Halochromic poly (lactic acid) film for acid base sensor

A novel strategy to engineer biodegradable halochromic film based on poly (lactic acid) (PLA) for pH sensorial substances was presented. The effect of polyethylene glycol (PEG) compositions and dye amount on the efficiency of halochromic pH film was observed. The interactions between PLA, PEG, and dye was evidence by Fourier transform infrared. UV-VIS results indicated the sensitivity of the halochromic film through color changes. Mechanical performance was investigated by tensile testing to assess the potential of the halochromic film. It was found that the halochromic pH film has a clear color response from yellow to purple at pH 3-11 with a rapid response time within a minute. The results also revealed that varying content of PEG showed a significant effect on response time compared with varying dye compositions. PLA/PEG film and dye formed new interactions where PEG increased the free volume of PLA and made it possible for the PEG and the dye to diffuse and entrap between PLA chain. In term of the film strength, the addition of PEG and dye improved the flexibility of PLA film, which enables great potential in many applications such as medical, textile, and packaging.