Network Topology and Percolation in Model Covalent Adaptable Networks.

Incorporating dynamic covalent linkages into thermosets can endow previously unrecyclable materials with new functionality and reprocessing options. Recent work has shown that the properties of the resulting covalent adaptable networks (CANs) are highly dependent on network topology, specifically the phenomenon of percolation, when permanent linkages form a connected skeleton that spans the material. Here, we use a model glassy disulfide based CAN to assess the merits of mean-field percolation theory as a tool to describe the network topology of CANs.

Using the Quartz Crystal Microbalance to Monitor the Curing of Drying Oils.

Drying oils such as linseed oil form a polymer network through a complex free-radical polymerization process. We have studied polymerization in this challenging class of polymers using a quartz crystal microbalance (QCM). The QCM is able to measure the evolution of polymer mass and mechanical properties as the oil transitions from a liquid-like to a solid-like state.

Tailoring Interactions of Random Copolymer Polyelectrolyte Complexes to Remove Nanoplastic Contaminants from Water.

We investigate the usage of polyelectrolyte complex materials for water remediation purposes, specifically their ability to remove nanoplastics from water, on which there is currently little to no prior research. We demonstrate that oppositely charged random copolymers are effective at quantitatively removing nanoplastic contamination from aqueous solution. The mechanisms underlying this remediation ability are explored through computational simulations, with corroborating quartz crystal microbalance adsorption experiments.

Crack Surface Analysis of Elastomers Using Transfer Learning.

Cracks that form during fatigue offer critical information regarding the fracture process of the associated material, such as the crack speed, energy dissipation, and material stiffness. Characterization of the surfaces formed after these cracks have propagated through the material can provide important information complementary to other in-depth analyses. However, because of the complex nature of these cracks, their characterization is difficult, and most of the established characterization techniques are inadequate.

Sterilizable and Reusable UV-Resistant Graphene-Polyurethane Elastomer Composites.

Shortages of personal protective equipment (PPE) at the start of the COVID-19 pandemic caused medical workers to reuse medical supplies such as N95 masks. While ultraviolet germicidal irradiation (UVGI) is commonly used for sterilization, UVGI can also damage the elastomeric components of N95 masks, preventing effective fit and thus weakening filtration efficacy. Although PPE shortage is no longer an acute issue, the development of sterilizable and reusable UV-resistant elastomers remains of high interest from a long-term sustainability and health perspective.

Quantitative high-throughput measurement of bulk mechanical properties using commonly available equipment.

Machine learning approaches have introduced an urgent need for large datasets of materials properties. However, for mechanical properties, current high-throughput measurement methods typically require complex robotic instrumentation, with enormous capital costs that are inaccessible to most experimentalists. A quantitative high-throughput method using only common lab equipment and consumables with simple fabrication steps is long desired.

In vitro assessment of varying peptide surface density on the suppression of angiogenesis by micelles displaying αvβ3 blocking peptides.

Ligand targeted therapy (LTT) is a precision medicine strategy that can selectively target diseased cells while minimizing off-target effects on healthy cells. Integrin-targeted LTT has been developed recently for angiogenesis-related diseases. However, the clinical success is based on the optimal design of the nanoparticles for inducing receptor clustering within the cell membrane.

Processing Polyelectrolyte Complexes with Deep Eutectic Solvents.

Polyelectrolyte complexes (PECs) formed from mixtures of polycations and polyanions are useful in a variety of applications and can be processed by the addition of salt. Salt mediates the ionic interactions within the polyelectrolyte complexes, with appropriately chosen salts enabling complete dissolution of solid PEC in aqueous media. Substantial complications arise from the crystallization of the salt during subsequent processing steps.

High-Throughput Screening Test for Adhesion in Soft Materials Using Centrifugation.

High-throughput screening of mechanical properties can transform materials science research by both aiding in materials discovery and developing predictive models. However, only a few such assays have been reported, requiring custom or expensive equipment, while the mounting demand for enormous data sets of materials properties for predictive models is unfulfilled by the current characterization throughput. We address this problem by developing a high-throughput colorimetric adhesion screening method using a common laboratory centrifuge, multiwell plates, and microparticles.

Exploring the effect of humidity on thermoplastic starch films using the quartz crystal microbalance.

The quartz crystal microbalance (QCM) is used as a non-destructive and efficient characterization tool for thin thermoplastic starch (TPS) films. Thin TPS films (1-2 μm) were prepared with 30% (w/w starch) plasticizers using either glycerol or an ionic liquid, 1-ethyl-3-methylimidiazolium acetate ([emim][Ac]), as the plasticizer. The differences in the mechanical properties and environmental effects on the plasticized TPS films were explored.

Tough, Transparent, Photocurable Hybrid Elastomers.

We investigated polydimethylsiloxane/poly(methyl methacrylate) (PDMS/PMMA) interpenetrating polymer networks (IPNs) by both sequential and simultaneous syntheses. In the sequential IPN, the PDMS network was first thermally cured after which methyl methacrylate was swelled in and UV photopolymerized in situ. The simultaneous IPN consists of a one-pot, single-step UV cure of both components.

High-Fidelity Hydrogel Thin Films Processed from Deep Eutectic Solvents.

Polyampholyte (PA) hydrogels are a fascinating class of soft materials that can exhibit high toughness while retaining self-healing characteristics. This behavior results from the random distribution of oppositely charged monomers along the polymer chains that form transient bonds with a range of bond strengths. PAs can be dissolved in aqueous salt solutions and then recast via immersion precipitation, making them particularly useful as surface coatings in biomedical applications.

Control over electroless plating of silver on silica nanoparticles with sodium citrate.

We describe the use of citrate to control the electroless plating of silver metal on silica nanoparticles. We find that the incorporation of relatively small amounts of citrate during the reduction of the Tollens' reagent in the presence of sensitized silica nanoparticles induces a continuous transition from conformal to raspberry particle coatings. This transition is dependent on both the citrate concentration and the silver precursor concentration.

Investigations of the high-frequency dynamic properties of polymeric systems with quartz crystal resonators.

Opportunities arising from the use of the rheometric quartz crystal microbalance (RheoQCM) as a fixed frequency rheometer operating at 15 MHz are discussed. The technique requires the use of films in a specified thickness range that depends on the mechanical properties of the material of interest. A regime map quantifying the appropriate thicknesses is developed, based on the properties of a highly crosslinked epoxy sample that is representative of a broad class of polymeric materials.

High Density Display of an Anti-Angiogenic Peptide on Micelle Surfaces Enhances Their Inhibition of αvβ3 Integrin-Mediated Neovascularization In Vitro.

Diabetic retinopathy (DR), Retinopathy of Pre-maturity (ROP), and Age-related Macular Degeneration (AMD) are multifactorial manifestations associated with abnormal growth of blood vessels in the retina. These three diseases account for 5% of the total blindness and vision impairment in the US alone. The current treatment options involve heavily invasive techniques such as frequent intravitreal administration of anti-VEGF (vascular endothelial growth factor) antibodies, which pose serious risks of endophthalmitis, retinal detachment and a multitude of adverse effects stemming from the diverse physiological processes that involve VEGF.

Sample Preparation in Quartz Crystal Microbalance Measurements of Protein Adsorption and Polymer Mechanics.

In this study, we present various examples of how thin film preparation for quartz crystal microbalance experiments informs the appropriate modeling of the data and determines which properties of the film can be quantified. The quartz crystal microbalance offers a uniquely sensitive platform for measuring fine changes in mass and/or mechanical properties of an applied film by observing the changes in mechanical resonance of a quartz crystal oscillating at high frequency. The advantages of this approach include its experimental versatility, ability to study changes in properties over a wide range of experimental time lengths, and the use of small sample sizes.

Self-Assembly of Charge-Containing Copolymers at the Liquid-Liquid Interface.

Quantitatively understanding the self-assembly of amphiphilic macromolecules at liquid-liquid interfaces is a fundamental scientific concern due to its relevance to a broad range of applications including bottom-up nanopatterning, protein encapsulation, oil recovery, drug delivery, and other technologies. Elucidating the mechanisms that drive assembly of amphiphilic macromolecules at liquid-liquid interfaces is challenging due to the combination of hydrophobic, hydrophilic, and Coulomb interactions, which require consideration of the dielectric mismatch, solvation effects, ionic correlations, and entropic factors. Here we investigate the self-assembly of a model block copolymer with various charge fractions at the chloroform-water interface.

Guanidinium Can Break and Form Strongly Associating Ion Complexes.

Guanidinium is one of nature's strongest denaturants and is also a motif that appears in several interfacial contexts such as the RGD sequence involved in cell adhesion, cell penetrating peptides, and antimicrobial molecules. It is important to quantify the origin of guanidinium's ion-specific interactions so that its unique behavior may be exploited in synthetic applications. The present work demonstrates that guanidinium ions can both break and form strongly associating ion complexes in a context-dependent way.

Sustained micellar delivery via inducible transitions in nanostructure morphology.

Nanocarrier administration has primarily been restricted to intermittent bolus injections with limited available options for sustained delivery in vivo. Here, we demonstrate that cylinder-to-sphere transitions of self-assembled filomicelle (FM) scaffolds can be employed for sustained delivery of monodisperse micellar nanocarriers with improved bioresorptive capacity and modularity for customization. Modular assembly of FMs from diverse block copolymer (BCP) chemistries allows in situ gelation into hydrogel scaffolds following subcutaneous injection into mice.

Energy Renormalization Method for the Coarse-Graining of Polymer Viscoelasticity.

Developing temperature transferable coarse-grained (CG) models is essential for the computational prediction of polymeric glass-forming (GF) material behavior, but their dynamics are often greatly altered from those of all-atom (AA) models mainly because of the reduced fluid configurational entropy under coarse-graining. To address this issue, we have recently introduced an energy renormalization (ER) strategy that corrects the activation free energy of the CG polymer model by renormalizing the cohesive interaction strength as a function of temperature T, i.e.

Solubility and interfacial segregation of salts in ternary polyelectrolyte blends.

Solid Polymer Electrolytes (SPEs) consisting of ternary blends of charged polymer, neutral polymer, and plasticizer or salt have received much interest for their low volatility and high flexibility of polymers with ion-selective conductivity of the charge-carrying backbone. It has been shown that in these polyelectrolyte blends, where the dielectric constant is relatively low, ionic correlations can significantly influence the miscibility, inducing phase separation even at negative values of χN. Here we present a comprehensive study of phase behavior and interfacial segregation upon the addition of a tertiary component in blends of charged and neutral homopolymers.