摘要:

AbstractA series of hot‐melt processable thermosetting compositions was prepared by blending N,N,N′,N′‐tetraglycidyl‐4,4′ ‐diaminodiphenyl‐methane/4,4′‐diaminodiphenylsulfone (TGMDA/DDS) epoxy resin and thermoplastic polymer powders with average particle size below 30 μm. The basic thermoplastic polymers were either a high Tgamorphous cardo polyimide (Tg=350°C) or commercial semicrystalline PA6 and PA12 polyamides. The resulting heterogeneous mixtures showed viscosity values below 5000 cps suitable for prepregging process. After cure, phase‐separated morphologies were maintained with a rather limited interphase miscibility as demonstrated by thermomechanical analysis. Scanning electron microscope examination of fracture surfaces pointed out a strong adhesion between the powder particles and the surrounding polyepoxy network, particularly for the potentially reactive polyamide structures. Moreover, as shown by differential scanning calorimeter analysis, the crystallinity ratio of the PA6 and PA12 powders was lowered due to melting during thermal polymerization. The fracture toughness properties of the powder‐containing materials were compared with those of a fully miscible cardo polyimide–TGMDA/DDS blend coming from an homogeneous resin composition. The best improvement in fracture energy was obtained for the powder‐modified resins. The most effective composition filled with 16 wt% of powdered polyimide exhibited a fourfold increase in GIC(388 J/m2versus 100 J/m2) without compromising the epoxy thermomechanical stab

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060401

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe two independent elements of the second‐order nonlinear optical susceptibility tensor of a range of contact poled, donor–acceptor substitued side‐chain polymers are reported. The susceptibilities were measured by second harmonic generation from thin films, typically less than 0.5 μm thick, at a fundamental wavelength of 1064 nm. The largest value was χ (2)36= 2.64 pm/V which is three times greater than the χ (2)36value of KDP and was measured in a nitrobenzylidene side chain, polyhydroxystyrene polymer with an eleven unit alkyl chain spacer attaching the side group to the backbone. Typical susceptibility values obtained were χ (2)31∼0.3 pm/V and X(2)33∼1 pm/V. The coherence lengths of the materials, which lay in the range 4–12 μm, were measured at 1064 nm by the maker fringe technique using thick

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060402

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mean‐square molecular dipole moments 〈μ2〉 of carbazole, N‐ethylcarbazole and of the sequence of poly(epoxypropylcarbazole) (PEPCa) oligomers of various molecular weights have been evaluated in solutions of these organic compounds in dioxan. For PEPCa the values of 〈μ2〉 have also been determined in the solid state. On the basis of the experimental results and of molecular mechanics calculations it has been shown that the orientation of the lateral group of PEPCa favors noninteracting racemic dyads. The temperature‐dependence of the effective dipole moment of solid PEPCa follows the Onsager the

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060403

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSpirobenzopyran1, with the 3‐(diethoxymethylsilyl)‐propyl group at the N atom, was synthesized. The condensation reaction of the spiropyran1and diethoxydimethylsilane gave oligomeric poly(dimethylsiloxane) with the spiropyran moiety in the side chain. The oligomer was photochromic; its colour changed from colorless to purple‐red on uv irradiation and the color faded on visible irradiation or on standing in the dark. The half‐decay time of the thermal decoloration was about twice that of monomeric spiropyran dissolved in the dimethylsiloxane oligomer. Photochromic poly(dimethylsiloxane) with the spirooxazine moiety in the side chain was also p

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060404

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractMany alkali metal carboxylates when dissolved in poly(ethylene oxide) (PEO) oligomers, are phaseseparated by heating. These were revealed to be the crystals of the initially dissolved corresponding salts from the X‐ray diffraction patterns. Some acetate salts achieve the lower limit of the lattice energy for phase separation of ordinary inorganic salts by heating in PEO oligomers. These carboxylate salts were therefore expected to show crystallization behavior in PEO oligomers by heating. The effects of cation size, alkyl chain length and molecular weight of PEO on the solubility are summarized. Negative temperature dependence of solubility of these acetate salts is seen in the PEO oligomers only when the salts have long alkyl chains. The salts containing larger cations needed a longer chain length of PEOs for crystallization by heating. These salts with longer alkyl chains showed positive temperautred dependence in lower molecular weight polyethers, but negative temperature dependence in solubility in PEO with molecular weights higher than 400. In PEO400, all the carboxylates with longer alkyl chains were phase separated by heatin

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060405

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of substituents on the electropolymerization of benzene derivatives and the redox properrties of the corresponding polymers were determined using Brown's substituent constants (σ+). Electron‐donating groups lower the oxidation potential by which increase in the current efficiency was observed. However, stabilization of the produced cation radicals by the electron‐donating groups resulted in a decrease in the polymerization efficiency. The appropriate values of σ+for the efficient polymerization ranged near

ISSN:1042-7147    

DOI:10.1002/pat.1995.220060406

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY