bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of poly(methyl methacrylate) and copolymers having enhanced thermal stabilities using sucrose‐based comonomers and additives
Authors: Sachinvala Navzer D. , Ju Ruei F. (Redford) , Litt Morton H. , Niemczura Walter P. 
Published: April 2003

AbstractA series of methyl methacrylate polymers have been prepared containing sucrose‐based crosslinkers and additives. Thermogravimetry and long‐term aging studies at 200°C show that sucrose‐based alkyl and allyl ethers provide unprecedented thermal stability to linear, as well as crosslinked, poly (methyl methacrylate) or PMMA. Linear PMMA and PMMA crosslinked with trimethylolpropane trimethacrylate (TMPTMA) both degrade at 284°C. PMMA containing octa‐O‐crotylsucrose (1 mol %) degraded at 322°C. Depending on concentration, PMMA containing octa‐O‐allylsucrose (0.1‐1.0 mol % and higher) degraded between 334 and 354°C, and PMMA containing 1′,6,6′‐trimethacryloyl‐2,3,3′,4,4′‐penta‐O‐methylsucrose (0.1‐1.0 mol %) degraded between 309 and 320°C. PMMA containing (1 mol % each) sucrose‐based esters, ester‐ether derivatives, all degraded at or below the degradation temperature of pure PMMA. Long‐term air aging studies revealed that PMMA containing penta‐O‐methylsucrose trimethacrylate, octa‐O‐allylsucrose, and octa‐O‐crotylsucrose did not flow or sag after heating for 24 h at 200°C, but the polymers did show yellowing. While linear and crosslinked samples of PMMA containing compounds other than sucrose ethers lost more than 50% of their original weight within 15 h at 200°C, PMMA containing sucrose‐based ethers lost about 8 and 20% of their original weight after 1 and 8.5 days, respectively. Herein we propose a unique mechanism by which saccharide ethers may be imparting this unprecedented thermal stabilization to PMMA. While tertiary hydrogens alpha to oxygens in saccharide ethers are stable to chain transfer during normal polymerization temperatures, they readily chain transfer at 200°C where PMMA is unstable. Chain transfer of these hydrogens is followed by fragmentation to produce alkyl, allyl or crotyl radicals, which combine with the macroradicals and terminate depropagation. © 1995 John Wiley & Sons, Inc.
Monomer‐isomerization polymerization. XXXVIII. Monomer‐isomerization copolymerizations of styrene and 2‐Butene with Ziegler–Natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

AbstractMonomer‐isomerization copolymerizations of styrene (St) and cis‐2‐butene (c2B) with TiCl3‐(C2H5)3Al catalyst were studied. St and c2B were found to undergo a new type of monomer‐isomerization copolymerization, i.e., only isomerization of 2B to 1‐butene (1B) took place to give a copolymer consisting of St and 1B units. The apparent copolymerization parameters were determined to be rst = 16.0 and rc2b = 0.003. The parameters were changed by the addition of NiCl2 (rSt = 8.4, rc2b = 0.05). The copolymers containing the major amount of St units were produced easily through monomer‐isomerization copolymerization of St and 2B. © 1995 John Wiley & Sons, Inc.
Convenient esterification of poly(γ‐glutamic acid) produced by microorganism with alkyl halides and their thermal properties
Authors: Kubota Hidetoshi , Nambu Yoko , Endo Takeshi 
Published: April 2003

AbstractThe esterification of poly(γ‐glutamic acid) (γ‐PGA) produced by Bacillus subtilis F2‐01 with alkyl halides was carried out at 60°C in N‐methyl‐2‐pyrrolidinone (NMP) in the presence of sodium bicarbonate to obtain the corresponding esterified γ‐PGA. The thermal properties of these γ‐PGA esters were examined by differential scanning calorimetry and thermogravimetry. γ‐PGA esters were more stable than free acid type γ‐PGA, which decomposed at 210°C. Melting temperature (Tm) of γ‐PGA esters could be observed at 230‐250°C. Tm of γ‐PGA n‐alkyl esters reached a maximum at an alkyl chain length of n = 3. © 1995 John Wiley & Sons, Inc.
Biocatalytic synthesis of polymers. III. Formation of a high molecular weight polyester through limitation of hydrolysis by enzyme‐bound water and through equilibrium control
Authors: Brazwell Eugenia M. , Filos Dianela Y. , Morrow Cary J. 
Published: April 2003

