Synthesis of Novel Thermo- and pH-Responsive Poly(L-lysine)-Based Copolymer and its Micellization in Water

A series of novel temperature and pH responsive block copolymers composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(L-lysine) (PLL) were synthesized. The effect of pH and the length of PLL on the lower critical solution temperature (LCST) of PNIPAM, and the self-assembly of these PLL-based copolymers induced by temperature and pH changes were investigated by the cloud point method, dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). These PNIPAM-b-PLL copolymers can self-assemble into micelle-like aggregates with PNIPAM as the hydrophobic block at acidic pH and high temperatures; and at alkaline pH and low hey can self-assemble into temperatures, particles with PLL as the hydrophobic block. The copolymers may have potential applications in biotechnological and biomedical areas as drug release carriers.