Self-Healing Phase Change Salogels with Tunable Gelation Temperature

• Published in: ACS applied materials & interfaces Vol. 10; no. 17; pp. 14786 - 14795
• Main Authors: Karimineghlani, Parvin, Palanisamy, Anbazhagan, Sukhishvili, Svetlana A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.05.2018
• Subjects: phase change materials; shape stabilization; hydrated salts; temperature-responsive gels; self-healing
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.8b03080

Chemically cross-linked polymer matrices have demonstrated strong potential for shape stabilization of molten phase change materials (PCM). However, they are not designed to be fillable and removable from a heat exchange module for an easy replacement with new PCM matrices and lack self-healing capability. Here, a new category of shapeable, self-healing gels, “salogels”, is introduced. The salogels reversibly disassemble in a high-salinity environment of a fluid inorganic PCM [lithium nitrate trihydrate (LNH)], at a preprogrammed temperature. LNH was employed as a high latent heat PCM and simultaneously as a solvent, which supported the formation of a network of polyvinyl alcohol (PVA) chains via physical cross-linking through poly­(amidoamine) dendrimers of various generations. The existence of hydrogen bonding and the importance of low-hydration state of PVA for the efficient gelation were experimentally confirmed. The thermal behavior of PCM salogels was highly reversible and repeatable during multiple heating/cooling cycles. Importantly, the gel–sol transition temperature could be precisely controlled within a range of temperature above LNH’s melting point by the choice of dendrimer generation and their concentration. Shape stabilization and self-healing properties of the salogels, taken together with tunability of their temperature-induced fluidization make these materials attractive for thermal energy storage applications that require on-demand removal and replacement of used inorganic PCM salt hydrates.