Gas Separation Membranes

1 - 25 . (canceled)

26 . A gas separation membrane comprising the following layers:

(i) a support layer;

(ii) a layer comprising a crosslinked polysiloxane;

(iii) a discriminating layer formed by plasma treatment of layer (ii) comprising groups of the Formula (1):

M-(O—) x    Formula (1)

wherein:

M is a metal or metalloid atom;

O is an oxygen atom; and

x has a value of at least 4;

(iv) optionally a layer which comprises a fluorinated polymer; and

(v) optionally a protective layer;

wherein:

(a) layer (ii) has an atomic ratio of carbon to silicon of 1.6 to 1.98;

(b) the discriminating layer comprises a surface comprising at least 10 atomic % of M of Formula (1) groups, wherein M is as hereinbefore defined; and

(c) layer (ii) is located between layers (i) and (iii).

27 . The gas separation membrane according to claim 26 wherein layer (ii) is formed by cross-linking a composition comprising a resin comprising

—O—Si≡CH and —O—Si(CH 3 ) 2 CH═CH 2 groups

28 . The gas separation membrane according to claim 26 wherein layer (ii) comprises groups of the formula:

29 . The gas separation membrane according to claim 26 wherein layer (iv) is present and is located on the opposite sides of layer (iii) to layer (ii).

30 . The gas separation membrane according to claim 26 wherein layer (v) is present and is the furthest layer from layer (i).

31 . The gas separation membrane according to claim 26 wherein layer (ii) further comprises one or more compounds of Formula (2):

M-(O—) z    Formula (2)

wherein:

M is a metal or metalloid atom;

O is an oxygen atom; and

z has a value of 1, 2 or 3.

32 . The gas separation membrane according to claim 26 wherein each M independently is silicon, titanium, zirconium or aluminium.

33 . The gas separation membrane according to claim 26 wherein M is silicon and the discriminating layer comprises a surface comprising 10 to 30 atomic % of M of Formula (1) groups.

34 . The gas separation membrane according to claim 26 wherein layer (iv) is present and has an average thickness of between 50 and 500 nm.

35 . The gas separation membrane according to claim 26 wherein the fluorinated polymer comprises an amorphous perfluorinated polymer.

36 . The gas separation membrane according to claim 26 wherein layer (iii) has been formed by a process comprising use of atmospheric glow discharge plasma.

37 . The gas separation membrane according to claim 26 wherein the plasma treatment of layer (ii) is done in the range of 0.30 to 9.00 J/cm2.

38 . The gas separation membrane according to claim 26 wherein layer (v) is present and comprises a polysiloxane.

39 . A gas separation module comprising a gas separation membrane according to claim 26 .

40 . A method of using of a gas separation membrane according to claim 26 for separating gases and/or for purifying a feed gas.

41 . A process for forming a gas separation membrane according to claim 26 .