bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nucleic acid base grafted imino polyurethane
Authors: Lu C. X. , Yang Yang , Xiao Chaodong , Ji Aixue 
Published: April 2003

AbstractPreparation of two model polymers of polynucleotides with linear polyurethane backbone and 2‐(thymin‐1‐yl)propionyl or 2‐(uracil‐1‐yl)propionyl group as grafted pendant are described. 2‐(Thymin‐1‐yl)propionic acid (TPA) and 2‐(uracil‐1‐yl)propionic acid (UPA) were grafted into partial imino functionalized polyurethane, poly[(β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NH‐75), at the secondary amino group through amide bonds with 1‐hydroxybenzotriazole (HOBT) using the active ester technique. Two novel polymer models of polynucleotides, poly[(N‐(2‐(thymin‐1‐yl)propionyl)‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NT‐75) and poly[(N‐(2‐(uracil‐1‐yl)propionyl)‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NU‐75) were obtained. The imino polyurethane PU‐NH‐75 was produced from the partially deprotected N‐Cbz imino polyurethane, poly[N‐(benzyloxycarbonyl‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)] (PU‐NCbz) which was prepared by the polyaddition of 4,4′‐diphenylmethane diisocyanate (MDI) with diol monomer N‐benzyloxycarbonyl‐β,β′‐dihydroxyethylamine (CbzHEA). Selective N‐protection of N‐benzyloxycarbonyloxy‐5‐norbornene‐2,3‐bicarboximide (CbzONB) with β,β′‐dihydroxyethylamine (HEA) gave the N‐Cbz protected diol monomer HEA. The related monomer model compounds were also prepared by the same methods.
A thermally stable polybenzimidazole polybenzoxazole segmented block copolymer
Authors: Gordon Bernard , Kumpf Robert J. , Painter Paul C. 
Published: April 2003

Abstractm‐phenyl benzoate end‐capped pre‐polybenzoxazole oligomer and a 3,4‐diaminobenzene endcapped pre‐polybenzimidazole were synthesized. These functionalized oligomers were then condensed to give a polybenzoxazole‐polybenzimidazole segmented block copolymer. The functionalized oligomers were characterized by proton NMR, diffuse reflectance FTIR, and thermal gravimetric analysis. The final block copolymer was characterized by diffuse reflectance FTIR and thermal gravimetric analysis.
Cyclo dehydration reaction of polyhydrazides. I. Kinetic parameters obtained with nonisothermal thermogravimetry
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A. 
Published: April 2003

AbstractThe thermal conversion reaction of poly‐(1,3‐phenyl‐1,4‐phenyl)‐hydrazide into poly‐(1,3‐phenyl‐1,4‐phenyl)‐1,3,4‐oxadiazole has been studied using thermogravimetry (TG). For the evaluation of the energie of activation and other kinetic parameters of this cyclo dehydration reaction a method developed by Ozawa was used, where polymer samples are heated with different constant heating rates. With this method the energy of activation can be determined accurately as a function of the degree of conversion. In this way a parallel reaction could be observed starting at the end of the nonisothermal conversion process. The polymer was used in two different morphological states, a powder and a film. A slightly higher energy of activation and a considerably higher pre‐exponential factor were observed for the film indicating a dependency of the kinetics on the morphological state or on the history of the polymer sample.
Cyclo dehydration reaction of polyhydrazides. II. Kinetic parameters obtained from isothermal thermogravimetry
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A. 
Published: April 2003

AbstractThe kinetics of the thermal conversion reaction of poly‐(1,3‐phenyl‐1,4‐phenyl)‐hydrazide into poly‐(1,3‐phenyl‐1,4‐phenyl)‐1,3,4‐oxadiazole have been studied with isothermal thermogravimetry in continuation of a study with nonisothermal thermogravimetry described in a previous paper. Although the isothermal measurements are much more time‐consuming, they provide some new information and insight about the cyclo dehydration reaction of the polyhydrazide. The physical state of the sample, rubbery or glassy, seems to influence the kinetics considerably. The kinetic parameters determined with the isothermal method for the polymer in its glassy state agree well with the parameters derived from the previously reported nonisothermal measurements, while the kinetic parameters for the expected rubbery state differ considerably. The morphological state or the history of the polymer has also a considerable influence on the kinetics of the isothermal conversion process. The powder form of the polymer has a much lower isothermal conversion rate than the film form.
Tough epoxy resins cured with aminimides
Authors: Inubushi Shinzo , Ikeda Tomiki , Tazuke Shigeo , Satoh Tasuku , Kumagai Yaomi 
Published: April 2003

