bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic oligomerization of styrene by solid acids. I. Catalysis by poly(styrenesulfonic acid) resin
Authors: Hasegawa Hiroshi , Higashimura Toshinobu 
Published: April 2003

AbstractCationic oligomerizations of styrene by a solid acid [poly(styrenesulfonic acid) resin, Amberlyst 15] and by the corresponding soluble catalyst (p‐toluenesulfonic acid) were compared with respect to their reactivity and the molecular weight distribution of products. The feature of Amberlyst 15 as oligomerization catalyst, in addition to its easy separation from products, was found to be was follows: The activity of Amberlyst 15 was 10 times larger than that of p‐toluenesulfonic acid in benzene, although catalyst deactivation at high conversions was observed for Amberlyst 15 at high monomer concentrations. Styrene trimer and tetramer were dominantly produced by Amberlyst 15 at low monomer concentrations, whereas a linear dimer was obtained in 85% yield with p‐toluenesulfonic acid. Characteristically, solvent polarity had almost no effect on the reaction rate and product composition in the Amberlyst 15‐catalyzed oligomerization. These facts were discussed in relation to differences between the heterogeneous and homogeneous catalyses.
Further studies on the postpolymerization of methyl methacrylate
Authors: Sarkar Arun K. , Palit Santi R. 
Published: April 2003

AbstractA search has been made for electroinitiators of postpolymerization. A number of hydroxycarboxylic acids and some of their sodium salts have been found to be quite efficient. Factors controlling the rate of polymerization and yield have been described. Surprisingly, citric acid, though not an electroinitiator of polymerization, is a good initiator of postpolymerization. Other active species that deserve mention are tartaric acid and its salts. A free radical mechanism involving formation of oligomeric initiator fragments, growth by attachment of imbibed monomer, and termination by chain transfer has been proposed to explain the observed facts.
Statistical mechanical estimation of the entropy of fusion of linear vinyl polymers
Authors: Gupta Mool C. , Nath Jaya D. 
Published: April 2003

AbstractThe entropy of fusion of linear vinyl polymers [polypropylene, polystyrene, and poly(vinyl chloride)] having asymmetric carbon atoms was calculated on the basis of the rotational isomeric state model. The results are found to be in good agreement with the experimental entropies of fusion per bond for these polymers.
Chemical modification of poly(N‐vinylcarbazole) by chloromethylation reaction
Authors: Pielichowski J. , Morawiec E. 
Published: April 2003

AbstractChloromethylation reaction of poly(N‐vinylcarbazole) was studied. The effect of the chloromethylating agent, catalyst, temperature, and reaction time on the course of chloromethylation reaction was investigated. The optimum conditions for introducing one chloromethyl group per one monomer unit were found. Thermal studies of chloromethylated poly(N‐vinylcarbazole) were carried out.
Diffusion‐controlled reaction. VI. Radiation graft polymerization of 4‐vinylpyridine to polyethylene
Authors: Odian George , Derman Arif , Imre Kaya 
Published: April 2003

AbstractThe radiation‐initiated graft polymerization of 4‐vinylpyridine to high‐density polyethylene was studied over a wide range of reaction conditions of radiation intensity I, monomer concentration M1, and polymer film thickness L. The conditions included both diffusion‐free and diffusion‐controlled graft polymerizations. The results corroborate our previous theoretical predictions on the effect of I, M1, and L on the experimental grafting rate. The grafting rate is inverse first order in L for diffusion‐controlled reaction and independent of L for diffusion‐free reaction. The dependence of grafting rate on radiation intensity decreases from 1/2 to 1/4 order for diffusion‐controlled reaction. Diffusion control results in a decrease in the dependence of rate on monomer concentration. The observed decrease is somewhat greater than theoretically predicted.
Photocrosslinking of elastomer systems. II. Ultraviolet light‐induced reactions in an EPDM modified by grafting of benzoin derivatives
Authors: Bousquet Jean‐Alain , Donnet Jean Baptiste , Faure Jean , Fouassier Jean‐Pierre , Haidar Bassel , Vidal Alain 
Published: April 2003

