Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Y08: Polymer RheologyLive
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Sponsoring Units: DPOLY Chair: Pinar Akcora, Stevens Inst of Tech |
Friday, March 19, 2021 11:30AM - 11:42AM Live |
Y08.00001: Facile equilibration of fully-entangled semiflexible bead-spring polymer melts Joseph Fox Dietz, Martin Kröger, Robert Hoy Equilibrating model entangled polymer melts is challenging because their longest relaxation times τmax scale as (N/Ne)3.4, where N is their degree of polymerization and Ne is their entanglement length. The well-known double-bridging hybrid (DBH) algorithm reduces these times to τmax ∼ (N/Ne) by performing periodic chain-topology switching Monte Carlo (MC) moves during a molecular dynamics (MD) simulation. For semiflexible chains, however, the high energy barriers associated with these MC moves make the prefactors to this (N/Ne) scaling prohibitively large. Here we overcome this issue by combining DBH with the use of core-softened pair potentials. By beginning with soft pair and bond interactions, and slowly stiffening them until they reach their final functional forms while keeping the equilibrium bond length constant, we are able to equilibrate 400K-monomer systems with N > 20 Ne and chain stiffnesses all the way up to the isotropic-nematic transition, using single-cluster-node simulations that last no more than ∼250 hours. We use this new algorithm to develop improved expressions for Kremer-Grest melts' chain-stiffness-dependent Ne and Kuhn length lK. |
Friday, March 19, 2021 11:42AM - 11:54AM Live |
Y08.00002: Dynamics of bottlebrush polymers in dilute solution Sarit Dutta, Charles Sing Highly branched polymers consisting of a central backbone chain hosting numerous densely grafted side chains, called bottlebrush polymers, have been widely studied for the design and manufacture of self-assembled |
Friday, March 19, 2021 11:54AM - 12:06PM Live |
Y08.00003: Obtaining analytic expressions for entanglement-related properties; does the choice of topological-analysis method matter? Robert Hoy, Joseph D Dietz, Martin Kröger In general, the entanglement length Ne measured by and consequently the plateau modulus G and tube diameter a inferred from topological analyses (TA) of simulated polymeric systems depend strongly and nontrivially on both the computational algorithm used for TA and the mathematical estimator used to extract Ne from the TA data. We show that the recently developed unified analytic expressions [Hoy, R.S. and Kröger, M., Phys. Rev. Lett. 2020, 124, 147801] predicting how the dimensionless quantities Le/lK, Glk3/kBT, and a/lK in dense polymer melts depend on lK/p, where lK and p are respectively the Kuhn and packing lengths, are supported by results from a TA algorithm and Ne-estimator [Svaneborg, C. and Everaers, R., Macromolecules 2020, 53, 1917] that are very different than the ones that were used in the development of these expressions. However, comparison of results from these two methods leads to quantitative corrections for the semiflexible (lK/p > 5) regime as well as new qualitative insights into the relation between primitive path structure and entanglement in this regime. |
Friday, March 19, 2021 12:06PM - 12:18PM Live |
Y08.00004: Measurement of segmental dynamics of polymer glasses in the pre-yield regime ENRAN XING, Trevor Bennin, Josh Ricci, Mark Ediger It has been shown that the segmental dynamics of polymer glasses are accelerated by deformation, but little is known quantitatively about the change of dynamics at a small strain. Here, we modify the photobleaching method by performing a deformation within a single optical measurement and measure the segmental dynamics in the pre-yield regime. The results were compared with two sets of theories. One of them is Fluidity model, which assumes that the effect of deformation on the segmental dynamics is controlled by the absolute value of strain rate. Using cyclic deformation protocols, we show that deformations with the same absolute strain rate but different peak strains affect the segmental dynamics differently. The other set are NLE, Eyring and PFVD models, all of which contain explicit relationships between the change of segmental dynamics and the stress. Here, it’s found that the acceleration of the segmental dynamics falls onto a universal curve with respect to peak strains. By comparing the curve with these models, we find that NLE model gives the best fit, which indicates its functional form of the acceleration-stress relationship can describe a polymer glass in the pre-yield regime most closely. |
Friday, March 19, 2021 12:18PM - 12:30PM Live |
Y08.00005: Construction of a highly coarse-grained model for cis-polybutadiene with slip-springs for rheological properties Ludwig Schneider, Alireza Behbahani, Anastassia Rissanou, Petra Bačová, Pritam Kumar Jana, Wei Li, Manolis Doxastakis, Patrycja Polinska, Craig Burkhart, Vagelis Harmandaris, Marcus Mueller We present a method to use dynamical observables from atomist and Lennard-Jones beads spring simulations to construct a highly coarse-grained model via a top-down parameter matching. |
Friday, March 19, 2021 12:30PM - 12:42PM Live |
