Graduation Year

2012

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Chemistry

Major Professor

Julianne P. Harmon

Keywords

Cross- linkers, Decomposition, Dielectric analysis, Procainamide HCl, rho-ZMOF, Thioanisole

Abstract

The design and synthesis of new finely tunable porous materials has spurred interest in developing novel uses in a variety of systems. Zeolites, inorganic materials with high thermal and mechanical stability, in particular, have been widely examined for use in applications such as catalysis, ion exchange and separation. A relatively new class of inorganic-organic hybrid materials known as metal-organic frameworks (MOFs) has recently surfaced, and many have exhibited their efficiency in potential applications such as ion exchange and drug delivery. A more recent development is the design and synthesis of a subclass of MOFs based on zeolite topologies (i.e. ZMOFs), which often exhibit traits of both zeolites and MOFs. Bio-compatible hydrogels already play an important role in drug delivery systems, but are often limited by stability issues. Thus, the addition of ZMOFs to hydrogel formulations is expected to enhance the hydrogel mechanical properties, and the ZMOF-hydrogel composites should present improved, symbiotic drug storage and release for delivery applications. Herein we present the novel composites of a hydrogel with a zeolite-like metal-organic framework, rho-ZMOF, using 2-hydroxyethyl methacrylate (HEMA), 2,3-dihydroxypropyl methacrylate (DHPMA), N-vinyl-2-pyrolidinone (VP) and ethylene glycol dimethacrylate (EGDMA), and the corresponding drug release. An ultraviolet (UV) polymerization method is employed to synthesize the hydrogels, VP 0, VP 15, VP 30, VP 45 and the ZMOF-VP 30 composite, by varying the VP content (mol%). The rho-ZMOF, VP 30, and ZMOF-VP 30 composite are all tested for the controlled release of procainamide (protonated, PH), an anti-arrhythmic drug, in phosphate buffer solution (PBS) using UV spectroscopy.

Blister agents are chemical compounds that induce severe skin, eye, mucosal pain and irritation. The research focuses on sequestering a blister agent analog, thioanisole in hydrogels. HEMA polymers and copolymers of HEMA with 2,3-dihydroxyproyl methacrylate (DHPMA) and vinyl pyrrolidone (VP) were synthesized with crosslinkers of various dimensions. These were: ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DiEGDMA), triethylene glycol dimethacrylate (TriEGDMA), tetraethylene glycol dimethacrylate (TetEGDMA) and neopentyl glycol dimethacrylate (NPEGDMA). Equilibrium swelling was characterized gravimetrically and pore size was estimated via scanning electron microscopy (SEM). Glass transition temperatures were measured by differential scanning calorimetry (DSC). The absorption of thioanisole in methanol was characterized with via ultra-violet (UV) spectroscopy.

Poly(2-hydroxyethyl methacrylate) (PHEMA) composites constructed from a paddle-wheel, a secondary building unit (SBU) for metal organic frameworks, Cu2(p-OH benzoate)4(DMSO)2*2DMSO (CPW) were also investigated for a broad analysis of dielectric spectra. The dielectric spectrum of poly(2-hydroxyethyl methacrylate) and its copolymer with Poly(2,3-dihydroxy propyl methacrylate) (PDHPMA) are already reported in the literature. This study delineates the effects on the dielectric behavior as a result of CPW addition. The dielectric permittivity and the loss factor were measured using a dielectric analyzer in the frequency range of 1 Hz to 100 k Hz and between the temperature range of -140 and 250°C. The electric modulus formalism was used to reveal the viscoelastic and conductivity relaxations present in the polymers. Significant changes were observed as CPW concentration increased from 0.1 to 0.5 wt%. It was determined through DSC that the glass transition temperature increased with the filler concentration. The secondary dielectric relaxations were also affected as it was recorded that the activation energy for the γ, Β, and conductivity relaxation increased with CPW content. AC and DC conductivity are also evaluated. The ionic conductivity data revealed that the CPW impedes the ion mobility when compared to the neat PHEMA.

Organic azides have become a very vital class of chemical compounds in synthetic organic chemistry and in many more fields due to their applications. Azido compounds are considered high-energetic compounds and are studied very little due to their explosive nature. There is an urge to evaluate the thermal stability of this wide variety of compounds which have tremendous applications in synthetic as well as organic chemistry. Here in we report the thermal stability of some organic azides such as sulfonyl, phosphoryl and carbonyl azides using differential scanning calorimetry (DSC) as an evaluating tool. Initial temperature of decomposition (Ti) and temperature of maximum decomposition (Tmax) are recorded. The area under exotherm peak during decomposition is used to determine the energy of decomposition (Ed) and is compared to threshold value for hazardous/explosive compounds. The effect of substituent groups at different positions, nature of the substituent groups (electron donating or electron withdrawing) and the steric hindrance on the thermal stability of these azides is studied in detail to verify the explosive nature of these compounds.

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