(WO9405404-A1)      A gas sepn. membrane comprises a miscible blend of at least 2 polymers comprising: (I) a first polymer selected from (a) polyimide materials contg. repeat units (I), (b) polyamide materials contg. repeat units (2), and (c) polyamide-imide materials contg. repeat units (3) or opt. comprising a mixt. of (a) and (b); Ar = 0-99% of any aromatic diamine moiety and 1-100% aromatic diamine moiety of formula (4) Ar' = gp.(5); X = direct bond or R'; R' = gp.(6) or (7), C(CF3)2, C(CH3)2, C(Z)2, SO2, Si(CH3)2, Si(Z)2, Si(Z)2-O-Si(Z)2 and/or CO; Z = H; 1-6C alkyl; 6-12C aromatic; or halogen such as F, Cl, Br or I; n = 0-4; R" = C(CF3)2, C(CH3)2, C(Z)2, SO2, Si(CH3)2, Si(Z)2, Si(Z)2-O-Si(Z)2, CO and/or gp.(8); R = gp. (9)-(12); R''' = C(CF3)2, C(CH3)2, C(Z)2, SO2 and/or CO; Ra = aromatic diacid moiety; Rb = aromatic moiety; and x,y,z = fractions and x+y+z = 1; and (II) a second polymer comprising a polyimide contg. repeat units (13): Ar" = gp.(14), Y = 1-6C alkyl; or 6-12C aromatic.    USE/ADVANTAGE -   The membranes cast from polymer blends have superior gas permeability and selectivity and are partic. useful in sepn. processes involving H2, N2, CH4, CO, CO2 He and O2.    (JP8501977-W)      A gas sepn. membrane comprises a miscible blend of at least 2 polymers comprising: (I) a first polymer selected from (a) polyimide materials contg. repeat units (I), (b) polyamide materials contg. repeat units -(NHArNHC(=O)RaC(=O))- (2), and (c) polyamide-imide materials contg. repeat units (3) or opt. comprising a mixt. of formula (a) and (b); Ar = 0-99% of any aromatic diamine moiety and 1-100% aromatic diamine moiety of formula (4); Ar' = gp.(5); X = direct bond or R'; R' = gp.(6) or (7), C(CF3)2, C(CH3)2, C(Z)2, SO2, Si(CH3)2, Si(Z)2, Si(Z)2-O-Si(Z)2 and/or CO; Z = H; 1-6C alkyl; 6-12C aromatic; or halogen such as F, Cl, Br or I; n = 0-4; R" = C(CF3)2, C(CH3)2, C(Z)2, SO2, Si(CH3)2, Si(Z)2, Si(Z)2-O-Si(Z)2, CO and/or gp.(8); R = gp. (9)-(12); R''' = C(CF3)2, C(CH3)2, C(Z)2, SO2 and/or CO; Ra = aromatic diacid moiety; Rb = aromatic moiety; and x,y,z = fractions and x+y+z = 1; and (II) a second polymer comprising a polyimide contg. repeat units (13): Ar" = gp.(14), Y = 1-6C alkyl; or 6-12C aromatic.    USE/ADVANTAGE -   The membranes cast from polymer blends have superior gas permeability and selectivity and are partic. useful in sepn. processes involving H2, N2, CH4, CO, CO2 He and O2.