bluuebunny/crossref_metadata_2025_split huggingface dataset:
Miniemulsion copolymerization of vinyl acetate and butyl acrylate. I. Differences between the miniemulsion copolymerization and the emulsion copolymerization processes
Authors: Delgado Joaquin , El‐Aasser Mohamed S. , Vanderhoff John W. 
Published: April 2003

AbstractDifferences between the emulsion copolymerization and miniemulsion copolymerization processes, in terms of emulsifier adsorption, emulsion stability, polymerization kinetics, copolymer composition and dynamic mechanical properties were studied for the comonomer mixture of 50:50 molar ratio vinyl acetate (VA+)—butyl acrylate (BuA), using sodium hexadecyl sulfate (SHS) as a surfactant and hexadecane (HD) as a co‐surfactant. The use of hexadecane with the appropriate SHS initial concentration led to a higher adsorption of surfactant, smaller droplet size, higher stability of the emulsions, lower polymerization rates, and larger latex particle size. The copolymer composition during the initial 70% conversion was found to be less rich in Vac monomer units for the miniemulsion process. The dynamic mechanical properties of the copolymer films showed less mixing between the BuA‐rich core and the VAc‐rich shell in the miniemulsion latexes compared to the conventional latex films.
Polymérisation radicalaire du pentadiène‐1,3. I. Copolymérisation des cis et trans pentadiènes‐1,3 avec l'acrylonitrile. Détermination des rapports de réactivité
Authors: Petit A. , Neel J. 
Published: April 2003

AbstractCis (CP) and trans (TP) isomers of 1,3‐pentadiene (piperylene) were homo and copolymerized with acrylonitrile (A) in bulk and emulsion, at 50°C, using azobisisobutyronitrile and potassium persulfate as free radical initiators. The cis isomer reacts more rapidly than the trans monomer. The copolymer compositions were determined from nitrogen analysis, 100‐MHz 1H‐NMR and 25‐MHz 13C‐NMR spectra. The results thus obtained show that both the bulk and emulsion processes yield copolymers characterized by a very similar composition. Data plotted according to the Kelen‐Tüdös method indicate that the terminal‐unit model is applicable to the piperylene‐acrylonitrile system. Reactivity ratios for bulk copolymerization were as follows: rA = 0.079, rTP = 0.114, and rA = 0.033, rCP = 0.188. These values are very small and hence suggest a strong alternating tendency for acrylonitrile and 1,3‐pentadiene in both comonomer systems. This latter conclusion is corroborated by the comparison of the NMR spectra of the synthesized copolymers with that of a standard alternating sample. The reactivity (Q) and electronegativity (e) of the 1,3‐pentadiene isomers calculated from the reactivity ratios by the Alfrey—Price equations were QTP = 0.56, eTP = −0.97 and QCP = 1.215, eCP = −1.055 for trans and cis dienes, respectively.
Chain scission efficiency and reactive‐ion etch resistance of alternating copolymers of styrene and olefins trisubstituted or tetrasubstituted with electron‐withdrawing groups
Authors: Ito Hiroshi , Hrusa Claudia , Hall H. K. , Padias Anne B. 
Published: April 2003

AbstractAlternating copolymers of styrene (St) with electron‐deficient olefins trisubstituted or tetrasubstituted with cyano and carboalkoxy groups have been subjected to 60Co γ‐radiolysis together with a series of copolymers of methyl methacrylate (MMA) and St. The chain scission susceptibility Gs—Gx determined by membrane osmometry drastically decreases as St is incorporated in poly(methyl methacrylate) (PMMA). Whereas the alternating St‐MMA copolymer is slightly crosslinked upon irradiation, an alternating copolymer of St with diethyl 2‐cyano‐1,1‐ethylenedicarboxylate maintains a fairly high degradation sensitivity (Gs—Gx = 1.2). The reactive‐ion etch rates were determined for the series of polymers in CF4/O2 (92/8). The etch resistance is significantly increased by introduction of St units in PMMA, and the highly substituted alternating copolymer etches as slowly as the MMA(50)—St(50) copolymers. Thus the alternating copolymer of NCCH=C(CO2Et)2 with St behaves like PMMA when exposed to high‐energy radiation but is comparable to PSt in plasma environments.
Photopolymerization of methyl methacrylate using a combination of rhodamine 6G and benzoyl peroxide as photoinitiator in nonaqueous media
Authors: Ghosh Premamoy , Biswas Samir , Niyogi Utpal 
Published: April 2003

AbstractPhotopolymerization of methyl methacrylate (MMA) in visible light was studied at 40°C using Rhodamine 6G—Benzoyl peroxide combination as photoinitiator. The photopolymerization proceeds by a free radical mechanism and the radical generation process occurs by an initial complexation reaction between the initiator components. Kinetic data indicated a lower‐order dependence of Rp on initiator concentrations (initiator exponent < 0.5). Initiator‐dependent chain termination was significant along with the bimolecular mode of chain termination.
Polydimethylsiloxane–vinyl block polymers. I. The synthesis of polydimethylsiloxane macroinitiators containing thermolyzable bis(silyl pinacolate) groups in their backbones
Authors: Crivello J. V. , Conlon D. A. , Lee J. L. 
Published: April 2003

AbstractThis first paper on the topic of polydimethylsiloxane–vinyl block polymers describes the development of a unique class of vinyl functional silicon containing free–radical initiators which can be used in the synthesis of block polymers. Details of the synthesis and characterization of these initiators are described together with the kinetics of their thermolysis. Specific conditions are described under which these initiators can be condensed with α,ω‐hydrogen functional polydimethylsiloxane oligomers by a platinum‐catalyzed hydrosilylation reaction to yield macroinitiators.
High‐temperature reactions of hydroxyl and carboxyl PET chain end groups in the presence of aromatic phosphite
Authors: Aharoni S. M. , Forbes C. E. , Hammond W. B. , Hindenlang D. M. , Mares F. , O'Brien K. , Sedgwick R. D. 
Published: April 2003

AbstractWhen melt‐extruded in the presence of triphenylphosphite (TPP), the molecular weight of polyesters such as poly(ethylene terephthalate) (PET) increases with time. Analysis of the PET chain end groups and model studies of high‐temperature reactions indicate that, most likely, the process leading to chain extension of PET in the presence of TPP takes place in two steps. In the first step, TPP rapidly reacts with the hydroxyl end groups by displacing one phenoxy group from the TPP. In the second step, a slow reaction takes place between the alkyldiphenyl phosphite and carboxylic chain end groups, forming an ester bond between the carboxyl and alkyl groups, and producing diphenylphosphite (DPP) as a reaction by‐product. The DPP tautomerizes to its pentacovalently bonded stabler form of diphenylphosphate, the form in which the DPP was usually detected in our analyses. The ester formation results in the extension of the PET chains. Model studies are presented which support the proposed mechanism.
Inhibition by red phosphorus of unimolecular thermal chain‐scission in poly(methyl methacrylate): Investigation by NMR, FT‐IR and laser desorption/fourier transform mass spectroscopy
Authors: Brown Charles Eric , Wilkie Charles A. , Smukalla Jeffrey , Cody Robert B. , Kinsinger James A. 
Published: April 2003

AbstractThe reaction of red phosphorus with poly(methyl methacrylate) under pyrolysis conditions was investigated with a number of physical techniques. A random methyl methacrylate/cyclic anhydride copolymer is formed from atatic PMMA, whereas a random methyl methacrylate/methacrylic acid copolymer is obtained with isotactic PMMA. The backbones of both these copolymers are more stable toward depolymerization than that of PMMA. The flame‐retardant activity of red phosphorus with PMMA may arise in part from stabilization of the polymer toward depolymerization via modification of the sidechains.
Preparation and structure of polymers from methoxy and hydroxy alkyl phenyl vinyl ketones
Authors: Aglietto Mauro , Cioni Luca , Ruggeri Giacomo , Taburoni Elisa , Tomei Edoardo 
Published: April 2003

