Spacers, nonlinear optics, molecular materials

Ferrocene-containing polymers with long spacers have been prepared as new nonlinear optical (NLO) materials for second harmonic generation (SHG) applications (e. g. frequency doubling) [10], The use of ferrocene derivatives in this area is attractive as a result of their demonstrated large hyperpolarizability values combined with their thermal and photochemical stabilities [11], These factors make polyferrocenes desirable candidates for use as processable NLO materials. The polyurethane copolymer 4.4 was synthesized using a functional ferrocene monomer (Eq. 4.1) and has been well-characterized the molecular weight was estimated by GPC to be Mn=7600. The two possible orientations of the ferrocene NLO chromophore monomer unit, which correspond to opposite dipole orientations, were both present in the main chain. 

One of the advances in the field of PET is the design of molecular devices, in which D and A pairs are ingeniously linked by covalent bridges (B) to form D-B-A dyads. Electron transfers between D and A across B in a controlled manner may thus display useful functionalities, such as molecular rectifiers [25], switches [26], biosensors [27], photovoltaic cells [28], and nonlinear optical materials [29]. Spacers that have been utilized are versatile, including small molecules, such as cyclohexane [30], adamantane [31], bicyclo[2.2.2]octane [32], steroids [33], and oligomers of... 

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