The physicochemical and mechanical properties of amine-terminated covalently bound poly(ethylene glycol) (PEG) layers are dependent on fabrication methods. In particular, the use of a Theta solvent yields dense polymer layers with properties not well described by traditional models. Light diffraction techniques were used in an attempt to understand the influence of polymer aggregation kinetics in a Theta solvent on the final properties of the fabricated PEG layers. The polymer layer properties were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) in force mode, quartz crystal microbalance (QCM), and fluorescence microscopy. Results show that polymer concentration in solution is an important indicator of final layer properties and that the use of a Theta solvent induces complex aggregation phenomena in solution yielding layers with widely different properties. The PEG layers fabricated through the process described in this article are also shown to present chemically available primary amine groups, paving the way for the immobilization of bioactive molecules.