bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft polymerization of acrylic monomers onto starch fractions. IV. Effect of reaction time on the grafting of butyl acrylate onto amylose
Authors: Vazquez M. B. , Goñi I. , Gurruchaga M. , Valero M. , Guzman G. M.
Published: April 2003

Studies were carried out on the grafting of butyl acrylate (BA) to amylose by the ceric ion method. After removing the homo‐PBA with THF and toluene, and the ungrafted amylose with 0.5NNaOH, the PBA content of the graft copolymers was determined by acid hydrolysis with 1N HCl. The influence of reaction time on the grafting yields was determined and the largest values were: 82% for the grafting efficiency, 246% for the percent grafting, 62% for the grafted amylose, 48% for the grafted PBA, and 64% for the total conversion.
The synthesis of biodegradable polymers with functional side chains
Authors: Pitt Colin G. , Gu Zhong‐Wei , Ingram Peter , Hendren R. Wayne
Published: April 2003

Trifunctional hydroxy‐terminated oligomeric polyesters, Mn 500, 1000, and 2000, were prepared by initiating ring‐opening copolymerization of δ‐valerolactone and ε‐caprolactone with glycerol. The prepolymers were converted to crosslinked polyester‐urethanes by their reaction with hexane‐1,6‐diisocyanate in proportions corresponding to 70, 80, 90, and 100% of the hydroxyl content. The moduli of the resulting elastomers varied between 0.12 MPa and 3.83 MPa, and the elongation at break between 60 and 2000%. The residual hydroxyl groups were derivatized by heterogeneous reaction with chloroacetic anhydride or excess hexane‐1,6‐diisocyanate, and these and further transformations of the functional groups were verified by infrared spectroscopy and electron probe x‐ray microanalysis. A second series of hydroxy‐substituted elastomers was synthesized by copolymerization of δ‐valerolactone, ε‐caprolactone, and 4‐(t‐butyldimethylsilyloxy)‐ε‐caprolactone, using different amounts of 2,2‐bis(caprolacton‐4‐yl)propane as the crosslinking agent; removal of the t‐butyldimethylsilyl group to liberate pendant hydroxyl groups was achieved with acetic acid but not fluoride ion. The hydroxylated polyester (but not the polyesterurethanes) was shown to undergo enzymatic surface erosion in rabbit. The biodegradation data were compared with results previously obtained with low‐modulus elastomeric polyesters.
o‐nitrovinylbenzaldehyde polymers: Precursors of photosensitive acetals
Authors: Kamogawa Hiroyoshi , Takei Mitsuhiko
Published: April 2003

2‐Nitro‐3‐vinyl, 2‐nitro‐5‐vinyl, and 4‐nitro‐3‐vinylbenzaldehydes were synthesized starting with the corresponding dimethylnitrobenzenes via brominations of the two methyl groups, subjection of one of the resulting two bromomethyl groups to the Wittig reaction, and further subjection of the remaining one to the Kröhnke reaction.

An attempt to prepare 2‐nitro‐4‐vinylbenzaldehyde (21) from the 2‐nitro‐4‐vinylaniline (19), synthesized starting with 2‐nitro‐4‐methylaniline following the same vinylation procedure, failed.

The three nitrovinylbenzaldehydes and 19 were polymerized with AIBN in the conventional manner to afford low molecular weight polymers in low conversions. The polymer of 19 was then converted to the 21 polymer. All nitrobenzaldehyde polymers were converted to acetals with ethylene glycol and 2‐hydroxyethyl salicylate and the latter in benzene solutions were irradiated with UV to afford the o‐nitrosobenzoate polymers with half‐cleavages of the alcohol residues.
Polymerization of phenylacetylene using palladium (II) catalysts
Authors: Trumbo D. L. , Marvel C. S.
Published: April 2003

Poly(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

Polymers 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

A 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

Soluble 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

Plasma 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

Blocking 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

Polymerization 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

Considerable 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

Preparation 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

Asymmetric 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

Solid 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

Abstraction 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

Complexes 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

A 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

Catalysts 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

Copolymerization 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

Previous 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

The 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

Castor 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

The 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

Poly(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.
Effect of N‐methyl substitution on the thermal decomposition processes in aliphatic–aromatic polyamides
Authors: Ballistreri Alberto , Garozzo Domenico , Montaudo Giorgio , Giuffrida Mario
Published: April 2003

The thermal decomposition processes of two polyamides, derived from succinic acid and two aromatic diamines, were studied by direct pyrolysis mass spectrometry.

