Abstract: [Objective] 1,2,3,4-butanetetracar boxylic acid(BTCA) cross-linked cellulose nanofibril(CNF) aerogels were used to study the effects of cross-linking degree on the chemical characterization,morphological,and mechanical property of the CNF aerogels,which laid the foundation for further development of functional CNF aerogels.[Method] In this paper,we prepared the cross-linked CNF aerogels with different cross-linking degrees by adjusting the addition ratio of raw materials via freeze drying and post cross-linking method. The chemical characterization,morphological,surface area,pore size distribution,and mechanical property of the CNF aerogels were analyzed by means of Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),Scanning electron microscopy(SEM),BET measurement and mechanical tests.[Result] Results showed that:1) Compared with those of the pure CNF aerogel,the FTIR and XPS spectra of the BTCA cross-linked CNF aerogel were changed obviously,the absorption peak intensity of hydroxyl(-OH) was observed weaker and that of carbonyl absorption peak(CO＝) was enhanced significantly. The C1,C2 and C3 spectra of C1s in the XPS spectrum were all greatly changed,and the C4(O-C＝O) energy spectrum was fitted. 2) The pore structure of the cross-linked CNF aerogels changed from the original irregularly shaped pores to relatively regular columnar pores. With the increase of BTCA content,the specific surface area and total pore volume gradually decreased. When the m(CNF)/m(BTCA) was 10/1,the specific surface area and total pore volume of CNF aerogels were reduced from 62.8 m²·g^-1 and 0.21 cm³·g^-1 to 35.5 m²·g^-1 and 0.098 cm³·g^-1,respectively,reduced by nearly half. When the m(CNF)/m(BTCA) reached 10/4,the structure of the aerogel became loose and appeared the excessive esterification phenomenon. 3) The density of pure CNF aerogels was only 5.76 mg·cm^-3, and its compression rate was up to 62.4% under 100 g load while the compression rate was only 30%. With the increase of BTCA content, both the density and the compressive recovery rate of aerogel were gradually increased, while the compression rate decreased gradually. When the m(CNF)/m(BTCA) was 10/1,the aerogel was still with the low density(7.67 mg·cm^-3) and the high compression rate(56.8%) while its compression resilience rate increased significantly(80.8%); When the m(CNF)/m(BTCA) reached to 10/4,the density of the aerogel increased to 9.54 mg·cm^-3, and its compression rate(reduced to 34%) and resilient rate(increased to 95%) were both changed significantly.[Conclusion] The results confirmed that the addition of BTCA made the CNF aerogels internal forming covalent bonds cross-linked structure,and had a significant effect on the internal pore structure and physical mechanicals performance. The greater mass ratio of BTCA and CNF,the density of aerogel was greater and the pore structure was more compact,only when the mass ratio of BTCA and CNF was within a certain range,which could improve the deformation resistance and deformation recovery ability of CNF aerogel at the same time to keep its good flexibility,and improve its application value.

Key words: cellulose nanofibril (CNF), aerogel, 1,2,3,4-butanetetracarboxylic acid (BTCA), chemical cross-linked