AbstractThe preparation of 2‐methoxy‐5‐t‐butylphenyl vinyl ketone (MeOBVK), 2‐hydroxy‐5‐t‐butylphenyl vinyl ketone (HOBVK), and 2‐methoxy‐5‐isooctylphenyl vinyl ketone (MeOOVK) is reported. These compounds can be considered as precursors of polymerizable derivatives of polyoxyethylated alkylphenols—a very important class of nonionic surface active compounds. The homopolymerization and copolymerization of MeOBVK, HOBVK, and MeOOVK with butylacrylate (BA), (–) menthylacrylate [(–)MtA], styrene (STY), and vinylacetate (VA) by free radical initiators, both in solution and emulsion, have been investigated. Copolymer formation has been demonstrated by fractionation and by the presence of induced optical activity in the electronic transitions of the achiral MeOBVK and HOBVK units in copolymers with the optically active comonomer (—)MtA. MeOBVK, HOBVK and MeOOVK give substantially random copolymers with STY, BA, or VA under all conditions investigated, and always show larger reactivity; thus, depending on feed composition, sequences of the vinyl ketone units can be expected in the macromolecules.
Poly(vinyl ether)s and poly(propenyl ether)s containing mesogenic groups: A new class of side‐chain liquid‐crystalline polymers
Authors: Rodriguez‐Parada Jose M. , Percec Virgil 
Published: April 2003

AbstractA new series of thermotropic liquid‐crystalline polymers, poly(vinyl ether)s and poly(propenyl ether)s, containing the mesogen 4‐methoxy‐4′‐hydroxybiphenyl in the side chain and different spacers between the mesogens and the backbone were synthesized and characterized by DSC and optical microscopy. Their mesomorphic behavior was compared to that of the corresponding polymethacrylates. In general the poly(propenyl ether)s showed lower transition temperatures and larger thermal stability ranges of their mesophases than the respective polymethacrylates, reflecting the effect of substituting the rigid ester bond connecting the spacer to the backbone in polymethacrylates by a more flexible ether bond. Also, poly(propenyl ether)s showed more ordered mesophases than the polymethacrylates, suggesting that a better decoupling of the mesogen and polymer backbone is obtained through the ether linkage.
Radical copolymerization of acrylic monomers. VIII. Copolymerization of methyl methacrylate with methyl α‐p‐chlorobenzylacrylate and methyl methacrylate with methyl α‐p‐methoxybenzylacrylate
Authors: Madruga E. L. , Roman J. San , Lavia M. A. 
Published: April 2003

AbstractFree‐radical copolymerization of methyl methacrylate with methyl α‐p‐chlorobenzylacrylate and methyl methacrylate with methyl α‐p‐methoxybenzylacrylate have been studied in benzene solution at 40°C. Although a simple copolymerization model fits the composition data, the kinetic behavior of both copolymerization systems are analyzed from simple and reversible copolymerization models, taking into account the relatively low ceiling temperature of both methyl α‐(p‐substituted benzyl)acrylates and considering that the overall rate of copolymerization drastically decreases with the increase of the corresponding methyl α‐(p‐substituted benzyl)acrylate molar fraction in the feed.
Some aspects of the bimetallic μ‐oxo‐alkoxides for polymerizing epoxides to polyether elastomers
Authors: Vandenberg E. J. 
Published: April 2003

