| Nowadays,with the fossil resources reduction and their negative impacts on the environment,there is growing demand for development of renewable and biodegradable biomass or biomaterials as substitutes for petroleum-derived synthetic polymers.Biomass resource is the most abundant resource in earth,which have the potential to replace petroleum-derived synthetic polymers.Cellulose as one of the most abundant biomass resource,which exhibits unique physicochemical properties,such as high mechanical strength,biodegradable,renewable and biocompatible.In addition,cellulose offers broad chemical modification susceptibility due to the presence of a large amount of hydroxyl groups.Chemical modification of cellulose is one of the most promising means for the production of value-added products.Moreover,the modified cellulose derivatives have displayed excellent functional properties for applications in various fieldsRegenerated cellulose films with enhanced mechanical property were prepared via incorporating different plasticizers(sorbitol,glycerol,carboxymethyl cellulose)using ionic liquid 1-allyl-3-methylimidazolium chloride(AmimCl)as the solvent.The results showed that the cellulose films exhibited a homogeneous and smooth surface structure.It was noted that the thermal stability of the regenerated cellulose film plasticized by glycerol was increased compared with other regenerated cellulose films.Furthermore,the incorporation of plasticizers dramatically strengthened the tensile strength and improved the hydrophobicity of cellulose films,as compared to the control sampleWith the cotton linter as the raw materials,we present a facile process for the preparation of lightweight and high adsorptive cellulose beads modified by acetylation,benzoylation and tosylation in an ionic liquid(AmimCl),respectively.To evaluate the potential application as adsorbent for wastewater treatment,the adsorption of organic dyes was also investigated.The results indicated that the modified cellulose beads displayed a homogeneous and porous network structure.In comparison,the modified cellulose samples exhibited higher adsorption capacity,which showed that the introduced group played an important roles in the improvement of the adsorption capacity.The adsorption kinetics experiments indicated that the relevant data could be satisfactorily fitted by the Langmuir model equation.In addition,the modified cellulose beads could be easily recycled,offering outstanding cycling capability with more than 94%of the removal efficiency for organic dyes after 3 cycles.In the present study,we describe a novel one-step method to prepare water-soluble cellulose acetate(WSCA)with higher degree of polymerization values(DP=650-680)by in situ activation of carboxyl group in ionic liquid.First of all,cellulose was dissolved in 1-ethyl-3-methylimidazolium acetate(EmimAc)and reacted with dichloroacetyl chloride(C12AcCl)in order to make cellulose dichloroacetate.Under various conditions,a series of water soluble products were produced.Elemental analysis and NMR results confirmed that they were cellulose acetate with DS(degree of substitution)values in the range from 0.30 to 0.63.NMR studies demonstrated that Cl2AcCl reacted with acetate anion of EmimAc producing a mixed anhydride that acetylated cellulose.Other acylating reagents such as benzoyl chloride,chloroacetyl chloride can also work similarly.2D NMR characterization suggested that 6-mono-O-acetyl moiety,3,6-di-O-acetylcellulose and 2,6-di-O-acetyl cellulose were all synthesized and the reactivity of hydroxyl groups in anhydro-glucose units was in the order C-6>C-3>C-2.Water-soluble cellulose acetate(WSCA),one of the most important cellulose derivatives,possesses biocompatibility,biodegradability properties and broad chemical modifying capacities.In this work,highly polymerized WSCA was synthesized and firstly used as the cross-linker to fabricate highly ductile,tough and resilient WSCA-polyacrylamide(PAM)composite hydrogels.The results showed that the WSCA/PAM nanocomposite hydrogels exhibited extraordinary toughness and ductility with a tensile strength of 297 kPa and elongation at break of about 4020%.The enhancement of mechanical properties and stretchability were due to the synergistic effect from the hydrogen bonding and physical interfacial adhesion between the composite matrix.Under stretching conditions,hydrogen bonds between WSCA chains and PAM could dynamically break and rearrange to dissipate energy.At the same time,the wound filaments in WSCA embedded in PAM matrix or penetrated between layers became unfolded or fractured to dissipate energy and maintained the conformation of hydrogels.It is envisioned that the introduction of WSCA into polymeric matrix would generate a facile method to fabricate multiple layered hybrid hydrogel network and widen broad the WSCA applications in the preparation of high performance supramolecular systems.Biopolymer nanocomposite films were prepared by adding exfoliated reduced graphene oxide(rGO)sheet into water-soluble cellulose acetate(WSCA)at low and high rGO loadings.As firstly evidenced by viscosity of film-forming solutions,microscopic observations and infrared spectroscopy measurements,it was found that the rGO form a three-dimensional network throughout strong interfacial hydrogen interactions with WSCA,confirming that the rGO were well dispersed within the WSCA,even at high rGO content,owing to the presence of several multifunctional groups on both phases which ensured the high compatibility between them.The topography of as prepared films was characterized by SEM measurements showing that the films have a smooth surface for all range of rGO contents.In addition,the thermal stability and tensile properties of rGO/WSCA composite films were gradually increased with increasing of rGO contents.Furthermore,all the composite films possessed excellent electrical conductivity.The high performances of these films can be expected to have potential in biomaterials or packaging materials applications. |
PDF Full Text Request