AbstractPhotocrosslinking experiments were performed on elastomeric polymer films (EPDM) previously modified by grafting a photosensitive initiator (benzoin derivative) onto the macromolecular backbone. This modification was performed by a series of Friedel–Crafts reactions and the resulting materials were characterized by infrared (IR) spectroscopy in conjunction with model reactions. After ultraviolet (UV) irradiation the photocrosslinked samples were studied by IR spectroscopy in conjunction with the measurement of physical properties. It apperared that grafting the photosensitizer onto the elastomer considerably enhances the crosslinking reaction even with a limited quantity of grafted benzoin derivative. Moreover, the results obtained suggest that the structure of the resulting networks is strongly dependent on the crosslinking process used; that is, curing the elastomer with peroxide or UV irradiation either of a blend of elastomer and photosensitizer or of the same elastomer modified by grafting the chromophore.
Synthesis and properties of polydiene and polypentenamer having formyl or hydroxymethyl groups and their photosensitive derivatives
Authors: Azuma Chiaki , Mitsuboshi Takao , Sanui Kohei , Ogata Naoya 
Published: April 2003

Abstractcis‐1,4‐Polybutadiene and polypentenamer having pendant functional groups such as formyl, aldoxime, hydroxymethyl, or cinnamoyloxymethyl groups have been prepared, and some of their properties were investigated in terms of structural effect on physical properties of these polymers. cis‐1, 4‐Polybutadiene and polypentenamer having a different content of formyl group were prepared by the hydroformylation reaction with rhodium catalyst under mild conditions. The pendant formyl group was reduced to a hydroxymethyl group by using various reducing agents such as sodium borohydride or sodium trimethoxyborohydride which were effective to avoid a crosslinking reaction among the formyl groups. Glass transition temperature of polypentenamer having hydroxymethyl groups increased with increasing the content of the hydroxymethyl groups in the polymer. Cinnamoyl group was introduced into the polypentenamer having hydroxymethyl groups by reacting with cinnamoyl chloride so as to prepare a photosensitive rubber. The relationships between the photosensitivity of the cinnamoylated polypentenamer and the mobility of polymer main chains have been elucidated. A linear relationship between the photodimerization rate constant and the difference between ultraviolet (UV) irradiation temperature and the glass transition temperature of the polymer was found. It has become apparent that the photosensitivity of cinnamoylated polypentenamer can be estimated by the glass transition temperature of the original polymer, UV irradiation temperature, activation energy of the dimerization, and γ, which is a coefficient of the relationship between the photosensitive group concentration and the glass transition temperature of the polymer.
Metal complexes with ligands–organic phosphites as polyolefin antioxidants. I. Kinetics and mechanism of polyolefin and model hydrocarbon stabilization by organic phosphites
Authors: Pobedimskii D. G. , Kirpichnikov P. A. 
Published: April 2003

AbstractThe most effective mechanism of protective action of organic phosphites–linear termination of kinetic chains on the inhibitor—has been established and the relative contribution of the other phosphite reactions (with hydroperoxides, their chain “self‐oxidation”) to the summary mechanism has been determined. The quantitative kinetic characteristics of efficiency and length of inhibitive action of different structure phosphites in the wide range of the phase state of the oxidized substrate (solid polymer, its melt, liquid phase) have been given. On this basis the regularities which allow the prediction of the structures of phosphites scavenging peroxy substrate radicals more effectively (effective inhibitors) have been formulated.
Vinyl polymerization in the presence of copper salts
Authors: Billingham Norman C. , Chapman Angela J. , Jenkins Aubrey D. 
Published: April 2003

AbstractThe radical polymerization of several vinyl monomers has been studied in the presence of cupric chloride. A termination reaction with CuII species leads to the formation of CuI species which can also participate significantly in termination with some, but not all, of the monomers studied. A theoretical treatment of the kinetics of such systems is presented which takes full account of initiator depletion during extended inhibition during extended inhibition periods. Specific velocity constants for reactions of polymer radicals with both CuII and CuI moieties are derived from observations on the nonstationary phase at the end of the inhibition period and from the subsequent steady state of polymerization. On the basis of the results presented here, together with the work of other authors, the patterns‐of‐reactivity approach gives α = −5.4, β = 9.0 as the parameters for copper (II) chloride. The implications of the results in relation to the mechanisms of the reactions between polymer radicals and both copper(II) chloride and copper(I) chloride are discussed. The kinetic treatment also provides an improved method for the determination of the rate of initiator decomposition and the rate of initiation form studies of the inhibition period.
Immobilization of enzymes with use of photosensitive polymers having the stilbazolium group
Authors: Ichimura Kunihiro , Watanabe Shoji 
Published: April 2003

AbstractReaction of the homopolymer of 2‐chloroethyl vinyl ether and the copolymer of N‐vinylpyrrolidone with stilbazole produced photosensitive polymers. The photocrosslinking mechanism is discussed. Irradiation of a film of the water‐soluble photosensitive polymer yielded insolubilized material in which the enzymes were entrapped. The activity of entrapped invertase, glucoamylase, and catalase was 30, 60, and 35%, respectively.
An experimental study of ideal and nonideal behavior in styrene emulsion polymerization
Authors: James D. R. , Sundberg D. C. 
Published: April 2003

AbstractAn experimental investigation was conducted to relate the average number of radicals per particle, n̄ to the dimensionless parameter α, as suggested by Stockmayer. Seed emulsion polymerizations of polystyrene were run over a wide range of particle sizes and initiator levels in the 50−70°C temperature range. The seed polymerization technique removed the question of particle formation behavior and allowed a straightforward determination of n̄. Alpha was varied more than three orders of magnitude and resulted in measured values of n̄ in the range 0.5−1.3. These data are in good agreement with Stockmayer's relationship as long as the value of the termination rate constant is taken at the monomer/polymer ratios found in emulsion polymerization. For polystyrene at a monomer/polymer ratio of 60/40 this value is an order of magnitude lower than that found for infinitely dilute polystyrene solutions.
Polymerization of diethylene glycol bis(allyl carbonate) by means of di‐sec‐butyl peroxydicarbonate
Authors: Schnarr Elizabeth , Russell Kenneth E. 
Published: April 2003

AbstractThe initial stages of the free radical polymerization of diethylene glycol bis(allyl carbonate) at temperatures of 35–65°C have been studied. The polymer is unsaturated and cyclization to give a 16‐membered ring occurs only to a small extent. The kinetic order with respect to the initiator, di‐sec‐butyl peroxydicarbonate, has an average value of 0.79; the order increases slightly with peroxydicarbonate concentration over the range 0.018–0.22M. The molecular weight of the polymer isolated after 3% polymerization is close to 19,000. It shows no significant dependence on initiator concentration or on temperature. The dominant feature of the bulk polymerization, as in free radical polymerization of the other allyl and diallyl monomers, is degradative chain transfer in which the growing polymer radical abstracts a hydrogen atom from a monomer unit to give a relatively unreactive allylic radical. The dependence of rate on initiator concentration is rationalized if some of these allylic radicals are able to reinitiate polymerization. The transfer constant to monomer is 0.014 at 50°C, assuming that the main termination step involves mutual termination of allylic radicals. Carbon tetrachloride is an active transfer agent with a transfer constant of 0.20 ± 0.04 at 50°C. Toluene, which is less active, has a transfer constant of 0.0064 at 50°C and also retards the polymerization. Some kinetic studies have been made with other initiators, including di‐2‐methyl‐pentanoyl peroxide which initiates polymerization at temperatures as low as 13°C.
Polymer flammability. I
Authors: Stuetz D. E. , Diedwardo A. H. , Zitomer F. , Barnes B. P. 
Published: April 2003

AbstractThe transport of oxygen by diffusion from the environment into a gas stream was investigated as a model for the analogous process in a diffusion flame. The amount transported at steady‐state conditions depended on the flow rate, diameter, and spatial orientation of the gas stream. A change of the same extrinsic parameters in a diffusion flame caused changes of burner surface temperature, maximum flame temperature, and flame height. These responses were correlated and yielded an overall activation energy of the rate‐controlling reaction step in the combustion process equal to 49 kcal/mole. This value was the same for several types of diffusion flames examined and appeared to be associated with the CO/CO2 conversion process at the high‐temperature flame boundary. Flame quenching was demonstrated to occur at a minimum fuel flow rate and minimum environmental oxygen concentration which were characteristic for a given fuel. Quenching conditions were related to the diffusion rate of oxygen into the product effluent stream. Quenching of a polymer flame by depletion of environmental oxygen was governed by the same processes. The effect of extrinsic parameters on polymer flames is discussed in Part II.
Polymer flammability. II
Authors: Stuetz D. E. , Diedwardo A. H. , Zitomer F. , Barnes B. P. 
Published: April 2003

