Polyacrylate coating has been used for modifying Polyethylene terephthalate (PET) film to improve its oxygen barrier performance. However, comprehensive study on the oxygen barrier of polyacrylate coating is still underway. In this work, a series of polyacrylate coatings with different functional monomers such as maleic acid (MA), acrylic acid (AA), 2-hydroxyethyl acrylate (2-HEA), and 2-butene-1, 4-diol (1, 4-BED) were prepared by using Desmodur L75 (L75) and Erisys Ga240 (Ga240) as a curing agent. The polyacrylate coatings were characterized by Fourier Transform Infrared (FT-IR) spectrometer. The oxygen permeability (Po 2 ) of the coatings was measured by Gas Permeability Tester. The results reveal that anhydride moiety produced by dehydration of carboxylic acid is the key structure for enhancing the oxygen barrier property of the polyacrylate coating. Moreover, when the anhydride coexists with other cross-linking structures, the oxygen barrier performance of the resulting coatings was not further enhanced. Compared with the pristine PET substrate, the anhydride-containing polyacrylate-coated PET film has reduced Po 2 by 68%. This work provides a facile strategy for improving the oxygen barrier performance of PET film by coating amorphous polyacrylate.
Fan Liu,Shuhong Xu,Pengfei Xia,Hongyu Yang,Ziting Qian,Yuan Jiang,Zhuyuan Wang,Dayan Ban,Chunlei Wang
In this work, fluorescent solid carbon dots (CDs) welcome a new member, namely anhydride-terminated CDs, which have a photoluminescence quantum yield (PLQY) of 28% for orange-emitted CDs at 580 nm in powder form. For the first time, we revealed that the electronic coupling of the functional groups should be a crucial factor affecting the optical properties of solid CDs. Due to the negligible hydrogen bonding interaction between the anhydride groups, the electronic coupling of excitons between neighboring anhydride groups is weak, leading to a high PLQY of 28% and an immobile emission peak at 580 nm in solid state. Anhydride-terminated CDs can be partly converted into carboxyl-terminated CDs after dispersion in ethanol. However, the strong electronic coupling of carboxyl groups at high concentration generates the stacking mode of J-aggregates, giving rise to a red-shifted emission from 450 to 515 nm as well as quenched fluorescence in solid state. In comparison, a useful blue emission for solid-state CDs occurs from low sp2 hybridized carbon atoms, which possess weak electronic coupling and a stationary emission band at 450 nm in both solution and solid state. By adjusting the feed ratio of the reactants, the relevant intensities between the emission from low sp2 hybridized carbon atoms at 450 nm and the emission from anhydride groups at 580 nm can be controlled. As a result, single-component anhydride-terminated CD powder with tunable emission color from orange to white light can be achieved. As-prepared anhydride-terminated CDs can be used for fabricating light-emitting diodes (LEDs), white LEDs, and luminescent solar concentrators (LSCs).
The current work demonstrates excellent thermal, mechanical, shape memory, and self-healing properties of 3D printable, thermoreversible, cross-linked network composites. The thermoreversible cross-linked networks are composed of Diels-Alder (DA) reversible covalent and transient cross-links, which are formed by thermoplastic polyurethane (TPU) and poly(ε-caprolactone) (PCL). Also, cellulose nanocrystalline (CNC) is utilized as a cross-linking agent. The incorporated CNC, modified with furan (CNC-FA) and maleic anhydride groups (CNC-MAH), exhibits excellent compatibility with TPU/PCL matrix, forming physical and chemical cross-linking structures in the composites. Also, the mechanical properties , thermal stability, and self-healing properties are significantly improved after the addition of modified CNC. In addition, the mechanism of performance enhancement is further analyzed by molecular dynamics simulations. One should note that the mechanically robust and 3D printable self-healing composites enable the fabrication of durable conductive devices and biomimetic skin devices with high mechanical integrity, excellent electrical healing and superior strain-induced fluorescence properties, showing promise in next-generation flexible electronics, encryption devices and electronic skins, and may broaden the variety and applications of 3D-printable materials.
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