Poly(2-ethyl-2-oxazoline) (PEOX) is a nonionic, synthetic polymer which is soluble in both a variety organic solvents and water. The negative entropy of mixing of this polymer in aqueous solution suggested that it adopts a rigid conformation such as a helix in aqueous solution. Hydrogen bonding between PEOX and water molecules is thought to facilitate a special conformation that is specific to aqueous solution. The intent of this work is to investigate the conformation of PEOX in aqueous solution and consequently propose the mechanism by which it would adsorb onto cellulose and make it a valuable additive in paper processing. This work ultimately contributes to the greater matter of understanding the mechanisms by which water solvates nonionic polymers. Viscometry measurements of PEOX in water show that its shape scales similar to a random coil and that its molecules collapse in the presence of sodium chloride. Investigation into the molecular structure of PEOX through molecular scale simulations have revealed that although a rigid helical conformation does not exist, the potential exists for PEOX to have secondary helical structure in both water and other solvents. Without the rigid predicted structure, however, it is not surprising that PEOX does not adsorb well on cellulose. Comparing this folded helical conformation to a random coil conformation reveals that the random coil produces a lower energy system in water.

The research presented in this thesis focuses on the synthesis of three amphiphilic block copolymer systems containing poly(ethylene oxide) (PEO) blocks. The polymer systems were developed for use in biomedical applications. The first of these is a series of poly(ethylene oxide-b-oxazoline) (PEO-b-POX) diblock copolymers for use in the progress towards novel non-viral gene transfer vectors. Poly(ethylene oxide-b-2-ethyl-2-oxazoline) (PEO-b-PEOX) and poly(ethylene oxide-b-2-methyl-2-oxazoline) (PEO-b-PMOX) were investigated. The PEOX block was hydrolyzed with acid to form linear polyethylenimine (L-PEI). The polycation L-PEI is well known for its DNA binding efficiency but the water solubility of the resulting DNA/polymer complex is limited. Addition of a PEO block is directed towards the formation of a water dispersible DNA/copolymer complex. Dynamic light scattering of the PEO-b-PEOX and PEO-b-PEI block copolymers indicated that both systems existed as single chains in aqueous solution at pH 7. PEO copolymers also play a significant role in the formation of magnetic magnetite nanoparticles, which are dispersible in water at biological pH (pH =7). There is significant interest in the design of magnetic nanoparticle fluids for biomedical applications including magnetic field-directed drug delivery, magnetic cell separations, and blood purification. For use in vivo, the magnetite nanoparticles must be coated with biocompatible materials. Such polymers render the nanoparticles dispersible in water. Harris1 et al. synthesized PEO based, polyurethane triblocks with pendant carboxylic acid groups for use in formation of stable aqueous magnetic fluids. Building from this work, two polyurethane and polyurethaneurea systems were synthesized with 1300 g/mol PEOX and 2500 g/mol and PEOX2070 g/mol poly(ethylene oxide-co-propylene oxide) tailblocks, respectively. The PEO/PPO random copolymer contained about 25 weight percent PPO, and this disrupted the capacity of the PEO to crystallize. The PEOX based urethane triblocks were synthesized through reacting the tailblocks with the monomers for the center block whereas the PEO/PPO based polyurethaneurea was synthesized through forming the central urethane block with pendant acid groups first and then terminating the copolymer with the monofunctional copolymer. Terminal amine groups on the PEO/PPO tailblock afforded a triblock linked with two urea groups. The new polyurethanes with the PEOX tailblocks and the new polyurethaneurea with the PEO/PPO tailblocks could be utilized to efficiently stabilize magnetite nanoparticles in water. / Master of Science

Poly(ethylene oxide) (PEO) and poly(2-ethyl-2-oxazoline) (PEOX) are biocompatible polymers that act as hydrophilic "stealth" drug carriers. As block copolymers, the PEOX group offers a wider variety of functionalization. The goal of this project was to synthesize a poly(ethylene oxide)-b-poly(2-ethyl-2-oxazoline) (PEO-b-PEOX) block copolymer and functionalize pendent groups of PEOX with phosphonic acid. This was achieved through cationic ring opening polymerization (CROP) of 2-ethyl-2-oxazoline monomer onto PEO. These polymerizations used tosylsulfonyl chloride as initiator. Size-exclusion chromatography (SEC) was used to determine the molecular weights of the block copolymers. Two samples of 1:2 and one sample of 1:3 of PEO-to-PEOX block copolymers were made. These samples underwent partial hydrolysis of the PEOX pendent groups to form the random block copolymer, poly(ethylene oxide)-b-poly(2-ethyl-2-oxazoline)-co-poly(ethyleneimine) (PEO-b-PEOX-co-PEI). These reactions showed that there was a degree of control based on the moles of acid. Diethyl vinyl phosphonate was attached to the nitrogen of PEI units via Michael addition where the phosphorylation left <1% of PEI units unattached. The ethyl groups on the phosphonates were further hydrolyzed off phosphonate with HCl acid leaving phosphonic acid. After each step of synthesis, structures and composition were confirmed using ¹H NMR. Due to the nature of the phosphonic acid, the polymer can be utilized in the incorporation and release of cationic drugs. / Master of Science

Size exclusion chromatography is the method of choice for characterizing molecular weights and molecular weight distributions of polymers. An important advancement in SEC is multidetection SEC which includes multi-angle laser light scattering, viscometry, refractive index and UV spectroscopy to analyze block and graft copolymers as well as polymers with oligomeric molecular weights. Oligomeric molecular weights present special challenges since the light scattering and viscosity detectors are more sensitive to higher molecular weights and both detectors have low molecular weight threshold values. The molecular weights and distributions of poly(2-ethyl-2-oxazoline) oligomers and block copolymers as well as poly(2-ethyl-2-oxazoline) were investigated by SEC using multiple detectors. Both a universal calibration method and light scattering were used to determine molecular weights and molecular weight distributions. The solvent was N-methylpyrrolidone that contained 0.05M LiBr used to minimize interactions among the polymers and solvent. SEC was used to establish that the diblock copolymers had heterogeneous compositional distributions. The low molecular weights of the diblock and homopolymer made it necessary to use the universal calibration method with combined refractive index and viscometry detectors to determine absolute molecular weights. / Master of Science

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal