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

Phase behavior of poly(pyromellitimide)s having (n-alkyloxy)methyl side cha ins (-CH2OCmH2m+1, m=4, 6, 8) has been studied by wide angle X-ray scatteri ng, differential scanning calorimetry and C-13 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 chai n (m=8), which is assigned to mesophase-mesophase transition. All the sampl es 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 laye red mesophase at high temperature. In the high temperature mesophase, the m ain chains do not form two-dimensional crystals in each layer; only the lat eral packing of the main chains remains undisrupted.