AbstractThe bimetallic catalysts of Osgan and Teyssie, (RO)2Al‐O‐Zn‐O‐Al(OR)2, are effective, unusual catalysts for polymerizing epoxides. The polymer obtained from propylene oxide when R = n‐Bu is preponderantly isotactic and highly crystalline and thus, largely head‐to‐tail. Crystallizable, sulfur vulcanizable propylene oxide rubber was made by copolymerizing propylene oxide (PO) with allyl glycidyl ether (AGE) with this catalyst. This product after S vulcanization exhibited gum tensile and other properties which were superior to the commercially available, amorphous PO–AGE copolymer of similar composition. However, the Osgan–Teyssie catalyst is very sensitive to reactive, polar impurities. Hindered alkyl aluminums and especially alkoxides such as Et2AlOtert–Bu can be added to help alleviate this problem. The reported favorable (but slow) copolymerization of epichlorohydrin with propylene oxide in nonpolar media with the Osgan–Teyssie catalyst has been confirmed and an alternate explanation for this unusual result suggested.
Charge mosaic membranes: Microdomain fixing of (polystyrene–poly‐4‐vinylpyridine) sequential copolymers prepared by macromonomer methods
Authors: Ishizu Koji , Murakami Atsushi , Fukutomi Takashi 
Published: April 2003

AbstractPolystyrene (PST) macromonomers having several allyl groups at the ends were synthesized by the mechanical scission reaction of the main chain in the presence of diallylmalonic acid diethyl ester (DAME). Photosensitive benzophenone groups were introduced on a PST macromonomer molecule by the reaction of these PST macromonomers with benzoyl chloride. The palm‐treelike (PST–poly‐4‐vinylpyridine (P4VP)) sequential copolymers with different compositions were prepared by the radical copolymerization of PST macromonomer with 4VP. The morphological observation of these sequential copolymers was carried out by the transmission electron microscopy. The PST block microdomains were fixed by photocrosslinks (UV irradiation) in the presence of mono‐ and bifunctional unsaturated compounds in the state of mesomorphic structures. The microdomain fixing of P4VP blocks was carried out by using the vapor of 1, 4‐dibromobutane (DBB). After subsequent chemical modifications (quaternization of residual P4VP blocks and sulfonation of PST blocks), the effect of microdomain fixings was elucidated from the moisture content of positive and negative regions. These results are discussed in some detail.
An unusual reaction polymerization in nitric acid medium
Authors: Bugni Ednéia A. , Lachtermacher Marly G. , Monteiro Elisabeth E. C. , Mano Eloisa B. , Overberger C. G. 
Published: April 2003

AbstractWe are investigating an unusual reaction that occurs when methyl methacrylate (MMA) is kept in contact with concentrated nitric acid1(65% HNO3, sp. gr. 1.41). Polymer of high molecular weight is formed, showing about one unit of methacrylic acid (MAA) per unit of MMA, when equilibrium is reached. The reaction depends on the temperature, the molar ratio MMA:HNO3, and the reaction time. Although we also found polymer at temperatures in the range 50–70°C,2in this paper we only report the results when the temperature was kept between 25 and 40°C. Methacrylic acid (MAA) was found to homopolymerize under those mild conditions; its behavior was investigated. Although we also observed that polymer is formed with sulfuric acid (96%) and that acrylic acid polymerizes with both nitric and sulfuric acid at 20–30°C, we are limiting this article to the observed polymerizing action of nitric acid on methyl methacrylate and on methacrylic acid. Work proceeds on this matter in this laboratory.
Amino acid end‐group in commercial heparin. II. Reaction kinetics of the amino end groups with 2,4,6‐trinitrobenzenesulfonic acid
Authors: Arai Kozo , Nakamura Yoshio , Edwards H. E. , Phillips G. O. 
Published: April 2003

AbstractThree different commercial heparins were trinitophenylated with 2,4,6‐trinitrobenzenesulfonic acid (TNBS) under aqueous conditions. The reaction kinetics of amino groups in heparin with TNBS showed that the reactivities of amino groups were significantly different for free amino groups on heparin, compared to reactivities in peptides and amino acid residues attached to heparin molecules. With TNBS, unreactive amino groups were always present during the reaction.
Monomer‐isomerization polymerization. XXI.. Monomer‐isomerization copolymerization of 3‐methyl‐1‐butene and 2‐pentene with ziegler–natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

