Self-metathesis of erucic acid by [(PCy3)(eta-C-C(3)H(4)N(2)Mes(2))Cl2Ru = CHPh] (Grubbs secondgeneration catalyst) followed by catalytic hydrogenation and purification via the ester yields 1,26-hexacosanedioate (>99% purity). Polyesterification with 1,26-hexacosanediol, generated from the diester, affords polyester-26,26, which features a T-m of 114 degrees C (T-c = 92 degrees C, Delta H-m = 160 J g(-1)). Ultralong-chain model polyesters-38,23 (T-m = 109 degrees C) and-44,23 (T-m = 111 degrees C), generated via multistep procedures including acyclic diene metathesis polymerization, underline that melting points of such aliphatic polyesters do not gradually increase with methylene sequence chain length. Available data suggest that to mimic linear polyethylenes thermal properties, even longer sequences, amounting to at least four times a fatty acid chain, fully incorporated in a linear fashion are required.