UV-induced crosslinking of the polybutadiene domains in lamellar polystyrene-block-polybutadiene block copolymer films - An in-depth study

We present an in-depth study of the UV-induced crosslinking of the polybutadiene domains in lamellar polystyrene-block-polybutadiene (PS-b-PB) block copolymer films. The crosslinking process is followed by a combination of depth-sensing indentation, Raman spectroscopy, and differential scanning calorimetry (DSC) investigations. Indentation assesses changes in the mechanical properties of the overall polymer films while Raman experiments directly monitor the consumption of the PB double bonds. Immediately after a short UV exposure, a loose network is formed and the glass transition temperature increases, whereas changes in the mechanical properties of the materials require far longer hardening times. We show that both processes are strongly affected by the amount of crosslinker (Lucirin-TPO®) added (within a range of 5 to 50 wt. % with respect to the PB fraction of the material).