Poly(p-phenylene) graft copolymers with polytetrahydrofuran/polystyrene side chains

1,4-Dibromo-2,5-bis(bromomethyl)benzene was used as a bifunctional initiator in cationic ring opening polymerization (CROP) of tetrahydrofuran. The resulting macromonomer, with a central 2,5-dibromobenzene ring, was reacted in combination with 2,5-dihexylbenzene-1,4-diboronic acid by a Suzuki coupling, in the presence of Pd(PPh3)4 as catalyst, leading to a poly(p-phenylene) (PPP) with alternating polytetrahydrofuran (PTHF) and hexyl side chains. A polystyrene (PSt) based macromonomer with a central benzene ring bearing cyclic boronic acid propanediol diester groups, synthesized by atom transfer radical polymerization (ATRP), was also used as partner for PTHF in the cross-coupling reaction. A PPP with alternating PSt and PTHF side chains was obtained. PTHF macromonomer was also homopolymerized by a Yamamoto reaction. The resulting PPPs have high solubility in common organic solvents at room temperature. The new polymers were characterized by GPC, 1H NMR, 13C NMR, IR and UV analysis. Thermal behavior of the precursor PTHF macromonomer and the final polyphenylenes were investigated by TGA and DSC analyses and compared.