Photocrosslinkable liquid prepolymers for flexible waveguide display applications

Abstract

We have prepared and evaluated two liquid prepolymers and their UV-cured films for flexible display applications. 2,3,5,6,2′,3′,5′,6′-Octafluoro-4,4′-bis-[2-(2-{2-[2-(2,3,5,6-tetrafluoro-4-vinyl-phenoxy)-ethoxy]-ethoxy}-ethoxy)-ethoxy]-biphenyl (7) and 2,3,5,6,2′,3′,5′,6′-octafluoro-4,4′-bis-[2-(2-{2-[1,1-difluoro-2-(2,3,5,6-tetrafluoro-4-vinyl-phenoxy)-ethoxy]-1,1,2,2-tetrafluoro-ethoxy}-1,1,2,2-tetrafluoro-ethoxy)-2,2-difluoro-ethoxy]-biphenyl (8) are synthesized with decafluorobiphenyl, 2,3,4,5,6-pentafluorostyrene, and tetraethylene glycol or fluorinated tetraethylene glycol. The UV-cured films prepared from these prepolymers show mechanical flexibility and optical transparency. The refractive indices and optical losses of the films prepared from prepolymers 7 and 8 are around 1.51 and 1.43, and 1.03 and 1.06 dB cm−1 at a wavelength of 633 nm. The films are thermostable at high temperature over 350 °C. The ultimate stress, initial modulus, and elongation of the films prepared from prepolymers 7 and 8 are 15.5 MPa, 0.42 GPa, and 12.2%, and 13.8 MPa, 0.49 GPa, and 6.8%, respectively. Finally, we have demonstrated a flexible waveguide display film fabricated from our prepolymers and identified the liquid prepolymers as possible good candidate materials for flexible display applications.