Studies On Design,synthesis And Dielectric Phase Transition Of Quaternary Ammonium Compounds Containing Ring Structure

Dielectric phase transition material is a kind of novel multifunctional composite material with stimulation response.Its photoelectricity and other properties could be subjected to external stimuli to achieve bistable or multi-stable switching,so that it has a broad application prospect in intelligent control,signal processing,sensing,photoelectric switch and other fields.The properties depend on the structure,it is still a challenging task to accurately construct compounds with dielectric phase transition by molecular structure design.Due to its unique organic and inorganic composition,organic-inorganic hybrid materials show excellent structural flexibility and rich physical properties,and are potential phase change materials.In previous studies,we found that some cyclic organic amine cations containing piperidine,piperazine,cyclohexylamine and other cyclic structures are susceptible to temperature and undergo thermal motion thus to cause phase transitions.On this basis,we designed and synthesized ten organic-inorganic hybrid compounds with organic cyclic quaternary ammonium salts as cations,and analyzed their crystal structure,thermal and dielectric properties and phase transition,etc.This thesis is divided into three parts:(1),the compounds with quaternary ammonium salt of methylpiperidine as cations,[C₈H₁₇NF][Cd(SCN)₃](compound 1),[C₈H₁₇NBr][Cd(SCN)₃](compound 2)?[C₇H₁₅NCl][Cd Br₃](compound 3).(2),the compounds with N-aminoethyl piperazine as ligand are[C₆H₁₇N₃][Sb Cl₃]₂(Compound 4),[C₆H₁₇N₃]₂[Mn Cl₆](Compound 5),[C₆H₁₇N₃][Cd Cl₄](Compound 6).(3),the compounds synthesized based on N,N-dimethylcyclohexylammonium derivative are[C₉H₁₉NBr][Mn Cl₄](compound 7),[C₉H₁₉NBr][Cl O₄](compound 8),[C₉H₁₉NCl][Cd(SCN)₃](compound 9),[C₉H₁₉NCl][Cl O₄](compound 10).In conclusion,ten compounds were synthesized and their structures and properties were measured and analyzed by means of dielectric,differential scanning calorimetry(DSC)and X-ray single crystal diffraction.Among them,compounds 1,2,8 and 9 undergo reversible phase transition,and the relationship between phase transition behavior and molecular structure are analyzed.This thesis provides some ideas and experimental basis for the targeted search for new dielectric phase transition compounds and the regulation of phase transition behavior through mocular structure design.