The present study was focused on permanent grafting of poly(ethylene glycol) (PEG) layers (brushes) from the melt to adsorbed reactive macromolecules. A poly(glycidyl methacrylate) (PGMA) was used to form the reactive primary adsorbed layer. It was found that a thin (1.5 nm) PGMA layer had a high grafting efficiency, and elevated temperatures considerably accelerated the grafting process. The grafting extent was eventually limited by concentration and accessibility of functional reactive groups in the primary adsorbed layer. Several distinct types of brush morphologies were observed depending on the grafted layer height. Isolated crystals were detected for brushes possessing lower grafting density. At higher levels of PEG attachment, the crystalline formations uniformly covered the entire surface of the substrate. The development of highly extended crystalline formations on the surface and marked expansion of the PEG brushes in water indicated that an extremely high grafting density was attained. The developed grafting protocol was utilized to modify various substrates with PEG grafted layers.