Thermodynamic investigation of G2 and G4 siloxane dendrimers with trimethylsilyl terminal groups. (February 2021)

• Record Type: Journal Article
• Authors: Sologubov, Semen S.; Markin, Alexey V.; Sarmini, Yuliya A.; Smirnova, Natalia N.; Boldyrev, Konstantin L.; Tatarinova, Elena A.; Meshkov, Ivan B.; Muzafarov, Aziz M.
• Is Part Of: Journal of chemical thermodynamics. Volume 153(2021)
• Publication Date: 2021-02
• Subjects: Siloxane dendrimers -- Adiabatic calorimetry -- Differential scanning calorimetry (DSC) -- Heat capacity -- Glass transition -- Thermodynamic functions; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2020.106318
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Highlights: The molar heat capacities of G2 and G4 siloxane dendrimers. The low-temperature structural anomaly and the glass transition of dendrimers. The standard thermodynamic functions of G2 and G4 siloxane dendrimers. The "thermodynamic property vs. molecular mass" dependences for dendrimers. Abstract: 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 = (5–520) 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 °( T ) − H °(0)], the entropy [ S °( T ) − S °(0)], the Gibbs energy [ G °( T ) − H °(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.