Abstract3‐Methyl‐1‐butene (3M1B) was found to undergo monomer‐isomerization copolymerization with 2‐pentene (2P) in the presence of Ziegler–Natta catalyst to give a copolymer exclusively consisting of 3M1B and 1‐pentene (1P) units, the same as that obtained from copolymerization of 3M1B and 1P. The apparent copolymerization parameters were determined. The amount of 3M1B unit incorporated in the copolymers was found to increase in the copolymerization system of 3M1B‐2P more than in that of 3M1B‐1P. The polymers consisting of nearly complete 3M1B units were produced at a rapid rate through monomer‐isomerization copolymerization of 3M1B with 2P in the presence of TiCl3 − (C2H5)3Al catalyst.
Preparation of conducting copolymers by oxidative electropolymerization of 2,2′‐bithiophene with pyrrole
Authors: Funt B. Lionel , Peters Eric M. , Van Dyke John D. 
Published: April 2003

AbstractVarious feed ratios of 2,2′‐bithiophene (BT) and pyrrole (PY) were electropolymerized to low conversion and the polymers analyzed for their mer ratios. The polymeric product was rich in polypyrrole (PPY), but the composition could be varied by control of the electrode potential. The increase in BT content is not linear with composition, and the physical evidence indicates oxidative copolymerization and not the formation of the two homopolymers. The data can be interpreted on a copolymerization equation despite the absence of steady state conditions. Sets of reactivity ratios were determined for the polymers formed at two potentials. The electrical efficiencies for polymer formation approach stoichiometric values for oxidative polymerization.
Thermal properties of nylons containing carbonyl groups
Authors: Do C. H. , Pearce E. M. , Bulkin B. J. , Reimschuessel H. K. 
Published: April 2003

AbstractNylons containing carbonyl groups in backbone chains were prepared and their response to heat was studied. The carbonyl groups were introduced using either HOOC(CH2)4CO(CH2)4COOH or H2N(CH2)5CO(CH2)5NH2 in the initial monomer compositions. In addition to pyrolysis of these polyamides, the progress of chemical and physical changes as a function of temperature was continuously monitored and analyzed by FT–IR spectroscopy on cast films placed in an environmental chamber. Introduction of the carbonyl groups into the polymer backbone resulted in a significant reduction of the thermal stability of the corresponding polyamide. Possible mechanisms for the thermal degradation entailing these carbonyl groups and N‐acylamide compounds are discussed.
Semiconducting polymers via the high temperature free radical polymerization of multinitriles
Authors: Padias Anne Buyle , Hall H. K. 
Published: April 2003

AbstractThe polymerizability of a variety of mono‐ and multi‐ nitriles in the presence of free radical initiators at high temperature is determined by the concentration of available cyano‐groups. Mononitriles do not polymerize, but multinitriles do so readily. If alkyl substituents are introduced in a molecule that easily polymerizes, this concentration and the ability to polymerize are lowered; if several or bulky substituents are introduced, the polymerization is completely prevented. Multinitriles containing ester groups undergo decarbomethoxylation in these polymerizations. The polymers are black and highly insoluble. From the few reactions that were attempted on these polymers, we can conclude that the structure is probably not the simple conjugated imine structure proposed by earlier investigators, but more experiments are needed to prove this point. The black polymers had conductivities less than 10−9 Ω−1 but, after heating at 700°C, conductivities in the range from 10−3 to 10−6 Ω−1 are observed.
Synthesis and properties of semiconducting aromatic polyquinonediimines
Authors: Everaerts A. , Roberts Sue , Hall H. K. 
Published: April 2003

