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.

A new article out of Ning Yan’s lab has been published in Carbohydrate Polymers about anisotropic cellulose nanocrystal hydrogel written by Liu Liu, Nicolas R.Tanguy, Ning Yan, Yiqiang Wu, Xiubo Liu, and Yan Qing

Click here to view the full article.

Abstract

Conventional hydrogels with isotropic polymer networks usually lack selective response to external stimuli and that limits their applications in intelligent devices. Herein, hydrogels with distinctive anisotropic optical characteristics combined with thermosensitivity were prepared through in situ photopolymerization. Self-assembled cellulose nanocrystals (CNCs) with chiral nematic ordered structure were embedded in polyethylene glycol derivatives/polyacrylamide polymer networks. The arrangement of CNCs showed a strong dependence on the self-assembly angle and standing time, enabling the fabrication of hydrogels with customizable CNCs arrangements. Increasing the self-assembly angle from 0° to 90° changed the CNCs arrangement from chiral nematic to symmetrical nematic order which, together with CNCs dynamic arrangement from isotropic to annealed chiral nematic phase at longer standing time, provided versatile ways to produce CNCs hydrogels with tunable anisotropic properties. In addition, the obtained hydrogel displayed reversible temperature and compression response, showing excellent promise to be used as soft mechanical stress and temperature sensors or novel anti-counterfeiting materials.

A new review article out of Ning Yan’s lab has been published in ACS Sustainable Chemistry & Engineering about the progress on startch maleats and polylactic acid blends for food packaging written by Shrestha Roy Goswami, Sandeep Sudhakaran Nair, Sen Wang, and Ning Yan

For the first 12 months of publication, 50 free e-prints are available for interested colleagues.
Click here to see the article and get your free e-print.

Abstract

Starch maleate/polylactic acid blends could replace polyethylene terephthalate in food packaging films. These films, however, are not acceptable for commercial use due to their poor performance, which is caused by processing polylactic acid with starch maleates having a low degree of maleic anhydride substitutions (DS_NMR < 0.1 or DS_titration < 1). Conventionally produced starch maleates produced via dry grinding or as aqueous and nonaqueous dispersions acquire a low DS due to the presence of inactive hydroxyl and maleic anhydride groups in each of the reaction systems. Low-DS starch maleates could barely interact with polylactic acid and plasticizers during blend processing; consequently, the resultant films perform poorly in terms of ductility and compostability. The key findings of this perspective indicate that recyclable ionic liquids like 1-allyl-3-methylimidazolium chloride could disrupt H-bonds among hydroxyls of starch and catalyze in situ maleic anhydride ring openings to provide functional groups for the synthesis of high-DS starch maleates (DS_NMR ≥ 0.1 or DS_titration ≥ 1). Improved interfacial chain interactions between high-DS starch maleates/polylactic acid and plasticizers like epoxidized soybean oil could facilitate stress-transfer and enzymatic activities of the resultant film, potentially improving its ductility and compostable properties. Besides these promising findings, this perspective also emphasizes the need for further research into identifying a wide range of ionic liquids and compostable plasticizers for producing high-DS starch maleates/polylactic acid blends, assessing the effect of interfacial chain interactions on properties of the resultant film, and determining specific usage of the film based on the barrier properties measured using standardized techniques.

A new article out of Ning Yan’s lab has been published in Composites Part B: Engineering written by Pitchaimari Gnanasekar, Heyu Chen, Nicole Tratnik, Martin Feng and Ning Yan.

Click here to view the full article.

Abstract

            In this study, non-covalently functionalized graphene oxide (FGO) containing phosphorus and nitrogen was synthesized using dibenzyl N,N’-diethyl phosphoramidite (DDP)via a single step process. Meanwhile, novel bio-based phosphorus containing vanillin epoxy resin (VPE) was made via a two-step process and used as a flame-retardant adhesive. Subsequently, FGO was dispersed in the epoxy resin matrix at different weight ratios as reinforcement for improving mechanical, thermal and flame-retardant properties of the resultant composite systems. Curing behavior of the VPE and FGO mixtures with 4,4’-diaminodiphenylsulfone (DDS) as the crosslinker was investigated using a Differential Scanning Calorimeter (DSC). Thermal and flame-retardant properties of the cured VPE/FGO nanocomposites were systematically investigated by Thermogravimetric Analysis (TGA), Gas Chromatography – Mass Spectrometry (GC-MS), Limited Oxygen Index (LOI), vertical burning test (UL-94), and cone calorimeter test. Results indicated that all VPE/FGO nanocomposites exhibited excellent thermal and flame-retardant properties. In particular, VPE with 9wt% of FGO achieved the highest LOI value (29.1%) and passed the V-0 rating in the UL-94 test. Furthermore, cone calorimetry test showed that flame retardancy performance of the VPE and VPE/FGO composites significantly improved compared to vanillin epoxy control resin without phosphorus. The gaseous and high boiling pyrolysis products of VPE cured by DDS were collected and characterized by GC/MS to reveal their formation mechanisms. The char layers of the cued VPE showed a high oxidation resistance with intumescent structures. The combined barrier and quenching effects of the char layer imparted VPE with excellent flame retardancy. This study illustrated a promising approach for synthesizing mechanically strong, thermally-stable and environmentally-friendly flame-retardant bio-based composite resins.