AbstractThe responses of a polymer flame to changes of specimen diameter, ignition position, and stability of the burning surface were determined. These extrinsic flame parameters restricted the transport of oxygen from the environment to the burning surface. With increasing restriction the oxygen demand from the environment for self‐sustained combustion increased from a minimum oxygen demand at maximum access of environmental oxygen to the burning surface. This increase in oxygen demand was measured and correlated with surface oxygen concentrations estimated from the diffusion data of Part I. The minimum oxygen demand was demonstrated as characteristic for a given polymer and intrinsic in its chemical structure. This minimum oxygen demand, termed intrinsic combustibility, has been correlated with a polymer's thermooxidative stability, measured by thermogravimetric analysis at specific conditions. An intrinsic combustibility scale for polymers is given. In contrast, polymer flammability, as commonly measured in air, is interpreted as a variable property that depends on the extent of the interaction between extrinsic parameters, which are set by the testing configuration, with intrinsic combustibility.
NMR relaxation study of crosslinked cis‐1,4‐polybutadiene
Authors: Munie G. C. , Jonas Jiri , Rowland T. J. 
Published: April 2003

AbstractProton relaxation measurements have been used to investigate the effects of crosslinking on the segmental motion in cis‐1,4‐polybutadiene samples. The temperature dependence of proton spin–lattice relaxation time T1 and spin–spin relaxation time T2 at 60 and 24.3 MHz are reported in cis‐1,4‐polybutadiene (PB) samples with different crosslink density including uncrosslinked PB and samples with 140, 40, and 14 repeat units between crosslinks. In addition, spin‐lattice relaxation times in rotating coordinate frame, T1p, have also been determined. The relaxation data are interpreted in terms of the effects of crosslinks on segmental chain motions. Because of their sensitivity to low‐frequency motion, T2 data are of major interest. At temperatures well above the T1 minimum the small T2 temperature dependence resembles solidlike behavior reflecting the nonzero averaging of dipolar interactions due to anisotropic motion of the chain segments between crosslinks. The magnitude of T2 at 60°C is found to be proportional to the average mass between crosslinks.
Kinetics of step polymerization with reactants of unequal functional group reactivity
Authors: Ozizmir Ercument , Odian George 
Published: April 2003

AbstractA general solution is presented for the kinetics of an A–A plus B–C step polymerization. B and C are the same type of functional group but with different reactivities (k1 and k2, respectively) toward A groups. The decay of the concentrations of B, C, and A groups and the increase in the degree of polymerization with time are described for various values of the ratio k2/k1.
Utilisation du dicyclohéxyl‐18 couronne‐6 en polymérisation anionique. II. Polymérisation du methacrylate de methyle amorcee par les metaux alcalins
Authors: Alev Samson , Collet André , Viguier Michel , Schué François 
Published: April 2003

AbstractThe purpose of the present work, relative to anionic polymerization, is to describe the use of DCHE in order to prepare stable alkali metal solutions in low‐dielectric‐constant solvents. All these new species initiate the polymerization of methyl methacrylate avoiding the inconvenience of heterogeneous reactions. The presence of complexed ion pairs increases the syndiotactic structure. The polymerization seems to obey the Bernoullian statistics.
Grafting onto wool. IV. Effect of amines upon ceric ion‐initiated grafting of poly(methyl acrylate)
Authors: Misra B. N. , Chandel P. S. 
Published: April 2003

AbstractGrafting of poly(methyl acrylate) onto wool has been carried out in an aqueous medium at 45 ± 1°C by using ceric ammonium nitrate (CAN) in the presence of triethylamine, diethylamine, n‐butylamine, triethanolamine, and N,N‐dimethylaniline. The percentage of grafting varied with the nature and concentrations of the amines. Reactivity of the different amines toward grafting reactions followed the order: triethylamine > diethylamine > n‐butylamine > triethanolamine ≥ N,N‐dimethylaniline. In the presence of N,N‐dimethylaniline grafting did not occur. An attempt has been made to explain the observed reactivity of Ce4+ in various amine systems in graft copolymerization reactions.
Thermal‐induced conversion of maleic and fumaric acid anion radicals in poly(methyl methacrylate)
Authors: Torikai Ayako , Fukumoto Mikiya 
Published: April 2003

AbstractThermal‐induced conversion of maleic and fumaric acid anion radicals produced by γ irradiation at 77 K in poly(methyl methacrylate) (PMMA) was studied by electron spin resonance (ESR) and optical absorption spectroscopic measurements. The ESR spectra of these acid anion radicals change into two‐line spectra with a line separation of ca. 10 G by thermal annealing. This spectrum is assigned to a protonated radical of each acid anion radical. Anion radicals of the solutes are relatively stable below the γ transition point of PMMA and the conversion reaction takes place near this point. This means that the molecular motion of matrix molecule affects the radical conversion reaction.
An investigation of the vacuum UV spectra of inductivity coupled RF plasmas excited in inert gases as a function of some of the operating parameters
Authors: Clark D. T. , Dilks A. 
Published: April 2003

AbstractThe vacuum ultraviolet (UV) emission from inductively coupled radio‐frequency (RF) plasmas excited in a series of inert gases has been studied as a function of the pressure and applied power of the system. The effects of discharge tube size and pulsing of the applied RF power are also considered and a comparison is made between RF and microwave excitation.
Circular dichroism of polyethylenimine containing optically active thymine derivatives as grafted pendants
Authors: Overberger C. G. , Morishima Y. 
Published: April 2003

AbstractOptical properties of linear polyethylenimine containing optically active (+)‐ or (−)‐2‐(thymin‐1‐yl)propionyl group as grafted pendant were investigated by circular dichroism (CD) and compared with those of the related monomer and dimer model compounds. CD spectra of the polymer in neutral aqueous solution were different from those of related model compounds, which suggest that the polymer exists in some ordered conformation (at least locally) to allow exciton coupling of π–π* (B2u) transition in the base chromophores along the polymer chain. This ordered conformation tends to be randomized on heating. The effects of complementary base pairing on the CD spectra have also been studied by using a linear polyethylenimine containing (±)‐2‐(adenin‐9‐yl) propionyl grafts and its related monomer and dimer models.
A new method of estimating monomer reactivity ratios in copolymerization by linear regression methods
Authors: Watts D. G. , Linssen H. N. , Schrijver J. 
Published: April 2003

AbstractSequential gas‐liquid chromotographic analysis of the reaction mixture throughout a copolymerization reaction in conjuction with the improved curve‐fitting I (integrated form) method, which accounts for measurements errors in both variables, allows accurate estimation of the monomer reactivity ratios. In this article an alternative method is presented for estimating r values in copolymerization with linear regression only, which is especially suited to cases in which one or two of the r values is close to 1. In these cases the improved curve‐fitting I method tends to converge slowly because of the numerical instability of the integrated copolymerization equation. The use of the new method is illustrated for the estimation of the r values for ethylene and vinyl acatate in benzene at 35 kg/cm2 and 62°C. The linear regression method was also tried on other copolymerizations and the results are compared with those obtained from the improved curve‐fitting I method. The limits of the applicability of the linear regression method were determined by simulated sequential sampling experiments. It appears that the new method is applicable when the product of the r values is between 0.001 and 2, provided both monomer conversions are large enough compared with the measurements error.
Molecular weight distribution in emulsion polymerizations
Authors: Lichti Gottfried , Gilbert Robert G. , Napper Donald H. 
Published: April 2003

AbstractA mathematical formulation is given which describes the evolution of the number distribution of the molecular weight (MWD) of linear polymer chains that grow in emulsion polymerization systems. The resulting set of coupled ordinary differential equations takes into account the microscopic events of free radical entry, exit, chain annihilation, bimolecular termination (by combination and disproportionation), and chain transfer in a mono‐ or polydisperse system. Simple analytic solutions are presented for systems in which the number of particles, as well as the average number of free radicals per particle, is constant and in which the rate coefficients are size independent. These solutions indicate that compartmentalization of the free radicals in the latex particles results in a significant increase in the polydispersity of the polymer produced by emulsion polymerization, compared with that in bulk systems. The theory shows that significant mechanistic information may be obtained from experimental MWDs and that, in principle, experimental conditions may be prescribed to grow a desired MWD. The MWDs are presented in a novel manner that facilitates the comparison of theory with experiment.