We acknowledge the support of: Perry Group, Dubin Group,

Charge Density Rules For Nature-Inspired MaterialsHansen Tjo, Sarah L. PerryDepartment 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?

ComplexCoacervation

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 Transition100μm

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

Inc

reas

ing

Mic

elle

Su

rface

Ch

arg

e D

en

sity

Surfactant amphilicity forms

adsorbed film lowering oil/slug

interfacial tension

Microfluidic Gradient-Tree Approach

Increasing surfactant PEG-length

increases 𝒀(−) of turbidity jump

𝒀𝒄 scales with increasing micelle

steric repulsion

Negative correlation

between polymer charge density

and 𝒀𝒄

• 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

= 𝒀𝒄

Well-plate assays for turbidity, optical

microscopy, kinetics studies