Design, synthesis and characterization of novel second-order nonlinear optical chromophores with fused-ring polyenes for application in polymeric electro-optic modulators

This dissertation is focused on the design and synthesis of high mubeta chromophores for application in EO modulators. Development of novel pi-conjugation bridges and acceptors has been carried out. An investigation into establishing structure/property relationships with regard to photostability issues has been attempted. Chapter 1 presents an introduction into electro-optic phenomenon and theoretical background of optical nonlinearity.; Chapter 2 details the development of novel phenyl tetraene and phenyl pentaene NLO chromophores with fused rings namely DRCR and DRELCR Series. Synthetic methodologies for the construction of fused-ring structures are being discussed. The chromophores thermal and optical properties were measured by TGA and UV/vis, respectively. Locking two methine bonds, as in DRCR, does not improve the thermal stabilities relative to the corresponding single-locked ones. A DRELCR chromophore of an exceptionally large hyperpolarizability has been synthesized, namely GLD. (r33) values as high as 108 pm/V at 1.06 mum has been measured at only 15-wt% in PMMA composites using the ATR technique.; Chapter 3 presents photostability and optical loss studies of a series of short chromophore structures for possible use in applications at 980 nm. The design of the six representative chromophores has been discussed with regard to photostabilty. B-values measured by pump-probe at 545 mn were compared to the literature data and some structure/property trends discussed. B-value as high as 107 has been achieved in one isolated case. Most high mubeta chromophore photostability is in the range of 105--10 6, far from the target value of 109.; Chapter 4 deals with a novel acceptor for NLO chromophores, namely malononitrile dimer. Based on its structural similarities to the TCF acceptor, the properties of the two acceptors were compared. For that purpose, a systematic structure/function study was attempted by gradually increasing the conjugation length and varying the substituents on the amine group of the acceptor. It was concluded that compared to the TCF acceptor, malononitrile dimer has lower chemical and thermal stability and causes red shift of the absorption maximum in short donor-acceptor polyenes.