Chemical and Biomolecular Engineering - Research Publications
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ItemAntifogging Surface Facilitated by Nanoscale Coatings with Controllable Hydrophobicity and Cross-Linking Density(WILEY-V C H VERLAG GMBH, 2017-01)
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ItemFullerene peapod nanoparticles as an organic semiconductor-electrode interface layer(ROYAL SOC CHEMISTRY, 2016)A syndiotactic poly(methyl methacrylate) bottlebrush polymer has been shown to complex with C60 fullerene and assemble into nanoparticles that can be dispersed in polar organic solvents. This composite material was used as an electrode interlayer in organic solar cell (OSC) devices leading to enhanced device performance.
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ItemFabrication of Chiral Stationary Phases via Continuous Assembly of Polymers for Resolution of Enantiomers by Liquid Chromatography(WILEY-V C H VERLAG GMBH, 2014-11)Precise stereochemical determination of chiral molecules is highly important, especially in the pharmaceutical industry where one enantiomer may have a therapeutic effect while the other has detrimental effects. Herein, the continuous assembly of polymers (CAP) mediated via ring‐opening metathesis polymerization (ROMP) is used to fabricate immobilized‐type chiral stationary phases (CSPs) – as cross‐linked thin films on solid supports – for enantiomeric separation. Optically active polysaccharides (chitosan and amylose) with aromatic substituents were pre‐functionalized with pendent norbornene groups and subsequently employed as macrocross‐linkers in the CAPROMP process, building cross‐linked films from initiator‐functionalized mesoporous silica particles. The immobilized cross‐linked films on mesoporous silica particles can act as CSPs. Therefore, the chiral recognition abilities of the CSPs were explored by liquid chromatography (LC). It was found that CSPs with higher amount of polysaccharide cross‐linked films – made from multiple CAP reactions – have better chiral separation capabilities. This work demonstrates the versatility of the CAP approach to fabricate CSPs to tailor specific separation needs.
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ItemNo Preview AvailableContinuous assembly of polymers via solid phase reactions(ROYAL SOC CHEMISTRY, 2014-09)
The formation of cross-linked polymer films, with tunable thickness, proceeds directionally from the substrate surface by controlled polymerization in the solid state.
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ItemLow-Fouling, Biospecific Films Prepared by the Continuous Assembly of Polymers(AMER CHEMICAL SOC, 2013-08)We report that the continuous assembly of polymers (CAP) approach, mediated by ring-opening metathesis polymerization (ROMP), is a facile and versatile technology to prepare engineered nanocoatings for various biomedical applications. Low-fouling coatings on particles were obtained by the formation of multicompositional, layered films via simple and efficient tandem CAP(ROMP) processes that are analogous to chain extension reactions. In addition, the CAP(ROMP) approach allows for the efficient postfunctionalization of the CAP films with bioactive moieties via cross-metathesis reactions between the surface-immobilized catalysts and symmetrical alkene derivatives. The combined features of the CAP(ROMP) approach (i.e., versatile polymer selection and facile functionalization) allow for the fabrication and surface modification of various types of polymer films, including those with intrinsic protein-repellent properties and selective protein recognition capabilities. This study highlights the various types of advanced coatings and materials that the CAP approach can be used to generate, which may be useful for biomedical applications.
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ItemAssembly of Free-Standing Polypeptide Films via the Synergistic Combination of Hyperbranched Macroinitiators, the Grafting-From Approach, and Cross-Chain Termination(WILEY-V C H VERLAG GMBH, 2013-09-06)Cross-linked polypeptide-based films are fabricated via a novel and robust method employing surface-initiated ring opening polymerization of α-amino acid N-carboxyanhydrides (NCA-ROP). The judicious combination of amine-based hyperbranched macroinitiators and benzyl ester-protected NCA derivatives promotes network formation by cross-chain terminations, which allows the formation of stable cross-linked peptide-based capsules in a one-pot system.
