Synthesis and second-harmonic generation study of DCM-containing polyurethane

Dicyanomethylene-2-methyl-5-(4-dialkylaminostyryl)-4H-pyran (DCM) moiety was incorporated into the rigid polyurethane to give strong NLO activity and thermal stability. The DCM-containing dihydroxy monomer was prepared with conventional Knoevenagel condition and reacted with 4,4-methylenebis(phenyl isocyanate) to form a functionalized polyurethane. The successful polymerization reaction was identified with several methods such as NMR, FT-IR, UV–VIS absorption spectroscopies. The resulting polymer was soluble in polar solvent such as DMF, DMAc and thin films could be obtained by spin-casting of its solution. From these, we investigated the second-order NLO properties of polymer films by using second-harmonic generation method.