bluuebunny/crossref_metadata_2025 huggingface dataset:
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

New 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

Alternate 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

Liquid 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

Nucleophilic 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

A 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

Solution 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

Binary 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

Glass 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

Solid‐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

A 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.
Synthesis and characterization of poly(4‐vinylpyridine) substituted with a novel betaine salt derived from 4,5‐dicyanoimidazole
Authors: Apen Paul G. , Rasmussen Paul G.
Published: April 2003

A novel betaine internal salt (3) has been synthesized by the reaction of pyridine with 1‐methyl‐2‐bromo‐4,5‐dicyanoimidazole (1). The reaction of pyridine with 1 serves as a model for the reaction of poly(4‐vinylpyridine) with 1. The reaction of poly(4‐vinylpyridine) with 1 gives betaine salt substituted polymers which were characterized by IR, NMR, UV‐visible spectroscopy, and viscometry. The substituted polymers were compared to the model compound (3) and to unsubstituted poly(4‐vinylpyridine) in order to determine polymer structure and the degree of substitution. One of the substituted polymers shows polyelectrolyte behavior. Thermal characterization of the substituted polymers shows two exothermic transitions at 260 and 340°C attributed to chemical reactions of the pendant groups.
Studies of the antenna effect in polymer molecules. XVII. Synthesis and photocatalytic activity of poly(sodium styrenesulfonate‐co‐N‐vinylcarbazole) and poly[sodium styrenesulfonate‐co‐N‐(acryloyloxyhexyl)carbazole]
Authors: Nowakowska M. , White B. , Vogt S. , Guillet J. E.
Published: April 2003

Two new antenna polyelectrolytes, poly(sodium styrenesulfonate‐co‐N‐vinylcarbazole) (PSSS–VCz) and poly[sodium styrenesulfonate‐co‐N‐(acryloyloxyhexyl)carbazole](PSSS–AHCz) have been synthesized. Both polymers were found to solubilize large hydrophobic compounds such as perylene in aqueous solution, but PSSS–AHCz was much more efficient than PSSS–VCz. The distribution coefficients of perylene between the polymer pseudophase and water was determined to be (2.9 ± 0.1) × 106 and (4.0 ± 0.2) × 104 in PSSS–AHCz and PSSS–VCz, respectively. The greater solubilizing ability of PSSS–AHCz is attributed to the higher content of hydrophobic monomer units in the polymer. Both copolymers displayed photocatalytic activity, absorbing light in the UV‐visible spectral region. Energy can then be transferred to a solubilized molecule or dissolved oxygen and induce photochemical reactions. The model reaction used in this study was the photosensitized oxidation of perylene solubilized in aqueous polymer solutions. PSSS–AHCz was found to be a much more efficient photocatalyst than PSSS–VCz. The enhanced photocatalytic activity of PSSS–AHCz is attributed to the greater concentration of carbazole chromophores, the higher local concentration of probe in the polymeric pseudophase and possibly to the elimination of the low‐energy excimer.
Synthesis of linear polyformal and copoly(carbonate formal) from polycarbonate
Authors: Wang Z. Y. , Berard N. , Hay A. S.
Published: April 2003

A linear, high molecular weight polyformal is readily synthesized by direct transformation of commercially available polycarbonate. The reaction is best carried out in dibromomethane with 8.0 equiv. of potassium hydroxide pellets in the presence of a phase‐transfer catalyst at 90–95°C. A random copoly(carbonate formal) can also be obtained simply by reducing the amount of potassium hydroxide used in the reaction. The molecular weight of the resulting polymer is governed by the starting polycarbonate.
Excited states of CF4 plasma for polymerization of TMPTA monomer
Authors: Bretagne J. , Epaillard F. , Richard A.
Published: April 2003

The F and CF2–CF2+ excited states have been detected by emission spectroscopy in CF4RF plasmas used for TMPTA polymerization. These excited states are related through electron collision to F and CF2 ground states. The temporal variation of the F and CF2–CF2+ radiative states near the substrate reveals that the F atoms disappear first by incorporation in the monomer during the polymerization phase and, then, by a third body recombination process enhanced by the polymer surface. The CF2–CF2+ radiative states are varying as the inverse of the F states indicating a strong destruction mechanism of CF2 radicals by F atoms.
Model studies on the kinetics and mechanism of polyarylate synthesis by acidolysis
Authors: Huang Jianing , Leblanc Jean‐Pierre , Hall H. K.
Published: April 2003

