A new article out of Ning Yan’s lab has been published in Carbohydrate Polymers written by Mohammad H Mahaninia and Ning Yan.

Click here to obtain an e-print of the full article for free until January 5th 2023.

Abstract

This study reports a first example of chitosan-based dynamic covalent framework materials successfully prepared through one-pot/ultrasonic-assisted amidation reaction via either citric acid (CA) or trimesic acid (TMA) as the linker unit under moderate conditions. Chitosan-based framework materials with residual carboxylic acid functional groups were obtained by tripodal cross-linking reactions without the need of any catalyst. The obtained materials were capable of bond exchange via neighboring group participation (NGP) effect within their dynamic covalent networks. It was demonstrated that the chitosan-based framework materials could undergo a dynamic transamidation reaction to exhibit self-healing characteristics. The structural properties of the synthesized dynamic covalent framework materials were controlled by the type and composition of the tripodal cross-linkers. This study showcased a novel approach to synthesize biodegradable, self-healing, pH-responsive, and selective mixed-dye adsorbent materials using chitosan as the building block.

A new article out of Ning Yan’s lab has been published in the ACS Sustainable Chemistry & Engineering Journal about new sustainable packaging for Fatty Foods written by Shrestha Roy Goswami, Sandeep Sudnakaran Nair, Xiao Zhang, Nicolas R. Tanguy, and Ning Yan.

Click here to obtain an e-print of the full article for free for the first 50 people within the next year.

Abstract

The commercial marketability of polylactic acid (PLA) food packaging films is limited by their poor ductility and biodegradation ability. To address these challenges, a high-DS amylose-rich corn starch maleate (SM)/epoxidized soybean oil (ESO)/PLA composite film was developed. The film demonstrated significant ductility improvement (elongation at break increased from ≈3.63 to 36.75% while the tensile toughness improved 15-fold compared to the neat PLA film) because of improved interfacial interactions and mobility of ESO-plasticized PLA chains. Furthermore, due to absence of voids, the SM/ESO/PLA film also outperformed the ESO/PLA film in terms of oxygen (23,140 cm³ μm m^–2 day^–1 Pa^–1) and water vapor (0.03 × 10^–5 g m^–1 day^–1 Pa^–1) barrier performances. These characteristics, together with findings that the SM/ESO/PLA film could rapidly breakdown in saline water (2.92 wt % per day) and compost (the C/N ratio increased from 20.4 to 22.69), as well as absence of ESO migration in fatty food simulants, make the SM/ESO/PLA film a promising material for food packaging.

A new article out of Ning Yan’s lab has been published in the Chemical Engineering Journal about a self-strengthening, recyclable, starch-based epoxy vitrimer written by Nicole Tratnik, Nicolas R. Tanguy, and Ning Yan.

Click here to view the full article for free until October 5th, 2022.

Abstract

Epoxy vitrimers have emerged as a new class of self-healing, recyclable, and reprocessable materials, offering new opportunities to traditional epoxy thermosets by improving life-span, while providing additional functionalities. Nevertheless, retaining 100 % of the original mechanical performances remains difficult for vitrimers after several reprocessing cycles due to progressive changes in the vitrimer networks during rearrangements. In this study, we designed a novel epoxy vitrimer with a higher renewable content compared to conventional epoxies by using renewable materials. The bio-based epoxy vitrimer was synthesized from epoxidized starch amylopectin together with diallyl disulfide, that is naturally found in garlic, and a thiol (pentaerythritol tetrakis(3-mercaptopropionate) (PETMP)). Diallyl disulfide and PETMP enabled the formation of a recyclable, and reprocesseable, vitrimer network. The epoxy vitrimer displayed unprecedented self-strengthening after 5 recycling cycles (tensile strength increased over 900 %) caused by the mechanically-induced homogeneization of the diallyl disulfide/thiol and the starch epoxy ghost granule phases during the recycling process, thereby increasing the vitrimer cross-linking density during reformation. Reprocessing the vitrimer 5-times improved the mechanical and thermal properties, raising glass transition temperature, Young’s modulus, and tensile strength from 7 °C to 25 °C, 2.98 MPa to 268 MPa, and 1.87 MPa to 18.47 MPa, respectively. Hence, capitalizing on mechanically-induced phase homegeneization during the vitrimer reprocessing, this work introduces a strategy for the design of self-strengthening bio-based and recyclable thermosets.

