Type and distribution of chemical groups from controlled photo-oxidation of gyroid nanoporous 1,2-polybutadiene

Photo-oxidation of nanoporous polymers is little studied. The high UV penetration depth and high surface concentration in these materials give unprecedented possibilities both in fundamental work on surface photochemistry and in nanotechnological applications related for example to patterned hydrophilicity or refractive index. This is a quantitative study of the photo-oxidation products of nanoporous gyroid 1,2-polybutadiene in air. Irradiation of the porous sample with UV in the wavelength range of 300-400 nm enables tuning of the hydrophilicity of the nanoporous polymer through formation of hydrophilic chemical groups, carboxyl and hydroxyls, mainly onto the large air-polymer interface. The nature and abundance of the chemical groups induced by photo-oxidation is identified by solid-state 13C-NMR and FTIR spectroscopy. The distribution of photo-oxidation groups, both relative to the nanometre-scale polymer-air interface, and as a function of irradiation depth in the sample, is studied by gravimetry, titrimetry, ATR-FTIR and energy dispersive X-ray spectroscopy in scanning electron microscopy.