How a Small Modification of the Corona-Forming Block Redirects the Self-Assembly of Crystalline–Coil Block Copolymers in Solution

Three-Dimensional Polymer Micelles Formed by Crystallization-Driven Self-Assembly

ConspectusPolymer self-assembly plays a crucial role across various fields, such as biomedicine, catalysis, and optoelectronics. Over the years, self-assembly in solution has attracted significant interest. In 2007, our group, in collaboration with Prof. Ian Manners, published a groundbreaking article in Science on living crystallization-driven self-assembly (CDSA) of amphiphilic block copolymers featuring a crystalline core-forming block. This study focused on polyferrocenylsilane block copolymers (PFS BCPs). Living CDSA operates similarly to living polymerization, enabling the precise fabrication of micelles with predictable shapes and dimensions. The crystalline nature of the core-forming block promotes the formation of structures with low interfacial curvature, such as cylinders and platelets, which are rarely formed in traditional self-assembly techniques based on microphase separation.Over the past two decades, we have pioneered a range of strategies to create one-dimensional (1D), 2D, 3D, and hierarchical uniform PFS BCP structures via CDSA. This method has also been extended to other semicrystalline polymer systems to produce regular and uniform assemblies. While 1D and 2D micelles have been extensively studied, the fabrication of 3D structures remains relatively rare. Nature, however, possesses exquisite 3D structures. Although CDSA has generated some 3D structures, it has not yet achieved the complexity found in nature. Researchers continue to push boundaries toward creating more intricate 3D structures.In this Account, we summarize our research advancements on 3D structure fabrication via CDSA. The free energy of the system, influenced by various factors, ultimately determines micellar morphology and growth behavior. Our work has led to the formation of branched structures through multistep seeded growth processes, incorporating PFS homopolymers (HP) with PFS BCP, manipulating the cooling rate, adjusting the corona block composition, controlling polymer dispersity, and varying solvents. Further innovations involved the use of organic sacrificial templates to produce hollow fiber-basket polymersomes and the application of inorganic substrates for surface micelle growth, yielding organic-inorganic hybrid materials with tailored functionalities. A significant breakthrough was the development of protocols for generating uniform polymeric spherulites and their precursors in solution. Although spherulites are common in bulk polymer materials and materials found in fields such as geology and biology, they have not been observed from block polymers in solution. We uncovered a novel CDSA mechanism in which defects in lamellar precursors act as a critical driver for constructing 3D architectures. To achieve intricate, bioinspired, and uniform 3D structures, further efforts will focus on enhancing structural control and integrating multifunctional properties.

Controllable Self-Assembly Morphologies of PPV-Based Block Copolymers

Poly(p-phenylenevinylene) (PPV) is a classic semiconducting π-conjugated polymer with outstanding optical and electronic properties, which shows important applications in the fields of optoelectronic, such as organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs). In the working process of the device, the microstate of PPV decides its property. Therefore, it is significant to achieve ordered morphologies based on PPV at micro scale. Due to the long rigid backbone and large area of delocalized electron, PPV has a strong tendency towards ordered aggregation through intermolecular π-π interaction, and "rod-coil" type block copolymer (BCP) based on PPV with a corona chain to improve the solubility is always built for self-assembly in situ solution. However, obtaining regular PPV based micro-/nano-structures in a controllable and uniform form remains challenging. In this review, we summarize the progresses in constructing multi-dimensional regular self-assembly morphologies based on PPV BCPs and exploring the application potential of these delicate functional nanomaterials. The molecular design strategy and growth mechanism can be extended to regulate the aggregation state of functional semiconducting conjugated polymers, which is beneficial to improving their performance in application of microelectronics, optoelectronics, biology and so on.

AIE-Active, Stimuli-Responsive Fluorescent 2D Block Copolymer Nanoplatelets Based on Corona Chain Compression

Aggregation-induced emission (AIE) represents a powerful tool in nanoscience as a result of enhanced luminescence in the condensed state. Although AIEgenic materials have been utilized in a wide range of applications, well-defined self-assembled nanoparticles with tailorable and uniform dimensions and morphology remain challenging to access. Herein, we use the seeded growth, living crystallization-driven self-assembly (CDSA) method to prepare size-tunable and uniform AIE-active 2D nanoplatelets from amphiphilic block copolymer (BCP) precursors with a crystallizable core-forming block and a corona-forming block to which tetraphenylethene (TPE) groups were covalently grafted as AIE-active pendants. The nanoplatelets were formed as a result of a solvophobicity-induced 1D to 2D morphology preference change, which accompanied the seeded growth of a BCP with a quaternized corona-forming block bearing the TPE luminogen. The 2D nanoplatelets exhibited a solvent-responsive fluorescent emission, and examples with coronas containing homogeneously distributed AIE-active TPE groups and Hg(II)-capturing thymine units exhibited excellent performance as proof-of-concept "turn-on" sensors for Hg(II) detection with a rapid response, high selectivity, and a low detection limit (5-125 × 10^-9 M, i.e., 1-25 ppb). The fluorescence intensity was found to be nonlinear with respect to analyte concentration and to increase with the area of the nanoplatelet. This behavior is consistent with a cooperative mechanism based on changes in the steric compression of the corona chains, which gives rise to a restriction of the intramolecular motion (RIM) effect.

π-Conjugated-polymer-based nanofibers through living crystallization-driven self-assembly: preparation, properties and applications

π-Conjugated-polymer-based nanofibers (CPNFs) of controlled length, composition and morphology are promising for a broad range of emerging applications in optoelectronics, biomedicine and catalysis, owing to the morphological merits of fiber-like nanostructures and structural attributes of π-conjugated polymers. Living crystallization-driven self-assembly (CDSA) of π-conjugated-polymer-containing block copolymers (BCPs) has emerged as an efficient strategy to prepare CPNFs with precise dimensional and structural controllability by taking advantage of the crystallinity of π-conjugated polymers. In this review, recent advances in the generation of CPNFs have been highlighted. The influence of the structure of π-conjugated-polymer-containing BCPs and experimental conditions on the CDSA behaviors, especially seeded growth and self-seeding processes of living CDSA, has been discussed in detail, aiming to provide an in-depth overview of living CDSA of π-conjugated-polymer-containing BCPs. In addition, the properties of CPNFs as well as their potential applications have been illustrated. Finally, we put forward the current challenges and research directions in the field of CPNFs.

Dimension control on self-assembly of a crystalline core-forming polypeptoid block copolymer: 1D nanofibers versus 2D nanosheets

The balance between the crystallization and solubility of the block copolymer dominates the nanostructures.

Morphological transformation of ultrasonically obtained nanofibers during living self-assembly

The nanofibers are obtained by ionic self-assembly and living self-assembly.

Synthesis and self-seeding behavior of oligo(p-phenylene vinylene)-b-poly(N-(2-hydroxypropyl)methacrylamide)

This article reports the preparation of uniform fiber- and ribbon-like nanostructures via the self-seeding of OPV₅-b-PHPMA diblock copolymers.

"Installation art"-like hierarchical self-assembly of giant polymeric elliptical platelets

This paper reports the aqueous self-assembly of giant elliptical platelets over 20 μm in axial length, from a novel polyamide. Both the self-assembly pathway and mechanism were studied using morphology and X-ray characterizations. The polymer first self-organizes into small quadrangular frustum pyramid platelets, and then these small platelets can be further installed into giant elliptical platelets through an "installation art"-like hierarchical self-assembly process driven by crystallization. The as-prepared regular giant platelets can further aggregate together into multi-horned or flower-like superstructures.