bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally reversible polymer systems by cyclopentadienylation. II. The synthesis of cyclopentadiene‐containing polymers
Authors: Kennedy Joseph P. , Castner Kenneth F. 
Published: April 2003

AbstractThe synthesis of polymers containing either terminal or pendant cyclopentadiene (CPD) groups has been studied. Using information obtained from model studies, the synthesis of polyisobutylenes containing a CPD terminus was accomplished by the use of the tert‐butylchloride–dimethylcyclopentadienylaluminum initiator system. Isobutylene polymerization by this system under carefully chosen conditions is essentially transfer free, and termination occurs by cyciopentadienylation. The presence of CPD end group has been established by UV spectroscopy and reaction with maleic anhydride. Selectivity toward termination by cyclopentadienylation increases with decreasing temperatures; at −41°C and low conversion (<10%) ca. 72% of the polymer chains terminate in this manner. The synthesis of polymers containing randomly distributed pendant CPD groups along the chain has been accomplished by cyclopentadienylating with dimethylcyclopentadienylaluminum chlorobutyl rubber and chlorinated poly(ethylene‐co‐propylene) (Cl‐EPM). Pendant CPD groups undergo Diels‐Alder/retro‐Diels‐Alder condensations yielding thermally reversible networks; e.g., a cyclopentadienylated Cl‐EPM was remolded three times to elastic sheets.
Factors affecting electrical conductivity of carbon black‐loaded rubber. II. Effect of concentration and type of carbon black on electrical conductivity of SBR
Authors: Abdel‐Bary E. M. , Amin M. , Hassan H. H. 
Published: April 2003

AbstractEffect of the concentration of four types of carbon black, namely, HAF, FEF, ISAF and GPF, on the electrical conductivity of SBR (1502) was studied. The anomalous behavior of conductivity [σmin in σ(T) curves] becomes more pronounced as we approach a characteristic value of carbon concentration, F0, at which maximum anomaly occurs; F0 was found to depend on the type of carbon black. Moreover, the depth of the valley shape of the σ(T) curve increases with the particle size of carbon black used.
Statistical approach to the molecular weight distribution of condensation polymers
Authors: Orlova T. M. , Pavlova S.‐S. A. , Dubrovina L. V. 
Published: April 2003

AbstractA mathematical linear polycondensation model in which the probability of bond formation depends on its index number and the limitation of molecular propagation were considered has been proposed. From this model a three‐parameter function of macromolecular weight distribution and degree of polymerization distribution of the macromolecules have been derived. Under certain conditions less common one‐ and two‐parameter functions can result. Two‐ and three‐parameter functions have been used in the description of experimental molecular weight distribution of polyarylate samples prepared under different conditions of synthesis. Theoretical functions conform to experimental data.
On the glass transition temperature of comblike polymers: Effects of side chain length and backbone chain structure
Authors: Reimschuessel H. K. 
Published: April 2003

AbstractPolymers composed of monomer units that contain n‐alkyl side chains are characterized by a monotonical decrease in the glass transition temperatures toward a critical value (Tg)c as the number of C atoms in the side chain increases toward a corresponding critical value nc. Thus the glass transition temperatures of these comblike polymers are for a given backbone chain structure directly related to the molecular weight (M) of the monomer unit. This relationship can be represented by the differential equation dTg/dM = −k′M[Tg − (Tg)c], which on integration yields Tg = (ΔTg)0 exp−[k(M2 − M)] + (Tg)c, where (ΔTg) = (Tg)1 − (Tg)c, and the subscript 1 refers to n = 1. Values for Tg calculated according to this relationship are in good agreement with published data on polybutadienes, polystyrenes, poly(vinyl ether)s, polyacrylates, polymethacrylates, polyitaconates, poly(phenylene ether)s, and poly(N‐maleimide)s. For these polymers the critical quantities nc and (Tg)c can be estimated rather well by the simple relationships nc = 1 + 2.8 × 10−2 (Tg)1 and (Tg)c = (Tg)1 − nc(nc − 1). The Tg(M) relationship derived appears to be applicable also to copolymers that contain monomer units with alkyl side chains.
Criteria for diffusion limitation in coordination polymerization
Authors: Chien James C. W. 
Published: April 2003

