bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal analyses of polymers. III. Influence of isocyanate structure on the molecular interactions in segmented polyurethanes,
Authors: Miller G. W. , Saunders J. H. 
Published: April 2003

AbstractThe thermal responses of various polyurethane elastomers in the form of changes in heat capacity, linear expansion, and tensile strain have been examined. Most of the change which can be attributed to the backbone of polyethylene adipate, found in several modes of thermal analysis, are still apparent, though shifted somewhat, among most of the diisocyanate extended elastomers used in this study. Tolylene diisocyanate extension changes the modulus properties markedly, low modulus properties being observed at ambient temperatures. Both hydrogenated MDI and MDI elastomers show comparable expansion and modulus response, whereas the hydrogenated TDI elastomer does not have the same characteristics as TDI‐based elastomers. The thermal properties of the hydrogenated TDI elastomer resemble more those exhibited by the polyol mixture extended with hexamethylene diisocyanate, and in addition this latter elastomer exhibits more crystallinity, as shown by the large endotherm in the specific heat measurement. The structure of the diisocyanate naturally changes the behavior of the hard segment.
Polymerization and processability of poly(vinyl chloride),
Authors: Deanin Rudolph D. , Somers Roger E. 
Published: April 2003

AbstractThe processability of rigid poly(vinyl chloride) can be improved by adding trichloroethylene as chain‐transfer agent, increasing the polymerization temperature, and especially by combining the two effects together. The resulting synergistic interaction is best expressed by an equation of the form, P = (A + B[TCE])eC/T, where P is thermal plasticity, AeC/T is the combined effect of chain transfer to initiator and monomer and termination through combination and disproportionation, and B[TCE]eC/T represents the chain‐transfer action of trichloroethylene.
Radical polymerizations and copolymerizations of dimethylstannyl dimethacrylate and trimethylstannyl methacrylate
Authors: Yamada Bunichiro , Yoneno Hiroshi , Otsu Takayuki 
Published: April 2003

AbstractThe radical polymerizations and copolymerizations of dimethylstannyl dimethacrylate (DSM) and trimethylstannyl methacrylate (TSM) in dimethylformamide (DMF) were studied. These monomers did not polymerize thermally, but easily underwent polymerization in the presence of α,α′‐azobisisobutyronitrile and on irradiation with ultraviolet light. The polymer obtained from TSM was soluble in DMF and methanol, but that from DSM was insoluble in any organic solvents; this polymer probably consists of a network structure. These polymers were converted to poly(methyl methacrylate) (PMMA) by means of acid hydrolysis and then methylation with diazomethane. The content of syndiotactic triad was determined from infrared spectra of PMMA derived from the polymers of DSM and TSM. It was noted that the content of syndiotactic triad was greater in the radical polymerization of TSM than those of DSM at every temperature investigated. The differences in the activation enthalpy (ΔΔH‡) and in the activation entropy (ΔΔS‡) between isotactic and syndiotactic additions were determined as follows: for DSM, ΔΔH‡ = ∼0 cal/mole, ΔΔS‡ = −0.856 eu; for TSM, ΔΔH‡ = 229 cal/mole, ΔΔ = −1.09 eu. From the radical copolymerizations of DSM and TSM with styrene at 60°C, the copolymerization parameters, Q and e, were evaluated as follows: for DSM, Q = 1.36, e = 0.41; for TSM, Q = 0.45, e = −0.37. These results were compared with the reported effects of stannic chloride and zinc chloride on the radical polymerization of methyl methacrylate.
Polyarylsulfones, synthesis and properties,
Authors: Vogel H. A. 
Published: April 2003

AbstractA new class of high molecular weight polyarylsulfones is described. Polymer synthesis and structure–property relationships are discussed. The polymers are prepared by Friedel‐Crafts type polycondensation of aromatic sulfonyl chlorides with aromatic hydrocarbons. A number of Lewis acids in small quantities are useful as catalysts for the polymerization. The polymerization reaction is carried out at elevated temperatures in the melt or in solution. Inert, nonbasic solvents which are compatible with the Lewis acid catalysts such as nitrobenzene and dimethyl sulfone are useful for conducting the polymerization. Many of the polyarylsulfones are amorphous, rigid thermoplastics with unusually high softening points, having glass transition temperatures in the range of 200–350°C. Outstanding resistance to air oxidation at high temperatures is derived from incorporation of the deactivating sulfone groups in the aromatic polymer backbone. Melt stability and solubility in selected solvents are emphasized as basis for processibility by conventional solution casting and molding techniques. The combination of properties, which in addition to thermal stability includes a high level of mechanical and electrical properties, chemical inertness, and hydrolysis resistance makes these new arylsulfone polymers useful over a wide temperature range and in severe and corrosive environments.
Synthesis and polymerization studies of 1,2‐dimethyleneoctafluorocyclohexane
Authors: Blomquist A. T. , Durandetta Donald W. , Robinson Gordon B. 
Published: April 2003

Abstract1,2‐Dimethyleneoctafluorocyclohexane has been prepared by the pyrolysis of 2‐chloro‐methyl‐1‐methyloctafluorocyclohexane. Free radicals initiate the polymerization of the diene in both bulk and emulsion systems to give a highly crystalline (mp 214–218°C) polymer that has an all‐cis 1,4‐structure. The polymer is insoluble in common laboratory solvents, but will dissolve in perfluorokerosene above 175°C and in 2,5‐dichlorobenzo‐trifluoride above 150°C. This diene is not polymerized by cationic, anionic, or Ziegler‐Natta catalysts. The diene is readily copolymerized with many common monomers to give soluble, high molecular weight polymers. Relative reactivity ratios have been measured with styrene by the Fineman and Ross method and Q–e parameters for the diene have been calculated.
Cyclopolymerization: Cyclization of diallylcyanamide to pyrrolidine derivatives
Authors: Brace Neal O. 
Published: April 2003

AbstractFree‐radical addition of perfluoroalkyl iodides (RFI) to diallylcyanamide gave cis‐ and trans‐1‐cyano‐3‐iodomethyl‐4‐(perfluoroalkyl)methylpyrrolidine (Ia,b). Five‐membered ring products were preferentially formed in this reaction by other 1,6‐dienes having terminal vinyl groups. This strongly suggests that cyclopolymerization of such monomers occurs in analogous fashion, instead of leading to 6‐membered rings as has been previously understood. Dehydrohalogenation of Ia,b gave 3‐methylenepyrrolidine derivatives as expected. Infrared and NMR spectra clearly show the exocyclic CH2 group. The influence of reaction conditions on the yield of cyclization product Ia,b and certain side products was investigated.
Quaternary ammonium and sulfonium derivatives of 2‐chloromethylbutadiene and poly‐2‐chloromethylbutadiene
Authors: Jones Giffin D. , Meyer W. C. , Tefertiller N. B. , MacWilliams D. C. 
Published: April 2003

Abstract2‐Chloromethylbutadiene has been converted to quaternary ammonium and sulfonium monomers which have been polymerized at room temperature. They show a very great tendency to dimerize on heating in water solution. The aqueous quaternary monomer dimerized 25 times as fast as the aqueous sulfonium monomer and nearly 105 times as fast as neat isoprene at 50°C. The quaternary monomer dimerized with itself in a water solution to which 2‐hydroxymethylbutadiene has been added as an example of a nonionic diene. The latter monomer did not dimerize rapidly in water, nor did 2‐aminomethylbutadiene. The hydrochlorides of 2‐aminomethylbutadiene and 2‐dimethylaminomethylbutadiene dimerized at rates comparable to that of the sulfonium monomer. Poly 2‐chloromethylbutadiene contains reactive chlorine except for the structure resulting from the minor extent of 1,2 addition. Water‐soluble derivatives have been made from it with nucleophilic tertiary amines and sulfides. Cationic polymers are substantive to paper pulp, and the sulfonium polymers can be cured in paper to give improved wet strength.
Design of active‐site‐directed fluorescent probes and their reactions with biopolymers
Authors: Himel Chester M. , Mayer Richard T. , Cook Larry L. 
Published: April 2003

AbstractFluorescent probes which are active‐site‐directed, reversible, competitive inhibitors of serum cholinesterase (ChE) enzymes have been designed and synthesized. Reversible inhibitors of enzyme active sites have a unique importance when they act as fluorescent probes, allowing fluorescence spectroscopic detection of conformation changes and activesite dynamics. 5‐Dimethylamino‐naphthalene‐1‐sulfonamido‐N,N‐dimethyl‐n‐propyl‐amine and its aliphatic quaternary derivative are fluorescent probes for serum cholinesterase. The quaternary probe forms complexes with acetylcholinesterase (AChE). The dissociation constants Kd for the two probes with serum ChE are 6.0 × 10−7 and 6.5 × 10−7M. The inhibition constants Ki are 3.1 × 10−6 and 6.3 × 10−6M from the slopes of Lineweaver‐Burk plots. The Michelis constant Km for the enzyme was 8.8 × 10−4M.
Preparation of some new polybenzimidazoquinazolines
Authors: Saga M. , Hachihama M. , Shono T. 
Published: April 2003

