In this study, encapsulation of montmorillonite (MMT) platelets into poly(methyl methacrylate) (PMMA) was successfully achieved via miniemulsion polymerization. First, N-allyl-N,N-dimethyloctadecan-1-aminium bromide (ADM₁₈), a polymerizable surfactant, was employed to modify MMT nanoplatelets via ion exchange to improve the compatibility with the matrix phase as well as form a covalent anchor with PMMA. Subsequently, MMT-ADM₁₈ was incorporated in methyl methacrylate, along with a surfactant, costabilizer, and initiator, to obtain stable nanocomposite latexes via miniemulsion polymerization. FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (Scanning electron microscopy), TEM (Transmission electron microscopy), and TGA (Thermogravimetric analysis) were utilized to validate structures and characterize thermal properties of neat PMMA and PMMA-based nanocomposites. FTIR indicated an interaction occurred between MMT's structural OH groups and PMMA's carbonyl moiety. XRD exhibited that the nanocomposites' morphology exfoliated. TEM images demonstrated stable nanocomposite latexes comprised of MMT core and PMMA shell with diameters ranging from 320 to 450 nm were formed. The TGA results showed a substantial improvement in nanocomposites' thermal stability, as evidenced by shifting the onset of the thermal degradation compared to that for pristine PMMA.