Research On The Preparation, Properties And Application Of Photochromic Phase Change Energy Storage Material

Multifunctional phase change materials with photochromic,thermal energy storage and temperature regulation have attracted wide attention and have broadened application prospects in wearable outdoor temperature regulation clothing,flexible wearable ultraviolet protective clothing,building materials,intelligent anti-counterfeiting,reversible optical data storage system,multi-purpose light response sensing system and other fields.In this paper,firstly,the comb-like alkyl polyacrylate was selected as the polymer matrix material of photochromic compound spiropyran(SP).SP was dissolved in alkyl acrylates with different alkyl side chain lengths by mini-emulsion polymerization and photochromic nanoparticles were prepared with sodium dodecyl sulfate,hexadecanol and dibenzoyl peroxide as emulsifiers,co-emulsifiers and initiators,respectively.The photochromic behavior of nanoparticles was studied at room temperature.The effects of alkyl side chain length of comb-like alkyl polyacrylate on photochromic performance,cycle durability,isomerization speed of MC→SP,UV-vis absorption spectrum and photodegradation resistance were further studied.The crystallinity and thermal performance of photochromic nanoparticles were analyzed in detail.The results showed that comb-like alkyl acrylate photochromic nanoparticles exhibit excellent optical response.The longer the alkyl side chain of comb-like polymer matrix,the higher the absorbance and the faster the MC→SP isomerization speed.Secondly,a novel chitosan-based polyurethane(c-PU)shell reversible photochromic phase change microcapsule(RP-PCMs)was successfully prepared by interfacial polymerization with butyl stearate as the core material and natural and nontoxic chitosan as the raw material.The mechanism of preparing c-PU shell was analyzed and discussed.The thermal properties,morphology and structure of microcapsules were systematically studied by various analytical techniques.C-PU shell microcapsules showed excellent latent heat performance(ΔHm=106.3 J/g,ΔHc=-105.1 J/g),high energy storage efficiency(E=71.4%),excellent thermal stability and cycle durability.Then,water-soluble polyurethane(WPU)was used as the medium to finish the RP-PCMs on cotton fabric,and the cotton fabric with photochromic properties was prepared.At the same time,the thermal properties,thermal stability,photochromic properties and temperature-regulating properties of cotton fabric/WPU/RP-PCMs were systematically studied,which made the cotton fabric/WPU/RP-PCMs show a broad application prospect in the field of intelligent flexible temperature-regulating photochromic clothing.Finally,c-PU shell microcapsules were modified by acid hydrolysis with dodecanol(LA)and tetraethyl orthosilicate as precursors,and SiO2@c-PU composite shell was successfully prepared.LA was added to the core material to consume unreacted hexamethylene diisocyanate,and excess LA can also be used as PCMs and encapsulated in microcapsules.The thermal conductivity of SiO2@PCMs was 18.75%higher than that of PCMs,and SiO2@PCMs also showed excellent light-heat conversion.