Novel fluorinated long linear segment hyperbranched polyimides bearing various pendant substituents for applications as optical materials

Four novel hyperbranched polyimides (HBPI) (a-d) with long linear segments have been synthesized from a triamine monomer and a series of diimide-diacid monomers (I-IV). All of these HBPIs exhibit good solubility as well as excellent thermal stability. As a result of the presence of long linear segments in the hyperbranched structure, the HBPI films exhibit better flexibility than previously reported polymers, with an elongation at break of 6.7–7.2%. Each of these HBPIs has a cutoff wavelength that is shorter than 356 nm. In addition, all of the HBPIs exhibit a high optical transmittance at 800 nm. The refractive indices of the HBPIs were investigated, and the values were found to be in the range of 1.5631–1.5727 at a wavelength of 650 nm, and the refractive index by copolymerization of HBPI is adjustable. Furthermore, the HBPI films obtained via spin-coating presented extremely low birefringence values (0.0013–0.0021), and low NIR absorption losses of 1310 and 1550 nm at the communication windows.