Surface spin labeling in interface layers of filled polymers investigation

A new approach to the investigation of interface layers in filled polymers is suggested. The method is based on using stable nitroxide radicals (spin labels) grafted to mineral filler surface. Two types of spin labels bounded to the solid surface of filler particles (silica) by covalent and hydrogen bonds were used. It was shown that the rotation mobility of spin labels relates to the intensity of a molecular motion of adsorbed polymer chain, irrespective of the bond nature. Information on structure and molecular motion of interface layers in filled polymers could be obtained by analysing the dynamics of nitroxide radicals bound to the surface of silica particles by covalent and hydrogen bonds. The correlation is found between the glass transition temperature of polymer matrix and the change in mobility of chains contacting with the filler surface. The lower the T-g of the polymer, the greater the difference between mobilities of chains in inner layers of the matrix and interface layers. In polymer matrices with high T-g (PS, PVP), the interface layer mobility differs only slightly from molecular mobility of the unfilled polymer. The possibilities of surface spin labeling for filled polymer investigations is considered.