Nanoplasmonic heating and sensing to reveal the dynamics of thermoresponsive polymer brushes

Abstract

Understanding of the phase transition dynamics of substrate tethered brushes of thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) is important for their application as, e.g., cell substrates with spatially selective cell affinity or drug delivery systems. But characterization of the brushes phase transition time is hampered by the low amount of involved pNIPAM. Here, by the simultaneous use of time resolved nanoplasmonic heating and sensing, we are able to measure a transition time of 160±20 μs for a 30 nm thick substrate tethered brush. The plasmon-induced temperature jump can be quantitatively deduced from the measured data. Nanoplasmonic platforms as applied here could serve as local and fast probes for a variety of dynamic processes in stimuli responsive molecules or polymers.