UV Photoinitiated Temperature-Sensitive Modification of Polypropylene Grafted with Poly(N-isopropylacrylamide)

Abstract Poly( N -isopropylacrylamide) was grafted onto the surface of polypropylene by a two-step surface photo-grafting method using benzophenone as a photosensitizer to impart surface temperature sensitivity to polypropylene. The structure of graft-copolymer was characterized by infrared spectroscopy and scanning electron microscopy. Its temperature sensitivity was investigated by modulated differential scanning calorimetry and surface water contact angle determination. The effects of initiator concentration, photoreduction time, monomer concentration and light exposure time on grafting rate are discussed. The results showed that graft-copolymer is temperature-sensitive hydrophilic/hydrophobic, and its low critical solubility temperature is around 33°C. The grafting rate could be increased by increasing the initiator concentration, monomer concentration, extending the photoreduction time and irradiation time; and the grafting rate could be controlled by adjusting these four factors.