Reactive Graphene Dispersant And The Application In Carbon Doped Energy Storage Coatings

Graphene(GR)is a two-dimensional nanomaterial composed of sp~2-hybridized carbon atoms with excellent chemical and physical properties,which has attracted extensive attention in the fields of energy,biosensing,catalysis,and medicine.However,the strong?-?interactions among the GR sheets make their dispersion in the solvent severely affected,which is unfavorable for further processing.Functional modification or modification of GR can improve its dispersion properties.Compared with chemical modification,functionalization through?-?,H-?and other non-covalent bonds will not cause damage to the structure of GR,and can better maintain its inherent properties.However,there are still widespread problems such as large amount of dispersant and low GR dispersing concentration.Excessive dispersant residues can largely affect the properties of composites,so it is of great significance to impart additional functions to the dispersants,which in turn can be converted into useful components.Aiming at this problem,this thesis designed and synthesized a new type of GR dispersant with high reactivity,which can not only disperse GR in high concentration in water and ethanol,but also use its silanols to cross-link reaction with other components.With its assistance,nano-carbon materials such as GR were successfully compounded into the silanol-modified polyethylene glycol polymer to obtain a phase-change energy storage coating.The phase change energy storage coating prepared in this way has many advantages,such as high mechanical strength,fast heat transfer rate,high phase change enthalpy,and good thermal stability.The main research contents and results of the paper are as follows:1.A highly reactive GR dispersant containing multiple silyl hydroxyl groups with naphthalene ring as the conjugated center was synthesized.First,using1,5-diaminonaphthalene,epichlorohydrin,ethylenediamineand3-glycidyloxypropyltrimethoxysilane(GPTMS)as raw materials,through a series of substitution and ring-opening reactions,a naphthalene derivatives of multiple silyloxy groups(-Si-OCH₃);Then,it is hydrolyzed under acidic conditions,and the methoxy groups are converted into silanol groups(-Si-OH)to obtain dispersant molecules.The synthesized dispersant(MSi ND)has good dispersing ability for both GR and carbon nanotubes(MWCNTs).Under the ratio of dispersant and its mass ratio of 1:1,the highest concentration of GR in water and ethanol can reach 16 mg m L^-1and 12 mg m L^-1,respectively,and can be kept for 3 months without natural standing settlement.The ability of MSi ND to disperse GR efficiently was proved by means of centrifugal acceleration test,Zeta potential,SEM,and TEM.The stability of the dispersion is mainly due to the strong?-?interaction between the conjugated structure of the naphthalene ring and the GR,and the multiple silanol groups on both sides of the molecule are beneficial for the dispersant to dissolve in other polar solvents such as water and alcohol.A large number of silanol groups on the dispersant also have high reactivity and can be cross-linked with other materials through dehydration condensation.2.With the aid of dispersants,GR,carbon nanotubes,etc.were successfully compounded with PEG-based phase-change polymers uniformly to prepare high-performance phase-change energy storage coatings.First,polyethylene glycol(PEG 10000)was modified by 3-isocyanatopropyltriethoxysilane(IPTS);and then hydrolyzed under acidic conditions to obtain reactive polyethylene glycol containing silyl hydroxyl groups at both ends of the molecular chain;Finally,it is simply physically blended with the aforementioned dispersion to obtain a nanocarbon-doped phase change energy storage coating.After the coating is applied,the dehydration condensation between the silyl hydroxyl groups can form a silyl ether bond,and the PEG molecules can be cross-linked to each other to obtain an energy storage coating with solid-solid phase transition behavior.In the absence of carbon doping,its phase transition enthalpy can be as high as 142.8 J g^-1,and the original intact solid state can be maintained when heated to 100?.After the incorporation of GR or CNTs,a higher-density cross-linked network is formed between PEG and GR due to the further cross-linking effect of the dispersant,so the composite coating exhibits more excellent high-temperature morphological stability and rapid heat exchange performance.Although the phase transition enthalpy of the composite coating with0.5 wt%GR doping amount decreased slightly(138.6 J g^-1),the phase transition temperature and enthalpy hardly changed after 100 heating-cooling cycles.The uniform composite of carbon materials increases the thermal conductivity of composite materials to a large extent.With only 0.5 wt%GR doping,the thermal conductivity is increased by about 36%.The composite coating is suitable for a variety of substrate materials,especially for the construction of energy storage coatings on the surface of irregular substrates,and has absolute advantages compared with most powder,granule or rigid block phase change materials.It has broad application prospects in flexible wearable thermal insulation fabrics,masks,buildings and pipeline thermal insulation.