In order to establish the structure of the title polymer, P6BP, two model compounds, di-n-hexyl 4,4’-biphenyldicarboxylate (6BP6) and hexamethylene di-4-biphenylcarboxylate (BP6BP) were synthesized and their crystal structures were established by X-ray diffraction. The unit cell of 6BP6 is orthorhombic (a = 7.754 (2), b = 11.428 (5), and c = 54.39 (4) Angstrom; space group Pbca). The crystal structure of 6BP6 was solved from single crystal diffraction data (R = 0.067). BP6BP is dimorphic : the a-form, whose structure was established (R = 0.043), has a monoclinic unit cell (a = 7.1039 (3), b = 8.1298 (3), c = 22.2308 (4) Angstrom, and a 94.531 (4)degrees; space group P2(1)/c); the beta-form, which is obtained upon cooling of the melted alpha-form, is also monoclinic (a = 13.42, b = 7.59, c = 12.95 Angstrom, and beta = 95.4 degrees). The aliphatic segments in both 6BP6 and alpha-BP6BP are in the all-trans conformation. The biphenyl dihedral angles are 35.5 degrees and 21.1 degrees for 6BP6 and alpha-BP6BP, respectively. The equivalent fiber repeats, calculated from both model compounds, are 19.568 (12) and 19.599 (6) Angstrom for 6BP6 and BP6BP, respectively. In the crystal, the 6BP6 molecules adopt a parallel disposition and the aromatic groups are arranged in a face-to-face pattern. The alpha-BP6BP molecules pack in layers; the chains in the adjacent layers have different orientations, while the biphenyl rings adopt the herringbone pattern.