Preparation and Properties of Cellulose Nanomaterials

Dufresne Alain
Université Grenoble Alpes,CNRS,Grenoble INP,LGP2,Grenoble,F-38000,France

Abstract：Cellulose is the most abundant biomass material in nature and it is mainly extracted from natural or lignocellulosic fibers. After purification, cellulose fibers exhibit two interesting features for their further transformation into nanomaterials: a hierarchical and multi-level strcture, and a semicrystalline microstructure. Different forms of cellulose nanomaterials, resulting from a top-down deconstructing strategy(cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs)) or bottom-up strategy (bacterial cellulose (BC)) can be prepared. Multiple mechanical shearing actions applied to cellulosic fibers release more or less the nanofibrils individually. A controlled strong acid hydrolysis treatment can be applied to cellulosic fibers allowing dissolution of non-crystalline domains. Such cellulose nanomaterials have been the focus of an exponentially increasing number of works or reviews devoted to understand such materials and their applications. They have a high potential for an emerging industry. In the nanoscale, cellulose exhibits specific properties broadening the applications of this naturally occurring polymer. An overview of existing methods for the preparation of cellulose nanomaterials and their specific properties that outperform and contrast with cellulose in the microscale is proposed.

Key words：cellulose;nanomaterial;nanocrystal;nanofibril;preparation;properties

DOI：10.12103/j.issn.2096-2355.2020.03.001

Cellulose Nanocrystals-based Chiroptical Materials

Jiawei Tao Yan Xu*
State Key Laboratory of Inorganic Synthesis&Preparative Chemistry,Jilin University,Changchun,Jilin Province,130012,China

Abstract：Chiroptical materials are widely used in photonic devices, enantioselective catalysis and bio-sensors. Cellulose-base chiroptical materials with multilength scale structural hierarchy and unique light manipulation ability found in nature provide inspiration for materials design. Cellulose nanocrystals (CNC) display twisted rod morphology and hierarchical chirality. Leveraging the evaporation-induced selfassembly of negatively charged CNC, a broad realm of CNC-based chiroptical materials featuring one-dimensional photonic bandgap and novel chiroptical properties have been developed, which are of scientific and technological significance. Here we presented a brief overview on CNC-based chiroptical materials by evaporation-induced self-assembly, showed energy and chirality transfer in a host-guest environment leading to photonic bandgap modulation of optoelectronic properties, outlined novel chiroptical phenomena and their underlying principles,and demonstrated the application potentials of the CNC-based chiroptical materials.

Key words：cellulose nanocrystals;chiroptical materials;photonic bandgaps;optoelectronics;energy and chirality transfer

DOI：10.12103/j.issn.2096-2355.2020.03.002

Modification of Cellulose by Hydrophobic Long-chain Molecules:Advances and Prospects

Yuyuan Wang Haishan Zhang Leyi Lin Rui Wu Xiaoying Wang Junli Ren Chuanfu Liu Xiaohui Wang*
State Key Laboratory of Pulp and Paper Engineering,South China University of Technology,Guangzhou,Guangdong Province,510640,China

Abstract：Cellulose, a natural polymer material with abundant natural sources, is non-toxic, renewable, and biodegradable, making it one of the most promising green materials. Its inherent hydrophilicity dramatically limits the development and application of cellulose products.Hydrophobic modification can significantly change cellulose properties and endow it with additional functions depending on the types of modifying molecules. Controlled modification of cellulose by long-chain hydrophobic molecules is challenging. Significant advances took advantage of new reaction systems and copolymerization. This paper reviews recent innovations in long-chain cellulose hydrophobic modification. A brief value-adding assessment provides a reference for green changes of cellulose to make it fit for future applications.

