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Synthesis and characterization of poly(ε-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(ε-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 ε-caprolactone and 19 of styrene and low polydispersity. The resulting polymer, still preserving the central aromatic di-bromo 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.