## 3 Results and Discussion  
By esterification of dicarboxylic acids with alkoxylated alcohols according to the method described earlier, the following were obtained: dibutoxyethyl adipate (DBEA), diphenyloxyethyl adipate (DPEA) and dibutoxypropyl adipate (DBPA) [29] (Table 1). The yield of diesters was 86.9% or more. The duration of synthesis is significantly influenced by the presence of a benzene ring in the structure of phenoxyethanol, which is associated with steric difficulties during reaction. As a result, the synthesis time of phenoxyester increased. The synthesis time of dibutoxypropyl adipate slightly exceeded the synthesis time of dibutoxyethyl adipate, which was probably also due to the branched structure of the alcohol used--1-butoxypropane-2-ol. The characteristics of the esters obtained are given in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ester** & & **Structural Formula** \\ \hline Dibutoxyethyl adipate (DBEA) & & & \\ Diphenoxyethyl adipate (DPEA) & & & \\ Diphenoxyethyl adipate (DPEA) & & & \\ Dibutoxypropyl adipate (DBPA) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The structure of alkoxylated adipates. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Indictors** & **DBEA** & **DPEA** & **DBPA** \\ \hline Acid number, mg KOH/g & 0.15 & 0.2 & 0.16 \\ Ester number, mg KOH/g & 321 & 289 & 298 \\ Molecular weight, calculated & 346 & 386 & 374 \\ Mass fraction of volatile substances, \%, & 0.7 & 0.5 & 0.6 \\ no more & & & \\ Yield, \% & 87.5 & 86.9 & 87.0 \\ Reaction time, min & 150 & 180 & 165 \\ Maximum reaction temperature, \({}^{\circ}\)C & 130 & 150 & 138 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The main characteristics of dicarboxylates. The obtained adipic acid diesters were characterized by low acid number values and mass fractions of volatile substances, which are critically important indicators in the production of PVC-based materials and are also associated with ensuring the necessary level of characteristics and service life of finished products. The resulting dibutoxic derivatives of acids are oily yellowish liquids; diphenoxy ester is a highly viscous paste-like substance with a low melting point. The structure of the obtained diesters was confirmed by IR spectra (Figure 1). The spectra lack characteristic absorption bands of the valence vibrations of the carbonyl group in the aliphatic carboxylic acids in the range of 1685-1687 cm\({}^{-1}\), as well as in the range of 1740-1650 cm\({}^{-1}\), indicating the C=O groups in carboxylic acids. Characteristic absorption patterns can be observed in infrared spectroscopy of esters, which help to determine their structural features. One of the key features is the absorption in the region of 1737 cm\({}^{-1}\), corresponding to the valence vibrations of the carbonyl group (C=O). An absorption of 1173 cm\({}^{-1}\) is also highlighted, this being associated with fluctuations in the C-O-C ester group. Additionally, two intense peaks at 1330 cm\({}^{-1}\) and 1050 cm\({}^{-1}\) can be noted, which reflect asymmetric fluctuations in carbon bonds of CO. If an aromatic fragment is present in the ester structure, this is confirmed by the absorption for the C=C double bond at the level of 1625 cm\({}^{-1}\) and the C-H group in the range of 1250 cm\({}^{-1}\). These spectral characteristics allow for a deeper understanding of the chemical nature and structure of esters. The esters obtained were investigated for possible use as PVC plasticizers. Currently, there is no single point of view on the mechanism of polymer plasticization due to the significant influence of various physico-chemical and technological factors on this process: the composition and structure of macromolecules and supramolecular structures; the composition and molecular weight of the polymer; the method of its preparation; the nature, molecular weight and structure of plasticizers; the method and mode of combining components; the nature of their interaction; etc.