ISSN:
0959-8103
Keywords:
polyimide
;
m-cresol
;
phase structure
;
morphology
;
phase boundary diagram
;
gel/sol transition
;
DSC
;
polarized light microscopy
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
An organo-soluble aromatic polyimide has been synthesized from 3,3′, 4,4′-bis(phenyltetracarboxylic) dianhydride (BPDA) and 2,2′-bis (trifluoromethyl)-4,4′-diaminobiphenyl (PFMB) via a one-step polymerization in m-cresol. The phase boundary diagram for this system has been established by differential scanning calorimetry, polarized light microscopy (PLM) and wide angle X-ray diffraction (WAXD) experiments. A crystallosolvate form I has been found over the entire concentration region at low temperatures. When the temperature is increased, an isotropic phase has been observed below concentrations of about 40%. In the relatively high concentration region between 45 and 95%, a transition from the crystallosolvate from I to a crystallosolvate form II has been observed. Form II exhibits a different WAXD pattern. In a narrow concentration region between the isotropic and the crystallosolvate form II (40-45%), a biphase behavior has been found. The birefringence of this region may be an indication of a liquid crystalline phase. The BPDA-PFMB polymer crystal has been found in the very high concentration region (〉95%) for temperatures 〉250°C. The morphologies of these phases have been investigated via PLM and transmission electron microscopy. Above the gel/sol transition temperature, the form I shows negative birefringent spherulites consisting of thin lamellae. The form II exhibits a tendency of positive birefringent spherulites. Possible mechanisms of the formation of the metastable phase morphology and their associations with the mechanical gel/sol transition are also discussed.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pi.1995.210370309
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