irradiation of triarylsulfonium salts produces Brönsted acid along with diarylsulfide products. This photochemical conversion has been applied in several areas of polymer film technology including imaging and curing of films. This paper discusses the dependency of acid generation in polymer films on the structures of both polymer and sulfonium salt. The results suggest that the structures of both polymer and sulfonium salt. The results suggest that the efficiency of acid generation is dependent on the interaction between polymer structure and the charged sulfonium salt. Studies have been carried out for both deep‐UV and electron beam irradiation of polymer films. The variation of acid generation with sulfonium salt loading has been determined. Finally the effect of accelerating voltage on the amount of acid generation following electron beam irradiation is discussed. ESR spectroscopy has been done on films after uv irradiation to determine the nature of the radicals which are formed.
Hydrogen/liquid vapor radio frequency glow discharge plasma oxidation/hydrolysis of expanded poly(tetrafluoroethylene) (ePTFE) and poly(vinylidene fluoride) (PVDF) surfaces
Authors: Vargo Terrence G. , Gardella Joseph A. , Meyer Anne E. , Baier Robert E. 
Published: April 2003

AbstractModification of fluorine‐containing polymers has recently received much attention due to new chemistries allowing for refunctionalization of these materials, especially their surfaces. In this article results are discussed which demonstrate various interesting modifications (including incorporations of OH and oxygen comprised functionality) to expanded poly(tetrafluoroethylene) (ePTFE) surfaces. This is effected through the use of low damage, radio frequency glow discharge (RFGD) processes. The low damage conditions, which preserve the original pore structure/morphology of these RFGD treated materials, are supported by Scanning Electron Microscopy (SEM) while the resulting atomic and molecular effects are investigated through other surface analytical methodology. All materials reported in this investigation have been subjected to intensive structural analyses utilizing Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR–FTIR), and wettability profiles obtained through contact angle measurements using a large series of liquids having varying surface tensions and surface reactive functionality. Through this multitechnique analysis of both expanded PTFE and poly(vinylidene fluoride) (PVDF) treated surfaces, a model is supported which illustrates surfaces possessing both high and low energy regions comprising both oxygen and fluorine functionality in close molecular proximity.
Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and polyamides from dicarboxylic acid and diisocyanate terminated functionalities
Authors: Otsuki Toshihiro , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractPolydimethylsiloxane (PDMS)–polyamide multiblock copolymers were successfully synthesized via diisocyanate route by two different procedures, i.e., the one‐step and two‐step methods, In the two‐step method, α, ω‐diisocyanate‐terminated polyamide oligomers, which were prepared in situ from a mixture of isophthalic acid (IPA) and azelaic acid (AZA) with 4,4′‐methylenedi (phenyl isocyanate) (MDI) in 1,3‐dimethyl‐2‐imidazolidone (DMI) in the presence of 3‐methyl‐1‐phenyl‐2‐phosopholene 1‐oxide catalyst, were reacted with α, ω‐bis (10‐carboxydecyl) polydimethylsiloxane (PDMS‐diacid) leading to the formation of multiblock copolymers. In the one‐step method, the reaction components, MDI, IPA, AZA, and PDMS‐diacid were reacted all together in DMI in the presence of the catalyst. These polymerizations gave multiblock copolymers having inherent viscosities in the range of 0.36–1.12 dL/g in N,N‐dimethylacetamide (DMAc). These multiblock copolymers were soluble in amide‐type solvents, and transparent (or translucent) and ductile films could be cast from the solutions in a mixture of DMAc and bis(2‐ethoxyethyl) ether. The multiblock copolymers prepared by the two‐step method had better‐defined, microphase‐separated morphology than those obtained by the one‐step method. The mechanical properties of PDMS–polyamide multiblock copolymer films were found to be highly dependent on the PDMS content; the tensile strength and modulus of the films decreased with increasing the PDMS content.
Photochromic and photomechanical ionene elastomer containing poly(tetrahydrofuran) segments and viologen units
Authors: Hashimoto Tamotsu , Kohjiya Shinzo , Yamashita Shinzo , Irie Masahiro 
Published: April 2003

