We describe on the basis of the scaling concept the mechanical properties of a composite consisting of rigid particles and macromolecules of differing length, some members of which are sorbed on the surface of the particles. Upon change of the deformation and the temperature there takes place sorption or desorption of the members of the macromolecules from the surface of the particles. Thus, the particles are labile polynodes of the polymer network. The sorption and desorption processes are controlled by the molecular and structural parameters of the composite such as the depth and width of the surface potential wells of the particles and the dimension and concentration of the particles, including the size distribution of the macromolecules. We obtain the analytic dependence of the mechanical properties of the composite on the structural and molecular parameters, the type of deformation, the temperature, and also on the molecular mass distribution (MMD) characteristics. We indicate the MMD characteristics that can be obtained from the mechanical tests at various temperatures and the technique of their determination.