Formation of Nanoporous β-PVDF Membranes and Visualization of Labelled PAA Radiografted Pores by Confocal Laser Scanning Microscopy

Poly (vinylidene fluoride) (PVDF) foils were irradiated with different radiations: electrons and swift heavy ions. In the first case, bulk and surface were homogeneously irradiated whereas for swift heavy ions the energy deposition is mainly localised along the ion pathway. In this study, heavy ion bombardment is used to obtain polymers membranes. The β-PVDF irradiated foils with Kr (10.37 MeV/amu) were chemically etched using an aqueous solution of KOH/KMnO4 at 65degree. The track diameter characterized by Scanning Electron Microscopy (SEM) and Small Angle Neutron Scattering is in the 20-50nm range. These nanoporous β-PVDF track-etched membranes can be grafted with acrylic acid (AA) using the remaining active sites produced previously by the heavy ion beams. Indeed, the concentration of radicals created in foils and track-etched PVDF have been studied by Electron Paramagnetic Resonance (EPR) and results have shown that after 3h etching time, 20% of active sites remains. Grafted and functionalized films were characterized using Infrared Spectroscopy, weighing measurements and Energy Dispersive Spectroscopy (EDS). The grafting yield has been found to be strongly dependent on the monomer concentration and etching time. Lower AA concentrations of 5 vv% leading to very low grafting yield were intensively investigated in order to get a fine PAA coverage onto pore walls. Under these conditions, it is necessary to adopt an enhancement method either Confocal Laser Scanning Microscopy (CLSM) to visualize grafting. CLSM results in well-resolved images and allows for an optical sectioning to get 3D data. Alexa Fluor Hydrazide probes were used to label acrylic acid. Thus, we can study the spatial distribution of acrylic acid in nanopores