Synthesis and characterization of poly(epsilon-caprolactone)-b-polystyrene macromonomer by combined ring-opening and atom transfer radical polymerizations and its use for the preparation of grafted polyphenylenes by Suzuki polycondensation

A poly(epsilon-caprolactone) (PCL) hydroxy telechelic having a central 2,5-dibromo-1,4-phenylene moiety was reacted with 4-bromomethyl benzoyl chloride to give a bifunctional macroinitiator for ATRP. The polymerization of styrene (St) in the presence of benzyl bromide functionalized PCL afforded a well-defined block-co-polymer having 25 repeating units of epsilon-caprolactone and 19 of styrene and low polydispersity. The resulting polymer, still preserving the central aromatic dibromo groups, can be used in Suzuki or Yamamoto polycondensations for the synthesis of poly(p-phenylenes) (PPPs) bearing block-co-polymers as side chains. The bromo-functional macromonomer was tested in a Suzuki-type cross-coupling reaction in combination with 2,5-dihexylbenzene-1,4-diboronic acid. This way a polymer with alternating hexyl and PCL-b-PSt side chains was obtained. The intermediate polymers and final PPPs were analyzed by spectral, GPC and DSC measurements.