The linear polyurethane provided a high thermo-optic coefficient (d n/dT) of −3.63 × 10 −4 ☌ −1 (1550 nm). The urethane content of the UV-polymers was adjusted using composite films from a diacrylate-derived from 1,3-dithiane-attached diol. Urethane-diacrylate was prepared via a reaction of IPDI and 2-hydroxyethyl methacrylate, and a urethane-acrylate polymer film was produced under UV-irradiation. The polymers exhibited a glass transition at 71–131 ☌ and were stable up to ∼250 ☌. Three different linear polyurethanes were prepared from the polycondensation of isophorone diisocyanate (IPDI) and novel diols containing cyclic substituents, such as 1,3-dithiane, cyclic O,S-acetal and 1,3-dithiolane. The refractive index and thermo-optic coefficient (d n/dT) of linear polyurethanes and UV-cured polyacrylates were determined over a range of near infrared (NIR )wavelengths.
