One potential problem associated with the long-term release of a drug from an implanted material ...

One potential problem associated with the long-term release of a drug from an
  implanted material is the initial burst release of significant amounts of the drug. One
  approach to reduce this burst release is to apply a coating to the material in an attempt to
  modulate the diffusion of the drug. In a study performed by Kwok et al. 24 the
  effectiveness of butyl methacrylate as a coating material was tested. Figure 1 below shows
  the chemical structure and a ESCA scan of the surface of this coating material. Plasma
  treatment of its surface was also performed in an attempt to increase its hydrophilicity. Part
  of the study explored how the power of the plasma-generating equipment affects the surface
  chemistry (Fig. 2 below). At high power, some of the polymer begins to degrade. Which of
  the bonds in the polymer is subject to degradation at high power? Explain in terms of the
  results in Fig. 2. Which power setting would you recommend for surface treating this
  polymer and why? (Figures adapted with permission from 24.)