Fig. 1: Drying and rehydrating controls the formation of PDADMA/PAA complex coacervates.
a Scheme showing the motivation behind the wet-dry cycle experiment—an early Earth environmental scenario proposed for the emergence of chemical complexity. b Turbidity values for 1:1 PDADMA:PAA complex coacervates prepared at different charge and salt concentrations ([monomer charge] is calculated with respect to the concentration of the polymer repeat units). All samples contained 25 mM HEPES and 4.3 mM MgCl2. The plot on the left is a zoom-in on the low [charge] samples. Black markers represent turbidity below a cutoff of 20, which was chosen based on microscopy images (Supplementary Fig. 8). The width of all circles is proportional to the turbidity values of the overall samples (see legend above, T refers to transmittance). As a guide to the eye, a solid red line delimits the expected boundary between the two-phase and one-phase regions; the line is an approximate binodal curve. The charge concentration refers to one polymer type, not the total amount of both polymers. c Comparison between drying different 1:1 PDADMA:PAA coacervate compositions based on different starting locations on the phase diagram (i = filled triangle, ii = filled square, iii = filled diamond, with the open versions—open triangle, open square, open diamond—and dashed arrows showing the expected approximate 10× dehydration) in the time range of 0–160 min. Drying was performed in a heatblock at 95 °C; (i) shows the volume remaining at each time point (V), which is an average of 27 samples (see Fig. 2) and is applicable to (ii) and (iii) as they have the same drying rate. The dashed arrow in (ii) is expected to go up to 500 mM [NaCl] and 150 mM [polymer charge], and is thus not fully shown. (iv) Rehydration of (i) by adding a volume of water similar to the volume reached at each time point in reverse order of the top panel. All scale bars are 20 µm.
