bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of semi‐ and full‐interpenetrating polymer networks of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and polydimethylsiloxane
Authors: Frisch Harry L. , Gebreyes Kassu , Frisch Kurt C. 
Published: April 2003

AbstractThe synthesis and characterization of pseudo or semi‐ and full‐interpenetrating polymer networks (IPNs) of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and polydimethylsiloxane were performed. We observed that in full IPNs, the elasticity of the IPN samples increased very drastically, as the composition of polydimethylsiloxane increased (i.e. 0–60%) while the tensile strength (TS) and the glass transition temperature (Tg) decreases. The pseudo IPNs appeared to consist of two phases while the full IPNs of lower siloxane content were miscible.
Copolymerization of 1‐(trimethylsilyl)‐1‐propyne with disubstituted hydrocarbon acetylenes
Authors: Hamano Toshiyuki , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractCopolymerization of 1‐(trimethylsilyl)‐1‐propyne (MeC ≡ CSiMe3) with several aromatic and aliphatic disubstituted acetylenes (MeC ≡ CPh, n‐BuC ≡ CPh, 2‐octyne, and 4‐octyne) were examined by using Ta and Nb catalysts. The TaCl5–Ph3Bi catalyst was effective in copolymerization with the aromatic acetylenes, whereas the NbCl5–Ph3Bi catalyst was preferable in copolymerization with the aliphatic acetylenes. The copolymerization products were not mixtures of homopolymers but copolymers. The relative reactivity of monomer tended to decrease with increasing steric effect of monomer: 2‐octyne > MeC ≡ CSiMe3 > 4‐octyne > MeC ≡ CPh > n‐BuC ≡ CPh. The copolymers of MeC ≡ CSiMe3 with MeC ≡ CPh [copoly(TMSP/PP)s] had high molecular weight (Mw > 1 × 106), and provided thermally stable tough films. With increasing MeC ≡ CPh content of copoly(TMSP/PP), the oxygen permeability coefficient (P) decreased, while the separation factor (P/P) increased.
The substitution of polychlorotrifluoroethylene with sulfur, selenium, and phosphorus nucleophiles
Authors: Pelter Michael W. , Taylor Richard T. 
Published: April 2003

AbstractThe substitution of polychlorotrifluoroethylene (PCTFE) with sulfur, selenium, and phosphorus nucleophiles is reported. The primary reaction, which extends throughout the bulk of the polymer, is the incorporation of the nucleophile with concommitant loss of chloride. The substituted PCTFE's are studied by 1H‐, 13C‐, 19F‐, and 31P‐NMR, as well as IR, and elemental analysis.
Cationic and polymeric radicals of vinyl monomers in halogenated matrices: An ESR and SCF MO study
Authors: Tabata M. , Lund A. , Samskog P. O. , Lunell S. , Huang M. B. 
Published: April 2003

AbstractThe vinyl monomers methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, and β‐methylstyrene were dissolved in CF3CCl3, x‐irradiated at 4 or 77 K, and investigated by ESR spectroscopy. The molecular cation of methyl acrylate has no resolved hyperfine structure, indicating that the unpaired electron is localized on the carbonyl oxygen. Evidence that a two‐stage photoinduced reaction gives rise to a propagating radical was obtained. Propagating radicals were observed also with methyl methacrylate, acrylic acid, and methacrylic acid as solutes. The positive ion of β‐methylstyrene has been prepared and characterized. The experimental data have been compared with molecular orbital calculations at different levels of approximation.
Thermally reversible, covalently crosslinked polyphosphazenes
Authors: Salamone J. C. , Chung Y. , Clough S. B. , Watterson A. C. 
Published: April 2003

AbstractThe concept of thermally reversible crosslinking was investigated by using poly[bis(trifluoroethoxy)phosphazenes] with different percentages of cyclopentadienylethoxy and dicyclopentadienyldiethoxy substituent groups. The resultant structures of these polymers are discussed and the phenomenon of reversible crosslinking is demonstrated by means of a DSC study and solubility behavior.
Superactive and stereospecific catalysts. II. Kinetics of propylene polymerizations
Authors: Chien James C. W. , Hu Youliang 
Published: April 2003

