Synthesis, photodegradable and antibacterial properties of polystyrene-cinnamaldehyde copolymer film

Copolymerization of styrene (St) and different ratios of Cinnamaldehyde (Cin) from cinnamon oil and synthetic cinnamaldehyde were carried out by free radical polymerization, and were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC) analysis, and Gel Permeation Chromatography (GPC). Photodegradation of cinnamaldehyde incorporated copolymer (Poly (St-co-Cin)) films have been studied at outdoor weathering and under direct ultraviolet (UV) radiation. The extent of photodegradation was assessed by FTIR spectroscopy, percentage weight loss, surface analysis, average molecular weights and polydispersity indices. FTIR analysis confirms the photodegradable mechanisms of the copolymer films as Norrish Type I, Norrish Type II and photo-oxidation. Extreme weight loss was observed at outdoor weathering with 36.76% weight loss for 75% (w/w) cinnamaldehyde (natural-from cinnamon oil) incorporated copolymer (Poly(St-co-N-Cin)), and 45.58% weight loss for 75% (w/w) cinnamaldehyde (synthetic) incorporated copolymer (Poly(St-co-S-Cin)) with respect to 2.5% weight loss for polystyrene (PS) homopolymer for the period of 100 days. The average molecular weights of Poly(St-co-Cin) copolymers after outdoor weathering have drastically reduced compared to polystyrene. Scanning Electron Microscope (SEM) images clearly depict the fracture generation on Poly(St-co-Cin) films upon degradation. Embrittlement and color developments of the copolymer films with aging were noticeably evident. Furthermore, copolymers were tested positive for antibacterial activity against both gram negative and gram positive bacteria.