In situ synthesis of poly(methyl methacrylate) (PMMA) nanocomposites by photopolymerization using organophilic, montmorillonite (MMT) as the layered clay is reported. MMT clay was ion exchanged with N-phenacyl, N,N-dimethylanilinium hexafluoro phosphate (PDA) which acts as both suitable intercalant- and photo-initiator. These modified clays were then dispersed in methyl methacrylate (MMA) monomer in different loading degrees to carry out the in situ photopolymerization. Intercalation ability of the photoinitiator and exfoliated nanocomposite structure were evidenced by both X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied.