Polymers zippered-up by electric charge reveal themselves

Cylindrical Zwitterionic Particles via Interpolyelectrolyte Complexation on Molecular Polymer Brushes

The fabrication of macromolecular architectures with high aspect ratio and well-defined internal and external morphologies remains a challenge. The combination of template chemistry and self-assembly concepts to construct peculiar polymer architectures via a bottom-up approach is an emerging approach. In this study, a cylindrical template-namely a core-shell molecular polymer brush-and linear diblock copolymers (DBCP) associate to produce high aspect ratio polymer particles via interpolyelectrolyte complexation. Induced, morphological changes are studied using cryogenic transmission electron and atomic force microscopy, while the complexation is further followed by isothermal titration calorimetry and ξ-potential measurements. Depending on the nature of the complexing DBCP, distinct morphological differences can be achieved. While polymers with a non-ionic block lead to internal compartmentalization, polymers featuring zwitterionic domains lead to a wrapping of the brush template.

Two-Step Assembly of Thermoresponsive Gold Nanorods Coated with a Single Kind of Ligand

Gold nanorods (GNRs) coated with a single kind of ligand show thermoreponsive two-step assembly to provide a hierarchical structure. The GNRs (33 nm in length × 14 nm in diameter) coated with a hexa(ethylene glycol) (HEG) derivative form side-by-side assemblies at 30 °C (T_A1 ) as a steady state through dehydration. By further heating to over 40 °C (T_A2 ), larger assemblies, which are composed of the side-by-side assembled units, are formed as hierarchical structures. The dehydration temperature of the HEG derivative varies depending on the free volume of the HEG unit, which corresponds to the curvature of the GNRs. Upon heating, dehydration first occurs from the ligands on the side portions with a lower curvature, and then from the ligands on the edge portions with a higher curvature. The different sized GNRs (33 × 8 and 54 × 15 nm) also show two-step assembly. Both the T_A1 and T_A2 are dependent on the diameter of the GNRs, but independent of their length. This result supports that the dehydration is dependent on the free volume, which corresponds to the curvature. Anisotropic assembly focusing on differences in curvature provides new guidelines for the fabrication of hierarchical structures.

Expanding the Cationic Polycarbonate Platform: Attachment of Sulfonium Moieties by Postpolymerization Ring Opening of Epoxides

Postpolymerization modification is a critical strategy for the development of functional polycarbonate scaffolds for medicinal applications. To expand the scope of available postpolymerization functionalization methods, polycarbonates containing pendant thioether groups were synthesized by organocatalyzed ring-opening polymerization. The thioether group allowed for the postpolymerization ring-opening of functional epoxides, affording a wide variety of sulfonium-functionalized A-B diblock and A-B-A triblock polycarbonate copolymers. The pendant thioether groups were found to be compatible with previously developed postsynthesis functionalization methods allowing for selective and orthogonal modifications of the polycarbonates.

Rod-Like Nanoparticles with Striped and Helical Topography

The behavior of nanoparticles in solution is largely dominated by their shape and interaction potential. Despite considerable progress in the preparation of patchy and compartmentalized particles, access to nanoparticles with complex surface patterns and topographies remains limited. Here, we show that polyanionic brushes tethered to rod-like cellulose nanocrystals (CNCs) spontaneously develop a striped or helical topography through interpolyelectrolyte complexation with polycationic diblock copolymers. Using cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET), we follow the complexation process and analyze the delicate 3D topography on the CNC surface. The described approach is facile and modular and can be extended to other block chemistries, nanoparticles, and surfaces, thereby providing a versatile platform toward surface-patterned particles with complex topographies and spatially arranged functional groups.

Supramolecular core-shell nanoparticles for photoconductive device applications

We report a breakthrough discovery involving supramolecular-based strategies to construct novel core-shell heterojunction nanoparticles with hydrophilic adenine-functionalized polythiophene (PAT) as the core and hydrophobic phenyl-C61-butyric acid methyl ester (PCBM) as the shell, which enables the conception of new functional supramolecular assemblies for constructing functional nanomaterials for applications in optoelectronic devices. The generated nanoparticles exhibit uniform spherical shape, well-controlled tuning of particle size with narrow size distributions, and excellent electrochemical stability in solution and the solid state owing to highly efficient energy transfer from PAT to PCBM. When the PAT/PCBM nanoparticles were fabricated into a photoconducting layer in an electronic device, the resulting device showed excellent electric conduction characteristics, including an electrically-tunable voltage-controlled switch, and high short-circuit current and open-circuit voltage. These observations demonstrate how the self-assembly of PAT/PCBM into specific nanostructures may help to promote efficient charge generation and transport processes, suggesting potential for a wide variety of applications as a promising candidate material for bulk heterojunction polymer devices.

Supramolecular polyelectrolyte complex (SPEC): pH dependent phase transition and exploitation of its carrier properties

A supramolecular poly-electrolyte complex (SPEC) comprising poly-electrolyte acrylic acid with supramolecularly complexed guanidium is reported. This complex shows pH responsive phase transitions, which are described and characterized using microscopy, spectroscopy, density functional theory studies and Monte Carlo simulations. The phase behaviour of the SPEC is exploited by loading a dye like perylene and a drug, viz., doxorubicin, and their pH dependent controlled release is demonstrated, owing to the pH dependent phase change of the SPEC.