ABSTRACT
HONG-SHEN LI, JIN-GANG LIU, LIN FAN and SHI-YONG YANG* Laboratory of Advanced Polymer Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
Abstract-Two novel fluorinated aromatic dianhydrides, 4,4’-[2,2,2-trifluoro -1-(3’-trifluoromethylphenyl)ethylidene] diphthalic anhydride (m-HFDA) and 4,4’-[2,2,2-trifluoro-1-(3’,5’-bis(trifluoromethyl)phenyl)ethylidene]diphthalic anhydride (9FDA), were synthesized and employed to polycondense with various aromatic diamines, including 4,4’-oxydianiline (ODA), 1,4-bis(4-aminophenoxy) benzene (APB) and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) to produce two series of fluorinated aromatic polyimides (PI-I series, based on m-HFDA, and PI-II series, based on 9FDA). The fluorinated polyimides obtained had inherent viscosities in the range of 0.461.14 dl/g and easily dissolved both in polar aprotic solvents, as well as in low-boiling-point common solvents. High-quality polyimide films could be prepared by casting the polyimide solution on a glass plate followed by thermal baking to remove the organic solvents and volatiles completely. Experimental results indicated that the fluorinated polyimides exhibited good thermal stability with the glass transition temperature in the range of 245-283°C and the temperature at 5% weight loss of 500-546°C. Moreover, the polyimide films showed outstanding mechanical properties with tensile strengths of 85.9-131.3 MPa and elongations at break of 5.0-12.6% and good dielectric properties with low dielectric constants of 2.71-2.97 and low dissipation factors in the range of 0.00130.0032.
