Organopolysiloxane cluster polymer for rapid air cure

A composition comprising a cluster organopolysiloxane having the following average chemical structure:

• X3SiO—SiR2—R′—(R2SiO)x—R2Si—[Rb—(R2SiO)y—R2Si—Rb′—(R2SiO)z—R2Si]m—R′—R2SiO—SiX3
• where:
• (a) X=—OSiR2—R′—R2SiO—R2Si—R″-A;
• (b) R is independently in each occurrence selected from a group consisting of alkyl groups having from 2 to 6 carbons and aryl groups;
• (c) R′, R″, Rb and Rb′ are independently in each occurrence selected from divalent hydrocarbon groups comprising a chain of 2 to 6 methylene units;
• (d) A is independently in each occurrence selected from a group consisting of acrylate, methacrylate and trialkoxysilyl groups;
• provided that, on average, 60 to 90 mole-percent of the A groups are selected from acrylate and methacrylate groups;
• (e) Subscript m has an average value in a range of zero to 10;
• (f) Subscripts x, y and z each independently in each occurrence has an average value in a range of zero to 1200;
• and
• provided that the average values of m, x, y and z are such that the sum of the average values for x, y and z is in a range of 300-1200 and the molar ratio of methylene units to siloxane units is less than 0.15.