Study on the Applicability of Photoswitch Molecules to Photo-controlled Thermal Energy in Different Organic Phase Change Materials
Organic phase change materials(PCMs)have been widely studied and applied in the field of energy storage due to reversible heat storage and release characteristics,high energy den-sity,optional operating temperature and no phase separation phenomenon.However,PCMs can-not achieve long-term energy storage and controlled heat release.As a kind of photoresponsive molecule,azobenzene molecule can realize photo-controlled phase change by the regulation of molec-ular structure,and store both photo-heat and phase change heat.In this paper,the controllable phase change behavior of two kinds of photoswitch molecules(AZO-A-14,AZO-O-14)in straight chain alkane and fatty acid phase change materials was studied after mixing in different proportions.The results show that the photoswitch molecules are more suitable for the phase change tempera-ture control of fatty acid phase change materials with different concentrations.The reason is that the polarity of fatty acid molecules is high,in which the photoswitch molecules at cis-metastable state can be well dispersed,preventing from nucleation.In addition,the photo-controlled tem-perature difference of the ester group grafted photoswitch molecule(AZO-A-14)is smaller than that of the ether group grafted photoswitch molecule(AZO-O-14),and the photo-controlled tem-perature difference of AZO-A-14 doped in PCMs is larger.Furthermore,we decouple enthalpy of phase transition and enthalpy of isomerization separately.This study provides ideas for the improvement,development and application of optically controlled phase change materials in the future.
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