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Keywords = core–shell polymer strand

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13 pages, 2347 KB  
Article
Ultra-Mild Fabrication of Highly Concentrated SWCNT Dispersion Using Spontaneous Charging in Solvated Electron System
by Junho Shin, Jung Hoon Kim, Jungeun Lee, Sangyong Lee, Jong Hwan Park, Seung Yol Jeong, Hee Jin Jeong, Joong Tark Han, Seon Hee Seo, Seoung-Ki Lee and Jungmo Kim
Nanomaterials 2024, 14(13), 1094; https://doi.org/10.3390/nano14131094 - 26 Jun 2024
Cited by 2 | Viewed by 2877
Abstract
The efficient dispersion of single-walled carbon nanotubes (SWCNTs) has been the subject of extensive research over the past decade. Despite these efforts, achieving individually dispersed SWCNTs at high concentrations remains challenging. In this study, we address the limitations associated with conventional methods, such [...] Read more.
The efficient dispersion of single-walled carbon nanotubes (SWCNTs) has been the subject of extensive research over the past decade. Despite these efforts, achieving individually dispersed SWCNTs at high concentrations remains challenging. In this study, we address the limitations associated with conventional methods, such as defect formation, excessive surfactant use, and the use of corrosive solvents. Our novel dispersion method utilizes the spontaneous charging of SWCNTs in a solvated electron system created by dissolving potassium in hexamethyl phosphoramide (HMPA). The resulting charged SWCNTs (c-SWCNTs) can be directly dispersed in the charging medium using only magnetic stirring, leading to defect-free c-SWCNT dispersions with high concentrations of up to 20 mg/mL. The successful dispersion of individual c-SWCNT strands is confirmed by their liquid-crystalline behavior. Importantly, the dispersion medium for c-SWCNTs exhibits no reactivity with metals, polymers, or other organic solvents. This versatility enables a wide range of applications, including electrically conductive free-standing films produced via conventional blade coating, wet-spun fibers, membrane electrodes, thermal composites, and core-shell hybrid microparticles. Full article
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13 pages, 3066 KB  
Article
Deposition Offset of Printed Foam Strands in Direct Bubble Writing
by Prasansha Rastogi, Cornelis H. Venner and Claas Willem Visser
Polymers 2022, 14(14), 2895; https://doi.org/10.3390/polym14142895 - 16 Jul 2022
Cited by 3 | Viewed by 2457
Abstract
Direct Bubble Writing is a recent technique to print shape-stable 3-dimensional foams from streams of liquid bubbles. These bubbles are ejected from a core-shell nozzle, deposited on the build platform placed at a distance of approximately 10 cm below the nozzle, and photo-polymerized [...] Read more.
Direct Bubble Writing is a recent technique to print shape-stable 3-dimensional foams from streams of liquid bubbles. These bubbles are ejected from a core-shell nozzle, deposited on the build platform placed at a distance of approximately 10 cm below the nozzle, and photo-polymerized in situ. The bubbles are ejected diagonally, with a vertical velocity component equal to the ejection velocity and a horizontal velocity component equal to the motion of the printhead. Owing to the horizontal velocity component, a discrepancy exists between the nozzle trajectory and the location of the printed strand. This discrepancy can be substantial, as for high printhead velocities (500 mm/s) an offset of 8 mm (in radius) was measured. Here, we model and measure the deviation in bubble deposition location as a function of printhead velocity. The model is experimentally validated by the printing of foam patterns including a straight line, a circle, and sharp corners. The deposition offset is compensated by tuning the print path, enabling the printing of a circular path to the design specifications and printing of sharp corners with improved accuracy. These results are an essential step towards the Direct Bubble Writing of 3-dimensional polymer foam parts with high dimensional accuracy. Full article
(This article belongs to the Special Issue Advanced Cellular Polymers)
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12 pages, 3948 KB  
Article
Numerical Simulation of a Core–Shell Polymer Strand in Material Extrusion Additive Manufacturing
by Hamid Narei, Maryam Fatehifar, Ashley Howard Malt, John Bissell, Mohammad Souri, Mohammad Nasr Esfahani and Masoud Jabbari
Polymers 2021, 13(3), 476; https://doi.org/10.3390/polym13030476 - 2 Feb 2021
Cited by 19 | Viewed by 4700
Abstract
Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the [...] Read more.
Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the 3D-printed manufactured products. Here we use numerical simulations within the framework of computation fluid dynamics (CFD) to identify the best combination of operating parameters for the 3D printing of a core–shell polymer strand. The objectives of these CFD simulations are to find strands with an ultimate volume fraction of core polymer. At the same time, complete encapsulations are obtained for the core polymer inside the shell one. In this model, the deposition flow is controlled by three dimensionless parameters: (i) the diameter ratio of core material to the nozzle, d/D; (ii) the normalised gap between the extruder and the build plate, t/D; (iii) the velocity ratio of the moving build plate to the average velocity inside the nozzle, V/U. Numerical results of the deposited strands’ cross-sections demonstrate the effects of controlling parameters on the encapsulation of the core material inside the shell and the shape and size of the strand. Overall we find that the best operating parameters are a diameter ratio of d/D=0.7, a normalised gap of t/D=1, and a velocity ratio of V/U=1. Full article
(This article belongs to the Special Issue Modelling and Simulation of Polymers)
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6 pages, 558 KB  
Proceeding Paper
mRNA Structuring for Stabilizing mRNA Nanocarriers and Improving Their Delivery Efficiency
by Satoshi Uchida, Kyoko Koji, Naoto Yoshinaga, Yuki Mochida, Taehun Hong and Horacio Cabral
Mater. Proc. 2021, 4(1), 82; https://doi.org/10.3390/IOCN2020-07789 - 10 Nov 2020
Cited by 1 | Viewed by 1819
Abstract
For in vivo application of mRNA therapeutics, the development of mRNA nanocarriers that protect mRNA from enzymatic degradation is needed. While current nanocarrier development focuses on fine-tuning the chemical structure of its components, including lipids and polymers, herein, we propose a novel strategy [...] Read more.
For in vivo application of mRNA therapeutics, the development of mRNA nanocarriers that protect mRNA from enzymatic degradation is needed. While current nanocarrier development focuses on fine-tuning the chemical structure of its components, including lipids and polymers, herein, we propose a novel strategy to design stable mRNA nanocarriers by structuring mRNA inside the nanocarriers. Firstly, several mRNA strands were crosslinked with each other using RNA crosslinkers that hybridize to mRNA strands, to prepare mRNA nanoassemblies (NAs). Then, we mixed NAs with poly(ethylene glycol) (PEG)-polycation block copolymers to prepare core–shell-structured polyplex micelles (PMs), composed of PEG shell and mRNA-containing core. Notably, PM-loading NAs (NA/m) exhibited enhanced stability against enzymatic attack and polyion exchange reaction compared to that loading naïve mRNA (naïve/m). According to mechanistic analyses, NA/m possessed a shell with a denser PEG layer and a core with more condensed mRNA compared to naïve/m. As a result, NA/m induced more efficient protein expression after introduction to cultured cells and mouse brain, compared to naïve/m. While newly developed materials need long processes before their clinical approval, our strategy is effective in improving stability and the mRNA introduction efficiency of existing mRNA nanocarriers just by structuring mRNA without the use of additional materials. Full article
(This article belongs to the Proceedings of The 2nd International Online-Conference on Nanomaterials)
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