Semi-conducting 2D rectangles with tunable length via uniaxial living crystallization-driven self-assembly of homopolymer

Abstract

Semi-conducting two-dimensional (2D) nanoobjects, prepared by self-assembly of conjugated polymers, are promising materials for optoelectronic applications. However, no examples of self-assembled semi-conducting 2D nanosheets whose lengths and aspect ratios are controlled at the same time have been reported. Herein, we successfully prepared uniform semi-conducting 2D sheets using a conjugated poly(cyclopentenylene vinylene) homopolymer and its block copolymer by blending and heating. Using these as 2D seeds, living crystallization-driven self-assembly (CDSA) was achieved by adding the homopolymer as a unimer. Interestingly, unlike typical 2D CDSA examples showing radial growth, this homopolymer assembled only in one direction. Owing to this uniaxial growth, the lengths of the 2D nanosheets could be precisely tuned from 1.5 to 8.8 μm with narrow dispersity according to the unimer-to-seed ratio. We also studied the growth kinetics of the living 2D CDSA and confirmed first-order kinetics. Subsequently, we prepared several 2D block comicelles (BCMs), including penta-BCMs in a one-shot method.

An Amphiphilic Corona-Forming Block Promotes Formation of a Variety of 2D Platelets via Crystallization-Driven Block Copolymer Self-Assembly

“…As seen in in the TEM images in Figure and Figure S6, rounded rectangular platelet structures were obtained. These platelets are fascinating structures and very different from the ones reported in previous work where 2D assemblies, including squares, , rectangles, ,,− diamonds, ,, ovals, ,,− and hexagonal disks, , were prepared. In the examples shown in Figure , one can see nearly straight edges for the long axis but rounded edges in the short axis.…”

“…The earliest examples of CDSA, with polyethylene glycol (PEG) as the core-forming block, led to square platelet structures. − Later examples, with poly­(ferrocenyldimethylsilane) (PFS) as the core-forming block and shorter corona-forming chains generated more ribbon-like planar (2D) structures, with the core characterized as a single crystal. , Core-crystalline 2D micelles formed by CDSA have now been reported for block copolymers with a broad variety of different core-forming blocks. Examples include polyethylene (PE), , poly­(3-hexylthiophene) (P3HT), , polycaprolactone (PCL), − and poly­( L -lactide) (PLLA). , In most cases, when the corona/core block ratios were less than 2, the BCPs tended to form 2D platelets. − There are a few exceptions where BCPs with long corona chains prefer to form elongated 2D structures. , Up to now, several types of 2D platelet structures have been fabricated, including squares, ,, rectangles, ,,− diamonds, ,, ellipsoidal or lenticular ovals, ,,− and hexagonal disks. , However, the factors that control the size and shape of these platelets and how they vary with sample preparation protocols are poorly understood.…”

Crystallization-Driven Self-Assembly of Block Copolymers Having Monodisperse Poly(lactic acid)s with Defined Stereochemical Sequences

“…Particularly, the crystallization-driven self-assembly (CDSA) of BCPs having a core-forming crystalline block in solution is of great interest as the crystallization of core-forming polymers require a precise control of their stereochemical structures, molecular weights, and molecular weight distributions. Controlled polymerization methods such as living ring-opening polymerization (ROP) have been employed to synthesize BCPs with well-defined crystalline polymer blocks such as polyferrocenylsilane (PFS), − poly­(lactic acid) (PLA), − and conjugated polymers. − Low-dimensional nanostructures with well-defined size, shape, and functions have been realized by living CDSA of various BCPs. − However, the CDSA of BCPs built with monodisperse polymer blocks and the effects of the absence of molecular weight distribution (in the crystal-forming polymer block) on its self-assembly has only been recently investigated. , Importantly, the contribution of the stereochemical sequence of the core-forming polymer block to the shape of nanostructures formed by CDSA has not been investigated.…”

Efficient and Controlled Seeded Growth of Poly(3-hexylthiophene) Block Copolymer Nanofibers through Suppression of Homogeneous Nucleation

“…200 nm as in segmented linear coaxial heterojunctions and quantum dots (QD) hybrid micelles . In other work, key developments have been achieved in terms of the application of living CDSA methods to form 1D and 2D nanoparticles from PPV BCP amphiphiles and PPV oligomers. − …”