Jacketed poly(p-phenyleneethynylene)s:: Nonaggregating conjugated polymers as blue-emitting rods

A series of dendronized poly(p-phenyleneethynylene)s were synthesized by the Pd-catalyzed coupling of a tetraphenylbenzene-substituted aromatic diiodide to 2,5-didodecyl-1,4-diethynylbenzene to form PPEs in excellent yield and high degree of polymerization. The tetraphenylbenzene-substituted monomer was obtained by a Diels-Alder reaction of a diethynylated arene with tetraphenylcyclopentadienone. The influence of the tether length (connecting the tetraphenylbenzene units to the main chain of the polymer) on the optical properties of the polymers was investigated. The closer the tetraphenylbenzene units were placed to the main chain, the larger is their effect upon the PPE's optical properties. In the case where the tether is shortest, i.e., two atoms, the optical properties of the PPE in the solid state and in solution are identical.