AbstractAminimide compounds (1–4) thermally generating isocyanates and tertiary amines were found to be excellent curing agents for epoxy resin. Tensile behavior, glass transition temperature, and degree of curing for the combination of EPIKOTE 828 prepolymer with a series of curing agents (1–4) are reported. The resins exhibit a large elongation at breakage and a high fracture energy per unit volume. The epoxy resins (EP‐AI) cured with 3 or 4 containing no hydroxyl group showed larger ultimate elongations (up to 15%) and higher fracture energies (ca. 8 J/cm3) than the resins (EP–AIOH) cured with 1 or 2. The curing reaction depends on the structure of aminimide (presence of hydroxyl group and generation of mono‐ or bisisocyanates). The origin of toughness and dependence of physical properties on the curing condition and the structure of aminimides were discussed. It was concluded that relatively slow curing at elevated temperature controlled by thermal decomposition of aminimides was a reason for the toughness.
Copolymerization of diethyl 2‐(methacryloyloxy) ethyl phosphate with alkyl acrylates: Reactivity ratios and glass transition temperatures
Authors: Nair C. P. Reghunadhan , Clouet G. , Brossas J. 
Published: April 2003

AbstractSoluble copolymers of diethyl 2‐(methacryloyloxy) ethyl phosphate (DMP) with methyl methacrylate (MMA), methyl acrylate (MA), ethyl acrylate (EA) and butyl acrylate (BA) were synthesized by radical copolymerization in benzene solution using azobis(isobutyronitrile) (AIBN) as initiator. The monomer reactivity ratios of these systems at 60°C were determined by the conventional schemes using the methods of Fineman–Ross, Joshi‐Joshi, and Kelen–Tüdos. DMP underwent a completely random and azeotropic copolymerization with MMA whereas in its reaction with the other acrylates DMP entered preferentially into the polymer chain. The reactivities of DMP‐terminated polymer radicals towards the acrylate monomers were found to be in the order: MMA > EA > MA > BA. An increase in solvent polarity decreased the relative reactivity of DMP for the DMP‐MMA pair. An examination of the molecular weights of the copolymers revealed the occurrence of chain transfer caused by DMP. The copolymer glass transition temperatures were determined and the variations of Tg with copolymer compositions were discussed according to the theory of Johnston, taking into account the effect of the sequence distributions of the comonomers on Tg. The Tgs of the alternating copolymers of DMP with the four alkyl acrylates were calculated.
Synthesis and electrical conductivity of poly(arylene vinylene). I. Poly(2,5‐dimethoxyphenylene vinylene) and poly(2,5‐dimethylphenylene vinylene)
Authors: Antoun S. , Karasz F. E. , Lenz R. W. 
Published: April 2003

AbstractThe highly conjugated aromatic polymers, poly(2,5‐dimethoxyphenylene vinylene) and poly(2,5‐dimethylphenylene vinylene), were obtained from their water soluble, sulfonium salt precursor polymers. Films of these polymers were reacted with either AsF5 or I2 vapor. Poly(2,5‐dimethoxyphenylene vinylene) showed increases in electrical conductivity of up to 14 to 15 orders of magnitude for these two dopants, while an 8 to 9 order of magnitude increase was observed for poly(2,5‐dimethylphenylene vinylene) with the same dopants. The synthesis of the precursor polymers, the properties and elimination reactions of films of the precursors, the doping reactions, and the conductivities of the resulting phenylene vinylene films are discussed.
Epoxidation of polybutadiene and styrene–butadiene triblock copolymers with monoperoxyphthalic acid: Kinetic and conformation study
Authors: Huang Wen‐Kuei , Hsiue Ging‐Ho , Hou Wei‐Hsin 
Published: April 2003

AbstractThe rates of epoxidation of polybutadiene homopolymers and styrene–butadiene triblock copolymers with monoperoxyphthalic acid were measured at four temperatures in homogeneous solution. Dioxane and mixed solvents with chloroform were used as reaction media. Activation energy values were also calculated for polymers different in microstructure and styrene content. Viscometry in a modified viscometer was performed and combined with kinetic measurement to monitor the conformational change during epoxidation. Cis‐content in polybutadiene and styrene content in SBS exhibit only slight effect on epoxidation in dioxane. The addition of chloroform promotes the reaction rate remarkably and enlarges the difference between polymers. Explanations were given including the solvent effect on reduced viscosity, which was used to correlate the conformational change of polymer chains. NMR and GPC analysis confirmed the absence of ring opening and degradation during epoxidation up to 54% epoxy group content.
High temperature phosphorylated or nonphosphorylated laminating resins based on maleimido‐substituted aromatic s‐triazines
Authors: Melissaris Anastasios P. , Mikroyannidis John A. 
Published: April 2003

