Nanocomposite materials based on poly(butyl methacrylate) and either graphene oxide (GO) or functionalized graphene oxide (F-GO) were produced using the in situ bulk radical polymerization technique. It was found that the Hummers method results in a higher degree of oxidation, compared to the Staudenmaier, whereas F-GO was produced using a silane-modifying agent. Polymerization kinetics were studied both experimentally and theoretically, and it was found that the presence of hydroxyl groups in the surface of GO results in scavenging the primary initiator radicals, thus reducing the initiator efficiency and the reaction rate, whereas the number-average molecular weight of the polymer formed was increased. The presence of F-GO affected the polymerization kinetics in a different way resulting in partially grafted structures. The theoretical study included the addition of a phenomenological transfer to the polymer side-reaction to account for the polymerization occurring at the F-GO surface.