Surface modification of polyvinyl alcohol-chitosan blend hydrogels using RF plasma treatment
Hydrogels are made from either natural or synthetic polymeric 3D chain networks with the ability to retain water due to their hydrophilic functional groups. Polyvinyl alcohol (PVA) and chitosan (Cs) are used in this study to synthesize hydrogels without the use of crosslinking agent. The surface properties of PVA-Cs blend were tailored using a 13.56 MHz radio frequency (RF) plasma system with varying working gases, argon (Ar) and oxygen (O2) and exposure times (1 min and 3 min). Contact angle (CA) measurements, with water and glycerine as test liquids, revealed that samples became more hydrophilic when exposed to Ar for 3 min with CA values of 36.97° and 49.8°, respectively. On the other hand, the total surface free energy (SFE) of the 3 min O2-treated hydrogel was the highest among the synthesized hydrogel with a value of 131.4 mN/m. Wetting of PVA-Cs hydrogels were also derived using the SFE values. Calculations showed that plasma treatment enhances the wettability of the hydrogels with polar liquids such as water and blood. Longer exposure time also showed better wettability. Degree of swelling of the hydrogels showed that samples exposed to Ar are unable to absorb and retain water. Nevertheless, plasma treatment was seen as an eective method to tune the surface properties of hydrogels for biomedical applications.