Smart coatings based on poly(styrene-spiropyran) photo-responsive polymers

In this research, poly(styrene-spiropyran) photo-responsive polymers were synthesized by free radical polymerization. For this purpose, an acrylate group was substituted on the spiropyran to allow the polymerization by the vinyl group. Different analyses such as nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), UV-vis spectroscopy, and water contact angle analysis were used to characterize and evaluate the properties of the synthesized polymers. The results of NMR and FTIR analyses indicated the successful copolymerization of styrene and spiropyran. The optical properties of the polymers were evaluated in a chloroform solvent. The color of all solutions was changed to purple by UVA irradiation, which subsequently was eliminated by visible light with a wavelength of 590 nm. Contact angle analysis showed that with increasing spiropyran content, the contact angle of coatings increased and the surfaces were more hydrophobic. UV irradiation made the surface hydrophilic. The water contact angle changes during UV irradiation increased with increasing the spiropyran content of the coatings. As a result, the hydrophobic surface became a hydrophilic one. Therefore, photo-responsive coatings were developed using poly(styrene-spiropyran) polymers.