Solution behavior of dendrimer-coated rodlike coordination polymers

We report here the synthesis and self-assembly behavior of a series of three coordination polymers (1-3) insulated with different generations and lengths of oligoether dendrons. Their self-assembly behavior in solutions was investigated according to the variation in generation of dendrons and solvent polarity by using spectroscopic measurements, molecular calculation, and transmission electron microscopy (TEM). In contrast. polymer 1 based on first-generation dendrons with diethylene oxide unit and polymers 2 and 3 based on higher volume fractions of dendrons are readily soluble in common organic solvents and H2O. Polymer 2 based on first-generation dendrons with triethylene oxide unit was observed to self-assemble into nanorods consisting of two pi-stacked polymer backbones in both nonpolar CHCl3 solvent and film, whereas 2 exists as isolated single polymer chains in polar solvents. Polymer 3 based on second-generation dendrons with tetraethylene oxide units also exists as isolated single polymer chains in both solution and film states. Notably, the CHCl3 solution of 2 at concentrations above 2 wt % was observed to be a nematic fluid, resulting from the formation of rigid polymer backbone driven by pi-stacking, whereas the THF Solution of 2 undergoes gelation at concentrations above 2 wt %. The primary driving force for this unique self-assembling behavior is proposed to be the solvation ability of solvent molecules to silver salts and the coverage ability of dendrons to insulate the conjugated backbones.