AbstractElastomeric polymer consisting of poly(oxytetramethylene) segments and viologen units (PTV) was synthesized by the reaction of dicationic living poly(tetrahydrofuran) with 4,4′‐bipyridine at −70°C. The chloride or bromide ion was introduced as the counter anion into the viologen groups of PTV by the treatment of the reaction mixture with aqueous sodium chloride or bromide, respectively. The solid film of PTV having chloride inon showed photochromism, i.e., color change by light irradiation, via photoreduction of the violegen groups. In contrast. PTV of bromide counter anion required a small amount of poly(N‐vinyl‐2‐pyrrolidone) to undergo the photochromic reaction. The irradiation of light also affected the stress relaxation of the polymers, namely PTV showed photomechanical behavior. This phenomenon is considered to be induced by the decrease of total number of ionic charges of PTV by photo‐reduction of the viologen groups followed by the change of a state of ionic clustering in the polymer matrix.
Surface grafting of polymers onto inorganic ultrafine particles: Reaction of functional polymers with acid anhydride groups introduced onto inorganic ultrafine particles
Authors: Tsubokawa Norio , Kogure Akira 
Published: April 2003

AbstractThe surface grafting onto inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by the reaction of acid anhydride groups on the surfaces with functional polymers having hydroxyl and amino groups was examined. The introduction of acid anhydride groups onto inorganic ultrafine particle was achieved by the reaction of hydroxyl groups on these surfaces with 4‐trimethoxysilyltetrahydrophthalic anhydride in toluene. The amount of acid anhydride groups introduced onto the surface of ultrafine silica, titanium oxide, and ferrite was determined to be 0.96, 0.47, and 0.31 mmol/g, respectively, by elemental analysis. Functional polymers having terminal hydroxyl or amino groups, such as diol‐type poly(propylene glycol) (PPG), and diamine‐type polydimethylsiloxane (SDA), reacted with acid anhydride groups on these ultrafine particles to give polymer‐grafted ultrafine particles: PPG and SDA were considered to be grafted onto these surfaces with ester and amide bond, respectively. The percentage of grafting increased with increasing acid anhydride group content of the surface: the percentage of grafting of SDA (Mn = 3.9 × 103) onto silica, titanium oxide, and ferrite reaching 64.7, 33.7, and 24.1%, respectively. These polymer‐grafted ultrafine particles gave a stable colloidal dispersion in organic solvents.
Studies of photoinitiation and phototermination of free radical polymerization using dual pulsed laser techniques
Authors: Holdcroft Steven , Guillet James E. 
Published: April 2003

AbstractStudies of free radical polymerization are described in which the initiation and termination events are independently controlled using two laser pulses of different wavelength. Flash photolysis of azobisisobutyronitrile (AIBN) was used to initiate the polymerization of styrene. After a predefined period the polymerization was terminated by laser photolysis of 2‐naphthylmethyl 1‐naphthylacetate (NMNA). The molecular weights of the polymer were controlled by the time interval between laser pulses. Irradiation with high intensity laser pulses in the presence of preformed polystyrene yields a fluorescent‐labelled polymer. A two‐photon process is proposed to explain the mechanism of photoaddition of naphthylmethyl groups to the polymer chain.
Synthesis, polymerization, and thermal properties of a new acetylene‐terminated schiff base
Authors: Wei Yen , Hariharan Ramakrishnan , Ray Jayanta K. 
Published: April 2003

AbstractA new acetylene‐terminated Schiff base monomer, N,N′‐(1,4‐phenylenedimethylidyne)‐bis‐(4‐ethynylaniline) (PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a new polymer (PPPP) with alternating units of aromatic imine and diacetylene via an oxidative coupling polymerization of the acetylenic terminal groups. The monomer was also polymerized by thermal curing at elevated temperatures up to 400°C to afford a crosslinked polymer network without significant structural decomposition. Thermal properties and thermal reactions of the monomer and the polymers were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polymers exhibit excellent thermal stabilities in an inert atmosphere. Electronic properties of the polymers are also discussed.
Biocompatible polymeric systems: Copolymerization of 4‐methacryloyloxy‐acetanilide with 2‐hydroxyethyl‐methacrylate
Authors: Román J. San , Levenfeld B. , Madruga E. L. , Vairon J. P. 
Published: April 2003

AbstractSoluble copolymers of 4‐methacryloyloxy‐acetanilide (M), an acrylic derivative of paracetamol, with 2‐hydroxyethyl‐methacrylate (H) were prepared by free radical polymerization in DMF solution at 50°C, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were determined by the application of conventional linearization methods suggested by Fineman‐Ross and Kelen‐Tudos. The results obtained make clear that this system copolymerizes at random with the reactivity ratios rm = 2.15 ± 0.05 and rH = 0.90 ± 0.10. The microstructure of copolymer chains is described on the basis of the first order Markov statistics. The copolymer glass transition temperatures were determined calorimetrically and the variation of Tg with the copolymer composition is discussed according to modern methods, considering the sequence distribution of monomeric units along the copolymer chains. Also the Tg of the corresponding homopolymers were determined giving the values of Tg(M) = 471 K and Tg(H) = 358 K.
Interpenetrating polymer networks of poly(carbonate‐urethane) and polymethyl methacrylate
Authors: Frisch Harry L. , Zhou Peiguang , Frisch K. C. , Xiao X. H. , Huang Misty Weiyu , Ghiradella H. 
Published: April 2003

