Advanced instrumental techniques: (1) Analysis of spatial chemical phase segregation in biodegradable polymers by STXM and TOF -SIMS (2) Novel effects of cluster vs. monatomic primary ion bombardment of polymers in TOF-SIMS
Wells, David D.
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The primary focus of this thesis is the development of Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Scanning Transmission X-ray Microscopy (STXM) to characterize phase segregation of polymer blends that have potential applications as materials for implantable drug delivery systems. Two model systems were studied consisting of blends of fluorine-endcapped poly(L-lactic acid) and poly(L-lactic acid) and also blends of polylysine and poly(lactic acid). The chemically relevant imaging capabilities of these techniques allowed for evaluation of phase-segregated domains while spectral changes provided insight into interactions between the two components. Analysis of the blended polymer film surface after exposure to pH 7.4 buffer solution for various times reveals degradation behavior that differs from the unblended polymer. New primary ion sources, specifically polyatomic primary ions have allowed TOF-SIMS to be applied to the analysis of materials that were previously not ideally suited to the technique. With the increased use of these new sources a more thorough understanding of the interaction of the primary ion with different sample types is important. A secondary focus of this thesis work involves studying various primary ion sources and the subsequent secondary ions that they generate to elucidate and explain the differences between cluster and monatomic primary ion bombardment. A particular focus was put on analysis of polymer molecular weight distributions.