Photoinduced synthesis of oligoesters

For the first time, a true step-growth polymerization, i.e, polyesterification, was achieved by a photochemical means. Thus, heterobifunctional monomers, namely benzodioxinone and naphthodioxinone compounds possessing both chromophoric and aliphatic hydroxyl groups in the structure (HDPD and HDNP, respectively), were synthesized by a ring closure and subsequent etherification processes and characterized. Photolysis of these compounds in CH₂Cl₂ at λi_inc = 300 nm yielded oligoesters with narrow molecular weight distribution. In the case of HDNP, photolysis can be performed at higher wavelengths, e.g., at λ_inc = 350 nm, because of the extended absorption introduced by the naphthalene ring. The structure of the photochemically formed oligoester was confirmed by FT-IR and ¹H NMR spectral measurements.