Injectable hydrogels with improved mechanical property based on electrostatic associations

Abstract

The mechanical properties of injectable and thermo-responsive ABC triblock copolymer hydrogels are enhanced by the electrostatic attraction between oppositely charged moieties introduced in the mid-blocks. The triblock copolymers are composed of biodegradable poly(epsilon-caprolactone) (PCL), hydrophilic cationic or anionic mid-block, and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) with quadruple hydrogen bonding units. PCL blocks and PNIPAM blocks form separate micellar cores, and the mid-blocks make a bridge between the cores. The dynamic nature and thermo-responsiveness of the PNIPAM block primarily endow the temperature- and shear-responsiveness to the hydrogel, and therefore make the hydrogel injectable and self-healable. In particular, the electrostatic attraction introduced in the mid-blocks results in the enhanced mechanical properties of the hydrogels. The dual-responsive hydrogel with the improved moduli will aid in designing soft materials in the field of biological and biomedical applications.