Disclosed are photoinitiators that are ultra violet (UV) reactive. The photoinitiators can be polymerized into polymeric backbones for use in UV curable hot melt pressure sensitive adhesives. The preferred polymeric backbones are acrylic-based polymers. The photoinitiators are very UVC sensitive and have excellent hot melt viscosity stability that is many fold higher than existing photoinitiators. The subject photoinitiators feature aryl ketones linked through an ether linkage to a variety of connector sequences that allow for polymerization of the photoinitiators.