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 understanding of hierarchical, complex solution-state self-assembly 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 π–π 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.

Efficient all polymer active layers with long-range ordered 1D p–n nanoheterojunctions confirmed by TEM tomography

“…The P(NDI2OD-T2) with a crystalline character is well known to form a 1D nanowire (NW) structure in a certain solvent. 42,43 In general, solution-state crystallization-driven assembly of polymer can be induced using a marginal solvent or mixed solvent having a limiting solubility. The compatibility between P(NDI2OD-T2) and the solvent used in this study was predicted considering the HSP space ( R a ) (see ESI†).…”

Recent developments of block copolymers in nonvolatile memory and artificial synapses

“…Block copolymer designs is a widely investigated polymer architecture, and its intrinsic self‐assembled nanostructures can be finely tuned by manipulating the structure and processing parameters. Notably, the determining critical factors for the nanostructures are the degree of polymerization, the block ratio, the Flory−Huggins interaction parameter ( χ ) between the blocks, and the annealing conditions 13 . These efforts can result in a microphase‐separated morphology with distinct domains such as cylinders, spheres, gyroids, and lamellae.…”

“…Notably, the determining critical factors for the nanostructures are the degree of polymerization, the block ratio, the FloryÀHuggins interaction parameter (χ) between the blocks, and the annealing conditions. 13 These efforts can result in a microphase-separated morphology with distinct domains such as cylinders, spheres, gyroids, and lamellae. BCPs have been chosen owing to their tunable chemical structure with many options of polymers for competent functions of memory applications.…”

Crystallization-driven self-assembly of poly(3-hexylthiophene)-b-poly(2,5-bis(2-ethylhexyloxy)p-phenylene), a π-conjugated diblock copolymer with a rigid rod corona-forming block

“…21,22 These materials have been used for photocatalytic hydrogen production, 2 as the active layer in organic field effect transistors, 3 and for flexible pressure sensors; 23 however, exerting control over the length and dimensions of these nanostructures remains challenging. 8,24,25 Living CDSA is a useful seeded growth technique to generate low length dispersity (D L ) (<1.1) samples of 1D micelles with controlled size and dimensions. 11,[26][27][28][29] The living CDSA seeded growth method begins with the formation of long polydisperse nanofibers that are subsequently fragmented by sonication to generate short "seed" micelles with low length differences.…”