Study of the temperature/HCO3- response mechanism of hyperbranched poly(bis-acrylamide)s

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 HCO 3 - . 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, 1 H 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 HCO 3 - .