Ngoc A. Nguyen

New Infrared Transmitting Material via Inverse Vulcanization of Elemental Sulfur to Prepare High Refractive Index Polymers

Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 μm) and mid-IR (3-5 μm) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated.

Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li–S batteries

High sulfur content copolymers were prepared via inverse vulcanization of sulfur with 1,4-diphenylbutadiyne (DiPhDY) for use as the active cathode material in lithium–sulfur batteries. These sulfur-rich polymers exhibited excellent capacity retention (800 mA h g−1 at 300 cycles) and extended battery lifetimes of over 850 cycles at C/5 rate.

Multivalency in healable supramolecular polymers: the effect of supramolecular cross-link density on the mechanical properties and healing of non-covalent polymer networks

Polymers with the ability to heal themselves could provide access to materials with extended lifetimes in a wide range of applications such as surface coatings, automotive components and aerospace composites. Here we describe the synthesis and characterisation of two novel, stimuli-responsive, supramolecular polymer blends based on π-electron-rich pyrenyl residues and π-electron-deficient, chain-folding aromatic diimides that interact through complementary π–π stacking interactions. Different degrees of supramolecular “cross-linking” were achieved by use of divalent or trivalent poly(ethylene glycol)-based polymers featuring pyrenyl end-groups, blended with a known diimide–ether copolymer. The mechanical properties of the resulting polymer blends revealed that higher degrees of supramolecular “cross-link density” yield materials with enhanced mechanical properties, such as increased tensile modulus, modulus of toughness, elasticity and yield point. After a number of break/heal cycles, these materials were found to retain the characteristics of the pristine polymer blend, and this new approach thus offers a simple route to mechanically robust yet healable materials.

Syringyl Methacrylate, a Hardwood Lignin-Based Monomer for High-Tg Polymeric Materials

As viable precursors to a diverse array of macromolecules, biomass-derived compounds must impart wide-ranging and precisely controllable properties to polymers. Herein, we report the synthesis and subsequent reversible addition–fragmentation chain-transfer polymerization of a new monomer, syringyl methacrylate (SM, 2,6-dimethoxyphenyl methacrylate), that can facilitate widespread property manipulations in macromolecules. Homopolymers and heteropolymers synthesized from SM and related monomers have broadly tunable and highly controllable glass transition temperatures ranging from 114 to 205 °C and zero-shear viscosities ranging from ∼0.2 kPa·s to ∼17,000 kPa·s at 220 °C, with consistent thermal stabilities. The tailorability of these properties is facilitated by the controlled polymerization kinetics of SM and the fact that one vs two o-methoxy groups negligibly affect monomer reactivity. Moreover, syringol, the precursor to SM, is an abundant component of depolymerized hardwood (e.g., oak) and graminaceous (e.g., switchgrass) lignins, making SM a potentially sustainable and low-cost candidate for tailoring macromolecular properties.

A comparative study on the morphology of P3HT:PCBM solar cells with the addition of Fe 3 O 4 nanoparticles by spin and rod coating methods

Our previous study presented up to 20% power conversion efficiency (PCE) enhancement of poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) solar cells under the Fe3O4 nanoparticles (NPs) self-assembly (SA) effect by spin coating. Fe3O4 NPs (about 11 nm hydrodynamic diameter) form a thin layer at the top interface of the light absorbing active layer, which results in the generation of PCBM rich region improving the charge transport (Zhang et al. Sol Energ Mat Sol C 160:126–133, 2017). In order to investigate the feasibility of this Fe3O4 NPs SA effect under large-scale production condition, a smooth rod was implemented to mimic roll-to-roll coating technique and yield active layers having about the same thickness as the spin-coated ones. Small angle neutron scattering and grazing incidence X-ray diffraction were employed finding out similar morphologies of the active layers by these two coating techniques. However, rod-coated solar cell’s PCE decreases with the addition of Fe3O4 NPs compared with the one without them. This is because PCBM rich region is not created at the top interface of the active layer due to the absence of Fe3O4 NPs, which is attributed to the weak convective flow and low diffusion rate. Moreover, in the rod-coated solar cells, the presence of Fe3O4 NPs causes decrease in P3HT crystallinity, thus the charge transport and the device performance. Our study confirms the role of spin coating in the Fe3O4 NPs SA effect and enables researchers to explore this finding in other polymer nanocomposite systems.