Model reactions were carried out to simulate the acidolysis process for polyarylate synthesis by using p‐tert‐butylphenyl acetate (ptBuPhOAc) and benzoic acid in diphenyl ether. p‐tert‐Butylphenol was formed in the reaction mixture and its concentration stayed constant throughout the reaction. Acetic benzoic anhydride and benzoic anhydride were detected by NMR. Based on this experimental evidence, a mechanism for the acidolysis was proposed involving the mixed anhydride. The kinetics of the acidolysis reaction was studied for this model reaction. The overall reaction order is two and the reaction order with respect to each reactant is one. Second‐order reaction rate constants were measured at different reaction conditions (200–250°C). The activation energy (Ea), activation enthalpy (ΔH≠), and activation entropy (ΔS≠) were calculated from these data. The thermodynamic parameters of the acidolysis reaction were also measured for the analogous reaction of p‐tert‐butylphenyl pivalate (ptBuPhOPiv) and benzoic acid. The kinetics of two other elementary reactions involved in the acidolysis reaction were also studied: p‐tert‐butylphenol with acetic anhydride or benzoic anhydride, and p‐tert‐butylphenyl pivalate with benzoic acid.
An improved method for the diimide hydrogenation of butadiene and isoprene containing polymers
Authors: Hahn Stephen F.
Published: April 2003

The hydrogenation of unsaturated polymers with diimide generated in‐situ by thermolysis of p‐toluenesulfonyl hydrazide (TSH) is a commonly used method for preparing laboratory scale quantities of saturated diene based polymers. The by‐products from TSH, particularly p‐toluenesulfinic acid, can attack at olefinic sites, adding p‐tolylsulfone functionality and degrading polymer molecular weight. The addition of tri‐n‐propyl amine has been found to eliminate these side reactions in butadiene containing polymers and copolymers, enabling the preparation of polymers devoid of backbone unsaturation. No detectable sulfur‐containing impurities were indicated by IR, NMR, or elemental analysis, and no chain degradation was observed via GPC analysis of the hydrogenated polymers. cis‐Polybutadiene and butadiene containing random and block copolymers with styrene were hydrogenated cleanly using this technique. A ratio of 2 mol TSH and 2 mol amine/mol of olefin was necessary to assure > 99% hydrogenation, and a w/v ratio of 2 parts butadiene/100 parts o‐xylene gave the most efficient hydrogenation. Polymers prepared from isoprene were only partially hydrogenated when treated with TSH in the presence of tri‐n‐propyl amine, and gave evidence of slight degradation of the polymer structure.
Preparation of hydrogenated nitrile rubber using palladium acetate catalyst: Its characterization and kinetics
Authors: Bhattacharjee Susmita , Bhowmick Anil K. , Avasthi B. N.
Published: April 2003

Hydrogenated nitrile rubber was prepared by using palladium acetate as the homogeneous catalyst system. The effect of different reaction parameters on the level of hydrogenation was studied. The extent of hydrogenation increased with increase in reaction time, temperature, pressure, and catalyst concentration. A maximum conversion of 96% could be achieved. The degree of hydrogenation was estimated from IR and NMR spectroscopy. The selectivity of the catalyst in reducing CC in presence of CN was supported by IR and 13C‐NMR spectra. ESCA studies further confirmed this observation. Properties of hydrogenated nitrile rubber were investigated by various techniques such as gel permeation chromatography (GPC), glass transition temperature (Tg), stress‐strain behavior and rheological measurements. GPC studies showed no significant change in molecular weights of the products after the reaction. Tg value decreased with an increase in the level of hydrogenation. The ultimate stress improved significantly with the increase in the extent of hydrogenation. The die swell decreased with hydrogenation at a particular shear rate. The kinetics of the NBR hydrogenation were investigated. With the increase of the hydrogen pressure and catalyst concentration, the rate of the reaction increased. The reaction was apparently first order with respect to olefinic substrate at higher hydrogen pressure. The apparent activation energy, enthalpy, and entropy of the reaction were calculated as 29.9 kJ/mol, 27.42 kJ/mol, and –0.20 kJ mol−1 K−1, respectively.
Gamma‐, photo‐, and thermally‐initiated oxidation of linear low density polyethylene: A quantitative comparison of oxidation products
Authors: Lacoste J. , Carlsson D. J.
Published: April 2003

