Dual Photo/Thermo-Responsive Polypeptoids

A series of polypeptoids with dual photo/thermo-responsiveness were prepared by incorporating both azobenzene (Azo) group and oligo(ethylene glycol) (OEG) segment into the side chains. Firstly, the N -substituted- N -carboxyanhydride (NNCA) monomers with different Azo and OEG groups were synthesized, and then a single NNCA ring-openning polymerization was performed to afford dual-responsive polypeptoids without any post-polymerization modification. The ultra-violet/visible (UV/Vis) photo-responsive behaviors of the polypeptoids were achieved by cis-trans photoisomerization of the Azo group and confirmed by both 1 H-NMR and UV/Vis spectroscopy. The thermo-responsive behaviors were realized by both OEG segment and Azo group and confirmed by UV/Vis spectroscopy and dynamic light scattering. This work demonstrated the synthetic pathway for dual responsive polypeptoids using NNCA monomers with two responsive groups and revealed the potential of polypeptoids as smart materials that could respond to different environmental stimuli.