AbstractThe following criteria are proposed to judge whether a coordination polymerization may be diffusion controlled or not: (1) If the number‐average molecular weight and polydispersity of the polymer calculated from kinetic rate constants as a function of time agree with the experimental values, the polymerization is not diffusion controlled. (2) The polymerization may be diffusion controlled if the Thiele modulus, the ratio of the characteristic diffusion time to the characteristic reaction time, is much greater than unity; if it is much smaller than unity, the polymerization is reaction controlled. (3) If an initial linear dependence of rate of polymerization on catalyst concentration changes over to a square‐root dependence, the polymerization may be diffusion limited. (4) The polymerization is likely to be diffusion limited if the instantaneous rate of polymerization is proportional to the rate of particle growth when the proportionality coefficient is the surface area of the particle. Criterion (1) is a necessary and sufficient condition as stated, as its converse is not true. All the other criteria are merely necessary but not sufficient conditions. The established Ziegler–Natta catalysts have activities too low to cause diffusion limitation; the Phillips catalyst system is likely to be diffusion limited. The polydispersity of polyolefins produced with Ziegler–Natta catalysts are not the consequence of diffusion control but are the characteristics of the catalysts in their kinetics of initiation, propagation, chain transfer, and termination.
Vibrational spectra and IR dichroism of poly(tetramethyl‐p‐silphenylene‐siloxane) and its chain structure
Authors: Dobos S. , Zelei B. 
Published: April 2003

AbstractRaman spectra of poly(tetramethyl‐p‐silphenylene‐siloxane) were investigated in solution with depolarization ratios and in the solid state. Polarized infrared (IR) spectra were studied on oriented polymer samples. Assignments of the vibrational bands are given and IR dichroic and Raman data are in agreement with tetragonal P41 space group symmetry. These data provide information on the arrangement of the SiC6H4Si groups in the unit cell. On the basis of vibrational spectra the dynamic interaction between adjacent benzene rings is negligibly small and the rings preserve their local D2h Pseudosymmetry.
Polymerization of acrolein and methyl vinyl ketone induced by amine–water and pyridine–phenol systems
Authors: Yamashita Natsuki , Inoue Hiroshi , Maeshima Toshihisa 
Published: April 2003

AbstractIt was reported that acrolein (AL) in tetrahydrofuran (THF) polymerizes at temperatures below 0°C in the presence of pyridine (Py) and water. To clarify this polymerization mechanism the polymerization of AL and methyl vinyl ketone (MVK) by an initiation system such as Py–water, triethylamine (Et3N)–water, or Py–phenol(Ph) was carried out. The polymerization rate (Rp) of MVK in the Et3N–water system was expressed by the same equation, Rp = k [Et3N] [H2O] [MVK]2, used for AL in the Py–water system. Meanwhile, β‐hydroxypropionaldehyde, β‐phenoxypropionaldehyde, γ‐ketobutanol, and β‐phenoxy‐1‐methylpropionketone were obtained as the initial addition products. The polymer of AL obtained was composed of polymer units of vinyl and aldehyde polymerization, but the structure of MVK polymer obtained by the Py–water system was composed of only vinyl polymerization units. The polymerization of MVK by the Py–Ph system did not occur, however. These results were discussed in terms of the initiation and propagation mechanisms.
Anionic block copolymerization of ϵ‐caprolactam
Authors: Petit D. , Jerome R. , Teyssie Ph. 
Published: April 2003

