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152 results on '"Luo, Yingdong"'

4. Tuning of protease resistance in oligopeptides through N -alkylation

Author

Kaminker, Revital, Anastasaki, Athina, Gutekunst, Will R, Luo, Yingdong, Lee, Sang-Ho, and Hawker, Craig J

Subjects
Chemical Sciences, Organic Chemistry
Abstract

N-Methylation of amino acids is an effective way to create protease resistance in both natural and synthetic peptides. However, alkyl substituents other than N-methyl have not been extensively studied. Here, we prepare and examine a series of N-substituted peptides in which the size and length of the alkyl group is modulated. These design insights provide a unique and modular handle for tuning proteolysis in oligopeptides.

Published
2018

6. Metal-Free Removal of Polymer Chain Ends Using Light

Author

Mattson, Kaila M, Pester, Christian W, Gutekunst, Will R, Hsueh, Andy T, Discekici, Emre H, Luo, Yingdong, Schmidt, Bernhard VKJ, McGrath, Alaina J, Clark, Paul G, and Hawker, Craig J

Subjects
Chemical Sciences, Engineering, Polymers
Abstract

A light-mediated method for the facile removal of polymer end groups that are common to controlled radical polymerization techniques is presented. This metal-free strategy is general, being effective for chlorine, bromine, and thiocarbonylthio moieties as well as a number of different polymer families (styrenic, acrylic, and methacrylic). In addition to solution reactions, this process is readily translated to thin films, where light mediation allows the straightforward fabrication of hierarchically patterned polymer brushes.

Published
2016

7. Chemoselective Radical Dehalogenation and C–C Bond Formation on Aryl Halide Substrates Using Organic Photoredox Catalysts

Author

Poelma, Saemi O, Burnett, G Leslie, Discekici, Emre H, Mattson, Kaila M, Treat, Nicolas J, Luo, Yingdong, Hudson, Zachary M, Shankel, Shelby L, Clark, Paul G, Kramer, John W, Hawker, Craig J, and de Alaniz, Javier Read

Subjects
Carbon, Catalysis, Free Radicals, Halogenation, Hydrocarbons, Halogenated, Photochemical Processes, Medicinal and Biomolecular Chemistry, Organic Chemistry
Abstract

Despite the number of methods available for dehalogenation and carbon-carbon bond formation using aryl halides, strategies that provide chemoselectivity for systems bearing multiple carbon-halogen bonds are still needed. Herein, we report the ability to tune the reduction potential of metal-free phenothiazine-based photoredox catalysts and demonstrate the application of these catalysts for chemoselective carbon-halogen bond activation to achieve C-C cross-coupling reactions as well as reductive dehalogenations. This procedure works both for conjugated polyhalides as well as unconjugated substrates. We further illustrate the usefulness of this protocol by intramolecular cyclization of a pyrrole substrate, an advanced building block for a family of natural products known to exhibit biological activity.

Published
2016

8. Simple Benchtop Approach to Polymer Brush Nanostructures Using Visible-Light-Mediated Metal-Free Atom Transfer Radical Polymerization

Author

Discekici, Emre H, Pester, Christian W, Treat, Nicolas J, Lawrence, Jimmy, Mattson, Kaila M, Narupai, Benjaporn, Toumayan, Edward P, Luo, Yingdong, McGrath, Alaina J, Clark, Paul G, de Alaniz, Javier Read, and Hawker, Craig J

Subjects
Inorganic Chemistry, Chemical Sciences, Macromolecular and Materials Chemistry, Physical Chemistry (incl. Structural), Macromolecular and materials chemistry, Physical chemistry
Abstract

The development of an operationally simple, metal-free surface-initiated atom transfer radical polymerization (SI-ATRP) based on visible-light mediation is reported. The facile nature of this process enables the fabrication of well-defined polymer brushes from flat and curved surfaces using a "benchtop" setup that can be easily scaled to four-inch wafers. This circumvents the requirement of stringent air-free environments (i.e., glovebox), and mediation by visible light allows for spatial control on the micron scale, with complex three-dimensional patterns achieved in a single step. This robust approach leads to unprecedented access to brush architectures for nonexperts.

