Probing Polymer Solution Conformation along Microparticle Formation Pathways with SANS

Polymeric microparticles are ubiquitous in encapsulation and targeted release applications. Their function is predicated on their microstructure, shape and interactions, which determine stability, phase behaviour and release profiles. Polymer solution droplet extraction is an attractive route to control their formation, and understanding the thermodynamic and non-equilibrium pathways involved is crucial for their predictive design. Here, we show microfluidic droplet formation and selective solvent exchange to yield porous polymer microparticles [1] with tunable morphologies [2]. We systematically explore the process with model poly(vinyl alcohol), varying polymer functionality, size, concentration, and droplet size [3]. We map polymer solution conformation with small angle neutron scattering (SANS) and microfluidic-SANS to resolve how chain dimensions evolve with mixed solvent/non-solvents during solidification. Our study elucidates, for the first time, the spatio-temporal evolution of polymer solutions into particles, from molecular to micron scales.

[1] Cabral and co-workers, Langmuir 30, 2470-2479 (2014).
[2] Udoh et al., Langmuir 32, 8131-8140 (2016), Science Advances 3, eaao3353 (2017).
[3] Sharratt et al., Soft Matter 14, 4453-4463 (2018).