Thermo‐Reversible Hydrogels Based on Poly(N,N‐diethylacrylamide)‐block‐poly(acrylic acid)‐block‐poly(N,N‐diethylacrylamide) Double Hydrophilic Triblock Copolymer

Summary: A novel double hydrophilic poly(N,N‐diethylacrylamide)‐poly(acrylic acid)‐poly(N,N‐diethylacrylamide) (PDEAAm‐PAA‐PDEAAm) triblock copolymer was synthesized by sequential anionic polymerization and modification of the poly(tert‐butyl acrylate) middle block by selective hydrolysis and neutralization to its ionic functions. Due to the pH‐sensitivity of the PAA central block and the thermo‐sensitivity of the PDEAAm end‐blocks, it exhibits responsive behavior in aqueous media. At low temperatures and high pH, it is molecularly dissolved while at temperatures above the LCST of the PDEAAm end‐blocks, a sol–gel transition was observed which should be ascribed to the formation of a three‐dimensional transient network comprising PDEAAm hydrophobic physical crosslinks interconnected by PAA negatively charged elastic chains. The sol–gel transition and the rheological properties of the physical gel are strongly influenced by the presence of salt.

Temperature induced sol–gel transition in PDEAAm‐PAA‐PDEAAm aqueous solutions.