bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and properties of silicon containing copolyamides
Authors: Kiyotsukuri Tsuyoshi , Tsutsumi Naoto , Ayama Koichi , Nagata Minoru
Published: April 2003

Copolyamides containing siloxane moieties in main chain were prepared by a melt polycondensation with 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (E), hexamethylenediamine (N6), and adipic acid (6). Glass transition temperature (Tg), cold crystallization temperature (Tcc), and melting temperature (Tm) were measured by differential thermal analysis (DTA). The depression of Tm for copolyamide was fitted by the Flory curve. Melting peak remarkably broadens with increasing E6 component in copolyamide. The change of Tg was fitted by the Gibbs and Dimarzio's equation in which the number of flexible bond is considered. The difference between Tg and Tcc increased with increasing E6 component. These DTA studies suggest that the crystallization of N66 component in copolyamide is hindered by the bulky siloxane moiety, while the micro‐Brownian motion of amorphous segment is promoted by the flexible siloxane bond. Tensile strength and Young's modulus decreased with increasing E6 component. The solubility in various solvents increased with increasing E6 component. Permeability of oxygen and nitrogen increased with an increase of temperature and E6 component. The separation coefficient of oxygen to nitrogen rapidly increased near 50 mol% of E6 concentration and then leveled out above 70 mol%. The contact angle with water and methylene iodide increased with an introduction of the siloxane moiety into polymer chain.
Graft copolymers from poly(2,6‐dimethylphenylene oxide) and pivalolactone
Authors: Bell Vernon L. , Wakelyn N. T.
Published: April 2003

The copolyether‐polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6‐dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle x‐ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation.
Complex radical copolymerization of di‐n‐butylstannyl dimethacrylate with maleic anhydride
Authors: Rzaev Z. M. O. , Mamedova S. G. , Jusifov G. A. , Rustamov F. B.
Published: April 2003

Mechanisms of radical copolymerization of di‐n‐butylstannyl dimethacrylate with maleic anhydride in the presence of 2,2‐asobisisobutyronitrile are discussed. Complexing (Keq) and copolymerization (r1 and r2) constants have been determined. Quantitative contributions of cyclization and complexing to reactivity ratios of the monomers under study and to propagation reactions have been estimated. The copolymerization has been found to proceed predominantly at the complex radical cyclocopolymerization step, leading to cyclized and linear unsaturated units in the macromolecule chain.
Dissociation of 2,2′‐substituted thioindigo whites, and recombination of their radicals in solution and in polymer matrix
Authors: Leest Yvo , Smets Georges
Published: April 2003

The dissociation of 2,2′‐disubstituted thioindigo whites into captodative radicals and the recombination of these radicals have been examined in solution and in polymeric matrix. For the methyl‐ and ethyl‐substituted TIW the quantum yield of dissociation in solution is equal to 4 × 10−4 and 5 × 10−4, respectively. Using the iodine scavenging method the quantum yield of formation of free radicals was almost 3 to 4 × 10−4, i.e. 20–25% radicals recombine in cage. For the isopropyl and aryl TIWs partial dissociation occurs already at room temperature. Their dissociation enthalpies have been evaluated in solution on the basis of the ESR signal surfaces at different temperatures. For the aromatic substituted Δ Hdiss amounts to 88–95 kJ mol−1, while for i‐PrTIW ΔHdiss is 150 kJ mol−1. The behavior of these compounds was studied in three different matrices: polymethyl methacrylate (PMMA), polypropyl methacrylate (PPMA), and polystyrene (PST). In the cases of the aryl substituted derivatives, cage dimensions of the TIW‐radical pairs were measured at low temperature, and their apparent dissociation enthalpies above their glass transition temperatures were evaluated using ESR spectrometry; they are equal to 118 ± 3 kJ mol−1 in PPMA and around 155 kJ in PMMA and PST. The decay kinetics of the radicals after photolysis of the TIWs below Tg were interpreted on the basis of Waite's equations for diffused controlled reactions. The great influence of steric effects in the cases of the 2‐orthochlorophenyl and the 2,4‐dichlorophenyl TIWs is stressed as well as the importance of the merostabilization of the captodative radicals on these kinetic characteristics. The nature of the polymeric matrix is also underlined; below Tg the diffusion rate constant is only one‐third in PST compared to PMMA. The radicals generated from Ph TIW and its para‐nitro and p‐methoxy derivatives show a strong inhibiting effect toward the polymerization of methyl methacrylate, while the alkyl TIWs behave as free radical initiators.
Interchain electron donor–acceptor complexes. Determination of equilibrium constant and thermodynamic parameters in the solid state
Authors: Percec Virgil , Schild Howard G. , Rodriguez‐Parada José M. , Pugh Coleen
Published: April 2003

The interpolymeric electron donor–acceptor (EDA) complex of donor poly[(N‐ethylcarbazol‐3‐yl)methyl methacrylate] (PHMCM‐2) with acceptor poly‐(2‐[(3,5‐dinitrobenzoyl)oxy]ethyl methacrylate) (PDNBM‐2) presents a single glass transition temperature and a decomplexation endotherm on differential scanning calorimetric (DSC) thermograms. This system is considered a “polymer blend model” which exhibits a lower critical solution temperature (LCST). Phase separation of this blend is kinetically controlled and positive deviations of the glass transition temperatures from weight average values suggest that it behaves as a thermally reversible crosslinked network. Calorimetric methods to determine the heats of mixing of small molecule complexes in solution were adapted for this solid state blend to estimate the equilibrium constant (Keq) and other thermodynamic parameters. Applying a computer iterative procedure and assuming 1 : 1 stoichiometry, a least‐squares fit was found for several different donor molecular weights with three different high molecular weight acceptors. At moderate molecular weights,Keqrises to represent saturation fractions near unity as found in biological systems.Keqdecreases for higher molecular weights, possibly due to trapped chain entanglements. These results are supported by a composition‐independent, “horizontal line” phase diagram, thus resembling the completely complexed/denaturation process in DNA.
Kinetic data on the curing of an epoxy polymer in the presence of lignin
Authors: Feldman D. , Banu Dorina
Published: April 2003

In the present study, dynamic differential scanning calorimetry has been used to investigate the effect of an alkali lignin in amounts up to 20% by weight, on the crosslinking kinetics of an epoxy prepolymer cured with an aliphatic polyamine. Lignin presence does not significantly affect the overall reaction order, but the activation energy increases and the slowing of the overall curing process with lignin content could be explained by the interaction between lignin and the polyamine hardener. The possibility of having a “false compensation” in the case of the use of single DSC scans is also discussed.
Grafting onto chitosan. I. Graft copolymerization of methyl methacrylate onto chitosan with Fenton's reagent (Fe2+−H2O2) as a redox initiator
Authors: Lagos A. , Reyes J.
Published: April 2003

Poly(methyl methacrylate) has been grafted onto chitosan by using Fenton's reagent as a redox initiator in an aqueous medium. Initiation by Fenton's reagent was carried out in the presence of atmospheric oxygen. The percentages of grafting, efficiency, and homopolymer were found to depend on chitosan (RchitOH), ferrous ammonium sulfate (FAS), hydrogen peroxide, monomer (MMA) concentrations, reaction temperature, and reaction time.
Direct polyesterification with thionyl chloride in pyridine improved by a modification of monomer sequences in copolymers
Authors: Higashi Fukuji , Sugimori Shigeru , Mashimo Toshio
Published: April 2003

The direct polyesterification with thionyl chloride (SOCl2) in pyridine was further investigated. Copolycondensations of dicarboxylic acids, bisphenols, and hydroxybenzoic acids were significantly affected by the reaction temperatures and combinations of monomers which could change relative rates of alcoholyses of the activated dicarboxylic acids and the hydroxyacids consequently to vary monomer sequences in the copolymers resulted. The sequences were tried to be varied more directly by stepwise reactions of monomers in copolycondensations of dicarboxylic acids, bisphenols, and p‐hydroxybenzoic acid (PHB), as well as PHB and m‐hydroxybenzoic acid (MHB). The reactions proceeded smoothly and satisfactorily when carried out by initial reaction of dicarboxylic acids and PHB followed by bisphenols likely to favor sequential to random distributions of monomers. Reverse addition of PHB and bisphenols, and then dicarboxylic acids resulted in rapid precipitation due to some oligomerization of PHB at an earlier stage of reaction, and largely retarded the reaction. This was also the case for the copolycondensation of PHB and MHB. Copolymers of high inherent viscosities with up to 65 mol% PHB could be obtained by initial reaction of MHB followed by PHB.
Anionic polymerization of N‐substituted maleimide. II. Polymerization of N‐ethylmaleimide
Authors: Hagiwara Tokio , Someno Tsutomu , Hamana Hiroshi , Narita Tadashi
Published: April 2003

Anionic polymerization of N‐ethylmaleimide (N‐EMI) was carried out with potassium t‐butoxide, lithium t‐butoxide, n‐butyllithium, and ethylmagnesium bromide as initiators in THF and in toluene. An almost quantitative yield of poly(N‐EMI) was obtained with potassium t‐butoxide as initiator in THF in a wide range of polymerization temperatures. Initiators possessing lithium as counter cation produced poly(N‐EMI) in slightly lower yields and ethylmagnesium bromide gave the polymer only in less than 35% yield in THF. As a polymerization reaction solvent, THF was preferable for the polymerization of N‐EMI compared with toluene with respect to polymer yields. Poly(N‐EMI) obtained with anionic initiators exerted unimodal molecular weight distribution. From 1H‐ and 13C‐NMR spectra of poly(N‐EMI) anionic polymerization of N‐EMI with potassium t‐butoxide was revealed to proceed at carbon–carbon double bond. t‐Butoxide system was found to have a “living” polymerization character, i.e., the observed average degree of polymerization was in good agreement with the one calculated from the initial molar ratio of N‐EMI/initiator and the yield of polymer.
Comparative reactivity of water soluble photoinitiators as viewed in terms of excited states processes
Authors: Lougnot D. J. , Fouassier J. P.
Published: April 2003

The activity of 10 water soluble photoinitiators derived from thioxanthone, benzophenone, and benzil were studied comparatively. The mechanisms of initiation were determined by time resolved laser spectroscopy and steady state polymerization. The characteristic features of each series of compounds are pointed out. The possible contribution of biphotonic processes to the initiation step is considered.
Electroinitiated polymerization of acrylamide in acetonitrile medium
Authors: Samal Seetanshu Kumar , Nayak Bimbadhar
Published: April 2003

The electroinitiated polymerization of acrylamide (AA) has been studied in acetonitrile medium using tetrabutylammonium perchlorate (TBAP) as the electrolyte. Split‐cell experiments showed that the polymer formation takes place both in the anode and the cathode compartments. The polymer yield depends on several factors such as the magnitude of the current flow, the duration of the electrolysis, the monomer concentration, the electrolyte concentration, the temperature of the solution, presence or absence of air, and finally whether or not the cell content was stirred. The current exponent of the polymerization was 0.28 with a reaction rate constant of 1.06 reaction % per hour. The IR and NMR spectra of the polymers suggest that the anodic polymer is polyacrylamide and the cathodic polymer is poly‐β‐alanine (CH2CH2CONH). Based on the experimental results, a radical mechanism for the anodic polymerization and an anionic mechanism for the cathodic polymerization have been proposed.
Synthesis and characterization of polyamides containing heterocyclic thiaxanthone units
Authors: Reddy T. Ashok , Srinivasan M.
Published: April 2003

Novel polyamides containing heterocyclic thiaxanthone units were prepared by condensing 2,7‐dichloroformylthiaxanthone‐5,5′‐dioxide and 2,8‐dichloroformylthiaxanthone‐5,5′‐dioxide with various aromatic diamines, under low temperature solution polymerization conditions in DMAc. The model diamide, 2,8‐ditolylcarbamylthiaxanthone‐5,5′‐dioxide was synthesised and characterized by spectroscopic methods. The polyamides were prepared in 70–80% yield and had inherent viscosity in the 0.36–0.73 dL/g range. The poyamides have decomposition temperatures in the 425–510°C range in nitrogen. The effect of thiaxanthone rings on polymer backbone on solubility, crystallinity, and thermal stability is also discussed.
Block copolymers derived from azobiscyanopentanoic acid. X. Synthesis of silicone–vinyl block copolymers via polysiloxane(azobiscyanopentanamide)s
Authors: Inoue Hiroshi , Ueda Akira , Nagai Susumu
Published: April 2003

The synthesis of silicone–vinyl block copolymers has been studied by the use of poly(azo‐containing siloxaneamide)s (abbreviated as PASAs), i.e., polysiloxane (azobiscyanopentanamide)s as macroazoinitiators. PASAs with number‐average molecular weight of 12000–31000 and with siloxane chain lengths of 250–9800 were prepared by the condensation of azobiscyanopentanoyl chloride and α,ω‐bis(3‐aminopropyldimethyl)polysiloxanes in equimolar feeds. Several kinds of silicone–vinyl block copolymers were synthesized by radical polymerization of vinyl monomers such as methyl methacrylate, styrene, and vinyl acetate, in the presence of PASA in homogeneous media. The block copolymers with siloxane contents up to 30 mol % were then characterized on the basis of infrared absorption, proton NMR spectra, and gel permeation chromatography.
Aqueous polymerization of acrylamide initiated by oxygenated cobalt(III) triethylenetetramine complex
Authors: Chen Chuh‐Yung , Kuo Jen‐Feng
Published: April 2003

Polymerization of acrylamide was thermally initiated by the oxygenated cobalt(III) triethylenetetramine complex. Rate, conversion, and molecular weights obtained are favorable comparable to those initiated by K2S2O4 and K2S2O8 initiators. An induction period is about 3 mins. The value of Kdf at 60°C is 6.75 × 10−5 s−1, and the chain transfer to monomer constant is 1.2 × 10−5. The rate dependence obtained are a half order on the initiator concentration and a 1.38 order on the monomer concentration. The mole fraction of combination termination occurred in the overall termination reactions evaluated is 0.746.
Sulphur‐containing polyarylenequinodiimides
Authors: Sergeev V. A. , Nedel'kin V. I. , Arnautov S. A.
Published: April 2003

Different synthetic approaches have been used for preparing some new polymers relating to sulphur‐containing polyarylenequinodiimides. The latter have been obtained both from quinodi‐imidedichloride and aromatic dithioles and directly from 1,4‐phenylenediamine and disulphenylchlorides. The mechanism of this process has been proposed on the basis of studying a model reaction of phenylsulphenylchloride with 1,4‐phenylenediamine. Polyarylenesulphonequinodi‐imides have been obtained by selective oxidation of polyarylenesulphoneamides with phenyliodozoacetate. Their structure has been proved by IR, PMR, and 13C‐NMR spectroscopies. Electrophysical properties of synthesized polymers have been studied.
Mass transfer of oxygen in poly(2‐hydroxyethyl methacrylate)
Authors: Parker J. W. , Cox M. E.
Published: April 2003

The diffusion coefficient of oxygen in poly(2‐hydroxyethyl methacrylate) has been explicitly measured using an optical technique based on fluorescence quenching. This measurement represents the first explicit determination of D in PHEMA. A diffusion coefficient of oxygen in PHEMA of 1.36 × 10−7 cm2/s at 20°C was obtained from this measurement. This value is shown to agree well with permeability data for PHEMA, the free volume theory of diffusion, and with values of D that have been explicitly measured in other methacrylate hydrogels.
Peroxide‐catalyzed grafting of maleic anhydride onto molten polyethylene in the presence of polar organic compounds
Authors: Gaylord Norman G. , Mehta Rajendra
Published: April 2003

The crosslinking of LDPE resulting from reaction with dicumyl peroxide at 180°C is increased in the presence of maleic anhydride (MAH). The presence of electron‐donating nitrogen‐containing compounds (amides, lactams, disubstituted aromatic amines, and amine oxides), phosphorous‐containing compounds (phosphites, phosphates, phosphonates, phosphoramides, and phosphine oxides) and sulfur‐containing compounds (sulfoxides, aryl disulfides, and thiazyl disulfides) which inhibit the homopolymerization of MAH but not that of methyl methacrylate, prevents crosslinking and yields soluble PE containing MAH units. Crosslinking, due to coupling of PE˙ macroradicals formed by hydrogen abstraction from PE by excited MAH, is prevented by electron donation from the additive to the MAH+ cation which is present in the MAH+−MAH excimer as well as in the excimer which is appended to the PE.
Molecular orbital analysis of the XPS spectrum of a fluorine containing polyimide: PMDA–BDAF
Authors: Silverman B. D. , Sanda P. N. , Clabes J. G. , Ho P. S. , Hofer D. C. , Rossi A. R.
Published: April 2003

