A series of poly(vinylphenol-co-vinylpyrrolidone-co-isobutylstyryl polyhedral-oligosilsesquioxane (PVPh-co-PVP-co-POSS) copolymers were prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with POSS (PAS-co-PVP-co-POSS) following by selective removal of the acetyl protective group, and results in significant glass transition temperature increase. The thermal properties and hydrogen bonding of these copolymers were investigated by differential scanning calorimetry and fourier transfer infrared spectroscopy and good correlation between thermal behaviors and infrared spectroscopy results were observed.