Mechanical, thermal, morphological, and rheological characteristics of high performance 3D-printing lignin-based composites for additive manufacturing applications

The article presents different mechanical, thermal and rheological data corresponding to the morphological formation within various renewable lignin-based composites containing acrylonitrile butadiene styrene (ABS), acrylonitrile butadiene rubber (NBR41, 41 mol% nitrile content), and carbon fibers (CFs). The data of 3D-printing properties and morphology of 3D-printed layers of selected lignin-based composites are revealed. This data is related to our recent research article entitled “A general method to improve 3D-printability and inter-layer adhesion in lignin-based composites” (Nguyen et al., 2018 [1]).

The effect of nanoparticle enhanced sizing on the structural health monitoring sensitivity and mechanical properties of carbon fiber composites

With current carbon composites being introduced into new commercial market sectors, there is an opportunity to develop multifunctional composites, which are poised to be the next generation of composites that will see future commercial applications. This multifunctional attribute can be achieved via integrated nanomaterials, which are currently under-utilized in real-world applications despite significant research efforts focused on their synthesis. This research utilizes a simple, scalable approach to integrate various nanomaterials into carbon fiber composites by embedding the nanomaterials in the epoxy fiber sizing. Illustrated in this work is the effect of silicon carbide nanoparticle concentrations and dimensions on the structural health monitoring sensitivity of unidirectional carbon fiber composites. Additionally, the nanoparticles contribute to the overall damping property of the composites thus enabling tunable damping through simple variations in nanoparticle concentration and size. Not only does this nanoparticle sizing offer enhanced sensitivity and tunable damping, but it also maintains the mechanical integrity and performance of the composites, which demonstrates a truly multifunctional composite. Therefore, this research establishes an efficient route for combining nanomaterials research with real-world multifunctional composite applications using a technique that is easily scalable to the commercial level and is compatible with a wide range of fibers and nanomaterials.

A Solvent‐Free Synthesis of Lignin‐Derived Renewable Carbon with Tunable Porosity for Supercapacitor Electrodes

Synthesis of multiphase materials from lignin, a biorefinery coproduct, offers limited success owing to the inherent difficulty in controlling dispersion of these renewable hyperbranched macromolecules in the product or its intermediates. Effective use of the chemically reactive functionalities in lignin, however, enables tuning morphologies of the materials. Here, we bind lignin oligomers with a rubbery macromolecule followed by thermal crosslinking to form a carbon precursor with phase contrasted morphology at submicron scale. The solvent-free mixing is conducted in a high-shear melt mixer. With this, the carbon precursor is further modified with potassium hydroxide for a single-step carbonization to yield activated carbon with tunable pore structure. A typical precursor with 90 % lignin yields porous carbon with 2120 m2  g-1 surface area and supercapacitor with 215 F g-1 capacitance. The results show a simple route towards manufacturing carbon-based energy-storage materials, eliminating the need for conventional template synthesis.

Roll-to-Roll Processing of Silicon Carbide Nanoparticle-Deposited Carbon Fiber for Multifunctional Composites

This work provides a proof of principle that a high volume, continuous throughput fiber coating process can be used to integrate semiconducting nanoparticles on carbon fiber surfaces to create multifunctional composites. By embedding silicon carbide nanoparticles in the fiber sizing, subsequent composite fabrication methods are used to create unidirectional fiber-reinforced composites with enhanced structural health monitoring (SHM) sensitivity and increased interlaminar strength. Additional investigations into the mechanical damping behavior of these functional composites reveal a significantly increased loss factor at the glass-transition temperature ranging from a 65 to 257% increase. Composites with both increased interlaminar strength and SHM sensitivity are produced from a variety of epoxy and silicon carbide nanoparticle concentrations. Overall, the best performing composite in terms of combined performance shows an increase of 47.5% in SHM sensitivity and 7.7% increase in interlaminar strength. This work demonstrates successful and efficient integration of nanoparticle synthesis into large-scale, structural applications.