The thermal degradation of monolayers of alkylsilicon hydrides (RSiH3), alkylphosphonic acids (RP(O)(OH)(2)), and alkyldimethylchlorosilanes (R(CH3)(2)SiCl) Supported on silica, alumina, titania, zirconia. and calcium hydroxyapatite particles was investigated using thermal gravimetric analysis (TGA). The common feature in the TGA was a dramatic weight loss between similar to 200 and similar to 600 degrees C (N-2 atmosphere). which was not present for bare minerals. and, thus, was assigned to the degradation of the surface (crafted organic species. The onset of weight loss and the temperature of maximal weight loss rate (T-MAX) showed no dependence on the mineral and were determined by the nature of the chemical group directly attached to the Surface. The T-MAX values were similar to 400-450 degrees C (monolayers of RSiH3 and RP(O)(OH)(2)) and similar to 250 degrees C (monolayers of RSi(CH3)(2)Cl). The activation energies (E-A) of the degradation processes were determined using TGA at Multiple heating rates. Surprisingly. the substrate material did not show a significant effect oil E-A. For example, all the monolayers of octadecyl groups (R = C18H37) supported on silica. alumina. titania. and zirconia showed closed E-A values similar to 265 +/- 15 kJ/mol. The weight loss, IR, MS. and chemical analysis data Suggested that monolayer degradation occurred through pyrolysis of the hydrocarbon moieties (R groups) via cleavage of the C-C and Si-C (monolayers of silanes) or C-C and P-C bonds (monolayers of phosplionic acids). The inorganic portion of the molecule remained attached to the Surface of the mineral (presumably as silicates or phosphates). (c) 2004 Elsevier Inc. All rights reserved.