Synthesis and characterization of polyimides from 1,4-bis[4-(n-alkyloxy)phenyloxy]pyromellitic dianhydrides and 4,4'-oxydianiline

Summary

New pyromellitic dianhydrides having (n-alkyloxy)phenyloxy (-O-Ph-O-n-C_mH_2m+1, m=1,4,8,12) side chains were synthesized and polymerized with 4,4'-oxydianiline (ODA) in NMP at room temperature. Imidization was carried out using triethylamine and acetic anhydride. The synthesized polyimides (C_m-OPIs) were characterized and their properties were measured and discussed in respect to the effects of side chains. Inherent viscosities of the polymers were in the 0.46 – 0.68 dL/g range. All the polymers were highly soluble in N-methylpyrrolidinone (NMP) and slightly soluble in DMSO, m-cresol, DMF and concentrated H₂SO₄ at room temperature. TGA pyrograms showed two-step degradation. In DSC thermograms the polymers exhibited T_g's between 219°C and 305°C and melting points near 350°C were observed in C₈- and C₁₂-OPIs. Wide-angle X-ray diffractometry for as-polymerized samples revealed very low crystallinities and layered structures which were better developed in the polymers with longer side chains.