摘要:

AbstractWhen 4,4'‐bis (3,4‐dicyanophenoxy) biphenyl is heated with small amounts of aromatic amine or amidine salts, a highly crosslinked polytriazine is obtained. This polymer has been shown to be the same as that reported when bisphthalonitriles are heated with amines. Salts promote this reaction more readily and the glass transition temperature of the polymer after post‐cure at 315°C is generally 30°C higher than when free bases are used. The fracture properties and elasticity of the salt‐cured polymer have been measured at temperatures up to 250°C. As a model system, the self reaction of phthalonitrile promoted by amines and their salts has been studied. In both cases, poly[4‐(2‐cyanophenyl)‐1,3,5‐triazine‐2,6‐diyl‐1,2‐phenylene] is produced, and more efficiently using the salts. A reaction mechanism for this polymerization has been proposed.

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320101

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSmooth, adherent films of the electrically conducting polypyrrole formed on surfaces in contact with unstirred aqueous solutions containing the pyrrole monomer and the oxidant, FeCl3. Contradictory reports in the literature concerning the influence of HCl on the growth rate and electrical conductivity of polypyrrole grown in this manner prompted this study of the growth rate and conductivity of films. With no intentional addition of HCl, the growth rate of the films, measured using a quartz crystal microbalance, was fit to a simple second‐order model in which the rate was limited by the bulk depletion of reactants. The conductivity of the films was found to be about 1 S cm−1. Both the growth rate and the electrical conductivity initially increased with the deliberate addition of HCl to the solution. The conductivity was found to peak at a value about 20 S cm−1at an initial HCl concentration of 0.3M. At initial HCl concentration of 2Mor more, films could not be grown. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320102

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe chemical reactions occurring in the melt mixing of nylon6/polycarbonate (Ny6/PC) at 240°C were investigated. The reaction of equimolar Ny6/PC blends can be reconciled within the overall scheme of an exchange reaction occurring with the attack of active amino terminals on the inner carbonate groups. We have performed the synthesis of low molecular weight amino‐terminated nylon 6 and the effect of the active amino terminal groups on the exchange kinetics was investigated. The exchange reaction yields sizeable amounts of copolymer, in fact after 75 min of melt mixing the (initially equimolar) blend contains 30 mol of unreacted PC and 70 mol of Ny6/PC copolymer (all the Ny6 was therefore incorporated in the copolymer). Trifluoroacetylation of nylon 6 was used to produce CHCl3‐soluble Ny6/PC copolymers, that could be analyzed by NMR. The NMR analysis yielded, beside the copolymer composition, evidence of the presence of urethane units interconnecting the Ny6 and PC blocks. The amount of urethane units increased with the reaction time, indicating a reduction of the block size as a function of the extent of exchange. Our study established the structure of the products formed, provided the materials balance of the process, and investigated some salient kinetic aspects. A thermal degradation study was also performed by thermogravimetry and direct pyrolysis mass spectrometry, to identify the products formed in the thermal treatment of the blends and to investigate the possible role of the inner amide groups in the intermolecular exchange reactions occurring between Ny6 and PC. Our results prove that these reactions occur above 300°C, and that only the cleavage of carbonate groups, by means of Ny6 amino end groups, is actually occurring at 240°C. © 1994 John Wiley&So

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320103

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolypyrrole (PPy) was deposited electrochemically on a platinum plate from a nitric acid solution of pyrrole. The PVC/PPy composite film was finally obtained by casting poly(vinyl chloride) (PVC) onto the PPy electrode from a tetrahydrofuran solution of PVC. The prepared composite film was irradiated at 90°C with a low‐pressure mercury lamp in the stream of hydrogen gas saturated with steam, and the PVC film was dehydrochlorinated, leading to the formation of conjugated polyene. The electrical conductivity (σ) of the PVC film in the irradiated composite film was reveled: σ=2.51 × 10−5S cm−1. By iodine doping, σ was further enhanced up to 5.04 X 10−3S cm−1. The tensile strength of the irradiated composite film became larger than that of the original PVC film; i.e., the stress at break was: 461 (composite film); 401 kg cm−2(PVC). These results were brought about by the doping of radical species to the conjugated polyene. The anion, NO−3, doped during the electrodeposition of PPy was photodecomposed to generate radical NO2and this species was doped to the polyene, resulting in the formation of electrically conductive PVC and mechanically improved composite film. © 1994 J

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320104

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractFluorination of low‐density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF6gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x‐ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley&Sons,

