Dendronized Polyfluorenes with High Azo-Chromophore Loading Density: Convenient Synthesis and Enhanced Second-Order Nonlinear Optical Effects.

Two new dendronized nonlinear optical (NLO) polyfluorenes were synthesized with high azo-chromophore loading density by the introduction of high generation chromophore dendrons on the side chains. Thanks to the advantages of Sharpless’ click chemistry reaction, the dendrons were conveniently bonded to the backbone of polyfluorene with the conversion of 100%, although they were really very bulky. The new-formed triazole rings in the dendrons acted as suitable isolation groups to minimize the strong dipole−dipole interactions among the polar chromophore moieties to improve NLO effects, according to the results obtained from UV−vis spectra and order parameters. All the polymers were well characterized and exhibited good solubility, high thermal ability, wide optical window, and large NLO effects (up to 106.0 pm/V). In addition, the tested NLO results of these dendronzied polymers demonstrated a deviation from the dipolar frustration that typically limits the NLO effect in conventional chromophore/polymer composite materials, indicating that the frequently observed asymptotic dependence of electro-optic activity on chromophore density may be overcome through rational design. [ABSTRACT FROM AUTHOR]