Photo-crosslinkable second-order nonlinear optical polymer: facile synthesis and enhanced NLO thermostability

Abstract

A new photo-crosslinkable second-order nonlinear optical (NLO) linear polymer was designed and successfully prepared by the azido-alkyne click reaction, in which the azo-benzene moieties acted as the chromophore. The latent double bonds in the polymer could undergo the subsequent thiol–ene click reaction with the addition of pentaerythritol tetra(3-mercaptopropionate)(PETMP) as the controlled photo-crosslinking, with the aid of UV lamp irradiation. Accordingly, the photo-crosslinked thin films exhibited much enhanced stability of the macroscopic second-order NLO effect. Thanks to the advantages of the azido-alkyne and thiol–ene click reactions, the syntheses were very simple and the post crosslinking process was convenient. Under the optimized conditions, the T_80% of the photo-crosslinked thin films (103 °C) was much higher than that of the controlled ones (57 °C), thus opening up a new avenue for the improvement of device stability.