The results of XPS measurements and molecular orbital calculations performed on the fluorine containing polyimide, PMDA–BDAF, are presented. The calculated carbon 1s (C1s) core energy level positions are compared with the level positions inferred from the XPS measurements. Within Koopman's approximation, the observed shape of the main XPS peak is consistent with the calculated distribution of C1s levels under this peak. Comparison of the magnitude of the carbonyl XPS peak intensity with the main peak intensity indicates a carbonyl C1s signal deficiency compared with that expected for “ideal bulk stoichiometry” i.e., for a polymer with no crosslinks or chain terminations. Comparison of data obtained from a grazing emission (surface sensitive) geometry with that obtained from a normal emission geometry, which probes more deeply into the bulk, indicates a signal enhancement of the C1s levels associated with carbon atoms of the CF3 groups as one nears the polymer surface. Such enhancement might be due to either actual differences in chemical composition, or to preferential structural ordering near the polymer surface.
Kinetics and mechanism of emulsifier‐free emulsion polymerization. II. Styrene/water soluble comonomer (sodium methallyl sulfonate) system
Authors: Chang Herng‐Show , Chen Show‐An
Published: April 2003

The emulsifier‐free emulsion polymerizations of styrene in the presence of about 1 wt% (related to styrene) of the water soluble comonomer, sodium methallyl sulfonate (NaMS), which has short hydrophobic group and strong hydrophilic ionic group, and of the initiator, potassium persulfate, are carried out. Under constant ionic strength, the number density of polymer particles (Np) is found to depend on 0.5‐power of the initiator concentration and shows a minimum in the comonomer concentration plot. Under constant concentration of monomer, comonomer and initiator, Np is found to depend on −1.1‐power of the ionic strength. In the earlier period, the presence of styrene oligomer having MW about 1000 and water soluble poly(NaMS) or copolymer with high NaMS content suggests a micellar nucleation mechanism, by which the styrene oligomer behaves as emulsifier and the poly(NaMS) can either stabilize or destabilize the existing particles, depending on its concentration in the aqueous phase. The particle size is rather uniform having an uniformity very close to 1 (ca. 1.001) throughout the entire process. It is much larger than that of the conventional emulsion polymerization or emulsifier‐free emulsion polymerization with the other comonomers by about 3 to 4 times in diameter or 27 to 64 times in volume, leading to that the average radical number in the particle could be much greater than 0.5. The (conversion)2/3 versus time plot is found to be linear from 6 to 50% conversion. During this period, for the conversion from 10 to 40% the polymerization rate increases twice but the particle volume increases four‐fold. In addition, MWD shows bimodal (excluding the styrene oligomer peak in the earlier period) during the growth period. But the lower MW peak shifts to higher MW and become larger, while the higher MW peak decreases, and finally the MWD becomes single mode after 58.6% conversion. These results suggest a “gradient polymerization” or “transition stage to core‐shell structure” in the earlier stage of particle growth and a “shell part polymerization” in the later stage.
The effect of flexibility on the photodegradation of aromatic diisocyanate‐based polyurethanes
Authors: Hoyle Charles E. , Chawla C. P. , Kim Kyu‐Jun
Published: April 2003

The photolytic degradation of 2,4‐TDI/aliphatic diol polyurethanes is directly dependent on the flexibility of the polymer backbone. The extent of photodegradation is accelerated above the glass transition temperature, indicating the role of chain flexibility and/or oxygen diffusion in the decomposition process. Photolysis of the model compound ethylN‐phenylcarbamate (EPC) in neutral host polymer matrices indicates that theparaphoto‐Fries toorthophoto‐Fries product ratio experiences an accelerated increase with temperature above the glass transition of the polymer matrix.
Polystyrenes with p‐oligo‐siloxane, silane, germanosiloxane, germane, or stannane as p‐substituents as materials for oxygen permeable membranes
Authors: Kawakami Yuhsuke , Hisada Hirofumi , Yamashita Yuya
Published: April 2003

The title polymers were synthesized and the oxygen permeation behavior through the polymer films were studied. The oligodimethylsilane‐substituted polystyrenes showed a little low Po2 compared with the oligodimethylsiloxane‐substituted polystyrenes. The important role of trimethylsiloxyl group in permeation was suggested.
Autoxidation kinetics of atactic polypropylene in bulk
Authors: De Andres Jaime , Aguilar Antonio , Domenech Jorge
Published: April 2003

The kinetics of the reaction between atactic polypropylene (APP) and oxygen in bulk at temperatures ranging from 170 to 210°C and oxygen partial pressures from 160 to 760 torr have been studied by thermal differential analysis. The reaction takes place in two successive steps, both giving hydroperoxide groups as product. Partial reaction orders with respect to APP and oxygen for the first step, which corresponds to the uncatalyzed attack of a CH tertiary bond to give a hydroperoxide, are one and two, respectively. In the second step, interpreted as another attack on a tertiary CH by oxygen, catalyzed by a neighboring hydroperoxide group, reaction orders are one and one‐half for APP and oxygen, respectively. Activation parameters have been determined and a reaction sequence is proposed. Hydroperoxidated APP subsequently decomposes via a zero‐order process giving methylketone groups as its main product. An interpretation of this process is also given.
Kinetics of reactions of methyl α‐eleostearate with cresols
Authors: Yoshimura Yukio
Published: April 2003

The kinetics of addition reactions between methyl α‐eleostearate which forms the main chain of tung oil and cresols when catalyzed by an acid, p‐toluene sulfonic acid, have been studied. The addition reactions, carried out with any one of the o‐, m‐, and p‐cresols were shown to be first order with regard to both methyl α‐eleostearate and cresol concentrations. The reactions were additions of two cresol molecules to one methyl α‐eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step in rate‐determining.

