The present invention relates to an aqueous dispersion comprising dispersed particles comprising a polyurethane comprising at least the following building blocks derived from a) at least one organic polyisocyanate, b) at least one carboxylate group-bearing isocyanate-reactive compound, and c) at least one organic isocyanate-reactive polyol, wherein at least one of the carboxylate group-bearing compounds b) has the following structural formula O II (1) R.sub.2(R.sub.3)NCR.sub.1-COO.sup. wherein R.sub.1 is a divalent aliphatic hydrocarbon radical having from 2 to 8 carbon atoms or a divalent cycloaliphatic hydrocarbon radical having from 6 to 8 carbon atoms or a divalent aromatic hydrocarbon radical having from 6 to 8 carbon atoms, R.sub.2 and R.sub.3 are 2-hydroxypropyl.

Periodic placement of directional dynamic bonding units along a flexible polymer backbone enables the formation of large supramolecular structures during strain. These structures, which form due to the alignment of stretched backbone chains, lock the stretched chains in their elongated state due to the formation of the directional dynamic bonds. Application of an appropriate stimulus (i.e., heat or light) weakens the dynamic bonds and enables the elongated chains to retract, performing measurable work and enabling the use of these structures as polymer actuators. Importantly, the high strength of the dynamic bonds enables a large amount of entropic energy to be stored in the elongated chains, enabling the polymer to achieve a large actuation force during recovery.