Functional Biopolysaccharide-based Nanocomposites Prepared Based On Mussel Biomimetic

The rapid consumption of petroleum resources and white pollution is expected to be solved by developing biomass materials.As one of the typical representatives of biomass polymers,biopolysaccharides have the advantages of abundant sources,renewable,good biocompatibility and biodegradability.In order to overcome the shortcomings of pure polysaccharide materials,such as brittleness,poor water resistance and single performance,the construction of functional nanocomposites is an effective solution.Biopolysaccharide-based nanocomposites are a combination of biopolysaccharides matrix and nanoscale inorganic/organic reinforcing materials,which can not only enhance mechanical properties,but also derive unique functional properties.In the process of preparing nano-composite materials,good distribution of nano-filler and effective energy dissipation interface are the key to achieve good performance.Inspired by the supramolecular structure of mussel adhesion proteins and their catechol side chains with strong adhesion ability by generating multiple non-covalent and covalent interactions,the use of plant-derived catechol derivatives for surface modification of fillers can promote the dispersion of fillers and provide bridging between the filler and the matrix,thereby enhancing the internal network of nanocomposites.Active end groups derived from catechol’s also provide efficient reaction sites for the introduction of other functional molecules.Based on this,this paper uses bio polysaccharide polymer as the base substance,nanocellulose and nano barium titanate as reinforcing fillers.The mussel biomimetic strategy was used to modify the nanofillers and design the interface structure to construct multiple bonding to prepare multifunctional chitosan film and multifunctional sodium alginate-polyvinyl alcohol conductive hydrogel strain sensor,which provided new ideas and methods for expanding the application of bio polysaccharide materials.The specific research works are as follows:(1)Nanocellulose based on mussel biomimetic modification was used to prepare functional chitosan composite films.Cellulose nanofiber hybrids functionalized by sodium lignosulfonate were prepared by supramolecular interaction,combined with quaternary ammonium salt hyperbranched polyamide,and introduced into chitosan polymers to construct supramolecular and hyperbranched crosslinking networks to enhance the properties of chitosan composites.The EDS element distribution image showed that quaternary ammonium salt hyperbranched polyamide and functionalized cellulose nanofibers were uniformly distributed in the chitosan matrix.The synergistic effect of flexible hyperbranched network and rigid functionalized cellulose nanofibers significantly increased the toughness of chitosan composite films to 19.1 MJ/m~3,which is 170.2%higher than that of unmodified chitosan films.The significant decrease in UV transmittance also proved that the modified chitosan composite films have excellent UV shielding ability.In addition,antibacterial experiments showed that cationic quaternary ammonium salt hyperbranched polyamide with a large number of positive charges could significantly improve the antibacterial performance of chitosan composite films against Escherichia coli and Staphylococcus aureus.(2)Nanocellulose/zinc oxide quantum dots based on mussel biomimetic modification are used to prepare functional chitosan composite films.By utilizing the multifunctional reaction characteristics of abundant aldehyde groups and polyphenol hydroxyl groups on the protocatechuic molecules,the layer of protocatechuic aldehyde was coated on the surface of cellulose nanofibers and zinc oxide quantum dots,and then introduced into the chitosan polymer with hyperbranched polyamide at the same time.The chitosan-based nanocomposite films enhanced by catechol chemistry,hyperbranched crosslinking and metal coordination were prepared.The chemical modification of mussel biomimetic significantly increased the interaction force between the nano-reinforced material and the chitosan matrix,and the results showed that the elongation at break and tensile strength of the functional chitosan composite films were increased at the same time,with the maximum values of 42.5%and 45.3 MPa,respectively.The surface hydrophobicity,thermal stability and UV shielding properties of chitosan composite films were also significantly improved.In addition,the introduction of functional zinc oxide quantum dots and protocatechualdehyde containing polyphenol groups significantly improved the antibacterial properties of chitosan composite films against Escherichia coli and Staphylococcus aureus.(3)Nano-barium titanate based on mussel biomimetic modification was used to prepare multifunctional sodium alginate-polyvinyl alcohol conductive hydrogel.Using nano-barium titanate as the construction base,tannin coated nano-barium titanate complex was prepared by mussel biomimetic chemistry,which was introduced into sodium alginate-polyvinyl alcohol crosslinked by borax,and multifunctional biopolysaccharide-based conductive flexible hydrogels were prepared by a simple one-pot method.The results showed that the crosslinking network composed of dynamic reversible borate ester bonds and tannin mediated interactions(including hydrogen bonds and coordination bonds)made the hydrogel have excellent self-healing ability and significantly improved mechanical properties,and the maximum strength and toughness of the hydrogel were 52.3 KPa and 587.1 KJ/m~3,respectively.Meanwhile,the combination of the abundant active functional catechol groups in the tannin with the significantly improved cohesion of the hydrogel enabled the hydrogel to exhibit strong and residue-free adhesion to a variety of inorganic and organic materials.The adhesion strength to wood was up to 67.5 k Pa.The combination of high toughness,conductivity,adhesion and self-healing properties of modified hydrogels enabled stable real-time monitoring of human movement when it was applied to wearable strain sensors.