AbstractSeveral new types of polybenzimidazoquinazolines with a different recurring unit have been prepared by solution polycondensation in polyphosphoric acid followed by heating at elevated temperature under reduced pressure. The polymers thus obtained were light yellow to brown powdery materials hardly soluble in common organic solvents and soluble in concentrated sulfuric acid. The inherent viscosity of the polymers ranged from 0.1 to 0.58 and showed good thermal stability.
An optically active vinyl sulfoxide copolymer and the configuration of sulfoxide adjacent to radical or anionic sites
Authors: Mulvaney J. E. , Ottaviani R. A. 
Published: April 2003

AbstractOptically active vinyl p‐tolyl sulfoxide was synthesized and copolymerized with styrene to produce an optically active copolymer. The question of the configuration of sulfur in a sulfoxide when adjacent to a radical site is discussed. The configuration of sulfur in a sulfoxide is proven to be nonplanar when adjacent to an anionic site.
Glass transformation temperatures of polymers of olefin oxides and olefin sulfides
Authors: Lai Joginder , Trick G. S. 
Published: April 2003

AbstractA number of polymers belonging to poly(olefin oxide) and poly(olefin sulfide) series have been prepared and their glass transformation temperatures determined by dilatometry and differential thermal analysis. In the poly(olefin oxide) series, theTgremained practically unchanged as the length of the pendent alkyl group was increased from methyl ton‐hexyl. However, a 20°C decrease inTgwas observed when the pendent group was changed from ethoxymethyl ton‐hexoxymethyl. In the poly‐(olefin sulfide) series, theTgvalue decreased as the pendent alkyl group changes from methyl to ethyl. Replacement of ether oxygen in the polymer main chain by sulfide sulfur increased theTgvalue. In some polymers, first‐order transitions were observed, but their significance has not been assessed.
Electron spin resonance study on polymerization of conjugated dienes by homogeneous catalyst derived from n‐butyl titanate and triethylaluminum
Authors: Hirai Hidefumi , Hiraki Katsuma , Noguchi Isamu , Inoue Takeo , Makishima Shoji 
Published: April 2003

AbstractPolymerizations of butadiene, penta‐1,3‐diene, and isoprene with n‐butyl titanate–triethylaluminum catalyst are examined by ESR measurements on the polymerization state. At Al/Ti molar ratios greater than 2.9 where the conjugated dienes are polymerized, the polymerization system of butadiene always gives an ESR signal with a g value of 1.983 and with a hyperfine structure of about 19 components. This signal does not appear at all, even in the presence of the monomer, at Al/Ti molar ratios smaller than two where butadiene is not polymerized. The absorption intensity of the signal coincides fairly well with the concentration of polymer chain calculated from polymer yield and the molecular weight. On the basis of these facts, the signal is assigned to the growing end of polybutadiene with this catalyst. The structure of the growing end is proposed to have both two substituted π‐allyl groups and an alkoxy group in coordination to titanium (III), by analysis of the hyperfine structure. The polymerization system of penta‐1,3‐diene and that of isoprene respectively, give a new signal with a g value of 1.983, although the signal for the former monomer has a hyperfine structure of 11 components and that for the latter monomer has no hyperfine structure. A structure for the growing end in the polymerization of each of these two monomers analogous to that of the growing end of polybutadiene is proposed.
Polyhydrazides. IV. Preparation and properties of poly‐N‐ethyl‐ and isopropylhydrazide oxadiazoles
Authors: Iwakura Yoshio , Uno Keikichi , Kurosawa Shigeru 
Published: April 2003

AbstractHigh molecular weight poly‐N‐alkylhydrazide‐oxadiazoles have been prepared in poly‐phosphoric acid by alkylation of poly‐1,3,4‐oxadiazole which was synthesized from terephthalic acid and hydrazine sulfate. Various kinds of reagents having an alkoxy group were used as alkylating agent, and N‐ethylated and N‐propylated polyhydrazides containing oxadiazole units were obtained. The thermal properties of the polymers obtained were investigated by using infrared spectroscopy, viscometry, differential thermometric and thermogravimetric techniques. Soluble poly‐N‐alkylhydrazide‐oxadiazole are thermally cyclized to poly‐1,3,4‐oxadiazole with elimination of olefins and water at 226–330°C for propylated polydrazide and at 240–360°C for ethylated polyhydrazide. For both, weight loss in polyhydrazides occurs in two distinct stages corresponding, respectively, to cyclization and decomposition of the poly‐1,3,4‐oxadiazole formed in situ.
Chain transfer with siloxanes during free‐radical polymerization
Authors: Saam John C. , Gordon David J. 
Published: April 2003

