SHG characterization of different polar materials obtained by in situ photopolymerization

The structural, thermal, and nonlinear optic (NLO) characterization of diff erent polar materials is reported. These materials, which range from side-c hain polymers to anisotropic networks and gels, were prepared by in situ ph otopolymerization of their precursors in the ferroelectric SmC* liquid crys tal phase. The influence of the structure, the percentage of cross-linker, and the degree of mobility of a common NLO-phore on the second harmonic gen eration (SHG) activity have been considered with the aim of analyzing the m ost suitable approach for practical applications. Slight improvements in th e SHG d(ij) coefficients of these polymeric materials compared to their par ent low molecular mass starting compounds have been observed. However, from these studies, it can be stated that side-chain polymers and low cross-lin king polymers are the most interesting materials from the point of view of both the NLO-activity and the ease of synthesis. These two types of materia ls provide stable room temperature thin films displaying SHG and electroopt ic (EO) responses without the application of a poling field.