Surface-sensitive molecular information on polymers from UV-resonance Raman spectroscopy

Area of Science:

• Polymer science
• Spectroscopy
• Materials science

Background:

• Poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) are widely used polymers.
• Characterizing the surface properties of polymers is crucial for understanding their performance and degradation.
• Traditional Raman spectroscopy has limitations in probing thin surface layers due to penetration depth.

Purpose of the Study:

• To investigate the capability of Ultraviolet Resonance Raman Spectroscopy (UV-RRS) for analyzing polymer surfaces.
• To determine the probing depth of UV-RRS under resonance conditions.
• To compare the surface resolution of UV-RRS with conventional Raman spectroscopy.

Main Methods:

• Application of UV-RRS to samples of PET and PEN with varying thicknesses.
• Analysis of spectral data obtained under strong absorption (resonance) conditions.
• Utilizing a microscope in conjunction with UV-RRS.

Main Results:

• UV-RRS effectively probes only the top layer of polymer samples, with a depth in the hundreds of nanometers.
• The technique provides molecular vibrational spectra of this thin top layer.
• Surface resolution achieved by UV-RRS is at least an order of magnitude better than non-resonance Raman spectroscopy.

Conclusions:

• UV-RRS is a powerful technique for high-resolution surface analysis of polymers.
• The method allows for the study of molecular vibrations in the uppermost layers of materials like PEN and PET.
• UV-RRS offers a significant improvement in surface sensitivity for polymer characterization using microscopy.