bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydroxy‐terminated poly(ε‐caprolactone‐co‐δ‐valerolactone) oligomers: Synthesis, characterization, and polyurethane network formation
Authors: Storey Robson F. , Herring Kent R. , Hoffman Douglas C. 
Published: April 2003

AbstractDifunctional hydroxy‐terminated poly(ε‐caprolactone‐co‐ε‐valerolactone) (PCV) oligomers were synthesized by the diol‐initiated bulk copolymerization of ε‐caprolactone (C) and δ‐valerolactone (V). The two homopolymers were semicrystalline, with almost identical melting temperatures; copolymerization significantly lowered the melting point (Tm) compared to either homopolymer. Copolymer melting points were found to decrease with decreasing molecular weight and to be dependent on composition, i.e., the incorporation of a comonomer into either homopolymer resulted in a decrease in Tm, with the maximum decrease occurring at a copolymer composition of about 60 mol % ε‐caprolactone. The molar compositions of the copolyesters were determined from 13C‐NMR spectra. The reactivity ratios of the two monomers (M1 = C, M2 = V) were determined to the r1 = 0.25 and r2 = 0.49. Number average molecular weight (M̄n) of the PCV diols was inversely proportional to the initial diol concentration within the studied molecular weight range of 900 to 11,100 g/mol. Crosslinked polyurethane networks were prepared by reacting PCV diols with triphenylmethane triisocyanate. Network characterization included determination of sol content by solvent extraction, glass transition (Tg) and Tm by DSC, and tensile properties by stress‐strain measurements. Completely amorphous networks resulted from PCV diols of M̄n ≤ 2,400; semicrystalline networks resulted from PCV diols of M̄n ≥ 3,600.
Novel platinum‐containing initiators for ring‐opening polymerizations
Authors: Crivello J. V. , Fan M. 
Published: April 2003

AbstractA novel class of platinum‐based initiating systems for the ring‐opening polymerization of a wide variety of heterocyclic compounds including epoxides, oxetanes, and 1,3,5‐trioxane have been discovered. In addition to a platinum complex as a catalyst, a cocatalyst, consisting of a compound or polymer containing silicon‐hydrogen bonds must also be present. This article reports on a preliminary survey of the scope and limitations of these new initiator systems. Particular emphasis in this article has been placed on the ring‐opening polymerization of epoxides which have been studied in some detail and which proceed rapidly and exothermically at room temperature. A number of mechanistic studies have been conducted and the best current evidence suggests that polymerization proceeds by a cationic mechanism. Evidence is also presented which suggests that platinum metal colloids may function as the active initiating species.
Mesomorphic polyacrylates containing isomeric methyl‐substituted azobenzene mesogens
Authors: Angeloni A. S. , Caretti D. , Laus M. , Chiellini E. , Galli G. 
Published: April 2003

AbstractThe synthesis and characterization are reported of two new series of structurally isomeric polyacrylates containing the azobenzene moiety spaced away from the backbone by a hexamethylene spacer and substituted in 4‐position with linear alkoxy groups (C1C6, C10) and with a lateral methyl group in 2′‐ or 3′‐position. Thermal optical and X‐ray analyses of the prepared polymer samples, with molecular weight ranging from 50 × 103 to 35 × 104 Dalton (M̄w/M̄n = 2−3), provide evidences for the establishment of liquid crystalline behavior in the melt in a fairly broad range of temperature. In any case, quenching from the mesophase allows for the lock‐in of the liquid crystalline structure in the glassy state. The presence of the lateral methyl‐substitutents causes a drop as high as 50–100 K. in the stability of the mesophase with respect to the corresponding samples of the methyl‐unsubstituted series. A parallel depletion of the smectogenic character is also observed. Typical even‐odd effects on the isotropization temperature and relevant thermodynamic parameters have been detected along with the formation of interdigitated smectic structures.
Synthesis of monomers containing guanine or guanine precursors as substituent groups
Authors: Toucet Isabel , Aponte Maria A. 
Published: April 2003