(E: methyl/α‐eleostearate, C: cresols)

The apparent reaction rate constants (L/mol min) were found to be 0.046 for o‐cresol, 0.038 for m‐cresol, and 0.033 for p‐cresol. The apparent activation energies (kcal/mol) were found to be 0.95, 3.66, and 4.05, in the cases of o‐, m‐, and p‐cresols, respectively.
Cure of epoxy resins with cyanoacetamides
Authors: Renner Alfred , Moser Roland , Bellus Miriam , Fuhrer Hermann , Hosang Othmar , Szekely Gustav
Published: April 2003

Cyanoacetamides are a novel class of curing agents for epoxy resins. Since reaction products of epoxy compounds with cyanoacetamides have not yet been described, we investigated the reaction of phenyl‐glycidylether (PGE) and N‐isobutylcyanoacetamide (NICA) under the conditions of the epoxy cure (120–150°C). Twenty‐two fractions of the reaction product have been separated by preparative TLC and characterized by FD and MS mass spectroscopy. The structures of 10 reaction product have been elucidated by MS, NMR, and IR techniques. They belong to the classes of cyclic urethanes, spiro‐dilactones, cyclo‐oxa‐1‐hepten‐4‐one‐2, pyrimidones, aminocrotononitrile, and tertiary amine. This complex model reaction mixture does not enable us to propose a curing mechanism. However practical cure of Bisphenol A diglycidylether (BADGE) yields clear and tough solids with a glass transition temperature up to 200°C, good mechanical strength, and high adhesion to metal surface. Cyanoacetamides are latent hardeners requiring a curing initiator. Since N‐4‐chlorophenyl‐N′‐dimethylurea is a latent initiator, liquid, homogeneous, storage stable “one shot” systems can be formulated which harden quickly above 120°C. Heat aging properties of cured specimens are reported. A series of novel liquid, resinous, and crystalline cyanoacetamides and their potential as curing agent are described.
Morphology of block copolyurethanes. III. Effect of polyether molecular weight on the mechanical properties of solvent cast films
Authors: Benson R. S. , Lyman D. J.
Published: April 2003

A homologous series of copolyether–urethane–ureas were synthesized with polypropylene glycol segments having molecular weights of approximately 200, 400, 700, 1000, 2000, and 3000. These copolymers were characterized using tensile measurements and dynamic mechanical spectroscopy. The dynamic mechanical measurements at low frequencies (≤ 1 Hz) showed evidence of the existence of an α‐relaxation process. This was attributed to constrained polyether segments located at the interfacial region between the hard urea segments and the soft polypropylene glycol segments.
Bis‐ or tetra‐maleimides of substituted s‐triazines chain‐extended by imide, amide, and urea groups for fire‐ and heat‐resistant applications
Authors: Mikroyannidis John A. , Melissaris Anastasios P.
Published: April 2003

Novel phosphorylated bismaleimides and nonphosphorylated tetramaleimides containing substituted s‐triazine rings (chain‐extended by imide, amide, or urea groups) were prepared and polymerized. These polymer precursors were prepared by reacting 2,4‐bis(4‐aminophenoxy)‐6‐diethoxyphosphinyl‐s‐triazine or 2,4,6‐tris(4‐aminophenoxy)‐s‐triazine with maleic anhydride in combination with a bridging agent such as pyromellitic or benzophenone tetracarboxylic dianhydride, terephthaloyl chloride, and tolylene diisocyanate. The structure of polymer precursors was confirmed by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy and their curing behavior was investigated by differential thermal analysis (DTA). The phosphorylated bismaleimides were thermally polymerized at a lower temperature than did the corresponding nonphosphorylated tetramaleimides. Dynamic thermogravimetric analysis (TGA) showed that the nonphosphorylated and phosphorylated cured resins were stable up to 320–370 and 312–327°C, respectively, in nitrogen or air atmosphere. In addition, the latter afforded a relatively higher char yield. The relative thermal and thermooxidative stability of polymers with regard to the chemical structure of the bridging group was of the order imide > amide > urea. Upon isothermal aging the phosphorylated polymers exhibited a lower weight loss than did the corresponding nonphosphorylated polymers.
Investigation of the intramolecular structure of styrene–ethylmethacrylate copolymers by 1H‐ and 13C‐NMR: Reassignment of 1H‐NMR spectra
Authors: Tacx J. C. J. F. , Van Der Velden G. P. M. , German A. L.
Published: April 2003

The compositions and sequence distributions of homogeneous styrene (S)–ethyl methacrylate (E) copolymers, obtained by low conversion solution polymerization have been studied by 1H‐ and 13C‐NMR. A new set of peak triad assignments was proposed for the δ 2.1–4.2 ppm region in the 1H‐NMR spectrum, whereby the reactivity ratios of rS = 0.59 and rE = 0.50 were used to establish this new assignment. The EEE and SSS blocks, present in these copolymers, have a high degree of syndiotacticity (σEE = 0.23, σSS = 0.39), whereas the ESE units are exhibiting a slight tendency toward isotacticity (σES = 0.66).
Studies on some radical transfer reactions by entrapping the radicals as polymer endgroups. III. Reaction of ȮH radical with halide ions
Authors: Pramanick Dinabandhu , Sarkar Jyotish , Bhattacharyya Ramanath
Published: April 2003

