Dipolar Chromophore Facilitated Huisgen Cross-Linking Reactions for Highly Efficient and Thermally Stable...

Efficient thermal cross-linking protocol for an azide-alkyne-based Huisgen 1,3-dipolar cycloaddition reaction has been developed for making highly efficient electrooptic (EO) polymers. The material system is based on an azide-containing side-chain copolymer and cross-linkable dendronized chromophores that have two pairs of dendritic bispropargyl ether moiety on the periphery. The dendritic chromophore possesses a tetraene conjugating bridge and strong dialkylaminophenyl donor and CF₃-TCF acceptor. This material system not only provides adequate accessibility for propargyl ether to react azido-containing moieties for efficient cross-linking but also gives the rotational freedom needed for electric field poling. The site isolation offered by the bispropargyl ether dendron effectively suppresses the unwanted side reactions that are usually associated with the decompositions of azides and chromophores. Due to these concerted efforts, it allows the Huisgen 1,3-dipolar cycloaddition reactions to be carried out at moderate temperatures in polar media that have a high concentration of dipolar polyene chromophores. Through sequential electric field poling and in situ cross-linking, the poled films exhibit very large EO activity (up to 147 pm/V at 1.31 μm) with a long-term alignment stability at 85 °C.