AbstractEnzyme‐catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures and has been studied for several years. A significant limitation on the polyesters prepared to date has been the low molecular weights achieved. The present studies have established that, in the polycondensation of bis(2,2,2‐trifluoroethyl) glutarate with 1,4‐butanediol using porcine pancreatic lipase as the catalyst, this limitation arises from at least two sources: hydrolysis of activated ester end groups by water introduced along with the enzyme and the polymerization's reaching equilibrium despite using the poorly nucleophilic 2,2,2‐trifluoroethanol as the leaving group. Evidence is also developed that the presence of trifluoroethanol accelerates the release of the enzyme‐bound water which hydrolyzes the activated ester end groups. The hydrolysis could be avoided by choosing a relatively high‐boiling solvent, such as bis(2‐ethoxyethyl) ether, then removing the trifluoroethanol by placing the reaction mixture under vacuum periodically or by drying the enzyme rigorously. The vacuum method also removed the limitation on molecular weight resulting from the reaction's reaching equilibrium. A further improvement in the molecular weight to nearly 40,000 daltons, well within the range that is technically interesting, was achieved by using 1,2‐dimethoxybenzene or 1,3‐dimethoxybenzene as the polymerization solvent. © 1995 John Wiley & Sons, Inc.
Molecular mechanics study of zirconocenium catalyzed isospecific polymerization of propylene
Authors: Yu Zhengtian , Chien James C. W. 
Published: April 2003

AbstractStereocontrol energy (ΔE0) is investigated as a measure of enantioselectivity of ansa‐zircoocenium catalyst in propylene polymerization; it was calculated with MM2 (molecular mechanics) force field using π complex (°C) and transition state (TS) geometries obtained by ab initio molecular orbital methods. Both rac‐ethylenebis (1‐η5‐indenyl) ‐ (1) and rac‐ethylenebis (1‐η5‐4,5,7,8‐tetrahydroindenyl) (2) zirconocenium species are isospecific in either the π‐complexes or the transition states. The stereoselectivity is greater if there is α‐agostic interaction; it is lowered in the cases of β and γ agostic interactions. The 13C‐NMR steric pentad distribution indicates the poly(propylene) to be much less stereoregular than that predicted by ΔE0. Following the occurrence of a regiochemical insertion error, the addition of another monomer via any mode is prohibitively unfavorable. The catalyst suffers loss of stereospecificity as temperature of polymerization increases. Insertion via transition states involving different agostic interactions could be one explanation for the observed loss. © 1995 John Wiley & Sons, Inc.
Epoxy‐amine multimethacrylic prepolymers, kinetic and structural studies
Authors: Titier Christelle , Pascault Jean‐Pierre , Taha Mohamed , Rozenberg Boris 
Published: April 2003

AbstractEpoxy‐amine methacrylated prepolymers are prepared in a 1‐step synthesis by the reaction of Bisphenol A diglycidyl ether, glycidyl methacrylate, and different diamines. The adaptation of these reactions to production processes with a reduced reaction time requires a kinetic control and the use of efficient catalysts. The comparative kinetic treatment of the epoxy‐amine reaction in the frame of Horie's and Rozenberg's kinetic schemes have been made. Cases where an efficient acid catalyst is used are also examined. Structural studies of these reactions established the occurrence of a Michael amine/double bond addition, when some amines are used. © 1995 John Wiley & Sons, Inc.
The photochemistry of polymers containing anthrylmethyl vinyl ketone
Authors: Modi Pankaj J. , Guillet James E. 
Published: April 2003

