Novel synthetic strategies and molecular engineering to ultra-high performance electro-optic materials

The essential requirements for high-performance organic electro-optic (EO) materials are that individual chromophore components have large molecular hyperpolarizabilities (beta) and that they be arranged in a noncentrosymmetric architecture. Accordingly, the primary goals of this dissertation are to develop efficient approaches to constructing microstructural acentricity in bulk materials and to develop novel high-beta chromophores. A new, expeditious siloxane-based layer-by-layer assembly methodology for the formation of intrinsically polar EO thin films is described using highly reactive -SiCl2I derivatives of a protected azobenzene chromophore and a chlorosiloxane deprotecting/capping reagent. This all-"wet-chemical" two-step process can be efficiently implemented in a vertical dipping procedure to yield robust, structurally regular self-assembled superlattices (SAS) exhibiting appreciable EO responses (chi(2) ∼180 pm/V and r33 ∼65 pm/V at 1064 nm). The present film assembly is at least one order of magnitude more rapid than previous siloxane-based self-assembly methodologies.; The capability to tune the SAS materials properties is demonstrated by the design, synthesis, and self-assembly into intrinsically acentric EO thin films of a novel type of "X-shaped" two-dimensional EO chromophore, which features a remarkably blue-shifted optical maximum while maintaining a very large beta (HRS-derived betazzz = 1840 x 10-30 esu at 800 nm). Self-assembled chromophoric films exhibit a dramatically blue-shifted lambdamax (325 nm) and large EO responses (chi (2) ∼232 pm/V at 1064 nm; r33 ∼43 pm/V at 1550 nm). These results demonstrate an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.; The first synthetic realization of a series of unconventional twisted pi-electron system EO chromophores is presented. A full complement of solid state and solution characterization relevant to understanding structural characteristics, electronic structure, aggregation behavior, and the exceptional NLO/EO properties of this unconventional chromophore family is described. This includes molecular hyperpolarizabilities as high as 15x greater than previously reported (EFISH-derived mubeta as high as -488,000 x 10-48 esu at 1907 nm) and poled polymers with EO responses 3-5x greater than achieved heretofore ( r33 as high as 330 pm/V at 1310 nm). This work demonstrates a new paradigm for molecular hyperpolarizability and organic electro-optics.