Polycondensation reaction conjugated systems

NLO materials (16 and 17) (Fig. 13) have been obtained from polyurethanes by the incorporation of sidechains with boron chromophores.37 The dihydroxy ligand of an azobenzene ligand containing a dimesityl boron acceptor was reacted in a polycondensation fashion with the diisocyanate groups of the polyurethanes to yield the desired polymers. Halogen displacement and transmetallation reactions have been utilized in the development of extended ir-conjugated systems of tri-9-anthrylborane with dendritic structures.38 In one (18) (Fig. 14) of the novel compounds, three identical... 

If this complex is sufficiently stable, then no further reaction occurs, and the polycondensation is obviated. However, as mentioned above, by using controlled monomer design, a variety of functionalised polymers (typical by with Mn = 10 000—30 000 and Mw/Mn = 2.0) can be synthesised polyethers [15,48 50], poly(thioether)s [48], polyesters [51,52], polycarbonates [53], polyketones [54], polysiloxanes [55-58], poly(carbosiloxane)s [59], poly(carbosilane)s [60], poly(carbodichlorosilane)s [61] and polymers with a conjugated % system [62]. 

Population of oxime-hydroxylamine tautomers B and C can be high, since unlike the initial dioximes A, they are conjugated systems and the energy gain of their formation should be considerable. Besides, highly basic medium is favorable for prototropic migration of the double bonds and enolization. The essential contribution of tautomers B and C in overall reaction is supported by the formation of isoxazoles, the predictable intramolecular cyclization of the tautomer in their Z-configurations. It is obvious that tautomers B and C as very reactive species (combination of the oxime and hydroxylamine functions with azadiene system), in the system KOH/ DMSO/acetylene, can tolerate various reactions, namely, vinylation, cyclization, elimination, polymerization, and polycondensation. 

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