Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D19: Polymer Brushes and Functional InterfacesFocus Recordings Available
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Sponsoring Units: DPOLY Chair: Christian Pester, Penn State Room: McCormick Place W-185A |
Monday, March 14, 2022 3:00PM - 3:36PM |
D19.00001: Fundamentals and Applications of Polymer Brushes in Air Invited Speaker: Sissi De Beer While polymer brushes in liquid have been researched intensively for several decades, the properties of brushes in air have only recently caught the attention of scientists. The reason for this is that several applications of brushes in air are currently being explored, such as in electronic noses or in gas separations. In this presentation, I will provide a microscopic picture of vapor-solvation of different types of brushes. By combining molecular dynamics simulations with neutron reflectometry measurements, atomic force microscopy and ellipsometry experiments, I will show that solvent-partitioning and thereby the mechanical properties of brushes strongly depend on the polymer-solvent affinity. In addition, I will evaluate differences between brushes and free polymer films. Based on these fundamental insights, I will propose optimal design parameters for application of brushes in sensing and separations technologies in air. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D19.00002: Free Energy for Adhesion of Nanocarriers to Endothelial Cells Saeed Akbari, Shaghayegh Khani, Joao M Maia Targeted drug delivery of functionalized nanocarriers (NCs) is a very critical technique in therapeutic and diagnosis treatments. However design of NCs for targeting to endothelial cells is still a biomedical and pharmacological challenge. Using dissipative particle dynamics simulations, herein we suggest a feasible method for accounting for the majority of parameters that control the adhesion process, including the impact of endothelial glycocalyx (EG) layer, namely its height and structure if both EG chains and receptors. In this presentation, the effects of NCs geometry (size, shape and orientation) and surface chemistry (ligand density, composition and flexibility) on their interactions with solvent, substrate, receptors and chains of the EG layer are investigated. Through studying the morphology and dynamics, the relation of EG layer expansion and movement of NCs inside the EG layer toward the receptor is investigated. To understand this adhesion process, the variation of inclusion free energy of NCs is explored. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D19.00003: Arbitrarily curved polymer brushes and their end-exclusion zones Michael S Dimitriyev, Gregory M Grason Surface-grafted polymer brushes are seen in a wide verity of scenarios, ranging from coated nanoparticles to complex block copolymer phases. Their substrates can take on just about any shape, from highly curved spheres to gyrating saddles. In many of these situations, chain ends can exist anywhere within the brush and the thermodynamics are well-modeled by the parabolic brush theory (PBT). However, when a convex substrate curvature forces brush ends to splay outward, chain ends are depleted away from the substrate, resulting in an "end-exclusion zone" (EEZ) that is inconsistent with the PBT. Here, we generalize previous descriptions of the EEZ that were limited to spherical and cylindrical surfaces to surfaces of arbitrary curvature. We find that the combination of surface curvatures contribute to non-local adjustments to chain packing constraints, either promoting EEZ growth or depressing it, which in turn affects the chain end distribution and the local polar order of chains. Finally, we explore the consequences of EEZ corrections on the stability of complex block copolymer phases. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D19.00004: Durable anti-fogging coatings via surface-initiated photopolymerization Christian W Pester The covalent attachment of polymers has emerged as a powerful strategy for the preparation of multi-functional surfaces. Patterned, surface-grafted polymer brushes provide spatial control over a variety of physical properties and allow for fabrication of ‘intelligent’ substrates which selectively adapt to their environment. However, the route towards such patterned polymer brush surfaces often remains challenging, creating a demand for more efficient and less complicated fabrication strategies. Here, we describe recent advances in our group in reduction photolithography to produce topographically and chemically pattern polymer brushes by using light-mediated controlled radical polymerization. We highlight the use of these approaches to engineer durable polymer brush films with functional surface properties, specifically anti-fogging activity. Further, we highlight recent work on a facile photolithography setup based on LED digital light projection as an inexpensive, push-of-a-button platform for topographically and chemically patterned surfaces under ambient conditions and open to air. