A modular approach for making second-order nonlinear optical (NLO) side-chain aromatic polyquinolines has been developed. The synthesis provides a method for readily incorporating NLO chromophores into the pendent phenyl moieties of parent polyquinolines at the final stage via the Mitsunobu reaction. The method produces polyquinolines with a wide range of polymer backbones and offers great flexibility in the selection of NLO chromophores. These side-chain NLO polyquinolines demonstrate high electro-optic (E-O) activities (up to 35 pm/V at 830 nm and 22 pm/V at 1300 nm) and excellent tradeoffs among thermal, optical, and electrical properties.
Most recently, a series of novel second-order NLO thermoset polymers containing silicon-perfluorocyclobutane (PFCB) has also been synthesized. This was accomplished via the crosslinking reaction between the di(trifluorovinylether)-containing NLO chromophores and the tris(trifluorovinylether) monomer in solid state at 180-250 °C. The radical-mediated, stepwise cycloaddition reaction offers great tolerance to very sensitive functional groups such as tricyanovinyl acceptor. A variety of NLO chromophores could be easily incorporated into these thermoset polymers compared to the modular approach. Preliminary results have indicated these polymers to possess excellent processability, low optical loss, and a combination of highly desirable thermal, nonlinear optical, and mechanical properties.