Development of novel phase change materials with classical and supramolecular approaches

Abstract

The demand for high-performance materials in solar energy and thermal energy storage applications has spurred significant research into phase change materials (PCMs) that can efficiently absorb and release energy. This study focuses on developing PCMs to be incorporated into polyurethane foam for thermal insulation, utilizing both traditional and supramolecular approaches to minimize energy loss. Initially, butyl stearate, a fatty acid ester, was selected as a conventional organic PCM for thermal energy storage. It was microencapsulated within a poly(urethane-urea) (PUU) shell using an in situ polymerization technique. This innovative method involves reacting a multifunctional amino alcohol with isocyanate, creating both urea and urethane groups within the same polymer chain. The resulting PUU microcapsules demonstrated enhanced mechanical properties and durability. The study found that the thermal properties of PUU microcapsules were significantly affected by the surfactant/PCM ratio and the type of surfactant used. Differential scanning calorimetry (DSC) analyses indicated variations in encapsulation efficiency and thermal behavior based on these factors. Microcapsules prepared with cationic surfactants showed superior phase change properties, exhibiting higher thermal stability, distinct thermal profiles and very high encapsulation efficiency up to 60%. Thermogravimetric analysis (TGA) confirmed that surfactant selection directly influenced the thermal degradation temperatures of the microcapsules. Incorporating microencapsulated PCMs into rigid polyurethane foam demonstrated the potential to create composites with substantial latent heat storage capacity. Treating PCM microcapsules as a third polyol in the formulation addressed challenges in foam formation quality, improving integration and performance. FTIR analysis confirmed the successful inclusion of PCM into the foam matrix, while DSC measurements verified the enhanced thermal storage capacity of the composites. Higher PCM concentrations increased thermal conductivity at specific temperatures, indicating the potential of these composites for thermal management applications. Moreover, lipid-derived cetyltrimethylammonium (CTA) salts were synthesized firstly as a novel group of organic PCMs for thermal energy storage applications. These salts were complexed with a calix[4]pyrrole core through ion pair recognition to explore the thermal behavior of a supramolecule with strong ionic interactions. Chemical and thermal characterization studies evaluated the performance of these materials as PCMs. The results showed that lipid-derived CTA salts complexed with calix[4]pyrrole exhibited trends similar to starting salts but with lower latent heat and onset temperatures, demonstrating unique characteristics. Despite these differences, they showed promising potential for PCM applications due to their enhanced stability and interaction properties. This study underscores the importance of innovative synthesis methods, careful material selection, and thorough characterization in developing advanced thermal energy storage materials. The findings of this study highlight the potential of PUU microcapsules and rigid polyurethane composites with microencapsulated PCMs for applications requiring robust, flexible, and efficient thermal management solutions. Besides with the help of supramolecular approach both lipid-derived CTA salts of this work display promising contributions to renewable PCMs for moderately high temperature solar and different thermal energy storage applications and their complexes with calix[4]pyrrole show promising potential for PCM applications due to their improved stability and interaction properties, making them valuable candidates for thermal management solutions.