A polysiloxane comprising: (a) from 40 to 90 mole % units of formula R1R2SiO2/2, (b) from 10 to 60 mole % units of formula R3SiO3/2, and (c) from 0 to 5 mole % units of formula R1R4SiO2/2; wherein R1 and R2 independently are phenyl or C1-C6 alkyl; R3 represents at least one C1-C30 hydrocarbyl group; R4 is —Ar1-X—Ar2, where Ar1 and Ar2 independently are C6-C12 aryl and X is O CH2; provided that the polysiloxane comprises at least one —Ar1-X—Ar2 group.