Yingfeng Tu

Well-Dispersed Chitosan/Graphene Oxide Nanocomposites

Nanocomposites of chitosan and graphene oxide are prepared by simple self-assembly of both components in aqueous media. It is observed that graphene oxide is dispersed on a molecular scale in the chitosan matrix and some interactions occur between chitosan matrix and graphene oxide sheets. These are responsible for efficient load transfer between the nanofiller graphene and chitosan matrix. Compared with the pure chitosan, the tensile strength, and Youngs modulus of the graphene-based materials are significantly improved by about 122 and 64%, respectively, with incorporation of 1 wt % graphene oxide. At the same time, the elongation at the break point increases remarkably. The experimental results indicate that graphene oxide sheets prefer to disperse well within the nanocomposites.

A Porphyrin–Fullerene Dyad with a Supramolecular “Double‐Cable” Structure as a Novel Electron Acceptor for Bulk Heterojunction Polymer Solar Cells

Bulk heterojunction (BHJ) polymer solar cells (PSCs) offer a promising, low-cost, large-area, fl exible, light-weight, clean, and quiet alternative energy source for both indoor and outdoor applications. [ 1–4 ] Power conversion effi ciencies (PCEs) in response to solar AM1.5 radiation as high as 6–8% have been reported for BHJ PSCs. [ 5 , 6 ] In order to achieve PCEs over 10%, BHJ materials capable of generating higher short circuit current ( J sc ) and larger open circuit voltage ( V oc ) are required. [ 7 , 8 ]

Hierarchical structure and polymorphism of a sphere-cubic shape amphiphile based on a polyhedral oligomeric silsesquioxane–[60]fullerene conjugate

A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct symmetry ([60]fullerene (C60) and polyhedral oligomeric silsesquioxane (POSS)) was synthesized and its solid state structures were characterized. The two types of nanoparticles are known to be generally immiscible, but they were connected with a short covalent linkage forming an organic–inorganic dyad (POSS–C60) which exhibited interesting crystallization characteristics. Crystals of the dyad exhibited polymorphism with two different crystal structures: an orthorhombic and a hexagonal unit cell with symmetry groups of P21212 and P6, respectively, both of which formed an alternating bi-layered structure of POSS and C60. The different symmetry groups in the polymorphs were attributed to the different packing orientations of the POSS within each layer. In the orthorhombic unit cell, one set of the edges of the POSS moieties is parallel to the c-axis; while in the hexagonal unit cells the body-diagonal is parallel to the c-axis of the crystal. Based on the crystal packing structure and density differential, it has been determined that the hexagonal unit cell structure is the more thermodynamically stable phase. This type of bi-layered structure with an alternating conductive fullerene and insulating POSS layer structure is of great interest for various potential applications such as nano-capacitors.

Supramolecular [60]Fullerene Liquid Crystals Formed By Self-Organized Two-Dimensional Crystals†

Fullerene-based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self-organization and external-field-responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self-organization driven by π-π interactions to form triple-layer two-dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals.

Acceptor–donor–acceptor-based small molecules with varied crystallinity: processing additive-induced nanofibril in blend film for photovoltaic applications

A series of acceptor-donor-acceptor-based small molecules (SMs) with varied crystallinity were successfully synthesized. The processing additive can induce the SMs to self-organize as nanofibrils with higher crystallinity and controlled scales of nanofibrils, which have significant influence on the photovoltaic performance.

One pot synthesis and characterization of novel poly(ether ester) mutiblock copolymers containing poly(tetramethylene oxide) and poly(ethylene terephthalate)

We demonstrate here a novel method to synthesize poly(ethylene terephthalate)-block-poly(tetramethylene oxide) multiblock copolymers (PET-b-PTMO-b-PET)x by the one pot melt polymerization of cyclic oligo(ethylene terephthalate)s (COETs) using poly(tetramethylene oxide) (PTMO) as a macroinitiator. Two-dimensional and one-dimensional nuclear magnetic resonance (2D and 1D-NMR) techniques, including 1H–13C Heteronuclear Single Quantum Coherence (HSQC) and 1H–1H Correlation Spectroscopy (COSY), have been used to characterize and reveal the multiblock copolymer structures and absolute molecular weights. It was found that the COETs were consumed completely within 15 minutes, and the molecular weights of the block copolymers increased linearly with reaction time. Based on the polymerization kinetic studies, a two-stage polymerization mechanism is proposed: the ring-opening polymerization of COETs by a PTMO macroinitiator to PET-b-PTMO-b-PET triblock copolymers at the first stage, followed by the in situ condensation polymerization of triblock copolymers to (PET-b-PTMO-b-PET)x multiblock copolymers at the second stage. The structures of the multiblock copolymers are further characterized and confirmed by viscometry and gel permeation chromatography (GPC). These multiblock copolymers show improved thermal stability when compared to PTMO homopolymers, and double crystalline properties from PTMO and PET segments, as revealed by thermogravimetric analysis and differential scanning calorimetry, respectively.

