Swelling of Poly(methyl acrylate) Brushes in Acetone Vapor

Abstract

Sensor platforms can benefit from the incorporation of polymer brushes since brushes can concentrate the analyte near the sensor surface. Brushes that absorb acetone vapor are of particular interest since acetone is an important marker for biological processes. We present a simple procedure to synthesize acetone-responsive poly(methyl acrylate) brushes. Using spectroscopic ellipsometry, we show that these brushes respond within seconds and swell by more than 30% when exposed to acetone vapor. Moreover, quartz crystal microbalance measurements demonstrate that the brushes can be exploited to increase the acetone detection sensitivity of sensors by more than a factor 6. Surprisingly, we find that the swelling ratio of the brushes in acetone vapor is independent of the grafting density and the degree of polymerization of the polymers in the brush. This is qualitatively different from swelling of the same brushes in liquid environments, where the swelling ratio decreases for increasing grafting densities. Yet, it indicates that the brushes are robust and reproducible candidates for implementation in vapor sensor systems.

Surface-Grafted Polymeric Ionic Liquids with Tunable Morphology via In/Ex Situ Cross-linking Methods

“…In this case, the graft density is a more telling metric of the swelling behavior. In accordance with literature precedent, − higher ratios of swelling ( h s / h d ) were observed for Ec brushes with lower grafting density.…”

Concentrating Vapor Traces with Binary Brushes of Immiscible Polymers

“…In addition to an increased sensitivity, the presence of brushes on sensor surfaces can also create more selectivity, which is important for sensing particular (groups of) molecules and in developing artificial noses. 10 The simulations presented in this Letter show the behavior of mixed brushes exposed to a single-component vapor, so we can only draw conclusions on the sensitivity of the coating. Nevertheless, in a recent paper, 24 we explored the selectivity of vapor sorption in single-component brushes using MD simulations with a two-component Lennard-Jones vapor using a double grand-canonical Monte Carlo scheme.…”

Synthetic strategies to enhance the long-term stability of polymer brush coatings

“…Polymer brushes are typically grown from well-defined surfaces such as silicon [58][59][60] or gold. [61][62][63] For silicon wafers, initiator coupling is often achieved by silane chemistry, 64,65 while gold surfaces are frequently decorated with initiators using disulphides or thiols.…”

“…[103][104][105][106] Vapor-solvated swelling ratios are smaller than the swelling ratios in liquid. 60 Nevertheless, hydrophilic brushes such as poly(3sulfopropyl methacrylate potassium) (PSPMA) and poly(2methacryloyloxyethyl phosphorylcholine) (PMPC) can absorb sufficient amounts of water vapor from the air to allow for the detachment of B10-50% of the polymers over 8 weeks. 101 In the discussions above, it has become clear that the experimental evidence supports the hypothesis that brushes degraft by tension-enhanced breakage of surface bonds.…”