Polyimides from isomeric oxydiphthalic anhydride

Isomers of 3,3, 4,4 -oxydiphthalic anhydride(3,3, 4,4 -ODPA), i.e., 2,2, 3,3 -oxydiphthalic anhydride (2,2, 3,3 -ODPA) and 2,3,3, 4 -oxydiphthalic anhydride (2,3,3, 4 -ODPA) were synthesized. Polyimides were prepared from these dianhydrides, and their 

The polyimides from these dianhydrides and diamines, 4,4 -ODA and l,4-bis(4aminophenoxy)benzene (1,4,4-APB), were s5mthesis by the two-step procedure in DMAc. The polyimides from 2,2, 3,3 -ODPA were obtained by chemical imidation and the polyimides from 2,3,3, 4 -ODPA and 3,3,4, 4 -ODPA were obtained by thermal imidation (40°C/12 h, 80°C/1 h, 220°C/1 h, 300°C/0.5 h) (Eq. 6). 

The Tg values move towards higher temperatures in the order of PI(3,3,4, 4 -0DPA) PI(2,3,3, 4 -0DPA ) PI(2,2, 3,3 -ODPA). This is rationalized in terms of restriction of internal rotation around the ether linkage between the phthalimides, as seen in the polyimides from BPDA. The rotation axes of the two aromatic rings of 2,2, 3,3 -ODPA are nearly perpendicular, and the rotation is strongly resisted. The polyimide structure is therefore nonlinear nonlinear 

The Tg values of PI(2,3,3, 4 -ODPA/4,4 -ODA) and PI(2,23, 3 -ODPA/4,4 -ODA) were lower than those of the corresponding the pol)dmides from BPDA due to the presence of the ether bonds between the phthalimides. 

---

A series of 15 wt % isomeric polyimide precursor resin solutions was prepared by the National Aeronautics and Space Administration Langley Research Center. The polymerization procedure has been described previously (2,3). The poly(amic-acid) resin solutions were made from 3,3, 4,4 -benzophenonetetracarboxylic acid dianhydride (BTDA), 4,4 -oxydiphthalic anhydride (ODPA), diaminobenzophenone (DABP), and methylenedianiline (MDA) monomers. 

---