The reactions of OH radical with Cl−, Br−, I−, and F− ions have been studied by entrapping the product radicals as polymer endgroup which have been detected and estimated by the sensitive dye partition technique. The rate constants of the reactions with Br−, Cl−, and F− ions have been determined to be 1.51 × 109, 1.32 × 109, and 0.92 × 109 L mol−1 s−1, respectively at 25°C and pH 1.00. Oxidation of I− ions liberates I, which inhibits the polymerization and the reaction could not be followed by polymer endgroup analysis. The observed order of reactivity Br− > Cl− > F− is in accordance with the electron affinities of the halide ions. The acidity of the reaction medium has a strong influence on the rate of reaction. With Br− ions, the rate constant of the reaction falls from 1.51 × 109 to 0.75 × 109 L mol−1 s−1 at 25°C as the pH is raised from 1.0 to 2.8. The method is simple and accurate and can be applied to study very reactive radicals.
Synthesis and properties of polysulfonamides containing thiophene links
Authors: Yi Mi Hie , Lee Sung Goo , Choi Kil‐Yeong , Jung Jin Chul
Published: April 2003

In order to study the synthesis and properties of polysulfonamides containing thiophene links, 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)propane [BCTP], 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)butane [BCTB], 1,1‐bis(5‐chlorosulfonyl‐2‐thienyl)cyclohexane [BCTC], and 2,4‐dichlorosulfonyl thiophene [DCST] were prepared and interfacial polycondensations with various aliphatic diamines were carried out. The resulting polymers had inherent viscosities in the range of 0.13–0.41 dL/g and showed high extent of moisture absorptions. Most of the polysulfonamides were soluble in electron‐donating solvents such as pyridine, DMF, DMSO, NMP, etc. These polysulfonamides exhibited relatively good thermal stabilities. The TGA data revealed 5% weight losses at 275–405°C and residual weights at 500°C were 13–40% under nitrogen. It was also found that dithienyldisulfonyl chlorides produced more thermally stable polymers than DCST, which were comparable to common polysulfonamides from aromatic disulfonyl chlorides.
Photoexcitable polymer membranes. Photoinduced membrane potential across poly(vinyl chloride) membrane doped with a photosensitive crown ether having lipophilic side chain
Authors: Anzai Jun‐Ichi , Hasebe Yasushi , Ueno Akihiko , Osa Tetsuo
Published: April 2003

Photoirradiation induced potential changes of 10–20 mV across the poly(vinyl chloride) membranes doped with a photosensitive lipophilic crown ether, p‐[3,4‐(1,4,7,10,13‐pentaoxatridecane‐1,13‐diyl)phenylazo]hexadecyloxybenzene was studied. The photoresponse of the membrane was highly improved, presumably due to the lipophilic nature of the crown ether. The photoresponse was explained in terms of the charge density change on the membrane surface. The electric double layer theory was applied to estimate the values of the photoinduced change of the charge density.
Graft copolymers having hydrophobic backbone and hydrophilic branches. III. Synthesis of graft copolymers having oligovinylpyrrolidone as hydrophilic branch
Authors: Miyauchi Noriyuki , Kirikihira Isamu , Li Xin , Akashi Mitsuru
Published: April 2003

Graft copolymers were synthesized by the esterification reaction between acrylic copolymers and carboxyl group terminated vinylpyrrolidone oligomer using phase transfer catalysts. Acrylic copolymers were obtained by the radical copolymerization of β‐bromoethyl methacrylate, chloromethylstyrene or glycidyl methacrylate with methyl methacrylate. Hydrophilic oligomers were prepared by the radical oligomerization of vinylpyrrolidone using β‐mercaptopropionic acid as chain transfer agent. The degree of esterification increased with decreasing the molecular weight of oligomer and with increasing the number of potential grafting sites on polymer backbones. The water dispersibility of graft copolymers increased with increasing the nitrogen content and was therefore dependent on the branch oligomer content.
Synthesis of polybutadiene–polysulphide
Authors: Pujol J. M. , Brossas J. , Catala J. M.
Published: April 2003

The anionic synthesis of polybutadiene–polysulphide polymers from butadiene, elemental sulphur, and sodium was studied in a polar solvent (THF). The polycondensation results from the combination of three reactions: initiation of the monomer by the alkali metals, anionic propagation, and deactivation of the dianionic species on elemental sulphur. From the characterization of the resulting polymers it has been shown that the sulphur rank of the polymer can be adjusted by varying the ratio K = [sodium]/[sulphur]. The degree of polymerization of the organic chain can be controlled by changing the temperature or the monomer concentration. From the thiol content, it has been concluded that the polysulphide polymers are principally in a cyclic form. It was also observed that the formation of the 1,4‐structure for the butadiene unit is quantitative when the deactivation of the corresponding carbanions occurs on elemental sulphur.
Synthesis and polymerization of racemic and optically active substituted ß‐propiolactones. V. α‐methyl ß‐propiolactone
Authors: Hmamouchi Mohammed , Prud'homme Robert E.
Published: April 2003

R(+) and S(−) enantiomers of α‐methyl β‐propiolactone (MPL) have been synthesized from the corresponding α‐methyl β‐hydroxymethylpropionates and racemic MPL from methyl methacrylate. The optical purity and absolute configuration of these lactones were determined using 1H‐NMR spectroscopy after complexation with a chiral compound: 2,2,2‐trifluoro‐1‐(9‐anthryl)‐ethanol. Optical purities of 100% were obtained for both the S(−) ([α0] = −10.4°, c = 1.3 g/dL in CHCl3) and the R(+) ([α0] = +10.5°, c = 1.0 g/dL in CHCl3) enantiomers. The corresponding racemic and optically active polylactones [poly(MPL)] were prepared by anionic polymerization, in bulk and in solution, as well as poly(MPL)s of intermediate optical purities. The polymers thus obtained are optically active ([α0] = 16.2° in CHCl3 for the optically pure polymer, S configuration) and exhibit significant differences. For example, the racemic poly(MPL) is soluble in several organic solvents such as tetrahydrofuran, benzene, CCl4, CH2Cl2, hexafluoroisopropanol, and CHCl3, whereas the optically active poly(MPL)s are soluble in CHCl3 and hexafluoroisopropanol only. Moreover, racemic poly(MPL) is amorphous whereas optically active poly(MPL)s are semicrystalline for optical purities larger than 51%. Melting temperatures and enthalpies of fusion of the semicrystalline polylactones vary with optical purity whereas glass transition temperatures remain invariant for all polymers, at about −28°C. The poly(MPL) of highest optical purity exhibits a melting temperature of 95°C and an enthalpy of fusion of 61 J/g.
Thermoxidative degradation of polypropylene
Authors: Vasile Cornelia , Odochian Lucia , Agherghinei Ion
Published: April 2003

