## 5 Conclusions and Outlook  
To summarize, in this study pentyl esters (from 1-pentanol, C\({}_{5}\)) of myristic C\({}_{14}\), palmitic C\({}_{16}\), stearic C\({}_{18}\), arachidic C\({}_{20}\) and behenic C\({}_{22}\) acid, alongside methyl and decyl arachidate (from methanol C\({}_{1}\) and 1-decanol C\({}_{10}\) with arachidic C\({}_{20}\) acid), were successfully synthesized through Fischer esterification in acidic catalytic conditions with purities over 95% and their properties analyzed. In order to prove the efficacy of the synthesis procedure and to confirm the formation of the desired compounds, the esters' chemical structures were identified through ATR-IR, GC-MS and NMR. Afterwards, the thermal properties were retrieved through DSC and TGA analysis. Methyl and decyl arachidate were found to have enthalpies of fusion above 200 J/g, while the pentyl esters showed lower values but still above 150 J/g. All esters presented good short-term stability with deviations in the phase change transition temperatures lower than 5%. Despite the tendency of DSC analysis to enhance the degree of supercooling perceived, the supercooling measured in the samples never exceeded 8 \({}^{\circ}\)C. Overall, the phase change temperatures of the esters measured were in the range between 10 and 48 \({}^{\circ}\)C. Upon comparison with the esters produced previously by [PERSON] et al. [14], some trends correlating the chemical structures of the esters to the melting temperatures could be deduced. In particular, the aliphatic chain length of the carboxylic acid was found to have a higher impact on the increase of the melting temperature than the alcohol aliphatic chain. This is due to the rotational freedom of the ester bond, which, if shifted from the position at the end of the chain to the middle, creates stronger vibrations in the crystalline structure able to disrupt the lattice. In addition, an \"odd-even\" effect was discovered, with pentyl esters having constantly lower melting points in comparison to decyl esters. This is due to the fact that in even-numbered structures the bonds to the ester group are symmetrical, while in odd structures they are thought to be angled at 112\({}^{\circ}\). Such an effect is only visible for CH\({}_{2}\) chains longer than two carbon atoms, and as such is not manifesting in methyl esters, which show the highest melting points of the whole series. The existence of trends correlating directly the chemical structure to the thermal properties is of significant importance since it could allow the development of predicting tools capable of calculating the chemical structure needed to achieve certain phase change temperatures for specific applications. As a result of the promising results obtained, fatty esters appear to be interesting candidates as bio-based PCM for latent heat storage applications. However, pentyl esters might face bigger challenges compared to methyl and decyl esters regarding their implementation in real case applications due to lower enthalpies of fusion. Generally, given the temperature range retrieved, all esters presented could prove to be an interesting alternative to inorganic PCM or paraffins for low-mid temperatures application. One example constitutes the use of PCM embedded in textiles to create \"smart\" sportswear to reduce sweat production and thus hot and cold peaks in the human body. Such application usually requires PCM with phase change transitions between 28 and 33 \({}^{\circ}\)C. Another possible field is represented by space cooling and heating applications, which necessitate of materials with phase change transitions generally below 23 \({}^{\circ}\)C for space cooling and above 25 \({}^{\circ}\)C for space heating. PCM with higher phase transition, such as 40 to 50 \({}^{\circ}\)C can be used for cooling of electronic devices and machining tools [27; 28]. According to the European Commission [4], water heating accounts for 79% of total final household energy use, while cooling shares a lower but increasing percentage due to recent climate change.