Structure Regulation Of Chitin Nanocrystals And Its Application In Gel Materials

Chitin is a natural polysaccharide macromolecular substance with abundant sources,which is difficult to use directly.However,chitin nanocrystals(Ch NCs)can be obtained by mechanical or chemical reactions.Ch NCs have unique needle shape,high longitudinal modulus,high aspect ratio,large specific surface area,water dispersion stability,good biocompatibility and other excellent properties.It is a new type of natural nanomaterials which is easy to function and biodegrade.It is of great value to explore and develop applications of Ch NCs in more fields.In this paper,the structure control of Ch NCs and its application in gel materials are discussed.(1)Chitin nanocrystalline was obtained by acid hydrolysis of purified chitin.The dispersion and good interfacial compatibility of chitin nanocrystalline were improved by grafting polyethylene glycol on the surface of Ch NCs,so that the enhancement effect was greatly improved.A freeze-resistant PVA/PEG-Ch NCs organohydrogel was prepared by using dimethyl sulfoxide and water solvent system.Moreover,the conductivity of 0.01 S/m can be maintained at-20℃.Organohydrogels have good mechanical properties and electrical conductivity and can be used as strain sensors.The organohydrogel-based sensor has a high gague,a gague factor of 2.3,and can repeatedly and stably monitor tiny strains under tensile and pressure.Therefore,the ionic conductive organic hydrogel sensor based on PVA/PEG-Ch NCS has a broad application prospect in wearable devices,such as motion monitoring or health monitoring.(2)Vertically aligned ice crystals were prepared by directional freezing,and then the chitin nanocrystalline aerogel with vertically aligned channels was obtained by freeze-drying.The stability of chitin nanocrystalline aerogel in aqueous solution was enhanced by chemical crosslinking of glutaraldehyde.Aerogels with vertically aligned channels were compared with aerogels with irregular channels under simulated sunlight to simulate seawater desalination.It was found that the evaporation rate of chitin nanocrystalline aerogels with vertically aligned channels reached 12.197 kg/m~3/h under 10 suns.The evaporation rate of aerogels with irregular channels was 10.69 kg/m~3/h.In addition,aerogels also had high interception ability to oil droplets and dyes,and the interception rate was more than 93%.Therefore,vertical channel aerogels are a new kind of natural multifunctional gel materials.(3)Multifunctional aerogel materials with photothermal,heat transfer and joule thermal characteristics were prepared by calcination aerogel.After full calcination,it becomes almost all carbon material with a density of 0.192 g/cm~3,a porosity of 75%.It also has certain mechanical properties and excellent electrical conductivity,Calcined aerogel shows excellent photothermal properties,for example,calcined aerogel can be raised to 310~oC within 60 s.The calcined aerogel also showed excellent joule heating performance.For example,the surface temperature of the calcined aerogel increased rapidly to 330~oC within 5 s.The temperature rise was related to the applied voltage and the cross-sectional area of the gel.In addition,it has good heat transfer performance and can be used as a thermal interface material.This multi-functional calcined aerogel integrates thermal,joule and heat transfer characteristics,and has the advantages of low cost and environmental friendly,which has broad prospects in the fields of thermal photoelectricity,crude oil treatment and heat dissipation materials.