Poled, doped polymers, thermal effects

Thermal Effects on Dopant Orientation in Poled, Doped Polymers... 

Figure 26.7 shows the chemical structures of an NLO chromophore (APAN) and an epoxy-based polymer (BPAZO) where NLO moieties are attached to the backbone [81]. Both the dye and the polymer are functionalized with thermally cross-linkable acryioyl groups. As the dye-doped polymer is subjected to heat as part of the simultaneous poling/curing process, the inter- and intramolecular cross-linking reactions occur simultaneously (Fig. 26.8). The 7g of the cross-linked polymer-dye network is lower than that of the undoped polymer network because of the plasticizing effect of the dissolved dye. However, the temporal stability at 100°C of the polymer-dye network is better than that of the undoped polymer network (Fig. 26.9) as a direct result of the increased cross-linking density in the cross-linked guest-host system. Therefore, the addition of the thermally cross-linkable NLO dye not only increases the...

At this time, molecularly doped poled polymers appear to fall somewhat short in the magnitude of the nonlinear coeflScient (27, 28). As will be shown in the following paragraph this fact is primarily due to the competition between molecular orientation and thermal randomization. This competition emphasizes the importance of having a high concentration of dopant molecules and favorable thermodynamic factors to suppress thermal-randomization effects. 

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