| Recent progress of electro-optic (E-O) polymers has shown great promise for applications in photonic devices such as high speed E-O modulators and switches due to their large E-O coefficients, ultra-fast response times, and ease of process. However, there are several important properties of E-O polymers that need to be improved before they can be incorporated in practical devices. These include E-O coefficients, thermal, chemical and photochemical stabilities, temporal dipole alignment stability, optical loss, and mechanical properties. To address these molecular, material and device issues, significant efforts have been invested in the design and synthesis of highly efficient nonlinear optic chromophores by manipulating the shape, size and functionality of these donor-acceptor substituted conjugated building blocks. For example, a diversified family of 2,5-dihydrofuran derivatives was synthesized through focused single-mode microwave irradiation. The tunable electron-withdrawing ability in the resulting “mixed” 2,5-dihydrofuran acceptor system has allowed us to achieve a balance of molecular nonlinearity, absorption at near-IR region, and thermal, chemical and photochemical stabilities of the resulting NLO chromophores. Very large E-O coefficients and excellent temporal stability were achieved in these optimized guest/host systems. Furthermore, hydroxyl containing 2,5-dihydrofuran derivatives have been synthesized through focused microwave irradiation as effective electron acceptors to be incorporated into NLO chromophore platforms where high molecular nonlinearity and hydroxy functionality can be integrated simultaneously in single molecular entity. Thus these multi-functionalized chromophores can be tailored at molecular scale to afford the desired topologies such as, dendronized NLO chromophore, NLO dendrimer, and dendritic side-chain polymer systems.; For conjugation bridge part, efficient ring-locked polyene bridges were employed in chromophore structures to realize an ideal combination of molecular nonlinearity, thermal and chemical stabilities.; Besides the adjustment of acceptor strength and effective conjugation length to improve molecular nonlinearity, geometrical functionalization of chemically inert dendron as bulky side group onto chromophores was also applied to improve poling efficiency. E-O property of the resulting poled polymers was significantly enhanced due to reduction of the intermolecular electrostatic interactions among large dipole chromophores. |
