Thermodynamic investigation of G2 and G4 siloxane dendrimers with trimethylsilyl terminal groups

In this work, we report results of the calorimetric study of the second (G2[OSi(CH3)(3)](12)) and fourth (G4[OSi(CH3)(3)](48)) generation siloxane dendrimers with trimethylsilyl terminal groups. The heat capacities of dendrimers were precisely measured in the temperature range T = (5520) K using a fully automated adiabatic calorimeter and a heat-flux differential scanning calorimeter. In the above temperature interval, the physical transformations of the studied compounds were detected, and its thermodynamic characteristics were determined. The fundamental thermodynamic functions (the enthalpy [H degrees(T) - H degrees(0)], the entropy [S degrees(T) - S degrees(0)], the Gibbs energy [G degrees(T) - H degrees(0)]) of dendrimers were calculated over the range from T -> 0 to 520 K using the experimentally determined heat capacities of the investigated compounds. The standard entropies of formation of dendrimers G2[OSi(CH3)(3)](12) and G4[OSi(CH3)(3)](48) were evaluated at T = 298.15 K. The obtained thermodynamic data of the investigated dendrimers were compared with those of the studied earlier siloxane dendrimers G1[OSi(CH3)(3)](6) and G3[OSi(CH3)(3)](24), which represent the structurally related homologous series of organosilicon dendrimers. As a result, the dependences between thermodynamic properties of the studied siloxane dendrimers and their molecular mass were established. (C) 2020 Elsevier Ltd.

Automated summary

In this study, the calorimetric properties of second and fourth generation siloxane dendrimers with trimethylsilyl terminal groups were measured and analyzed. The thermodynamic characteristics and fundamental functions of the dendrimers were calculated, showing a correlation between thermodynamic properties and molecular mass. The results provide valuable insights into the thermodynamic behavior of siloxane dendrimers.