Multi-POSS cluster-wrapped polymers and their block copolymers with a PEO bottlebrush polymer: synthesis and aggregation

Abstract

In this paper, we report an approach for synthesizing multi-cluster-wrapped polymers and their block copolymers with a bottlebrush polymer with controlled chain length and composition via living ring-opening metathesis polymerization. To wrap more than one cluster on a polymer backbone, two to four polyhedral oligomeric silsesquioxane (POSS) clusters were firstly placed at the periphery of low-generation monodendrons to generate cluster-dendrons. Then, norbornene monomers that contain the cluster-dendrons and also one cluster were synthesized. Finally, the polymerization of these monomers was carried out using a Grubbs catalyst under mild conditions to generate multi-POSS cluster-wrapped polymers. Meanwhile, their block copolymers with a bottlebrush polymer that contains a polyethylene oxide were also prepared. Both the absolute and relative molecular weights of the polymers and block copolymers were determined using size-exclusion chromatography with both on-line light-scattering and refractive index detectors. Our analysis of their molecular weights indicates that the differences between absolute and relative molecular weights increase when the POSS number in the side moieties increases from 1 to 4. Thus the size of the micelles of the block copolymers formed via solution self-assembly increases with increasing POSS number due to the stretching of the polymer chains.