Preparation, Characterization And Application Of Soft Materials Inspired By The Marine Organisms

With the development of technology,there is a more and more urgent need of new materials for human lifes.The abundent biological resources in the ocean have inspired researchers to design new materials.Among the plenty of marine-inspired materials,the soft materials including hydrogels and coacervates are one of the most significant ones.At current stage,for this kind of materials,there are still some drawbacks from the aspect of cohesion and biocompatibility.Aiming at the shortcoming of poor cohesion,in this paper,inspired by the composite materials,we successfully prepared an oyster-inspired organic-inorganic hybrid adhesive which consisted of amorphous calcium carbonate?ACC?and polyacrylic acid?PAA?,as well as cellulose reinforced mussel-inspired adhesives.The as-prepared adhesives showed excellent adhesion performance under dry and wet conditions,which was demonstrated by the lap shear testings.To improve the biocompatibility of the adhesives,bovine serum albumin?BSA?was employed to physically crosslink the catechol modified hyaluronic acid?HA?.All the components of the acquired coacervate can be extracted from organisms,which lays a foundation for further biomedical application.The summarized results of this thesis are listed as follows:1.An oyster-inspired biomineralized hydrogel adhesive was prepared by in-situ crosslinking of high molecular weight(Mw?250 000 g mol^-1)PAA with amorphous calcium carbonate?ACC?nanoparticles.This hydrogel adhesive showed excellent adhesion properties to various substrates such as aluminum,wood,and polyethylene.Among them,the adhesive strength to the aluminum substrate could reach 5 MPa and 250 kPa under the dry curing condition and wet curing condition respectively.After drying in air,the as-prepared hydrogel could form a highly transparent film.The UV transmittance test showed that the hydrogel exhibited a transmittance of more than 90%in the visible wavelength range?300 nm-800 nm?.The adhesive could be potentially served as an optical clear adhesive.2.The ACC/PAA hydrogel was doped with a series of negatively charged water-soluble nanoparticles,including Cu₂O nanoparticles,Fe3O4 nanoparticles,Laponite,and gold nanoparticles,and the interior structure of the hydrogel was subjected to a secondary cross-linking to achieve a better adhesion strength.Rheological tests showed that after the doping of negatively charged nanoparticles,both the elastic modulus?G"?and the viscosity modulus?G"?of the hydrogel were greatly improved.At the same time,the nano-indentation tests of the dried hydrogel film were performed.The results showed that the introduction of nanoparticles successfully increased the Young's modulus of the film by 28-3 8%.Through the introduction of nanoparticles,the enhancement of the crosslinking of the internal structure of the hydrogel could be successfully achieved,further improving the cohesion of the hydrogel.Especially,after the introduction of Cu₂O nanoparticles,the adhesion strength to the aluminum plate was increased by 60%under dry conditions compared with the undoped hydrogel.3.To overcome the insufficient cohesive strength of the original DOPA modified polyacrylic acid-zinc(PAA-DOPA/Zn²⁺)adhesive coacervate,cellulose fibers?CFs?and cellulose nanocrystal?CNCs?were introduced to the coacervate as reinforcing materials,which led to a great enhancement of the adhesive performance.The effect of lengths of cellulose fiber?25 ?m,90 ?m,and 180 ?m?and the amount of reinforcing material?2.5-20 wt%,w/w?on the adhesive properties were studied in detail.After optimizing a series of conditions,the adhesive strength of the reinforced adhesive coacervate on the aluminum substrate can reach 10 MPa under dry curing conditions,1.9 MPa under wet conditions.These results were superior to most of commercial adhesives.4.DOPA-modified hyaluronic acid?HA-DOPA?was successfully prepared through an amidation reaction in the aqueous solution.The grafting ratio of DOPA was about 15%.HA-DOPA and bovine serum albumin?BSA?were dissolved in aqueous solution at a certain weight ratio.When the pH of the solution was lower than the isoelectric point of BSA,BSA and HA-DOPA could be combined through electrostatic interaction to obtain viscous adhesive coacervate.The coacervate showed excellent dry adhesion as well as underwater adhesion.The adhesive strength to aluminum plates under dry curing conditions can reach about 5 MPa.The underwater adhesive strength on porcine skin can reach about 25 kPa.Different coacervate could be prepared by changing the ionic strength of the mixed precursor solution.Last but not least,the coacervate shows excellent self-healing properties.Combined with the biocompatibility,this adhesive coacervate has potential applications in the biomedical field.5.A dual physical-crosslinked hydrogel,which consisted of PVA crystallite crosslinked network and hyaluronic acid-Fe³⁺ electrostatic network,was successfully prepared through a simple method.The PVA crystals were formed by freeze-thaw-annealing treatment without adding any toxic initiator or crosslinking agent.The effect of preparation parameters of hydrogel on the mechanical strength,including the mass ratio of PVA to HA,annealing temperature,and the Fe³⁺ concentration,were studied in detail.By optimizing the preparation process,the elastic modulus of hydrogel could reach 4.9 MPa and the toughness can reach 19.6 MJ/m³.Furthermore,the viscous precursor solution with viscoelastic properties can be processed as ink for 3D printing,so that hydrogels could be processed to various patterns through a 3D printer.The design strategy provided a simple avenue for the fabrication of tough hydrogels featuring good processability without chemical polymerization.