Co-crystallization phase transformations in all π-conjugated block copolymers with different main-chain moieties

Area of Science:

• Polymer Science
• Materials Science
• Crystallization Kinetics

Background:

• Block copolymers (BCPs) self-assemble into ordered nanostructures, crucial for material properties.
• Co-crystallization of dissimilar polymer blocks in BCPs can lead to unique phase behavior and morphologies.
• Understanding the interplay between self-crystallization and co-crystallization is key to controlling BCP nanostructure.

Purpose of the Study:

• To synthesize and investigate the multi-crystallization effect in novel all-π-conjugated poly(2,5-dihexyloxy-p-phenylene)-b-poly(3-(2-ethylhexyl)thiophene) (PPP-P3EHT) block copolymers.
• To explore the formation of uniform domains through co-crystallization of dissimilar PPP and P3EHT blocks.
• To elucidate the sequential phase transitions and hierarchical superstructures formed by varying the P3EHT fraction.

Main Methods:

• Synthesis of crystalline and monodisperse all-π-conjugated PPP-P3EHT block copolymers.
• Investigation of co-crystallization behavior between PPP and P3EHT blocks with distinct structures.
• Analysis of phase transitions and nanostructure evolution with increasing P3EHT content.

Main Results:

• Achieved co-crystallization of PPP and P3EHT blocks into a single uniform domain with interdigitated side-chains.
• Observed sequential phase transitions leading to hierarchical superstructures: PPP nanofibrils, co-crystalline nanofibrils, bilayer structures, and P3EHT nanofibrils.
• Identified a novel co-crystalline lamellar structure, demonstrating the balance between self- and co-crystallization.

Conclusions:

• Demonstrated the co-crystallization capability of all-conjugated BCPs with differing main-chain moieties.
• The study provides insights into the formation of ordered nanostructures driven by molecular affinity and crystallization kinetics.
• Findings offer new guidelines for organizing π-conjugated BCPs for advanced optoelectronic applications.