The present invention relates to a poly(arylene sulfide) (PAS) copolymer (P) comprising: at least one block of poly(arylene sulfide) (PAS) having a weight- average molecular weight (Mw) of at least 40,000 g/mol as determined by gel permeation chromatography, and at least one block of polyorganosiloxane (POS) having a weight-average molecular weight (Mw) of at most 5,000 g/mol as determined by gel permeation chromatography, wherein the weight ratio of PAS:POS is from 95:5 to 99.5:0.5.