Study On Preparation And Properties Of Catechol-based Polymers

Catechols are phenol derivatives with two neighboring(ortho-) hydroxyl groups, which are found in nature and have multifunctions. They cantake part in a remarkably broad scope of biochemical processes. 3,4-Dihydroxyphenylalanine(DOPA) is a kind of typical catechol derivatives. Accourding to the versatility of chemical and physico-chemical properties of DOPA, catechol-based polymers were prepared for varied technologically applications.In order to obtain precise structure of PDOPA polyester, N-(ethoxycarbonyl)phthalimide(N-Phth) and acetyl chloride were used to protect amine group and hydroxyl groups in DOPA, respectively, before polymerization. Then, PDOPA polyester was prepared by thermal polycondensation and deprotection of amine group. The structures of N-Phth-DOPA, ace-N-Phth-DOPA, P(N-Phth-DOPA) and PDOPA were confirmed by FT-IR and 1H NMR. The molecular weight and molecular weight distribution of PDOPA were characterized by GPC. Thermal stability of PDOPA was measured by DSC. Degradation of PDOPA was analyzed by GPC, HPLC and MS, and these results suggested that PDOPA had well degradability with a high speed and the degraded products were original DOPA and its dimer. The MTT method was used to confirm the cell compatibility of PDOPA through a cell adhesion test, and the result suggested that PDOPA polyester had well biocompatibility.DOPA was employed to modify PVA by esterification interaction, and the grafting agree of DOPA was controlled by the DOPA composition. The structure of PVA-DOPA was confirmed by FT-IR, 1H NMR and UV-vis. DOPA has been confirmed to have a strong binding affinity to diverse kinds of metals or metal oxides through the formation of hydrogen bonding and metal coordination. Non-covalent PVA-DOPA hydrogels and PVA-DOPA metal complexation hydrogels were prepared from PVA-DOPA and complexation with Fe3+ and other metal ions. Rheology analysis was carried out to test mechanical properties of the gels and to monitor qualitatively the self-healing process. Moreover, the coordination interaction between PVA-DOPA and metal ions was dependently on p H. Mono-, bis- and tris-complexes were found to dominate in solutions in the p H ranges 1-5, 5-10.8, and 10.8-12, respectively. By adjusting p H, the coordination interaction could be controlled and reversible.PVA-DOPA was mixed into PVA to prepared PVA/PVA-DOPA film. Accourding to the redox activity and adhesion ability of DOPA, silver nanoparticles were loaded on PVA/PVA-DOPA films. UV-visible spectrum of the PVA-DOPA/Ag+ mixture showed the presence of an additional broad absorption at λmax=415nm, which assigned to the special adsorption peak of the oxidized quinone groups. This result indicated the occurring oxidation-reduction reaction of DOPA and the formation of Ag0 nanoparticles SEM and TEM images of the PVA/PVA-DOPA/Ag0 films showed that the Ag0 nanoparticles were formed on the surface of the PVA/PVA-DOPA films. The amount of the silver nanoparticles loaded on the PVA/PVA-DOPA films was about 18 wt%, calcluated by TGA diagrams of PVA, PVA/PVA-DOPA, and PVA/PVA-DOPA/Ag0 in N2. Antimicrobial assessment showed that the prepared PVA/PVA-DOPA/Ag0 film has a high antibacterial activity.