Controlling the Stability of Imprinted Nanostructures Using Grafted Nanoparticles

Structural decay in imprinted polymer-nanocomposite thin films presents an important problem from both fundamental and application standpoint as they find use in various applications such as nanoimprint and E-beam lithography. This work investigates the kinetics of structural decay in imprinted composite thin films of Polymethyl methacrylate (PMMA) grafted TiO₂ nanoparticles(NP) incorporated within PMMA matrix of a lower molecular weight compared to the grafted chains. Addition of grafted NP significantly improved the thermal stability above T_g and acted as stabilizing agents for the imprinted nanostructures. Utilizing ex-situ atomic force microscopy measurements, decay kinetics of the imprinted structures provide insights into stress relaxation of the nanocomposite film. We demonstrate that as the NP loading is increased, the imprinted nanostructure exhibited a higher relaxation time, indicative of slower decay kinetics. Furthermore, extrapolation of the relaxation behavior for this composite reveals a transition from antiplastication to plastication regime at 97°C below which NP decrease the relaxation time of the composite.These results provide a simple strategy to control high temperature nano-structural integrity in imprinted polymer-nanocomposite films by using grafted NPs.