Synthesis and characterization of aromatic polyketones and polyetherketones derived from divanillic acid via Friedel–Crafts acylation

Abstract

The present paper describes the synthesis and characterization of aromatic polyketones (PKs) and polyetherketones (PEKs) derived from divanillic acid (DVA) via Friedel–Crafts acylation. Various alkyl side-chains with carbon numbers of 2–8 were introduced into the hydroxyl groups of DVA units. Polyketones (PKs) were synthesized from DVA monomers and 2,2′-dimethoxybiphenyl, and polyetherketones (PEKs and PEKOMes; PEKOMes = polyetherketones with methoxy groups) were synthesized from DVA monomers and diphenylether and 3,3′-oxybis(methoxybenzene), respectively. Unexpectedly, some alkyl side-chains were eliminated during polymerization under Friedel–Crafts conditions in a polar solvent, and elimination was suppressed in a non-polar solvent. Longer alkyl side-chains were eliminated more easily. The molecular weights of the PKs, PEKs, and PEKOMes were 12.5–32.7 × 10³, 4.1–6.3 × 10³, and 10.6–15.3 × 10³ g/mol, respectively. DVA-based PKs and PEKs with relatively high molecular weights compared with those obtained by the previously reported method were obtained via Friedel–Crafts acylation. The aryl comonomers with methoxy moieties produced polymers with higher molecular weights, likely owing to their electron-donating properties. These polymers were all amorphous; their glass transition temperatures were 181–252 °C (PKs), 105–152 °C (PEKs), and 149–218 °C (PEKOMes).