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D19.00005: Stimulus-Responsive Microphase-Separation of Resilin/Elastin Block-Copolypeptides in Solution and on Surfaces Stefan Zauscher, Ashutosh Chilkoti, Michael Gradzielski, Luis A Navarro, Justin Ryan, Michael Dzuricky We investigated the self-assembly of a series of stimulus-responsive block copolypeptides (BCPs) composed of a hydrophobic, resilin-like domain and a hydrophilic, elastin-like domain in the bulk and on surfaces using small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). We observed classical, microphase-separated nanostructures, such as hexagonally-packed cylinders and alternating lamella, in concentrated solutions of the block copolypeptides. The emergence of these nanostructures was strongly dependent on copolymer composition and temperature. Discrete order-order transitions were observed for higher molecular weight species, and order-disorder transitions were observed with increasing temperature for all species due to the lower-critical solution behavior of the elastin-like block. BCP thin-films also exhibited microphase-separated nanostructures that resembled those in solution. and could be further refined by annealing in a high humidity environment, resulting in long-range, periodic nanostructures. For example, these structures can function as templates to guide the self-assembly of molecules or other nanoscale objects, and thus enable a broad range of biocatalytic, bioelectronic, or assay devices. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D19.00006: Importance of the Polymer Ligand Conformation to the Assembly of Nanoparticles within Emulsion-Evaporative Block Copolymer Particles Meng Xu, Hongseok Yun, Bumjoon J Kim The conformation of polymer brushes highly affects the interactions between ligand-grafted nanoparticles and polymer matrices, thus determining the nanostructures of hybrid materials. Herein, we demonstrated the precise spatial alignment of polystyrene-grafted Au nanoparticles (Au@PS) within onion-like polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) particles depending on the parameters related to the conformation of PS ligands, including the ratio of PS block molecular weight (Mn) to PS ligand Mn (P/N), core size of Au@PS (r), and grafting density of PS ligands (σ). Change in any of these parameters drives dramatic morphological transitions of hybrid particles. PS ligands having low interfacial interactions with BCP chains were excluded from the BCP domains and formed hexagonal packing on the particle surface. In contrast, high interfacial interactions between Au@PS and BCP chains allowed the formation of Au@PS arrays between PS blocks. The phenomena were explained by considering the ligand architecture directed-interdigitation and swelling behavior between grafted polymer and matrix polymer. In addition, the effect of nanoparticle size was also taken into account for a comprehensive understanding of the entropic interactions in a BCP-based hybrid system. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D19.00007: nano-FTIR for probing molecule orientation and conformation in thin polymer brush films with nanoscale spatial resolution Tobias Gokus, Adrian Cernescu The properties of ultrathin functional surface coatings such as polymer brushes strongly depends on orientation and conformation of their polymer chains. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D19.00008: Quantum-optical brushes: active control of strong plasmon-exciton coupling in programmable biomimetic pigment-polymer antenna complexes grown by surface-initiated polymerisation from gold nanostructures Graham J Leggett, Anna Lishcuk, Evelin Csanyi Theory suggests that exciton diffusion lengths in molecular materials could be enhanced by several orders of magnitude in the strong light-matter coupling regime. Photosynthetic light-harvesting complexes (LHCs) from plants and bacteria are strongly coupled to localised surface plasmon resonances (LSPRs) in gold nanostructure arrays, yielding delocalised states (plexcitons) that mix the properties of light and matter. However, proteins are not suitable for putative applications of molecular photonic materials. Here we demonstrate the fabrication of programmable, biomimetic plexcitonic antenna complexes, in which poly(amino acid methacrylate) scaffolds grown by atom-transfer radical polymerisation organise chlorophylls within LSPRs to achieve strong light-matter coupling. Modelling the system as coupled oscillators yields Rabi energies up to twice those achieved with LHCs. The energies of the plexcitons are programmed by varying the degree of polymerisation, scaffold packing density and chlorophyll loading. Moreover, synthetic plexcitonic antenna complexes display pH and temperature responsiveness, facilitating active control of strong plasmon-exciton coupling. Programmable plexcitonic antenna complexes offer promise as a new kind of biologically-inspired metamaterial. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D19.00009: The importance of charge regulation for DNA-like polymer layers in a physiological intranuclear environment: effect of mono- and multivalent cations Rikkert J Nap, Ranya K Virk, Marcelo A Carignano, Vadim Backman, Igal G Szleifer The highly negative charge of DNA is not fully neutralized when it packages into chromatin in the nucleus. Thus, the physicochemical environment, including intracellular cations, pH, and DNA density, is expected to have a large influence on chromatin packing. Here, we use a molecular theoretical approach to determine how the packing and charge of DNA-like tethered polyelectrolytes change in response to changing environmental conditions. Overall, we found that Mg2+, the most prevalent multivalent cation in the cell, has a large effect on the density distribution as well as the effective charge of the polyelectrolyte, whereas monovalent cations have lesser effects on both the structure and charge of the DNA-like system. This larger effect of Mg2+ ions is caused by the possibility of Mg2+ forming an ion bridge with two negatively charged DNA phosphates, which results in charge neutralization/reduction, polymer collapse, and increased polymer density. