Polyelectrolyte Coacervates: From Stabilized Protocell Motion to Drug Polymorph Control
By: Alamgir Karim
From: Department of Chemical and Biomolecular Engineering, University of Houston
At: Building C1, room 1.4.14
[2026-06-29]
Complex coacervates are a dense, polymer-rich phase formed during liquid-liquid phase separation (LLPS) of oppositely charged polymers that coexist with surrounding dilute phase ‘Supernatant’. Coacervates act as ion reservoir, selectively concentrating ions and molecules, thereby creating a confined microenvironment that promote nucleation and guide non classical crystallization by stabilizing prenucleation clusters and amorphous intermediates. We demonstrate that coacervate droplets can be stabilized in de-ionized water and can mimic membraneless pre-biotic protocells. They also act similarly to highly polarizable living cells, and move under relatively weak electric fields, with precise control over their deformation into assembled droplets and organized chains. We also demonstrate that coacervates formed by poly (diallyl dimethylammonium) (PDDA) and Sodium poly(acrylate) (PA) act as ion-concentrating microenvironment, sequestering calcium (Ca2+) and oxalate (C2O42-) ions within the dense phase that are precursors of kidney stones. Theses ion-polymer interactions regulate the local supersaturation, enabling controlled, time-dependent crystal growth. As a result, the system directs polymorph selection, preferentially stabilizing calcium oxalate monohydrate (COM) or calcium oxalate dihydrate (COD) crystals formation in contrast to bulk solution, where rapid and uncontrolled crystal growth occurs. Our results showed that crystallization of calcium oxalate in coacervate is significantly influenced by parameters such as polymer concentrations, polymer ratios, and pH. Moreover, different coacervate systems influence calcium oxalate polymorphism, as variation in ion-polymer interactions steer nucleation toward specific polymorphic form. These findings highlight the potential of complex coacervates as versatile, biomimetic platforms for controlling mineralization processes with implications in both biological systems and designing new materials.