2.2.3. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC)

For the TGA, analyses were performed using TA Instruments TGA Q20 thermobalance under nitrogen atmosphere (flow rate of 40 mL∙min⁻¹). The samples with a mass of ca. 6 mg were heated from room temperature to 800 °C at the heating rate of 20 K∙min⁻¹.

For the DSC, measurements were performed using TA Instruments DSC Q20 calorimeter. A solid polymer sample with a mass of ca. 8 mg was heated in an aluminum pan from −20 °C to 180 °C at the rate of 20 K∙min⁻¹. The glass transition temperature (T_g) was determined to be the temperature that corresponded to half of the complete change in heat capacity in the second cooling cycle of the DSC scan. Measurements of thermal isomerization were carried out in an aluminum pan. First, a polymer sample was dissolved in dichloromethane and irradiated by an LED UV lamp (365 nm) until no further changes were observed in the UV–VIS absorption spectrum. Afterwards, the solvent was removed using a vacuum rotary evaporator at room temperature in the dark. The value of enthalpy of thermal isomerization was determined in the first heating cycle of the DSC scan. All the DSC measurements were performed under a nitrogen atmosphere (flow rate of 40 mL∙min⁻¹).