Published
2016

10. A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations

Author

Discekici, Emre H, Treat, Nicolas J, Poelma, Saemi O, Mattson, Kaila M, Hudson, Zachary M, Luo, Yingdong, Hawker, Craig J, and de Alaniz, Javier Read

Subjects
Chemical Sciences, Organic Chemistry
Abstract

Here we report the use of 10-phenylphenothiazine (PTH) as an inexpensive, highly reducing metal-free photocatalyst for the reduction of carbon-halogen bonds via the trapping of carbon-centered radical intermediates with a mild hydrogen atom donor. Dehalogenations were carried out on various substrates with excellent yields at room temperature in the presence of air.

Published
2015

15. Optofluidic phase-shifting digital holographic microscopy for quantitative measurement of microfluidic diffusion dynamics.

Author

Luo, Yingdong, Yang, Jinwu, Tu, Xin, Huang, Tianye, Che, Zhizhao, and Song, Chaolong

Subjects
*DIGITAL holographic microscopy, *DIFFUSION measurements, *PHASE-shifting interferometry, *FLUID dynamic measurements, *STEREOLOGY, *MICROFLUIDIC analytical techniques
Abstract

In this work, an integrated optofluidic phase-shifting element, along with an image processing algorithm, was proposed to enable quantitative analysis for microfluidic applications using a digital holographic microscopic configuration. The advantages of the proposed system lie in its compactness, that the phase-shifting element can be simultaneously fabricated with other microfluidic functional components on a single chip, its robustness to resist environmental vibrations as no mechanical movement is involved for phase-shifting, and its capability of capturing transient events of fluid dynamics for quantitative measurement. The performance of the proposed system was validated with quantitatively label-free monitoring of concentration gradients under various conditions in microchannels. [ABSTRACT FROM AUTHOR]

Published
2020
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21. Engineering Edge States of Graphene Nanoribbons for Narrow-Band Photoluminescence

Author

Ma, Chuanxu, primary, Xiao, Zhongcan, additional, Puretzky, Alexander A., additional, Wang, Hao, additional, Mohsin, Ali, additional, Huang, Jingsong, additional, Liang, Liangbo, additional, Luo, Yingdong, additional, Lawrie, Benjamin J., additional, Gu, Gong, additional, Lu, Wenchang, additional, Hong, Kunlun, additional, Bernholc, Jerzy, additional, and Li, An-Ping, additional

Published
2020
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23. Insight into the Mechanisms Driving the Self-Assembly of Functional Interfaces: Moving from Lipids to Charged Amphiphilic Oligomers

Author

Chowdhury, Azhad U., primary, Taylor, Graham J., additional, Bocharova, Vera, additional, Sacci, Robert L., additional, Luo, Yingdong, additional, McClintic, William T., additional, Ma, Ying-Zhong, additional, Sarles, Stephen A., additional, Hong, Kunlun, additional, Collier, C. Patrick, additional, and Doughty, Benjamin, additional

Published
2019
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27. Improved self-assembly of poly (dimethylsiloxane-b-ethylene oxide) using a hydrogen-bonding additive

Author

Luo, Yingdong, Kim, Bongkeun, Montarnal, Damien, Mester, Zoltan, Pester, Christian W, McGrath, Alaina J, Hill, Glake, Kramer, Edward J, Fredrickson, Glenn H, Hawker, Craig J, Laboratoire de Chimie, Catalyse, Polymères et Procédés, R 5265 (C2P2), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École supérieure de Chimie Physique Electronique de Lyon (CPE)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Materials Research Laboratory (MRL), University of California [Santa Barbara] (UCSB), and University of California-University of California

Subjects
[CHIM.POLY]Chemical Sciences/Polymers, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; no abstract

Published
2016

30. Effects of Tailored Dispersity on the Self-Assembly of Dimethylsiloxane–Methyl Methacrylate Block Co-Oligomers

Author

Oschmann, Bernd, primary, Lawrence, Jimmy, additional, Schulze, Morgan W., additional, Ren, Jing M., additional, Anastasaki, Athina, additional, Luo, Yingdong, additional, Nothling, Mitchell D., additional, Pester, Christian W., additional, Delaney, Kris T., additional, Connal, Luke A., additional, McGrath, Alaina J., additional, Clark, Paul G., additional, Bates, Christopher M., additional, and Hawker, Craig J., additional