AbstractThe kinetics of propylene polymerization by superactive CH‐catalyst prepared from toluene solution of MgCl2 · EH/PA/TiCl4–TEA/PES was investigated. The results are compared with CW‐catalyst prepared from crystalline MgCl2/EB/PC/TEA/TiCl4–TEA/MPT (abbreviations given in the text). The former is four times more active than the latter and produces more isotactic polypropylene. The CH‐catalyst has 25% of the Ti as isospecific sites as compared to 6.7% for the CW‐catalysts. These sites have the same rate constant of propagation so that the higher polymerization activity of the CH‐catalyst is attributable simply to a greater number of active sites. Differences in the kinetics of deactivation and of chain transfer for the two catalysts are described.
Synthesis and characterization of urethane polymers containing 2,2′‐biimidazole
Authors: Liu F. J. , Kokorudz J. S. , Collier H. L. 
Published: April 2003

AbstractA heterocyclic nitrogen‐containing system having substituent primary diol function, i.e., 1,1′‐dihydroxethyl‐2,2′‐biimidazole (I), has been prepared and used to synthesize a series of new polyurethanes based on aromatic diisocyanates (TDI, MDI). Variation of solution polymerization parameters permitted the isolation and infrared, NMR, molecular weight, and thermal characterization of polymeric materials. Isolated polymers exhibit a linear structure and have Tg (150–170°C) and thermal stability (205–250°C for 20% weight loss) properties comparable to other typical urethane polymers. Zn2+ complexation was indicated by shifts in the imidazole ringmode infrared vibrational bands at 917 and 1133 cm−1 to higher frequencies.
Activation and racemization of trifluoroacetate esters in the cationic polymerization of styrene
Authors: Matyjaszewski K. , Lin C. H. 
Published: April 2003

Abstract1‐Phenylethyl trifluoroacetate (1) does not react directly with styrene but it is readily incorporated into polymer chains in the presence of an excess of trifluoroacetic acid. The proportion of the nondeuterated 1‐phenylethyl end groups in the polymerization of deuterated styrene coinitiated with the acid was much higher than the proportion of the end groups formed by direct incorporation of the acidic protons ([CH3CHPhCD2CDPh …] > [HCD2CDPhCH2CDPh …]). The racemization of the optically active ester‐(pseudo‐first order rate constant at [HA]0 = 0.79 mol/L at 20°C equals kR = 1.7 × 10−4 S−1) is more rapid than the incorporation of the ester into polymer chains (kE = 1.5 × 10−4 mol−1 Ls−1, [M]0 < 0.4 mol L−1, i.e., kR > kE · [M]). These results and the complete loss of the optical activity in the final polymer indicate that the ester is activated by the acid but it is incorporated into polymer chain via ionic intermediates.
Synthesis and characterization of a multiblock copolymer of poly(N‐isovaleryl ethyleneimine) and poly(ethylene glycol)
Authors: Hsiue G. H. , Swamikannu A. X. , Litt M. H. 
Published: April 2003

AbstractBlock copolymers of poly(N‐isovaleryl ethyleneimine) (PiVEI) and poly(ethylene glycol) (PEG) were synthesized by coupling previously prepared blocks of PEG ditosylate with the dianion of the dihydroxy PiVEI. On the average four blocks coupled together to form the final block polymer. The PiVEI blocks crystallized with the same melting points as in the homopolymer. This restricted the mobility of the PEG blocks and they did not crystallize unless cooled well below room temperature. The mechanical properties of cast films were quite good with a tensile strength of 77 kg/cm2 and an elongation of 120%. The swelling of unoriented and oriented films with water was studied. The unoriented polymer absorbed about its own volume of water, even though PEG comprised only 40% of the total polymer.
Thermotropic liquid crystallinity of copoly(ester‐amides) prepared by the direct polycondensation with diphenyl chlorophosphate in pyridine
Authors: Higashi Fukuji , Arikawa Hideo , Mochizuki Akihiko 
Published: April 2003

AbstractCopolycondensation of isophthalic (IPA) and terephthalic (TPA) acids, methylhydroquinone (MeHQ), and aromatic diamines with diphenyl chlorophosphate (DPCP) in pyridine were investigated. The resulting copoly(ester‐amides) showed optical anisotropy, which was discussed in terms of the ester and amide sequence lengths in the copolymers. The temperature above which the anisotropy was observed varied in the 225 to 300°C range by changing addition time of a mixture of MeHQ and diamines, initial reaction with MeHQ, and the further reaction with diamines.
Benzocyclobutene in polymer synthesis. III. Heat‐resistant thermosets based on Diels–Alder polymerization of a bisbenzocyclobutene and a bismaleimide
Authors: Tan Loon‐Seng , Arnold Fred E. , Soloski Edward J. 
Published: April 2003

