Photoinduced Anisotropic Assembly of Conjugated Polymers in Insulating Polymer Blends

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Poly(3-hexylthiophene) (P3HT) is a key organic semiconductor.
• Controlling P3HT morphology is crucial for charge transport.
• Insulating polymers like polystyrene (PS) and polyisobutylene (PIB) are often blended with P3HT.

Purpose of the Study:

• To investigate the effect of low-dose UV irradiation on P3HT-insulating polymer blends.
• To understand how UV irradiation influences P3HT nanofiber formation and morphology.
• To correlate film morphology with charge transport properties.

Main Methods:

• Preparation of blend solutions of P3HT with PS or PIB.
• Low-dose UV irradiation of the blend solutions.
• Formation of thin films via spin coating.
• Characterization of P3HT nanofibrillar structures and lamellar packing using techniques like X-ray diffraction (XRD) and microscopy.
• Measurement of macroscopic charge transport characteristics.

Main Results:

• UV irradiation induced highly ordered P3HT nanofibrillar structures in solidified films.
• Interconnected P3HT nanofibers formed through phase-separated P3HT islands.
• Films with as low as 5 wt% P3HT demonstrated excellent charge transport.
• PS influenced P3HT interactions, aiding UV processing but hindering lamellar packing.
• Increased PS content led to larger d-spacing and reduced coherence length in P3HT lamellar packing.

Conclusions:

• Low-dose UV irradiation is an effective method for creating ordered P3HT nanostructures in polymer blends.
• Morphology control via UV irradiation and polymer blending enables high charge transport even at low semiconductor concentrations.
• The choice of insulating polymer (PS vs. PIB) and its concentration significantly impacts P3HT self-assembly and film properties.