skip to main content

Title: Oligoaniline-assisted self-assembly of polyaniline crystals
The conductivity and charge transport mobility of conjugated polymers (CPs) are largely correlated with their degree of crystallinity, rendering the crystallization of CPs an important endeavour. However, such tasks can be challenging, especially in the absence of sidechain functionalization. In this study, we demonstrate that the incorporation of a small amount of oligomers, specifically tetraaniline, can induce crystallization of the parent polymer, polyaniline, through a single-step self-assembly process. The resulting crystals are compositionally homogeneous because the oligomers and their parent polymer share the same repeating unit and are both electroactive. Mechanistic studies reveal that the tetraaniline forms a crystalline seed that subsequently guides the assembly of polyaniline due to their structural similarities. Applying this oligomer-assisted crystallization approach to polyaniline with defined molecular weights resulted in single crystalline nanowires for 5000 Da polyaniline, and nanowires with strong preferential chain orientation for those with molecular weights between 10 000 and 100 000 Da. Absorption studies reveal that the polymer chains are in an expanded conformation, which likely contributed to the high degree of packing order. Two-probe, single nanowire measurements show that the crystals have conductivity as high as 19.5 S cm −1 . This method is simple, general, and can potentially be applied to other CPs.  more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Materials Horizons
Page Range / eLocation ID:
1282 to 1291
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Polymerization‐induced self‐assembly (PISA) has emerged as a scalable one‐pot technique to prepare block copolymer (BCP) nanoparticles. Recently, a PISA process, that results in poly(l‐lactide)‐b‐poly(ethylene glycol) BCP nanoparticles coined ring‐opening polymerization (ROP)‐induced crystallization‐driven self‐assembly (ROPI‐CDSA), was developed. The resulting nanorods demonstrate a strong propensity for aggregation, resulting in the formation of 2D sheets and 3D networks. This article reports the synthesis of poly(N,N‐dimethyl acrylamide)‐b‐poly(l)‐lactide BCP nanoparticles by ROPI‐CDSA, utilizing a two‐step, one‐pot approach. A dual‐functionalized photoiniferter is first used for controlled radical polymerization of the acrylamido‐based monomer, and the resulting polymer serves as a macroinitiator for organocatalyzed ROP to form the solvophobic polyester block. The resulting nanorods are highly stable and display anisotropy at higher molecular weights (>12k Da) and concentrations (>20% solids) than the previous report. This development expands the chemical scope of ROPI‐CDSA BCPs and provides readily accessible nanorods made with biocompatible materials.

    more » « less
  2. Abstract

    Polymer crystalsomes are a class of hollow crystalline polymer nanoparticles with shells formed by single crystals with broken translational symmetry. They have shown intriguing mechanical, thermal, and biomedical properties associated with spherical packing. Previously reported crystalsomes are formed by quasi‐2D lamellae which can readily tile on a spherical surface. In this work, the formation of polymer crystalsomes formed by 1D polymer crystals is reported. Poly (3‐hexylthiophene) (P3HT) is chosen as the model polymer because of its 1D growth habit. P3HT crystalsomes are successfully fabricated using a miniemulsion solution crystallization method, as confirmed by scanning electron microscopy and transmission electron microscopy. X‐ray diffraction (XRD) and selected area electron diffraction experiments confirm that P3HT crystallized into a Form I crystal structure. XRD, differential scanning calorimetry and UV–Vis results reveal curvature‐dependent structural, thermal and electro‐optical properties.

    more » « less
  3. The nanoscale structure and macroscopic morphology of π-conjugated polymers are very important for their electronic application. While ordered single crystals of small molecules have been obtained via solution deposition, macroscopically aligned films of π-conjugated polymers deposited directly from solution have always required surface modification or complex pre-deposition processing of the solution. Here, ordered nanowires were obtained via shear-enhanced crystallization of π-conjugated polymers at the air–liquid–solid interface using simple deposition of the polymer solution onto an inclined substrate. The formation of macroscopically aligned nanowire arrays was found to be due to the synergy between intrinsic (π-conjugated backbone) and external (crystallization conditions) effects. The oriented nanowires showed remarkable improvement in the charge carrier mobility compared to spin-coated films as characterized in organic field-effect transistors (OFETs). Considering the simplicity and large-scale applicability, shear-enhanced crystallization of π-conjugated polymers provides a promising strategy to achieve high-performance polymer semiconductor films for electronics applications. 
    more » « less
  4. null (Ed.)
    In this report, we explore the internal structural features of polyMOFs consisting of equal mass ratios of metal-coordinating poly(benzenedicarboxylic acid) blocks and non-coordinating poly(ethylene glycol) (PEG) blocks. The studies reveal alternating lamellae of metal-rich, crystalline regions and metal-deficient non-crystalline polymer, which span the length of hundreds of nanometers. Polymers consisting of random PEG blocks, PEG end-blocks, or non-coordinating poly(cyclooctadiene) (COD) show similar alternation of metal-rich and metal-deficient regions, indicating a universal self-assembly mechanism. A variety of techniques were employed to interrogate the internal structure of the polyMOFs, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and small-angle synchrotron X-ray scattering (SAXS). Independent of the copolymer architecture or composition, the internal structure of the polyMOF crystals showed similar lamellar self-assembly at single-nanometer length scales. 
    more » « less
  5. Abstract

    The programmable synthesis of rationally engineered crystal architectures for the precise arrangement of molecular species is a foundational goal in nanotechnology, and DNA has become one of the most prominent molecules for the construction of these materials. In particular, branched DNA junctions have been used as the central building block for the assembly of 3D lattices. Here, crystallography is used to probe the effect of all 36 immobile Holliday junction sequences on self-assembling DNA crystals. Contrary to the established paradigm in the field, most junctions yield crystals, with some enhancing the resolution or resulting in unique crystal symmetries. Unexpectedly, even the sequence adjacent to the junction has a significant effect on the crystal assemblies. Six of the immobile junction sequences are completely resistant to crystallization and thus deemed “fatal,” and molecular dynamics simulations reveal that these junctions invariably lack two discrete ion binding sites that are pivotal for crystal formation. The structures and dynamics detailed here could be used to inform future designs of both crystals and DNA nanostructures more broadly, and have potential implications for the molecular engineering of applied nanoelectronics, nanophotonics, and catalysis within the crystalline context.

    more » « less