A process for the manufacture of a fiber or foil comprising at least one optionally functionalized polymer with a high Tg selected from the group consisting of poly(aryl ether sulfone) (PAES), poly(aryl ether ketone) (PAEK) and aromatic polyimide, comprising the steps of (aa) providing a solution comprising at least 45 wt. % of the polymer, and at least 20 wt. %, of at least one halogen-free organic solvent (S1) for the polymer, both wt % based upon the weight of the solution; (bb) pushing the solution through a nozzle; and (cc) introducing the solution into a coagulation bath comprising: (cc1) at least one liquid (L1) in which the polymer is insoluble, and optionally (cc2) at least one organic solvent (S2) for the polymer, identical to or different from the organic solvent (S1), to form a fiber or foil. A fiber or foil obtained by this process as well as to fibers or foils with specific porosity features and/or mechanical properties.