AbstractThe photolysis of copolymers of anthrylmethyl vinyl ketone (AMVK) with styrene and methyl methacrylate has been studied, both in solution and in the solid phase. Quantum yields of the order of 0.01 were observed in both cases for release of the major product, methyl anthracene (MA). Photolysis of an aqueous emulsion of a styrene‐AMVK copolymer showed similar yields of MA. The results indicate the possibility of using the Norrish type I process as a means of releasing drugs or other biologically active compounds from polymeric matrices. © 1995 John Wiley & Sons, Inc.
Synthesis and metal binding behavior of hydroxamic acid resins from poly(ethyl acrylate) crosslinked with divinylbenzene and hydrophilic crosslinking agent
Authors: Lee Taek Seung , Hong Sung Il 
Published: April 2003

AbstractPorous poly(hydroxamic acid) chelating resin was prepared by the reaction with poly(ethyl acrylate) crosslinked with divinylbenzene and hydrophilic crosslinking agent, and hydroxylamine. The hydrophilic crosslinking agents and diluent used in this article were ethylene glycol dimethacrylate or butanediol dimethacrylate, and 2,2,4‐trimethyl pentane, respectively. The characterization of this type chelating resin was carried out by IR spectroscopy, density measurement, and scanning electron microscopy. Various metal binding properties such as extraction, kinetics, and selectivity were investigated with atomic absorption spectrometer and inductively coupled plasma spectrometer. Poly(hydroxamic acid) resins crosslinked with mixed crosslinking agents showed better metal extraction properties and faster adsorption rate than those crosslinked with divinylbenzene alone. And alkali treatment enhances the binding rate for metal ions because of the formation of other chelating ligands or micropores. © 1995 John Wiley & Sons, Inc.
Molecular weight distributions of linear polymers: Detailed analysis from GPC data
Authors: Kissin Y. V. 
Published: April 2003

AbstractThe GPC method is used widely to measure molecular weights of linear polymers. High‐quality GPC data contains detailed information on many aspects of the polymer's molecular weight distribution (MWD). This information can be extracted from the data using computer analysis. Equations have been derived for the two simplest MWD functions in the GPC coordinates: the Flory function (one growing polymer chain produces one polymer molecule), and for the case when two polymer radicals combine into one polymer molecule. The equations were used to analyze MWD of two classes of polymers. The first class includes polymers with narrow MWD: polyethylene, ethylene‐propylene and ethylene‐hexene copolymers, syndiotactic polystyrene, and radical polystyrene. The second class includes polymers with broad MWD: ethylene copolymers and polypropylene produced with heterogeneous, Ti‐based catalysts. The examples demonstrate that the resolution of complex GPC curves into their constitutents serve as an important source of information about kinetics of polymerization reactions. © 1995 John Wiley & Sons, Inc.
Synthesis of functional substituted polycarbosilanes based on silyltriflate derivatives
Authors: Uhlig Wolfram 
Published: April 2003

AbstractPolycarbosilanes obtained by the Wurtz method or Grignard synthesis were converted by protodesilylation with trifluoromethanesulfonic acid to triflate‐substituted derivatives. Reactions of these polymers with nucleophiles led to novel functionally substituted polycarbosilanes. Polycarbosilanes with a regular alternating arrangement of silicon and carbon atoms, however, could not be obtained by this procedure. Such polymers were prepared by reactions of bis(trifluoromethylsulfonyioxysilyl)methanes with dinucleophiles. All syntheses are characterized by a high regioselectivity and high yields at low temperatures in short reaction times. The structures of the polymers were proven by NMR spectroscopy (29Si, 13C, 1H). © 1995 John Wiley & Sons, Inc.
Synthesis of stereoregular polygluconamides from D‐glucose and D‐glucosamine
Authors: Bueno M. , Galbis J. A. , García‐Martín M. G. , De Paz M. V. , Zamora F. , Muñoz‐Guerra S. 
Published: April 2003

