Geometrical influence of ABn monomer structure on the thermal properties of linear-hyperbranched ether-ketone copolymers prepared via an AB+ABn route

A series of poly(ether ketone) copolymers were prepared by nucleophilic aromatic polymerization reactions of 4-fluoro-4′-hydroxybenzophenone, 2, in the presence of varying percentages of ABn monomers based on a triarylphosphine oxide platform, 1a (2F), 1b (4F), and 1c (6F), where A=OH and B=F. As expected, the crystallinity of the samples decreased with an increasing ABn content. However, the tetrahedral geometry of the phosphine oxide-based ABn monomers proved to be much more efficient at lowering the melt temperature of the copolymers than was the corresponding ketone-based ABn monomer, 3,5-bis(4-fluorophenylbenzoyl)phenol, 4, that possesses a structure more similar to that of 2. Polymerization of 2 in the presence of as little as 5 mol% of bis-(3,4,5-trifluorophenyl)-(4-hydroxyphenyl)phosphine oxide, 1c (6F), afforded a completely amorphous polymer with a glass transition temperature of 168 °C that was soluble in hot NMP and DMSO. The copolymers also exhibited excellent thermoxidative stability with a number of samples displaying 5% weight loss temperatures, in air, well in excess of 500 °C.