## 3 Results and Discussion
For example, dibutoxpropyl adipate exhibits better compatibility with PVC than other studied esters due to its branched ester structure, which enhances solubility and lowers dissolution temperatures within the polymer matrix. A decrease in these characteristics is observed in ether containing aromatic rings in the structure of alcohol. The minimum values of important technological characteristics correspond to an ester based on aliphatic alcohol of normal structure. Polar phenoxy derivative molecules featuring two benzene fragments hinder the segmental mobility of polymer macromolecules, particularly at lower temperatures. As a result, polyvinyl chloride (PVC) containing DPEA exhibits the highest glass transition temperature, reaching 7.4 \({}^{\circ}\)C, indicating that the polymer transitions to a glassy state at this temperature. With an increase in the length of the alkyl chain between the ester fragments, the glass transition temperature passes into the region of negative temperatures. The butoxy derivative of the linear structure reduces the glass transition temperature of PVC plastic to a temperature of minus 29.4 \({}^{\circ}\)C. This value is slightly lower than that achieved by industrial di(2-ethylhexyl) phthalate (DOP), but it remains comparable to the effectiveness of dioctyl adipate (DOA). It is noteworthy that the introduction of branched alcohols into the ether structure further reduces \(T_{g}\), reaching a remarkable \(-\)37.6 \({}^{\circ}\)C for dibutoxpropyl adipate ester (DBPA). This modification enhances the segmental mobility, which significantly affects the temperature transitions of PVC plastic. Plasticizers are crucial for the creation of flexible polymer materials. Their effectiveness can be quantified by their effect on the hardness of PVC measured at a controlled temperature (23 \(\pm\) 2) \({}^{\circ}\)C. The key indicator in this assessment is the \"substitution coefficient\", which indicates the amount of plasticizer needed to match the hardness of PVC plastic achieved with DOP. The replacement coefficient can be calculated using a specific formula that takes these variables into account. Thus, structural modifications of plasticizers not only improve the thermal properties of PVC, but also play a significant role in determining its mechanical characteristics (5):  
\[\text{The substitution factor = Amount of plasticizer, wt. h./ Amount of DOP, wt. h.} \tag{5}\]  
To evaluate the effectiveness of the plasticizing properties of synthesized esters, a comprehensive study was conducted focusing on the relationship between plasticizer concentration and the hardness of PVC plasticate across a broad range of dosages. The primary objective was to determine the specific amount of plasticizer necessary for the PVC formulation to achieve a Shore A hardness of 70 conditional units. Additionally, substitution factors for various plasticizers in relation to dioctyl phthalate (DOP) were calculated (Table 6). \begin{table}
\begin{tabular}{c c} \hline
**Plasticizer** & **Substitution Factor** \\ \hline DBEA & 0.91 \\ DBPA & 1.02 \\ DPEA & 1.19 \\ \hline \end{tabular}
\end{table} 
Table 6: The effectiveness of the plasticizing effect of synthesized plasticizers. Based on the findings, it is evident that the structural characteristics of the esters significantly influence their plasticizing effectiveness. The data indicate that phenoxy esters demonstrate a lower plasticizing efficiency compared to their butoxy counterparts. This variation can be attributed to specific substitution factors that affect how these esters interact with polymers, ultimately impacting their mechanical properties and thermal stability. In summary:  
* Structural influence: The design and molecular structure of esters play a crucial role in determining their effectiveness as plasticizers. * Comparative effectiveness: Phenoxy esters are less efficient than butoxy esters, suggesting that the latter may be more suitable for applications requiring enhanced plasticization.