Polycondensation Knoevenagel

Monomer 33 was made to undergo transesterification polymerization using Ti(OC4H9)4, while monomer 34 was appropriate for a Knoevenagel polycondensation. The transesterification polymerization resulted in the formation of an intractable material of unknown structure. Homopolymerization of 34 by the Knoevenagel technique afforded polymer 35 with a low molecular weight (M 6800). A major byproduct in this polymerization was a macrocyclic lactone, formed via an intramolecular Knoevenagel condensation (Scheme 10-14). 

Typically, in the Knoevenagel polycondensation, a terephthalic aldehyde is condensed with a bis-(cyanomethyl)-benzene compound. Since two monomers are used, PPVs with a strictly alternating structure can be synthesized. The Knoevenagel polycondensation allows the convenient synthesis of compounds in that the backbone double bond is substituted. PPV modified with cyano groups show a high EL activity. The synthesis is shown in Figure 3.8. In a quite similar way, PPV can be formed by the Wittig... 

Typically, in the Knoevenagel polycondensation, a terephthalic aldehyde is condensed with a bis-(cyanomethyl)-benzene compound. Since two... 

Also, polymers that contain carbazole moieties in the backbone with two acceptor groups as multifunctional chromophores were synthesized. The sytheses were carried out by a Knoevenagel polycondensation of divinylcarbazoles with bis(cyanoacetate)s using 4-(N,N -dimethyl)pyridine as a base. Second-order nonlinear optical properties of the polymers were confirmed by second harmonic generation. The photorefractive optical gain of these polymers was demonstrated to be high. 

Ferrocene polymers with nonlinear optical properties were also prepared via Knoevenagel polycondensation reactions. " Scheme 32 shows the reaction of monomer 123 with 124 to give the accordion polymer 125 with values ranging from 9100 to 26,600." A mixture of A and Z isomers was initially obtained however, an isomerically enriched polymer (98% E isomer) could be isolated through selective precipitation. 

Quite impressive device efficiencies are obtained with CN-PPV 22, a cyano-substituted PPV daivative which is synthesized by a Knoevenagel polycondensation of terephthaldehyde 20 with dinitrile 21 under carefully controlled reaction conditions (Figure 11.13). Single-layer devices of CN-PPV show red light emission and efficiencies up to 0.2% with both Ca and A1 cathode contacts. The introduction of cyano... 

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