Novel Branched Polyphenylenes based on A 2 /B 3 and AB 2 /AB Monomers via Diels‐Alder Cycloaddition

Summary: Novel hyperbranched polyphenylenes based on both an A 2  + B 3 and an AB 2  + AB approach were synthesised and characterised. Different monomers were prepared and polymerised using a Diels‐Alder reaction with subsequent decarbonylation. The polymer backbones consist of hexaphenylbenzene units which are linked in different positions and functionalised by cyclopentadienone (A) and/or alkyne groups (B) depending on the monomer ratio. The structure and properties of the resulting polymers were compared to those of hyperbranched polyphenylenes based solely on an AB 2 monomer. All branched products showed high thermal stability and good solubility in common organic solvents such as chloroform or toluene. However, due to steric hindrance, the polyphenylenes produced using the A 2  + B 3 approach exhibited a high percentage of linear units within the polymer structure.Schematic structure of hyperbranched polyphenylenes from A 2 and B 3 monomers.