Fig. 3: MD simulations of PAA hydrogel formation and diffusive dynamics on untreated glass and silicone chain-grafted glass.

a Representative snapshots of hydrogel-formation simulations at 1 µs. The bottom views show the bottom surfaces (white dashed line) of the poly(acrylic acid) (PAA) hydrogel with the mold removed for clarity. The lower panels are magnified snapshots showing details of the interactions between PAA and molds. b Density of interfacial hydrogen bonds formed between the PAA hydrogel and molds. c Proportion of the mold surface area in contact with the PAA hydrogel surface network. d Proportion of polar contents (carboxylate oxygen) in the surface network of PAA hydrogels contacting the different mold surfaces. e Mean squared displacement (MSD) of a single PAA chain diffusing on the silicone chain-grafted mold surface with 0%/50%/100% silicone chains restrained. Diffusion coefficients of PAA were obtained from fitting of the MSD data. f Trace of the C75 atom of PAA in the four 1-µs surface-diffusion simulation replicas. g Schematic snapshots of the adhesion-diffusion simulations for a single PAA chain on the silicone chain-grafted molds with 0%/50%/100% silicone chains restrained. The terminal carbon of PAA at its free end, C75, is restrained by a cylindrical wall potential. The adhesion time, τ, is defined as the minimum time required for the complete adhesion of PAA. h Adhesion probability of PAA calculated from 100 runs of 20-ns adhesion-diffusion simulations. Mean adhesion time of PAA (〈τ〉) ± the standard error of the mean, is given in the inserted table; P < 0.0001 (between the 0% and 50% data group); P = 0.080 (between the 50% and 100% data group); P < 0.0001 (between the 0% and 100% data group). Statistical analyses were performed by using two-tailed Student’s t test. P values less than 0.05 were considered statistically significant differences among the compared groups.