Y08.00006: How to measure effect of solvent and charged groups on polymer excluded volume and Kuhn length Michael Jacobs, Ryan Sayko, Andrey Dobrynin Knowledge of solvent effect on polymer excluded volume and Kuhn length is a foundation of scaling analysis of solutions of charged and neutral polymers. Here we present an approach based on scaling relationship between solution correlation length ξ≈lgν/B and number of monomers per correlation blob g for polymers with monomer projection length l. Numerical coefficient B and exponent v are determined by solvent quality for the polymer backbone, chain Kuhn length and type and strength of monomer-monomer interactions at different length scales starting from solutions correlation length down to thermal blob length scales. Values of the B-parameters are obtained from a plateau of normalized specific viscosity ηsp(c)cα/N as a function of monomer concentration c with degree of polymerization N. Exponent α=1/(1-3ν) describes concentration dependence of the number of monomers per correlation blob, g∼cα. This approach allows one to extract excluded volume and Kuhn length as a function of fraction of charged monomers and salt concentration. We illustrate this approach on salt-free solutions of N-methyl-2-vinyl pyridinium chloride random copolymers in ethylene glycol and salt solutions of sodium carboxymethyl cellulose in water. |
Friday, March 19, 2021 12:42PM - 12:54PM Live |
Y08.00007: Physically Intuitive Continuum Mechanics Model for QCM Applied to Obtain the Frequency-Dependent Storage and Loss Modulus of PDMS Within the Glass Transition Regime Yannic Gagnon, Justin Burton, Connie Roth Quartz crystal microbalances (QCMs) are increasingly applied as MHz-rheometers to measure viscoelastic properties of films beyond the simple Sauerbrey equation relating frequency shifts to mass loading of the crystal. Much QCM modeling in the literature applies mathematical simplifications such as the small load approximation to analytically solve for frequency shifts as a function of harmonic number, which cannot be applied to situations in which the frequency shift is large. In addition, many models utilize equivalent circuit formalisms, losing their physics intuition to the sample’s material properties. We present a continuum mechanics model with no mathematical approximations that numerically solves for the viscoelastic properties of the polymer, while preserving the model’s intuitive physics formulation. By incorporating frequency-dependent moduli, we are able to model polydimethylsiloxane (PDMS) films within the glass transition regime, obtaining good agreement with interpolated literature values of the rubbery and glassy plateau regimes from dynamic mechanical analysis (DMA). |
Friday, March 19, 2021 12:54PM - 1:06PM Live |
Y08.00008: Dynamics and Rheology of cis-1,4-Polybutadiene melts through Systematic Bottom-up Coarse-grained Simulations Alireza Foroozani Behbahani, Ludwig Schneider, Anastassia Rissanou, Antonis Chazirakis, Petra Bačová, Pritam Kumar Jana, Wei Li, Manolis Doxastakis, Patrycja Polinska, Craig Burkhart, Marcus Mueller, Vagelis Harmandaris Due to the broad range of time and length scales involved, the simulation of high molecular weight polymer melts is not straightforward. |
Friday, March 19, 2021 1:06PM - 1:18PM Live |
Y08.00009: Dynamic adsorption influences drop and bubble formation of Polymer Surfactant Complexes Carina Martinez, Thomas Mazur, Vivek Sharma Surface tension of a freshly created interface varies due to dynamic adsorption that is intimately linked with the rate of mass transfer of surfactant from liquid sub-phase to the interface, and this adsorption-limited kinetics impacts the formation of drops and bubbles. Complexation of a neutral polymer to an ionic surfactant in solution influences dynamic adsorption, surface tension and bulk rheological response. Dynamic surface tension refers to the time dependent variation in surface tension, that can be characterized using conventional methods like pendant drop analysis, Wilhelmy plate, etc. However, the conventional methods are limited in their temporal resolution. In this study, we utilize maximum bubble pressure tensiometry for the measurement of dynamic surface tension at extremely short (1-50 ms) timescales. We characterize the adsorption kinetics of charged surfactants as well as surfactant-polymer complexes. We characterize the pinch-off dynamics of bubbles and drops to determine the influence of shear and extensional rheology behavior as well as dynamic adsorption on foamability, emulsion formation and processability. |
Friday, March 19, 2021 1:18PM - 1:30PM Live |
Y08.00010: Rheology of entangled solutions of ring-linear DNA blends Dejie Kong, Sourya Banik, Michael San Francisco, Rae M Robertson-Anderson, Charles M Schroeder, Gregory B McKenna The rheological response of ring polymers remains poorly understood, and even small amounts of linear chains can have large effects on their behavior. In this work, we use monodisperse ring DNA polymers (45 kbp, 2.9 x 107 g/mol) to investigate the importance of linear chains in the rheology of ring-linear blends. Linear viscoelastic measurements have been made on ring-linear DNA solutions at various concentrations with different linear chain ratios and the responses compared to those of linear λ DNA (48.5 kbp) solutions. Because of the linear threading effects, the blends have a significantly higher zero-shear rate viscosity and a much broader rubbery regime than that of the linear polymer. Furthermore, a linear ratio of 0.5 is a threshold at which the magnitude of the plateau modulus GN0 tends towards that of the linear counterpart. However, independent of the linear content, the power law dependences of GN0 on total concentration for the blends are the same as that of the linear solutions. We also find that the Cox-Merz rule holds for the linear-ring topology. |
Friday, March 19, 2021 1:30PM - 1:42PM Live |