AbstractThe synthesis of four new monomers containing guanine or a guanine precursor was achieved. These were two isomeric acid ester derivatives of guanine and two isomeric vinyl ether derivatives of N2‐acetylguanine. In the case of the synthesis of the guanine acid esters IV and V, it was necessary to prepare first the guanine alcohol derivatives II and III. These N‐7 and N‐9 isomeric alcohols of guanine were separated by fractional crystallization. Subsequent esterification of these alcohols with maleic anhydride gave the desired products. In the other case, N2‐acetylguanine was alkylated with 2‐chloroethyl vinyl ether to yield the N‐7 and N‐9 isomer VI and VII, respectively. These were separated using flash column chromatography.
Synthesis and characterization of a new monomer with pendant hindered amine group
Authors: Lee C. S. , Lau Wayne W. Y. , Lee S. Y. , Goh S. H. 
Published: April 2003

AbstractA new monomer, 1,2,2,6,6‐pentamethyl‐4‐piperidinyl m‐isopropenyl‐α, α‐dimethylbenzyl carbamate, was synthesized by direct addition of 1,2,2,6,6‐pentamethyl‐4‐piperidinol to m‐isopropenyl‐α, α‐dimethylbenzyl isocyanate in the presence of dibutyltin dilaurate catalyst at elevated temperatures. It was characterized by FT‐IR, 1H‐NMR. MS, and elemental analysis. It is a potential hindered amine light stabilizer as it contains the 2,2,6,6‐tetraalkylpiperidine moiety and its vinylic functionality makes it polymerizable.
N‐(2‐hydroxypropyl) methacrylamide copolymers containing pendant saccharide moieties: Synthesis and bioadhesive properties
Authors: Rathi Ramesh C. , Kopečková Pavla , Říhová Blanka , Kopeček Jindŕich 
Published: April 2003

AbstractA new route for the synthesis of bioadhesive water soluble polymeric drug carriers has been developed. Novel monomers, namely, N‐methacryloylglycylglycylgalactosamine (MA‐Gly‐Gly‐GalN) [8], MA‐Gly‐Gly‐FucN [9], MA‐Gly‐Gly‐GlcN [10], and MA‐Gly‐Gly‐ManN [11], and copolymers [12–16] based on N‐(2‐hydroxypropyl) methacrylamide (HPMA) containing different content of pendant saccharide moieties (galactosamine, fucosylamine, glucosamine, or mannosamine), were synthesized. Copolymerization parameters for the copolymerization of HPMA [M1] and MA‐Gly‐Gly‐GalN [M2] have been determined (r1 = 0.82, r2 = 0.38). Bioadhesion studies with everted sacs of guinesa pig small intestine and colon in vitro demonstrated that HPMA copolymers containing side‐chains terminated in fucosylamine bind selectively to the colonic tissue. The extent of binding was dependent on the fucosylamine content of copolymers.
Thermal degradation mechanisms of liquid crystalline aromatic polyesters studied by pyrolysis–gas chromatography/mass spectrometry
Authors: Sueoka K. , Nagata M. , Ohtani H. , Nagai N. , Tsuge S. 
Published: April 2003

AbstractThe thermal degradation mechanisms of liquid crystalline aromatic polyesters (LCPs) prepared from p‐hydroxybenzoic acid (PHB), biphenol (BP), and terephthalic acid (TA) were studied by pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS). The LCP containing deuterated terephthalate units and the LCPs that have different comonomer ratios were examined. On the basis of the pyrolysis products determined, the origin of the main pyrolysis products (benzene, phenol, biphenyl, phenyl benzoate, etc.) from the corresponding comonomer units were estimated and their thermal degradation mechanisms were eventually discussed in detail.
Living cationic polymerization of vinyl ethers by electrophile/lewis acid initiating systems. VII. Living cationic polymerization of isobutyl vinyl ether by trimethylsilyl halide/zinc halide initiating systems in the presence of p‐methoxybenzaldehyde: Effects of halide anions and zinc halides
Authors: Kamigaito Masami , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

AbstractTrimethylsilyl halides (Me3SiY), in conjunction with zinc halides (ZnX2) (Y and X:I, Br, Cl), were employed to investigate the living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene at −15°C in the presence of p‐methoxybenzaldehyde; with the aldehyde and IBVE monomer, Me3SiY yields an initiating species [Me3SiOCHC6H4(OMe) CH2CH(OiBu) Y] that triggers the IBVE polymerization via the activation of its carbon‐halogen bond (CY) by ZnX2 into Cδ+…︁Yδ−…︁ZnX2. Living polymerizations occurred with the silyl iodide and bromide irrespective of the type of ZnX2, either when Y = X (Me3Sil/Znl2 and Me3SiBr/ZnBr2) or when Y ≠ X (Me3Sil/ZnBr2, Me3SiI/ZnCl2, and Me3SiBr/Znl2). With these five initiating systems, the number‐average molecular weights (M̄n) of the polymers increased in proportion to monomer conversion, and the molecular weight distributions (MWDs) of the polymers were narrow (M̄w/M̄n = 1.1−1.2). The Me3SiCl‐based systems (Me3SiCl/ZnCl2 and Me3SiCl/Znl2), in (Me3SiCl/Znl2), in contrast, failed to give perfectly living polymerization; the M̄n indeed increased with conversion, but the MWDs of the polymers were broader (M̄w/M̄n = 1.3−1.5). Thus, the living nature of the polymerizations with Me3SiY/Znx2 is primarily determined by the halogen Y in Me3SiY, which generates the terminal carbon‐halogen bond (CY) that is activated by ZnX2 for the propagation via a species Cδ+…︁Yδ−…︁ZnX2. For Y−, not only the iodide but the bromide anion also is suited for living cationic polymerization. The virtual absence of the effects of X in ZnX2 implies that the halogen exchange between ZnX2 and Y from Me3 SiY at the growing end (Cλ+…︁Yδ−…︁ZnX2 ⇄Cδ+…︁Xδ−…︁ZnXY) is absent or negligible.
Anionic polymerization of 4‐methyl‐2‐oxetanone (β‐butyrolactone)
Authors: Duda Andrzej 
Published: April 2003

AbstractPolymerization of 4‐methyl‐2‐oxetanone (1) initiated with potassium acetate‐dibenzo‐18‐crown‐6 complex (2) in THF as solvent, was studied. Transfer reactions, leading to both crotonate anions and carboxylic acid formation, have been observed. Two kinetic effects of these reactions, hampering the living polymerization, have been established. The first results from reinitiation with the crotonate anions and thereby lowers the polymer molecular weight. The second is the decrease in the overall polymerization rate due to complexation of the growing carboxylate anions with carboxylic acid moieties. Kinetic scheme of polymerization involves propagation accompanied by transfer followed by slow reinitiation. This scheme, including complexation of the active species has been solved numerically. The apparent rate and equilibrium constants (kp, ktr, kri, and Kass and respectively) have been determined. Although these kinetic parameters depend strongly on the polymerization conditions, but the ratio of the rate constants kp : kt : kri is fairly constant and equal to 10−4 : 10−6 : 10−6, respectively (at 20°C). Conditions of the controlled anionic synthesis of the amorphous poly(4‐methyl‐2‐oxetanone) with \documentclass{article}\pagestyle{empty}\begin{document}$\bar M_n$\end{document} as high as 1.7 × 104 and \documentclass{article}\pagestyle{empty}\begin{document}${{ \le \bar M_n } \mathord{\left/ {\vphantom {{ \le \bar M_n } {\bar M_n }}} \right. \kern-\nulldelimiterspace} {\bar M_n }} \le 1.20$\end{document} have also been elaborated.
Polyisobutylene‐containing block polymers by sequential monomer addition. IV. New triblock thermoplastic elastomers comprising high Tg styrenic glassy segments: Synthesis, characterization and physical properties
Authors: Puskas J. E. , Kaszas G. , Kennedy J. P. , Hager W. G. 
Published: April 2003

AbstractNew linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert‐ether (dicumyl methyl ether) initiator in conjunction with TiCl4 coinitiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at −80°C. After the living narrow molecular weight distribution PIB midblock ($\[\bar M_n\]$ = 1.1–1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di‐tert‐butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p‐methylstyrene (pMeSt), p‐t‐butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6‐trimethylstyrene (TMeSt) and α‐methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N‐dimethylacetamide (DMA), TPEs with good mechanical properties (10–20 MPa tensile strength, 300–600% elongation) were prepared. The products exhibit a low and a high temperature Tg characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt–PIB–PSt triblock copolymers due to the higher Tgs (PpMeSt = 108, PptBuSt = 142 and PIn = 220–240°C) of the outer blocks. The Tg of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt‐butylstyrene‐co‐indene) showed a single glassy transition Tg = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end‐blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt–PIB–PSt triblock of similar composition.
Model studies and a new melt polycondensation route to poly‐bisphenol a–iso/terephthalate (polyarylate)
Authors: Oishi Tsutomu , Hall H. K. 
Published: April 2003

