Patent ID: 7148263

Claim:
A composition which comprises a homogeneous mixture of a porogen, a solvent, a catalyst, and a pre-polymer combination comprising a first silicon containing pre-polymer having Formula (I) and a second silicon containing prepolymer having Formula (II): (R 2 ) (3−x) (OR 3 ) x Si—R 1 —Si(OR 4 ) y (R 5 ) (3−y) Formula (I) (R 6 ) (4−m) Si(OR 7 ) m (Formula II) wherein x and y are each integers having a value of 0, 1, 2, or 3; m is an integer have a value of 1, 2, or 3; R 1 is a polyvalent organic group selected from the group consisting of an alkyl group, an aryl group, a biphenyl group and an anthracenyl group; R 2 , R 5 and R 6 , are independently a monovalent or polyvalent organic group selected from the group consisting of an alkyl group, an aryl group, hydrogen a biphenyl group and an anthracenyl group; R 3 , R 4 and R 7 are independently a monovalent or polyvalent organic group selected from the group consisting of an alkyl group, an aryl group, hydrogen, a biphenyl group, an anthracenyl group and an acyl group; wherein the proportion of the first silicon containing pre-polymer to the total of the first silicon containing pre-polymer and the second silicon containing pre-polymer ranges from about 10 weight percent to about 90 weight percent, and which composition has a pH of less than 7.