A new article out of Ning Yan’s lab has been published in Nano Energy about lignocellulosic nanofibrils used in triboelectric nanogenerators written by Nicolas R. Tanguy, Masud Rana, Asif A. Khan, Nicole Tratnik, Heyu Chen, Dayan Ban and Ning Yan.

Click here to view the full article for free until June 24, 2022.

Abstract

Triboelectric nanogenerators (TENGs) are promising energy harvesting devices for powering next generation wearable electronics. TENGs performance are largely determined by the triboelectric effect between the tribonegative and tribopositive layers. To date, fluorine-containing petroleum-based polymers, such as polytetrafluoroethylene (PTFE), remain the most popular choice as tribonegative layer due to their high tribonegativity against various materials during frictional contact. We report for the first time a natural wood-derived lignocellulosic nanofibrils (LCNF) tribolayer that could replace fluorine-containing petroleum-based polymers as a tribonegative material for TENGs. The high tribonegativity was due to the presence of natural lignin on the surface of LCNF and LCNF’s nanofibril morphology. The LCNF nanopaper-based TENGs produced significantly higher voltage (~160%) and current (~120%) than TENGs with PTFE as the tribonegative material when paired with various polymeric/metallic tribolayers. Furthermore, assembling LCNF nanopaper as the tribonegative layers into a cascade TENG generated an output sufficient for powering a wireless communication node, capable of sending a radio-frequency signal to a smartphone every 3 min. This study demonstrates the excellent promises of using LCNF to make high-performance and more environmentally friendly wireless self-powered electronics; and thus pinpoints a new approach for fabricating sustainable triboelectric nanogenerators using natural lignocellulosic materials instead of conventional fluorine-containing petroleum-based polymers as tribonegative layers.

A new article out of Ning Yan’s lab has been published in the International Journal of Biological Macromolecules about functionalized lignin nanoparticles written by Hetian, Fangeng Chen, Wenxiang Zhu and Ning Yan.

Click here to view the full article for free until June 16, 2022.

Abstract
There is a strong interest in developing environmentally friendly synthesis approaches for making polyurethane elastomers (PUE) with desirable mechanical performance and flame retardancy suitable for a variety of applications. Hence, in this study, a novel nano functionalized lignin nanoparticle (Nano-FL) containing nitrogen (N) and phosphorus (P) moieties was developed via mild grafting reactions combined with the ultrasound method. The Nano-FL incorporated in the PUE acted as both crosslinking agents and flame retardants. The novel Nano-FL showed good compatibility and dispersibility in the PUE matrix, thereby overcoming the weakening effect of adding traditional lignin flame retardants on the mechanical properties of the PUE materials. PUE/Nano-FL exhibited strong tensile properties. Compared with control neat PUE, with 10 wt% of Nano-FL addition, the PUE attained a limiting oxygen index as high as 29.8% and it also passed the UL-94 V-0 rating. Furthermore, Cone Calorimetry Test (CCT) showed that the addition of Nano-FL not only reduced the heat release rate and the total heat release but also decreased the total smoke production rate during combustion. The char residues of PUEs with Nano-FL showed a high oxidation resistance with dense and continuous structural morphologies. The combined barrier and quenching effects of the char layer provided excellent flame retardancy performance. The novel Nano-FL developed in this study showed excellent promises as green functional additives for enhancing mechanical, thermal and flame retardancy performance of a wide range of polymers.