Nanoparticle role on the repeatability of stimuli-responsive nanocomposites.

Repeatability of the responsiveness with time is one important concern for effective durable functions of stimuli-responsive materials. Although the increase in the yield and tensile strength of the hybrid composite materials by nanoparticle (NP) incorporation has been reported, exact NP effect on stimuli-responsiveness is rarely reported. In this study, a set of nanoscale actuating system is demonstrated by a thermo-sensitive process operated by polyethylene glycol (PEG) linked by gold nanoparticle (AuNP). This designed nanocomposite exclusively provides an artificial on/off gate function for selective passages of permeate molecules. The results demonstrate high repetition efficiency with sharp responding in a timely manner. In terms of the morphology changes induced by repeated swelling-deswelling mechanics, the nanocomposite exhibits phase separation between AuNP clusters and PEG domains. This leads to a delay in responsiveness in a cumulative way with time. Acting as stable junction points in the nanocomposite network structures, the incorporated AuNPs contribute to maintain repeatability in responsiveness. This study contributes to new-concept smart material design and fundamental understanding on the hybrid nanomaterials for various applications in terms of a dynamic mechanical behavior.