Amine substitution of hexachlorocyclotriphosphazene with poly(oxyethylene-oxypropylene)-monoamines afforded aminophosphazenes (AP) at molecular level with the structure of rigid phosphazene core and flexible alkoxy shell. Sodium montmorillonite were modified by using HCl-treated AP to prepare AP-exfoliated MMT clay (AP/EMMT) nanohybrids. When blending the nanohybrid into PU, the presence of silicate platelets promoted the PU stability and retarded the degradation for more than 60 degrees C under the standard TGA measurement. The co-existence of AP and EMMT at various weight ratios demonstrated a synergistic effect on the improvements of thermal stability as well as the UV resistance under the standard test of UV exposure in wavelength range of 365-400 nm. The molecular-level dispersion of AP and silicate platelets had synergistically contributed to the PU thermal and UV stability. (C) 2012 Elsevier Ltd. All rights reserved.