he tunable wettability of plasma copolymer coating is the primary concern in this study. The wettability of C₄F₈‐co‐AA plasma polymer coatings can be controlled from superhydrophobicity to superhydrophilicity by tuning surface chemistry and surface morphology. The hydrophilic carboxylic acid group controls the wetting state and hydrophobic fluorocarbon group dewtting state as the presence of polar carboxylic acid group allow polar water to penetrate into plasma copolymer coatings and the presence of nonpolar groups like CF₂ and CF₃ of low surface energy repel water. C₄F₈plasma polymer coating on LDPE surface shows static water contact angle (SWCA) of 119°. As carboxylic acid group concentration increases, SWCA of C₄F₈‐co‐AA plasma polymer coatings decreases. For C₄F₈‐co‐AA (40:5) plasma polymer coatings SWCA decrease to 97°. The advancing contact angle (ACA) and the receding contact angle (RCA) also drop from 123 to 103° and 113 to 93° as presented in Figure a. Optical SWCA images of a water droplet of C₄F₈‐co‐AA plasma polymer on flat LDPE presented in Figure b. With further increase of carboxylic acid groups, more rapid decrees in RWCA as compared to AWCA is observed because RWCA is most sensitive to the polar character. It leads to increase in contact angle hysteresis that indicated an increase in relative adhesion. C₄F₈‐co‐AA (40:40) plasma polymer coatings show rapid decrees in AWCA leading to lower hysteresis as water spread on the hydrophilic surface due to increasing polar interaction between water and carboxylic acid groups. These results suggest that as AA feed ratio increases carboxylic acid group content compared to CF_x also increases and this leads to lower SWCA.

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