Abstractϵ‐Caprolactam anionic homopolymerization was studied in the presence of different model activators. On the basis of the results ester‐ and isocyanate‐terminated polymers were used as macroactivators and nylon‐6–polyvinyl or polydiene block copolymers were synthesized in high yields. The physical properties and morphology of a nylon–polybutadiene triblock copolymer were characterized.
Syntheses of polymerizable viologens bearing a terminal vinyl group
Authors: Kamogawa Hiroyoshi , Mizuno Hideyuki , Todo Yasuto , Nanasawa Masato 
Published: April 2003

AbstractViologens that bore a terminal vinyl group were synthesized by four sequences of reactions: (1) N‐vinylbenzyl‐N′‐n‐propyl‐4,4′‐bipyridinium bromide chloride (V) was synthesized by the reaction of 4‐(4′‐pyrodyl)‐N‐n‐propyl pyridinium bromide (III) with vinylbenzyl chloride; (2) N‐β‐acrylamidoethyl‐N′‐n‐propyl‐4,4′‐bipyridinium dibromide (IX) was synthesized by the Menschutkin reaction of III with 2‐aminoethyl bromide hydrobromide and subsequent reaction with acryloyl chloride; (3) N‐β‐methacryloyloxyethyl‐N′‐n‐propyl‐4,4′‐bipyridinium dibromide and its analogs (XI) were synthesized by the reactions of III with the corresponding acyloxyalkyl bromides; and (4) N‐vinyloxycarbonylmethyl‐N′‐n‐propyl‐4,4′‐bipyridinium bromide chloride (XIII) was synthesized by the reaction of III with vinyl chloroacetate. With the exception of monomer XIII in which hydrolysis in large extent was observed during attempted polymerization, the synthesized monomers polymerized smoothly in aqueous solutions by a conventional radical procedure. Comparisons of the absorption peaks of the radical cations produced by reductions in aqueous solutions with those produced in films by ultraviolet (UV) irradiation indicate that the radical cations of polymers are associated intramolecularly in aqueous solutions.
Polymerizations of substituted cyclopropanes. II. Anionic polymerization of 1,1‐disubstituted 2‐vinylcyclopropanes
Authors: Cho Iwhan , Ahn Kwang‐Duk 
Published: April 2003

AbstractAmong the four 1,1‐disubstituted 2‐vinylcyclopropanes, diethyl 2‐vinylcyclopropane‐1,1‐dicarboxylate (Ia), 2‐vinylcyclopropane‐1,1‐dicarbonitrile (Ib), ethyl 1‐cyano‐2‐vinylcyclopropanecarboxylate (Ic), and 1,1‐diphenyl‐2‐vinylcyclopropane (Id), Ib and Ic polymerized well with sodium cyanide in N,N‐dimethylformamide. Ib was most reactive and a polymer (IIb) from Ib exhibited an inherent viscosity of 1.05 dl/g (concentration of 1.0 g in 100 ml of 95% H2SO4). All experimental results indicated that the polymerization proceeded by ring opening and that the structure of the polymers had pendant vinyl groups. The polymer IIc from Ic was soluble in common solvents like acetone, but IIb was soluble only in 95% H2SO4. Reactions of those compounds with benzenethiolate ion in ethanol yielded addition products that supported the ring‐opening polymerization of those monomers. In the postulated mechanism of polymerization cyanide ion attacks the carbon of a cyclopropane ring with electron‐releasing vinyl group and the resulting anion is thereby stabilized by two electron‐withdrawing substituents. The propagation takes place by the reaction of the anion with another monomer molecule.
Melamine–formaldehyde resins: Constitutional characterization by fourier transform 13C‐NMR spectroscopy
Authors: Tomita Bunichiro , Ono Hirokuni 
Published: April 2003

