Crystallization-Driven Solution-State Assembly of Conjugated Block Copolymers in Materials Science

Abstract

Conjugated polymers are a promising material scaffold alternative to inorganic semiconductors for large-area flexible, stretchable electronics because of their tunable optoelectronic properties, mechanical compliance, compositional tailorability, light weight, and low-cost solution processability. In particular, solution-state crystallization-driven assembly of conjugated block copolymers (BCPs) consisting of a rigid rod-like conjugated polymer and a flexible coil-like polymer is attracting growing attention as a nanomaterial manufacturing strategy to customize such functions and performance based on the of BCP into nanoparticles. In this Perspective, we highlight substantial advances in developing crystallization-driven assembly of conjugated BCPs by discussing fabrication methods and nanoaggregate formation mechanisms, accessible controls on molecular packing, arrangement, and orientation within the aggregates and nanostructural diversity, and their applications. The resultant nanoparticles are under exploration in various fields, with potential from optoelectronics to biomedicine. The conjugated BCPs can form the spontaneous nanoarchitecture by relatively subtle complex thermodynamic and kinetic pathways in solution-state molecular assembly. The stepwise crystallization-driven assembly of conjugated BCPs involving a crystal seed formation and crystal growth, which mainly uses strong pi-pi interactions as a driving force, should be closely understood but remain elusive. It is necessary to develop a strategy to ensure nanoparticle uniformity in size and shape by controlling dynamic chemical bonds between building blocks in addition to discovering unique crystalline nanostructures to expand their applicability as reproducible and reliable functional materials. The analysis tools are also needed to verify successful control directly. We will discuss current issues and future directions from a polymer/supramolecular nanochemistry point of view to provide a general platform.