Synthesis and polymerization of trifluorovinylether-terminated imide oligomers. I

Abstract 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 trifluorovinyl 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°C and a polymerization exotherm with a maximum at 220°C. The thermogram of the trimer prepared from TFVA and 6FDA had a melting endotherm with a minimum at 136°C and a polymerization exotherm with a maximum at 244°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 Tg of 186°C, while the Tg of the TFVA/6FDA polyimide was 206°C. The coefficient of thermal expansion of a thin film of the TFVA/BisA-DA polyimide was 57.1×10−6(°C)−1. The film displayed a tensile strength of 88 MPa, a modulus of 2113 MPa, and elongation at break of 6.5%. The water absorption of this polyimide was 0.08%.