Photo-degradation of Di- and Trifunctional Oxime Ethers Bearing Polyphthalaldehyde Arms

Abstract

Polyphthalaldehyde (PPA) is a representative degradable polymer that can be end-to-end depolymerized. Herein polymers bearing two and three PPA chains have been prepared, and their photochemical behaviors were investigated. The PPA chains were linked to fluorene and truxene cores via oxime ether units that are photoreactive moiety. Di- and trifunctional PPAs were obtained by anionic polymerization of phthalaldehyde monomer (o-PA) initiated by corresponding oximes and 1,8-diazabicyclo[5.4.0]undec-7-ene, even though the conversion of was low after purification. From the 1H NMR spectral changes of CDCl3 solutions of both PPA on irradiation with Hg-Xe lamp, it was found that PPAs decreased along with the formation of o-PA, and then the o-PA reduced along with the formation of phthalide. PPAs were also coated on CaF2 substrates and irradiated with the lamp. UV spectral changes of the films showed the photochemical reaction of oxime ether moieties, and IR spectral changes indicated the formation of phthalide. These results clearly show that depolymerization and following photo-isomerization into phthalide proceeded both in solution and solid state. 2,7-Diacetylfluorene O,O'-dibenzyldioxime was newly prepared to discuss the photochemical reaction of oxime ether with fluorene chromophore.