Temen off and Mikos, p. 274, Problem 7.8 One potential problem associated with t

Question

Temen off and Mikos, p. 274, Problem 7.8 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 an 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].)

Explanation / Answer

The oxygenated carbon functionalities (C-O and O-C=O) are more susceptible to degradation under plasma treatment at high powers than the hydrocarbon portion of the molecule (C-Hx). This is shown by the disappearance of the C-O and O-C=O peaks at higher powers in Figure 2. The O-C=O peak is gone after line (d), so anything above 20 W would cause considerable degradation of this portion of the molecule.

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