Key words：cellulose;hydrophobic;chemical modification;long-chain

DOI：10.12103/j.issn.2096-2355.2020.03.003

Etherification of Alkali-pretreated Sugarcane Bagasse Cellulose in Tetrahydrofuran

Shiyu Fu*Chuanlong Xie
State Kay Laboratory of Pulp and Paper Engineering,School of Light Science and Engineering,South China University of Technology,Guangzhou,Guangdong Province,510640,China

Abstract：Sugarcane bagasse (SCB) is an important by-product in the sugar industry. It is a source of cellulose fibers or cellulose for paper mills and textiles factories. In this study, SCB was ethyl etherified in tetrahydrofuran (THF) after alkali pretreatment. The alkali concentration for the pre-treatment, the ratio of ethyl bromide (EtBr) to dried SCB in the reaction, reaction time, and temperature were investigated for the etherification of SCB. The ethoxyl content and characterization of the product were determined using headspace gas chromatography (HS-GC), Fourier Transform Infrared (FT-IR) and13C-NMR spectroscopy, respectively. It was found that SCB was welletherified with EtBr in alkali-THF. Upon ethylation of SCB,the ethoxyl content of the product was high when the alkali concentration and the ratio of EtBr to dried SCB were controlled from 50% to 75% and 4:1 (V/w) to 6:1 (V/w), respectively. The reaction occurred optimally when the temperature was controlled below 110℃;above this temperature,the degree of etherification decreased. The thermal stability of ethylated SCB was higher than that of SCB but slightly lower than that of commercial ethyl cellulose. Ethylated SCB has the potential to form composites with many materials because it is soluble in a wide variety of solvents.

Key words:sugarcane bagasse;alkali pretreatment;etherification;ethylated SCB cellulose

DOI：10.12103/j.issn.2096-2355.2020.03.004

Effect of Thermal Treatment on the Properties of TEMPO Oxidized Cellulose Film for the Flexible Substrate of Solar Cell

Changmei Lin Hui Zhang Qidu Deng Liulian Huang Xiaojuan Ma*Shilin Cao*
College of Materials Engineering,Fujian Agriculture and Forestry University,Fuzhou,Fujian Province,350002,China

Abstract：The 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose film (TOCF) has been attempted to be used as a substrate in electronic and optoelectronic devices, but the changes in the TOCF properties before and after annealing treatment have usually been neglected during device fabrication. In this study, TOCF was treated in different atmospheres (air, vacuum, and N2) and at different temperatures, and the properties were investigated. The results indicate that the optical properties are slightly affected by atmosphere and temperature; only slight transmittance loss and haze increase have been observed when TOCF is exposed to an air atmosphere at temperatures of above 120℃. In contrast to the slight effects on the optical properties, cellulose degradation and a loss of film strength have been observed regardless of the atmosphere used when placed at temperatures of above 100℃. Specifically, TOCF was exposed to air,followed by N2and vacuum atmospheres. Additional Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) results showed that increasing the temperature had no significant effect on the structure of TOCF. Therefore, the annealing temperature should be controlled at a temperature of lower than 100℃and a vacuum atmosphere is preferred.

Key words:TEMPO oxidized cellulose film;thermal treatment;transmittance;haze

DOI：10.12103/j.issn.2096-2355.2020.03.005

Effects of MFC-modified GCC as Filler on the Opacity of Pulp Handsheets

Yanqun Su1,2Junjie Liu1,*Jingang Liu1,2Ruijuan Zhang1,2Jinghuan Chen1,2Yanfen Du1,2
1.China National Pulp and Paper Research Institute Co.,Ltd.,Beijing,100102,China;2.National Engineering Laboratory for Pulp and Paper,Beijing,100102,China

Abstract：Microfibrillated cellulose (MFC)was obtained by mechanical grinding of different pulps. MFC-modified ground calcium carbonate(GCC) was prepared in two different ways, designated MFC-GCC composite filler and MFC-GCC flocs filler. The opacity of pulp handsheets loaded with MFC-modified GCC was measured. The effects of MFC originated from different pulps, pretreatment method, and filler modification on the opacity of handsheets loaded with MFC-modified GCC were discussed. The results show that MFC originated from alkaline peroxide mechanical pulp (APMP) was optimal for improving the opacity of the handsheets and PFI grinding pretreatment for MFC provided a denser structure in the corresponding MFC APMP-GCC floc filler while enzyme pretreatment was more effective inincreasing the opacity of the filled paper. Under the experimental conditions, the opacity of handsheets increased from 81.0% to 82.7% when the unmodified GCC was replaced by an equivalent amount of MFC APMP-GCC composite filler,while other properties were unchanged.

Key words：microfibrillated cellulose;ground calcium carbonate;modification;opacity

DOI：10.12103/j.issn.2096-2355.2020.03.006