The detailed oxidation products from the initiated oxidation of linear low density polyethylene have been compared by the use of infrared spectroscopy combined with chemical derivatization. Oxidized films were treated with NO or SF4 to allow the resolution of the various alcohol and hydroperoxides and of the carbonyl species, respectively. All types of initiation gave very similar products but in varying quantities. In photooxidation, hydroperoxide was clearly shown to approach a photostationary concentration either from below for fresh film or from above for samples that had been pre‐oxidized by γ‐irradiation, prior to UV exposure. Carboxylic acid groups, the main backbone scission product, dominated in photooxidations, possibly as the result of the further oxidation of sec‐hydroperoxide sites.
Poly(Aryl ether‐phenylquinoxaline)s: Self‐polymerization of an A—B monomer via quinoxaline‐activated ether synthesis
Authors: Labadie J. W. , Hedrick J. L. , Boyer S. K.
Published: April 2003

A new A—B monomer, 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline (1), which contains both a quinoxaline‐activated fluoro group and a phenol group was prepared and it's self‐polymerization studied. Compound 1 was prepared either by condensation of 3,4‐diaminofluorobenzene with 4‐hydroxybenzil, or condensation/demethylation with 4‐methoxybenzil in a one pot procedure. The polymerization of 1 was carried out in NMP in the presence of potassium carbonate at 180–190°C, analogous to previous examples of quinoxaline‐activated polyether synthesis. A new poly(aryl ether‐phenylquinoxaline) (2) was synthesized by this procedure, which was processable from N‐methylpyrrolidone, displayed a Tg of 255°C and a polymer decomposition temperature of 450°C. The mechanistic implications of quinoxaline activated fluoro‐displacement using an A—B monomer are discussed.
Absorption spectra of thin film of polyaniline
Authors: Wan Meixiang
Published: April 2003

The absorption spectra of thin film of polyaniline (PANI) on slide glass coated by a spin coater were measured as a function of the protonation state of PANI, the concentration of solution of PANI in NMP, drying temperature, and atmosphere. The absorbance value of the 950 nm peak and the ratio of the absorbance value at 950 nm to that of the 630 nm peak increases with increasing the protonation state of PANI. This is consistent with the observation of varying the conductivity with the protonation state. A modified molecular structure of PANI is proposed:
magnified image
where y and x are defined as the oxidation and the protonation states of PANI, respectively.
Synthesis and conformation of poly(L‐azetidine‐2‐carboxylic acid‐L‐proline) and poly([L‐proline]3‐L‐azetidine‐2‐carboxylic acid)
Authors: Tsai F. H. , Overberger C. G. , Zand R.
Published: April 2003

The synthesis, characterization, and conformational assessment of poLy(L‐Aze‐L‐Pro) and poly[(L‐Pro)3‐L‐Aze] are reported. The polymers were prepared by using the pentachlorophenol active ester as the polymerizable tetrapeptide derivatives. The copolymer, poly(L‐Aze‐L‐Pro), assumes a Form II helix in polar solvents, and is converted into a form I‐like helix at a critical solvent composition of ethanol to trifluoroethanol. The CD spectrum of this Form I‐like conformation of poly(L‐Aze‐L‐Pro) is similar to that of poly(trans‐5‐isopropyl‐L‐proline), indicating that the rigid four‐membered ring at the alternating position can lock in the structure by a mechanism similar to that of a bulky substituent at the trans‐5‐position of proline. The helix conformation of this copolymer was unfolded in a 0.2M CaCl2 aqueous solution. In contrast to poly(L‐Aze‐L‐Pro), the copolymer of poly[(L‐Pro)3‐L‐Aze] contains both cis and trans peptide bond geometry when dissolved in a 90:10 ETOH‐H2O mixture. The conversion of the mixed conformation of poly[(L‐Pro)3‐L‐Aze)] into a polyproline Form II‐like structure occurred in highly polar solvent environments such as water.
Grafting of polymers onto carbon whisker by anionic graft polymerization of vinyl monomers using metallized aromatic rings and/or phenoxy lithium groups on the surface as initiator
Authors: Tsubokawa Norio , Yoshihara Toshio , Sone Yasuo
Published: April 2003

