Microstructural Variation upon Introducing Di([2,2'-bithiophen]-5-yl)pyrenes into a Naphthalene Diimide-Based Polymer

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Conjugated molecules and polymers are crucial for organic electronics.
• Understanding structure-property relationships is key to optimizing material performance.
• Pyrene-based molecules offer unique electronic and structural properties.

Purpose of the Study:

• To investigate the effects of alkyl substitution and regioisomerism in pyrene-based molecules on polymer microstructure.
• To evaluate the impact of these molecular modifications on the electronic properties of polymer blends.
• To explore the role of naphthalene diimide-pyrene interactions in polymer backbone rigidification.

Main Methods:

• Synthesis and blending of four pyrene-based conjugated molecules (A-D) with a specific polymer (P).
• Characterization using differential scanning calorimetry, 1H NMR spectroscopy, and grazing-incidence X-ray scattering.
• Computational analysis using density functional theory and device measurements using organic field-effect transistors.

Main Results:

• Regioisomerism significantly influences polymer crystallization and aggregation, while alkyl substitution has a lesser effect.
• Alkyl substitution impacts lamellar stacking, but regioisomerism is critical for overall microstructure.
• Pyrene incorporation leads to polymer backbone rigidification via naphthalene diimide-pyrene interactions.
• Blends exhibit higher electron mobility than the base polymer, correlated with polymer crystallization.

Conclusions:

• Regioisomerism is a key factor in controlling the microstructure and properties of these pyrene-containing polymer systems.
• Pyrene units enhance polymer backbone rigidity and improve electron mobility in organic field-effect transistors.
• The blending approach offers advantages over previous incorporation methods due to increased molecular degrees of freedom.