To obtain a polymer blend containing high-performance polymer(s) and sulfoxide group-bearing polymer(s), and to provide a method for producing the polymer blend.

This polymer blend is obtained by heat treatment at ≥150°C of a blend composed of 1-85 pts.wt. of at least one kind of high-performance polymer and 15-99 (pref. 40-90, esp. pref. 55-75) pts.wt. of sulfoxide group-bearing polymer(s). Another version of this polymer blend, a crosslinked or partially crosslinked product of this polymer blend, is obtained by heat treatment at ≥150°C of a blend composed of high-performance polymer(s), i.e., at least one kind of polymer selected from polyesters, partially fluorinated polymers, polyethersulfones, polysulfones, polyetherimides, polyamide-imides and polyacetals, and at least one kind of sulfoxide group-bearing polymer. The latter polymer blend has been well known to have high heat and chemical resistance. The sulfoxide group-bearing polymer is a polyarylene sulfoxide, esp. polyphenylene sulfoxide. The polymer blends of the present invention are used for producing fibers, films or other formed products.