During the anionic polymerization of methyl methacrylate (MMA) initiated by n‐butyl‐lithium (n‐BuLi) in the presence of carbon whisker, PMMA was found to be grafted onto the surface depending on the propagation from OLi groups, which are produced by the reaction of oxygen containing groups on the surface with n‐BuLi. But no grafting of polystyrene was observed at all. By the activation of OLi groups by the addition of crown ether, however, the grafting of polystyrene onto the carbon whisker was achieved. On the other hand, it was found that metallized carbon whisker also initiates the anionic graft polymerization of MMA and styrene: percentage of grafting of PMMA and polystyrene reached 231.3 and 157.9%, respectively. The metalation of carbon whisker was achieved by the treatment with n‐BuLi in aprotic polar solvents, such as N,N,N′,N′‐tetramethylethylene‐diamine or hexamethylphosphorous triamide, and in toluene in the presence of complexing agent of cation such as crown ether or a small amount of aprotic solvent. In the polymerization, grafted polymer chains were considered to propagate both from metallized aromatic rings and from OLi groups. The polymer‐grafted carbon whisker gave a stable colloidal dispersion in organic solvents.
Inhibition of acrylic acid polymerization by phenothiazine and p‐methoxyphenol. II. Catalytic inhibition by phenothiazine
Authors: Levy Leon B.
Published: April 2003

Inhibition of acrylic acid by p‐methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N‐radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p‐methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p‐methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p‐methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p‐methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.
Cationic polymerization of γ‐methyl‐ and α‐methylphenylallene
Authors: Takahashi Tatsuya , Yokozawa Tsutomu , Endo Takeshi
Published: April 2003

The cationic polymerizations of γ‐methylphenylallene (1) and α‐methylphenylallene (2) were carried out with some Lewis acids at 25 and 0°C in dichloromethane to obtain the corresponding polymers through allyl cations, respectively. Tin (IV) chloride was found to be an effective catalyst for the cationic polymerization of both allenes 1 and 2 compared with other Lewis acids. Thus, in the polymerization of 1, methanol‐insoluble polymer was only obtained using Tin (IV) chloride, and M̄n of methanol‐insoluble polymer obtained by Tin (IV) chloride was the highest in the polymerization of 2. From the analysis of 1H‐ and 13C‐NMR spectra of the obtained polymers, the polymer from 1 consisted of two kinds of units polymerized by each double bonds of allene 1, whereas the polymer from 2 consisted of only one unit polymerized by terminal double bond of allene 2. Moreover, effect of solvent on the cationic polymerizations of 1 and 2 were discussed.
Thermal redistribution reactions in crosslinked polysiloxanes
Authors: Belot V. , Corriu R. J. P. , Leclercq D. , Mutin P. H. , Vioux A.
Published: April 2003

The thermolysis under argon of various polysiloxane resins containing D, T, DH, or TH units was investigated using thermogravimetric analysis combined with mass spectroscopy (TG/MS analysis) and solid‐state 29Si‐NMR. Redistribution reactions involving the exchange of SiC/SiO bonds or SiH/SiO bonds were evidenced in addition to the exchange of SiO/SiO bonds reported to date. These reactions significantly modify the initial siloxane units and lead to an escape of volatile silanes or siloxanes. The exchange of SiH/SiO bonds takes place at lower temperatures (300°C) than the exchange of SiC/SiO bonds (500°C).
Catalytic inhibition in free radical polymerizations
Authors: Suddaby K. G. , O'Driscoll K. F. , Rudin A.
Published: April 2003

Free radical polymerizations of methyl methacrylate and methacrylamide in DMF solution were found to be catalytically inhibited by the addition of the boron fluoride derivative of cobaloxime to the system. The nature of this inhibition is examined and equations which describe the kinetics of these catalytically inhibited polymerizations are developed. Using these equations estimates of the inhibition constants (Cz) of 7.23 × 102 and 2.27 × 102 were estimated for methacrylamide and methyl methacrylate, respectively.
Poly(N‐acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. III. Surface properties and abhesion
Authors: Cai Gangfeng , Litt Morton H.
Published: April 2003

