Structure and properties of N-octadecylated poly(p-phenylene terephthalamide)

Abstract

N-octadecylated PPTA's with various molecular weights were synthesized from PPTA and n-octadecyl bromide via the metalation reaction. The polymer exhibited side-chain crystallization at 314 K due to the long alkyl side chains and both crystallinity and the perfection of the crystal increase with increasing in the molecular weight. The results of IR spectra and the wide angle X-ray indicate that the polymer crystallizes in hexagonal form. The mechanical and the dynamic mechanical properties of N-octadecylated PPTA's were measured. Two tan δ peaks were observed in a temperature range of 310–350 K and at 260 K, respectively, which can be designated αc and αa relaxation, respectively. The concentrated solutions of N-octadecylated PPTA's in tetrahydrofuran, dichloroethane, tetrachloroethane, and bromoform showed liquid crystalline behavior of lyotropic type.