The Design And Synthesis Of Organic-Inorganic Hybrid Phase Change Materials By Quasi-Spherical Molecules

Compared with the common phase separation and undercooling phenomenon of inorganic phase change materials and the shortcomings of organic phase change materials such as low phase change temperature,low density and volatile,due to their significant structural variability and high adjustability,organic-inorganic hybrid materials avoid the drawbacks of inorganic and organic phase change materials in the aspect of single properties,so more and more researchers pay attention to them.As soon as the"quasi-spherical theory"was put forward,it attracted great attention and provided a new idea for the exploration of phase change materials.Phase change materials above room temperature are more important as key components in many fields due to their high phase change temperature,which provides a wide temperature operating range and high stability for production.Chemical modification is an effective strategy to improve the phase transition temperature of compounds.Therefore,a series of hybrid compounds of organic and inorganic were designed by combining"quasi-spherical theory"with chemical modification,and the research content of this paper was divided into the following three parts:In the first part,four organic molecules([Me C₆N₂H₁₃]I、[C₇N₂H₁₅Cl]Cl、[C₈N₂H₁₇Br]Br、[C₈N₂H₁₇Br]Br)were obtained by chemical modification of spherical molecules（1,5-diazodicyclic[3.3.0]octane）.By reacting with tetrahedral acids（HCl O₄,HRe O₄ and HBF₄）,seven compounds were obtained as[Me C₆H₁₃][Cl O₄]（1）,[Me C₆H₁₃][Re O₄]（2）,[C₇N₂H₁₅Cl][Cl O₄]（3）,[C₇N₂H₁₅Cl][Re O₄]（4）,[C₇N₂H₁₅Br][Re O₄]（5）,[C₇N₂H₁₅Br][BF₄]（6）,[C₈N₂H₁₇Br][BF₄]（7）.The structure of the compounds was confirmed by IR、PXRD and xrd,and then the properties were characterized by DSC（Differential scanning calorimetry）.The characterization results show that compounds 1-7 are all organic-inorganic hybrid phase change materials（the inorganic part is tetrahedral acid）with reversible phase transition.The phase change temperature of compound 6 is up to 486 K,which belongs to high phase change temperature in non-metallic organic-inorganic hybrid phase change materials,and has a wide application prospect.In the second part,the obtained quasi-spherical molecules（1,5-diazodicyclic[3.3.0]octane）and their derivatives([Me C₆N₂H₁₃]I and[C₈N₂H₁₇Cl]Cl)were reacted with inorganic salts to obtain three compounds 8-10.The three compounds were[1,5-3.3.0-H₂dabco]NH₄I₃（8）,[Me Hdabco]₂Cd I₄（9）,[1,5-3.3.1-H₂dabcn]Cu Cl₄（10）.The structure of the compounds was confirmed by IR、PXRD and xrd.The properties of the compounds were characterized by DSC and SHG（second harmonic generation）.The results showed that,except for compound 10,compounds 8 and 9were organic-inorganic hybrid phase change materials with reversible phase transition（the inorganic part was salt）,and compound 9 showed reversible frequency doubling signal in the temperature range of 210-330 K,and showed good reversible NLO（Nonlinear optics）switching activity in the five-cycle test of LTP-HTP-LTP（LTP:A state below the temperature of a phase transition;HTP:A state above the temperature of a phase transition）.It is a kind of second-order nonlinear optical switching material with stable performance and good reversibility.In the third part,[C₈N₂H₁₇Br]Br was obtained by chemical modification of the obtained quasi spherical molecule（1,5-diazodiheterocyclic[3.3.0]octane）,which was reacted with ammonium halides and alkali metal halides to obtain five three-dimensional perovskite（The general formula is ABX₃,A is generally composed of organic cationic groups,located at the apex of the octahedron,B is a metal or non-metallic cationic,X represents the halogen）..The three compounds were[1,5-3.3.1-H₂dabcn]NH₄Cl₃（11）,[1,5-3.3.1-H₂dabcn]NH₄Br₃（12）,[1,5-3.3.1-H₂dabcn]Cs Cl₃（13）,[1,5-3.3.1-H₂dabcn]Cs Br₃（14）,[1,5-3.3.1-H₂dabcn]Rb Br₃（15）.The structure of the compounds was confirmed by IR、PXRD and xrd.The properties of the compounds were characterized by DSC and SHG.The results showed that except for phase transition of compound 13 is irreversible,the other four compounds showed reversible phase transition,and compounds 11,14,and 15 exhibited reversible frequency doubling signals within the scope of the melting point,and have stable switchable NLO switching activity and the unattenuated SHG signal in multiple cycle tests.It is worth noting that Tc（11）=246 K,Tc（12）=435 K,Tc（13）=439 K,Tc（14）=465 K,Tc（15）=443 K.Tc（11）<Tc（12）,Tc（13）<Tc（14）,it is concluded that Tc（ABCl₃）<Tc（ABBr₃）is the phasetransition point of the same organic amine and the same inorganic cation but X（X=Cl or Br）is different.Tc（11）<Tc（15）<Tc（13）,Tc（12）<Tc（14）,indicating that the compounds obtained from the same organic amine and the same halogen anion and different inorganic cations,inorganic cations have higher Curie temperature than compounds with large molecular weight.In a word,by introducing“quasi-formational”molecules and chemically modifying them to react with inorganic tetrahedral acids and inorganic salts respectively,13 kinds of organic-inorganic hybrid phase change materials with reversible phase change are obtained,which are compounds 1-9,11-12,14-15.Compounds 9,11,14-15,which have reversible frequency doubling and good reversible NLO（nonlinear optical）switching activity,are obtained.This paper provides a new design idea for further exploration of phase change materials.