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Tuning thermal performance: the role of molecular asymmetry in di-n-alkyl adipates for efficient low-temperature thermal energy storage
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Advisor(s)
Abstract(s)
The development of efficient and sustainable thermal energy storage (TES) systems is crucial for improving energy efficiency in various applications, especially at low temperatures, such as cryogenic cooling, cold storage, logistics and transportation. Phase change materials (PCM) play a key role in TES, as they allow the storage and release of significant amounts of latent heat during phase transitions. In this context, our research group has been working on new materials, particularly binary systems, with potential application as PCM for efficient low-temperature TES1. As a result, di-n-alkyl adipates have recently emerged as promising candidates due to their favorable thermal properties, chemical stability, and phase change behavior2.
Our previous work2 focused on the binary system of diethyl and dibutyl adipates, highlighted the potential of adipates as low-temperature PCM, motivating further research into their solid-liquid phase change behavior and structure-property relationships. Building upon this initial study, we have expanded our research into a broader range of di-n-alkyl adipates.
One of the key aspects of our current research is the identification of eutectic compositions within adipate-based binary systems. Eutectic mixtures are particularly attractive as PCM enabling tunable phase transition temperatures to match specific TES requirements. Through the careful combination of results obtained from Differential Scanning Calorimetry (DSC), Hot-Stage Microscopy (HSM), and Raman Spectroscopy, a detailed phase diagram was methodically crafted to highlight the intricate eutectic behavior of these systems, identifying compositions that optimize thermal performance. In this study, the interplay between alkyl chain length and thermal behavior, particularly the influence of odd–even effects in binary systems is also approached. By selecting mixtures that combine odd-odd, even-odd or even-even substituent arrangements, we have explored how molecular asymmetry impacts solid-liquid phase change behavior. Our results reveal distinct trends, demonstrating how subtle structural variations can be leveraged to fine-tune the thermophysical properties of these materials. Our findings contribute to the growing field of organic PCM, demonstrating that di-n-alkyl adipates are viable candidates for low-temperature TES applications. By elucidating their phase change behavior, we provide a foundation for the innovative development of next-generation thermal storage materials, paving the way for more advanced and efficient solutions.
Description
Keywords
thermal energy storage Di-n-Alkyl Adipates Low-Temperature Phase change materials (PCM) Phase diagram
Pedagogical Context
Citation
Maria C.M. Sequeira1, Timur Nikitin, Fernando J.P. Caetano, Hermínio P. Diogo, João M.N.A. Fareleira, Rui Fausto; Tuning Thermal Performance: The Role of Molecular Asymmetry in Di-n-Alkyl Adipates for Efficient Low-Temperature Thermal Energy Storage; ICCT2025 - 27th IUPAC International Conference on Chemical Thermodynamics, July 20-24 2025, Porto, Portugal