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The viscosity and microstructure of Li-ion battery slurries and the performance of the resulting electrodes have been shown to depend on the mixing protocol. This work applies rheology to understand the impact of shear during mixing and polymer molecular weight on slurry microstructure and electrode performance. Mixing protocols of different shear intensity are applied to slurries of LiNi0.33Mn0.33Co0.33O2 (NMC), carbon black (CB), and polyvinyldiene difluoride (PVDF) in N-methyl-2-pyrrolidinone (NMP), using both high-molecular-weight (HMW) and low-molecular-weight (LMW) PVDF. Slurries of both polymers are observed to form colloidal gels under high-shear mixing, even though unfavorable interactions between high molecular weight PVDF and CB should prevent this microstructure from forming. Theoretical analysis and experimental results show that increasing shear rate during the polymer and particle mixing steps causes polymer scission to decrease the polymer molecular weight and allow colloidal gelation. In general, electrodes made from high molecular weight PVDF generally show increased rate capability. However, high shear rates lead to increased cell variability, possibly due to the heterogeneities introduced by polymer scission. 

The microstructure of solid coatings produced by solution processing is highly dependent on the coupling between growth, solute diffusion, and solvent evaporation. Here, a quasi-2D numerical model coupling drying and solidification is used to predict the transient lateral growth of two adjacent nuclei growing toward each other. Lateral gradients of the solute and solvent influence the evolution of film thickness and solid growth rate. The important process parameters and solvent properties are captured by the dimensionless Peclet number (Pe) and the Biot number (Bi), modified by an aspect ratio defined by the film thickness and distance between nuclei. By variation of Pe and Bi, the evaporation dynamics and aspect ratio are shown to largely determine the coating quality. These findings are applied to drying thin films of crystallizing halide perovskites, demonstrating a convenient process map for capturing the relationship between the modified Bi and well defined coating regimes, which may be generalized for any solution processed thin film coating systems. 

Low molecular weight gelators (LMWGs) are the subject of intense research for a range of biomedical and engineering applications. Peptides are a special class of LMWG, which offer infinite sequence possibilities and, therefore, engineered properties. This work examines the propensity of the GxG peptide family, where x denotes a guest residue, to self-assemble into fibril networks via changes in pH and ethanol concentration. These triggers for gelation are motivated by recent work on GHG and GAG, which unexpectedly self-assemble into centimeter long fibril networks with unique rheological properties. The propensity of GxG peptides to self-assemble, and the physical and chemical properties of the self-assembled structures are characterized by microscopy, spectroscopy, rheology, and X-ray diffraction. Interestingly, we show that the number, length, size, and morphology of the crystalline self-assembled aggregates depend significantly on the x-residue chemistry and the solution conditions, i.e. pH, temperature, peptide concentration, etc. The different x-residues allow us to probe the importance of different peptide interactions, e.g. π–π stacking, hydrogen bonding, and hydrophobicity, on the formation of fibrils. We conclude that fibril formation requires π–π stacking interactions in pure water, while hydrogen bonding can form fibrils in the presence of ethanol–water solutions. These results validate and support theoretical arguments on the propensity for self-assembly and leads to a better understanding of the relationship between peptide chemistry and fibril self-assembly. Overall, GxG peptides constitute a unique family of peptides, whose characterization will aid in advancing our understanding of self-assembly driving forces for fibril formation in peptide systems. 

Post-drawn PCL nanofibers can be molecularly tuned to have a variety of mechanical properties and drug release profiles depending on the temperature and time of annealing, which has implications for regenerative medicine and drug delivery applications. Post-drawing polycaprolactone (PCL) nanofibers has previously been demonstrated to drastically increase their mechanical properties. Here the effects of annealing on post-drawn PCL nanofibers are characterized. It is shown that room temperature storage and in vivo temperatures increase crystallinity significantly on the order of weeks, and that high temperature annealing near melt significantly increases crystallinity and molecular orientation on the order of minutes. The kinetics of crystallization were assessed using an anneal and quench approach. High temperature annealing also increased the ultimate tensile strength and toughness of the fibers and changed the release profile of a model drug absorbed in PCL nanofibers from first-order to zero-order kinetics.