Supramolecular Interactions Regulate Thermal Conductivity And Flexibility Of Poly(TA)-based Thermal Interface Materials

With the rapid development of electronic technology and energy science,complex,integrated,miniaturized and portable micro-nano electronic devices continue to emerge,putting forward more stringent requirements for the thermal power density and heat dissipation performance in the system.If the temperature rise of electronic devices cannot be effectively controlled,the working efficiency,reliability,and service life of the devices will be greatly degraded.However,the existing flexible thermally conductive composites still can't balance high thermal conductivity and flexibility,and crack damage easily leads to thermal management failure,making it difficult to meet the needs of the development of the electronic and power industry.Aiming at the above problems,this thesis intends to introduce supramolecular interactions into the polymer network to provide physical cross-linking points,reduce thermal interfacial resistance and promote self-healing to prepare thermally conductive composites.The purpose is to improve the thermal conductivity while taking into account the flexibility and self-healing properties of materials.Moreover,the application of thermally conductive composite materials in the field of thermal interface materials is explored.The main research contents of this paper are as follows:(1)Using natural small molecule thioctic acid(TA)as the monomer,Poly(TA)is formed by ring-opening polymerization after heating.The reaction between the active sulfur end of the poly(TA)molecular chain and the carbon-carbon double bond of 1,4-diisopropenylbenzene(DIB)builds a supramolecular network structure.Then,aluminum chloride(Al Cl₃)was added to introduce metal ion coordination bonds into the supramolecular network,and the supramolecular elastomer Poly(TA-DIB-Al)with high flexibility,self-healing and easy processing was prepared.FTIR,Raman and other characterizations were used to determine the crosslinking reaction between TA and DIB and the formation of metal ion coordination bonds.The effect of Al³⁺concentration on elastomer properties was investigated.The results show that the higher the Al3+concentration,the more internal physical cross-linking points,and the greater the strength of the elastomer.By adjusting the concentration of Al³⁺,the preparation of elastomers with elastic modulus as low as 0.1 k Pa and elongation at break as high as7200%can be achieved.The existence of various non-covalent bonds makes the elastomer have good self-healing properties at room temperature,high temperature and underwater.It can recover 91%of its original mechanical properties after 1 h.In addition,the network structure of dynamic covalent bonds and non-covalent bonds enables Poly(TA-DIB-Al)elastomers to be recycled and functionalized in a simple hot-melting manner.Finally,Al/Poly(TA-DIB-Al)composites were prepared by compounding Poly(TA-DIB-Al)with spherical aluminum particles.Under the loading of 70 wt%filler,the composite has good flexibility(Young's modulus:0.98 k Pa;elongation at break 1720%),self-healing(self-healing at 80°C for 4 h to restore 96%thermal conductivity)and high thermal conductivity(1.82 W/m K).Compared with silicon-based thermally conductive composites,it has lower thermal contact resistance and higher thermal conductivity,and has excellent heat dissipation performance and stability during practical application testing.(2)N,N-methylenebisacrylamide(MBA)was introduced into the supramolecular network through the reaction of the terminal active sulfur end of the Poly(TA)molecular chain with the carbon-carbon double bond.Supramolecules elastomers Poly(TA-MBA)with various hydrogen bond structures have high flexibility(Young's modulus:0.08k Pa,elongation at break>10000%),self-healing(self-healing for 1 h to restore 91%of mechanical properties),and easy processing properties.Elastomer.The structure of the network and the existence of hydrogen bonds were confirmed by FTIR,Raman and other characterization methods.The analysis of the mechanical and rheological properties of Poly(TA-MBA)shows that the increase of MBA content will form more cross-linking points in the interior,and the elastic modulus will also increase.Further analysis shows that the added MBA can form an ordered hydrogen bond structure,which can greatly enhance the mechanical and thermal conductivity of the elastomer.When the molar ratio of TA:MBA is 25:1,the thermal conductivity is as high as 0.72W/m K,which is 3 times that of traditional polymers.Finally,Al/Poly(TA-MBA)composites were prepared by compounding Poly(TA-MBA)elastomer with spherical aluminum particles.The 70 wt%thermally conductive filler-loaded composite exhibits good flexibility(Young's modulus:2.27 k Pa,elongation at break 510%),high thermal conductivity(2.21 W/m K)and self-healing performance(4h recovery at 80°C).its 95%thermal conductivity).It has lower contact thermal resistance than traditional silicone rubber-based composite materials,and exhibits good heat dissipation performance and stability during practical application testing.