Effect of patterns on Polyacrylamide hydrogel surface towards enhancement of water retention

Polyacrylamide hydrogel was investigated to improve its water retention capacity. Among the several hydrogel samples prepared, a sample with ∼0.55 % cross-linker was found sufficiently rigid with high water content. The drying and rehydration cycles induced the appearance and disappearance of cracks respectively within the hydrogel and were confirmed by FESEM analysis. The effect of mili-patterns on hydrogel surface was studied and was found that the patterns enhanced the duration of water retention by ∼60 %. Even after 100 h of drying of a swelled hydrogel, the one with the pattern retained sufficient water so that its length remained ∼35 % longer compared to a non-patterned flat hydrogel. These findings were discussed in light of the Kelvin equation and were supported by the time-resolved Raman spectra that ensured the presence of the bound water for a longer duration. Based on the intensity of O–H stretching, it was inferred that patterned hydrogel exhibited water retention efficiency (RE) of ∼97 %, whereas, a flat non-patterned hydrogel had RE merely of ∼70 % after 3 cycles of drying and rehydration.