Published
2017
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32. Poly (dimethylsiloxane-b-methyl methacrylate): A Promising Candidate for Sub-10 nm Patterning

Author

Luo, Yingdong, Montarnal, Damien, Kim, Sangwon, Shi, Weichao, Barteau, Katherine P, Pester, Christian W, Hustad, Phillip D, Christianson, Matthew D, Fredrickson, Glenn H, Kramer, Edward J, Hawker, Craig J, Materials Research Laboratory (MRL), University of California [Santa Barbara] (UCSB), University of California-University of California, Materials Research Laboratory, and The Dow Chemical Company

Subjects
[CHIM.POLY]Chemical Sciences/Polymers, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; no abstract

Published
2015

33. Insight into the Mechanisms Driving the Self-Assembly of Functional Interfaces: Moving from Lipids to Charged Amphiphilic Oligomers

Author

Chowdhury, Azhad U., Taylor, Graham J., Bocharova, Vera, Sacci, Robert L., Luo, Yingdong, McClintic, William T., Ma, Ying-Zhong, Sarles, Stephen A., Hong, Kunlun, Collier, C. Patrick, and Doughty, Benjamin

Abstract

Polymer-stabilized liquid/liquid interfaces are an important and growing class of bioinspired materials that combine the structural and functional capabilities of advanced synthetic materials with naturally evolved biophysical systems. These platforms have the potential to serve as selective membranes for chemical separations and molecular sequencers and to even mimic neuromorphic computing elements. Despite the diversity in function, basic insight into the assembly of well-defined amphiphilic polymers to form functional structures remains elusive, which hinders the continued development of these technologies. In this work, we provide new mechanistic insight into the assembly of an amphiphilic polymer-stabilized oil/aqueous interface, in which the headgroups consist of positively charged methylimidazolium ionic liquids, and the tails are short, monodisperse oligodimethylsiloxanes covalently attached to the headgroups. We demonstrate using vibrational sum frequency generation spectroscopy and pendant drop tensiometery that the composition of the bulk aqueous phase, particularly the ionic strength, dictates the kinetics and structures of the amphiphiles in the organic phase as they decorate the interface. These results show that H-bonding and electrostatic interactions taking place in the aqueous phase bias the grafted oligomer conformations that are adopted in the neighboring oil phase. The kinetics of self-assembly were ionic strength dependent and found to be surprisingly slow, being composed of distinct regimes where molecules adsorb and reorient on relatively fast time scales, but where conformational sampling and frustrated packing takes place over longer time scales. These results set the stage for understanding related chemical phenomena of bioinspired materials in diverse technological and fundamental scientific fields and provide a solid physical foundation on which to design new functional interfaces.

Published
2020
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43. Ambiguous anti-fouling surfaces: Facile synthesis by light-mediated radical polymerization.

Author

Pester, Christian W., Poelma, Justin E., Narupai, Benjaporn, Patel, Shrayesh N., Su, Gregory M., Mates, Thomas E., Luo, Yingdong, Ober, Christopher K., Hawker, Craig J., and Kramer, Edward J.

Subjects
PHOTOPOLYMERIZATION, RADICALS (Chemistry), FOULING, POLYETHYLENE glycol, COPPER catalysts
Abstract

ABSTRACT In an attempt to create a polymer brush-based platform for the systematic study for anti-biofouling surfaces, the benefits of surface initiated, visible light-mediated radical polymerization are utilized to fabricate well-defined, chemically ambiguously patterned surfaces. A variety of analytical tools are used to illustrate the precise tuning of surface chemistry and thoroughly characterize spatially well-defined, hydrophilic/hydrophobic surfaces composed of poly(ethylene glycol methacrylate) and poly(trifluoroethyl methacrylate) with chemical definition on the micron scale. Advantages of both visible light-mediated photopolymerization and traditional copper-catalyzed atom transfer radical polymerization are combined to achieve both high spatial control and expanded monomer tolerance. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 253-262 [ABSTRACT FROM AUTHOR]

Published
2016
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