AbstractWe report the synthesis and characterization of interpentrating polymer networks (IPN's), pseudo INPN's, and blends of urethane‐containing aliphatic polycarbonates (PCU) and polymethyl methacrylate (PMMA). The simultaneous full IPN's of PCU's and PMMA over the whole composition range have only one Tg, as determined by DSC and DMA which, together with transmission electron microscopy observations, suggest a single phase morphology even though the linear chain blends are completely immiscible. The full IPN's exhibit a maximum tensile strength at a certain composition, and superior solvent and heat resistance as compared to the pseudo IPN's, linear blends, and the pure crosslinked PCU's and PMMA.
Reactions in aminosilane‐epoxy prepolymer systems. II. Reactions of alkoxysilane groups with or without the presence of water
Authors: Serier A. , Pascault J. P. , Lam Thanh My 
Published: April 2003

AbstractThe hydrolysis and reactions of alkoxy silane groups have been studied on a model compound (TA) prepared from 2 mol of phenyl glycidyl ether and 1 mol of aminopropyl triethoxy silane. At low (40°C) and high (140°C) temperatures, the monomer conversion and the evolution of the molecular mass are followed by size exclusion chromatography (SEC). During the same reaction time, the evolution of the functional groups, hydroxyl CHOH, ethoxy OC2H5, and siloxane SiOSi, is observed by FTIR spectroscopy. Without the presence of water, reactions between hydroxyl and ethoxy silane lead to gelation at the end of the reaction. A by‐product, probably a cyclic tetramer is also formed. After the hydrolysis, the reaction of the model compound is quite different. The product of reaction is always soluble, even after a treatment at high temperatures, and the evolution of the molecular mass versus the reaction time seems to correspond to the condensation giving a dead cyclic tetramer. From this study it is evident that the curing cycle has a great influence on the properties of the interface of a composite based on a epoxy matrix.
Syntheses and polymerization of (meth)acrylates containing spiro ortho ester moieties
Authors: Kitamura Naoya , Takata Toshikazu , Endo Takeshi , Nishikubo Tadatomi 
Published: April 2003

AbstractAcrylates and methacrylates bearing pendant spiro ortho ester groups (3) were prepared by the reaction of (meth)acrylic acid with bromomethyl spiro ortho esters (2) in the presence of 1,8‐diazabicyclo [5.4.0] undec‐7‐ene (DBU). These monomers were copolymerized with styrene (St) at 60°C in the presence of α,α'‐azobisisobutyronitrile (AIBN) to give the corresponding copolymers with M̄n 6000‐17000 and their compositions were in proportion to the feed ratios. Similarly, the copolymerization of 3 with acrylonitrile (AN) was carried out at 60°C to obtain the corresponding copolymers with the similar compositions to the feed ratios. Two kinds of 3‐St copolymers with different compositions were treated with BF3OEt2 in refluxing methylene dichloride affording the crosslinked polymers quantitatively. Slight expansion in volume was observed during the crosslinking.
Interfacial polycondensation and characterization of polyphosphates and polyphosphonates
Authors: Richards M. , Dahiyat B. I. , Arm D. M. , Lin S. , Leong K. W. 
Published: April 2003

AbstractThe synthesis of four bisphenol A‐based polyphosphates and phosphonates was accomplished. The polymerization involved a condensation between bisphenol A and a phosphorodichloridate. The heterophasic polycondensation technique was used with the aid of a phase transfer catalyst to yield molecular weights in the range of 20,000–40,000. The polymers were characterized by FT‐IR, FT‐NMR, and DSC. Systematic studies on the interfacial polymerization indicated that a more concentrated organic phase and a slight excess of diol favored the production of high molecular weight polymers. An optimum concentration of 5–10 mol % was observed for three different phase transfer catalysts. Kinetic studies showed that the polymerization was complete within the first 10 min. The degree of agitation was shown to be important, as the overhead mechanical stirrer was not as effective as the blender. In addition, crosslinking with pentaerythritol yielded significant increases in the molecular weights of these polymers.