bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of phenylacetylene using palladium (II) catalysts
Authors: Trumbo D. L. , Marvel C. S. 
Published: April 2003

AbstractPoly(phenylacetylenes) were synthesized using various palladium (II) salts as initiators. In the case of palladium diacetate, the polymerizations were found to be extremely exothermic, with explosions occurring on some occasions. The polymers produced yielded two fractions, a methanol soluble and a methanol insoluble fraction. Both fractions were found to be low molecular weight linear polymers.
Reactions of the 2‐cyano‐2‐propyl radical with vinyl acetate and other monomers: A study of head‐addition
Authors: Bevington John C. , Breuer Stephen W. , Heseltine Elizabeth N. J. , Huckerby Thomas N. , Varma Sushil C. 
Published: April 2003

AbstractPolymers have been prepared at 60 and 100°C using initiators giving the 2‐cyano‐2‐propyl radical enriched with carbon‐13 in the nitrile group. Examination by NMR of the (CH3)2C(CN) end groups in the resulting polymers of vinyl acetate (VAC) and of appropriate model compounds has indicated that up to 20% of these end groups correspond to the product of head‐addition of the primary radical to VAC at 60°C. Similar end groups have been found in poly(vinyl formate) but not in poly(methyl methacrylate) and polystyrene. In polyVAC prepared at 100°C, the proportion of end groups attached to the head of a monomeric unit is higher than for polymers made at 60°C.
Graft copolymers of para‐hydroxybenzoic acid (PHB). I. A general method for grafting mesogenic oligo‐PHB to oligomers
Authors: Chen Der‐Shyang , Jones Frank N. 
Published: April 2003

AbstractA method for grafting oligo‐(p‐hydroxybenzoic acid) to carboxyl‐functional oligomers or polymers to give copolymers having mesogenic side chains was developed. The method employs dicyclohexylcarbodiimide (DCC) to promote esterification of PHB at mild temperatures and to remove water. Pyridine is used as solvent, and catalytic amounts of p‐TSA are added to suppress side reactions. Grafting efficiencies are estimated to range from 74 to 90%. Ungrafted oligo‐PHB and other by‐products are readily removed. Structure assignments were supported by IR,1H‐NMR, GPC, DSC and model compound studies. The method appears capable of grafting oligo‐PHB side chains to any pyridine soluble oligomer or polymer having carboxyl groups and no other reactive groups that could interfere.
Kinetics of crosslinking reactions. 2. Reaction rates of intermolecular and intramolecular crosslinkings by using a soluble microgel
Authors: Ishizu Koji , Nunomura Masataka , Fukutomi Takashi 
Published: April 2003

AbstractSoluble microgels with several pendant vinyl groups were synthesised by radical copolymerization of methyl methacrylate (MMA) with p‐divinyl benzene (p‐DVB). The competitive reactions of intermolecular and intramolecular crosslinkings of these microgels were carried out at 40°C in the presence of 1‐buten‐3‐ol as a degradative chain transfer agent. The rate constant of intermolecular crosslinking (k) was estimated by GPC (gel permeation chromatography) analysis on the polymer produced from intermolecular propagation between bimolecules. The k depended strongly on the internal structure of microgels. Network formation was discussd inclusive of informations for the rate constant of intramolecular crosslinking (k).
Plasma polymers from chloromethyltrimethylsilane and their modification with sodium azide
Authors: Inagaki N. , Tano Y. 
Published: April 2003

AbstractPlasma polymerization of chloromethyltrimethylsilane (CMTMS) was investigated by elemental analysis, infrared spectroscopy, and ESCA, and the modification of Cl substituents in the plasma polymers from CMTMS with sodium azide was discussed. CMTMS was plasma polymerized to yield filmy polymers. The polymer deposition rate was faster than that from tetramethylsilane containing no Cl atom. The plasma polymers from CMTMS were mainly composed of CH3, CH2, SiCH3, SiOSi, and SiOC groups with a small amount of CCl groups. The Cl substituents incorporated into the plasma polymers were capable of substitution reactions with azide groups to form azide polymers.
Chemical modification of cured MY720/DDS epoxy resins using fluorinated aromatic compounds to reduce moisture sensitivity
Authors: Hu H.‐P. , Gilbert R. D. , Fornes R. E. 
Published: April 2003

