Structure of hybrid polymer by numerical simulation: example of   $(Si(CH_3)_2)_n(OSiO)_p(OH)_q$
  The structure depends on the mechanism of hydrolyse and polycondensation in the case sol-gel process used to obtain hybrid polymers containing uniquely covalent bonds. We computed by a tight binding calculation taking into account hybridization, the total electronic energy of different structures (amorphous, fractal and linear) of $(Si-(CH_3)_2)_n-(OSiO)_p(OH)_q$. We found that the total electronic energy of the amorphous structure was the smallest as a function of the number of atoms contained by the structure. As the total electronic energy is linked to the toughness of the structure, we may say that the structure of such hybrid polymer has the highest toughness for the amorphous structure. 
N.Olivi-Tran, S.Calas, P.Etienne