Fast atom bombardment (FAB) mass spectrometry has been also used in order to provide additional information for the elucidation of the thermal degradation mechanism of the polymers investigated. FAB mass spectra, obtained by introducing in the FAB ion source the solid residues from polymer pyrolysis performed in thermogravimetric experiments, allowed the detection of diagnostic compounds up to about 1600 amu.

Our results indicate that the thermal stability of the N‐methyl‐substituted polyamide is higher than that of the unsubstituted polyamide. The difference in the thermal degradation mechanism accounts for the difference in the thermal stability of the two polyamides. In fact, the unsubstituted polyamide decomposes via an intramolecular exchange and a concomitant NH hydrogen transfer process with formation of compounds with amine and/or succinimide end groups. Instead, the N‐methyl‐substituted polyamide decomposes via an α CH hydrogen transfer process from the methyl group to the nitrogen atom with formation of compounds with amine and/or 2,5‐piperidinedione end groups.
FT–IR spectroscopic study on the thermal and thermal oxidative degradation of nylons
Authors: Do C. H. , Pearce E. M. , Bulkin B. J. , Reimschuessel H. K.
Published: April 2003

The effects of heat and oxygen on nylon films were studied by FT–IR spectroscopy. Nylons 6, 66 and nylons containing carbonyl groups in either the diamine or the diacid moiety were prepared. Nylon films cast on aluminum were studied in an environmental chamber under controlled conditions. The progress of chemical and physical changes was monitored by FT–IR spectroscopy. Thermal energy caused largely an increase in crystallinity due to annealing and also an increase of nonhydrogen‐bonded amide groups, which seemed to entail mainly amide groups from the amorphous region. The intensities of IR absorption bands related to the folded structure reduced as soon as heating began. The IR spectra of the carbonyl groups formed by thermal oxidation showed band shapes that indicated that the formed carbonyl groups were of many different origins. The presence of keto groups purposely inserted into the backbone chains increased the rate of oxidation. Pyrolysis of the nylons was also studied to supplement data obtained at lower temperatures.
Liquid crystalline polymers containing heterocycloalkane mesogens. 2. Side‐chain liquid crystalline polysiloxanes containing 2,5‐disubstituted‐1,3‐dioxane mesogens
Authors: Hsu C. S. , Rodriguez‐Parada J. M. , Percec V.
Published: April 2003

Polysiloxanes and copolysiloxanes containing 2‐(p‐hydroxyphenyl)‐5‐(p‐methoxyphenyl)‐1,3‐dioxane and 5‐(p‐methoxyphenyl)‐1,3‐dioxan‐2‐yl as mesogenic units and an aliphatic spacer containing 11 and 10 methylene units, respectively, were synthesized. Their phase behavior was studied by differential scanning calorimetry and optical polarization microscopy, and compared with the phase behavior of the polysiloxanes and copolysiloxanes containing 4‐methoxy‐4′‐hydroxybiphenyl and 4‐cyano‐4′‐hydroxybiphenyl mesogens attached to the polymer backbone through an aliphatic spacer containing 11 methylene units. All synthesized polymers present smectic mesomorphism. The polymers containing 4‐methoxy‐4′‐hydroxybiphenyl and 4‐cyano‐4′‐hydroxybiphenyl are also crystalline, while the polymers containing 1,3‐dioxane based mesogens do not crystallize.
Polymer‐supported bases. 7. Nucleophilic acyl rearrangements catalyzed by polymer‐supported aminopyridine or imidazole bases
Authors: Tomoi Masao , Arita Yasushi , Kakiuchi Hiroshi
Published: April 2003

Polymer‐supported aminopyridine or imidazole catalysts were effective for acyl rearrangements of O‐acylated substrates to C‐acylated products. Some of the aminopyridine catalysts, which had much higher activity than the imidazole catalyst, exhibited high activity comparable to that of the corresponding soluble catalyst, 4‐N, N‐dimethylaminopyridine. The activity of the immobilized aminopyridines was studied as a function of the percentage of ring substitution, spacer‐chain length, and solvents. The affinity of the substrates for the immobilized catalysts played an important role for the rearrangements. The increased catalytic activity resulted from the increased affinity of the substrates for the catalysts. The activity of the immobilized bases decreased gradually owing to the reaction of the active site with the products as the catalysts were used repeatedly. The treatment of the used catalysts with nucleophiles restored the activity to some extent. The activity decrease can be minimized by shortening a contact time between the catalysts and the products.
Enantioface differentiation by chiral polymers having (+)‐5,6‐exo‐bornanediol moieties. II. Asymmetric reduction of prochiral ketones by chiral polymers containing (+)‐5,6‐exo‐bornanediol derivatives
Authors: Liu Jui‐Hsiang , Lin Shyuh‐Rurng , Kuo Jue‐Cheng
Published: April 2003

The asymmetric reduction of prochiral aromatic ketones with modified reagents prepared from sodium borohydride and carboxylic acids in the presence of both chiral polymers and relating low molecular weight compounds having (+)‐5,6‐exo‐dihydroxybornyl derivatives was carried out. The enantioface differentiation took place effectively by raising the reaction temperature, and the highest enantiomeric excess was achieved at 10°C (24.3%) in the presence of the chiral polymers. A higher optical yield (87.8%) can be obtained in the asymmetric reduction by using the low molecular weight (+)‐5,6‐exo‐diol compounds. The effect of the reaction temperature, solvents, and the advantages of the chiral polymer‐bound reagents were also discussed.
The influence of molecular weight on the reactivity of a vinylbenzyl ether macromonomer of poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Mühlbach Klaus , Percec Virgil
Published: April 2003

The synthesis of a series of vinylbenzyl ether macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO–VBE) with number average molecular weights between 1,000 and 27,000 and narrow molecular weight distribution is presented. The reactivity ratio r1 was determined for the comonomer pairs methyl methacrylate (MMA) and butyl methacrylate (BMA), respectively (M1), and PPO–VBE (M2) over the entire range of molecular weights of the macromonomer. r1 was determined by the single experiment intergrated equation. Since both the monomer and macromonomer present an induction period, it has been shown that the determination of r1 from one single point experiment is not correct. Accurate r1 values can be obtained from one single copolymerization experiment only when the comonomer conversions are determined at several different reaction times. The macromonomer reactivity (1/r1) increases with its molecular weight up to about 5,000–7,000. Above these values its reactivity decreases. An attempt to explain this behavior based on the kinetic excluded free volume effect is presented.
A new synthesis of 1,5‐dioxepan‐2‐one
Authors: Kafrawy Adel , Shalaby S. W.
Published: April 2003

A new method for the synthesis of 1,5‐dioxepan‐2‐one (DXO)1 was developed and advantages over an earlier synthetic scheme2 were documented.
Synthesis and properties of new polybenzimidazoles and N‐phenyl polybenzimidazoles with flexibilizing spacers on the polymer backbone
Authors: Scariah K. J. , Krishnamurthy V. N. , Rao K. V. C. , Srinivasan M.
Published: April 2003

Several new polybenzimidazoles (PBIs) and N‐phenyl PBIs were synthesized by high temperature solution polycondensation techniques. Three different tetramine hydrochlorides and one N‐phenyl tetramine hydrochloride were condensed independently with p‐phenylenedioxydiacetic acid (PDDA), 2,2′‐[isopropylidene bis(p‐phenyleneoxy)] diacetic acid (bisacid A2) and 2,2′‐[sulfonyl bis(p‐phenyleneoxy)] diacetic acid (bisacid S) in polyphosphoric acid (PPA) at high temperatures. The polymers were obtained in 55–65% yield with inherent viscosities in the range 0.58–0.96 dL/g. Four model benzimidazoles (MBI) were also synthesized to confirm the formation of polybenzimidazoles. The PBIs and MBIs were characterized by infrared spectroscopy and elemental analysis. The properties of the polymers such as solubility, density, crystallinity, and thermal, thermoxidative, and isothermal stabilities were studied.
High performance polymers and composites. IV. Copolymers containing benzoxazole units
Authors: Mathias Lon J. , Livant Peter D. , Ahmed Sharf U.
Published: April 2003

