Preparation and properties of catechol-based waterborne polyurethane based on thiol-ene click chemistry reaction

A highly effective way is found to incorporate dopamine (DA) containing catechol groups into waterborne polyurethane backbone. Firstly, prepolymer polyurethane (PPU) containing sulfydryl were created through stepwise polymerization in which isophorone diisocyanate (IPDI) was as hard segment, polyethylene glycol (PEG)(Mn=600) was as soft segment, dimethylolpropionic acid (DMPA) was as hydrophilic monomer and monothioglycerol (MON) was as chain extender. Then a series of catechol-based waterborne polyurethanes (MON-PPU-DOMA) was obtained by introducing methacrylamide dopamine (DOMA) into polyurethane backbone via thiol-ene click chemistry. FT-IR, 1H-NMR and UV-vis spectra showed that DOMA was successfully incorporated into polyurethane backbone. TG and mechanical properties testing results indicated that the heat resistance and tensile strength of MON-PPU-DOMA films were obviously improved. Moreover, MON-PPUDOMA/Fe3+ complex was obtained by MON-PPU-DOMA with Fe3+ triggered via adjusting pH and their color and state change was apparent, which also made it possible for MON-PPU-DOMA/Fe3+ to become an injection adhesion material. MON-PPU-DOMA was used to bonding different substrates. The results showed that the lap shear strength of MON-PPU-DOMA to iron sheet was 3.23 MPa, which was obviously bigger than that of MONPPU without DOMA. The introduction of DOMA can significantly improve adhesive ability of polyurethane. Because it is difficult to dissolve in DMF, MON-PPU-DOMA emulsion has the potential of being an environmentally friendly coating on the surface of iron substrates.