AbstractSeveral new phosphorylated or nonphosphorylated maleimide or nadimide systems containing s‐triazine rings were synthesized. Their synthesis was accomplished by simple methods utilizing readily available and relatively inexpensive starting materials. All polymer precursors were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. They were thermally polymerized to heat‐resistant laminating resins. Thermal characterization of monomers and their cured resins was achieved using differential thermal analysis (DTA), dynamic thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). The cured resins were stable up to 304–330°C both in nitrogen and air atmospheres and formed anaerobic char yield 49–59% at 800°C. The phosphorylated polymers showed a lower temperature of initial weight loss but afforded higher anaerobic char yield than did the corresponding nonphosphorylated polymers. The thermal properties of the polymers were correlated with their chemical structure.
Radical‐catalyzed homopolymerization of maleic anhydride in presence of polar organic compounds
Authors: Gaylord Norman G. , Mehta Rajendra 
Published: April 2003

AbstractPolar organic compounds either (1) inhibit the peroxide‐catalyzed bulk homopolymerizations of both MAH and MMA at 80°C, (2) do not inhibit the polymerization of either MAH or MMA, or (3) inhibit the polymerization of MAH but not that of MMA. Compounds generally used as polymerization inhibitors or antioxidants inhibit the polymerizations of both MAH and MMA, presumably by interaction with peroxide decomposition products. Ketones, ethers, acids, esters, nitriles, imides, sulfones, sulfonates, sulfonamides, and acyl disulfides do not inhibit either MAH or MMA polymerization. However, amides, lactams, carbamates, amine oxides, phosphites, phosphates, phosphonates, phosphoramides, phosphine oxides, monosulfides, sulfoxides, aryl disulfides, and thiazyl disulfides inhibit the polymerization of MAH but not that of MMA. Inhibition presumably occurs as a result of electron transfer from the nitrogen‐, phosphorous‐ or sulfur‐containing electron donor compound to the MAH carbocation which is an intermediate in the polymerization of MAH.
Mechanistic and kinetic studies on the photoinitiated polymerization of tetrahydrofuran
Authors: Yaǧci Yusuf , Ledwith Anthony 
Published: April 2003

AbstractPolymerization of tetrahydrofuran (THF) (bulk) promoted by a free radical source, 2,2‐dimethoxy‐2‐phenyl acetophenone (DMPA), in the presence of 4,4′‐di‐(methylphenyl)iodonium hexafluorophosphate was studied in detail. Rate dependence of the polymerizing system on both DMPA and the iodonium salt was studied dilatometrically. Rate saturation for the iodonium salt was attributed to the formation of iodobenzene, which may react with propagating cations to form an iodonium salt. DMPA was shown to be an efficient transfer agent in the cationic polymerization of THF. A transfer constant for DMPA was estimated to be 2.8 and, whilst the precise details of the overall mechanism cannot be deduced from the present results, it may result in functionalized polytetrahydrofuran chains having photochemically active end groups.
Emulsifier‐free emulsion copolymerization of styrene and butyl acrylate. II. Kinetic studies in the presence of ionogenic comonomers
Authors: Guillaume J. L. , Pichot C. , Guillot J. 
Published: April 2003

AbstractBatch emulsifier‐free copolymerizations of styrene (S) and butyl acrylate (BuA) have been performed for a S/BuA weight ratio = 50/50 in the presence of two types of functional comonomers [methacrylic acid (MAA) at different pHs] or potassium sulfopropylmethacrylate (SPM) and two initiators [potassium persulfate or 4–4′azobiscyanopentanoic acid (AZO)]. The use of AZO/MAA system results in the formation of polymer particles with only surface carboxylic end groups. The particle size of the final latexes can be adjusted with the MAA concentration, provided the polymerization is carried out at pH > 6.5. However, the higher the MAA concentration, the sooner the polymerization levels off in conversion. With the K2S2O8/SPM system, particles bearing only sulfate and sulfonate groups are produced and the polymerization is complete. In that case, the particle size of the final latexes is smaller than with the previous system and 30% of the SPM is fixed on the particle surface, instead of 10% with MAA. Using SPM, a too high functional monomer concentration results in the latex destabilization caused by the formation of a large amount of polyelectrolytes. Kinetic studies indicate that most of the functional monomer is incorporated onto the particle surface during the last 30% conversion of the polymerization. A tentative explanation of such a behavior is discussed, based on the existence of two polymerization loci in the latex system.
Poly(vinyl alcohol) obtained through polymerization of some vinyl esters
Authors: Imai Kiyokazu , Shiomi Tomoo , Tezuka Yasuyuki , Kawanishi Toshiaki , Jin Tomofumi 
Published: April 2003

