Temperature-Driven Reversible Shape Transformation of Polymeric Nanoparticles from Emulsion Confined Coassembly of Block Copolymers and Poly(<i>N</i>-isopropylacrylamide)
Yaping Wang, Dengwen Hu, Xiaohua Chang, Yutian Zhu
Abstract
Shape-tunable particles in response to external stimuli have gained unprecedented opportunities for their great and remarkable potential in catalysts, sensors, and clinical systems. Especially, temperature-responsive particles are highly worthwhile due to their simplicity for manipulation. Herein, we incorporated thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) into the self-assembly of block copolymers (BCPs) within confined emulsion droplets, which generated novel temperature-triggered shape-switchable particles. At a temperature higher than the lower critical solution temperature (LCST) of PNIPAM, raspberry-like particles are formed initially. Interestingly, the raspberry-like particles can automatically transform into onion-shaped particles as the temperature is lower than the LCST of PNIPAM. This shape transformation is attributed to the temperature-mediated hydrophobic–hydrophilic transition of the anchored PNIPAM in BCP domains. This successful immobilization of PNIPAM within BCP domains is ascribed to the hydrogen bonds between them. Afterward, the onion-shaped BCP particles turn into raspberry-like particles again when the temperature is switched back to higher than the LCST of PNIPAM. More importantly, the change in BCP particle shape is reversible and can be repeated over many cycles upon adjusting the ambient temperature. In addition, the temperature-driven shape-switching BCP particles can be utilized to regulate temperature-triggered drug release, demonstrating their promising applications in clinical and biomedical systems.