title: Temperature-memory polymer actuators.
abstract: Reading out the temperature-memory of polymers, which is their ability to remember the temperature where they were deformed recently, is thus far unavoidably linked to erasing this memory effect. Here temperature-memory polymer actuators (TMPAs) based on cross-linked copolymer networks exhibiting a broad melting temperature range (ΔT(m)) are presented, which are capable of a long-term temperature-memory enabling more than 250 cyclic thermally controlled actuations with almost constant performance. The characteristic actuation temperatures T(act)s of TMPAs can be adjusted by a purely physical process, guiding a directed crystallization in a temperature range of up to 40 °C by variation of the parameter T(sep) in a nearly linear correlation. The temperature T(sep) divides ΔT(m) into an upper T(m) range (T > T(sep)) forming a reshapeable actuation geometry that determines the skeleton and a lower T(m) range (T < T(sep)) that enables the temperature-controlled bidirectional actuation by crystallization-induced elongation and melting-induced contraction. The macroscopic bidirectional shape changes in TMPAs could be correlated with changes in the nanostructure of the crystallizable domains as a result of in situ X-ray investigations. Potential applications of TMPAs include heat engines with adjustable rotation rate and active building facades with self-regulating sun protectors.
authors.affiliation: Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, 14513 Teltow, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Behl
authors.forename: Karl
authors.initials: K
authors.lastname: Kratz
authors.forename: Ulrich
authors.initials: U
authors.lastname: Noechel
authors.forename: Tilman
authors.initials: T
authors.lastname: Sauter
authors.forename: Andreas
authors.initials: A
authors.lastname: Lendlein
mesh_terms: D006358:Hot Temperature; D011095:Polyethylenes / Q000138:chemical synthesis / Q000737:chemistry*; D011145:Polyvinyls / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D011095:Polyethylenes; D011145:Polyvinyls; C548976:poly(ethylene-co-vinyl acetate-co-carbon monoxide)
keywords: active movement; reversible shape-memory polymer