Integral composite membrane with a continuous ionomer phase

A method of forming the composite membrane, the method comprising:

• (a) providing a support layer,
• (b) applying an ion exchange material to the support layer in one step,
• (c) obtaining a microporous polymer structure comprising at least one microporous polymer layer;
• (d) laminating the at least one microporous polymer layer to the ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase,
• (e) applying an ion exchange material on a top surface of the impregnated microporous polymer structure according to method step (d),
• (f) drying the impregnated microporous polymer structure to form the composite membrane having a continuous ionomer phase, and
• (g) annealing thermally the composite membrane, to provide a composite membrane comprising:
• a microporous polymer structure;
• and
• an ion exchange material at least partially embedded within the microporous polymer structure and rendering at least a portion of the microporous polymer structure occlusive,
• wherein the ion exchange material forms a continuous ionomer phase within the composite membrane,
• wherein the composite membrane includes multiple layers of the ion exchange material provided on top of one another which do not have any internal interface between the layers, and
• wherein the composite membrane has a haze which is the ratio of diffuse transmittance to total transmittance of light through the composite membrane and the composite membrane exhibits a change of the haze of 0% or less after being subjected to a blister test procedure.