Synthesis and polymerization of trifluorovinylether-terminated imide oligomers. I

The objective of this research was the preparation of imide trimers, terminated with trifluorovinyl ether groups, that could be melt processed and then polymerized to high molecular weight via the thermal dimerization of the trifluorovinyl ether moieties. The work was begun with the synthesis of an aromatic amine end-capping agent containing trifuorovinyl ether functionality, i.e. 4-(trifluorovinyloxy)aniline (TFVA). Melt-processable imide trimers were prepared from the end-capping agent and 2,2'-bis [4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BisA-DA) and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). The trimers underwent thermal cyclopolymerization to afford polyimides containing perfluorocyclobutane (PFCB) rings. The DSC thermogram of the imide trimer prepared from TFVA and BisA-DA contained a melting endotherm with a minimum of 153 degrees C and a polymerization exotherm with a maximum at 220 degrees C. The thermogram of the trimer prepared from TFVA and 6FDA had a melting endotherm with a minimum at 136 degrees C and a polymerization exotherm with a maximum at 244 degrees C. The PFCB-containing polyimides obtained from the melt polymerizations had intrinsic viscosities of 0.63 and 0.31 dl/g, respectively. The TFVA/BisA-DA polymer had a T-g of 186 degrees C, while the T-g of the TFVA/6FDA polyimide was 206 degrees C. The coefficient of thermal expansion of a thin film of the TFVA/BisA-DA polyimide was 57.1 x 10(-6) (C-degrees)(-1). The film displayed a tensile strength of 88 MPa, a modulus of 21 13 MPa, and elongation at break of 6.5%. The water absorption of this polyimide was 0.08%. (C) 2000 Elsevier Science Ltd. Ail rights reserved.