Several new copolymers have been synthesized. Initial polycondensation of mixtures of aryl and arylalkyl carboxylic acids containing aromatic hydroxyl and amine substituents led to random copolyamides. Thermal cyclization of these prepolymers (inherent viscosities of about 0.2 dL/g) gave copolybenzoxazoles with inherent viscosities of about 1.4 dL/g. Thermal stability as measured by TGA was similar for the 1:1 copolymers and the homopolymers containing hydrocinnamic units; i.e., catastrophic decomposition occurred at 450°C. Copolymers with lower ratios of the hydrocinnamic units displayed greatly improved thermal stability while maintaining good molecular weight.
Synthesis and characterization of liquid crystalline polysiloxanes containing benzyl ether mesogens
Authors: Hsu C. S. , Percec V.
Published: April 2003

Side chain liquid crystalline polysiloxanes were synthesized by the hydrosilation of poly(methylhydrosiloxane) with p‐(1‐undecenyl‐11‐oxy) benzyl ethers of 4‐cyanophenol (IM), 4‐methoxyphenol (IIM), 4‐cyano‐4′‐hydroxybiphenyl (IIIM), 4‐methoxy‐4′‐hydroxybiphenyl (IVM), and 2‐cyano‐6‐hydroxynaphthalene (VM). The phase behavior of both monomeric and polymeric liquid crystals was characterized by differential scanning calorimetry and optical polarization microscopy. IM is a monotropic liquid crystal, IIM is crystalline, and IIIM and IVM are enantiotropic liquid crystals, whereas VM presents two virtual liquid crystalline transitions and crystalline polymorphism. All the synthesized polysiloxanes present enantiotropic smectic mesomorphism.
Uniform encapsulation of fine inorganic powder with soapless emulsion polymerization
Authors: Hasegawa Masahiro , Arai Kunio , Saito Shozaburo
Published: April 2003

The encapsulation of inorganic powder of submicron sizes was attempted with soapless emulsion polymerization of methyl methacrylate in water in the presence of the powder. The powders used were barium sulfate and calcium carbonate. The polymerizations were initiated by potassium persulfate and by sodium bisulfite‐oxygen redox reaction. The encapsulation state of the powder with the polymer formed varied considerably with the initiators used. With potassium persulfate initiator the powder surface was partially or totally covered by polymer particles, while with redox initiator under air atmosphere the powder surface was well encapsulated with a film‐like polymer layer. From the differences in the encapsulation states, an encapsulation mechanism is suggested for each initiator system. Based upon this mechanism, a new encapsulation process capable of covering uniformly fine powders with a film polymer is proposed. An important factor in the new process is the addition of an extremely small quantity of a surfactant into the reaction system prior to the polymerization.
Benzocyclobutene in polymer synthesis. II. Solid state diels–alder polymerization utilizing an in situ generated diene and an alkyne
Authors: Tan Loon‐Seng , Arnold Fred E.
Published: April 2003

A novel class of aromatic imide AB‐monomers with benzocyclobutene and an alkyne (primarily phenylethynyl group) as the reactive units have been prepared. The monomers have been utilized in thermally induced Diels–Alder polymerizations. The differential scanning calorimetric study of the AB‐monomers provided two observations: (i) primary acetylene began its homopolymerization (202°C max.) before the electrocyclic ring opening of benzocyclobutene (270°C max.); (ii) the phenoxy group connecting between phenylacetylenyl group and the aromatic imide fragment suppressed polymerization in Diels–Alder fashion. Furthermore, thermoxidative stability evaluation on the cured samples (250°C for 8 h and then 350°C for another 8 h under N2 atmosphere), carried out at 650°F (air) for 200 h, indicated the more rigid phenylethynyl phthalimide system was the most heat‐resistant.
Synthesis and characterization of poly([3H]‐thiazole‐2‐thione)s
Authors: Katritzky Alan R. , Tarr Richard D. , Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R.
Published: April 2003

