Controllable fabrication of novel pH-, thermo-, and light-responsive supramolecular dendronized copolymers with dual self-assembly behavior

Abstract

Novel tri-stimulus responsive supramolecular dendronized copolymers are prepared through the self-assembly of imine bonds, exhibiting fast and fully reversible phase transitions and trans–cis isomerization in alkaline solutions. The lower critical solution temperature (LCST) is controlled with the aldehyde-to-amino molar ratio, and mostly decreases after UV irradiation. As the pH increases, the LCST has an inflection point caused by two different self-assembly behaviors. The aldehyde and amino monomers are assembled by H-bonds in acids, but by dynamic imine bonds in bases. The copolymer concentration plays an essential role in affecting the LCST. The LCST increases with the aldehyde content when the concentration is 5.0 mg mL⁻¹ and has an inflection point with the aldehyde content when the concentration is 1.0 mg mL⁻¹. The tri-stimuli-responsive copolymers have three advantages: (1) feasible control via pH-adjusting aldehyde–amino bonds, (2) controllable synthesis, and (3) narrow, tunable phase transition temperature by pH, light and the molar ratio.