AbstractBlocking the hydroxyl, amine, and epoxide functional groups of cured MY720/DDS epoxy thin films with various fluorinated aromatic reagents reduces the equilirium moisture absorption by as much as 75%. The blocking reactions were temperature‐, time‐, and diffusion‐dependent. 2,4‐Difluorophenyl isocyanate was a more effective blocking reagent than trifluoromethylphenyl isocyanates (i.e., ortho‐, meta‐, and para‐) due to its higher reactivity. Among the trifluoromethylphenyl isocyanates, meta‐trifluoromethylphenyl isocyanate exhibited the greatest extent of reaction based on the reduction of IR peaks at 3400 and 904 cm−1, presumably due to the slightly poorer inductive effect inherent in meta‐trifluoromethylphenyl isocyanate, permitting a greater extent of diffusion into the bulk polymer. Pentafluorobenzoyl chloride was a more efficient blocking reagent compared to the fluorinated aromatic isocyanates. DSC thermogram data indicated that reaction of pentafluorobenzoyl chloride at 90°C for 2 days with the epoxy groups was essentially complete. The treated films were stable to hydrolysis even after immersion in distilled water at room temperature for 2 months as measured by IR spectroscopy.
Polymerization of silicon‐containing acetylenes. 5. Polymerization of 1‐silyl‐1‐propynes by TaCl5‐based catalysts
Authors: Masuda Toshio , Isobe Eiji , Hamano Toshiyuki , Higashimura Toshinobu 
Published: April 2003

AbstractPolymerization of homologues of 1‐(trimethylsilyl)‐1‐propyne [CH3CCSi(CH3)3] was studied. CH3CCSi(CH3)2(n‐C6H13) (I) polymerized with 1 : 1 mixtures of TaCl5 and organometallic cocatalysts (e.g., Ph4Sn and Ph3Bi) to produce in good yields a polymer having a weight‐average molecular weight (Mw) over 1 × 106. CH3CCSi(CH3)2 Ph (II) and CH3CCSi(C2H5)3 (III) formed polymers having Mw's of ∼ 5 × 105 in moderate yields in the presence of TaCl5‐based catalysts. In contrast, none of CH3CCSi(CH3)2(i‐C3H7), CH3CCSi(CH3)2(t,‐C4H9), C2H5CCSi(CH3)3, and n,‐C4H9CCSi(CH3)3 polymerized, which is attributed to the steric effect of the monomers. Some other 1‐silyl‐1‐propynes also failed to polymerize. The three new polymers formed from (I)–(III) had the structure \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [{\rm CCH}_{\rm 3} \hbox{=\hskip-2pt=} {\rm C(SiRR'R''}\rlap{--} ]_n$\end{document} according to IR and 13C‐NMR spectra. They were white solids, soluble in low‐polarity solvents (e.g., toluene and chloroform) and stable enough in air at room temperature.
The effect of temperature and initiator levels on the dispersion polymerization of polystyrene
Authors: Ober Christopher K. , Hair Michael L. 
Published: April 2003

AbstractConsiderable interest has been generated recently by the preparation of large monodisperse polymer latices by a multistage swelling process. Dispersion polymerization in organic media has been shown to be an alternative route to the preparation of large monodisperse polymer colloids. The size of the resulting particles is known to be dependent on the polarity of the reaction medium. Several other factors are also extremely important in determining both the size and size distribution of the resulting particles. These include the temperature of the reaction and the level of initiator. The temperature affects both the rate of free radical formation and the thermodynamic properties of the polymerization system. It is shown that monodispersity can be achieved over a considerable range of temperatures provided that a particular level of initiator is used at a given temperature. It is also shown that higher levels of initiator at a particular temperature actually produced larger particles. Interestingly, the level of initiator was not found to significantly change the overall rate of polymerization.
Synthesis of copoly(vinylamine‐vinylalcohol) containing two kinds of asymmetric nucleic acid base derivatives as grafted pendants
Authors: Overberger C. G. , Lu C. X. 
Published: April 2003

