Photo-induced denitrogenation of triazoline moieties for efficient photo-assisted poling of electro-optic polymers

• Published in: Polymer chemistry 2013-01, Vol.4 (16), p.4434-4441
• Main Authors: Li, Ming, Jin, Zhian, Cernetic, Nathan, Luo, Jingdong, Cui, Zhanchen, Jen, Alex K.-Y
• Format: Article
• Language: English
• Subjects: Backbone; Chromophores; Denitrogenation; Deoxidizing; Electro-optics; Polymers; Thin films; Triazolines
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/c3py00480e

Efficient room temperature poling of a guesthost electro-optic (EO) polymer is achieved by photo-induced denitrogenation of triazoline moieties. The host polymer ( P1 ) with 2 -1,2,3-triazoline groups on the backbone is synthesized by 1,3-dipolar cycloaddition polymerization between a bis- N -phenylmaleimide and an aromatic bis-azide. The guest chromophore ( C1 ) is a pushpull compound with a strong dialkylaminophenyl donor and a CF 3 TCF acceptor. By irradiating the thin films of P1 with a compact UV lamp at 365 nm, the angular and asymmetric 1,2,3-triazoline structures can be readily converted into a more straight and symmetrical aziridine structure by losing nitrogen. This photo-induced denitrogenation provides the clean conversion to form an aziridine-based polymer P2 . This high efficiency conversion process is insensitive to the light-absorbing nonlinear optical chromophores, and the reaction rate can be controlled by the irradiation power and the thin film UV absorbance. Upon the photo-induced denitrogenation, considerable structural change of the polymer backbone provides sufficient rotational freedom to the chromophores for the poling of EO polymers. This has been verified by the demonstration of high field poling (up to 250 V m 1 ) and large EO activity at RT for thin films containing 2025 wt% of chromophore C1 in P1 , which can be efficiently activated by photochemical denitrogenation of triazoline moieties by irradiating with low-power UV light. Photo-induced denitrogenation of triazoline moieties enables efficient high-field poling of guesthost EO polymers under ambient conditions.