A study of polymer chain diffusion by surface enhanced Raman: effects of plasmonic substrate topology

Area of Science:

• Materials Science
• Polymer Science
• Spectroscopy

Background:

• Polymer interdiffusion is crucial for material properties.
• Accurate nanoscale diffusion measurements are challenging.
• Plasmonic substrates can enhance Raman signals.

Purpose of the Study:

• To develop a novel, labeling-free method for tracking polymer chain interdiffusion.
• To investigate the effectiveness of plasmon-enhanced Raman spectroscopy for nanoscale diffusion studies.
• To identify optimal plasmonic substrate designs for reliable diffusion measurements.

Main Methods:

• Utilized a deuterated-polystyrene/polystyrene (dPS/PS) bilayer system.
• Employed plasmonic substrates (gold-based with varied nanostructures) to enhance Raman signals.
• Performed in situ dynamic spectral acquisition during annealing to monitor interdiffusion.

Main Results:

• Demonstrated successful in situ tracking of dPS/PS interdiffusion.
• Identified highly regular topology and surface continuity of plasmonic substrates as critical for reliable data.
• Achieved diffusion coefficients in the range of 10⁻¹³–10⁻¹⁵ cm²/s with sampled regions below 40 nm using pyramidal substrates.

Conclusions:

• Plasmon-enhanced Raman spectroscopy is a viable labeling-free technique for nanoscale polymer interdiffusion.
• Pyramidal plasmonic substrates offer superior performance for this application.
• The methodology provides precise measurements of diffusion coefficients and sampled region dimensions.