AbstractPreparation of new model polymers of polynucleotides with poly(vinylamine‐vinylalcohol) [P(Vam‐Val)] backbones and different kinds of nucleic acid base derivatives as grafted pendants is described. At first, the grafting of (−) and (±)‐2‐(thymin‐1‐yl)propionic acid [(−) and (±)TPA] onto linear P(Vam‐Val) at the amino group via an amide bond was carried out in a mixed solvent of ethanol‐dimethylformamide by selective N‐acylation of the active ester of N‐hydroxy‐5‐norbornene‐2,3‐dicarboximide (HONB) or N‐hydroxysuccinimide (HOSu). This procedure gave the corresponding hydroxyl polymers P[Vam(−)T‐Val] and P[Vam(±)T‐Val]. In addition, direct, low temperature esterification was used to graft (−), (±)TPA, and (±)‐2‐(uracil‐1‐yl)propionic acid, [(±)UPA], onto the hydroxyl polymer at the hydroxyl group via an ester bond. This process gave the corresponding copoly(Vam‐Val) with different or the same kinds of nucleic acid base derivatives. P[Vam(−)‐Ve(−)T], P[Vam(±)T‐Ve(±)T], P[Vam(−)T‐Ve(±)U], and P[Vam(±)T‐Ve(±)U] are representative examples. The related monomer and segmental model compounds were also prepared by this method; 3‐aminopentane, 3‐pentanol, 3‐amino‐1‐propanol, and threo‐2‐amino‐4‐pentanol were employed in the syntheses. The segment models were separated and purified using HPLC techniques.
Asymmetric polymerization of triphenylmethyl methacrylate by C2‐chiral catalysts
Authors: Kanoh Shigeyoshi , Kawaguchi Naotaka , Sumino Takeshi , Hongoh Yukihiko , Suda Hiroshi 
Published: April 2003

AbstractAsymmetric polymerization of triphenylmethyl methacrylate (TrMA) was investigated with optically active anionic catalysts in toluene at −78°C. The catalysts were prepared in various combinations of organolithium compounds with C2‐chiral tertiary diamines (1–6). Tetramethyl‐ethylenediamine derivative bearing an axially dissymmetric biphenyl moiety (1) and the binaphthyl analogue (4) were found to provide efficient catalysts for the preparation of highly isotactic poly(TrMA)s of very large optical rotations whose signs depended on the configurations of the diamines. Especially, the catalysts consisting of 1 gave nearly pure one‐handed helical polymers soluble in tetrahydrofuran (THF) in excellent yields, regardless of the kind of the lithium compounds used. The BuLi‐1 catalyst caused the metallation of toluene used as the solvent, and hence the resulting polymer had a benzyl moiety as an initiator fragment. The polymerization was also discussed with respect to the mole ratio of 1 to BuLi. Circular dichroism (CD) spectra of the (−)‐ and (+)‐polymers, which were obtained with the BuLi‐(R)‐1 and ‐(S)‐1 catalysts, respectively, were virtually complete mirror images of each other. High performance liquid chromatography (HPLC) using the THF–soluble, optically active poly(TrMA) as chiral adsorbent realized the complete resolution of racemic compounds.
Relationship between ion conductivity and morphology of complexes formed from poly(ethylene oxide) and potassium thiocyanate
Authors: Tada Hiroaki , Yano Yu‐Ichi , Fujino Kozo , Kawahara Hideo 
Published: April 2003