AbstractTwo stereoregular polygluconamides, one (3) of polypeptide‐type and the other (16) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D‐glucosamine and D‐glucose, respectively. The new polyamides were characterized by elemental analysis, and IR, 1H‐ and 13C‐NMR spectroscopies. The molecular weights for 3 and 16 were estimated as 25,000 and 67,000, respectively, on the basis of viscosimetric measurements. Both polyamides display high optical activity; they are highly hydrophilic and readily soluble in water as well as in a variety of organic solvents including chloroform. Polyamide 16 is highly crystalline and yields resistant films with spherulitic texture. © 1995 John Wiley & Sons, Inc.
Synthesis of 1,1,9,9‐tetrafluoro[2.2]paracyclophane and its polymerization by vapor deposition method
Authors: Itoh Takahito , Okuoka Siro , Kubo Masataka , Iwatsuki Shouji 
Published: April 2003

Abstract1,1,9,9‐Tetrafluoro[2.2]paracyclophane (1) was prepared successfully as white crystals in 72% yield via two‐step reactions from 1,9‐diketo[2.2]‐paracyclophane. The polymerization of 1 by the vapor deposition method was carried out at pyrolysis temperature range of 400 to 800°C and deposition temperature range of −20 to 20°C, and a tough, transparent poly(α,α‐difluoro‐p‐xylylene) film was obtained in 72% yield at the pyrolysis temperature of 750°C and the deposition temperature of −20°C. It was found that the pyrolysis of 1 gave a reactive α,α‐difluoro‐p‐xylylene, which polymerized on the head‐to‐tail addition to give poly(α,α‐difluoro‐p‐xylylene). Some properties such as solubility, thermal stability, glass transition temperature, and density for poly(α,α‐difluoro‐p‐xylylene) were studied. © 1995 John Wiley & Sons, Inc.
Detection of nanoscale events in dispersed polymer particles containing a charge‐transfer fluorescence probe
Authors: Verhey Herman J. , Gebben Bert , Hofstraat Johannes W. , Verhoeven Jan W. 
Published: April 2003

AbstractA probe molecule, which shows an unusually large change in fluorescent properties in response to changes in its environment, was introduced into a monodisperse polystyrene latex. Upon addition of low‐molecular‐weight compounds, the ensuing swelling process of the latex could be followed via the changes in the fluorescence spectrum of the probe molecule. Polymerization reactions of monomers, introduced into the particles, could also be monitored by means of this approach. Using glycidylmethacrylate as the monomer led to the formation of particles in which two distinctly different surroundings could be detected after such a polymerization. © 1995 John Wiley & Sons, Inc.
Formation and characterization of simple and mixed vesicles based on monomeric and oligomeric phosphate bipolar amphiphiles
Authors: Kokkinia A. , Keramaris K. E. , Margaritis L. , Malliaris A. , Paleos C. M. 
Published: April 2003

AbstractCertain phosphate bipolar amphiphiles, both monomeric (I and II) and polymeric or rather oligomeric (poly‐I and poly‐II), were used as basic materials for the preparation of simple and mixed vesicles. Specifically, it was found that oligomeric phosphate bipolar amphiphiles form stable vesicles in aqueous media. The same oligomeric bolaamphiphiles in mixture with their monomeric counterparts also form stable mixed vesicles with sonication; they are relatively less stable with the “thin film method.” Furthermore, it was shown that the method of spanning the membrane of didodecylphosphate vesicels with the dipolar amphiphile II is not effective for enhancing stability. © 1995 John Wiley & Sons, Inc.
Curing of diglycidylamine‐based epoxides with amines: Kinetic model and simulation of structure development
Authors: Matêjka Libor , Duŝek Karel 
Published: April 2003

