Association Behavior between End-Functionalized Block Copolymers PEO-PPO-PEO and Poly(acrylic acid)

The end groups of ABA‐triblock copolymers HO–PEO–PPO–PEO–OH, (PEO – poly(ethylene oxide), PPO – poly(propylene oxide)), have been modified with ammonia, ethylene diamine and linear polyethylenimine (LPEI) by substitution of the α,ω‐ditosyl ester of the triblock copolymer (TsO–PEO–PPO–PEO–OTs) with amines, or by the hydrolysis of the corresponding poly(2‐methyl‐2‐oxazoline) (PMeOx) containing ABCBA block copolymers. The latter block copolymer structures have been obtained by the polymerization of MeOx using TsO–PEO–PPO–PEO–OTs as a macro‐initiator. Adding poly(acrylic acid) (PAA) to these (poly)amine terminated block copolymers leads to the formation of networks through a combination of PAA–PEO hydrogen bonding and PAA–(poly)amine acid‐base reaction. Depending on the number of amino groups at both chain ends of the block copolymer, the corresponding complexes behave as liquids, gels or precipitates. Introduction of as little as 1–5 wt.‐% block copolymers H2N–PEO–PPO–PEO–NH2 or H2NCH2CH2NH–PEO–PPO–PEO–NHCH2CH2NH2 to the system of HO–PEO–PPO–PEO–OH/PAA leads to viscous liquids with strong shear‐thickening behavior. Reversible gel formation via the ternary PAA/HO–PEO–PPO–PEO–OH/H2N–PEO–PPO–PEO–NH2 system under shear conditions.