In the present work by precision adiabatic vacuum and dynamic scanning calorimetry the heat capacity of covalent-bonded fullerenes C-60 and C-70 containing derivatives of atactic poly(methyl methacrylate) has been measured over the range from 6 to 350 K and from 330 to 460 K, respectively. Low-temperature heat capacity has been analyzed on the basis of Debye and Tarasov theories of the heat capacity of solids and the multifractal generalization and, as a result, some conclusions on the heterodynamics of their structures have been drawn. Temperature interval and thermodynamic characteristics of devitrification as well as their thermal stability regions have been determined. The experimental data were used to calculate standard thermodynamic functions, namely, the heat capacity C(p)degrees(T), enthalpy H degrees (T) - H degrees(0), entropy S degrees(T) and Gibbs function G degrees(T) - H degrees(0), for the range from T -> 0 to 430 K. The thermodynamic characteristics of fullerene-containing derivatives of atactic poly(methyl methacrylate) and a polymer-analog not including C-60 and C-70 have been compared. (c) 2005 Elsevier B.V. All rights reserved.