Synthesis of end-capped polyester from SmI2-catalyzed Tishchenko-type polyaddition of dialdehydes

SmI₂-catalyzed polyaddition of 1,12-dodecanedial followed by treatment with benzaldehyde gives a polyester (1) containing three structural units, OCH₂-(CH₂)₁₀-CH₂O], OCH₂-(CH₂)₁₀-CO], and CO-(CH₂)₁₀-CO], in the main chain and an OCH₂Ph end-capping group. GPC analysis of 1 shows molecular weights of M_n = 5.5 × 10³ and M_w = 14 × 10³. The ¹H-NMR spectrum reveals the polymer structure with the COOCH₂Ph end group as well as the M_n value (2.6 × 10³) calculated based on an amount of the end-capping group and lower than that estimated from GPC. Mixtures of terephthalaldehyde and 1,12-dodecanedial in several molar ratios undergo similar polyaddition catalyzed by SmI₂ to give the corresponding copolyesters after treatment with benzaldehyde. Increase in the ratio of 1,12-dodecanedial causes increase in yield and molecular weight of the copolymer. Terephthalaldehyde shows a tendency to give alcohol-side —O—R—O— unit in the polyester, whereas 1,12-dodecanedial is mostly incorporated as the acid-side —CO—R′—CO— unit. Terminal aldehyde group derived from dodecanedial is capped effectively by benzaldehyde to give the COOCH₂Ph end group. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2821–2825, 1997