The Structure And Function Design And Application Of Nano-cellulose-based Gel Materials

Nanocellulose is a good substrate for the preparation of gel materials due to the high crystallinity,high purity,high strength,high Young's modulus,lightweight,biocompatibility,reproducibility and degradability,which has been widely concerned.At present,it is an important research direction to search for the method of preparing multifunctional nano-cellulose based gel materials.At the same time,explore the relationship between the structure and properties of the gel is also important.In this paper,three kinds of hydrogel and aerogel materials were prepared by chemical method,physical method and physicochemical combination method.The formation mechanism of gel and its application in heavy metal ion adsorption and drug release were studied.The relationship between the chemical composition,structure and application properties of gel was also discussed.The specific studies are as follows:?1?Interpenetrating network?IPN?hydrogels based on nanofibrillated cellulose?NFC?and poly?2-?dimethylamino?ethyl methacrylate??PDMAEMA?were prepared via crosslinking free radical polymerization.Attenuated total reflection-Fourier transform infrared spectroscopy?ATR-FTIR?and thermogravimetric analysis?TGA?confirmed the formation hybrid network of NFC and PDMAEMA.The IPN hydrogels possess uniform pore structure and high porosity?>97%?.The specific surface area and compressive strength were higher than 82 m² g^-1 and 1.26kPa,respectively.Water swelling experiments showed that the IPN hydrogels were both pH-sensitive and temperature-sensitive.The swelling of hydrogels was limited at high temperature and in neutral medium.There was an increase in the swelling ratio as the NFC content increased.Adsorption kinetic and thermodynamics studies of Cu?II?and Pb?II?explained pseudo-second-order equation and Langmuir model?R²>0.99?as the best fit.The maximum adsorption capacities of Cu?II?and Pb?II?according to Langmuir model were 217.39 mg/g and 81.96 mg/g,respectively.The good adsorption performance can be attributed to the chelation of tertiary amine groups and the ion-exchange of carboxyl groups.?2?This study describes the preparation of an aerogel adsorbent based on nanofibrillated cellulose?NFC?and polyethyleneimine?PEI?via electrostatic combination without chemical crosslinking.Purely physical crosslinking between NFC and PEI was confirmed by attenuated total refraction-Fourier transform infrared spectroscopy?ATR-FTIR?and thermogravimetric analysis?TGA?.The NFC/PEI hybrid aerogels exhibited good structural stability and shape recovery in water.Absorption experiment shows that the hybrid aerogels are excellent adsorbents for the removal of heavy metal ions owing to the highly porous structure and the existence of plenty of amine groups.Thermodynamic and kinetic study showed pseudo-second-order equation and Langmuir model?R2>0.999?as the best fit.The maximum adsorption capacity of Cu?II?and Pb?II?according to Langmuir model were 175.44 mg/g and 357.44 mg/g,respectively.Besides,the Cu?II?or Pb?II?loaded NFC/PEI aerogel could be easily regenerated by EDTA and retain the adsorption capacity after repeatedly using.This environmentally friendly hybrid aerogels with high-performance are promising candidates for sewage disposal and metal pollution treatment.?3?A composite aerogel with controllable porosity,reversible crosslinking structure and biocompatibility was constructed by combining hydrogen bonding and chemical crosslinking.The hydrogen bonding,acetalization and Schiff base reaction between NFC and gelatin were confirmed by attenuated total refraction-Fourier transform infrared spectroscopy?ATR-FTIR?.Thermogravimetric analysis showed that the maximum thermal decomposition rate of composite aerogel was at 320?.Scanning electron microscopy?SEM?and BET analysis showed that the aerogels have uniform pore structure and high porosity.The specific surface area,pore volume,pore size distribution and porosity increase with an increase of the NFC dosage.The highest specific surface area is up to 103.17 m²/g.The swelling property shows that the swelling degree of the aerogels is higher at neutral pH and the swelling degree increases firstly and then decrease upon increasing the NFC and dialdehyde starch contents.The results of drug release show that the highest loading ratio of 5-fluorouracil was 37.8%.The maximum sustained release time of the aerogel was 12 h in intestinal environment.The drug release kinetics was fitted to Korsmeyer-Peppas model,and drug release was dominated by diffusion.