AbstractSeveral compatible mixtures of 2,2‐bis[4‐(N‐4‐benzocyclobutenyl) phthalimid‐4‐phenyl]hexafluoropropane (BCB) and 1,1′‐(methylene di‐4,1‐phenylene)bismaleimide (BMI) were prepared according to the molar ratios (BCB : BMI): 1 : 1; 1 : 1.5; 1 : 3; 1.5 : 1. Complete compatibility of the mixtures was evidenced by a single initial Tg. All mixtures showed relatively low initial Tg's (61–70°C) and characteristic polymerization exotherms of benzocyclobutene‐based systems (onset: 221–225°C; maximum: 257–259°C), providing an excellent processing window (ca. 155°C). The cured sample of the mixtures, pure BCB and BMI (250°C; N2; 8 h) were subjected to comparative isothermal gravimetric analysis (ITGA). After 200 h at 650°F (343°C) in circulating air, the cured BMI sample retained only 3% of its original weight, whereas the mixtures of BCB and BMI exhibited thermo‐oxidative stabilities similar to BCB (13–15% weight loss). A model compound was synthesized from the intimate mixture of N‐phenylmaleimide and N‐benzocyclobutenyl phthalimide in 63% yield. The ITGA results and isolation of the model Diels–Alder adduct render strong support to the conviction that Diels–Alder polymerization is indeed the predominant curing process in the BCB/BMI system.
Grafting of vinyl monomers onto sisal fiber in aqueous solution
Authors: Samal Bibhuti B. , Sahu Sagarika , Chinara Braja B. , Nanda S. , Otta P. K. , Mohapatro L. M. , Mohanty Trijama R. , Ray A. R. , Singh K. C. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) onto sisal fibers (chemically modified) was studied using the Mn(III)/EDTA redox system in aqueous solution. The effects of time, monomer (AN), metal ion [Mn(III)] substrate [ethylene diamine tetraacetic acid (EDTA)], temperature, and acid concentration on graft yield have been studied. The effects of thiourea on the graft yield has also been studied. A suitable mechanism is proposed.
Phthalonitrile‐based high temperature resin
Authors: Keller Teddy M. 
Published: April 2003

AbstractAn aromatic, diether‐linked phthalonitrile resin, prepared from 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl, exhibits excellent thermo‐oxidative properties. The resin is easily processed from the melt of the monomer in a controlled manner as a function of the amine curing agent and processing temperatures. Polymerization occurs by a cyclic addition reaction without the formation of volatile by‐products. The polymerization reaction can be stopped at a prepolymer stage. The prepolymer can be stored indefinitely at ambient conditions without further reaction. The modulus and viscoelastic properties of the resin were found to be a function of the postcuring conditions.
Thermally reactive aromatic polyamides
Authors: Evers Robert C. , Moore George J. , Abraham Tonson 
Published: April 2003

Abstract2,5‐Bis(phenylethynyl)terephthaloyl chloride and 4,6‐bis‐(phenylethynyl)isophthaloyl chloride were synthesized in a multistep reaction scheme from 2,5‐dibromoterephthaldehyde and 4,6‐dibromoisophthaldehyde, respectively. Low temperature solution polycondensation of these novel monomers and tolane‐2,4′‐dicarbonyl chloride with aromatic diamines yielded aromatic polyamides containing phenylethynyl moieties. Inherent viscosities of 0.20–0.51 dL/g were recorded. Attempts to carry out the homopolymerization of 2‐(3‐aminophenylethynyl)benzoyl chloride hydrochloride under similar conditions led to low molecular weight polyamide. Under differential scanning calorimetry and thermal mechanical analysis, the polyamides exhibited strong exotherms with onset occurring in the 185–225°C range. The exotherms were attributable to intramolecular cycloaddition of phenylethynyl moieties with amide groups to give polybenzalphthalimidine structures. Curing of a pressed pellet specimen for 16 h at 250°C under a nitrogen atmosphere resulted in partial conversion to a polybenzalphthalimidine structure with a concomitant increase in the polymer glass transition temperature. Isothermal aging in air of the cured specimen at 316°C (600°F) led to 25% weight loss after 200 h.
Separation and structural analysis by 1H‐NMR of the telomers of methyl methacrylate with thiophenol
Authors: Bessiere Jean‐Marie , Boutevin Bernard , Sarraf Lena 
Published: April 2003

AbstractThe stereoselectivity of the addition step and the transfer step of the radical telomerization of methyl methacrylate with thiophenol has been studied by determining the structure and the amount of each isomer by 1H‐NMR. We found, in this case, that the addition step gave preferentially a diad r and that the transfer step gave preferentially a diad m. On the other hand, the tacticity observed for higher telomers is preferentially syndiotactic, similar to that of the poly(methyl methacrylate) prepared by radical initiation. The propagation process for radical telomerization obeys, as for the radical polymerization, Bernoulli's statistics.
Polymerization photoinitiated by carbonyl compounds. VIII. Solvent and photoinitiator concentration effects
Authors: Encinas M. V. , Garrido J. , Lissi E. A. 
Published: April 2003

