Hyperbranched Poly(p‐phenylene ethynylene)s

Abstract

Abstract Hyperbranched poly( p ‐phenylene ethynylenes) (HB‐PPEs) were synthesized in an A 2 + B 3 one‐pot approach by the Pd/Cu‐catalyzed cross‐coupling reaction of 1,4‐diethynyl‐2,5‐bis‐(octyloxy)benzene and 1,2,4‐tribromobenzene. Reaction conditions were varied with the objective to obtain well‐defined HB‐PPEs of different molecular weights. HB‐PPEs with $\overline M _{\rm w}$ from 11 000 to 237 000 g · mol −1 and PDIs of 1.5–10.7 were prepared. All polymers that comprised unreacted ethynyl groups eventually became insoluble upon drying, presumably as a result of solid‐state cross‐linking. This reaction could be prevented by endcapping the polymers with an excess of 4‐iodotoluene. magnified image