Tracking high molecular weight polymer interdiffusion on a SERS‐based platform

Abstract

We describe the implementation of an experimental setup based on Surface Enhanced Raman Spectroscopy (SERS) to investigate polymer interdiffusion. Ultra‐thin bilayer films of deuterated polystyrene (dPS) and polystyrene (PS) are placed in contact onto SERS‐active gold substrates with inverted square‐base pyramidal geometry and subsequently annealed. Initially, the Raman spectrum shows only spectral features of the polymer adjacent to the substrate. Upon annealing, Raman bands of the polymer located far from the substrate start to emerge, an indication of chain diffusion into the substrate hotspot and mixing between polymer layers. The kinetics of the process is consistent with transport of polymer chains in nanometer scale, with diffusion coefficients in the range 10−13 – 10−15 cm2/s. The temperature response of the process is characterized by an activation energy of 48.93 ± 1.5 kcal/mol, in excellent agreement with earlier experiments. SERS experiments provide a powerful and reliable experimental platform to characterize polymer interdiffusion without the need of chemical labeling, with several prospective applications to the study of chain dynamics in advanced polymer‐based nanocomposite materials. Copyright © 2016 John Wiley & Sons, Ltd.

Temperature-Modulated Doping at Polymer Semiconductor Interfaces

“…The resulting diffusivity plots as a function of molar fraction (Figure c,d) exhibit roughly symmetric peaked distributions with diffusion coefficient values ranging from ∼10 –14 cm 2 s –1 in the pure materials to ∼10 –13 cm 2 s –1 in the mixed phase, with the maximum occurring at a Nafion molar fraction of 0.42 and 0.57 for the O – and CF – signals, respectively. These diffusion coefficient values are in agreement with the expected values (10 –13 to 10 –15 cm 2 s –1 ) for interdiffusion of polymer films annealed above their T g …”

“…These diffusion coefficient values are in agreement with the expected values (10 −13 to 10 −15 cm 2 s −1 ) for interdiffusion of polymer films annealed above their T g . 31 Moreover, the shift in the O − diffusivity peak position to an apparently lower Nafion mass fraction can be explained by the presence of water molecules associated with the Nafion head groups. Whereas the CF − signal originates uniquely from the Nafion species, the normalized O − mass signal arises from both Nafion and water molecules associated with the hydrated film.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…Mana and Tomba described the tracking of high molecular weight polymer interdiffusion on a SERS‐based platform. They found that SERS measurements provide a powerful and reliable experimental platform for the characterization of polymer interdiffusion without the need of chemical labeling, with several prospective applications to the study of chain dynamics in advanced polymer‐based nanocomposite materials . S. R. Smith et al used shell‐isolated nanoparticle‐enhanced Raman spectroscopy to characterize oxide ores during thiosulfate‐mediated gold leaching.…”

“…They found that SERS measurements provide a powerful and reliable experimental platform for the characterization of polymer interdiffusion without the need of chemical labeling, with several prospective applications to the study of chain dynamics in advanced polymerbased nanocomposite materials. [40] S. R. Smith et al used shell-isolated nanoparticle-enhanced Raman spectroscopy to characterize oxide ores during thiosulfatemediated gold leaching. From their results, they concluded that the pressure-oxidation pretreatment process may successfully destroy or inactivate minerals found in the ore that are responsible for catalyzing thiosulfate decomposition into polysulfides, which results in low Au extraction efficiencies.…”

Following mass transport through barrier membranes with confocal Raman microscopy

“…Depth profiling has been used to track either polymer interdiffusion, [14][15][16] or diffusion of species in polymer matrices [17,18] ; lateral mapping has also been used with this purpose but less frequently. [19] Surface enhanced Raman has been recently applied to study polymer interdiffusion in nanometric scale, [20,21] whereas tip enhanced Raman has demonstrated its capabilities in characterizing the morphology of polymer blends at nanometric scale, opening up opportunities for diffusion studies. [22] Overall, Raman microscopy is a technique to consider for tracking mass transport in barrier membranes due to a unique combination of natural spectroscopic contrast between diffusant, matrix, and obstacle and the ability to probe the phenomenon at several levels of spatial resolution.…”