Phase behavior of poly (pyromellitimide)s having flexible (n-alkyloxy)methyl side chains

Summary

Phase behavior of poly(pyromellitimide)s having (n-alkyloxy)methyl side chains (-CH₂OC_mH_2m+1, m=4, 6, 8) has been studied by wide angle X-ray scattering, differential scanning calorimetry and ¹³C solid-state NMR. While there are no observable transitions in the polymers bearing short side chain(m=4, 6), there is one transition in the polymer bearing the longest side chain(m=8), which is assigned to mesophase-mesophase transition. All the samples show layered mesophase at room temperature, in which the side chains are amorphous but the main chains form two-dimensional crystals in each layer. In the polymer bearing the longest side chain(m=8), it shows another layered mesophase at high temperature. In the high temperature mesophase, the main chains do not form two-dimensional crystals in each layer; only the lateral packing of the main chains remains undisrupted.