The surface properties and abhesion of both N/Si and U/Si series of random copolymers were studied by contact angle and peel strength measurements. When these copolymers are coated on clean glass slides, the contact angles of water on the polymer films are over 105° for copolymers with less than 50 mol % of Si, and 98‐104° for those with more than 50 mol % of Si. All the polymers have similar critical surface energies, 21 dyn/cm (from hydrocarbon probes) and 20 dyn/cm (from EtOH/H2O probes), within the experimental error. This demonstrates that the amide groups in the polymer backbones are buried and all the polymers have methyl surfaces. The copolymers with less than 50 mol % Si (for N/Si copolymers) or 20 mol % (for U/Si copolymers) are stable and show good abhesive properties toward Scotch magic tape at or below 50°C. The peel strengths of Scotch magic tape with the copolymer coated slides rise dramatically as the annealing temperatures approach to the melting points of the polymers.
Stereoregular polyamides derived from methylene‐L‐tartaric acid and aliphatic diamines
Authors: Rodríguez‐Galán A. , Bou J. J. , Muñoz‐Guerra S.
Published: April 2003

Stereoregular polyamides containing two chiral backbone carbons in the repeating unit were prepared by polycondensation of bis(pentachlorophenyl) 2,3‐O‐methylene‐L‐tartrate with 1,9 and 1,12‐alcanediamines activated as N,N′‐bis(trimethylsilyl) derivatives. The polymers were characterized by elemental analysis, IR, and 1H‐NMR spectroscopy, and differential scanning calorimetry. Both viscosimetry and GPC were used to estimate the molecular weights which ranged between 6000 and 44000. These polytartaramides were readily soluble in chloroform, displayed moderate optical activity in solution, and formed highly crystalline films.
Molecular weight distribution in emulsion polymerization. I. The homopolymer case
Authors: Storti Giuseppe , Polotti Gianmarco , Cociani Michele , Morbidelli Massimo
Published: April 2003

A model for evaluating the instantaneous degree of polymerization distribution of homopolymers produced in emulsion, based on the mathematics of the Markov chains, is developed. The model accounts for any number of active chains per particle, as well as for the two fundamental mechanisms of chain termination: mono‐ and bi‐molecular, both by combination and by disproportionation. The core of the model is the so called subprocessmain process treatment, which allows us to correctly evaluate the degree of polymerization of the chains growing in the polymer particles, by distinguishing between the events experienced by the polymer chain which imply a change of its degree of polymerization (subject transitions) and those which imply only a change in the particle state (environment transitions). This is obtained by properly defining the one‐step transition probability matrix of the relevant Markov process. Once this is done, the evaluation of the distribution of the degrees of polymerization reduces to a few simple operations among matrices. Explicit expressions for the instantaneous probability density functions and the relative cumulative distributions are obtained. The application of such relationships is facilitated by the numerical procedures reported in the Appendices. The results of the model developed in this work are in agreement with those of earlier models in the range of parameter values of practical interest. In the limit of very low molecular weights, only the model developed in this work provides the correct answer. Moreover, a much more significant result is its applicability to the case of emulsion copolymerization, as it is shown in Part II.
Selective hydrolysis of oxazoline block copolymers
Authors: Litt M. H. , Lin C. S.
Published: April 2003

Block copolymers, composed of a hydrophobic block [poly(N‐t‐butylbenzoyl ethylenimine) or poly(N‐lauroyl ethylenimine)] and a hydrophilic block [poly(N‐propionyl ethylenimine)], synthesized by cationic ring‐opening polymerization of 2‐substituted Δ2‐oxazolines, were selectively deacylated by acid hydrolysis. The hydrolysis process was monitored by using 1H‐NMR. The results show that the propionyl groups could be removed from the hydrophilic block of the polymer chain without touching the hydrophobic block, if appropriate reaction conditions were used.
Side‐chain liquid crystalline polymers with silphenylene‐siloxane main chains. III. Synthesis and characterization of polymers with phenyl benzoate mesogenic groups
Authors: Itoh Maki , Lenz Robert W.
Published: April 2003