AbstractSolid polymer electrolytes with different stoichiometries were prepared from molten poly(ethylene oxide) (PEO) containing various amounts of potassium thiocyanate (KSCN). X‐ray diffraction and conductivity measurements revealed that both morphology and conductivity were dependent on their stoichiometries, and that the highest conductivity at ambient temperature corresponded to 3.98 × 10−6 S cm−1 for the amorphous complex with the composition of X = 0.15 (X = [KSCN]/[EOunit]). The temperature dependence of the conductivity showed a WLF‐type behavior for the amorphous complex, whereas it showed an Arrhenius‐type behavior for a crystalline complex with the composition of X = 0.2. It was also found that the ionic mobility at 60°C of the amorphous complex was approximately 2.25 times greater than that of the crystalline complex. Furthermore, results of the infrared reflection spectroscopy measurements suggested that the mobility of potassium ion (K+) was correlated to the degree of the interaction between K+ and ether oxygens.
Ethylene homopolymerization with P, O‐chelated nickel catalysts
Authors: Klabunde U. , Mulhaupt R. , Herskovitz T. , Janowicz A. H. , Calabrese J. , Ittel S. D. 
Published: April 2003

AbstractAbstraction of phosphine from the nickel(II) P, O‐chelated complexes, Ni[Ph2PCHC(Ph)O] (Ph)(PPh3), and related species converts them from olefin oligomerization to olefin polymerization catalysts. Phosphine acceptors such as Rh(acetylacetonate)(C2H4)2 or Ni(1,5‐cyclooctadiene)2 are most effective. Alternatively, nickel complexes in which the phosphine ligand is replaced with weakly coordinated pyridine can be prepared. These active, homogeneous catalysts can be tuned to give either low or high molecular weight, linear low or high density polyethylene. Depending on the diluent, the same catalytic complex can be used as heterogeneous or homogeneous catalyst. They are tolerant of oxygenated, hydroxylic, or polar molecules that would poison normal early transition metal‐based Ziegler‐Natta catalysts. In fact, the polymerizations can be run in solvents such as ethanol or acetone, but hydrocarbon solvents are preferred.
Curing studies of a polyimide precursor
Authors: Brekner M.‐J. , Feger C. 
Published: April 2003

AbstractComplexes between diphenylcarbamido‐dicarboxybenzene and 1‐methyl‐2‐pyrrolidinone, 1/4 and 1/2 M, are obtained by reacting pyromellitic dianhydride with aniline in the solvent 1‐methyl‐2‐pyrrolidinone. Decomplexation and imidization of this diamic acid are studied by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectrometry, polarizing microscopy, and gas chromatography/mass spectrometry. Side reactions competing with the imide formation are discussed. The presence of solvent is found to markedly influence imidization.
Polyaddition of p‐benzenedithiol to p‐diethynylbenzene in solid state under UV irradiation
Authors: Kobayashi Eiichi , Ohashi Toyoshi , Furukawa Junji 
Published: April 2003

AbstractA novel polyaddition of p‐benzenedithiol (BDT) to p‐diethynylbenzene (DEB) was studied in solid state under UV or γ‐ray irradiation at 25–99°C. Thin layer crystals of the 1:1 mixture of BDT and DEB mounted on a glass plate were prepared by a sublimation of an equimolar amount of the mixture of BDT and DEB at 45–80°C under a reduced pressure of nitrogen.The thin layer crystal of the 1:1 mixture of BDT and DEB and that of polymers exhibited almost similar and high crystalline diffraction patterns on x‐ray diagraph. Consequently, the polyaddition in the solid state was a topotactic reaction controlled by the crystal lattice of the 1:1 mixture of BDT and DEB. The arrangement of both compounds in the thin layer crystal of the 1:1 mixture of BDT and DEB is seemingly quite ordered induced by a molecular interaction between BDT and DEB, and this is supported on the basis of the broad absorption at 340–450 nm by the diffuse reflectance spectrum taken with the thin layer crystal of the 1:1 mixture of BDT and DEB.The melting point of the 1:1 mixture of BDT and DEB was 90–94°C. However, the polyaddition at 87°C proceeded in a molten state perhaps due to heat evolved in the polyaddition. In the solid state polyaddition Mn of polymers obtained was 3–4 × 103, whereas in the molten state polyaddition the crystallinity of polymers remarkably decreased, and Mn increased several times.
Rhodium(I) catalyst supported on polymer crystal surfaces: Further hydrogenation studies
Authors: Gordon Bernard , Butler Jacqueline S. , Harrison Ian R. 
Published: April 2003

