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 Q03: Programmed Responsive Polymers and Soft Matter IIFocus
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Sponsoring Units: DPOLY Chair: Liheng Cai, University of Virginia Room: Room 126 |
Wednesday, March 8, 2023 3:00PM - 3:12PM |
Q03.00001: Magneto-active check valve with a reprogrammable cracking pressure Chaemin Kim, Anna Lee The check valve is essential for controlling flow direction, flow rate, and pressure distribution in a fluidic system. The pressure at which the flap opens in the check valve, called cracking pressure, is fixed because it depends on the material and geometry of the valve. Therefore, reasonable reprogramming of the cracking pressure allows a single check valve to operate in various scenarios and systems. Here, we fabricate a magneto-active check valve using a magneto-active elastomer. The magnetic force applied to the magneto-active check valve was diversified by changing the direction and magnitude of the current along the Maxwell coil. Our experiments on the actuation of a magneto-active check valve under various magnetic forces demonstrate the re-programmability of cracking pressure. We also theoretically analyze the mechanical response of the flap subjected to the gravitational force, magnetic force, and flow pressure. Furthermore, we predict the cracking pressure, defined as the inlet pressure when the contact force becomes zero between the flap and the stopper, by conducting finite element simulations. Experimental, theoretical, and numerical results well-agree with each other, implying that the cracking pressure of check valves can be dynamically controlled within a specific range. Consequently, we expect our new active and passive check valves to be designable for various needs in diverse fields, from drug delivery to gas separation systems. |
Wednesday, March 8, 2023 3:12PM - 3:24PM |
Q03.00002: polymeric nanoparticles with dual responsive interlayers Jeonghun Lee, KARLA CURENO HERNANDEZ, Sunghoon Kim, Margarita Herrera-Alonso Stimuli-responsive nanoparticles play a crucial role in many applications where on-demand effects are desirable, including drug delivery systems. Boronic acid-based systems are of particular interest for their ability to hydrogen bond intra/intermolecularly, but also to bind with diol/catechol moieties as a dynamic covalent (DC) interaction in a pH-dependent manner. Boronic acids, therefore, have great potential to be embedded in polymeric constructs as interlayers in order to perform programmed responsive operations triggered by pH and oxidative stress. We developed linear and bottlebrush amphiphiles with boronic acid blocks as interlayers. Nanoparticles from linear polymers were utilized to study hydrogen bonding effects on controlled release of a model hydrophobic solute. Nanoparticles from bottlebrushes were studied in the context of interlayer crosslinking effects with diol-containing crosslinkers in a stimuli-responsive manner. We discuss the effects of the self-assembly method (e.g., rapid nanoprecipitation vs. direct dissolution) on the physicochemical properties of the resulting nanoparticles. In addition, we studied the mixing process with stabilizers and evaluated the programmed responsiveness of nanoparticles under different pH and oxidative conditions to evaluate solute release kinetics. In summary, boronic acid-based nanoparticles hold great potential for pH and oxidative stress-responsive systems for environmentally-triggered release applications. |
Wednesday, March 8, 2023 3:24PM - 3:36PM |
Q03.00003: Photocontrol of pattern formation and hysteresis loops in polymer gels with host-guest interactions Olga Kuksenok, Yao Xiong Pattern formation and reconstruction under external stresses plays an important role in defining functionality of a broad range of soft confined systems. We focus on dynamic control of pattern formation in hydrogels with host-guest interactions. We extend the three-dimensional gel Lattice Spring Model (gLSM) to capture the dynamics of the PNIPAAm hydrogels with pendant azobenzene moieties immersed into alpha-cyclodextrins (alpha-CD) solutions. While trans-azobenzene moieties are recognized and accommodated by the alpha-CD cavities to form inclusion complexes, an exposure to UV light drives the trans-to-cis photoisomerization and dissociation of the complexes. First we demonstrate that the proposed model reproduces volume phase transitions in azobenzene-functionalized hydrogels with host-guest interactions observed in prior experiments. We then use spaciotemporal variations in UV irradiation to control pattern formation in thin hydrogel films under the rigid and soft confinements and to control hysteresis loops. The soft confinement is introduced via illuminating the ridges of the thin samples and thereby introducing localized regions with higher rigidity. We show that controllable feedback mechanisms can be introduced into the networks with host-guest interactions via well-defined illumination patterns. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q03.00004: A hybrid in-silico and experimental kinetics study of glycidyl methacrylate-functionalized N-vinylcaprolactam microgel synthesis Thomas Nevolianis, Nadja Wolter, Luise Kaven, Lukas Krep, Can Huang, Adel Mhamdi, Alexander Mitsos, Andrij Pich, Kai Leonhard The synthesis of microgels with new functionalities is vital for a variety of applications, e.g., in drug release systems[1] and enzyme immobilization[2]; however, the synthesis kinetics of microgels remain largely unknown. In this contribution, we study the synthesis of glycidyl methacrylate-functionalized N-vinylcaprolactam-based microgels. A hybrid approach using quantum chemical calculations and experimental data allows us to estimate parameter values for unknown reaction rates in the existing synthesis model[3]. Using quantum mechanics, we compute gas-phase propagation rate constants and enthalpies of the underlying polymerization reactions at B2PLYPD3/aug-cc-pVTZ and B3LYPD3/tzvp level of theory for the energies and geometries, respectively. Solvation effects based on COSMO-RS are incorporated to obtain liquid-phase reaction rate constants and enthalpies. Using reaction calorimetry measurements and the mechanistic process model, we estimate seven out of twenty-one reaction parameters. As a result of our hybrid approach, we find a coefficient of determination of 0.97 for the enthalpy transfer rate during microgel synthesis. In the future, the fully identified model will help determine the optimal pVCL/GMA microgel synthesis conditions. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q03.00005: Polymer chains via control of intermolecular assembly pathway of peptide bundlemers Yao Tang, Kenneth Crane-Moscowitz, Nairiti J Sinha, Rui Guo, Jeffery G Saven, Christopher J Kloxin, Darrin J Pochan Peptides were computationally designed to self-assemble into homotetrameric, anti-parallel coiled coils, or 'bundlemers'. Specifically, peptides with a net +4 charge per peptide, or +16 per tetrameric bundlemer, were synthesized and modified with a thiol (via incorporation of cysteine as the N-terminal amino acid) or maleimide (via incorporation at the N-terminus). When in water, the respective thiol or maleimide functionalized peptide assembled into coiled-coil bundlemer particles. When the thiol and maleimide functionalized bundlers were subsequently mixed, a thiol-Michael 'click' reaction created polymer chains with extreme rigidity from bundlemer building blocks. Utilizing organic solvent, the same rigid polymer chains can form with a separate, unique assembly pathway. The thiol and maleimide functionalized chains were first dissolved in organic solvent and conjugated together. Subsequent water titration causes the peptides to physically self-assemble into the same coiled-coil rigid chains. This alternate pathway provides direct insight into the stability of the coiled-coil bundles in organic solvent as well as kinetic control of the rigid rod polymer formation on physical assembly with water titration. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q03.00006: Stimuli-Triggered Stereoselective Relaxations in Diels-Alder Polymer Networks Svetlana A Sukhishvili Diels-Alder polymers (DAP) networks have the unique ability to reconfigure their permanent shape through the mechanism of network plasticity with minimal macroscopic creep. Using a combination of DSC and variable-temperature FTIR techniques, we demonstrate that the rate of bond reshuffling is dependent on the stereochemistry of DA junctions and that this rate is faster for endo DA isomers as compared to their exo counterparts. We quantify the process of temperature-dependent conversion of endo to exo isomers, relate it with Young’s moduli, degree of strain recovery, and rates of stress relaxation in DAP materials, and compare the results with those obtained with permanently crosslinked networks. Temperature annealing of as-prepared DAP networks results in all-exo materials with enhanced mechanical properties and improved strain recovery. Further control of the relaxation through network rigidity and crosslinking density enables designing and constructing DAP multi-material constructs with programmable stress-induced and temperature-induced deformations. |
Wednesday, March 8, 2023 4:12PM - 4:48PM |
Q03.00007: Towards Subcritical Phase Transitions in Liquid Crystalline Elastomers Invited Speaker: Timothy White Liquid crystalline elastomers (LCEs) are functional materials widely studied for their ability to produce large deformations. This deformation is a result of order disruption between mesogenic moieties incorporated in the polymer network. Often, reports detail that LCEs undergo phase transitions analogous to low molar mass liquid crystalline systems. However, in practice, LCEs deviate from this behavior. Prior investigation has associated the deviation from first order behavior in LCEs to the restraint on the mesogens that is imposed by crosslinks. This talk will highlight some of our recent efforts in working toward achieving first order, subcritical phase transitions in LCEs. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q03.00008: Programming Shape Transformations of Gel-based Micro-helices Xinpei Wu, Matthew Libera Nature provides abundant examples of helical structures over many length scales, which have inspired scientists and engineers for centuries. In particular, hydrogel-based helices are of great interest due to their similarity to biological tissue and because of their stimuli-responsive behaviors. The underlying principles of helix formation have been studied in such areas as soft devices, biosensors, and biomimetic materials. However, the precise control of helical shape and chirality in the micrometer regime can be challenging, particularly using a simple one-step maskless process. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q03.00009: 3D simulation of self-growing polymer gels Santidan Biswas, Victor V Yashin, Anna C Balazs We utilize the gel lattice-spring approach to develop the 3D computational model of self-growing polymer gels. When placed in a monomer solution, these gels exhibit sustained growth by imbibing monomeric units from the surrounding solution into their network. We model the two types of self-growing polymer gels, one comprising of an interpenetrating network (IPN) between primary and secondary polymer chains, and the other one consisting of a random copolymer network (RCN), with the copolymers formed by inter-chain exchange between the primary chains and the polymer chains resulting from polymerization of the secondary units. The mathematical model takes into account the effects of gel elasticity and kinetics parameters of the step-growth polymerization. We tune the mechanical properties of these gels by patterning when different gel areas undergo different gel growth kinetics. These gels can be used as building blocks for materials having tunable properties such as controllable gradient, actuators, and shape-morphing materials. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q03.00010: Janus Magnetoelastic Membrane Swimmers Yao Xiong, Hang Yuan, Monica Olvera De La Cruz Soft swimming microrobots have attracted considerable attentions due to their potentials in diverse fields from microswitches to biomedicines and cargo transports. The locomotion control is of importance to the research of micromachines and microrobots. Herein, inspired by the motility strategies of living microorganisms, such as flagella, cilia, and euglenoid, we focus on the design and propulsion mechanisms of Janus magnetoelastic membrane swimmers. Superparamagnetic particles are uniformly distributed on the surface of hemispheres. We study the reversible morphological transitions of closed Janus magnetoelastic shells in response to varying magnetic dipole-dipole interactions. Due to the competition between the magnetic field induced dipoles with the elasticity of the membranes, we observe cyclic non-reciprocal buckled shapes that are accompanied with locomotion. Interestingly, our results show that the characteristics of the propulsion motions is significantly dependent on the temporal patterns of the magnetic dipole-dipole interactions as well as the variations in the elasticity of the hemispheres. |
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