Side‐chain liquid crystalline (SCLC) silphenylene‐siloxane polymers with a phenyl benzoate mesogenic group and polymethylene spacers were prepared and characterized, and their properties were compared with those of equivalent SCLC polymers, SCLCPs, with a biphenyl mesogenic group. With identical spacers and terminal substituents, the melting temperatures of the former were much lower, but the isotropization temperatures were lowered to a lesser extent, than those of the latter, and, consequently, a more thermally stable nematic phase was obtained for the former. Both types of SCLCPs formed nematic phases, while polymethylsiloxanes with the same side‐chain mesogens exhibited smectic phases with wider temperature ranges. The lower thermal stability of the mesophases in the silphenylene‐siloxane SCLCPs compared to those of the SCLC polymethylsiloxanes can be attributed to both the rigidity of the backbone and the greater separation of the side‐chains along the main chains of the former.
Synthesis of poly(phenyltrifluoroethoxyphosphazene) by direct reaction of trimethylsilyl azide with bis(2,2,2‐trifluoroethyl) phenylphosphonite
Authors: Matyjaszewski Krzysztof , Montague Robert , Dauth Jochen , Nuyken Oskar
Published: April 2003

The reaction between bis(2,2,2‐trifluoroethyl) phenylphosphonite and trimethylsilyl azide at temperatures from 70 to 120°C provides a mixture of bis(2,2,2‐trifluoroethoxy)phenylN‐(trimethylsilyl) phosphoranimine and poly(phenyl‐2,2,2‐trifluoroethoxyphosphazene). The polymer is probably formed by phosphine azide intermediates because the phosphor‐animine is thermally stable up to 200°C. The polyphosphazene is an amorphous stereo‐random polymer with a glass transition temperature at −31°C.
Novel dialkylaminoalkyl‐ and dialkylaminoalcoxy‐benzophenones as polymerization photoinitiators. II. Photocalorimetric study on photoinitiated polymerization of butyl and lauryl acrylates
Authors: Mateo J. L. , Bosch P. , Catalina F. , Sastre R.
Published: April 2003

A photocalorimetric study of butyl and lauryl acrylates (BA and LA) polymerization photoinitiated by several benzophenone derivatives is reported. Molecular weight measurements and end‐chain group analysis of the samples are also described and the results are compared with those obtained by dilatometric technique. The role played by the long methylene chain in lauryl acrylate is discussed
Synthesis and calorimetric curing study of amino‐terminated PEEK oligomers
Authors: Corfield G. C. , Wheatley G. W. , Parker D. G.
Published: April 2003

Amino‐terminated polyetheretherketone (PEEK) oligomers were prepared by the condensation of 4,4′‐difluorobenzophenone and hydroquinone in the presence of a calculated excess of m‐aminophenol endblocker. The molecular weight of the oligomer was controlled by the manipulation of the ratio of difluoride to hydroquinone with the appropriate stoichiometric amount of m‐aminophenol ensuring amino termination. The thermally induced self‐crosslinking of these oligomers was studied by differential scanning calorimetry (DSC). Curing was found to be quite slow, taking up to 1 h to reach completion at 668 K. Cured materials were all completely amorphous in contrast to the semi‐crystalline starting material. The limiting Tg reached on curing was found to be proportional to the percentage of reactive terminal groups, as would be expected.
Synthesis of poly(phenylacetylene)s containing trifluoromethyl groups for gas permeable membrane
Authors: Hayakawa Yoshio , Nishida Masakazu , Aoki Toshiki , Muramatsu Hiroshige
Published: April 2003

Poly(phenylacetylene)s containing trifluoromethyl groups on their benzene rings were synthesized, and gas permeation behaviors of their films were examined. Permeability coefficients for O2 and N2, diffusion selectivity (Do2/DN2) and solubility selectivity (SO2/SN2) were estimated. The gas permeability of polymer films were found to be enhanced remarkably with introduction of trifluoromethyl groups into the polymers: poly[2,4,5‐tris(trifluoromethyl)phenylacetylene], Po2 = 7.8 × 10−8 [cm3 (STP) cm cm−2 s−1 cm Hg−1], Po2/PN2 = 2.1. The relationship between the polymer structures and their gas permeability was discussed.
The effect of the steric hindrance on metallic cation conduction in polymer electrolytes
Authors: Liu H. , Yeh T. F. , Lee H. S. , Skotheim T. A. , Okamoto Y.
Published: April 2003

