Development of novel crosslinkable polymers for second-order nonlinear optical devices

We have synthesized different nonlinear optical responsive chromophores with imidazolidine-2,4-dione, pyrimidine-2,4,6(1H,3H,5H)-trione and 3-pheny-2-isoxazolin-5-one as acceptors. With these, a series of crosslinkable polymers were synthesized using phenylenediacryloyl chloride, tolylene-2,4-diisocyanate and 4,4′-methylenedi(phenyl isocyanate). The molecular structural characterization of these polymers was achieved by FTIR, UV–vis, 1H NMR and elemental analysis. The inherent viscosities of these polymers (η inh) determined by Ubbelohde viscometer, were in the range of 0.26–0.29 dl/g. Thermal behavior of these polymers was investigated using differential scanning calorimetry and thermogravimetric analysis. The glass transition temperatures (Tgʹs) of the resulting polymers were in the range of 97–175 °C. The change in the molecular alignment in the polymer films after electrical poling was ascertained by atomic force microscopy. The resulting polymers exhibited an excellent solubility in many of the common organic solvents, suggesting that these polymers offer good processability. The second harmonic generations (SHG) coefficients (d33) of poled polymers determined by Maker fringe technique were in the range of 44–109.07 pm/V at 532 nm, signifying the acceptability for nonlinear optical devices.