The present invention relates to macroinitiators comprising at least one hydrophobic segments in a molecule, wherein a molecular weight of the hydrophobic segment is 300 to 1800. The present invention further relates to block copolymers, wetting agent and polymeric materials having the block copolymers of the present invention associated with, which is suitable for medical devices, particularly for ophthalmic devices, including contact lenses, ophthalmic lenses, punctal plugs and artificial corneas.