Cross-linked functionalized poly(3-hexylthiophene) nanofibers with tunable excitonic coupling

Area of Science:

• Materials Science
• Polymer Chemistry
• Photophysics

Background:

• Poly(3-hexylthiophene) (P3HT) is a semiconducting polymer with potential in organic electronics.
• Controlling the morphology and photophysical properties of P3HT nanostructures is crucial for device performance.
• Chemical cross-linking offers a route to enhance the stability and processability of polymer nanofibers.

Purpose of the Study:

• To investigate the impact of different chemical cross-linking strategies on the photophysical properties of functionalized P3HT nanofibers.
• To understand how structural modifications induced by cross-linking affect excitonic coupling and charge transport.
• To develop mechanically and chemically robust P3HT-based nanostructures with tunable optoelectronic characteristics.

Main Methods:

• Synthesis of P3HT-based diblock copolymers (P3HT-b-P3MT and P3HT-b-P3ST).
• Fabrication of nanofibers from these copolymers.
• Chemical cross-linking using hexamethylene diisocyanate (HDI) for P3MT and disulfide cross-linking for P3ST.
• Characterization of photophysical properties using ensemble and single-nanofiber photoluminescence (PL) spectroscopy, transient absorption spectroscopy (visible and near-IR).

Main Results:

• Robust P3HT nanofibers were successfully formed via chemical cross-linking.
• Cross-linking P3HT-b-P3MT nanofibers with HDI significantly disrupted excitonic coupling, leading to photoluminescence similar to unaggregated P3HT.
• Cross-linking P3HT-b-P3ST nanofibers minimally altered excitonic coupling, preserving the aggregate structure.
• Different photophysical behaviors were observed despite similar gross structures and pre-cross-linked absorption spectra.

Conclusions:

• The choice of functionalizing moiety and cross-linking strategy dictates the photophysical properties of P3HT nanofibers.
• Cross-linking-induced strain in P3MT systems disrupts intra- and interchain coupling, while cross-linking in P3ST systems minimally perturbs the aggregate structure.
• This study demonstrates a method for tuning the optoelectronic properties of P3HT nanostructures through controlled chemical modification, enhancing their robustness.