AbstractCatalysts bound to polymers in the form of crosslinked beads have been demonstrated to have a number of advantages over homogeneous catalysts. However, there are several problems that exist due to the polymer support being in the form of a bead. The rate of reaction depends on the presence of solvents that adequately swell the bead in order to allow access to the catalytic sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed whereby tris(triphenyl phosphine) chlororhodium (I) (Wilkinson's catalyst) is bound to the surface of polyethylene single crystals. Polyethylene single crystals have a very high surface to volume ratio allowing for greater ease of reaction compared to a bead system. In a previous paper we showed that there is a dramatic increase in catalytic activity and that the reaction rate increased as the polarity of solvent was increased, even in ethanol where the homogeneous catalyst is not soluble and the polystyrene bead support would not swell. In this letter we are describing the activity of hydrogenation of olefins contained in both large and/or polar molecules. The results demonstrate the advantages of supported catalysts on polyethylene single crystals rather than on polymer beads.
Poly(iminomethylene) copolymers
Authors: King R. B. , Borodinsky L. , Greene M. J. 
Published: April 2003

AbstractCopolymerization of an isocyanide giving an insoluble homopolymer with another isocyanide giving a soluble homopolymer in ethanol solution using 0.5–1% of a nickel (II) catalyst in many cases gives a soluble copolymer containing pendant groups arising from both isocyanides. Thus, methyl isocyanide, which gives an insoluble homopolymer, gives chloroform‐soluble copolymers incorporating 39–44% of pendant methyl groups when copolymerized with equimolar amounts of tert‐butyl isocyanide or several aryl isocyanides. Similarly, cyclohexyl isocyanide, which also gives an insoluble homopolymer, gives chloroform‐soluble copolymers incorporating 43–59% of pendant cyclohexyl groups when copolymerized with equimolar amounts of several aryl isocyanides. The compositions, chloroform solubilities, and polystyrene equivalent molecular weights are given for 33 different copolymers obtained by copolymerizations of various equimolar binary mixtures of the monomers CH3NC, (CH3)3CNC, cyclo‐C6H11NC, C2H5NC, CH3CHCHNC,(CH3)2CCHNC, 2,4,6‐(CH3)3C6H2CHCHNC, C6H5CH(CH3)NC, CH2CHNC, (CH3)3CCHCHNC, C6H5NC, 2‐ and 4‐CH3C6H4NC and 2‐, 3‐, 4‐CH3OC6H4NC using the nickel (II) catalyst system.
A mechanistic study of polyimide formation from diester‐diacids
Authors: Johnston James C. , Meador Mary Ann B. , Alston William B. 
Published: April 2003

AbstractPrevious work by a number of researchers has noted the presence of anhydride during the imidization step of polyimide polymer processing from diester‐diacids and diamines. This has been often, and incorrectly, dismissed as being due to the reversion of the intermediate amide‐acid. Comparison of the relative rates of reactions among model compounds demonstrates the intermediacy of anhydride in the imidization reaction. When creation of the anhydride is blocked, the production of amide‐acid is greatly slowed. Infrared and NMR observations of mixtures of monomers confirm the production of anhydride as a necessary intermediate in the imidization reaction occuring during the production of polyimide polymers from diester diacids.
Polyarylates. III. Kinetic studies of interfacial polycondensation
Authors: Tsai Hong‐Bing , Lee Yu‐Der 
Published: April 2003

