Nano-holocellulose:Preparation And Properties

Fabrication of high-performance nanocellulose-based multifunctional materials via effective surface/interface engineering remains a great challenge.Nano-holocellulose,as a composite biomass nanomaterial composed of nanocellulose and hemicellulose,shows many advantages in surface/interface engineering to fabricate high-performance multifunctional materials.However,due to the nano-holocellulose structure’s particularity,there has been no comprehensive study on its preparation,properties,and advantages in surface/interface engineering and application.Therefore,starting from the structure of nano-holocellulose,this paper focus on its preparation process,properties,and surface/interface engineering in fabrication of multifunctional materials.The main works of this paper are as follows:（a）HCNFs were prepared from bagasse holocellulose via a mechanical process.At the same time,structure and properties changes of HCNFs were studied after non-derivatized enzyme and alkali treatment.The results showed that HCNFs are mainly composed of cellulose and hemicellulose,and their morphology is network-like nanofibrils.Single HCNFs nanofiber showed a diameter of～13 nm,which consists of～3.5 nm hemicellulose coated on～6 nm cellulose.In addition,the surface of HCNFs has abundant chemical functional groups and negative charges,especially hydrophobic acetyl groups.After enzyme treatment and alkali treatment,the content and thickness of hemicellulose,the content of acetyl groups,and the surface charge decreased,but the crystallinity index increased.In addition,the uniformity of HCNFs dispersion decreased,while thermal stability,stability of dispersion in water,and compatibility with water increased.（b）Bioinspired nano-holocellulose/carbon nanotube nanocomposites（HCNF/CNT）were fabricated by a self-assembly process,which was used as a liquid sensor to study its application performance.The results showed that the HCNF/CNT exhibited excellent electrical conductivity（conductivity 123 S/m）and mechanical properties（tensile strength 121MPa）and can be used as a liquid sensor with high sensitivity and stability.The well-preserved native hemicellulose in HCNFs could disperse CNTs uniformly as like as a surfactant,which caused HCNF/CNT with a regular orientation structure and lower interface resistance.At the same time,hemicellulose could enhance interfacial interaction between HCNFs and CNTs as like as“glue”,to obtain excellent mechanical properties.（c）Boron nitride nanosheets（BNNSs）were exfoliated via HCNFs assisted ultrasound treatment in water.Furthermore,BNNSs were functionalized by liquid metal（Gallium,Ga）dominated interface engineering and assembled with cellulose fibers into nanocomposite paper.This work focusses on the effects of synergy on nanocomposite paper properties.The results showed that surfactant-like HCNFs can effectively reduce the surface tension of the water and assist the ultrasonic exfoliation process of boron nitride.The resultant BNNSs possessed high yields,few surface defects,high aspect ratio,and excellent dispersibility in water.Phase Change Material Ga was introduced to surface of BNNSs through chelating of HCNFs and Ga³⁺.Owing to the Ga dominated interface engineering,the obtained nanocomposite paper exhibited outstanding integrated performance,especially excellent in-plane thermal conductivity(11.78 W m^-1 K^-1).The in-plane thermal conductivity of the nanocomposite paper was enhanced by well-designed interface engineering in two main aspects.Firstly,Ga could bridge the thermal conduction path among BNNSs.Secondly,Ga could fill the gaps between the cellulose fibers and fillers to replace air with low thermal conductivity.Finally,nanocomposite paper can be used as a flexible heat sink for thermal management of LED modules.（d）SHCNF were prepared from holocellulose via sulfamic acid derivatization and mechanical process.The esterification mechanism of two-component（hemicellulose and cellulose）in holocellulose was studied by reaction kinetics.Moreover,the structure and properties SHCNF were also studied.The results showed that morphology of SHCNF is single nanofiber with a diameter of 2～4 nm and a length of 1μm.SHCNF has abundant sulfate groups and negative charges.Kinetics illustrate the sulfate groups contents increased with the increase of temperature and showed a trend of first increase and then decrease with the increase of time.The derivatization of SHCNF has lower activation energy.Furthermore,SHCNF demonstrate hemicellulose dominated the competitive derivatization of holocellulose.SHCNF has advantages in dispersion stability,redispersion,rheological properties,mechanical property and transparency of fabricated film.