The reaction of dithiocarbamate salts with α‐haloketones is extended to (i) dithiocarbamate salts with bis(α‐haloketones), (ii) bis(dithiocarbamate salts) with α‐haloketones, and (iii) bis(dithiocarbamate salts) with bis(α‐haloketones). Both (i) and (ii) give bis([3H]‐thiazole‐2thiazole‐2‐thiones) in high yields, and (iii) gives the corresponding polymers which are described and characterized.
Effect of surfactant adsorbed on encapsulation of fine inorganic powder with soapless emulsion polymerization
Authors: Hasegawa Masahiro , Arai Kunio , Saito Shozaburo
Published: April 2003

The encapsulation of fine inorganic powder was carried out with the soapless emulsion polymerization of methyl methacrylate in water in the presence of the powder, a layer of surfactant being adsorbed. The powder used was titanium dioxide. Surfactants added prior to the polymerization were sodium dodecyl sulfate, dodecyltrimethyl ammonium bromide, and polyoxyethylene sorbitan mono‐oleate. The encapsulation state of the powder with polymer was closely related to the amount of surfactant adsorbed on the powder; and an amount of adsorption above a certain value was necessary for uniform encapsulation. Ionic surfactants were more useful than nonionic in the surfactants used, and could be adsorbed utilizing the electrostatic interaction between powder and the ionic end group. The combination of electric charges between the ionic end groups of surfactant and initiator was found to influence the molecular weight of capsulating polymer.
The initiation of the free radical polymerization of vinyl monomers by hexakis(arylisocyano) derivatives of chromium (o)
Authors: Hargreaves K.
Published: April 2003

The present paper describes studies carried out to determine the effect of structure on the free radical polymerization of vinyl monomers initiated by means of the hexakis(arylisocyano) derivatives of chromium (o) in which chlorine, methoxy, and methyl groups have been substituted into different positions of the benzene ring.

The kinetics of the initiation reactions resembles that studied in detail for the parent compound hexakis(phenylisocyano) chromium (o). The observed changes in the initial rates of the polymerization of methyl methacrylate at 80°C in the presence of carbon tetrachloride can be accounted for by the electronic effects associated with these substituents. However, when steric overcrowding occurs, the initial rates of polymerization are reduced considerably.

The results obtained confirm the mechanism of initiation proposed earlier in which the rate determining step is the Sn2 displacement of an arylisocyano ligand by a monomer or reactive solvent molecule. An attempt has been made to explain the increased rate of radical formation observed when chlorine is substituted into the benzene ring.
Synthesis and properties of polyamides derived from systematically halogenated terephthalic acids with fluorine, chlorine, or bromine atoms
Authors: Nagata Minoru , Tsutsumi Naoto , Kiyotsukuri Tsuyoshi
Published: April 2003

Aromatic polyamides were prepared from systematically halogenated terephthalic acids with hexamethylene diamine, piperazine, 4,4′‐diaminodiphenylether and p‐phenylene diamine by interfacial or low temperature solution polycondensation. The halogenated terephthalic acids used have mono‐, di‐, or tetra‐substituted fluorine, chlorine, or bromine atoms on the benzene ring. The nonhalogenated terephthalic acid was also used for the comparison. The effects of halogen substitution on the benzene ring on the synthesis and some properties of polymers were examined. Reduced specific viscosity decreased in the order F > Cl > Br by halogen substitution. The incorporation of halogen substituents on the ring led to a decrease of crystallinity and fluoro‐substituents hindered the crystallization more strongly. The melting point (Tm) decreased in the order F > Cl > Br by mono‐substitution, and Br > Cl > F by di‐and tetra‐substitution. The change of Tm caused by the difference of the number of halogen substituents differed depending on the rigidity of polymer chains. The flame‐retardancy estimated by thermogravimetry, self‐ignition, and flash‐ignition test increased with increasing halogen content of the polymers. Solubility increased remarkably by halogen substitution. The peak temperature of tan δ decreased by halogen substitution. Some discussion was made on these effects of halogen substitution.
Preparation and properties of 1‐ethoxy‐2,2,2‐trifluoroethyl esters of acrylic and methacrylic acids and of their polymers
Authors: Hrabáak F. , Lokaj J. , Bílá J. , Pivcová H. , Tkaczyk M. , Biroš J.
Published: April 2003