AbstractA new class of poly‐conjugated polymers has been obtained by condensation of anthraquinones with aromatic diamines in polyphosphoric acid. The polymers are black, intractable powders. Toward obtaining tractable materials, the effect of monomer structure on polymer tractability has been studied. Copolymerizations were also carried out to “soften” these materials. Electrical conductivities in the semiconducting range, 10−4‐ 10−8 (ohm cm)−1 were observed. Doping with iodine showed small increases.
Kinetics of crosslinking reactions. 1. Reaction rate of intramolecular crosslinkings by using a soluble microgel
Authors: Ishizu Koji , Kuwabara Shojiro , Chen Hui , Mizuno Hirohide , Fukutomi Takashi 
Published: April 2003

AbstractSoluble microgels with several pendant vinyl groups were synthesized by radical copolymerization of methyl methacrylate (MMA) with p‐divinyl benzene (p‐DVB). The polymerization conditions used for intramolecular crosslinking of microgels were chosen from gel permeation chromatograph (GPC) measurements of the reaction products. The rate constant of intramolecular crosslinking (kpi) was estimated from the changes in the concentration of pendant vinyl groups of microgel by using photometrical measurements at 30°C assuming a unimolecular termination mechanism of polymer radicals. As a result, kpi showed larger values than kp of styrene and depended strongly on the internal structure of the microgels.
Configurational stereoselectivity in the nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate: NMR study and Monte‐Carlo simulation of the reaction
Authors: Spitz Roger , Llauro‐Darricades Marie‐France , Michel Alain , Guyot Alain , Mijangos Carmen , Martinez Gerardo , Millan Jose Luis 
Published: April 2003

AbstractThe nucleophilic substitution of the chlorine atoms of poly(vinyl chloride) with sodium thiophenate is assumed to obey an SN2 mechanism with inversion of configuration and a steric control according to which reactivities R of the triads follow the order Rmm > Rmr ≫ Rrr. Such a reaction cannot be described by simple differential equations, but a Monte Carlo simulation, first generating a random Bernouillian chain and then simulating random attack of the chain by the reactant according to the triad reactivities, allows a good agreement with the experimental results of both the kinetics of a reaction carried out in cyclohexanone solution at 40°C and the evolution of the 13C and 1H NMR spectra of the tertiary carbon atoms, assuming the following parameters: Bernouillian probability for a meso placement in the initial chain: 0.431; relative reactivities of the mm, mr and rm, rr triads: 1, 0.5, and 0., respectively. The agreement is excellent until the reaction is about three‐quarters complete; this shows a limiting level of about 60% substitution. Better agreement can be obtained up to the limit, if a secondary process of steric control by the substituant in a partially substituted mr triad is assumed. Other possibilities for that secondary process are discussed.
Synthesis and characterization of fluorescently labelled poly(vinyl acetate) particles
Authors: Egan Luke S. , Wimmik Mitchell A. , Croucher Melvin D. 
Published: April 2003

AbstractNonaqueous dispersions of poly(vinyl acetate) particles stabilized with poly(2‐ethylhexyl methacrylate) and labelled with fluorescent dyes in the core and stabilizer polymer phases were prepared. The materials were characterized using a broad range of techniques (NMR, UV, and fluorescence spectroscopy. GPC, particle sizing, and DSC). The data show that dispersion polymerization of vinyl acetate in the presence of stabilizers containing certain fluorescent dye derivatives, instead of unlabelled stabilizer, results in changes in the mean particle size, size distribution, composition, and molecular weights of the colloidal polymer particles. It was found that increasing the amounts of fluorescent groups in the stabilizer resulted in smaller mean particle sizes and larger amounts of irreversibly attached stabilizer. When the average number of labels in stabilizer exceeded one per chain, a new ultra‐high molecular weight polymer fraction appeared. The fluorescence spectra for several of these materials are reported. We describe how fluorescence decay curves can be used to assess block formation and local phase separation in particles labelled with phenanthrene groups. These materials are intended to be used for more detailed studies by fluorescence spectroscopy. Those results will be published in due course.