AbstractAlternate syntheses of polyarylate from dimethyl iso/terephthalate (DMI/DMT) and bisphenol‐A (BPA) or bisphenol‐A diacetate (BPAOAc) were investigated using a variety of catalysts. The model exchange of DMT with 4‐t‐butylphenol with loss of methanol proceeded moderately rapidly at rather low temperature (170°C) to produce to mono‐ and di‐t‐butylphenyl terephthalates. Dibutyltin oxide is the preferred catalyst. Alkali metal phenoxides are almost as effective but were less soluble. The model reaction of DMT with 4‐tert‐butylphenyl acetate involving loss of methyl acetate gave comparable results using dibutyltin oxide as catalyst. Based on these model results, polycondensations of DMI/DMT with BPAOAc under optimal conditions, gave polyarylate having an inherent viscosity 0.34 dL g−1 in quantitative yield and light brown color. Polycondensation with BPA was unsatisfactory in terms of yield, molecular weight, and color.
Liquid crystalline lonomers. I. Main‐chain liquid crystalline polymer containing pendant sulfonate groups
Authors: Zhang Baoyan , Weiss R. A. 
Published: April 2003

AbstractLiquid crystalline polymers containing sodium sulfonate groups pendant to the polymer backbone were synthesized by an interfacial condensation reaction of brilliant yellow, a sulfonate‐containing monomer, with 4,4′‐dihydroxy‐α,α′‐dimethyl benzalazine and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. Polymers containing up to ca. 4 mol% brilliant yellow were characterized by elemental analysis and ultraviolet spectroscopy. The polymers were thermally stable to about 300°C, and they exhibited a broad nematic mesophase region of 70–100°C. The solution viscosity behavior in chloroform suggested that intramolecular associations of the sulfonate groups occurred at low polymer concentrations and intermolecular associations predominated at higher concentrations.
Stereoselective nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate in cyclohexanone solution: Influence of the reaction temperature on the mechanism
Authors: Spitz Roger , Llauro‐Darricades Marie‐France , Michel Alain , Guyot Alain , Mijangos Carmen , Martinez Gerardo , Millan Jose Luis 
Published: April 2003

AbstractNucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
Structural modifications in imide‐aryl ether phenylquinoxaline random copolymers
Authors: Hedrick * J. L. , Labadie J. W. 
Published: April 2003

AbstractA rigid rod polyimide derived from biphenyldianhydride (BPDA) and p‐phenylenediamine (PDA) was modified by the incorporation of diamines containing performed phenylquinoxaline and aryl ether linkages, and the morphology and mechanical properties of the resulting imide‐aryl ether phenylquinoxaline copolymers were investigated. These phenylquinoxaline containing diamines, 1, 4‐bis[6‐(3‐aminophenoxy)‐3‐phenyl‐2‐quinoxalinyl] benzene and 1, 4‐bis[6‐(4‐aminophenoxy)‐3‐phenyl‐2‐quinoxalinyl] benzene, were prepared by a novel nucleophilic aromatic substitution reaction of 1,4‐(6‐fluoro‐3‐phenyl‐2‐quinoxalinyl) benzene with either 1, 3‐ or 1, 4‐aminophenol in the presence of K2CO3, respectively. The diamines were utilized as co‐monomers with BPDA and PDA to synthesize poly(amicacids.) Films were cast and cured (350°C) to effect imidization, affording films which showed high elongations and moduli. The copolymers with high phenylquinoxaline compositions displayed Tg's in the 300°C range, and the thermal stability of the copolymers was comparable to that of the parent polyimide. The copolymers also showed improved auto‐ or self‐adhesion, particularly those which showed a Tg, allowing sufficient molecular motion for interdiffusion.
Solid‐State 13C‐NMR spectral evidence for charge transfer complex formation in aromatic diimides and dianhydrides
Authors: Dinan Frank J. , Schwartz Willis T. , Wolfe Roger A. , Hojnicki Daniel S. , Clair Terry St. , Pratt J. Richard 
Published: April 2003

