Persistent, efficient frequency doubling by poled annealed films of a chromophore-functionalized poly(p-hydroxystyrene)

An attractive alternative to poling glassy polymers simply doped with nonlinear optical (NLO) chromophores^2-4 are materials in which NLO chromophores are covalently linked to the polymer backbone, thus offering potential impediment both to phase separation at high chromophore densities and to deleterious relaxation of poling-induced chromophore alignment. The authors report here an embodiment of this strategy which employs structure-enforcing hydrogen-bond networks, achieves high chromophore densities, and affords polymer films with persistent (on a timescale of months) second-harmonic coefficients equal to or in excess of the corresponding value for LiNbO₃. General observations relevant to NLO film processing and the applicability of current theoretical models are also reported. The results considerably expand what is known about the properties of NLO chromophore-functionalized polystyrenes. Equally important, they suggest future synthetic and processing strategies for materials with even more efficient frequency-doubling properties.