AbstractBulk and/or solution polymerizations of a series of vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, and vinyl benzoate were conducted. Iodine‐coloration, 1,2‐glycol structure, molecular weight, and tacticity (triad and pentad) were measured for the resulting poly(vinyl alcohol)s (PVAs). The iodine‐coloration abilities of PVAs, derived from poly(vinyl ester)s that were obtained through bulk polymerization at 60°C, depended on the starting monomer, increasing in the following order: vinyl benzoate < vinyl acetate < vinyl propionate < vinyl butyrate < vinyl pivalate. In solution polymerizations of vinyl propionate and vinyl butyrate, it was revealed that the tacticity of the derived PVAs apparently depended on the type and amount of polymerization solvent employed, as found previously in the case for vinyl acetate. The iodine‐coloration of these PVA samples varied in the same order as their syndiotactic content, while no relationship was observed toward their 1,2‐glycol content. The probabilities of the syndiotactic propagation at 60°C were estimated as 0.49 (benzoate), 0.54 (acetate), 0.55 (propionate), 0.56 (butyrate), and 0.60 (pivalate), respectively.
Aromatic copolyesteramides by the direct polycondensation with diphenyl chlorophosphate and carboxamides in pyridine
Authors: Higashi Fukuji , Hirakouchi Hiroshi 
Published: April 2003

AbstractThe reaction promoted by a Vilsmeier adduct derived from diphenyl chlorophosphate and N,N‐dialkylcarboxamides such as N,N‐dimethylformamide was successfully used for the preparation of soluble copolyesteramides directly from aromatic dicarboxylic acids, bisphenols, and a wide range of mole percent diamines. The polycondensation was affected by the carboxamides used, and an attempt was made to explain the effect by the ester sequence in polyamide units by examining a competitive reaction of benzoic acid with a phenol and an aniline and by examining the thermal properties of the copolymers produced.
Synthesis, bulk characterization, and surface characterization of p‐hydroxystyrene/styrene copolymers
Authors: Majumdar Debesh , Ratner Buddy D. 
Published: April 2003

AbstractStyrene/p‐hydroxystyrene copolymers were prepared from copolymers of styrene and p‐benzyloxystyrene by cleavage of the ether bond. Nuclear magnetic resonance spectroscopy was used to characterize the polymers before and after the ether cleavage reaction. Reactivity ratios were calculated by applying the method of least squares to data generated from the Fineman–Ross equation (r1 = 0.37, r2 = 0.28). The surface chemistry of centrifugally cast films of the homopolymers and the copolymers was studied by using electron spectroscopy for chemical analysis (ESCA). The Zisman contact angle method was used to determine the critical surface tension in air for each polymeric surface. Water contents of hydrated films were determined gravimetrically. The polar character of the surface was shown to increase to a small degree with an increase in the p‐hydroxystyrene component. Polymers with high p‐hydroxystyrene contents did not exhibit pronounced hydrogel character.
Graft copolymerization of cellulose initiated by ceric salts: Effect of reaction conditions on the consumption of ceric ion
Authors: Graczyk Tomasz , Hornof Vladimir 
Published: April 2003

AbstractA soluble monomer [methyl acrylate (MA)] and an insoluble monomer [butyl methacrylate (BMA)] were grafted onto cellulose by three types of ceric salts under both oxygen‐free conditions and in the presence of oxygen. For comparison, Ce(IV) consumption during cellulose oxidation was also determined under similar reaction conditions. Slightly more Ce(IV) was consumed during cellulose oxidation in the presence of oxygen. During graft copolymerization of MA under oxygen‐free conditions, the consumption of Ce(IV) was much lower than during cellulose oxidation regardless of the type of ceric salt employed. The opposite was observed in the presence of oxygen: much more Ce(IV) was consumed during grafting than during cellulose oxidation. The consumption of Ce(IV) in the graft copolymerization of BMA by ceric sulfate was nearly independent of reaction conditions and it was approximately the same as in cellulose oxidation. In the reaction initiated by ceric ammonium nitrate under oxygen‐free conditions, less Ce(IV) was once again used up during grafting than during cellulose oxidation. However, the difference was much smaller than in the case of MA.
Characterization of the functionalization reaction product of poly(styryl)lithium with ethylene oxide
Authors: Quirk Roderic P. , Ma Jing‐Jing 
Published: April 2003

