Synthesis and nonlinear optical properties of novel polyurethanes with high thermal stability of dipole alignment

2,3-Di-(2′-hydroxyethoxy)-4′-nitrostilbene (2) was prepared and condensed with 2,4-toluenediisocyanate (TDI), 3,3′-dimethoxy-4,4′-biphenylenediisocyanate and 1,6-hexamethylenediisocyanate to yield polyurethanes (3–5) containing the nonlinear optical (NLO)