The thermoxidative behavior of atactic and isotactic polypropylene under dynamical thermoxidative conditions has been studied. It has been established that, with the increase of the heating rate, the development of the oxidative processes are diminished and consequently a modification in the reaction mechanism takes place. One can notice at the same time that the oxidative processes are more intense in the case of the atactic polymer. The 5–15°C/min heating rates determine significant differences between the thermal behavior of the samples, permitting the elaboration of the standard curves useful in fast determination of the atactic content of the industrial products by routine analysis.
Nucleic acid base grafted imino polyurethane
Authors: Lu C. X. , Yang Yang , Xiao Chaodong , Ji Aixue
Published: April 2003

Preparation of two model polymers of polynucleotides with linear polyurethane backbone and 2‐(thymin‐1‐yl)propionyl or 2‐(uracil‐1‐yl)propionyl group as grafted pendant are described. 2‐(Thymin‐1‐yl)propionic acid (TPA) and 2‐(uracil‐1‐yl)propionic acid (UPA) were grafted into partial imino functionalized polyurethane, poly[(β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NH‐75), at the secondary amino group through amide bonds with 1‐hydroxybenzotriazole (HOBT) using the active ester technique. Two novel polymer models of polynucleotides, poly[(N‐(2‐(thymin‐1‐yl)propionyl)‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NT‐75) and poly[(N‐(2‐(uracil‐1‐yl)propionyl)‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)]‐75 (PU‐NU‐75) were obtained. The imino polyurethane PU‐NH‐75 was produced from the partially deprotected N‐Cbz imino polyurethane, poly[N‐(benzyloxycarbonyl‐β,β′‐diethylene)amine methylene bis(4‐phenylcarbamate)] (PU‐NCbz) which was prepared by the polyaddition of 4,4′‐diphenylmethane diisocyanate (MDI) with diol monomer N‐benzyloxycarbonyl‐β,β′‐dihydroxyethylamine (CbzHEA). Selective N‐protection of N‐benzyloxycarbonyloxy‐5‐norbornene‐2,3‐bicarboximide (CbzONB) with β,β′‐dihydroxyethylamine (HEA) gave the N‐Cbz protected diol monomer HEA. The related monomer model compounds were also prepared by the same methods.
A thermally stable polybenzimidazole polybenzoxazole segmented block copolymer
Authors: Gordon Bernard , Kumpf Robert J. , Painter Paul C.
Published: April 2003

m‐phenyl benzoate end‐capped pre‐polybenzoxazole oligomer and a 3,4‐diaminobenzene endcapped pre‐polybenzimidazole were synthesized. These functionalized oligomers were then condensed to give a polybenzoxazole‐polybenzimidazole segmented block copolymer. The functionalized oligomers were characterized by proton NMR, diffuse reflectance FTIR, and thermal gravimetric analysis. The final block copolymer was characterized by diffuse reflectance FTIR and thermal gravimetric analysis.
Cyclo dehydration reaction of polyhydrazides. I. Kinetic parameters obtained with nonisothermal thermogravimetry
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

The thermal conversion reaction of poly‐(1,3‐phenyl‐1,4‐phenyl)‐hydrazide into poly‐(1,3‐phenyl‐1,4‐phenyl)‐1,3,4‐oxadiazole has been studied using thermogravimetry (TG). For the evaluation of the energie of activation and other kinetic parameters of this cyclo dehydration reaction a method developed by Ozawa was used, where polymer samples are heated with different constant heating rates. With this method the energy of activation can be determined accurately as a function of the degree of conversion. In this way a parallel reaction could be observed starting at the end of the nonisothermal conversion process. The polymer was used in two different morphological states, a powder and a film. A slightly higher energy of activation and a considerably higher pre‐exponential factor were observed for the film indicating a dependency of the kinetics on the morphological state or on the history of the polymer sample.
Cyclo dehydration reaction of polyhydrazides. II. Kinetic parameters obtained from isothermal thermogravimetry
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

The kinetics of the thermal conversion reaction of poly‐(1,3‐phenyl‐1,4‐phenyl)‐hydrazide into poly‐(1,3‐phenyl‐1,4‐phenyl)‐1,3,4‐oxadiazole have been studied with isothermal thermogravimetry in continuation of a study with nonisothermal thermogravimetry described in a previous paper. Although the isothermal measurements are much more time‐consuming, they provide some new information and insight about the cyclo dehydration reaction of the polyhydrazide. The physical state of the sample, rubbery or glassy, seems to influence the kinetics considerably. The kinetic parameters determined with the isothermal method for the polymer in its glassy state agree well with the parameters derived from the previously reported nonisothermal measurements, while the kinetic parameters for the expected rubbery state differ considerably. The morphological state or the history of the polymer has also a considerable influence on the kinetics of the isothermal conversion process. The powder form of the polymer has a much lower isothermal conversion rate than the film form.
Tough epoxy resins cured with aminimides
Authors: Inubushi Shinzo , Ikeda Tomiki , Tazuke Shigeo , Satoh Tasuku , Kumagai Yaomi
Published: April 2003

