Fabrication and assessment of <i>n</i> -eicosane/poly(stearylmethacrylate- <i>co</i> -butylacrylate) nanocapsules: impact of long alkyl polymer chains on thermal performance and stability

The objective of this study is to develop, characterise, and analyse thermal energy storage (TES) properties of <i>n</i>-eicosane/poly(stearylmethacrylate-<i>co</i>-butylacrylate) [ESE/P(SMA-<i>co</i>-BA)], a novel nanoencapsulated phase change material (NPCM). The NPCMs were produced <i>via</i> mini-emulsion polymerisation of a polymer shell, poly(stearylmethacrylate-<i>co</i>-butylacrylate) [P(SMA-<i>co</i>-BA)], around <i>n</i>-eicosane [ESE], which served as the core material. The thermal behaviour and thermal stability of ESE/P(SMA-<i>co</i>-BA) were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). According to DSC results, ESE/P(SMA-<i>co</i>-BA) has melting and crystallisation temperatures of 37.4 °C and 25.1 °C and latent heat values of 224.6 J g^-1 and 191.7 J g^-1, respectively. The ESE/P(SMA-<i>co</i>-BA) nanocapsules exhibited an effective encapsulation efficiency (87.2%), encapsulation ratio (93.6%), and excellent thermal storage capacity (93.1%). The TGA study revealed the exceptionally good thermal stability of ESE/P(SMA-<i>co</i>-BA), with degradation in two stages. The chemical structure and crystallinity of the prepared ESE/P(SMA-<i>co</i>-BA) were verified using Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) analysis. The results obtained from field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and polarized optical microscopy (POM) indicated that the synthesized ESE/P(SMA-<i>co</i>-BA) had a spherical morphology with a mean particle diameter of 195.3 nm, as determined by particle size distribution (PSD) analysis. This research highlighted a novel technique for fabricating phase transition materials for TES, which can be used in a variety of applications, including food storage containers, smart textiles, and building, medical and electronic materials.