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177 results on '"Pester, Christian W."'

2. Rapid Self‐Healing of Robust Surface‐Tethered Covalent Adaptable Coatings.

Author

Capets, Jacob A., Yost, Sierra F., Vogt, Bryan D., and Pester, Christian W.

Subjects
POLYMER networks, SERVICE life, HIGH temperatures, URETHANE, COVALENT bonds
Abstract

The incorporation of self‐healing properties to repair scratches (or other minor damage) has revolutionized the coating industry by increasing service life, sustainability, and optical appearance. This work addresses challenges with the robustness of self‐healing coatings through the inclusion of surface‐tethered covalently adaptable networks (CANs). Surface‐initiated polymerization is combined with spray‐coating to deposit polymers to produce coatings with reversible crosslinks to the tethered chains. These robust coatings are based on reversible vinylogous urethane bonds using 2‐(acetoacetoxy)ethyl methacrylate‐based polymers and tris(2‐aminoethyl) amine (TREN). Here, TREN enables reversible covalent bonding between the spray‐coated and surface‐tethered polymers. Without this polymer brush layer, the physisorbed CAN coatings fail to self‐heal completely, are labile to solvent, and exhibit shear delamination upon scratching. The utility of this tethered coating approach is highlighted through its ability to autonomously self‐heal incisions within seconds at elevated temperatures, or more steadily under ambient conditions. The key to these advancements is the use of polymer brushes as a primer layer to attach the CAN to enhance healing and improve the environmental robustness of the coating. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Novel Strategy for Photopatterning Emissive Polymer Brushes for Organic Light Emitting Diode Applications

Author

Page, Zachariah A, Narupai, Benjaporn, Pester, Christian W, Zerdan, Raghida Bou, Sokolov, Anatoliy, Laitar, David S, Mukhopadhyay, Sukrit, Sprague, Scott, McGrath, Alaina J, Kramer, John W, Trefonas, Peter, and Hawker, Craig J

Subjects
Chemical Sciences
Abstract

A light-mediated methodology to grow patterned, emissive polymer brushes with micron feature resolution is reported and applied to organic light emitting diode (OLED) displays. Light is used for both initiator functionalization of indium tin oxide and subsequent atom transfer radical polymerization of methacrylate-based fluorescent and phosphorescent iridium monomers. The iridium centers play key roles in photocatalyzing and mediating polymer growth while also emitting light in the final OLED structure. The scope of the presented procedure enables the synthesis of a library of polymers with emissive colors spanning the visible spectrum where the dopant incorporation, position of brush growth, and brush thickness are readily controlled. The chain-ends of the polymer brushes remain intact, affording subsequent chain extension and formation of well-defined diblock architectures. This high level of structure and function control allows for the facile preparation of random ternary copolymers and red-green-blue arrays to yield white emission.

Published
2017

6. Molecular mass engineering for filaments in material extrusion additive manufacture.

Author

Yost, Sierra F., Pester, Christian W., and Vogt, Bryan D.

Subjects
MOLECULAR weights, THREE-dimensional printing, THERMOPLASTICS, POLYMETHYLMETHACRYLATE, RHEOLOGY
Abstract

3D printing of thermoplastics through local melting and deposition via material extrusion additive manufacturing provides a simple route to the near net‐shape manufacture of complex objects. However, the mechanical properties resulting from these 3D printed structures tend to be inferior when compared to traditionally manufactured thermoplastics. These unfavorable characteristics are generally attributed to the structure of the interface between printed roads. Here, we illustrate how the molecular mass distribution for a model thermoplastic, poly(methyl methacrylate) (PMMA), can be tuned to enhance the Young's modulus of 3D printed plastics. Engineering the molecular mass distribution alters the entanglement density, which controls the strength of the PMMA in the solid state and the chain diffusion in the melt. Increasing the low molecular mass tail increases Young's modulus and ultimate tensile strength of the printed parts. These changes in mechanical properties are comparable to more complex routes previously reported involving new chemistry or nanoparticles to enhance the mechanical performance of 3D printed thermoplastics. Controlling the molecular mass distribution provides a simple route to improve the performance in 3D printing of thermoplastics that can be as effective as more complex approaches. [ABSTRACT FROM AUTHOR]

Published
2024
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10. 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

11. 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

27. Estimating Internal Stress of an Alteration Layer Formed on Corroded Boroaluminosilicate Glass through Spectroscopic Ellipsometry Analysis

Author

Kaya, Huseyin, primary, Ngo, Dien, additional, Hahn, Seung Ho, additional, Li, Mingxiao, additional, He, Hongtu, additional, Yedikardeş, Beyza, additional, Sökmen, İlkay, additional, Pester, Christian W., additional, Podraza, Nikolas J., additional, Gin, Stephane, additional, and Kim, Seong H., additional

Published
2021
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39. 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

40. 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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42. Electric-Field-Induced Order-Order Transition from Hexagonally Perforated Lamellae to Lamellae

Author

Pester, Christian W., Schmidt, Kristin, Ruppel, Markus, Schoberth, Heiko G., Böker, Alexander, and Publica

Subjects
Institut für Chemie
Abstract

Block copolymers form a variety of microphase morphologies due to their ability to phase separate. The hexagonally perforated lamellar (HPL) morphology represents an unusually long-lived, nonequilibrium transient structure between lamellar and cylindrical phases. We present a detailed study of a concentrated, HPL-forming poly(styrene-b-isoprene) diblock copolymer solution in toluene in the presence of an electric field. We will show that this phase is readily aligned by a moderate electric field and provide experimental evidence for an electric-field-induced order order transition toward the lamellar phase under sufficiently strong fields. This process is shown to be fully reversible as lamellar perforations reconnect immediately upon secession of the external stimulus, recovering highly aligned perforated lamellae.

Published
2015

43. 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

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