AbstractA complex mechanism of the reaction of diglycidylamine (DGA)‐based epoxides with primary amines is described and the kinetic model is developed. The reaction mechanism involves the addition of amine, etherification, and also formation of small cycles and anionic homopolymerization of the epoxide compound including transfer and termination. The polymer structure was theoretically described by distribution of structural fragments determined using the kinetic model. Simulation of the structure evolution during the DGA‐aniline reaction at varying molar ratios of reagents and dilution of the system was performed. The effect of the reaction conditions on the distribution of structural fragments, such as branching units and cyclic structures, was determined. © 1995 John Wiley & Sons, Inc.
Cationic polymerization of glycidyl phenyl ether by benzylammonium salts
Authors: Nakano S. , Endo T. 
Published: April 2003

AbstractNovel cationic initiators, p‐substituted benzylanilinium SbF–6 salts (1), were synthesized from the corresponding benzylchloride and N,N‐dimethylaniline, where Cl– was exchanged with SbF–6. Their catalytic activities in the cationic polymerization of glycidyl phenyl ether (GPE) were examined and compared to that of benzylpyridinium SbF–6 salts (2), latent thermal initiators previously reported by Endo et al. It was found that 1 acted as a latent thermal initiator in the cationic polymerization of glycidyl phenyl ether (GPE) above 80°C for 10 min. Furthermore, 1 showed higher activity than 2 having the same p‐substituents, except for a p‐Cl group in the cationic polymerization of GPE. Both the GPE polymer structure and the benzyl group reactivity in 1 or 2 indicate that 1 generates benzyl cations that are active species for the cationic polymerization of GPE, and that in cationic polymerization using 2, side reactions generating active species other than benzyl cations occur. magnified image © 1995 John Wiley & Sons, Inc.
Investigation of polyimides containing naphthalene units. II. Model compounds synthesis
Authors: Sek Danuta , Wanic Andrzej , Schab‐Balcerzak Ewa 
Published: April 2003

AbstractA series of model compounds from 4‐benzoyl‐1,8‐naphthalene anhydride and aromatic amines and diamines has been synthesized. The influence of the reaction conditions on the structure of the compounds obtained has been investigated to explain the high‐temperature polycondensation reaction mechanism. It was found that at high‐temperature polycondensation of 1,8‐naphthalene‐type anhydrides with aromatic amines, isoimides with cis and and trans structures are formed instead of amic acids. The only trans isoimides may isomerize to imide structure. © 1995 John Wiley & Sons, Inc.
Grafting of maleic anhydride to hydrocarbons below the ceiling temperature
Authors: Russell K. E. 
Published: April 2003

AbstractMaleic anhydride has been grafted to eicosane and squalane at 60–80°C using 1,2‐dichlorobenzene as solvent and benzoyl peroxide as initiator. These hydrocarbons are low molecular weight models for hydrocarbon polymers containing secondary and tertiary hydrogen atoms. In the absence of the hydrocarbon and with monomer concentrations of the order of 1M, low molecular weight poly(maleic anhydride) is formed. On addition of the hydrocarbon, the main product is grafted material and very little homopolymer is formed. The grafts consist primarily of single succinic anhydride units but some of them are short poly(maleic anhydride) chains. Ceiling temperature considerations control the formation of homopolymer in the absence of hydrocarbon substrate. In the presence of eicosane or squalane, initiation of grafting proceeds by hydrogen abstraction from the hydrocarbon. The main factor controlling graft length is then the ratio of the rates of intramolecular hydrogen abstraction and of monomer addition to succinic anhydride radicals © 1995 John Wiley & Sons, Inc.
Grafting of polymers with controlled molecular weight onto ultrafine silica surface
Authors: Tsubokawa Norio , Yoshikawa Sachio 
Published: April 2003