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320105

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractFive acrylic esters having different fluorine contents and distributions in their side‐groups (i.e., CH2=CHC(O)OR, where R = C(CH3)2C6F4H, C(CH3)2C6F5, C(CF3)2C6F5, C(CF3)2C6H5, and C(CH3)2C6H5) have been prepared from the reactions of the lithium salts of their corresponding alcohols with acryloyl chloride. These monomers are polymerized under identical conditions by the radical initiator AIBN and five polyacrylates were prepared having the structure of  [ CH2CHC(O)OR]n. These addition polymers were compared and fully characterized by GPC, VPO, DSC, TGA, NMR, IR, and UV‐visible spectroscopies, and they showed potential for practical applications. Significant differences in their thermal stabilities were found with respect to fluorine contents and distributions in these polyacrylates, and the highest stability arises from CF3substitutions in the side‐chains of the polymers. © 1

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320106

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of fluorine‐containing aromatic homopolyformal and copolyformals with a wide range of unit ratio were synthesized by the solution polycondensation of 2,2‐bis (4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane (Bisphenol AF) and/or 2,2‐bis (4‐hydroxyphenyl)propane (Bisphenol A) with dichloromethane, and the effect of the fluorine substitution on the preparation and properties of these polymers was investigated by comparing with those of Bisphenol‐A‐based homopolyformal without fluorine. Irrespective of the ratio of Bisphenol AF, high‐molecular‐weight, fluorine‐containing polyformals with reduced viscosities of 1.4–5.3 dL/g were obtained in high yields by using dichloromethane as both comonomer and solvent, potassium hydroxide as a base, and N‐methyl‐2‐pyrrolidone as a comedium at 75°C for 4 h. Their solubility increased markedly by the introduction of fluorine atom. Colorless, transparent, and tough films were cast from chloroform solution irrespective of fluorine content. These films had good mechanical properties comparable to that of Bisphenol‐A‐based homopolyformal. The contact angles by water were larger than 90°, regardless of their fluorine contents, at 25°C. The glass transition temperature and thermal stability increased monotonically with increasing fluorin

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320107

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe reaction of bis(4,7‐tetrahydrothiopheniomethyl) benzofuran dibromide with aqueous tetramethylammonium hydroxide leads to a water‐soluble polyelectrolyte which can be film cast and thermolytically eliminated to give poly(4,7‐benzofuran vinylene) (PBFV). Subjection of bis(4,7‐tetrahydrothiopheniomethyl) benzothiophene dibromide to the same reaction sequence gives poly(4,7‐benzothiophene vinylene) (PBTV). UV‐VIS studies show that PBFV has a band gap of 2.76 eV, while PBTV has a band gap of 2.92 eV. These polymers are members of a new class of conjugated poly (arylene vinylene)s, in which heterocyclic pseudoaromatic rings are fused onto a poly(1,4‐phenylene vinylene) backbone. © 1994 John W

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320108

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is shown that amine‐terminated poly(aryl ether ketone)s based on the reaction of 4,4'‐difluorobenzophenone, and a substituted hydroquinone [either methylhydroquinone (MePK),t‐butylhydroquinone (tBPK), or phenylhydroquinone (PhPK)] of controlled molecular weight and high amine‐termination efficiency can be synthesized by a two‐step reaction technique. Attempts to synthesize analogous materials by a one‐step method were shown to be unsuccessful. The side groups are shown to have a large influence on the aromatic proton chemical shifts and this effect is characterized. The side groups and molecular weight are also shown to influence the thermal transitions of the respective polymers. The tBPK polymer possessed the highest glass transition temperature, while the MePK polymer was found to be the only semi‐crystalline polymer; a unit cell is proposed. The side groups and molecular weight effects are also characterized as a function of thermal stability and mechanical properties. © 1994 John W

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320109

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThermotropic copolyamides were prepared from triethyleneglycol bis(4‐carboxy‐phenyl)ether (PEG3) and two types of diamines, substitutedp‐phenylenediamines and 4,4'‐diaminodiphenyls, and depression of melting point and isotropization temperature of the copolymers produced were measured as a function of diamine combination. The depression was not practically observed by the combinations of homologous diamines with several kinds and numbers of substituents, but significant by those of the diamines with different lengths of the mesogenic segments, and by the molar ratios of the diamines employed. The effect was discussed in terms of deviation of interchain hydrogen bonding between amide bonds in the main chain. © 1994 John Wiley&S

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320110

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY