| In recent years,with the introduction of the concept of green economy and people's awareness of environmental protection,the research and application of biobased materials have been widely valued.Among them,cellulose is the most widely used,due to a wide range of sources and the largest reserves.For a long time,the cellulose material is mainly used in the form of cellulose derivatives and additives.Thanks for the progress of the cellulose dissolving technology,it is possible to prepare various forms of materials with regenerated cellulose?RC?materials as a matrix.In order to improve the performance of materials,to prepare functional materials,based on the structural characteristics of regenerated cellulose molecular chains and the structural features of a variety of materials such as fiber,films and aerogel,a series of high performance and functional materials have been constructedIn this paper,the regenerated cellulose fiims/membranes with porous network structure were used as the research object.By using the hydrogen bonding between hydroxyl groups in the macromolecules of cellulose and organic molecules with hydroxyl groups and ester groups;the promoting effect of hydroxyl groups on epoxy curing,and the reaction activity of hydroxyl groups,such as the condensation reaction with the silicon hydroxyl group,the oxidation reaction under TEMPO,and the acetal reaction,a series of novel regenerated cellulosic films/membranes were constructed and prepared by using physical and chemical methods respectively.Firstly,all cellulose composite films with good mechanical properties and transparency were prepared;RC and epoxy soybean oil blending films with higher toughness and hydrophobicity were also prepared;moreover,aminated RC membranes with highly catalytic activity were constructed and prepared;finally,two-sided surface oxidized cellulose membranes modified with PEI were perpared.Specific research content is divided into the following parts:?1?All cellulose composites based on cellulose diacetate and nanofibrillated cellulose prepared by alkali treatmentCellulose diacetate?CDA?composite films were synthesized by incorporation of nanofibrillated celluloses?NFCs?,using a casting/evaporation technique.Fourier transform infrared?FTIR?spectroscopy,X-ray diffraction?XRD?,and scanning electron microscopy?SEM?measurements indicated the presence of interaction and certain compatibility between CDA and NFCs.The CDA and NFCs were converted to cellulose II by an alkaline treatment which resulted in the formation of all cellulose composite?ACC?films,as indicated by the FTIR and XRD measurements.Significant changes were observed in their structural,thermal,mechanical,and optical transparency properties after alkali treatment.The SEM images revealed the excellent compatibility among the constituents of the ACC films.At the content of 15 wt%of NFCs,the tensile strength,Young‘s modulus,and strain at break of the ACC films were increased to 102.3 MPa,5.8 GPa,14.7%respectively.This work provides a promising pathway for manufacturing high performance ACC materials.?2?Preparation and properties of hydrophobic regenerated cellulose/ESO composite films with high toughnessBased on the preparation of regenerated cellulose films,the combination of RC and epoxy-soybean oil?ESO?was realized by using the impregnating process,and the RC/ESO composite films were prepared by heat curing.The curing behavior of RC/ESO composites showed that as maleic anhydride is used as curing agent,when the molar ratio of epoxy equivalent to anhydride equivalent is 1?1,in theory,ESO is considered to be completely cured.Further research indicates that RC can reduce ESO apparent curing activation energy and promote ESO curing.The mechanical property test showed that when the ESO with high curing ratio,the introduction of ESO caused the mechanical properties of the membrane to decline.Further research indicates that RC can reduce ESO curing apparent activation energy and promote ESO curing.Through the regulation of ESO curing degree,the cured ESO resin and the interface of the two phases could be fractured or damaged under stress,resulting in the consumption of a large number of fracture energy.While uncured ESO played a plasticizing effect.A composite film with good comprehensive mechanical properties could be obtained.As the molar ratio of epoxy equivalent to anhydride equivalent is 1?0.7,the tensile strength,Young's modulus and elongation at break of the composite film were 65.7 MPa,1.2 GPa and 16.3%,respectively.The water contact angle tests and the water absorption tests showed that the RC/ESO composite films prepared in this experiment had good hydrophobicity.?3?Peparation,structure and properties of amino-functionalized cellulose membrane with high catalytic activityThe modification of regenerated cellulose?RC?membranes was carried out by using silane coupling agents presenting primary and secondary amino-groups.The grafting of the amino groups onto the modified cellulose molecule was confirmed by X-ray photoelectron spectroscopies and 13C nuclear magnetic resonance spectroscopic analyses.The crystallinity of the cellulose membranes?CM?decreased after chemical modification as indicated by the X-ray diffraction results.SEM characterization showed that the pore size of the porous surface of the modified regenerated cellulose membrane was reduced and the internal porous structure had disappeared?within the experimental size range?,by the control of the heating temperature and time during the modification process,The water contact angle measurements showed that the silane coupling treatment enhanced the hydrophobicity of the obtained materials.Then the catalytic properties of two types of modified membranes were studied in a batch process and a pervaporation catalytic membrane reactor,by evaluating their catalytic performance in a Knoevenagel condensation.Therefore,functional CM that prepared in this paper represented a promising material in the field of industrial catalysis.?4?Two-sided surface oxidized cellulose membranes modified with PEI:preparation,characterization and application for dyes removalPorous regenerated cellulose?RC?membranes were prepared with cotton linter pulp as a raw material.These membranes were first oxidized on both sides by a modified?2,2,6,6-tetramethylpiperidin-1-yl?oxyl?TEMPO?oxidation system using a controlled oxidation reaction technique.Then,the oxidized RC membranes were functionalized with polyethylenimine?PEI?via the glutaraldehyde crosslinking method to obtain bifunctional?carboxyl and amino?porous RC membranes,as revealed by Fourier transform infrared spectroscopy?FT-IR?,elemental analysis and zeta potential measurements.The scanning electron microscopy?SEM?and the tests of the mechanical properties and permeability characteristics of modified RC membranes demonstrated that the porous structure and certain mechanical properties could be retained.The adsorption performance of the modified membranes towards dyes was subsequently investigated.The modified membranes displayed good adsorption capacities,rapid adsorption equilibrium and removal efficiencies towards both anionic?xylenol orange?XO??and cationic?methylene blue?MB??dyes.The maximum adsorption capacities of XO and MB reached 403 mg·g-1 and 139 mg·g-1,respectively,making them suitable bioadsorbents for wastewater treatment.To increase the added value of cellulose based materials and expand its application scope,in this paper,a series of high performance and functional regenerated cellulose films/membranes could be constructed by using the porous network structure of the regenerated cellulose films/membranes and the reaction activity of the hydroxyl groups in the cellulose macromolecule,and through the adjustment of the influence factors such as temperature. |
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