期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 110, 期 31, 页码 12555-12559出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1301895110
关键词
reversible shape-memory polymer; active movement
资金
- Helmholtz Association
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 (Delta T-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 degrees C by variation of the parameter T-sep in a nearly linear correlation. The temperature T-sep divides Delta T-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.
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