AbstractChain transfer constants (Cs) for a number of substrates containing the silicon‐oxygen bond are measured in polymerizing methyl methacrylate. Additionally, a few measurements are run in styrene in order to estimate the influence of polar factors on chain transfer. The methylsiloxanes studied all show very low values of Cs (10−5 to 10−6). The chain transfer constants of a number of propylsiloxane derivatives are negligibly influenced by the presence of silicon. Thus, (Me3SiO)2MeSiCH2MeCH(C6H5) shows a value of Cs nearly that reported for cumene, and (MeO)3SiCH2CH2CH2SH shows values of Cs close to those reported for alkyl mercaptans.
Polymerization of unsaturated episulfides
Authors: Lautenschlaeger F. , Schnecko H. 
Published: April 2003

AbstractThe polymerization of four unsaturated episulfides, vinylthiirane, endo‐2,3‐thioepoxy‐norbornene, cyclooctadiene‐1,5‐monoepisulfide and allyloxymethylthiirane can be affected by various ionic catalysts, BuLi, ZnEt2.H2O, BF3.Et2O, etc. In case of conjugated functional groups, some catalysts afford isomeric structures resulting from participation of both the olefinic and the episulfide group; the latter can also be opened separately, but even for radical initiation of vinylthiirane no 1,2‐structure of a pure vinyl polymer was obtained. A rearrangement of 1,3‐ to 1,5‐polymer has been observed in some cases by post treatment.
Treatments of cross‐termination rate constants in radical copolymerization
Authors: Ito Katsukiyo 
Published: April 2003

AbstractIn copolymerization, Arlman's equation was modified towherektabis an apparent cross‐termination rate constant depending on a ratiof1= [A]/[B], andKz(x= 1, 2, 3, 4) is the ratio of each cross‐termination rate constant depending on the penultimate unit to the geometric meanK̄tabof two termination rate constants in homopolymerizations. The calculated values of (K1+K2/r1r2) by using this equation were related toK1+K2/r1r2= 18/r1r2.
Étude de la cotacticité des copolymères acrylonitrile‐méthacrylate de methyle par resonance magnetique nucléaire—haute resolution
Authors: Pham‐Quang‐Tho  , Guillot Jean 
Published: April 2003

AbstractA study of the NMR spectra of acrylonitrile–methyl methacrylate copolymers (PAM) with very low percentages of methyl methacrylate (M) allows quantitative determinations of AMA, and MMA or AMM triad sequences from the methoxy resonances. The resolution of the complex α‐methyl resonances of the isolated M units in seven components has been attempted. If our assignments are correct, the analysis of the cotactic pentad sequences (with a M in central position) has revealed that the configurations of the copolymer chain do not follow the Bernouillian or the first‐order Markoffian statistics.
Mechanism of the thermal stabilization of poly(vinyl chloride) with metal carboxylates and epoxy plasticizers
Authors: Anderson Donald F. , McKenzie D. A. 
Published: April 2003

AbstractThe chemical reactions responsible for the retardation of thermal discoloration in poly(vinyl chloride) (PVC) stabilized with a combination of an epoxy plasticizer and a heavy metal soap mixture of Group IIa and IIb metals have been studied. Allylic chlorides (a mixture of 4‐chlorohexene‐2 and 2‐chlorohexene‐3) are used as prototypes for the degrading segment of the polymer chain. The results confirm earlier reports that, when a mixture of a covalent and ionic metal soap is used as the stabilizer, the covalent moiety (e.g., Cd and Zn soaps) functions to esterify the allylic site of the degrading PVC model. A synergistic effect displayed by the ionic soap (e.g., Ca or Ba) is caused by a transfer of carboxylate ligands from the ionic soap to the depleting covalent species, which has been largely converted to the corresponding chloride. When an epoxy plasticizer model (cyclohexene oxide) is used in conjunction with the metal soap stabilizer, the preferred reaction is esterification. After a considerable build‐up of ester, an α‐chloroether, 2‐hexenyl 4‐(2‐chlorocyclohexyl) ether, is formed by the reaction of cyclohexene oxide with the PVC model. This reaction was found to be catalyzed by cadmium chloride. The esterification and etherification reactions provide an explanation for the synergism observed in the stabilization of PVC containing a combination of an epoxy plasticizer with a covalent and an ionic metal soap.
Relationship between membrane potential and electrolyte uptake by ion‐exchange membranes
Authors: Lakshminarayanaiah N. , Siddiqi Fasih A. 
Published: April 2003

