Synthesis and polymerization of trifluorovinylether-terminated imide oligomers. I

The objective of this research was the preparation of imide trimers, termin ated with trifluorovinyl ether groups, that could be melt processed and the n 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 functionali ty, i.e. 4-(trifluorovinyloxy)aniline (TFVA). Melt-processable imide trimer s were prepared from the end-capping agent and 2,2'-bis [4-(3,4-dicarboxyph enoxy)phenyl]propane dianhydride (BisA-DA) and 2,2'-bis(3,4-dicarboxyphenyl )hexafluoropropane dianhydride (6FDA). The trimers underwent thermal cyclop olymerization to afford polyimides containing perfluorocyclobutane (PFCB) r ings. 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 polyme rization exotherm with a maximum at 220 degrees C. The thermogram of the tr imer 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-D A polymer had a T-g of 186 degrees C, while the T-g of the TFVA/6FDA polyim ide 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 d isplayed a tensile strength of 88 MPa, a modulus of 21 13 MPa, and elongati on at break of 6.5%. The water absorption of this polyimide was 0.08%. (C) 2000 Elsevier Science Ltd. Ail rights reserved.