Y08.00011: Anomalous nonlinear rheological responses of nanocomposites: the transition to linear-nonlinear dichotomy Jinying Zou, Xiaorong Wang We found an anomalous nonlinear behavior under large amplitude oscillatory shears, where the amplitude stress deviates strongly from the linear dependence of strain, while the time dependence of stress remains sinusoidal. This phenomenon is usually accompanied with the Payne effect of filled rubbers. In order to understand the molecular details regarding this unusual behavior, we examined a series of polybutadiene/tetradecane solutions filled with carbon black. Our results show that there is a previously unrecognized transition in the system as the matrix polymer concentration φ approaches and passes through a characteristic polymer concentration φc. Below φc, the system typically shows the classic nonlinearity, where storage modulus G’ decreases as strain amplitude γ0 increases and the resulting stress waveforms are distorted from sinusoidal waves. Above φc, the system displays an anomalous nonlinearity, where the stress responses at any given strain remain surprisingly sinusoidal regardless the drop of storage modulus G’. The critical concentration φc is about an order of magnitude greater than the entanglement polymer concentration φe. The degree of entanglement in the matrix apparently determines the occurrence of this unusual rheological event and plays a key role here. |
Friday, March 19, 2021 1:42PM - 1:54PM Live |
Y08.00012: Influence of Graft Density on the Viscoelastic Properties of Polymer Grafted Nanocomposites Andrew Ehlers, Pinar Akcora, Rahmi Ozisik Molecular dynamic simulations are used to investigate the dynamics and viscoelastic properties of polymer grafted nanocomposites (PGNs). In the current study, the PGN consists of a nanoparticle with grafted high-Tg polymer chains in a low-Tg polymer matrix. These types of PGNs have been shown to have reversible and repeatable stiffening behavior upon heating (Senses, E.; Isherwood, A.; Akcora, P. ACS Appl. Mater. Interfaces 2015, 7, 14682). The interface between the grafted and matrix polymers may influence chain dynamics and viscoelastic properties of the whole system. The influence of the graft density and graft chain stiffness on viscoelastic properties is investigated to identify the mechanism of the observed stiffening in these types of PGNs. |
Friday, March 19, 2021 1:54PM - 2:06PM Live |
Y08.00013: Single-molecule imaging of tube nonlinearities for sheared, entangled F-actin chains Kaikai Zheng, Zitong Zhang, Bingyang Cao, Steve Granick A homebuilt setup for single-molecule epifluorescence imaging under controlled rheological shear is used to accomplish single-molecule imaging of entangled F-actin solutions. We find “tube softening” at low shear rate and “tube hardening” at high shear rate. Surprisingly, “tube softening” and “tube hardening” are quantitatively related to chain alignment and chain stretching, respectively – quantities that are inaccessible using conventional ensemble-averaged methods. |
Friday, March 19, 2021 2:06PM - 2:18PM Live |
Y08.00014: Shear and extensional rheology of highly entangled cyclic polymer in melts and solutions Dongjie Chen, Gregory B McKenna, Judit E Puskas, Carin A Helfer, Kristof Molnar, Gabor Kaszas, Juile A Kornfield Rheology of circular polymers remains an area of active research due to the difficulty of making ring polymers of sufficient purity free of linear contaminants. Past work has been limited to rings made in dilute solution and, consequently, have been limited to sizes of approximately 15 entanglements in the linear analog and small amounts of material being available for study. These problems have been overcome by reversible radical recombination polymerization (R3P) recently developed in Puskas laboratory. R3P can produce 10-100g scale circular polymer which opens new avenues of research. Here we have studied poly(3,6-dioxa-1,8-octanedithiol) (PolyDODT) and Polyisobutylene disulfide synthesized by R3P of different molecular weights. Of interest is that the largest PolyDODT ring investigated to date has a molecular mass corresponding to approximately 300 entanglements in the linear counterpart. The extensional rheology behavior of cyclic PIB-disulfide and cyclic PolyDODT is compared with that of linear PIB and literature data of Polystyrene ring. Linear and nonlinear shear responses of the cyclic PIB-disulfide melts, cyclic PolyDODT melts and solutions are compared with literature results published since 1980s. |
Friday, March 19, 2021 2:18PM - 2:30PM Live |
Y08.00015: Rheology and scaling of concentrated linear DNA solutions Sourya Banik, Dejie Kong, Michael San Francisco, Gregory B McKenna We have studied the flow and entanglement behavior of concentrated monodisperse linear lambda DNA, MW ~ 3.2x107 g/mol in solution. Dynamic tests on solutions of having concentrations from 0.47 to 3.75 mg/ml DNA in an aqueous buffer showed a rubbery plateau modulus, GN0 that scales with concentration as C2.24. Two distinct zones in the behavior of the relaxation time, τD against concentration are observed: scaling as C~0.88 and C~3.55 in low and high concentration regimes, respectively. The Cox-Merz rule and the time concentration superposition were established to follow in the range of concentrations studied. The damping function was obtained for different concentrations following stress relaxation experiments. The samples showed an increase in softening with strain as concentration increases. The entanglement behavior was found to be similar to that of synthetic melts and solutions. |
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