Effects of in-situ acid dopants on the latent heat storage properties and morphology of palmitic acid @ polyaniline microencapsulated phase change materials

Abstract

Fatty acids (FA) based microencapsulated phase change materials (MePCMs) with acid doped polyaniline (PANI) as shell are promising multi-functional MePCMs. In order to investigate the effects of different in-situ acid dopants on the latent heat storage properties and the morphology of the prepared FA@PANI MePCMs, herein, we selected palmitic acid (PA) as a representative FA, and five kinds of PA@PANI MePCMs were prepared via interface polymerization of aniline with HCl, H3PO4, salicylic acid, p-aminobenzenesulfonic acid and taurine (TA) as in-situ dopants, respectively. Characterization of the prepared MePCMs revealed that when TA was used as in-situ dopant, PA@PANI MePCMs with good spherical morphology and high encapsulation ratio (R) could be obtained. Specifically, when the TA/aniline molar ratio was no more than 0.4, the latent heat of the prepared spherical PA@PANI MePCMs could attain 120 J/g, corresponding to an R of 55%. There was no chemical interaction existed between the PA core and the PANI shell, while the crystallinity of PA was not affected by the microencapsulation. On the other hand, the other four acids are unfavorable for obtaining PA@PANI MePCMs with high R and good spherical morphology. This work proved that TA is a suitable in-situ acid dopant for preparing in-situ acid doped FA@PANI MePCMs. It also implied that it is better to dop the PANI shell with strong proton acids after the FA@PANI MePCMs have been prepared where strong proton acid doped FA@PANI MePCMs are preferred.