Herein we report a robust, highly selective, and efficient method to prepare dense poly(ethylene glycol) (PEG) polymer brushes on silicon substrates via solvent-free, catalyst-free, strain-promoted acetylene azide cycloaddition (SPAAC) reaction. First, poly(glycidyl methacrylate) was grafted to the silicon substrate as an anchoring layer to immobilize cyclopropenone-caged dibenzo-cyclooctyne-amine (photo-DIBO-amine) via an epoxy ring-opening reaction providing protected, stable, and functionalized substrates. Next, three synthesized alpha-methoxy-omega-azido-PEGs of different molecular weights (5, 10, and 20 kg/mol) were successfully grafted to the photo-DIBO-modified silicon substrates from melt after the deprotection of DIBO with LW-irradiation. PEG molecular weight, reaction temperature, and reaction time were all used to control the grafting reaction for targeted brush thicknesses and grafting densities. The highest grafting density obtained was close to 1.2 chains/nm(2) and was achieved for 5 kg/mol PEG. The prepared PEG polymer brushes displayed efficient antifouling properties and stability in PBS buffer aqueous media for a period of at least two months.