Polyethersulfone

Polyethersulfone, commonly abbreviated PESU, is an aromatic polymer with ether and sulfone linkages in its polymer backbone. It belongs to the sulfone-containing engineering thermoplastics. The complete repeat unit, rather than the presence of one sulfur-containing group, distinguishes its chemical identity from related polysulfone and polyphenylsulfone materials.^[ref]

BASF identifies its PESU family as an amorphous thermoplastic. These terms answer different questions: amorphous concerns the absence of long-range crystalline order, while thermoplastic concerns the material's ability to soften for reshaping. A glass transition is therefore a change in physical response, rather than necessarily a chemical cleavage of the polymer backbone.^[ref]

For an illuminating comparison, imagine testing the same polymer chemistry with two different chain-length distributions. The local ether and sulfone connections can remain the same while flow behavior and mechanical response differ. A useful measurement report must identify both the chemical family and the sample being tested; naming PESU alone does not specify every processing or mechanical property.