Chemical and Biomolecular Engineering - Research Publications
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ItemReduced Ice Adhesion Using Amphiphilic Poly(Ionic Liquid)-Based Surfaces(American Chemical Society, 2023-01-28)Ice build-up on solid surfaces causes significant economic losses for a range of industries. One solution to this problem is the development of coatings with low ice adhesion strength. Amphiphilic poly(ionic liquid) (PIL)-based surfaces have been recently reported for antifogging/antifrosting applications. However, they have possible anti-icing properties through lowering the ice adhesion strength that have yet to be reported. Herein, we designed well-defined triblock copolymers composed of a polydimethylsiloxane component coupled with PIL segments of poly([2 (methacryloyloxy)ethyl] trimethylammonium chloride) (PMETAC), which were subsequently UV-cured with an oligo(ethylene glycol) dimethacrylate (OEGDMA) cross-linker. The structure-property relationships of the resultant semi-interpenetrating polymer networks (SIPNs) were investigated by varying the counterion (i.e., trimethylammonium bis(trifluoromethanesulfonyl)imide (TFSI-)) and the content of the PIL segments and cross-linker. An ice adhesion strength as low as 13.3 ± 8.6 kPa was observed for the coating containing 12.5 wt % of PMETAC segment and 5 wt % of OEGDMA, which is one of the lowest values reported so far for the amphiphilic coatings. Characterization of the coatings in terms of surface features, wettability, and hydration states have enabled the elucidation of different deicing mechanisms. Self-lubrication due to the existence of nonfreezable bound water led to the obtained low ice adhesion strength. This work offers a new approach for the exploration of PIL-based icephobic coatings for practical applications.
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ItemMechanochromophore-Linked Polymeric Materials with Visible Color Changes(WILEY-V C H VERLAG GMBH, 2022-05)Mechanical force as a type of stimuli for smart materials has obtained much attention in the past decade. Color-changing materials in response to mechanical stimuli have shown great potential in the applications such as sensors and displays. Mechanochromophore-linked polymeric materials, which are a growing sub-class of these materials, are discussed in detail in this review. Two main types of mechanochromophores which exhibit visible color change, summarized herein, involve either isomerization or radical generation mechanisms. This review focuses on their synthesis and incorporation into polymer matrices, the type of mechanical force used, factors affecting the mechanochromic properties, and their applications.
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ItemCrosslinked Polypeptide Films via RAFT-Mediated Continuous Assembly of Polymers(WILEY-V C H VERLAG GMBH, 2022-02-21)Polypeptide coatings are a cornerstone in the field of surface modification due to their widespread biological potential. As their properties are dictated by their structural features, subsequent control thereof using unique fabrication strategies is important. Herein, we report a facile method of precisely creating densely crosslinked polypeptide films with unusually high random coil content through continuous assembly polymerization via reversible addition-fragmentation chain transfer (CAP-RAFT). CAP-RAFT was fundamentally investigated using methacrylated poly-l-lysine (PLLMA) and methacrylated poly-l-glutamic acid (PLGMA). Careful technique refinement resulted in films up to 36.1±1.1 nm thick which could be increased to 94.9±8.2 nm after using this strategy multiple times. PLLMA and PLGMA films were found to have 30-50 % random coil conformations. Degradation by enzymes present during wound healing reveals potential for applications in drug delivery and tissue engineering.
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ItemVernetzte Polypeptide durch RAFT‐vermittelte Polymerisation zum kontinuierlichen Aufbau von Polymerfilmen(Wiley, 2022-02-21)Abstract Polypeptidbeschichtungen spielen aufgrund ihres großen biologischen Potentials eine wichtige Rolle in der Oberflächenmodifizierung von Materialien. Da ihre Eigenschaften durch ihren strukturellen Aufbau mitbestimmt werden, ist eine Kontrolle der Struktur durch entsprechende Herstellungsstrategien notwendig. In diesem Artikel berichten wir über eine einfache Methode zur präzisen Herstellung von dicht vernetzten Polypeptidfilmen mit ungewöhnlich hoher β‐Faltblatt – und Zufallsknäuel Konformation durch eine kontinuierliche Assemblierungspolymerisation (CAP, continuous assembly polymerization) mittels reversibler Addtitions‐Fragmentierungs‐Kettenübertragungspolymerisation (RAFT Polymerisation, reversible‐addition‐fragmentation chain‐transfer polymerization), kurz CAP‐RAFT. CAP‐RAFT wurde bereits grundlegend mit methacryliertem Poly‐l‐Lysin (PLLMA) und methacrylierter Poly‐l‐Glutaminsäure (PLGMA) untersucht. Eine sorgfältige Anpassung der Methode führte hier zu Filmen mit einer Schichtdicke von bis zu 36.1±1.1 nm, die durch mehrfache Anwendung dieser Strategie auf 94.9±8.2 nm erhöht werden konnte. PLLMA‐ und PLGMA‐Filme wiesen überraschenderweise bis zu 30–50 % Zufallsknäuel Konformation auf. Durch den enzymatischen Abbau mit einem Protease‐Mix, der Proteasen im Wundheilungsmileu repräsentiert, konnte das Potential diesen Strukturen für Anwendungen im Wirkstofftransport und in der Gewebezüchtung gezeigt werden.
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ItemRegulating Color Activation Energy of Mechanophore-Linked Multinetwork Elastomers(American Chemical Society, 2020-05-26)To lower color activation stress/strain while maintaining excellent mechanical properties for mechanochromic materials has been a challenge. Here, a structure of multinetwork polyacrylates was adopted to incorporate a widely studied mechanophore, spiropyran (SP), to investigate the regulation of mechanochromic sensitivity by varying network compositions. In situ color channel intensity analysis was used to characterize deformation-induced ring-opening of SP to merocyanine (MC) for color changes. The multinetwork strategy could substantially reduce the onset of mechanochromic activation strain and stress, and the resulted double networks and triple networks exhibited remarkable mechanochromic performance with excellent mechanical properties. The network formation conditions, including solvent ratio and type of monomers, were shown to have great impact on regulating the mechanochromic activities. A triple-network sample achieved the lowest macroscopic color activation energy compared to previously reported SP-linked elastomers. In addition, the ratio of SP to MC conversion activated by stretching was first shown higher than that by UV light.
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ItemReversible Nontoxic Thermochromic Microcapsules.(American Chemical Society, 2020-02-26)Thermochromic materials exhibit a color change in response to a change in temperature. Creating nontoxic microcapsules containing thermochromic materials for applications in ink and film materials is historically challenging. In this study, we develop a nontoxic chlorophenol red (CPR)-water thermochromic system and its microcapsules with silicone shells via a reaction between water and octadecyltrichlorosilane (OTS) at the interface of a w/o emulsion. The obtained microcapsules exhibit a clear color change with full reversibility and are successfully used as inks by screen printing and as additives in films. Nontoxicity of both microcapsules and films is demonstrated through cell cytotoxicity assays. These features make these novel materials applicable to the next generation of intelligent sensors, coating, and food packaging materials.