A poly(polyoxometalate)-b-poly(hexanoic acid) block copolymer: synthesis, self-assembled micelles and catalytic activity

Abstract

A hybrid block copolymer (H-BCP) composed of a poly(polyoxometalate) (poly(POM)) block and a poly(6-norbornene-hexanoic acid) (poly(COOH)) block was prepared by sequential addition of two norbornene monomers containing a POM cluster and a carboxyl as side groups via ring-opening metathesis polymerization (ROMP). Because the 5833 Da molecular weight of the POM-containing monomer is much higher than 277 Da of the carboxyl-containing monomer, the designed H-BCP has a degree of polymerization DP = 5 for the poly(POM) block and DP = 200 for the poly(COOH) block. Thus, the H-BCP not only has differences in its chemical structure and properties but also asymmetries in its molecular weight and length. In acetonitrile, it self-assembles into hybrid micelles with a thin shell of the poly(POM) block and a core of the poly(COOH) block. The micelles form thin films in which the micelles pack into a hexagonal pattern driven by attractive capillary forces between the micelles. Meanwhile, the H-BCP exhibits good catalytic activity. The H-BCP may become an important candidate for producing hybrid materials with good processability and ductility of the polymer components, and good functionality of the POM clusters.