Doctor of Philosophy, University of Akron, 2011, Polymer Science

A variety of methods were used to make polymers with different architecture and functionalities. The linking chemistry of vinyldimethylchlorosilane (VDMCS) with poly(styryl)lithium (Mn = 1,700-3,000 g/mol) was studied. The average degree of branching varied from 7.5 to 9.4 with an increase in concentration of VDMCS (1.2 to 5.2 eq). The intrinsic viscosities and melt viscosities (at 160 °C) of the star polymers were found to be less than half of that of the corresponding linear polystyrenes. α-Pyrrolidine-functionalized polystyrene (Mn = 2,700 g/mol, Mw/Mn = 1.03, 92.5%) was successfully synthesized from α-chloromethyldimethylsilane-functionalized polystyrene(Mn = 2,600 g/mol, Mw/Mn = 1.02) based on NMR spectroscopy, MALDI-TOF and ESI mass spectrometry. The stability of silyl hydride groups under atom transfer radical polymerization conditions was proven by copolymerizing methyl methacrylate and (4-vinylphenyl)dimethylsilane (VPDS). Tapered block copolymers of isoprene, VPDS, and styrene with narrow molecular weight distributions (1.04 and 1.05) were synthesized via anionic polymerization. Evidence regarding the topology of cyclic polybutadienes was obtained by Atomic Force Microscopy of grafted polymers obtained by grafting an excess of silyl hydride functionalized polystyrene (Mn = 8,300 g/mol, Mw/Mn =1.01) onto cyclic polybutadiene(Mn=88,000 g/mol, Mw/Mn = 2.0). The reactivity of polyisobutylene carbocations was compared with respect to competitive electrophilic addition to a vinyl group versus silyl hydride transfer by investigating the reaction with VPDS. Based on GPC results, and 1H and 13C NMR spectroscopy, no evidence for any vinyl group addition was observed. A successful attempt was made to prepare electrospun fibers from fluorofunctionalized styrene-butadiene elastomers. The water contact angle of these surfaces was found to be 162.8o ± 3.8o for the fibrous mat of the fluorinated polymers as compared to 151.2o ± 2.4o for the analogous fibrous (open full item for complete abstract)

Committee: Roderic Quirk Dr. (Advisor); Mark Foster Dr. (Committee Chair); Judit Puskas Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member); Kevin Cavicchi Dr. (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2021, Chemistry

This dissertation will focus on the use of multidimensional mass spectrometry (MS) techniques for the characterization of complex polymeric materials and mixtures, especially of samples that are impossible or difficult to characterize by other analytical methods. The research can be separated into two categories; applying separation techniques and mass spectrometry to polymeric mixtures, and using atmospheric solids analysis probe (ASAP)-MS for the analysis of cross-linked polymeric networks. Poly-glycidyl phenyl ether (PGPE) samples synthesized via zwitterionic ring opening polymerization by the Grayson Research Group (Tulane University) were initially analyzed using matrix assisted laser desorption ionization (MALDI) MS. Although able to confirm the presence of linear products, MALDI-MS was unable to distinguish between the tadpole and cyclic products, both of which are produced by back-biting reactions and are structural isomers. To overcome this problem, ultraperformance reversed-phase liquid chromatography interfaced with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) was employed. These experiments showed that the tadpole isomer elutes before the cyclic structure due to the increased polarity associated with a free hydroxyl end group on the tadpole tail. The achieved separation showed that the ratio of tadpole to cyclic species increases with each repeat unit. These results agree with the synthetic predictions, as the potential for forming tadpole structures by back-biting should increase with increased polymer chain length. Once separated, the two isomers could be independently analyzed by tandem mass spectrometry. The cyclic and tadpole species exhibit unique fragmentation patterns and include structurally diagnostic fragments for each structure. The importance in these peaks lies in their ability to provide information about the tadpole to cyclic ratio, without the need for inline separation techniques prior to MS. Surfactants are co (open full item for complete abstract)

Committee: Chrys Wesdemiotis (Advisor); Claire Tessier (Committee Chair); Adam Smith (Committee Member); Aliaksei Boika (Committee Member); Wang Junpeng (Committee Member) Subjects: Chemistry; Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2016, Chemistry

The spectroscopy, photophysics, and photochemistry of organometallic complexes of the general type [Re(X)(CO)3(diimine)]0/+ (X= halogen, CN-, alkyl, benzyl, pyridyl, phosphine, isonitrile, or metal fragment group) have received much attention since the 1970s, when their excited state properties were recognized and presented by Wrighton. These organometallic complexes occupy an important position in the photophysics and photochemistry of transition-metal complexes due to their potential uses in many applications such as emission sensitizers, photosensitizers, photooxidants, photocatalysts and electrocatalysts. Due to their promising photophysical properties as well as their excellent thermal and chemical stabilities, ReI(CO)3 complexes have been incorporated into metal containing polymers and macromolecules as emitters in light emitting diodes (LEDs), photosensitizers in photovoltaic devices (PVs) and luminescent probes in biological systems. In the second and third chapters, the syntheses and characterization of monomeric and dimeric ReI(CO)3 complexes is described by using one-pot conditions via metal mediated Schiff base complexation. These compounds are fully characterized by X-ray crystallography, NMR, mass spectroscopy, UV-visible and cyclic voltammetry. Cyclic voltammetry experiments confirm that in dimeric complexes the bridging ligands unit do mediate coupling between the Re(CO)3X coordination complexes. Two-electron redox behaviour allows to calculate a comproportionation constant (Kc), which corresponds to the degree of coupling as the presence of an apparent inter-valence charge transfer (IVCT) band between the ReI(CO)3 centers. DFT and TDDFT calculations indicate that the reductions are ligand-centered, which support intra-ligand transitions for the IVCT bands. In the next chapter, the synthesis of series of main chain organometallic polymers (MCOPs) containing Re(CO)3Cl(diimine) cores is described. Three different types of polymerization reactions, in (open full item for complete abstract)

Committee: Christopher J Ziegler Dr. (Advisor); Claire A. Tessier Dr. (Committee Member); Yi Pang Dr. (Committee Member); Wiley J. Youngs Dr. (Committee Member); Steven S.C. Chuang Dr. (Committee Member) Subjects: Chemistry