Pester Research Group

Polymer Surface Science at Penn State

Research

Surface-initiated reversible deactivation radical polymerization

SI-PET-RAFT affords functionalization of surfaces with spatiotemporal control and provides oxygen tolerance under ambient conditions. All hallmarks of controlled radical polymerization (CRP) are met, affording well-defined polymerization kinetics, and chain end retention to allow subsequent extension of active chain ends to form block copolymers. The modularity and versatility of SI-PET-RAFT is highlighted through significant flexibility with respect to the choice of monomer, light source and wavelength, and photoredox catalyst. The ability to obtain complex patterns in the presence of air is a significant contribution to help pave the way for CRP-based surface functionalization into commercial application.

 Related Publications

  1. SI-PET-RAFT: Surface-Initiated Photoinduced Electron Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization — M. Li, M. Fromel, D. Ranaweera, S. Rocha, C. Boyer, C. W. Pester*. ACS Macro Lett. 2019, 8, 4, 374-380.
  2. Superhydrophilic Polymer Brushes with High Durability and Anti-Fogging Activity — M. Fromel, D. M. Sweeder, S. Jang, T. A. Williams, S. H. Kim, C. W. Pester*. ACS Appl. Polym. Mater. 2021, 3,  5291–5301
  3. Preparation of Patterned and Multilayer Thin Films for Organic Electronics via Oxygen-Tolerant SI-PET-RAFT — J. Poisson, A. M. Polgar, M. Fromel, C. W. Pester*, Z. M. Hudson. Angew. Chem. 2021, 60, 19988

Heterogeneous photoredox catalysis

Photoredox catalysis is a potent approach that provides user-friendly access to small and macromolecular molecules under mild reaction conditions, using visible light, and at ambient temperatures and pressures. However, the photocatalysts’ inherently strong visible light absorption means that catalyst residuals in the final polymer product can lead to discoloration and their excited states can promote material degradation. Further, the high cost of common transition metal photocatalysts and complex synthetic pathways for organic alternatives makes their use on large scales economically prohibitive. To address these limitations, we are working on heterogeneous photoredox catalysis platforms based on organic photocatalyst-functionalized polymers grafted to micron-scale glass beads.

 Related Publications

  1. Heterogeneous photoredox catalysis using fluorescein polymer brush functionalized glass beads — K. Bell, S. Freeburne, M. Fromel, H. Oh, C. W. Pester*. J. Polym. Sci. 2021, 59, 2844-2853

 

Solution exchange lithography

Humboldt Fellow at University of California at Santa Barbara (UCSB, USA)

Hosts: Prof. Edward J. Kramer & Prof. Craig. J. Hawker

Topographically- and chemically-patterned surface-tethered polymer brushes with spatially-confined functionalities are useful for a plethora of targeted, interdisciplinary applications. However, many current approaches to accessing these structured materials either are destructive or involve tedious, repetitive deposition of initiating molecules. During my postdoctoral tenure I have developed Solution Exchange Lithography (SEL) as a cost- and time-efficient, and extremely versatile platform for the fabrication of such multi-functional substrates with chemically complex, hierarchical architectures from uniform initiating monolayers. SEL combines the benefits of stop-flow and reduction lithography techniques, allowing a wide variety of photochemical reactions. We can readily exchange reactants in-situ, without the necessity of altering the position of a projected photomask. The spatial decoupling of the photomask from the substrate allows us to reduce arbitrarily complex inkjet-printed patterns down to the micron-scale.

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 Related Publications

  1. Engineering surfaces through sequential stop-flow photopatterning — C. W. Pester, B. Narupai, K. M. Mattson, D. P. Bothman, D. Klinger, K. W. Lee, E. H. Discekici, and C. J. Hawker. Adv. Mater. 2016, 28, 9292.
  2. Ambiguous anti-fouling surfaces: facile synthesis by light-mediated radical polymerization — C. W. Pester, J. E. Poelma, B. Narupai, S. N. Patel, G. M. Su, T. E. Mates, Y. Luo, C. K. Ober, C. J. Hawker, and E. J. Kramer. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 253.
  3. Metal-free removal of polymer chain ends using light — K. M. Mattson, C. W. Pester, W. R. Gutekunst, A. T. Hsueh, E. H. Discekici, Y. Luo, B. V. K. J. Schmidt, A. J. McGrath, P. G. Clark, and C. J. Hawker. 2016, 49, 8162.

 

Block copolymers in electric fields

Ph.D. Student at RWTH Aachen & DWI Leibniz Institute for Interactive Materials (Germany)

Advisor: Prof. Alexander Böker

Block copolymers readily self-assemble in bulk and solution to yield a wide variety of either well defined thermotropic or lyotropic phases with characteristic lengths on the mesoscopic scale. Such self-assembled structures provide a versatile tool for soft-matter nanotechnology, such as soft lithography, nanostructured networks, and membranes. To harvest the full potential of self-assembled block copolymer morphologies adaptable, strategies are required to control and manipulate their spatial orientation, periodicity, connectivity, and long-range order. Twenty years have passed since Amundson first studied block copolymer alignment using electric fields. In strong collaboration with the Oak Ridge national Laboratory (ORNL) the research from my doctorate studies helped elucidate alignment and described additional effects of electric fields on block copolymer morphologies: reversible alteration of lamellar spacings (converse piezoelectricity), order-order, as well as order-disorder transitions have been described, allowing the precise tuning of block copolymer mesophases without the immediate need of synthetic materials design.

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 Related Publications

  1. Block copolymers in electric fields — C. W. Pester, C. Liedel, M. Ruppel, and A. Böker. Prog. Polym. Sci. 2017, 64, 182.
  2. Piezoelectric properties of non-polar block copolymers — C. W. Pester, M. Ruppel, H. G. Schoberth, K. Schmidt, C. Liedel, P. van Rijn, K. A. Schindler, S. G. Hiltl, T. Czubak, J. Mays, V. S. Urban, and A. Böker. Adv. Mater. 2011, 23, 4047.
  3. Electric field-induced selective disordering in lamellar block copolymers — M. Ruppel, C. W. Pester, K. M. Langner, G. J. A. Sevink, H. G. Schoberth, V. S. Urban, J. Mays and A. Böker. ACS Nano 2013, 7, 3854

 

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