A Novel Sequential Photoinduced Living Graft Polymerization

A novel sequential ultraviolet (UV)-induced living graft polymerization method has been designed and investigated to modify polymeric materials. This method consists of two steps. In the first step, a surface initiator is formed on a substrate under UV irradiation in the presence of benzophenone (BP) solutions; in the second step, the monomers are grafted to the substrate by a living polymerization initiated by the surface photoinitiator. Hydrophobic porous polypropylene (PP) membranes were made hydrophilic and with negatively charged surface by grafting acrylic acid (AA). Experimental results demonstrated that grafting density and graft polymer chain length can be controlled by choosing the reaction conditions in the first step and in the subsequent step(s) independently. The amount of grafted polymer relative to the total amount of polymer from the novel sequential photoinduced graft polymerization method is 4-fold greater than that of the simultaneous grafting method for the system studied. In addition, a reaction mechanism was proposed and confirmed in the experiments. With regard to the surface initiator formation caused by hydrogen abstraction, the kinetic studies show that the reaction rate has a maximum value which depends on BP concentration. With regard to the graft polymerization in the second step, there is a linear relationship between the graft polymerization rate and the monomer concentration.