1‐Ethoxy‐2,2,2‐trifluoroethyl esters of acrylic (I) and methacrylic (II) acids were synthesized from 1‐ethoxy‐2,2,2‐trifluoroethanol and acryloyl‐ and methacryloylchloride, respectively, and their densities, mass, 1H‐ and 13C‐NMR spectra were measured and the rate constants of hydrolysis were determined. Poly(I) and poly(II) were prepared by radical homopolymerization; the rates of polymerization, specific volume contractions in polymerization, limiting viscosity numbers, average number degrees of polymerization, temperature dependences of the heat capacities both in glass and liquid state, glass transition temperatures, and the initial temperature of the spontaneous thermal decomposition of homopolymers were determined. The monomer reactivity ratios of the styrene (S) copolymerizations, SI and SII, and the Alfrey–Price copolymerization constants e and Q for I and II were calculated from the composition of copolymers of I and II with styrene.
Preparation of polysiloxanes from silicic acid. X. Preparation and properties of allyldimethylsilylated silicic acids
Authors: Abe Yoshimoto , Kaijou Akira , Nagao Yukinori , Misono Takahisa
Published: April 2003

In order to obtain polysiloxanes capable of forming a film, the preparation and properties of allyldimethylsilylated silicic acid was investigated. The reaction in variable molar ratios of allyldimethylchlorosilane to silicic acid gave partially silylated silicic acids with different degrees of silylation. They provided not only fibrous polysiloxanes but also films from concentrated polymer solutions. Spinnability and film formation depended on the solvent, degree of silylation, molecular weight, and allyl group.
Highly active supported catalysts for olefin polymerization: Preparation and characterization of the catalyst
Authors: Yano Takefumi , Inoue Tokuji , Ikai Shigeru , Shimizu Michimasa , Kai Yoshiyuki , Tamura Masanori
Published: April 2003

With use of the support prepared by the reaction1 of a Grignard reagent with reaction mixture of AlCl3 and CH3Si(OC2H5)3, an immobilized active stereospecific titanium catalyst was prepared by the three‐step treatment of the support, first with TiCl4, second with ethylbenzoate, and third with TiCl4 again. The catalyst was also prepared by the two‐step treatment of the support, with the mixture of TiCl4 and ethylbenzoate, and with TiCl4. Solids obtained in each step of the catalyst preparation were characterized by elemental and IR analysis, and their activities for propylene polymerization were determined with triethylaluminum as a cocatalyst under an atmospheric propylene pressure for 1 h at 60°C. The experimental data support the idea that both TiCl4 and ethylbenzoate as donors are immobilized on the surface of the active stereospecific catalyst without any interaction between them.
Copolymerization of trioxane with phenylglycidylether
Authors: Mateva R. , Sirashki G.
Published: April 2003

This study deals with the regularities and peculiarities of the copolymerization of trioxane (TO) and phenylglycidylether (PhGE) in nitrobenzene catalyzed by the cationic initiator BF3Et2O. The additions of PhGE were varied in wide bounds from 5 up to 50 mol %. No data were found about the course of copolymerization process, as well as about the influence of the polymerization conditions on the rate of exhaustion of the monomers and the composition of the copolymer. The effect of the polymerization conditions on the rate of exhaustion of comonomers was established. The kinetics of the process has been followed; the following equation is proposed:

The activation energy was determined to be Eα = 15.3 kcal/mol. The course of copolymerization of TO/PhGE was compared with those of TO/DO, TO/EO, TO/St, and TO/ECH. The variation of comonomer concentrations was measured by gas chromatographic methods. The copolymers were characterized by elemental analysis, IR‐, and NMR‐spectroscopy, as well as by their molecular weights (Mv).