A supramolecular structure with an alternating arrangement of donors and acceptors constructed by a trans-di-C60-substituted Zn porphyrin derivative in the solid state

When a molecule is constructed from geometrically isotropic [such as [60]fullerene (C60)] and anisotropic (such as porphyrin) units, as in the case of a trans-di-C60-substituted Zn porphyrin derivative (diZnCPD), great interest lies in the understanding of their individual contributions to structural formations and phase transitions. For this purpose, the compound, diZnCPD, was designed and synthesized. Its phase behavior was investigated viadifferential scanning calorimetry (DSC) and polarized light optical microscopy (POM) and its supramolecular structure was elucidated viawide-angle X-ray diffraction (WAXD) and selective area electron diffraction (SAED) in transmission electron microscopy (TEM). The diZnCPD possesses a polymorphism in its ordered structures. When cooled from the isotropic (I) phase with experimentally accessible rates, instead of transferring into its ultimate stable phase, this compound formed a less ordered, metastable phase with a layered structure at 152 °C. Annealing this metastable phase enabled a further transformation into a stable phase with a higher transition temperature. As such, this metastable phase is monotropic. The formation of the stable phase was thus thermodynamically favorable, but kinetically more difficult (with a higher barrier for the transformation). Direct formation of this stable phase from the I state was unsuccessful even after prolonged isothermal experiments over several days above 152 °C, indicating that the formation barrier of this stable phase is extremely high. The thermally stable phase possessed a supramolecular structure with a triclinic unit cell of a = 3.34 nm, b = 2.01 nm, c = 1.88 nm, α = 89°, β = 98°, and γ = 90°. Detailed structural analysis revealed that this is a donor–acceptor separated structure of C60s and porphyrins nearly along the [01] direction within which the zig-zag shaped C60 channels are along the [001] direction of the unit cell. We believe this is the first example of generating a donor–acceptor separated structure of C60s and porphyrins in the bulk through a thermal annealing process. This structure provides promising potential for the use of this material to fabricate supramolecular electronic devices without utilizing a solvent process.

A fullerene dyad with a tri(octyloxy)benzene moiety induced efficient nanoscale active layer for the poly(3-hexylthiophene)-based bulk heterojunction solar cell applications

A bulk tri(octyloxy)benzene moiety grafted onto fullerene (PCBB-C8) was successfully synthesized, which could effectively induce poly(3-hexylthiophene) (P3HT) to form highly ordered bulk heterojunction structure without any external treatment. This ordered active layer exhibits good photovoltaic performance.

Synergistic toughening of bioinspired artificial nacre by polystyrene grafted graphene oxide

A biologically inspired, multilayer laminate structural design is deployed in composite films of polystyrene (PS) grafted graphene oxide (GO) synthesized by a Ce(IV)/HNO3 redox system in aqueous solution. Artificial hybrid films are fabricated using a vacuum-assisted filtration macroscopic assembly method, using nacre as the structural model, GO as the inorganic building blocks and PS as glue. The resulting multilayer structure and the mechanical properties of the nanopaper were studied by scanning electron microscopy, X-ray diffraction and stress–strain measurements. The resulting multilayer GO–PS films with low polymer content (<15 vol%) show greatly enhanced mechanical properties compared to pure GO films. It is interesting that the mechanical properties of the nacre-like films can be varied with the volume fraction of the polymer.

Side-chain fullerene polyesters: a new class of high refractive index polymers

By introducing flexible spacers between pendant fullerenes and the backbone, side-chain fullerene polyesters with high fullerene content and good solubility were synthesized by condensation polymerization. These polyesters are a new class of soluble high refractive index polymers (HRIPs) with the highest value of 1.79 at the sodium D line (589 nm).