The hybrids 2-hydroxyethyl methacrylate - chlorometylstyrene - modified montmorillonite were synthesized by means of "in-situ" radical (co) polymerization. The composites were analysed by thermal analysis (DSC-TGA-MS), Fourier-Transform Infrared Spectroscopy (FT-IR), nuclear magnetic resonance ((1)H-NMR), X-ray diffraction, and scanning electron microscopy (SEM). The influence of the polymerization conditions and compositions on the thermal stability and morphology of the obtained composites is discussed.