Precision Macro (molecular) Assemblies

Abstract

Structural precision in hierarchical self-assembled architectures is ubiquitous in biological systems. For instance, DNA double helix, quaternary structures of proteins, tobacco mosaic virus, microtubules, and several other elegant systems are constituted through specific molecular recognitions that are responsible for regulating numerous complex functions in nature. Inspired by such elegant examples in living systems, the self-assembly of synthetic small molecules and macromolecules has been studied with great interest, especially in the past four decades since the concept of supramolecular chemistry had been established in a formal way. In this context, solution self-assembly of amphiphilic block copolymers (ABCPs) with amorphous core- forming blocks has been studied extensively in the past three decades owing to the possibility of generating different nanostructures in water,such as micelles, vesicles, fibers, lamella, and others.Despite the fact that self-assembly of ABCPs has proven to be an effective bottom- up approach for creating multilevel structures that are gateways to highly promising soft materials for diverse applications, attempts to improve specific and nontrivial functional utilities of these systems have been hampered by a number of significant problems. Aggregation of ABCPs in block-selective solvents is commonly catalyzed by the immiscibility-driven chain collapse of the amorphous core-forming blocks. Thus, the critical packing parameter, which in turn depends on the relative volume fraction of the hydrophobic and hydrophilic block segments, is the primary factor controlling the morphology of these polymer aggregates in solutions.This limits the ability to precisely tailor the internal order orsurface functional group display in such nanostructures or control their dimensions, shapes, and dispersity, which is crucial for their elegant biological functions. Moreover, for ABCPs with amorphous core- forming blocks, non-spherical structures are rarely accessible only within a limited window of block compositions and self-assembly environments. Sometimes, those are also contaminated with other undesired morphologies. Many studies have demonstrated that non-spherical, high aspect ratio nanostructures such as one- dimensional (1D) fibers and two- dimensional (2D) plateletperform superior functions in emerging applications, compared to their spherical analogues. This has paved the way for the emergence of new macromolecular designs toward the development of internally-ordered precision anisotropic structures.