Chaowei Feng

Semiconducting Conjugated Polymer–Inorganic Tetrapod Nanocomposites

Cadmium telluride (CdTe) tetrapods were synthesized via multiple injections of the Te precursor by utilizing bifunctional ligands. Subsequently, tetrapod-shaped semiconducting inorganic-organic nanocomposites (i.e., P3HT-CdTe tetrapod nanocomposites) were produced by directly grafting conjugated polymer ethynyl-terminated poly(3-hexylthiophene) (i.e., P3HT-≡) onto azide-functionalized CdTe tetrapods (i.e., CdTe-N3) via a catalyst-free click chemistry. The intimate contact between P3HT and CdTe tetrapod rendered the effective dispersion of CdTe tetrapods in nanocomposites and facilitated their efficient electronic interaction. The success of coupling reaction was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafting density of P3HT chains on the CdTe tetrapods was estimated by thermogravimetric analysis. The photophysical properties of P3HT-CdTe tetrapod nanocomposites were studied using UV-vis and photoluminescence spectroscopies. These intimate semiconducting conjugated polymer-tetrapod nanocomposites may offer a maximized interface between conjugated polymers and tetrapods for efficient charge separation and enhanced charge transport regardless of their orientation for potential application in hybrid solar cells with improved power conversion efficiency.

A versatile strategy for uniform hybrid nanoparticles and nanocapsules

A viable strategy for uniform organo-silica hybrid nanoparticles and nanocapsules was developed. The key to our strategy is the implementation of spherical star-like homopolymers and diblock copolymers with well-controlled molecular weights that form unimolecular micelles in solution as nanoreactors. Organo-silica hybrid nanoparticles were crafted by introducing trimethoxysilyl functionalities to the arm of star-like homopolymers. Quite intriguingly, organo-silica hybrid nanocapsules with an interior cavity were created when the trimethoxysilyl moieties were incorporated into the outer block of star-like diblock copolymers. The diameter of hybrid nanoparticles and the shell thickness of hybrid nanocapsules can be readily tailored via the living polymerization of star-like homopolymer and diblock copolymer nanoreactors, respectively. These hybrid nanoparticles and nanocapsules may find promising applications in polymer nanocomposites, water purification, separation, catalysis, and drug delivery. We envision that the nanoreactor strategy is general and robust. By rationally designing nonlinear yet structurally regular polymers possessing metal-containing units, other exotic metal- and metal oxide-containing nanostructures can also be easily accessed for a variety of applications.

Unimolecular micelles composed of inner coil-like blocks and outer rod-like blocks crafted by combination of living polymerization with click chemistry

A new class of star-shaped coil–rod diblock copolymer polystyrene-block-poly(3-hexylthiophene) (PS-b-P3HT) with well-defined structures and the ratio of coil to rod blocks were synthesized by a combination of atom transfer radical polymerization, the Grignard metathesis method, and click reaction. The star-shaped PS-b-P3HT diblock copolymers covalently connected to a β-cyclodextrin (β-CD) core were composed of 21-arm coil-like PS inner blocks and rod-like conjugated polymer P3HT outer blocks with narrow molecular weight distribution. The intermediate and final products were systematically characterized and confirmed by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (1H-NMR), and Fourier transfer infrared (FTIR) spectroscopy. The optical properties of star-shaped PS-b-P3HT were examined by UV-Vis absorption and photoluminescence (PL) measurements. In comparison to the linear P3HT, due to their compact structure and the introduction of PS blocks, the optical properties of 21-arm, star-shaped PS-b-P3HT were altered. The star-shaped PS-b-P3HT formed unimolecular micelles in good solvent as revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) studies.

Functional copolymer brushes composed of a hydrophobic backbone and densely grafted conjugated side chains via a combination of living polymerization with click chemistry

A series of well-defined copolymer brushes, PS-g-P3HT, composed of a hydrophobic coil-like PS backbone and densely grafted rod-like P3HT side chains were successfully synthesized by a combination of the quasi-living Grignard metathesis (GRIM) method, reversible addition–fragmentation chain transfer (RAFT), and click reaction. The molecular weight distribution of the resulting PS-g-P3HT copolymer brushes was rather narrow (polydispersity index, PDI 96%). The self-assembly of PS-g-P3HT at the air/water interface was explored using the Langmuir–Blodgett (LB) technique. Quite intriguingly, circular domain arrays composed of the non-crystallized P3HT nanofibers were observed at high surface pressure.

Self-assembly of a conjugated triblock copolymer at the air–water interface

Controlling the self-assembly of highly luminescent conjugated polymers is essential for preparing various optoelectronic devices. In this study, a polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) (PI-PS-P3HT) triblock copolymer was synthesized and readily self-assembled into network-like morphologies via dewetting at the air–water interface. Interestingly, the monolayer thick film displayed high photoluminescence (PL) as a result of successfully transferring the amorphous conjugated P3HT chains in the PI-PS-P3HT triblock copolymer from the solution state to the solid state. A model was proposed to illustrate the supramolecular organization of the PI-PS-P3HT monolayer. To the best of our knowledge, this is the first study of a hydrophobic conjugated block copolymer at the air–water interface, from which the conjugated polymer-based monolayer with highly efficient PL formed by dewetting was achieved.

Unconventional Route to Uniform Hollow Semiconducting Nanoparticles with Tailorable Dimensions, Compositions, Surface Chemistry and Near-Infrared Absorption

Despite impressive recent advances in the synthesis of lead chalcogenide solid nanoparticles, there are no examples of lead chalcogenide hollow nanoparticles (HNPs) with controlled diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with their complexity, inability to precisely control the dimensions, and limited possibilities with regard to applicable materials. Herein, we report on an unconventional strategy for crafting uniform lead chalcogenide (PbS and PbTe) HNPs with tailorable size, surface chemistry, and near-IR absorption. Amphiphilic star-like triblock copolymers [polystyrene-block-poly(acrylic acid)-block-polystyrene and polystyrene-block-poly(acrylic acid)-block-poly(3,4-ethylenedioxythiophene)] were rationally synthesized and exploited as nanoreactors for the formation of uniform PbS and PbTe HNPs. Compared to their solid counterparts, the near-IR absorption of the HNPs is blue-shifted owing to the hollow interior. This strategy can be readily extended to other types of intriguing low-band-gap HNPs for diverse applications.