Morphology of Nanostructured Polymer Brushes Dependent on Production and Treatment

Abstract

The morphology of top-down and bottom-up nanostructured neutral brushes is studied as a function of the production process and the quality of solvent to which the brushes have been exposed. Neutral brushes of poly­(tert-butyl methacrylate) (PtBuMA) were grafted from the substrate by surface-initiated radical-chain polymerization (SI-RCP). Brush patterning was conducted using deep ultraviolet (DUV) photolithography following either top-down (TD) or bottom-up (BU) approaches with patterned lines as small as 200 nm. The resulting brushes were immersed in toluene or methanol, and the change of morphology of the dried brushes was monitored using tapping mode atomic force microscopy (AFM). TD nanopatterned brushes (NPBs) exhibit a box-like and BU generated brushes a lens-like shape directly after the production process. We show that the pattern width for the BU brushed depends not only on the wetting properties of the areas adjacent to the pattern but also on the process history to which the sample has been exposed, especially the solvent quality. Furthermore, we show that TD NPBs are cross-linked on the edges of the pattern because of the high-energy process conditions during brush patterning and study the behavior of the thus-obtained structures.

Entropic death of nonpatterned and nanopatterned polyelectrolyte brushes

“…The widths of the polymer chain grafted areas varied over a range from 0.2 to 50 μm to ensure to cover the point of transition from a NPB, where the whole pattern is affected by stress relaxation due to edge effects, to a micropatterned polymer brush (MPB), where only the chains at the edge of the pattern experience stress relaxation [see Fig. 7(a)] . To monitor the rate of degradation the cross‐sectional integrals A of all brush patterns were measured in the dry state using tapping mode AFM before and after exposure to solvents.…”

“…7(a)]. 42,44,50 To monitor the rate of degradation the cross-sectional integrals A of all brush patterns were measured in the dry state using tapping mode AFM before and after exposure to solvents. An example is depicted in Figure 5 (a).…”

“…The widening of the brush line after exposure to water is caused by relaxation of the brush chains at the periphery of the pattern and wetting of the substrate, which has been described in detail in a previous work. 50 From the observed values, the relative cross-sectional integrals A rel of the brush patterns were calculated as…”

“…Motivated by this situation, the present experimental work investigates the thermodynamic stability and its kinetic aspects of high‐molecular‐weight poly(4‐methyl vinylpyridinium iodide) (PMeVP) brushes as a function of different extrinsic and intrinsic parameters. The growth by surface‐initiated radical‐chain polymerization (SI‐RCP) of high‐molecular‐weight polymer brushes on silicon is performed as reported previously, as was the nanopatterning by deep‐ultraviolet (DUV) photolithography to achieve bottom‐up (BU) nanopatterned PEBs . The brush layer thickness or rather the cross‐sectional integral is studied by ellipsometry and tapping mode atomic force microscopy (AFM).…”

“…The growth by surface-initiated radical-chain polymerization (SI-RCP) of high-molecular-weight polymer brushes on silicon is performed as reported previously, 48,49 as was the nanopatterning by deep-ultraviolet (DUV) photolithography to achieve bottom-up (BU) nanopatterned PEBs. 33,50 The brush layer thickness or rather the cross-sectional integral is studied by ellipsometry and tapping mode atomic force microscopy (AFM). The investigation enables a closer look on the impact of the chemical nature, the confinement, the environment, and the polymer chain dynamics on the PEBs thermodynamic stability, which is important for the preservation of their function.…”