2,6‐Di‐t‐butylphenol and oligo(ethylene oxide) bound covalently to polyisocyanate were synthesized and characterized. The ionic conductivities of their Li, Na, and K phenolates were studied at various temperatures. The conductivities were in the range of 10−7−10−5 S/cm at 30°C. The conductivity of Na and K salts was approximately 102 greater than that of the Li salts. The t‐butyl groups serve to dissociate K and Na ions from the phenoxide. The cations, therefore, are more mobile as a result increasing the conductivity. The temperature dependence of ionic conductivity suggests that the migration of ions is controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel–Tammann–Fulchere plots. The polyisocyanate backbone is a rather stiff structure, however, a flexible oligo(ethylene oxide) side chain forms complexes with metal ion. Since the ion transport is associated with the local movement of polymer segments, the rigidity of the polymer backbone does not have much influence on the ion mobility.
Kinetic study of light‐induced polymerization by real‐time UV and IR spectroscopy
Authors: Decker C.
Published: April 2003

Real time ultraviolet (RTUV) spectroscopy was used to study the photolysis kinetics of a radical‐type morpholino initiator, during the polymerization of a multiacrylate monomer exposed to UV radiation in bulk, in solution, in a polyurethane‐acrylate resin, and in a poly(methyl methacrylate) matrix. The photolysis rate constant k was determined from the exponential loss profile recorded; it was found to vary between 0.1 and 3s−1, depending on the light intensity and on the monomer concentration. The quenching of the photoinitiator excited states by the acrylate monomer was shown to be an important deactivation pathway which substantially reduces the rate of initiation. The observed influence of the film thickness and photoinitiator concentration on the k value were accounted for by the internal filter effect. Conversion versus time curves were recorded by real time infrared (RTIR) spectroscopy for the various systems examined, thus allowing a direct comparison of both the actual polymerization rate and the residual unsaturation content of the cured polymer. Various factors were shown to be responsible for the early stop of the polymerization, such as depletion of the photoinitiator, O2 inhibition, or vitrification of the polymer. The photoinitiated cationic ring‐opening polymerization of a cycloaliphatic diepoxy monomer was also studied in real time by RTUV and RTIR spectroscopy. Despite a very fast photolysis of the triarylsulphonium initiator, the polymerization of the epoxy monomer developed less rapidly than for the acrylic monomer, with shorter kinetic chain lengths. A linear relationship was found to exist between the decay rate constant and the light intensity, for both the radical and the cationic photoinitiators, as expected for a direct photolysis process.
Liquid crystalline ionomers. II. Main chain liquid crystalline polymers with terminal sulfonate groups
Authors: Zhang Baoyan , Weiss R. A.
Published: April 2003

Liquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4′‐dihydroxy‐α,α′‐dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight‐average molecular weights were estimated from inherent viscosity measurements to be between 6000–11,000 and the sodium sulfonate concentrations ranged from 0–18.4 meq/100 g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140°C to form nematic mesophases that were stable over a temperature range of ca. 80°C. They were thermally stable to about 350°C. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements.
Liquid crystalline polyethers based on conformational isomerism. XIX. Synthesis and characterization of flexible polyethers based on 1‐(4‐hydroxyphenyl)‐2‐(2‐r‐4‐hydroxyphenyl) ethane with H, F, CH3, Br, Cl, and CF3 as R groups
Authors: Percec V. , Zuber M.
Published: April 2003

