Calorimetric study of chitosan-graft-poly(2-ethylhexyl acrylate) copolymer

Highlights: • The heat capacity of chitosan-graft-poly(2-ethylhexyl acrylate) copolymer was measured. • Thermodynamic characteristics of the revealed physical transformation were analyzed. • The standard thermodynamic functions of copolymer were calculated. In the present work, the temperature dependence of the molar heat capacity of chitosan-graft-poly(2-ethylhexyl acrylate) copolymer was measured for the first time in the temperature range from 6 to 350 K by precise adiabatic calorimetry, and the thermophysical properties of copolymer were studied over the range from 270 to 570 K by differential scanning calorimetry. In the above temperature intervals, the glass transition was detected for the investigated compound, and the standard thermodynamic characteristics were determined and analyzed. The standard thermodynamic functions: heat capacity $C_{\text{p}}^{\text{o}}\left(T\right)$, enthalpy [H°(T)−H°(0)], entropy [S°(T)−S°(0)], and the Gibbs energy [G°(T)−H°(0)] for the range from T → 0 to 350 K, as well as the standard entropy of formation Δ_fS° and the Gibbs energy of formation Δ_fG° of copolymer at T = 298.15 K in the glassy state were calculated based on the obtained experimental data. The standard thermodynamic properties of the investigated copolymer were discussed and compared with the literature data for the studied earlier copolymers of chitosan.