@misc{behl_temperaturememory_polymer_2013, 
author={Behl, M.,Kratz, K.,Noechel, U.,Sauter, T.,Lendlein, A.},
title={Temperature-memory polymer actuators},
year={2013},
howpublished = {journal article},
doi = {https://doi.org/10.1073/pnas.1301895110},
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 (ΔTm) 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 Tacts 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 Tsep in a nearly linear correlation. The temperature Tsep divides ΔTm into an upper Tm range (T > Tsep) forming a reshapeable actuation geometry that determines the skeleton and a lower Tm range (T < Tsep) 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.},
note = {Online available at: \url{https://doi.org/10.1073/pnas.1301895110} (DOI). Behl, M.; Kratz, K.; Noechel, U.; Sauter, T.; Lendlein, A.: Temperature-memory polymer actuators. Proceedings of the National Academy of Sciences of the United States of America: PNAS. 2013. vol. 110, no. 31, 12555-12559. DOI: 10.1073/pnas.1301895110}}