AbstractThe interaction of benzil and thioxanthone triplets with triethylamine leads to the production of free radicals that are able to initiate the polymerization of methylmethacrylate and vinyl acetate. The process is mediated by a charge transfer complex. The initiation efficiency is higher in benzene than in acetonitrile, a result explained in terms of competition between back electron transfer, production of free ions and ketyl radical formation. The initiation efficiency decreases when the carbonyl concentration increases, because of the occurrence of a radical molecule reaction such as
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The α‐hydroxy radicals produced in this reaction are unable to initiate the polymerization chain.
Oligomerization of ethylene with a homogeneous sulfonated nickel ylide–aluminum alkoxide catalyst
Authors: Kissin Yury V. , Beach David L. 
Published: April 2003

AbstractVarious organoaluminum compounds strongly affect reactivity of a sulfonated nickel ylide complex in its reactions with ethylene. The complex, if used alone, is an active single‐component catalyst for ethylene oligomerization to linear 1‐alkenes. Al(C2H5)3 and tetraethylaluminoxane completely deactivate the catalyst by reducing it to Ni(O). Alkylaluminum halides, such as Al(C2H5)2Cl and Al(C2H5)Cl2, convert the nickel complex into a very active catalyst for ethylene dimerization to mixtures of butenes. Aluminum alkoxides, e.g., Al(C2H5)2OC2H5, AlC2H5(OC2H5)2, and Al(OC2H5)3, significantly increase oligomerization activity by a factor of 20–100. The distribution of 1‐alkenes (in the C4C40 + range) produced with the sulfonated nickel ylide–aluminum alkoxide catalyst follows the Flory molecular weight distribution law. The ratio of the chain termination to chain propagation rate constants is ca. 0.3 and is not temperature‐sensitive in the 50–120°C range. Kinetic analysis of the ethylene oligomerization reaction with the binary catalytic system showed that the number of active centers is proportional to the nickel complex concentration. The effective activation energy of ethylene oligomerization with the catalyst is ca. 27 kJ/mol. The oligomerization catalysts loose their activity in time. The activity decay follows the first‐order kinetic law. The rate of the decay increases with increasing temperature and is caused mainly by the intrinsic instability of active species.
Miniemulsion copolymerization of vinyl acetate and butyl acrylate. III. Experimental evidence for the role of the cosurfactant
Authors: Delgado Joaquin , El‐Aaser Mohamed S. , Silebi Cesar A. , Vanderhoff John W. 
Published: April 2003

AbstractThe role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50 : 50 molar ratio vinyl acetate–butyl acrylate monomer mixture is analyzed from an experimental point of view. The main factor responsible for the different kinetic behavior between the miniemulsion and conventional emulsion copolymerization processes was found to be the different particle nucleation mechanism operating in each process. Experimental evidence is presented indicating that in the miniemulsion copolymerization particle nucleation takes place in the preformed stable submicron monomer droplets.
Uncatalyzed polymerization of bistriazolinediones with electron‐rich aromatic compounds via electrophilic aromatic substitution
Authors: Mallakpour Shadpour E. , Butler George B. 
Published: April 2003

AbstractThe reaction of 4‐substituted‐1,2,4‐triazoline‐3,5‐diones(4R‐TD's), i.e., MeTD(4‐methyl substituted) and PhTD(4‐Phenyl substituted) with electron rich aromatic compounds were investigated. N,N‐Dimethylaniline undergoes reaction instantaneously with MeTD and PhTD. Electrophilic aromatic substitution occurred at room temperature at the para position without use of any catalyst. N,N,N′,N′‐tetramethyl‐m‐phenylenediamine (TMPDA) undergoes reaction with 2 mol of PhTD and MeTD which lead to the formation of 2:1 adducts in high yields. These compounds were fully characterized by IR, 13C‐NMR, 1H‐NMR and elemental analysis and were used as model compounds. The reaction of bistriazolinediones with TMPDA was performed in dimethylformamid at room temperature. The reactions are exothermic, fast, and gave novel polymer structures via electrophilic aromatic substitution. Some physical properties and structural characterization of these new polymers have been studied, and will be reported.
Photoresponsive inorganic polymers obtained by metal alkoxides
Authors: Ueda Hisashi 
Published: April 2003

