Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

Formation of rough, dendritic deposits is a critical problem in metal electrodeposition processes and could occur in next-generation, rechargeable batteries that use metallic electrodes. Electroconvection, which originates from the coupling of the imposed electric field and a charged fluid near an electrode surface, is believed to be responsible for dendrite growth. However, few studies are performed at the scale of fidelity where root causes and effective strategies for controlling electroconvection and dendrite growth can be investigated in tandem. Using microfluidics, we showed that forced convection across the electrode surface (cross-flow) during electrodeposition reduced metal dendrite growth (97.7 to 99.4%) and delayed the onset of electroconvective instabilities. Our results highlighted the roles of forced convection in reducing dendrite growth and electroconvective instabilities and provided a route toward effective strategies for managing the consequences of instability in electrokinetics-based processes where electromigration dominates ion diffusion near electrodes.

Well-dispersed, solvent-free silica nanoparticles tethered with polymers exhibit soft glassy rheology and jamming behavior because of the cages induced by interpenetrated chains. In this study, we use small-angle X-ray scattering and rheology to investigate slow structural and mechanical evolution of a soft glassy material composed of silica nanoparticles densely grafted with poly(ethylene glycol) methyl ether (mPEG) chains. We observe a significant equilibration process that has not been reported previously and show that the process is thermally activated and associated with local rearrangements of tethered chains to their equilibrium conformations. At a fixed temperature, the strength of the equilibrated cages increases significantly, relative to their unequilibrated values, but decreases in a predictable manner as the temperature rises. A simple geometrical model is used to rationalize these observations in terms of corona interpenetration, cage dynamics, and yielding of self-suspended nanoparticles.

The propensity of lithium to form nonplanar, mossy, or dendritic electrodeposits at current densities below the diffusion limit is a well-known, fundamental barrier to commercialization of energy-dense storage in lithium metal batteries. It has been proposed that proliferation of Li dendrites can be eliminated by controlling the uniformity and size of the deposits to levels where surface tension and other small-scale interfacial forces are able to planarize the deposition. Herein, we investigate lithium electrodeposition in uniformly porous, nanostructured media formed in cross-linked poly(ethylene oxide) polymer networks enabled by thiol-ene click chemistry. Using galvanostatic strip-plate experiments along with scanning electron microscopy and operando visualization techniques, we critically assess the effectiveness of these materials in enabling uniform, planar deposition of lithium. We report that thiol-ene click networks that host a liquid electrolyte in their pores are more effective than their liquid electrolyte or solid polymer network components in regulating Li deposition at both the nucleation and growth phases. It is shown further that compressive interfacial stresses imparted by the networks during electrodeposition may serve to augment surface tension to enable uniform Li electrodeposition. The practical relevance of these electrolytes is demonstrated in full-cell battery configurations with excellent long-term stability.