Calorimetric study of carbosilane dendrimers of the third and sixth generations with phenylethyl terminal groups

Abstract

In the present work, temperature dependences of heat capacities of carbosilane dendrimers of the third and sixth generations with phenylethyl terminal groups, denoted as G3[CH2CH2C6H5]32 and G6[CH2CH2C6H5]256, were measured for the first time in the temperature range from 6 to 520 K by precision adiabatic calorimetry and differential scanning calorimetry. In the above temperature range, physical transformations, such as the low-temperature anomaly (for dendrimer G3[CH2CH2C6H5]32), the glass transition (for both dendrimers), and the high-temperature relaxation transition (for dendrimer G6[CH2CH2C6H5]256), were detected, and the standard thermodynamic characteristics of the revealed transformations were determined and analyzed. The standard thermodynamic functions, heat capacity \( C_{\text{p}}^{\text{o}} (T) \), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0), and Gibbs energy G°(T) − H°(0) for the range from T → 0 to 520 K, and the standard entropies of formation \( \Delta S_{\text{f}}^{\text{o}} \) of the investigated dendrimers in the devitrified state at T = 298.15 K were calculated per mole of the notional structural unit. The standard thermodynamic properties of dendrimers under study were discussed and compared with the literature data for carbosilane dendrimers with different functional terminal groups.