| Tunicate is a kind of marine animal and its outer sheath is consisted of almost pure I_?crystalline cellulose.Due to its high aspect ratio,tunicate cellulose has excellent physical properties.Recently,it draws extensive attention in the construction of robust functional materials.However,there is few research on its biological activity.Aerogel,which is made from tunicate cellulose nanocrystals,is a new type of raw material.It has many advantages,such as excellent mechanical properties,light weight,controllable porous structure,reproducible,biodegradable and abundant resources.It has been widely applied in biomedical scaffolds,oil-water separation materials,thermal insulation materials,energy storage and power generation equipment.Therefore,the development of high strength tunicate cellulose nanocrystal aerogels and its performance are of great significance for the wider exploration of aerogels.In this paper,cellulase hydrolysis and antifungal experiments were used to study the biodegradability of tunicate cellulose.After that,the stable tunicate cellulose nanoscale solution was obtained from the tunicate through acid hydrolysis and ultrasonic dispersion treatment.Finally,the composite aerogels were prepared by freeze drying method and the properties of the composite aerogels were studied.(1)Study on the preparation and biodegradation resistance of tunicate cellulose nanocrystals.In this study,the tunicate cellulose nanocrystals with high aspect ratio was prepared by acid hydrolysis.In the process of enzymatic hydrolysis,the crystalline behaviors,i.e.crystallinity index(Cr I),crystalline size and degree of polymerization(DP),were analyzed on the tunicate cellulose.As comparisons,similar hydrolysis were performed on cellulose samples with relatively low Cr I,namely?-cellulose and amorphous cellulose.The results showed that,after 96h hydrolysis,the crystallinity,crystalline size and DP remained constant on the tunicate cellulose and the cellulose conversion rate was below 7.8%.While the crystalline structure of?-cellulose was significantly damaged and the cellulose conversion rate exceeded 83.8%at the end of 72 h hydrolysis and the amorphous cellulose was completely converted to glucose after 7 h hydrolysis.In addition,through the mold experiment,when the culture medium contained 100%tunicate cellulose nanocrystals,the growth rate of mold was zero after 96 h.It can be concluded that tunicate cellulose has significant resistance to enzymatic hydrolysis and could be potentially applied in anti-biodegradation materials.(2)Freeze drying and silylation of TCNC and silica nanoparticle suspension were used to prepare superhydrophobic hydrogels by impregnating the poly(DOPA_m-co-PFEA)solution.IR and XPS analysis showed that the composite aerogels showed obvious silicon and fluorine elements,indicating that aerogels were covered by low surface energy materials.The contact angle of composite aerogel was 158.7°and had good chemical stability.After 72 h impregnating in p H=0 and p H=12 solution,the contact angle of aerogel was still greater than 150°.In addition,the composite aerogel can separate the surfactant stable emulsion in the absence of external pressure,and it can be repeatedly used repeatedly.It shows that it has great prospects in the field of oil-water separation.(3)Different aerogels were prepared by freeze drying method using TCNCs,graphene oxide and sepiolite as raw materials.The results showed that the mechanical properties of the composite aerogels increased with the decrease of the temperature and the addition of graphene oxide.In addition,with the increase of graphite oxide content,the composite aerogel decreased by 23%compared with the pure aerogel.In the alcohol lamp combustion experiment,the pure aerogel completed the process of flame contact combustion to extinction in 9 s,while the composite aerogel self-extinguishing in 0.42 s.Surprisingly,when the composite aerogel was immersed in ethanol,the self-extinguishing behavior occurred at 12 s.After quenching,the composite aerogel basically kept its original shape and did not collapse.The composite aerogel has good thermal insulation and flame retardancy. |
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