Preparation And Energy Storage Behavior Of Poly(di)ethylene Glycol N-alkyl Vinyl Ether

The mismatch between energy supply and demand in time,region and space has increasingly become a key factor constraining sustainable development.The research and development of new types of energy storage and conversion materials are hot spots for the current and future periods.PCM(Phase Change Material),especially solid-liquid,solid-solid PCM,are green,reusable thermal energy storage materials with small volume change and high energy storage density in the phase change process.PCM is most promising to be widely used in solar energy storage,waste heat recovery,energy-saving buildings,agricultural greenhouses,pavements,vehicles,electronic product cooling and smart textiles.Small molecule phase change materials need to be encapsulated when they are applied,which increase the production cost.When the composite phase change materials are used repeatedly,some small molecules will leak and the energy storage efficiency will decrease as a result.The polymeric phase change materials have a low degree of supercooling and a good thermal stability,so they can be used for many cycles.Polymeric phase change materials mainly include:graft polymers,block copolymers,cross-linked polymers and homopolymers.In order to obtain a polymeric phase change material with moderate phase change temperatures and possessing a high heat storage efficiency,our group has prepared a series of homopolymer-type comb-like polymeric phase change materials:poly(n-alkyl acrylate),poly(diethylene glycol-n-alkyl acrylate)and poly(diethylene glycol n-alkyl methacrylate),etc.In this paper,a series of poly(mono/diethylene glycol n-alkyl vinyl ether)homopolymer phase change energy storage materials were prepared.Based on the parts of preparation and characterization of mono/diethylene glycol-n-alkyl vinyl ether,poly(mono/diethylene glycol-n-alkyl vinyl ether)and poly(mono/diethylene glycol n-tetradecyl ether vinyl ether)s with various molecular weights,the following conclusions were drawn:It was found that the melting enthalpy and crystallization enthalpy values of mono/diethylene glycol n-octadecyl ether vinyl ether and mono/diethylene glycol n-hexadecyl ether vinyl ether were not equal,and these four monomer compounds had polymorphism.While there are one pair of melting/crystallization peaks appeared in the heating and cooling process of mono/diethylene glycol n-tetradecyl ether vinyl ether and mono/diethylene glycol n-dodecane ether vinyl ether,and the melting enthalpy and crystallization enthalpy for each compound were equal.It was shown that with the length of alkyl chain increasing,the influence of terminal groups on the crystallization of alkyl chains became more and more significant.A series of poly(mono/diethylene glycol n-alkyl vinyl ether)s were prepared via cationic polymerization.The side chain was linked to the backbone of the polymer via ether bonds.The introduction of the ether bond further reduced the limitation of the polymer backbone on the crystallization of the alkyl side chain compared to the previous ester bond.For poly(diethylene glycol n-hexadecyl vinyl ether),the critical carbon atoms number that could form crystals in the alkyl side chain is 6.8,which was lower than 9 of poly(n-alkyl acrylate).A series of poly(mono/diethylene glycol n-tetradecyl ether vinyl ether)s with various molecular weights(7,000-25,000)were prepared and the effects of molecular weights on the thermal storage properties of the polymers had been investigated.The results showed that the phase change enthalpy of the polymers decreases significantly with the increase of molecular weights.When the molecular weight of the polymers was up to 20,000,the phase change enthalpy remained unchanged.As the molecular weight increasing,the phase transition temperatures also showed a slightly increase,and the thermal stability of the polymers was also improved dramatically.