Facile tuning of hydrogel properties by manipulating cationic-aromatic monomer sequences

Copolymer hydrogels formed from cationic and aromatic monomers with identical monomer compositions but different average sequences were synthesized by free-radical copolymerization in various solvents. We found that hydrogels with one-component-rich segments are mechanically stronger than those with adjacent-rich monomer sequences in water, while hydrogels with a rich cation-π adjacent sequence showed excellent mechanical strength and underwater adhesion in saltwater (0.7 M NaCl). The molecular mechanisms for these behaviors are discussed in terms of polymer structures. This work reveals the importance of monomeric sequences in determining hydrogel properties and provides a facile approach to develop hydrogels with different properties but the same monomer composition.