Effect of Acid Dopant on the Antibacterial Properties of k-Carrageenan/Polyaniline Films

Koh, Mei Xin (2024) Effect of Acid Dopant on the Antibacterial Properties of k-Carrageenan/Polyaniline Films. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Traditionally, the polymeric antibacterial film, gloves and also plastic are used to avoid touching the contaminant surface as the bacteria that easily spread everywhere. The usage of them had caused terrible plastic pollution. To solve this problem, the biopolymer which is the k-carrageenan (k-CGN) was used as matrix to form the antibacterial film with the incorporation of the polyaniline (PAni) to act as the antibacterial agent. The PAni was synthesized by chemical oxidative method by using different acid dopants which are hydrochloric acid (HCl), sulphuric acid (H2SO4) and phosphoric acid (H3PO4). The k-CGN/PAni films were produced through ex-situ method. For the characterisation, the chemical structure and oxidation state of PAni and k-CGN/PAni film were confirmed by the FTIR and UV-Vis analyses. Among all the doped PAni, PAni-H2SO4 showed the highest conductivity (29.33 S/cm) and thermal stability (530°C) compared to PAni-HCl and PAni-H3PO4. For the k-CGN/PAni films, they posed a lower conductivity and thermal stability compared to the pristine PAni. Lastly, all the k-CGN/PAni films were successfully inhibited the growth of Staphylococcus aureus (gram-positive) but not work to the Pseudomonas aeruginosa (gram-negative). The mechanism of the films inhibited bacteria was the protonated PAni was attracted to the anionic membrane of the bacteria and disrupted the cell wall as well as destroyed the peptidoglycan. The sequence of the antibacterial performance was k-CGN/PAni-HCl film (PAni% = 10%, inhibition% = 35.82%) > k-CGN/PAni-H2SO4 film (PAni% = 20%, inhibition% = 35.44%) > k-CGN/PAni-H3PO4 film (PAni% = 30%, inhibition% = 37.65%). In short, the k-CGN/PAni-HCl film was the best composite that possesses the highest antibacterial properties as well as good mechanical property by utilising the minimum amount of PAni (10%).