AbstractThe polymerization of metal alkoxides was carried out in organic solvents and light responsive polymers were obtained. As starting materials for polymerization, Ti(OBu)4, Zr(OBu)4, Nb(OEt)5, and Ta(OEt)5 were used. The polymerization yield roughly corresponds to the formation of TiO2, ZrO2, NbO2(OEt), and TaO2(OEt), respectively. The polymers obtained are paramagnetic and all give similar (dark) ESR spectra. When illuminated by visible light, a new ESR absorption is detected in the vicinity of g = 2.00, or 330–340 mT (for 9.450 GHz) region. The formation and decay rates of this ESR absorption was measured. The decay rate constants obtained from the formation curves were larger than those obtained from the decay curves, indicating relatively short lived species are formed during light illumination. The polymers thus prepared have photocatalytic activity and can photolyze 1 : 1 methanol/water system with visible light. Other possible uses of these polymers as paramagnetic or photochromic materials are discussed.
Degradation of epoxidized polyenes in the presence of phthalic acid
Authors: Huang Wen‐Kuei , Hsiue Ging‐Ho 
Published: April 2003

AbstractViscometry was used to follow the epoxidation of polybutadiene and styrene–butadiene triblock copolymers (SBS) with monoperoxyphthalic acid (MPPA). Long reaction periods lead to an abnormal increase and then drop in reduced viscosity. The increasing viscosity is due to repulsion between oxirane group and its ring‐opening product with phthalic acid, while the viscosity drop can be correlated with a decrease of molecular weight. Long‐term storage of the epoxidized polyenes in the reaction solution containing phthalic acid, which is the derived product from MPPA, also leads to the dramatic decrease in molecular weights. The occurrence of degradation was confirmed by GPC analysis of molecular weight and molecular weight distribution. Chloroform accelerated the degradation reaction, possibly through the generation of hydrochloric acid. The degraded products were isolated and analyzed by GPC and NMR. A free radical mechanism was proposed for the oxidative degradation of epoxidized polyenes after excessive reaction.
Analysis of model polyurethane thermolysis products by direct mass spectrometer sampling
Authors: Greenwalt C. C. , Futrell Jean H. , Lyman Donald J. 
Published: April 2003

AbstractThe results obtained using a molecular beam direct sampling mass spectrometer system to determine the thermolysis products and investigate the decomposition kinetics of two model linear polyurethanes are reported. The polyurethanes are shown to degrade in this system strictly to the polycondensation reactants. These results conflict with previous research which indicated that the model polymers degraded by different mechanisms and yielded different degradation products. Kinetic analysis of results obtained from rapid thermolysis of the polymer in the ion source chamber of the pyrolysis mass spectrometer using the activation energy and frequency factor parameters deduced from thermogravimetric analysis of the same polymers reproduced the experimental data on decomposition as a function of time and temperature quite satisfactorily.
Synthesis and polymerization of (E,E)‐[6.2](9,10)anthracenophane‐1,5‐diene
Authors: Glans Jeffrey H. , Longone Daniel T. 
Published: April 2003

AbstractThe title compound has been synthesized by dimerization of a substituted p‐xylylene, generated via a 1,8‐Hofmann elimination. Several unique isomers of this dimer are also obtained. The title diene can be polymerized cationically to give low molecular weight polymer. Oxidative doping of this polymer with iodine forms a material with a conductivity of 3 × 10−4 S/cm. In contrast to previously reported anthracenophanes this polymer is photochemically unreactive.
Surface graft polymerization of acrylamide onto poly(ethylene terephthalate) film by UV irradiation
Authors: Uchida Emiko , Uyama Yoshikimi , Ikada Yoshito 
Published: April 2003

AbstractTo improve the low water wettability of poly(ethylene terephthalate) (PET), graft polymerization of acrylamide (AAm) by UV irradiation was performed onto the surface of a PET film with the simultaneous irradiation method without using a photo sensitizer. The PET film immersed in a 10 wt % deaerated aqueous solution of AAm was found to become highly hydrophilic upon UV irradiation. Optical microscopy on cross sections of grafted films showed that localization of the graft polymerization was restricted to a thin surface region of the film. Both the low concentration of polymer radicals formed by UV irradiation and the monomer penetration limited to the film surface would be responsible for localization of the grafted layer to the film surface region. Pretreatment of the PET film with benzyl alcohol was effective for enhancement of the graft polymerization. Retention of high hydrophilicity of the surface even after rigorous extraction of homopolymer and a comparative study of polymerization without UV irradiation strongly suggested that UV irradiation of the PET film under immersion in the deaerated AAm aqueous solution would lead to formation of the true graft copolymer.