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D19.00010: Interaction potential for coarse-grained models of bottlebrush polymers Tianyuan Pan, Sarit Dutta, Charles E Sing Bottlebrush polymers are a class of highly-branched macromolecules that show promise for applications such as self-assembled photonic materials and tunable elastomers. However, computational studies of bottlebrush polymer solutions and melts remain challenging due to the high computational cost involved in explicitly accounting for the presence of side chains. Here we consider a coarse-grained molecular model of bottlebrush polymers where the side chains are modeled implicitly, with the aim of expediting simulations by accessing longer length and time scales. The key ingredients of this model are the size of a coarse-grained segment and a suitably coarse-grained interaction potential between the non-bonded segments. Our previous studies have not focused on developing explicit forms of such potentials, instead relying on non-specific analytical functions to model non-bonded interactions. Here we show how to systematically calculate an interaction potential between the coarse-grained segments of bottlebrush from finer grained explicit side chain models using Monte Carlo and Brownian Dynamics, and then incorporate it into an implicit side chain model. We compare the predictions from our coarse-grained implicit side chain model with those obtained from models with explicit side chains in terms of the potential of mean force, the osmotic second virial coefficient and the interpenetration function, highlighting the range of applicability and limitations of the coarse-grained representation. Though presented in the context of homopolymer bottlebrushes in athermal solvents, our proposed method can be extended to other solvent conditions as well as to different monomer chemistries. We expect our implicit side chain model will prove useful for accelerating large-scale simulations of bottlebrush solutions and assembly. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D19.00011: Neutron characterization of stimuli-responsive polymer brushes for nanofluidic gating Hadi Rahmaninejad, Andrew J Parnell, Thomas H Sexton, John F Ankner, Wei-Liang Chen, Wim Bras, Christopher K Ober, Anthony J Ryan, Rana Ashkar |
Monday, March 14, 2022 5:36PM - 5:48PM |
D19.00012: Understanding Strong Hydration, Salt-Resistance, and Antibiofouling of Zwitterionic Materials from Ab Initio Simulations Pranab Sarker, Tao Wei Zwitterions are emerging affordable antibiofouling candidates due to their strong hydration and resistance against salt molecules. The robust hydration introduces physical and energetical barriers, preventing biomolecules from attaching to the surfaces. Experimentally, their antifouling efficacies increase as the separation between the two oppositely charged head groups decreases. However, how zwitterionic separation controls the hydration is not known to date. We employ ab initio molecular dynamics (AIMD) and symmetry-adapted perturbation theory (SAPT) to investigate hydration of different zwitterions with varied separation. Our results reveal that zwitterionic hydrations are primarily governed by the hydrogen bonds between zwitterionic oxygens and water hydrogens, the strengths of which vary with the zwitterionic gaps. The bond strength is the strongest when the zwitterionic gap vanishes, as quantified by the quantum theory of atoms in molecules (QTAIM) analysis. Our SAPT analysis further demonstrates that the electrostatic interaction is the dominating attractive component in the hydrogen-bond makeup and highest for the shortest zwitterionic gap material. Our results explain why TMAO exhibits strong salt-resistance and antibiofouling efficacy against proteins. |
Monday, March 14, 2022 5:48PM - 6:00PM |
D19.00013: Assembly Behavior of Bottlebrush Random Copolymers at the Water/Toluene Interface Hong-Gyu Seong, Zhan Chen, Todd S Emrick, Thomas P Russell We investigated the assembly of bottlebrush random copolymers (BRCPs) at the water/toluene interface. BRCPs with poly(dimethylsiloxane) (PDMS, hydrophobic) and poly(ethylene oxide) (PEO, hydrophilic) as the sidechains were synthesized by ring-opening metathesis polymerization using ruthenium benzylidene catalysis. Our experiments showed a strong relationship between the interfacial assembly kinetics and the molecular weight of the polymer. The relaxation behavior was investigated further by fitting the interfacial tension (IFT) vs time plot with two exponential decay functions to extract two characteristic relaxation times. The results showed that the relaxation time for BRCP adsorption to the fluid-fluid interface increased, while the relaxation time associated with reconfiguration of the polymers decreased with increasing molecular weight. We further investigated the time-dependent relaxation behavior and the collective diffusion coefficient by fluorescence recovery after patterned photobleaching (FRAPP). The results provide both fundamental understanding of the interplay between molecular weight and assembly behavior at liquid interfaces, and the generalized design rules for bottlebrush polymers as surfactants. |
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