摘要:

AbstractA new method of measuring the environmental stress cracking (ESC) of polymers at constant strain is proposed in which an occurrence of fracture is detected automatically. The new method showed a very good reproducibility within 10% compared with a few hundred percent by conventional methods.The ESC values obtained by the new method was found to be proportional to those by the conventional Bell Telephone Laboratory method in which the ESC was determined by the occurrence of small cracks, with a proportionality contant of 2.8. From the fact that the difference of both ESCs were also proportional to the ESC determined by the BTL method, it was concluded that the value of the ESC was proportional to the velocity of crack propagation. These conclusions were supported by the observation of the test pieces by a scanning electron microscope.The study of the blended polymers revealed that the additivity of logarithmical ESC with weight fraction holds for a wide range of polymes, which enables estimation of ESCs up to millions of hours.Using this technique, the ESCs of a wide range of molecular weights and a number of short chain branches were studied. It was found that the branches in the high molecular weight polymer were much more effective on the ESC than those in the low molecular weight polymer. This makes it possible to design a good resin with a good ESC.

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060901

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractHexacene (HEX) and derivatives such as dihydrohexacene and dihydroxyhexcane quinone were synthesized and thin films of them were prepared by the sublimation method. The structure and conductivity of the films both before and after doping with iodine were studied. The doped HEX film showed the conductivity of 3 × 10−2S/cm at room temperature, which was lower than expected since the conductivity of highly ordered pentacene was above 100 Ω−1cm−1. The reason for the low conductivity was considered to be the disorder in molecular alignment since the HEX film showed an amorphous structure. A reversible change in the conductivity of the HEX film was observed in air and in

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060902

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractHighly sensitive gas sensors for both acidic and basic gases were fabricated based on conducting thin films of polyacene compounds. Gas sensors formed with pentacene thin films deposited on various kinds of substrates were found to exhibit high sensitivity in detecting subppm concentrations of NO2or Cl2by monitoring the conductivity of the thin film. Improvements in the conductance and duration period for detection were achieved by changing the shape of electrodes and substrate. The sensors with PEN thin films initially doped with iodine could detect ppm concentrations of ammonia gas, since iodine molecules were dedoped upon exposure to ammonia, causing the reduction of the conductivity.

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060903

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSuperlattice thin films of pentacene (PEN) and tetracene (TET) were fabricated by alternate layer deposition using the sublimation method. The film showed a highly crystalline structure that was due to the strong aggregation tendency of polyacene compounds to form a layered monomolecular column structure. The crystalline structure of the films was drastically changed by doping with iodine. The doped films showed a highly ordered structure where an iodine monomelecular layer was intercalated between molecular columns of acene compounds in both PEN and TET. The doped films exhibited a large lateral conductivity of 10 Ω−1cm−1and attained giant anisotropy above 1012. This indicated that molecular columns of TET remained insulating upon doping to form a perfect two‐dimensional conductor in the superlattice thin

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060904

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe phase behavior of ternary blends was analyzed on the basis of the lattice approach. Both compatibilization and incompatibilization effects are predicted to occur depending on the relative magnitudes and the sign of the interaction parameters of the binary subsystems. Thermodynamic, structural and kinetic properties were investigated for a ternary model blend composed of poly(vinylidene fluoride), poly(methyl methacrylate) and poly(vinyl acetate). This particular ternary system is characterized by a specific symmertry with respect to the interactions in the binary subsystems. This symmetry affects both thermodynamic and structural properties. The experimentally determined interaction parameters were used to model the phase diagram on the basis of the lattice model: the theoretical phase diagram was found to be close to the experimental one. The crystallization processes were analyzed both for the binary and the ternary systems on the basis of a modified Turnbull–Fisher equation. The conclusions are that the properties of the ternary systems can be understood to a first approximation on the basis of those of the corresponding binary systems and the symmetry of the interaction

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060905

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractPhotocrosslinkable second‐order nonlinear optical (NLO) polymers were synthesized from cationic copolymerization of a vinyl ether monomer bearing 4′‐nitrobiphenyl‐4‐oxy group as the NLO chromophore with a vinyl ether monomer bearing cinnamoyl group as the photoreactive moiety. To obtain a suitable poling method involving photocrosslinking, which is capable of inducing a higher and more stable second‐order nonlinear coefficient, d33, for NLO polymer films, some poling procedures were investigated. An optimized poling method was as follows. Ultraviolet (UV) irradiation is performed for 90 sec during poling at 50°C for 20 min, followed by poling at 150°C for 20 min. By using this poling method NLO polymer films exhibited a higher and considerably stable d33value at room temperature, even though they had rather lower glass transition temperatures before photocrosslinking. Some photocrosslinking mechanism for NLO polymers investigated here we

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060906

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060907

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060908

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060909

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY