Enzymatic Degradation of Precipitates and the Processing of Coacervate Droplets of Cellulose-Derived Materials to Study Phase Transitions

We investigated the use of cellulose-derived materials as a base to study the transition from solid precipitates to liquid coacervate droplets and from coacervates into solid fibers. We used carboxymethyl cellulose (CMC) with poly(diallyldimethylammonium chloride) (PDADMAC) as our model system to first explore the use of enzymes in weakening the interactions between oppositely charged polymers, thereby facilitating the transition from precipitates to liquid coacervate droplets. We formed solid precipitates when the CMC had a degree of substitution (DS) of 0.6. Starting from precipitates, we added varying concentrations of cellulase to degrade the CMC and monitored the transition of the precipitates to liquid droplets using brightfield microscopy. We used rheology to further assess the material properties of these complexes as the CMC degrades over time. Our data confirm the transition of these materials from solid to a more liquid-like state. With a shorter PDADMAC (N = 53) and a CMC DS of 1.2, we formed coacervates. To create solid materials, we used solution blow spinning with the coacervate phase to form fiber mats. We investigated several parameters, including the distance between the nozzle and substrate, air pressure, syringe pump speed, and concentration of a third sequestered species, to elucidate how these materials transition from a liquid state to solid fibers. These results broaden our understanding of how we may transition materials from one phase to another using the same monomer species.