Programmable Assembly of π-Conjugated Polymers.

π-Conjugated polymers have numerous applications due to their advantageous optoelectronic and mechanical properties. These properties depend intrinsically on polymer ordering, including crystallinity, orientation, morphology, domain size, and π-π interactions. Programming, or deliberately controlling the composition and ordering of π-conjugated polymers by well-defined inputs, is a key facet in the development of organic electronics. Here, π-conjugated programming is described at each stage of material development, stressing the links between each programming mode. Covalent programming is performed during polymer synthesis such that complex architectures can be constructed, which direct polymer assembly by governing polymer orientation, π-π interactions, and morphological length-scales. Solution programming is performed in a solvated state as polymers dissolve, aggregate, crystallize, or react in solution. Solid-state programming occurs in the solid state and is governed by polymer crystallization, domain segregation, or gelation. Recent progress in programming across these stages is examined, highlighting order-dependent features and assembly techniques that are unique to π-conjugated polymers. This should serve as a guide for delineating the many ways of directing π-conjugated polymer assembly to control ordering, structure, and function, enabling the further development of organic electronics.

Oxidation promoted self-assembly of π-conjugated polymers.

Self-assembly is an attractive strategy for organizing molecules into ordered structures that can span multiple length scales. Crystallization Driven Self-Assembly (CDSA) involves a block copolymer with a crystallizable core-forming block and an amorphous corona-forming block that aggregate into micelles with a crystalline core in solvents that are selective for the corona block. CDSA requires core- and corona-forming blocks with very different solubilities. This hinders its use for the self-assembly of purely π-conjugated block copolymers since blocks with desirable optoelectronic properties tend to have similar solubilities. Further, this approach is not readily reversible, precluding stimulus-responsive assembly and disassembly. Here, we demonstrate that selective oxidative doping of one block of a fully π-conjugated block copolymer promotes the self-assembly of redox-responsive micelles. Heteroatom substitution in polychalcogenophenes enables the modulation of the intrinsic polymer oxidation potential. We show that oxidized micelles with a narrow size distribution form spontaneously and disassemble in response to a chemical reductant. This method expands the scope of π-conjugated polymers that can undergo controlled self-assembly and introduces reversible, redox-responsive self-assembly of π-conjugated polymers.

Surface Patterning of Uniform 2D Platelet Block Comicelles via Coronal Chain Collapse.

The formation of colloids with anisotropically patterned surfaces is of growing interest for the creation of hierarchical structures and the templating of nanoparticles. We have recently shown that well-defined two-dimensional platelets with low areal dispersities can be formed by the seeded growth of a blend of homopolymers and block copolymers. Herein we form rectangular platelets containing two block copolymers with different coronal chemistries. On addition of a solvent that is only able to solvate the corona of one block, we were able to form colloidally stable micelles with patterned surfaces via coronal collapse. Scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy and atomic force microscopy were employed to provide information on the structure and size of the patches decorating the micelle surfaces.