(FR2748485-A1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (EP897407-A1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (EP897407-B1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (JP2000510511-W)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (US6245881-B1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (US2001019787-A1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.    (US2001020082-A1)      Sulphonated polyimides with recurring groups of formula (In) and recurring groups of formula (Im) are new (where, C1, C2 = tetravalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, C1 and C2 each forming rings of 5 or 6 atoms with neighbouring imide groups; Ar1, Ar2 = divalent group containing at least one 6-10C optionally substituted aromatic ring, and/or 5-10C optionally substituted heterocyclic, based on aromatic ring, containing one or more heteroatoms selected from S, N and O, at least one of rings of Ar2 also being substituted by sulphonic acid group). Also claimed are membrane containing polyimide and fuel cell containing the membrane.    USE -   In preparation of low-cost ion-exchange membranes used in manufacture of fuel cells (claimed) to replace fossil fuels.    ADVANTAGE -   Polyimides produce membranes which have good mechanical, chemical and electrical properties; particularly good thermal stability, resistance to hydrolysis by acids, thermal stability at high temperatures for long periods of time, and resistance to oxidation and reduction.