Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F04: Beyond Linear: Structure, Dynamics, Response and Unique Properties of Topological Polymers IFocus
|
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Ting Ge, University of South Carolina Room: Room 127 |
Tuesday, March 7, 2023 8:00AM - 8:36AM |
F04.00001: Break
|
Tuesday, March 7, 2023 8:36AM - 9:12AM |
F04.00002: Concentration-superposition meets the challenge of validating very large rings Invited Speaker: Julie A Kornfield Valuable properties of linear polymers emerge when their molecular weight is several times their entanglement molecular weight, Me,lin, providing a strong impetus to examine cyclic polymers that have Mw / Me,lin ≡ Zw >> 1. This regime has proven difficult to reach. Some molecular structures enable preparation of pure rings, but have a highest accessible Zw < 15. Synthesis strategies that produce rings of Zw >> 15 confront the difficulty of proving that there are <1% linear chain contaminants. This talk deals with such a case: putative rings produced by Reversible Radical Recombination Polymerization (R3P) up to Zw = 300·Me,lin. We use dilution to increase Me(φ) without modifying topology. Using samples that have Zw = 301 and 219 in the melt, we present results for solutions of 2.5% and 1% that have Zw < 15 and show their accord with highly purified rings. Examining concentrations from 5% to 50% reveal unanticipated, qualitative changes in the relaxation dynamics as Zw increases from 30 to 300—a previously unexplored regime for cyclic polymers. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F04.00003: Uniaxial Elongational Flow of Ring-Polymer Melts with Associating Groups John M Bracewell, Supun S Mohottalalage, Dvora Perahia, Gary S Grest, Thomas O'Connor Recent studies of effects of uniaxial extensional flows on linear polymers, driven by polymer processing challenges, have raised several fundamental questions regarding the impact of entanglements. Non-concatenated ring polymers, which have no free ends, do not entangle like linear polymers, thus serve as an excellent model for understanding flow response. Previous studies found that links formed spontaneously in the ring system under extensional flow, which led to the unexpected large increases in extensional viscosity observed experimentally. Associating groups were added to the bead-spring model to determine their effect on the formation of these topological links. The fraction of associating groups was varied from 2% to 10%, and association strength was varied from 1–10kBT. As for linear chains, the associating groups form clusters, which increase in size as the strength of the associating groups increase. These clusters are dynamic under flow, continuously breaking up and reforming. They govern the distribution of ring extensions which become heterogeneous for strongly interacting associating groups. Even for large interaction strength, some rings still form topological links, in which case the viscosity is due to a combination of these linked rings and the associating groups. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F04.00004: Entanglement length scale separates threading from branching of unknotted and non-concatenated ring polymers in melts Mattia Alberto Ubertini, Jan Smrek, Angelo Rosa We look at the structure and dynamics of unknotted and non-concatenated ring polymers in melt conditions and investigate the interplay between double folding and threadings. Double folding is postulated in current theories which describe the ring as a tree-like double folded object, and evidence of this are supported from simulations on a single ring level. In contrast threadings, penetration of a ring through the surface of another ring, are neglected by theories but recent works show that they are present and may be fundamental for the dynamics of such systems. In this work, we reconcile this dichotomy using Monte-Carlo simulations of the ring melts with different bending rigidity. We find that rings are indeed double folded (more strongly for stiffer rings) on and above the entanglement length scale, while threadings are localized on smaller scales. In the stiffer melts we show the first evidence of the presence of an underlying tree-like structure with self avoiding walk statistics, while more flexible chains do not show this feature. As for the threadings, despite they create only a small opening in the double folded structure, the threading loops can be numerous and their length can exceed substantially the entanglement scale. We link the threading constraints to the divergence of the relaxation time when a fraction of rings are pinned. Current theories do not predict such divergence and predict faster than measured diffusion of rings, pointing at the relevance of the threading constraints in unpinned systems as well. Finally, revision of the theories with explicit threading constraints might elucidate the validity of the conjectured existence of topological glass. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F04.00005: Statics of Diblock Ring Polymers in Lamellar Phase: A Study Combining Molecular Simulations and Scaling Analysis Andrew S Wijesekera, Ting Ge Ingenious synthesis and precise characterization of non-concatenated ring polymers propel the idea of using polymer topology as a new pathway to achieve desirable nanostructures for polymer-based templating and membrane applications. Extensive molecular simulations are performed to study the static properties of diblock ring polymer melts in the lamellar phase. The self-similar dynamics of non-concatenated ring polymers, which are much faster than the entangled dynamics of linear polymers, facilitate the transition from the disordered phase to the lamellar phase. The lamellar spacing d and the interfacial width w for the structure equilibrated at constant pressure are computed as functions of both the ring polymer contour length N and the χ parameter for the interactions between the two blocks. The simulation results agree with the scaling analysis based on the self-similar loopy globular conformations of non-concatenated ring polymers. A further comparison with the lamellar phase of diblock linear polymer melts with chain length N/2 shows that d is reduced for the diblock ring polymers at the same value of χ, manifesting the topological interactions that make non-concatenated ring polymers more compact than the random-walk conformations. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F04.00006: AFM investigation of Topological and Physical Properties of Kinetoplast DNA Maria Maalouf, Ryan Blair, Alexander R Klotz Kinetoplast DNA (kDNA) is a two-dimensional network of topologically linked DNA molecules found in trypanosome parasites. Studying kDNA can improve our understanding of polymer |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F04.00007: Entropy of Insertion, Not Pore Jamming, Controls Polycatenane Translocation Dynamics Zifeng Wang, Mesfin Tsige, Robert M Ziolek Catenanes are a mechanically interlocked molecular architecture consisting of two or more consecutively interlocked macrocycles. They play an important role in applications that range from molecular machines and switches to catalysis and drug delivery underpinned by their unique topological structure. Polymer translocation applications have also been widely studied, such that the phenomenon of polycatenane translocation can be applied to various tasks such as low-cost characterization, controlled drug delivery, and rapid DNA sequencing. This talk will discuss the translocation dynamics of a polycatenane passing through a small nanopore under an external driving force using Langevin dynamics simulations. The simulations reveal the translocation dynamics are controlled by the entropy of insertion into the pore, rather than simple pore jamming. In addition, the size of the pore radius greatly affects the mean translocation time especially in the small pore limit. We observe a huge jump in the translocation time at a critical pore radius. No power law-type behavior (which is typically deduced from studies of translocation in larger pore sizes) can account for this highly non-linear pore size dependent behavior. We explain this abnormality by thorough statistical analysis of the translocation of the polycatenane knots, and the orientation of the polycatenane during the translocation process. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F04.00008: Effect of rings stiffness and steric interactions on the static and dynamics of linear catenanes Pietro Chiarantoni, Cristian Micheletti Using molecular dynamics, we study how the bending rigidity of the constituent rings affects the static and dynamics of isolated, interacting, and spatially-confined linear catenanes. For the isolated case, we show that stiffer rings yield catenanes with a more flexible backbone and slower relaxation dynamics at all length scales. We rationalize the results by separating the contributions of rings' shape and steric interactions to the backbone rigidity and by comparing the properties of (mechanically-bonded) catenanes to those of equivalent (covalently-bonded) polymers. We next consider the diffusivity of interacting catenanes, which is strongly impacted by rings' rigidity, even in the semi-dilute case. Finally, we turn to catenanes in spatial confinement and discuss how their morphology and relaxation dynamics respond to the degree of confinement. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F04.00009: Theta-Temperature Depression in 2-catenane Polymer Investigated by Simulation Hao Guo, Kun Qian, Mesfin Tsige Recent studies have shown that a ring polymer in solution exhibits a lower theta temperature than its linear analog because of topological effect. We have investigated the effect of having two rings in the theta temperature of 2-catenane polymer, a molecular architecture consisting of two mechanically interlocked ring polymers. The mechanical bonds in catenated polymer brings extra rotational freedoms to the chain which could result in several unique properties of the polymer. The theta temperature is expected to be depressed more in catenated polymers. Nevertheless, to the best of our knowledge, this hypothesis has not been thoroughly examined through simulation or experiment. Using coarse-grained Molecular Dynamics Simulation, we have investigated the solution properties of 2-catenane polymer and compared it with that of trivial ring polymer and linear polymer. The theta temperature depression of 2-catenane is confirmed from our simulation. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F04.00010: A new method for characterizing the structure of knotted polymers Franco Ferrari, Luca Tubiana, Neda Abbasi Taklimi, Marcin R Piatek Numerical simulations based on Monte Carlo methods often require the sampling of millions of polymer conformations. For this reason, it is hard to capture the main features that characterize polymer conformations of given energy or at a given temperature. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700