The morphology and crystal structures of poly(2,6-naphthalene terephthalate) (PNT) and poly(2,6-naphthalene naphthalate) (PNN), prepared by confined thin film melt/solution polymerization (CTFMP/CTFSP), were characterized by transmission electron microscopy, electron diffraction and molecular modeling. The unit cells of PNT and PNN are both monoclinic (P12(1)/a1 space group) with parameters a = 8.18 angstrom, b = 5.80 angstrom, c = 14.9 angstrom and beta = 101.9 degrees for PNT, and a = 7.85 angstrom, b = 5.97 angstrom, c = 17.1 angstrom and beta = 99.5 for PNN, respectively. Simulated ED patterns from the proposed unit cells agree well with the observed ED patterns. The crystal structures of PNT and PNN are also compared with those of poly (p-phenylene naphthalate) (PPN) and poly(2,6-oxynaphtalate) (PONA). (c) 2006 Elsevier Ltd. All rights reserved.