AbstractElectrical potentials arising across three cation‐selective membranes of low water content when they separate solutions of different concentration of the same NaCl electrolyte have been measured at 25°C. Also, electrolyte uptake by these membranes when they are in equilibrium with different solutions of NaCl has been estimated. These data together with the apparent membrane transport number derived from membrane potential have been used to check a simple relation given by Lakshminarayanaih.
Mobility of the ring structure and the characteristics of crosslinked polymers: The structural effect of the eleven‐membered ring and its homologs upon the dynamic mechanical properties and glass transition temperature of crosslinked diallyl succinate polymers
Authors: Isaoka Shinichi , Mori Makihiko , Mori Akio , Kumanotani Ju 
Published: April 2003

AbstractDynamic mechanical properties and glass transition temperatures were measured for crosslinked polymers derived from diallyl succinate monomers. The mobility of the diester having an eleven‐membered ring and of homologous structures which are introduced in the crosslinked polymer system, is discussed on the basis of the parameter for cyclization polymerization of a monomer, dynamic mechanical properties, and glass transition temperature. Control of the mobility of the ring structure and its homologous structures involved in the crosslinked polymers was attempted by modification of the substituent at the 1‐ or 1,2‐position of diallyl succinate, and the diallyl succinate monomers were derived from the succinic acid and its derivatives: succinic acid, methyl succinic, ethyl succinic, and chlorosuccinic acids; cis‐1,2‐dicarboxylic acids of cyclopropane, cyclobutane, cyclopentane, and cyclohexane; cis‐1,3‐ and 1,4‐dicarboxylic acids of cyclohexane, and phthalic acid. The results obtained are explained well on the basis of the mobility of the ring and homologous structures.
Influence of mass transfer at the monomer‐water interface on polymerization emulsion
Authors: Nikitina S. A. , Spiridonova V. A. , Taubmann A. B. 
Published: April 2003

AbstractA quasi‐spontaneous process of mass transfer takes place at the interface of a monomer and water in the presence of surface‐active substances soluble in both phases as a result of their diffusion through the interfacial boundary. This process is accompanied by the formation of a microemulsion whose particle size depends on the emulsifier concentration and its molecular structure. While investigating various nonionic surface‐active substances as emulsifiers in the emulsion polymerization of vinyl acetate, it was established that polymerization occurs in droplets of the monomer microemulsion in water, which are formed as a result of mass transfer at the interface.
Investigation of the mechanism of chlorination of poly(vinyl chloride) as influenced by chain microstructure
Authors: Allen V. R. , Young R. D. 
Published: April 2003

AbstractSamples of poly(vinyl chloride) polymerized at different temperatures (+30, 0, −30, and −78°C) and a commercial sample were chlorinated by a photoinitiated, free‐radical method in o‐dichlorobenzene at ambient temperature. The chlorine content was determined by difference by using a carbon‐hydrogen analyzer. High‐resolution infrared analysis revealed a selective attack on the methylene hydrogens along with a concomitant decrease in intensity of the isotactic methylene deformation band and the syndiotactic carbon‐chlorine stretching band. Graphical representation of the relative intensities of the v(CH), δ(CH2), and v(CCI) modes indicate that the chlorine radical preferentially attacks the middle carbon of the heterotactic triad. The increased “stiffness” of this unit causes the rotational energy of the system to be transferred to the syndiotactic portion of the chain. It is proposed that this additional energy causes the TTTT conformer of the syndiotactic unit to rotate into the less‐preferred TTGG conformation, which would be more reactive. Facile chlorination of this latter conformer is predicted. This mechanism is in accord with the reported equilibrium composition of the different conformers.
Effects of substituents on the anionic copolymerization of ring‐substituted cinnamonitriles
Authors: Kobuke Yoshiaki , Fukui Yoshio , Furukawa Junji , Fueno Takayuki 
Published: April 2003

Abstracttrans‐Cinnamonitrile (M1) was copolymerized with several of its ring‐substituted derivatives (M2) in toluene at 25°C, calcium zinc tetraethyl being used as catalyst. The ring substituents investigated include H,p‐CH3O,m‐CH3O,p‐CH3,m‐CH3,p‐Cl, andm‐Cl. It was found that the values of log (1/r1) are linearly correlated with Hammett's σ constants with the reaction constant σ ρ 0.7. The effects of coordination between monomer and catalyst sites upon the Hammett relation are discussed.