Synthesis and Erosion Properties of PEG-Containing Polyanhydrides

To tailor the erosion rate of polyanhydrides while retaining their surface erosion characteristics, new three-component polyanhydrides of sebacic acid, 1,3-bis( p -carboxyphenoxy)propane and poly(ethylene glycol) were synthesized. The hydrophilicity of the polymer increased and its mechanical strength decreased with increasing PEG content. Correspondingly, the erosion rate increases with increasing PEG content, whereas it decreases with increasing specimen thickness. This indicates that the incorporation of poly(ethylene glycol) into traditional two-component polyanhydrides retains their surface erosion properties while making the erosion rate tunable. The new polyanhydrides hold potential for drug delivery applications.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56103/1/620_ftp.pd

Syntheses and functionalization of block copolymers based on polystyrene-block-poly(4-vinylpyridine) and polystyrene-block-polyisoprene

published_or_final_versionChemistryDoctoralDoctor of Philosoph

An NMR-Based Method for Multiphase Methane Characterization in Coals

Discriminating multiphase methane (adsorbed and free phases) in coals is crucial for evaluating the optimal gas recovery strategies of coalbed methane (CBM) reservoirs. However, the existing volumetric-based adsorption isotherm method only provides the final methane adsorption result, limiting real-time dynamic characterization of multiphase methane in the methane adsorption process. In this study, via self-designed nuclear magnetic resonance (NMR) isotherm adsorption experiments, we present a new method to evaluate the dynamic multiphase methane changes in coals. The results indicate that the T2 distributions of methane in coals involve three different peaks, labeled as P1 (T2 < 8 ms), P2 (T2 = 20–300 ms), and P3 (T2 > 300 ms) peaks, corresponding to the adsorbed phase methane, free phase methane between particles, and free phase methane in the sample cell, respectively. The methane adsorption Langmuir volumes calculated from the conventional volumetric-based method qualitatively agree with those obtained from the NMR method, within an allowable limit of approximately ~6.0%. Real-time dynamic characterizations of adsorbed methane show two different adsorption rates: an initial rapid adsorption of methane followed by a long stable state. It can be concluded that the NMR technique can be applied not only for methane adsorption capacity determination, but also for dynamic monitoring of multiphase methane in different experimental situations, such as methane adsorption/desorption and CO2-enhanced CBM