Electron-beam induced RAFT-graft polymerization

MARIANO GRASSELLI; BETZ, N.

NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B - BEAM INTERACTIONS WITH MATERIALS AND ATOMS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2005 vol. 236 p. 201 - 207

0168-583X

This paper explores for the first time the radiation-induced-grafting polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced grafting polymerization onto polymers is a potentially interesting technique to easily create new materials from highly resistant polymers. For example, surface grafting polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) to improve its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to keep under control and therefore design and standardize the properties of final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. In spite of the controversy of its mechanism, the potentiality to prepare polymers with enhanced properties is evident. The ability of these chain transfer agents (CTA) to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation induced grafting polymerization technique. In this way, grafting polymerization of AA onto electron beam irradiated a-PVDF has been performed using trithiocarbonic acid bis(1-phenylethyl) ester as CTA agent to control the radical polymerization by RAFT mechanism. 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 grafting 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.