Calorimetric and infrared studies of carbosilane dendrimers of the third generation with ethyleneoxide terminal groups

Abstract

In the present work, temperature dependences of heat capacities of carbosilane dendrimers of the third generation with ethyleneoxide terminal groups, denoted as G3[(OCH2CH2)1OCH3]32 and G3[(OCH2CH2)3OCH3]32, have been measured in the temperature ranges from T=6 to 520K by precision adiabatic calorimetry (AC) and differential scanning calorimetry (DSC). In the above temperature range the physical transformations, such as glass transition and anomalies, have been detected, and their standard thermodynamic characteristics have been determined and analyzed. Complementary temperature-dependent infrared (IR) studies of carbosilane dendrimer G3[(OCH2CH2)1OCH3]32 have been performed in the range from T=4 to 298K in order to study the nature of the revealed transformations. The standard thermodynamic functions of dendrimers under study, namely, heat capacity Cp0(T), enthalpy H°(T)−H°(0), entropy S°(T)−S°(0), and Gibbs energy G°(T)−H°(0) have been calculated for the range from T→0 to 520K. The standard thermodynamic properties of the investigated dendrimers have been discussed and compared with literature data for carbosilane dendrimers with different functional terminal groups.