We acknowledge the support of: Perry Group, Dubin Group, Charge Density Rules For Nature-Inspired Materials Hansen Tjo, Sarah L. Perry Department of Chemical Engineering, University of Massachusetts Amherst Polycation (+) Polyanion (-) • Surfactant amphilicity -> flexible environments, e.g., hydrophobic drug encapsulation for release in polar physiological system • Charged micelle isotropy ~ ideal colloidal systems How does molecular chemistry inform coacervate phase behavior? Comple x Coacervation 100μm 100μm 100μm Surfactant Steric Repulsion Effects On Phase Behavior 100μm 100μm Y(-) ~ 0.6 Precipitation Predominates Y(-) ~ 0.8 100μm Spherical Droplets (Coacervates) Y(-) ~ 0.3 100μm L-to-S Phase Transition 100μm Y(-) ~ 0.6 • Increase in Polymer Charge Density Decreases Critical Micelle Surface Charge Density • Increase in neutral surfactant head PEG length effectively decreases micelle surface charge density Taylor et al., Soft Matter, 2016, 12, 9142. Applications: • Drug delivery • Vaccines stabilizers • Sustainable oil recovery Electrostatically driven, associative liquid-liquid phase separation (LLPS) • Charge density studies inform molecular design of polymer-micelle slug injections • High-throughput optimization of slug parameters using porous microfluidic media • Bridging systems chemistry and microfluidic platforms for energy sustainability Adapted from He et al., ACS Crystal Growth & Design, 2020, 20, 1021. PDADMAC-SDS/TX-100 Phase Diagram Surfactant Steric Hindrance Polymer Charge Density Design Rules = No Phase Separation Increasing Micelle Surface Charge Density Surfactant amphilicity forms adsorbed film lowering oil/slug interfacial tension Microfluidic Gradient-Tree Approach Increasing surfactant PEG-length increases (−) of turbidity jump scales with increasing micelle steric repulsion Negative correlation between polymer charge density and • Determined the effects of polymer and micelle charge densities in driving complex coacervation • Charge density design framework can be generalized to broad classes of ionic colloids, e.g., charged proteins, nanoparticles etc. and broaden array of coacervate-based platforms • Further exploration into nanoscale chemistry affects on coacervate mechanical properties for renewable energy applications Polyethylene Glycol (PEG) tail on neutral surfactant head = Well-plate assays for turbidity, optical microscopy, kinetics studies