The synthesis of 1‐(4‐hydroxyphenyl)‐2‐(2‐fluoro‐4‐hydroxyphenyl)ethane (FBPE), 1‐(4‐hydroxyphenyl)‐2‐(2‐chloro‐4‐hydroxyphenyl)ethane (CIBPE), 1‐(4‐hydroxyphenyl)‐2‐(2‐bromo‐4‐hydroxyphenyl)ethane (BrBPE), and 1‐(4‐hydroxyphenyl)‐2‐(2‐trifluoromethyl‐4‐hydroxyphenyl)ethane (CF3BPE), of the corresponding polymers based on 1,5‐dibromopentane (RBPE‐5), 1,8‐dibromooctane (RBPE‐8), and of the copolymers based on various ratios of 1,5‐dibromopentane and 1,8‐dibromooctane [RBPE‐5/8(A/B)] is described. The phase transition temperatures and thermodynamic parameters of RBPE‐5 and RBPE‐8 polymers were compared to those of the corresponding polyethers based on 1,2‐bis(4‐hydroxyphenyl)ethane (BPE) and 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane (MBPE) which were reported previously. Both isotropic‐nematic transition temperatures and corresponding thermodynamic parameters (i.e., enthalpy and entropy changes) decrease in the following order of the substituent R: H > F > CH3 > Cl > Br > CF3. This order corresponds to the increase of the breadth of the RBPE molecules, and agrees with the similar trends observed in low molar mass liquid crystals.
Synthesis and properties of polyamides of 3,3′‐dimethylnaphthidine and its model compounds
Authors: Cimecioglu A. L. , Weiss R. A.
Published: April 2003

A number of polyamides and model amides based on 3,3′‐dimethylnaphthidine and various dicarboxylic acids were synthesized in N‐methylpyrrolidone containing lithium chloride either by low temperature solution or by direct polycondensation using triphenyl phosphite and pyridine. The polyamides had inherent viscosities of 0.36−5.42 dL g−1 and were, in general, readily soluble in N‐methylpyrrolidone. Amorphous members exhibited relatively high glass transition temperatures in the range of 340–380 and 200–230°C for aromatic and aliphatic polymers, respectively. All polyamides showed good thermal stability in nitrogen and in air.
Polyacrylamide gels formed with Cr+3 ion and Cr(acetate)3: Thermodynamically and kinetically controlled crosslinking reactions
Authors: Albonico Paola , Burrafato Giovanni , Lockhart Thomas P.
Published: April 2003

The gelation of buffered aqueous Cr+3/polyacrylamide (PAAm) solutions has been studied over the pH range 2‐11. With Cr+3 supplied as Cr(NO3)3 and a 7.5% hydrolyzed PAAm the upper limit for gelation was about pH 7, but Cr(acetate)3/PAAm solutions gelled as high as pH 9. Evidence is presented that the formation of unreactive colloidal Cr(OH)3(H2O)3, rather than polymer crosslinking, is favored thermodynamically for Cr+3/PAAm solutions at pH > 7. The crosslinks formed in Cr(acetate)3/PAAm solutions at pH 7–9 are deduced to be kinetically controlled products. Independent evidence for the kinetic stability of Cr+3/PAAm gels above pH 7 has also been obtained. Other observations relevant to the mechanism of crosslinking of PAAm with Cr(acetate)3 are described.
Radiation induced terpolymerization of tetrafluoroethylene with propylene and n‐butyl vinyl ether in bulk
Authors: Kostov G. K. , Matsuda O. , Tabata Y. , Machi S.
Published: April 2003

Terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and n‐butyl vinyl ether (NBVE) induced by γ‐rays at room temperature at dose rate 5 × 105 rad/h and P/NBVE molar ratio from 49/1 to 10/40 was carried out. An alternating copolymerization between TFE and two α‐olefins was found to take place in this system, so that 50 mole % of TFE containing terpolymer is always formed at various monomer compositions. The terpolymer composition can be explained successfully by the treatment by a complex mechanism. The complex reactivity ratios of rI (TFE–complex) and rII (TFE‐NBVE complex) were calculated to be 0.5 and 0.6, respectively, assuming a complex mechanism. The polymerization rate and molecular weight increase with NBVE concentration in the monomer mixture. Colorless transparent rubber‐like polymers were obtained at each monomer composition. The glass transition temperature sharply decreases with NBVE concentration in the terpolymer but the thermal and chemical resistances of the terpolymer slightly decrease. Considering these results together with the mechanical properties it has been concluded that the 45/48/7 terpolymer of TFE/P/NBVE molar ratio is good as a practical elastomer useful at relatively low temperatures.