AbstractTo graft polymers with controlled molecular weight and narrow molecular weight distribution, the grafting of polymers onto ultrafine silica surface by the termination of living polymer cation with amino groups introduced onto the surface was investigated. The introduction of amino or N‐phenylamino groups onto the silica surface was achieved by the treatment of silica with γ‐aminopropyltriethxysilane or N‐phenyl‐γ‐aminopropyltrimethoxysilane. It was found that these amino groups on silica are readily reacted with living poly(isobutyl vinyl ether) (polyIBVE), which was generated with CF3COOH/ZnCl2 initiating system, and polyIBVE with controlled molecular weight and narrow molecular weight distribution is grafted onto the surface. By the termination of living poly(2‐methyl‐2‐oxazoline), which was generated with methyl p‐toluenesulfonate initiator, with amino groups on silica, polyMeOZO was also grafted onto the surface. The percentage of grafting of polymer onto the silica surface decreased with increasing molecular weight of the living polymer, because the steric hindrance of silica surface increases with increasing molecular weight of living polymer. Polymer‐grafted silica gave a stable dispersion in a good solvent for grafted chains. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of sulfone‐containing polyesters derived from 4,4′‐dicarboxydiphenyl sulfone by direct polycondensation
Authors: Liaw Der‐Jang 
Published: April 2003

AbstractSeveral sulfone‐containing polyesters having inherent viscosities 0.43‐0.19 dL g−1 were prepared by direct polycondensation of 4,4′‐dicarboxydiphenyl sulfone (DCDPS) with various aromatic and aliphatic diols, by p‐toluenesulfonyl chloride and N,N′‐dimethylformamide in pyridine solution. The polyesters were examined by elementary analysis, IR spectra, inherent viscosity, x‐ray diffraction, solubility, DSC, and TGA. The diffraction diagram showed that all polyesters were crystalline except that obtained from bisphenol‐A. All polymers were soluble in sulfonic acid (18M), phenol and p‐chlorophenol, but not in acetone and toluene. These polymers obtained from aromatic bisphenols lost no mass below 325°C, but 10% loss of mass was recorded above 396°C in nitrogen. DCDPS copolymerized with isophthalic acid (IPA) and bisphenol‐A had inherent viscosity up to 0.49 dL g−1,

with relatively narrow distribution of molar mass

. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of poly(4‐vinyl,2′‐carboxybensophenone)
Authors: Kamble K. J. , Patkar D. N. 
Published: April 2003

AbstractThe synthesis and characterization of poly(4‐vinyl,2′‐carboxybenzophenone) ion exchange resin is described. This resin displays a remarkably high capacity for Cu2+. Control of pH permits selective adsorption and estimation of Fe3+. This ion‐exchanger is quite stable to loading acid washing cycles. © 1995 John Wiley & Sons, Inc.
Kinetics and mechanism of the grafting of 2‐(dimethylamino)ethyl methacrylate onto hydrocarbon substrates
Authors: Shing J. B. Wong , Baker W. E. , Russell K. E. 
Published: April 2003

AbstractThe kinetics of grafting a basic monomer, 2‐(dimethylamino)‐ethyl methacrylate (DMAEMA) to hydrocarbon substrates have been investigated. These systems were chosen as models for the grafting of a homopolymerizable monomer to polyolefins such as polyethylene. The reactions with squalane and n‐eicosane were initiated by an organic peroxide, 2,5‐dimethyl 2,5 dit‐butylperoxy)‐3‐hexyne; grafting yields become significant at high reaction temperatures and low monomer concentrations. In squalane, the order of reaction with respect to monomer increased from about 1.1 for 0.22−0.44M DMAEMA to almost 2 at 0.69M DMAEMA; the order with respect to initiator was 0.56. The overall activation energy in the 130−160°C temperature range was, however, surprisingly low, 42±5 kJ mol−1. When analytical data were used to separate the overall rate into those for grafting and homopolymerization, different kinetic paths were observed for the competing reactions. These results are interpreted in terms of two different mechanisms; intramolecular chain transfer plays an important role in grafting, while depropagation becomes a major factor in homopolymerization at temperatures above 150°C. © 1995 John Wiley & Sons, Inc.