Cyclobutane Ring Cleavage of CBDA-ODA Polyimide Molecules Induced by Linearly Polarized UV Light

Abstract

We have determined the initial cleavage rate of the cyclobutane ring of poly[4,4′-oxydiphenylene-1,2,3,4-cyclobutanetetracarboximide] (CBDA-ODA) for linearly polarized ultraviolet light (LPUVL). The initial cleavage rates β// and β/ for LPUVL polarized parallel and perpendicular to the polyimide backbone direction, respectively, were determined from the IR absorption data reported previously. β// and β⊥ are 0.70 ± 0.02 and 0.13 ± 0.02 J−1 cm2, respectively, for LPUVL of wavelength 248 nm. We found that the anisotropy of the cleavage rate is much larger than that of the phenyl ring decomposition rate for poly[4,4′-oxydiphenylene-pyromellitimide] (PMDA-ODA) that was previously reported. The large anisotropy of the cyclobutane ring cleavage is advantageous to photo-induced alignment of liquid crystals based on the decomposition reaction of polyimide molecules.