AbstractThe random chemical structures of melamine–formaldehyde resins, including methylated melamine–formaldehyde resins and urea–melamine formaldehyde resins, were investigated by 13C‐NMR spectroscopy (Fourier transform). All the combined formaldehydes, methylol and methyl ether groups, methylene structures, and dimethylene ether structures were assigned. A 13C chemical shift of methylene carbon occurred by substitution of other constituents of the methylene group for a proton of the adjacent monosubstituted nitrogen atom, as shown in a 13C‐NMR spectrum of urea–formaldehyde resins. It was found that the chemical shift of each corresponding carbon of both melamine resins and urea–melamine resins was almost superimposed with that of urea resins.
Copolymers of 2‐hydroxyethyl methacrylate and alkyl acrylates: Studies of molecular weight distribution and thermal behavior
Authors: Varma I. K. , Patnaik S. 
Published: April 2003

AbstractSeveral copolymers of 2‐hydroxyethyl methacrylate (HEMA) with methyl acrylate (MA), ethyl acrylate (EA), n‐butyl acrylate (BA), and methyl methacrylate (MMA) were prepared at 70°C in nitrogen atmosphere using 0.2% (w/v) benzoyl peroxide as initiator. The copolymer composition was evaluated by estimation of hydroxyl group in the copolymers. Intrinsic viscosity of HEMA–EA, HEMA–BA, and HEMA–MMA copolymers was determined at 35°C in dimethyl formamide. Molecular weight distribution of copolymer samples was evaluated by gel permeation chromatography. Thermal behavior of the copolymers was investigated by dynamic thermogravimetry. Thermal stability decreased on increasing HEMA content in MA, EA, and BA copolymers. However, a reverse trend was observed in HEMA–MMA copolymers.
Photoinitiated radical chains in solid polymeric methacrylates
Authors: Egerton P. L. , Reiser A. , Shaw W. , Wagner H. M. 
Published: April 2003

AbstractPolymeric methacrylates functionalized with free methacryloyl groups are efficiently crosslinked in the presence of transition‐metal carbonyls on UV irradiation of the polymeric solid. The reaction proceeds by a radical chain mechanism with a kinetic chain length of about 10 in a solvent‐free polymer containing 10−3 mole of methacryloyl groups per cm3. The chain length increases steeply when the glass transition of the polymer is reached, either by plastification or by an increase in temperature. The temperature dependence of the crosslinking yield below the glass transition is consistent with an activation energy of about 9 kcal mole−1. The addition of acrylic monomers enhances chain propagation by up to an order of magnitude. Postirradiative crosslinking in the matrix comes to a standstill well before all acrylic groups or radicals have been exhausted: if, after cessation of the primary reaction, the matrix is briefly heated, a second crop of crosslinks is obtained without further exposure. The system behaves thus as if the radicals had been removed into traps from which they can be set free by thermal activation. From an analysis of the reaction kinetics it appears that in the glassy polymer 90% of the radicals are inactivated in this way. Radical recombination, however, is the principal mechanism of chain termination above the glass transition. From the kinetic data, diffusion coefficients for polymer‐bound groups are found to be in the range of 10−17–10−16 cm2 sec−1 in the glassy polymer at room temperature. They are of the order of 10−14 cm2 sec−1 in plasticized films above the glass transition.
Trifunctional polycondensation: A cumulative distribution function
Authors: Stafford J. W. 
Published: April 2003

AbstractA trifunctional polycondensation, cumulative‐weight‐fraction distribution function has been derived. The equation is exact and yields cumulative‐weight fractions that are the same as those calculated by summation of the differential distribution function. The cumulative distribution function still contains factorials, which renders computation difficult for high values of i. The cumulative distribution function is derived in a form that allows inferences to be drawn on whether mass is conserved past an extent of reaction of p = 0.5 or whether a material loss to what is considered a gel phase occurs. The inferences that can be drawn indicate that mass is conserved up to p = 1. The discrepancy between this finding and the requirements of the Flory gel–sol theory are discussed.
Kinetics of styrene polymerization at ultrahigh conversion
Authors: Kwant P. W. 
Published: April 2003

