Resonant X-Ray Diffraction of Conjugated Polymers at the Selenium K-Edge

Area of Science:

• Materials Science
• Polymer Chemistry
• X-ray Physics

Background:

• Conjugated polymers possess a complex microstructure influencing semiconductor device performance.
• Characterizing this microstructure, particularly the degree of order between amorphous and crystalline states, remains challenging.
• Understanding molecular packing is crucial for optimizing polymer-based electronic materials.

Purpose of the Study:

• To investigate the potential of selenium K-edge resonant diffraction for characterizing conjugated polymer thin films.
• To explore how variations in X-ray energy across the selenium absorption edge can reveal microstructural details.
• To assess the utility of this method for studying molecular packing and π--π stacking.

Main Methods:

• Utilized resonant diffraction (anomalous scattering) by varying X-ray energy across the selenium K-edge (12.66 keV).
• Studied two selenium-containing polymers: poly(3-hexylselenophene) (P3HS) and a naphthalene diimide-based copolymer (PNDI-SVS).
• Compared selenium K-edge results with sulfur K-edge measurements on a thiophene analog of PNDI-SVS.

Main Results:

• Observed variations in diffraction intensity and anisotropic diffraction at the selenium K-edge, though less pronounced than at the sulfur K-edge.
• Demonstrated the potential of selenium K-edge resonant diffraction to probe small crystalline spacings, including those related to π--π stacking.
• Provided evidence that this technique can assist in refining structural models of conjugated polymer thin films.

Conclusions:

• Selenium K-edge resonant diffraction is a viable technique for obtaining novel microstructural information on conjugated polymers.
• The method shows promise for detailed analysis of molecular packing and the ordering within polymer thin films.
• Further studies can leverage this approach to enhance the understanding and design of high-performance polymer semiconductor devices.