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ItemNo Preview AvailableTuning the Properties of Polymer Capsules for Cellular Interactions(AMER CHEMICAL SOC, 2017-07)Particle-cell interactions are governed by, among other factors, the composition and surface properties of the particles. Herein, we report the preparation of various polymer capsules with different compositions and properties via atom transfer radical polymerization mediated continuous assembly of polymers (CAPATRP), where the cellular interactions of these capsules, particularly fouling and specific targeting, are examined by flow cytometry and deconvolution microscopy. Acrylated eight-arm poly(ethylene glycol) (8-PEG) and poly(N-(2-hydroxypropyl)-methacrylamide) (PHPMA) as well as methacrylated hyaluronic acid (HA), poly(glutamic acid) (PGA), and poly(methacrylic acid) (PMA) are used as macro-cross-linkers to obtain a range of polymer capsules with different compositions (PEG, PHPMA, HA, PGA, and PMA). Capsules composed of low-fouling polymers, PEG and PHPMA, show negligible association with macrophage Raw 264.7, monocyte THP-1, and HeLa cells. HA capsules, although moderately low-fouling (<22%) to HeLa, BT474, Raw 264.7, and THP-1 cells, exhibit high targeting specificity to CD44-over-expressing MDA-MB-231 cells. In contrast, PGA and PMA capsules show high cellular association toward phagocytic Raw 264.7 and THP-1 cells. These findings demonstrate the capability of the CAPATRP technique in preparing polymer capsules with specific cellular interactions.
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ItemPhotocontrolled Cargo Release from Dual Cross-Linked Polymer Particles(AMER CHEMICAL SOC, 2016-03-09)Burst release of a payload from polymeric particles upon photoirradiation was engineered by altering the cross-linking density. This was achieved via a dual cross-linking concept whereby noncovalent cross-linking was provided by cyclodextrin host-guest interactions, and irreversible covalent cross-linking was mediated by continuous assembly of polymers (CAP). The dual cross-linked particles (DCPs) were efficiently infiltrated (∼80-93%) by the biomacromolecule dextran (molecular weight up to 500 kDa) to provide high loadings (70-75%). Upon short exposure (5 s) to UV light, the noncovalent cross-links were disrupted resulting in increased permeability and burst release of the cargo (50 mol % within 1 s) as visualized by time-lapse fluorescence microscopy. As sunlight contains UV light at low intensities, the particles can potentially be incorporated into systems used in agriculture, environmental control, and food packaging, whereby sunlight could control the release of nutrients and antimicrobial agents.
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ItemFabrication of ultra-thin polyrotaxane-based films via solid-state continuous assembly of polymers(ROYAL SOC CHEMISTRY, 2015)Surface-confined ultra-thin polyrotaxane (PRX)-based films with tunable composition, surface topology and swelling characteristics were prepared by solid-state continuous assembly of polymers (ssCAP). The PRX-based films supported cell attachment, and their degradation in biological media could be tuned. This study provides a versatile nano-coating technology with potential applications in biomedicine, including tissue engineering and medical devices.
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Item(Super)hydrophobic and Multilayered Amphiphilic Films Prepared by Continuous Assembly of Polymers(WILEY-V C H VERLAG GMBH, 2013-11-06)Abstract The continuous assembly of polymers (CAP) is used to fabricate tailored nanocoatings on a wide variety of substrates. Ring‐opening metathesis polymerization (ROMP) is used to mediate the CAP process (CAPROMP) to assemble specifically designed macromolecules into nanoengineered crosslinked films. Different films composed of single or multiple macromolecules are used to tune the surface wetting characteristics on various planar substrates, including porous substrates such as filter paper and cotton, and non‐porous subtrates such as aluminium foil and glass. By judicious selection of the macromolecules, these substrates, which are hydrophilic in nature, can be rendered (super)hydrophobic. The robustness of the ROMP catalysts and the reinitiation ability of the CAPROMP approach allow the production of layered multicomponent amphiphilic films with on‐demand switchable wettability. Such functional nanocoatings can be potentially applied as self‐cleaning surfaces, as waterproof woven fabrics, and for the next generation of microelectronic devices.