Design of Smart Surface by Nanometric Grafting of NIPAAm with Benzophenone Initiator under UV Radiation

The UV radiation method is a suitable method for grafting processes . Poly-Nisopropylacrylamide was successfully grafted onto a polystyrene surface with benzophenone initiator under UV radiation. The ATR-FTIR analysis showed the existence of the graft poly-N-isopropylacrylamide (PNIPAAm) on the surface by this method. The scanning electron microscopy and atomic force microscopy (AFM) images clearly showed suitable grafting of the PNIPAAm on the PS surface . Surface topography and graft thickness in AFM images of the grafted samples showed that the thickness of these grafts was about 300-600 nm. The drop water contact angle of the grafted sample at 37°C and 4°C was 48° and 63° respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. Thermo-responsive polymers were grafted to dishes covalently, which allowed epithelial cells to attach and proliferate at 37°C; the cells were also detached spontaneously without using enzymes when the temperature dropped below 4°C. Also MTT analysis showed a good viability of cells on the grafted samples. Such a characteristic proved that this type of grafted material had the potentiality as a biomaterial for cell sheet engineering.