Remote radiofrequency triggering of topography changes in a surface micropatterned PANI@PNIPAM nanocomposite

Abstract

The presence of polyaniline (PANI) conducting polymer loaded in thick films of a transparent and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) hydrogel network allowed for absorption of UV light and modification of dry (PANI@PNIPAM) nanocomposites by direct laser interference patterning (DLIP) at 355 nm. This resulted in a surface morphology of a nano-foam superimposed on a dominant line/groove pattern. The observations are rationalized based on currently accepted mechanisms for laser-induced polymer surface modification. Furthermore, the PANI in the nanocomposite films absorbs radiofrequency (RF) radiation remotely inducing the volume phase transition of PNIPAM. The swelled, low-roughness state for PANI@PNIPAM collapsed into a non-swelled and patterned film. The procedure provided the optimum RF dose range for preserving the surface topography of the films. The evidence suggests that the DLIP processing of PANI@PNIPAM films preserve the thermosensitivity of the original PNIPAM material and shows up the potential for tuning the surface morphology of the composite due to synergistic effects of both RF actuation on PANI and temperature rise of PNIPAM. In this sense, the surface pore size increase accompanying the development of line/groove pattern by DLIP, creates a structure onto PANI@PNIPAM films with potential for the development of remotely triggered soft-sensors and drug delivery systems.