## 3 Results and Discussion
The transition to a state of high elasticity occurs at a glass transition temperature of 7.4 \({}^{\circ}\)C. For PVC plasticized with esters of aliphatic alcohols DBEA and DBPA, the glass transition temperatures are noticeably lower and amount to minus 29.4 \({}^{\circ}\)C and minus 37.6 \({}^{\circ}\)C, respectively. The obtained indicators exceed the same indicator for plastic with the industrial plasticizer DOP. Heating of the polymer material causes its softening and reduces the index of the dynamic modulus of elasticity, E\({}^{\prime}\). Such changes in mechanical properties due to temperature are associated with the thermal transition of the polymer from a glassy state to a highly elastic one. The structure of synthesized esters has a direct effect on the modulus of elasticity of plasticized PVC samples at the beginning of pharmaceutical tests: for dibutoxyethyl adipate, the modulus values are higher than for diphenylester and branched-structure ester. The order of the index for DPEA is commensurate with the elastic modulus of PVC plastics with a DOP content. The modulus value for DBPA is close to this indicator for DOA, which also has an alcohol group with a branched structure. The temperature ranges of the transition from the glassy state to the highly elastic state (Tf-Ts) for PVC compositions plasticized with DBPA and industrial DOA are quite close: 84.3 \({}^{\circ}\)C and 81.6 \({}^{\circ}\)C, respectively. The investigated ether even surpasses the industrial DOA in this indicator. For a composition containing DPEA, this transition interval is significantly inferior in magnitude to the esters of aliphatic alcohols and is 40.7 \({}^{\circ}\)C, which is slightly lower than for the industrial plasticizer DOP--52.6 \({}^{\circ}\)C. In general, the regularity of the influence of the alcohol structure on the elastic modulus is traced: in the case of the presence of an aromatic ring in the alcohol component in the structure of the diester, an increase in the elastic modulus is observed; in the case of a branched structure, there is a decrease in the elastic modulus. The highest value of this indicator corresponds to the aliphatic structure of the normal structure. The physical properties of polymers are significantly influenced by their chemical structure and the arrangement of polymer chains. A key factor in this is the glass transition temperature, \(T_{g}\), which can be altered through the incorporation of plasticizers during processing. This process, known as plasticization, results in a reduction in \(T_{g}\), allowing for enhanced flexibility and mobility within the polymer chains. Plasticizers achieve this by disrupting the secondary bonds that hold the polymer chains together, creating weaker bonds between the polymer and the plasticizer. Figure 6: DMA thermogram for PVC, plasticized DOP. From both practical and theoretical perspectives, introducing a plasticizer into a polymer matrix is crucial. Lowering the glass transition temperature expands the temperature range in which the polymer maintains a highly elastic state, improves frost resistance, and reduces viscosity in polymer melts. These changes facilitate processing, particularly for polymers whose \(T_{g}\) or flow temperatures are close to or exceed their decomposition temperatures. The effectiveness of a plasticizer is often evaluated by its ability to depress \(T_{g}\). The low-temperature characteristics of plasticizers are vital for applications like sealing plastics, where brittleness can lead to cracking in cold environments. The extent of \(T_{g}\) depression is influenced by the thermodynamic compatibility between the plasticizer and the polymer; greater compatibility allows for higher concentrations of plasticizer to be added, enhancing lubricity and facilitating new applications for polymer materials. Intermolecular interactions are determined by the volume and structure of the plasticizer molecule, in particular the size of the alkyl chain.