AbstractThe radical‐initiated bulk polymerization of styrene at low conversion can be adequately described by a simple kinetic scheme that involves initiation by the decomposition of a radical initiator, propagation, and termination by combination of polystyryl radicals. An integrated equation can be derived that will describe the relationship between monomer concentration and time. We have investigated the validity of applying equations of this kind in the 98–99.999% conversion range. From our experimental work we conclude that the initial rates at 130°C, when starting the polymerization at that temperature at more than 98% conversion, can be described by an integrated equation over at least two decades of monomer concentration. Deviations from the simple kinetics at ultrahigh conversion were observed after a certain time at 130°C. These are discussed and explained in terms of the kinetic assumptions made and an extended model is suggested to allow for depolymerization reactions that cannot be neglected at ultrahigh conversion.
Methods of acrolein polymerization and investigation of structures of the polymers obtained
Authors: Andreeva I. V. , Artemyeva V. N. , Nesterov V. V. , Kukarkina N. V. 
Published: April 2003

AbstractTwo methods for the polymerization of acrolein are proposed: suspension polymerization in water with the redox system K2S2O8:AgNO3 = 1:0.1 with respect to the monomer and a static method with the system K2S2O8:PA–SO2 adduct. The dependencies of yield, molecular weight, and structure of polyacrolein under investigation on the following factors: the amount and the ratio of the initiator components, the pH of the medium, and the monomer:solvent ratio were investigated. The structure of polyacrolein was studied by infrared spectroscopy, thermogravimetric analysis, and chemical functional analysis. The molecular weight distribution of samples of static and suspension polyacroleins modified under identical conditions was determined by gel permeation chromatography.
Stereoregularity of poly(α‐methylvinyl alkyl ether)s determined by 1H‐ and 13C‐NMR spectroscopy
Authors: Matsuzaki Kei , Okuzono Shuichi , Kanai Taiichi 
Published: April 2003

Abstractα‐Methylvinyl methyl ether, ethyl ether, and isobutyl ether were polymerized under various polymerization conditions and the structure of the polymers was determined by 1H‐ and 13C‐NMR spectroscopy. α‐Methyl and β‐methylene carbon spectra of poly(α‐methylvinyl isobutyl ether) showed splitting and were analyzed by triad and tetrad sequences. β‐Methylene carbon spectra of poly(α‐methylvinyl ethyl ether) also showed splitting. When Eu(fod)3 was added, α‐methyl and methoxy proton spectra in benzene of poly(α‐methylvinyl methyl ether) showed splitting assigned to triad tacticities. All the polymers obtained in polar solvents exhibited an increase in syndiotacticity. The polymerization mechanism is discussed.
Coupling of acrylic polymers and collagen by use of a water‐soluble carbodiimide. II. Investigations of the coupling mechanism
Authors: Lloyd Douglas R. , Burns Charles M. 
Published: April 2003

AbstractThe coupling mechanism involved in the coupling of acrylic polymers and collagen by a water‐soluble carbodiimide was investigated. By the use of a series of homopolymers of α‐amino acids, support was given to the postulate that a major proportion of the coupling takes place in the amino functional group. In light of the results presented the reaction is sterically controlled and the steric, stoichiometric, and kinetic aspects of the reaction are discussed.
Aromatic polyamides. IV. A novel synthesis of sulfonated poly(para‐phenyleneterephthalamide): Polymerization of terephthalic acid and para‐phenylenediamine in sulfur trioxide
Authors: Silver Frank M. 
Published: April 2003