AbstractThe functionalization reaction of poly(styryl)lithiums (Mn = 1.3–9.9 × 103) with ethylene oxide in benzene proceeds quantitatively ( > 99%) to produce the corresponding hydroxyethylated polymer as determined by vapor phase osmometry, size exclusion chromatography, end‐group titration, thin layer chromatography, and 1H‐ and 13C‐NMR spectroscopy. 13C‐NMR spectral analysis of the functionalized polystyrene with Mn = 1.3 × 103 was consistent with addition of only one ethylene oxide unit to poly(styryl)lithium, i.e., no evidence for ethylene oxide oligomerization was observed.
Polyamide synthesis by the direct polycondensation with phenylphosphonic dichloride in pyridine
Authors: Kigashi Fukuji , Lee Yen‐Nehg , Kobayashi Akira 
Published: April 2003

AbstractThe direct polycondensation of isophthalic acid (IPA) and aromatic diamines with a new phosphorus compound, phenylphosphonic dichloride (PPDC), was studied. PPDC could actually react with nearly a two molar amount of carboxyl groups, but more than 75 mol % PPDC with respect to the carboxyl groups of IPA were satisfactorily used in the polycondensation. The initial reaction of IPA with PPDC in pyridine at room temperature and then at 120°C was needed to complete the activation, and the subsequent aminolysis at 120°C for 3 h was most effective. The polyamides of high inherent viscosity were obtained even from weakly basic aromatic diamines, and their values were more than those obtained by the conventional method. In their thermal properties determined by the DTA, they showed Tgs and Tms higher than those reported before.
Intumescent flame retardants for polymers. IV. The polycarbonate–aromatic sulfonates system
Authors: Ballistreri Alberto , Montaudo Giorgio , Scamporrino Emilio , Puglisi Concetto , Vitalini Daniele , Cucinella S. 
Published: April 2003

AbstractThe mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol‐A carbonate) (PC) has been investigated. These compounds are capable of inducing a self‐extinguence in PC even when present in very low amounts (0.2–1%). Thermogravimetric and flash pyrolysis–GC–MS data show the thermal degradation rate of PC enhanced, and the distribution of the volatile pyrolysis products was modified by these additives. Oxygen Index (OI) and Nitrous Oxide Index (NOI) measurements indicate a FR condensed‐phase mechanism of these additives. Traces of polymer surface temperature against time, measured under forced flame conditions, show that the expanded carbon layer formed in the combustion of polycarbonate–aromatic sulfonate blends produces a heat insulating effect toward the undecomposed bulk. The overall evidence leads us to conclude that aromatic sulfonates cause the flame extinguishment in polycarbonate by an intumescent phenomenon.
The synthesis and characterization of poly(methylene terephthalate)
Authors: Cimecioglu A. L. , East G. C. , Morshed M. , Zeronian S. H. 
Published: April 2003

AbstractPoly(methylene terephthalate) (1GT) has been synthesized via the reaction of cesium or potassium terephthalates with dibromomethane or bromochloromethane in N‐methylpyrrolidone at temperatures of 80–125°C. The polymerization was relatively slower with the latter substrate, though the potassium salt was found to be equally as efficient as its cesium counterpart with dibromomethane. The polymer is insoluble in all common polyester solvents, and its high molecular weight nature (DPn ≥ 25) was inferred from elemental analyses and its fiber forming capacity. Thermal analyses indicated that 1GT possesses poor thermal stability and decomposes rapidly during melting, the initial process being thought to be the splitting out of formaldehyde. 1GT polymers were shown to contain a homologous series of cyclic oligomers (from dimer to decamer); the two most predominant were tentatively identified as the cyclic trimer and tetramer. No change in the cyclization efficiency was observed when the potassium counterion was substituted for cesium with Br CH2 Br whereas a drastic reduction in the cyclic content was obtained using Br CH2 Cl (with Cs+). The two most important features of the polymerization are the insensitivity of the reaction to the stoichiometric equivalence of the reactants and the production of reasonably high molecular weights at low conversions. It is suspected that the polymerization might be occurring through an interfacial mechanism.