Guest-host systems and NLO polymers

Fundamentally, there are two categories of second-order NLO polymeric systems, commonly also referred to as electro-optically active polymeric systems [4, 

In this context, research concerning non-centrosymmetric structures with su-pramolecular helical organization is interesting. In the case of thermally stable (up to 400 °C) polyesters containing Ti-conjugated donor-acceptor segments (see Chart 3.4), the hyperpolarizability values, p, turned out to be much larger than those of the respective monomeric chromophores. 

At a chiral unit content of 50%, the second harmonic generation (SHG) efficiency of the polymer (at 2 = 532 nm) is 4.8 times that of the monomer, and P is equal to 20.7x10 esu. This enhancement may be rationalized in terms of the directional orientation of dipole segments in the polymer as a consequence of the chiral organization of the polymer chains [37]. 

Typical low molar mass AnD compounds and polymers containing AnD moieties are listed in Table 3.2 [38] and Table 3.3 [39, 40]. In this context, it is noticeable that electro-optically active compounds have been tabulated [7]. 

Chart 3.4 Chemical structures of an electro-optically active polyester and a chemically related monomer. 

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