Hydrophobic/Hydrophilic Triblock Copolymers: Synthesis and Properties of Physically Cross-Linked Hydrogels

Abstract

Hydrophobic/hydrophilic triblock copolymers of poly(2-(N-ethylperfluorooctanesulfonamido)ethylmethyl acrylate) and poly(N,N′-dimethylacrylamide) (PD) were synthesized by sequential reversible addition–fragmentation chain transfer polymerization. Physically cross-linked hydrogels were produced by immersing compression-molded triblock copolymers into water. The copolymers and their hydrogels were characterized by differential scanning calorimetry, thermogravimetric analysis, thermal desorption-GC/MS analysis, swelling isotherms, wide- and small-angle X-ray scattering, and dynamic mechanical analysis. The equilibrium water sorption of the hydrogels depended on the length of the water-soluble polymer block (PD), and the block copolymers swelled more in water than a random copolymer of the same composition. The block copolymer hydrogels were viscoelastic, though the frequency dependence of the dynamic modulus was weak. The dynamic modulus of the block copolymer hydrogels ranged from ∼103 to 4 × 104 Pa, which was much lower than the modulus of a random copolymer hydrogel of the same composition.