Sprecher
Beschreibung
A thermoresponsive polymer, such as poly(isopropyl acrylamide) (PNIPAM), changes state when the temperature crosses its phase transition point. PNIPAM-based polymers exhibit broad hysteresis for the volume phase transition between the swollen and collapsed states. These polymers display atypical behaviors, such as bistability, remanence, information storage capabilities, and memory functions. The behavior of the polymer near the transition point and the long-term stability of swollen or collapsed polymer clusters within the hysteresis temperature range have been thoroughly investigated using scattering and electron microscopy techniques.
The phase transition from the swollen to the collapsed state (and vice versa) has been studied in detail using dynamic light scattering and cryo-TEM. To do so, samples were prepared across the transition point with a small temperature step. The broad hysteresis of PNIPAM-based polymers opens exciting possibilities for achieving bistability, remanence, and efficient, reversible information storage. Our research highlights the potential of PNIPAM and its block copolymers, which significantly expand the hysteresis window and enhance the material's capabilities.
Furthermore, hysteresis is intricately connected to the dynamic assembly and disassembly of cluster domains during phase transitions, paving the way for advanced applications. Imagine writing information thermally with a laser or heated/cooled pen tips on a thin-film backscattering display. The versatility is astounding: not only can the bistable state be changed smoothly by temperature, but also by pH, enabling an AND logic gate function. We also discovered an intriguing memory state. Information can be encoded within the hysteresis window and remain hidden at elevated temperatures, adding a layer of complexity and creativity to information management.