Development of chitosan-acrylic acid based hydrogels with incorporated polyaniline and plasma treatment

Hybrid hydrogels are materials that incorporate features from multicomponent systems of polymers, significantly improving their functionality and making them ideal for biomedical applications. Both natural and synthetic polymers are utilized, further enhancing their functionality. The combination of polyaniline (PANI), chitosan (CS), and acrylic acid (AA) can result in a multifunctional hybrid hydrogel that is antibacterial, hydrophilic, and salt-sensitive. A multifunctional PANI-CS-AA with varying PANI weight ratio was synthesized in this study. In addition, improving the surface of the multifunctional hydrogels by atmospheric pressure plasma (APP) treatment was also investigated. During APP treatment, the production of reactive species (e.g., OH and N2 radicals) responsible for the functionalization of the hydrogel surface was confirmed through optical emission spectroscopy. The integration of three polymer components in the synthesized hydrogels was confirmed through the presence of their mid-FTIR spectral characteristics, particularly in the AA and CS C=O, PANI quinonoid and benzenoid units, AA COO−, and the PANI aromatic and C—H vibration regions. Moreover, the hybrid hydrogels with incorporated PANI and APP treatment improved their wettability and surface free energy (SFE) characteristics. The hybrid hydrogels with 0.25 wt. % PANI and exposed to 2 min air plasma yielded the highest hydrophilicity and total SFE with values 41.27° ± 2.15° and 135.68 ± 4.72 mJ/m2, respectively. The plasma-treated 0.25PANI-2.5CS-4AA samples exhibit improved swelling response in water (Smax = 1310 ± 100; ks = 0.005) and saline media (Smax = 1280 ± 80; ks = 0.001) due to enhanced polymeric chains and affinity toward polar liquids. Synthesized hydrogels exhibited antibacterial activity, as evidenced by the zone of inhibition test. Clearing zones measured were in the range of 16–27 mm. The study developed an APP-treated tricomponent hydrogel consisting of PANI, CS, and AA that has improved hydrophilicity, salt sensitivity, and antibacterial features.