AbstractThe kinetics of interfacial polycondensation of bisphenol A with isophthaloyl chloride and terephthaloyl chloride in dichloromethane with triethylbenzylammonium chloride (TEBAC) as the catalyst was investigated via measurements of bisphenolate concentration by UV. The reaction was found to be second order with respect to bisphenolate. The dependence of the rate constant on stirring speed, amount of TEBAC, and reaction temperature was studied. The rate constant was increased with an increase of stirring speed, quantity of TEBAC added, as well as the reaction temperature. The activation energy was found to be 7.7 kcal/mol at a stirring speed of 700 rpm in the presence of 0.160 of TEBAC. The role of TEBAC was found to be interesting. It did not alter the equilibrium (the partition coefficient remained the same in the presence of TEBAC), but it did enhance the transfer rate of bisphenolate.
Interpenetrating polymer networks from castor oil‐based polyurethanes and poly(methyl methacrylate). V
Authors: Patel Mayur , Suthar Bhikhu 
Published: April 2003

AbstractCastor oil is reacted with hexamethylene diisocyanate under different experimental conditions varying the NCO/OH ratio to yield liquid prepolyurethanes (PPU's). All these polyurethanes were interpenetrated with methyl methacrylate (MMA) and a crosslinker EGDM by radical polymerization initiated by benzoyl peroxide. The novel PPU/MMA interpenetrating polymer networks (IPN's) were obtained as tough films by transfer molding. The characterization of these IPN's includes resistance to chemical reagents, thermal behavior (DSC, TGA), and the mechanical properties, namely, tensile strength, modulus of elasticity, elongation at break (%), and hardness. The morphological behavior (SEM) and dielectrical properties such as electrical conductivity, dielectric constant (ε′), dielectric loss (ε″), and loss tangent (tan δ) were estimated.
FT–IR spectroscopic study on the photo‐ and photooxidative degradation of nylons
Authors: Do C. H. , Pearce E. M. , Bulkin B. J. , Reimschuessel H. K. 
Published: April 2003

AbstractThe progress of photo‐ and photooxidative degradation of nylon films were studied by FT–IR spectroscopy. The gases evolved from the photolysis of various nylons and their model amides were also analyzed. The formation of double bonds, changes of crystallinity, and the effect of amino and carboxyl end groups has been studied and discussed. The band shapes of the IR spectra pertaining to the carbonyl groups formed by thermal oxidation or photooxidation were found to be very similar, suggesting that the two oxidation mechanisms might be similar. The broadness of these bands indicates that the carbonyl groups may belong to more than one species. The photodegradation of nylons containing purposely inserted carbonyl groups formed CHCH2 groups. Carbonyl groups formed during oxidation, and present either as keto groups or part of N‐acylamide units make nylons susceptible to degradation reactions entailing mainly a Norrish type II mechanism.
Use of aromatic dialdehydes in the preparation of poly(p‐benzoquinono)diimidazoles
Authors: Karayannidis G. P. , Sideridou‐Karayannidou I. 
Published: April 2003

AbstractPoly(p‐benzoquinono)diimidazoles have been synthesized under mild conditions (100 or 150°C) by one‐stage polycondensation in N,N‐dimethylacetamide (DMAc) or in polyphosphoric acid of 2,3,5,6‐tetraamino‐p‐benzoquinone (TABQ) with terephthalaldehyde and isophthalaldehyde. The model compound 2,6‐diphenyl‐1,5‐dihydro‐1′,4′‐benzoquinono[2′,3′‐d:5′,6′‐d′]diimidazole was also prepared by condensation of TABQ with benzaldehyde in DMAc at 100°C. The prepared polymers were completely insoluble in organic solvents but slightly soluble (0.5%) in strong acids with viscosities (ηinh) in the range of 0.17–0.38 dL/g (c = 0.2% in formic acid). Their thermal stability was studied by TG analysis.