AbstractSolution and solid‐state proton decoupled 13C‐NMR spectra were determined on two diimides derived from 4, 4′‐oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′‐isophthaloyldiphthalic anhydride (IDPA) and 4, 4′‐terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid‐state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides.
Linear aliphatic polysulfides: Synthesis and characterization
Authors: Sianawati E. , Van De Mark M. R. 
Published: April 2003

AbstractBinary condensation copolymers of 1,2‐ethane dithiol and 1,3‐propane dibromide, 1,4‐butane dibromide, and 1,6‐hexane dibromide were prepared. Yields ranged from 55 to 89% with molecular weights of 1–2 × 104 Daltons. The polymers were synthesized via an SN2 process with and without the presence of water. The polymers were characterized by DSC, viscosity, FT‐IR, and 1H‐and 13C‐NMR spectra.
Evidence for interphasial amide formation between surface‐bound poly(3‐aminopropyltrisiloxane) and polyamide‐6 in glass bead reinforced polyamide‐6 model composites
Authors: Jenneskens Leonardus W. , Venema Arnold , Van Veenendaal Nico , Huysmans Willem G. B. 
Published: April 2003

AbstractGlass beads pretreated with equal amounts of either natural abundance‐or selectively 13C‐enriched (3‐13C)‐3‐aminopropyltriethoxysilane were used as filler for the preparation of polyamide‐6 model composites. After isolation of the glass beads from the composite by dissolving the polymer matrix in trifluoroethanol, the glass beads were investigated by pyrolysis capillary gas chromatography–mass spectrometry. The identification of the aldimine derivatives 1 and 2, respectively, containing the 13C‐label at C3 next to the imine nitrogen atom provides compelling evidence for amide formation between carboxylic end‐groups of the polyamide‐6 and amine groups of the surface‐bound poly(3‐aminopropyltrisiloxane) in the interphase region during composite preparation.
A solid‐state 13C‐NMR study of crosslinking in polybutadiene by γ radiation: Effect of microstructure and dose
Authors: O'Donnell James H. , Whittaker Andrew K. 
Published: April 2003

AbstractSolid‐state 13C NMR spectroscopy has been used to determine the decrease in CC bonds, formation of crosslinks and cis to trans isomerization during the γ irradiation of (a) > 99% cis, 1,4‐polybutadiene, (b) 54% trans, 41% cis, 1,4‐polybutadiene, and (c) 86% 1,2‐polybutadiene. G(‐cis CC) and G(‐trans CC), were similar and decreased with dose from ≈ 40 for 0‐1 MGy to 5 for 5‐10 MGy. G(‐double bonds) and G(crosslink) were comparable, indicating that crosslinking occurred through the double bonds. G(crosslink) was much higher than values derived from physical properties, confirming that NMR measures the total of inter‐ and intramolecular crosslinking (cyclization). The 1,2 polybutadiene was much more sensitive to crosslinking, and a value of G(‐CC) = 240 was obtained at low doses. Crosslinking evidently proceeds by a kinetic chain reaction in all three types of polybutadiene.
Novel two‐step synthesis of polybenzothiazoles via precursor polyamides from 2,5‐bis(isopropylthio)‐1,4‐phenylenediamine and aromatic dicarboxylic acid chlorides
Authors: Hattori Tatsuya , Akita Hiroshi , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractA novel two‐step method for the synthesis of polybenzothiazoles has been developed starting from 2,5‐bis(isoprophylthio)‐1,4‐phenylenediamine and aromatic dicarboxylic acid chlorides. The low‐temperature solution polycondensation of these monomer pairs in N‐methyl‐2‐pyrrolidone afforded the aromatic polyamides with pendant isopropylthio groups having inherent viscosities in the range of 0.8 and 2.4 dL/g. The soluble precursor polyamides were subjected to thermal cyclization to the corresponding polybenzothiazoles along with the elimination of propylene and water. The resulting polymers were also characterized.