Preparation And Application Of Coordination Polyelectrolyte Complex Coacervate Materials

Complex coacervates are soft material structures formed by complexing oppositely charged macromolecules such as proteins,polymers,and nucleotides.It is ubiquitous in natural and life systems.Utilizing functional polyelectrolytes or biomacromolecules to control the preparation of new kind of complex coacervates,which is a hot research direction in the field of polymer materials and soft materials in recent years.Two bis-armed and tri-armed ligands of pyridine dicarboxylic acid were designed and synthesized,and a series of supramolecular coordination polyelectrolytes were prepared by coordination with different metals.Thanks to the adjustable structure and properties of supramolecular polymers,this paper constructs a variety of polyelectrolytic coacervate materials with different structures and functions,which achieves the stability improvement,mechanical properties enhancement and multi-functionality of such materials,laying the foundation for subsequent applications.Finally,in this paper,novel complex coacervate microdroplets were prepared by complex coacervate between peptide and ferricyanide/ferrocyanide.The formation and dissolution of microdroplets can be controlled by redox reaction.It laid the foundation for its application in simulating protocells and developing new bioreactors.The main contents are as follows:(1)The double-headed(L1)and tri-headed ligands(L3)of the dipicolinic acid were designed and synthesized.It forms a polyanion with different structure by coordination with the transition metal and further assembles the polyelectrolyte micelles with the polycation-neutral block polymer.The introduction of ligand L3 improves the cross-linking density of the complex coacervate core and makes the salt stability of the complex coacervate core micelles significantly improved.The cross-link density and salt stability can be simply controlled by varying the stoichiometric ratio of the two ligands.The presented strategy is generally applicable to transition metal ions.For example,Zn-L2-L3,Ni-L2-L3 and Fe-L2-L3micelles were all found show tunable response and enhanced stability against salt.(2)Based on the above work,paramagnetic manganese ions(Mn2+)were selected as coordination ions to prepare complex coacervate core micelles,the MRI relaxation ability of micelles was studied.The morphology of micelles was characterized by dynamic light scattering and cryo-electron microscopy.Studies have shown that the introduction of the ligand(L3)as coordination cross-linking not only improves the salt stability of the micelle,but we are surprised that the longitudinal relaxation rate T1 is also significantly improved.The Mn-L3 micelles feature a very high relaxivity(10.8 mM-1s-1),and strong contrast enhancement in a T1-weighted in vivo MRI test.The mechanism of L3’s improvement on the longitudinal relaxation rate of micelles was investigated by UV spectroscopy of the Fe-L2-L3 micellar system.(3)Developing an effective strategy to fabricate a multifunctional robust luminescent hydrogel via the ionic coacervation of an anionic dynamic lanthanide coordination polymer with a cationic polyelectrolyte.The hydrogel has the characteristics of high modulus,plasticity,self-healing,and recyclability,and may be regarded as a new kind of "luminescent plastic".Owing to its force-induced plastic deformation,long fibers can be directly drawn form the hydrogel reservoir at room temperature.Moreover,the dynamic nature of such a physical polymer network leadw to multiple responses to various stimuli,such as temperature,salt and sonication.The studies described herein not only enable the processability of luminescent hydrogels but also provide a new strategy to prepare stimuli-responsive and self-healing lanthanide-based hydrogels as sustainable and smart materials.(4)The microdroplets are prepared by complex coacervate of inorganic polyvalent small molecule potassium ferricyanide/potassium ferrocyanide and a cationic polypeptide.Salt titration is used to determine the phase diagram of the peptide ferrocyanide microdroplets and to control the formation and dissolution of droplets by redox reaction.As all steps of the coacervate droplet life cycle,including nucleation,coarsening,and dissolution,occur under the same reaction conditions,the cycle can be repeated multiple times.Our results suggest that peptide-ferrocyanide microdroplets can be considered as a new type of protocell model that could be used to develop novel bioreactors and plausible pathways to the prebiotic organization before the emergence of lipid-based compartmentalization on the early Earth.