Formation Of Tunable Functional Chitosan-based Core-shell Hydrogels Through Physical Approaches

Tunable core-shell chitosan-based hydrogels are generated through self-assembly of sodium alginate(SA)toward oppositely charged water-soluble chitosan(WSC)gel beads.In order to improve the mechanical strength of the beads,well-defined polyvinyl alcohol(PVA)that obtained via RAFT polymerization and alcoholysis are blended with WSC in solution.The mixture is subjected to freezing/thawing cycles to form enhanced cores,and then the aforementioned self-assembly is performed to obtain enhanced core-shell beads.The enhanced core-shell beads are further transferred into porous ones by introducing porogen during the formation of cores and removing porogen from the core-shell beads.The structure-performance relationships of these chitosan-based hydrogels and their modulation are well investigated.The obtained results are as follows.1.Water-soluble chitosan-based core-shell hydrogels particles that contained changeable cores are prepared through self-assembly of SA onto WSC beads and the removal of cores by taking advantages of p H-responding and water-soluble properties of WSC.FTIR,TGA,SEM-EDS and fluorescence analysis results verify the structure of the formed core-shell hydrogels.The core-shell hydrogels can adsorb copper and lead ions as well as CO2.The capacity can reach 145.85mg/g.The adsorption capacity of core-shell hydrogels,Ca(II)-SA-WSC@WSC,toward heavy metal ions are greater than that of the empty-core ones.In addition,the capacity of the hydrogel particles for adsorbing CO2 is increased in the presence of Na OH.2.A mixture of well-defined PVA prepared by RAFT polymerization and alcolysis and WSC is subjected to freezing/thawing to prepare the cores.Then the self-assembly of SA onto the cores are carried to obtain core-shell hydrogels Ca(II)-SA-WSC@WSC/PVA.FTIR,TGA,EDS and DMTA analysis results confirm the structure of the samples and the improvement of mechanical strength compared to Ca(II)-SA-WSC@WSC.The storage modulus and glass transition temperatures of the hydrogels can be changed by the content and molecular weight of the PVA.The adsorption capacity of the core-shell hydrogel particles toward heavy metal ions and gases is similar to those of Ca(II)-SA-WSC@WSC.3.The enhanced core-shell hydrogels Ca(II)-SA-WSC@WSC/PVA are further transferred into porous ones through introducing and removing of Na2CO3 as porogen,which is confirmed with SEM and porosity analysis.The porosity of the core-shell hydrogels can be simply adjusted with the mount of porogen,and the adsorption capacity toward Cu(II),Pb(II)and?-amylase are varied accordingly.The particles are able to catalyze the degradation of starch.These results indicate the porous core-shell hydrogels are sorbents for heavy metal ions and suitable carrier for?-amylase.In a word,a variety of controllable core-shell hydrogels are physically generated by taking advantage of the properties of WSC,SA and PVA such water-soluble,p H-sensitive,and easily to be physically cross-lined.The cores of Ca(II)-SA-WSC@WSC can be transformed into aqueous ones or replaced with WSC/PVA.Porous Ca(II)-SA-WSC@WSC/PVA particles are easily to be obtained.These WSC-based hydrogels show the capacity to fix heavy metal ions,acidic or basic gases and?-amylase.They may be applied in the fields such as purification,separation,encapsulation and catalysis.