The aqueous solution of hyperbranched poly(bis-acrylamide)s (HPEAMs) prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization has a lower critical solution temperature (LCST), which can also respond to HCO3-. However, the phase change mechanism of HPEAMs has not yet been proven. In this paper, N-(2-propionamidoethyl)acrylamide was designed as a monomer and chain transfer agent (CTA), and the corresponding linear polymers, hyperbranched polymers and hyperbranched copolymers were further prepared. Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, ultraviolet‒visible spectroscopy, dynamic light scattering and zeta potential were employed to characterize the structure and phase transition behavior. The results confirmed that the bis-acrylamide unit is hydrophilic and the CTA unit is hydrophobic. The hydrophilic-hydrophobic balance system constructed by the unit of bis-acrylamide and CTA endowed the hyperbranched polybisacrylamide with temperature-responsive behavior, and the carboxyl group in the CTA structural unit is the responsive group that makes it possible to tune the LCST in the presence of HCO3-.
The aqueous solution of hyperbranched poly(bis-acrylamide)s (HPEAMs) prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization are of lower critical solution temperature (LCST), which also can response to HCO3-. The structure of HPEAM is characterized by the presence of carboxyl groups, thioester groups, and diamine bisacrylamide structural units. The study will reveal how they act in solution to cause these phenomena.