AbstractA novel polyamide condensation reaction of aromatic diamines (usually as strong inorganic acid salts) and aromatic diacids in SO3 has been discovered. para‐Phenylenediamine was polymerized with terephthalic acid in SO3 at 20–47% polymer concentration to form highly anisotropic (liquid crystalline) sulfonated poly(p‐phenyleneterephthalamide) (SPT) solutions (dopes) with inherent viscosities as high as 1.6. Sulfonation of the aromatic diamine ring was a major side reaction. The effects of reaction variables such as temperature, time, monomer concentration, stoichiometry, and solvent acidity on molecular weight were studied. The dopes were spun to fiber, but tensile properties were limited by coagulation problems associated with hydrophilicity of the highly sulfonated polymer. Thermogravimetric analysis of SPT at 20°C/min showed weight loss only above 450°C.
Aromatic polyamides. VI. Synthesis of aromatic copolyamides and copolyamide–oxadiazoles in sulfur trioxide
Authors: Silver Frank M. , Black W. Bruce 
Published: April 2003

AbstractCopolymerization of para‐phenylenediamine sulfate (PPD‐S), hydrazine sulfate (Hy‐S), and terephthalic acid (TA) in SO3 yielded solutions of poly[p‐(disulfonatophenylene)terephthalamide]–co‐poly(p‐phenylene‐1,3,4‐oxadiazole) (SPT‐co‐POx). Reaction of PPD‐S, TA, and 4,4′‐sulfonyldibenzoic acid (SDBA) in SO3 gave sulfonated copolyamide (SPT‐co‐SPSDB) solutions. Solutions of both SPT‐co‐POx (mole % ratios of 70:30 to 90:10) and SPT‐co‐SPSDB (75:25 to 90:10) were anisotropic, illustrating liquid crystalline behavior for polymeric structures containing significant amounts of noncoaxial backbone components.
Polysiloxane dizwitterionomers. III. Water sorption
Authors: Graiver D. , Litt M. , Baer E. 
Published: April 2003

AbstractThe interaction of water with the various polysiloxane dizwitterionomers and the model compound 4,7‐diazaheptyl‐4,7‐di(3‐propane‐sulfonate) heptamethyltrisiloxane was studied. The model compound is soluble in water but the polymers swell inhomogeneously when soaked in water. The initial sorption kinetics of these zwitterionomers indicate similar mechanisms of water uptake which is independent of ion concentration (D = 4.7 × 10−7 cm2/sec). The sorption isotherms reveal the high sorptive capacity of these ionomers. Furthermore, the linear relationship between the water uptake and the concentration of ions over a large relative humidity range (0.22 ≤ P/P0 ≤ 0.93) allowed us to treat each phase separately. It has been found that most of the absorbed water molecules are immobilized in the ionic domains. Their concentration in this phase is nearly identical to the sorptive capacity of the model compound.
Polymer particle formation in soapless emulsion polymerization
Authors: Arai Masahiko , Arai Kunio , Saito Shozaburo 
Published: April 2003

AbstractPolymer particle formation in soapless emulsion polymerization for monomers that are soluble in diluent is studied theoretically and experimentally. A kinetic model is proposed assuming that polymer particles are formed by homogeneous nucleation of both growing radicals and dead polymer molecules above the critical size in solution. Based on this model, the dependence of the number of polymer particles on the concentration of initiator and monomer in solution is discussed for the polymerization system of methyl methacrylate–potassium persulfate–water. Experimental results of the number of polymer particles in this system can reasonably be interpreted by this model.
Polymerization of aromatic nuclei. XXII. Structure of the oligomer product from thiophene and trifluoroacetic acid: A reinvestigation
Authors: Margosian Daniel , Kovacic Peter 
Published: April 2003

AbstractA reinvestigation was made of thiophene polymerization by trifluoroacetic acid with the aim of elucidating the structure of the oligomer product. Comparison of spectral and molecular weight data was made with corresponding data for thiophene polymer generated by means of aluminum chloride and for trimer prepared from thiophene–phosphoric acid. We conclude that the solid product from thiophene–trifluoroacetic acid is best represented by the following structure:
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In addition, the major product is the known liquid trimer:
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Our designation is in disagreement with that of Wassermann et al., who proposed a structure having aliphatic unsaturation.