Fig. 3. (A) Synthesis of the DNA chains undergoing pH-induced hydrogel formation and dissociation. Formation of the hydrogel proceeds at pH = 7.0 using the strand (7) as activator for the formation of Hoogsteen triplex bridges between the (5)-modified chains. At pH = 10.0 the triplex bridging units dissociate to form the separated polymer chains. (B) Images of the polymer hydrogel formed at pH = 7.0 and the polymer solution generated at pH = 10.0. (C) Rheology studies following the pH-switchable storage moduli, G′, and loss moduli, G′′, upon switching the TA·T triplex-crosslinked system between the pH values 10.0 and 7.0. (D) Time-dependent feature of the G′ modulus corresponding to systems composed of: (a) the (6)/(7) triplex crosslinked hydrogel. (b) The polymer chains (6) treated with (7a) (two base mismatches). (c) The polymer chains (6) treated with (7b) (three base mismatches). (d) The polymer chains (6) treated with (7c) (four base mismatches).