Electron-beam induced RAFT-graft polymerization of poly(acrylic acid) onto PVDF

This paper explores for the first time the post-radiation-induced-graft polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced graft polymerization onto polymers is a potentially interesting technique to create easily new materials from highly resistant polymers, e.g. surface graft polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) improves its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to control molecular weight of grafted chains, and therefore design and standardize the properties of the final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. The ability of the RAFT agents to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation-induced-graft polymerization technique. In this way, graft polymerization of AA onto electron-beam irradiated alpha-PVDF was performed using trithiocarbonic acid bis(1-phenylethyl) ester as a RAFT agent to control the radical polymerization. We studied several grafting parameters such as solvent, monomer concentration and grafting time in order to achieve a poly(acrylic acid) (PAA) layer onto PVDF surface. Acetic acid was found to be the best solvent for many reasons, as to drive graft polymerization mainly to the polymer surface, complete solubility and stability of all reactants. Hydrolysis of PAA chains was also studied in order to remove the trithiocarbonate functionality from the grafted polymer. A mild chemical condition was achieved in order to have thiol groups that were detected onto the modified PVDF by specific enzymatic reaction. (c) 2005 Elsevier B.V. All rights reserved.