Aminimide compounds (1–4) thermally generating isocyanates and tertiary amines were found to be excellent curing agents for epoxy resin. Tensile behavior, glass transition temperature, and degree of curing for the combination of EPIKOTE 828 prepolymer with a series of curing agents (1–4) are reported. The resins exhibit a large elongation at breakage and a high fracture energy per unit volume. The epoxy resins (EP‐AI) cured with 3 or 4 containing no hydroxyl group showed larger ultimate elongations (up to 15%) and higher fracture energies (ca. 8 J/cm3) than the resins (EP–AIOH) cured with 1 or 2. The curing reaction depends on the structure of aminimide (presence of hydroxyl group and generation of mono‐ or bisisocyanates). The origin of toughness and dependence of physical properties on the curing condition and the structure of aminimides were discussed. It was concluded that relatively slow curing at elevated temperature controlled by thermal decomposition of aminimides was a reason for the toughness.
Copolymerization of diethyl 2‐(methacryloyloxy) ethyl phosphate with alkyl acrylates: Reactivity ratios and glass transition temperatures
Authors: Nair C. P. Reghunadhan , Clouet G. , Brossas J.
Published: April 2003

Soluble copolymers of diethyl 2‐(methacryloyloxy) ethyl phosphate (DMP) with methyl methacrylate (MMA), methyl acrylate (MA), ethyl acrylate (EA) and butyl acrylate (BA) were synthesized by radical copolymerization in benzene solution using azobis(isobutyronitrile) (AIBN) as initiator. The monomer reactivity ratios of these systems at 60°C were determined by the conventional schemes using the methods of Fineman–Ross, Joshi‐Joshi, and Kelen–Tüdos. DMP underwent a completely random and azeotropic copolymerization with MMA whereas in its reaction with the other acrylates DMP entered preferentially into the polymer chain. The reactivities of DMP‐terminated polymer radicals towards the acrylate monomers were found to be in the order: MMA > EA > MA > BA. An increase in solvent polarity decreased the relative reactivity of DMP for the DMP‐MMA pair. An examination of the molecular weights of the copolymers revealed the occurrence of chain transfer caused by DMP. The copolymer glass transition temperatures were determined and the variations of Tg with copolymer compositions were discussed according to the theory of Johnston, taking into account the effect of the sequence distributions of the comonomers on Tg. The Tgs of the alternating copolymers of DMP with the four alkyl acrylates were calculated.
Synthesis and electrical conductivity of poly(arylene vinylene). I. Poly(2,5‐dimethoxyphenylene vinylene) and poly(2,5‐dimethylphenylene vinylene)
Authors: Antoun S. , Karasz F. E. , Lenz R. W.
Published: April 2003

The highly conjugated aromatic polymers, poly(2,5‐dimethoxyphenylene vinylene) and poly(2,5‐dimethylphenylene vinylene), were obtained from their water soluble, sulfonium salt precursor polymers. Films of these polymers were reacted with either AsF5 or I2 vapor. Poly(2,5‐dimethoxyphenylene vinylene) showed increases in electrical conductivity of up to 14 to 15 orders of magnitude for these two dopants, while an 8 to 9 order of magnitude increase was observed for poly(2,5‐dimethylphenylene vinylene) with the same dopants. The synthesis of the precursor polymers, the properties and elimination reactions of films of the precursors, the doping reactions, and the conductivities of the resulting phenylene vinylene films are discussed.
Epoxidation of polybutadiene and styrene–butadiene triblock copolymers with monoperoxyphthalic acid: Kinetic and conformation study
Authors: Huang Wen‐Kuei , Hsiue Ging‐Ho , Hou Wei‐Hsin
Published: April 2003

The rates of epoxidation of polybutadiene homopolymers and styrene–butadiene triblock copolymers with monoperoxyphthalic acid were measured at four temperatures in homogeneous solution. Dioxane and mixed solvents with chloroform were used as reaction media. Activation energy values were also calculated for polymers different in microstructure and styrene content. Viscometry in a modified viscometer was performed and combined with kinetic measurement to monitor the conformational change during epoxidation. Cis‐content in polybutadiene and styrene content in SBS exhibit only slight effect on epoxidation in dioxane. The addition of chloroform promotes the reaction rate remarkably and enlarges the difference between polymers. Explanations were given including the solvent effect on reduced viscosity, which was used to correlate the conformational change of polymer chains. NMR and GPC analysis confirmed the absence of ring opening and degradation during epoxidation up to 54% epoxy group content.
High temperature phosphorylated or nonphosphorylated laminating resins based on maleimido‐substituted aromatic s‐triazines
Authors: Melissaris Anastasios P. , Mikroyannidis John A.
Published: April 2003

Several new phosphorylated or nonphosphorylated maleimide or nadimide systems containing s‐triazine rings were synthesized. Their synthesis was accomplished by simple methods utilizing readily available and relatively inexpensive starting materials. All polymer precursors were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. They were thermally polymerized to heat‐resistant laminating resins. Thermal characterization of monomers and their cured resins was achieved using differential thermal analysis (DTA), dynamic thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). The cured resins were stable up to 304–330°C both in nitrogen and air atmospheres and formed anaerobic char yield 49–59% at 800°C. The phosphorylated polymers showed a lower temperature of initial weight loss but afforded higher anaerobic char yield than did the corresponding nonphosphorylated polymers. The thermal properties of the polymers were correlated with their chemical structure.