Synthesis and properties of carborane-containing dendronized polymers

Carborane-containing dendronized polymers were successfully synthesized using two different approaches up to the fourth generation. Nitroxide-mediated polymerization (NMP) was effective for the polymerization of carborane-functionalized styrenic monomers, leading to well-defined polymers with high boron content and narrow molecular weight distributions (PDI < 1.1). The resulting carborane-functionalized polymers could then be dendronized using a divergent approach to introduce aliphatic polyester dendrons of generation 1-4 grafted from the polymer backbone. This first approach afforded a maximum degree of dendronization of 70%. To increase the degree of dendronization, a first-generation macromonomer was polymerized using NMP to yield a fully functionalized first-generation dendronized polymer. This material was also dendronized up to the fourth generation. Both approaches produced water-soluble dendronized polymers (1 mg/mL in pure water) with high molecular weights (in excess of 70 kDa). It was found that the solubility of the polymer produced from the second approach, where dendronization occurred at every monomer unit, exceeded that of the first approach.