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In the effort to design new photochromic material for integral parts in many scientific processes I have synthesized, characterized and studied photophysical characteristics of new photochromic polymers. By coupling the properties of a photochromic unit with that of polymers one can anticipate the discovery of new viable photochromic materials that has the possibility to enhance the processes in many scientific fields. Water solubility in photochromic processes gives life to new innovations and possibilities in the scientific community. As part of my dissertation I have designed, synthesized and studied new water soluble photochromic polymers. The findings in this dissertation will help to reveal the understandings of incorporating/coupling a photochromic molecule with that of polymers.

As a part of a larger effort towards the fundamental understanding of mechanical behaviors of polymers toughened by nanoparticles, this dissertation focuses on the structure-property relationship of epoxies modified with nano-sized poly(ethylene-altpropylene)- b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) micelle particles. The amphiphilic BCP toughener was incorporated into a liquid epoxy resin and selfassembled into well-dispersed 15 nm spherical micelle particles. The nano-sized BCP, at 5 wt% loading, can significantly improve the fracture toughness of epoxy (ca. 180% improvement) without reducing modulus at room temperature and exhibits only a slight drop (ca. 5 �C) in glass transition temperature (Tg). The toughening mechanisms were found to be BCP micelle nanoparticle cavitation, followed by matrix shear banding, which mainly accounted for the observed remarkable toughening effect. The unexpected ?nano-cavitation? phenomenon cannot be predicted by existing physical models. The plausible causes for the observed nano-scale cavitation and other mechanical behaviors may include the unique structural characteristics of BCP micelles and the influence from the surrounding epoxy network, which is significantly modified by the epoxy-miscible PEO block. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. Structure-property relationships of this nano-domain modified polymer are discussed. In addition, other important factors, such as strain rate dependence and matrix crosslink density effect on toughening, have been investigated. This BCP toughening approach and conventional rubber toughening techniques are compared. Insights on the decoupling of modulus, toughness, and Tg for designing high performance thermosetting materials with desirable physical and mechanical properties are discussed.

This research work examines the process of block copolymer membrane fabrication by self-assembly combined by non-solvent induced phase separation. Self-assembly takes place from the preparation of the primordial solution until the moment of immersion in a non-solvent bath. These mechanisms are driven thermodynamically but are limited by kinetic factors. It is shown in this work how the ordering of the assembly of micelles is improved by the solution parameters such as solvent quality and concentration of block copolymer. Order transitions are detected, yielding changes in the morphology. The evaporation of the solvents after casting is demonstrated to be essential to reach optimum membrane structure. The non-solvent bath stops the phase separation at an optimum evaporation time.

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Thesis / Master of Applied Science (MASc)

The Digitization Centre has determined that pages x, 30 and 106 are not in this thesis or the vault copy. / Pyrenebutylamide-labeled poly(N-isopropylacrylamide-co-N-acryloyl-L-valine) copolymers have been prepared by two different methods and their physicochemical properties have been compared. One sample was prepared via copolymerization of N-isopropylacrylamide (NIPAM), and N-acryloyl-valine (NAV) with N-[4-(1-pyrenyl)butylacrylamide], the other by post-modification of poly(N-isopropylacrylamide-co-N-acryloyl-L-valine-co-N-acryloxysuccinimide) copolymer with pyrenebutylamine hydrochloride. The polymers were characterized by 1H NMR and FTIR spectroscopy, Differential scanning calorimetry and light Scattering. Though the use of fluorescence spectroscopy several differences between the two types of copolymers were detected. By comparing the extent of pyrene excimer emission and pyrene monomer emission from solutions of the two polymers, it was concluded that the copolymer obtained by direct copolymerization (method 1) had an inherent ''blocky" microstructure, while the copolymers obtained by the post-modification route presented a more random microstructure. Intrapolymeric interaction exists in solutions of low copolymer concentrations. At higher concentrations both inter-and intrapolymeric interactions coexist. The presence of a number carboxylic groups in the PNIP AM chain significantly modifies the conformation properties of the copolymers, compared to poly(N-isopropylacrylamide). The copolymers contract and expand in response to external conditions such as pH and temperature. Their Lower critical solution temperature (LCST) changes with pH. The interactions between polymers and fluorescence quenchers were investigated. The quenching results reveal that hydrophilic cationic quenchers interact strongly with the randomly labeled-copolymer. Hydrophobic cationic species interact strongly with ''blocky" pyrene labeled copolymer. Anionic quencher interacts quite weakly with both copolymers owing to electrostatic repulsion. / Thesis / Master of Science (MS)

In this dissertation, we studied two-phase microfluidics as a platform for the controlled synthesis of drug delivery polymeric nanoparticles (PNPs). The block copolymer we studied was poly(ε-caprolactone)-block-poly(ethylene oxide) (PCL-b-PEO). The anticancer drug we studied was paclitaxel (PAX). First, we explored microfluidic control of nanoparticle structure (size, morphology, and core crystallinity) on PCL-b-PEO PNPs without loaded PAX. We demonstrated the reproducible variability of PCL-b-PEO nanoparticle size and morphology. Microfluidic control of nanoparticle size and morphology was found to arise from the interplay of flow-induced particle coalescence and breakup. Next, we demonstrated the linear dependence of PCL core crystallization on flow-rate. We attributed this dependence of PCL core crystallization on flow-induced crystallization. We then used our microfluidic device to control PAX-loaded PNP structure and function (small molecule loading efficiency, diffusional release kinetics, and cytotoxicity). At low drug loading ratios (r < 0.1), we demonstrated reproducible variability of PAX-loaded PNP size and morphology. With increasing flow rate we were able to manufacture PNPs of high aggregation number. We were also able to reproducibly demonstrate the linear dependence of PCL core crystallinity on flow rate. Furthermore, PAX loading efficiency was dependent on PNP size and morphology. Formulations which consisted of cylindrical and lamellar type morphologies typically had higher PAX loading efficiencies, than formulations which consisted of spherical structures. Next, we studied diffusional PAX release, increasing core crystallinity correlated with slowing diffusional PAX release kinetics. At high drug loading ratios (r > 0.1), we demonstrated reproducible control of PAX-loaded PNP structure and function. PCL core crystallinity was a major factor influencing PNP size and morphology. Samples with high core crystallinity formed PNP structures with low internal curvature. Furthermore, core crystallization had a large influence on PAX loading efficiency; as samples with high PAX loading efficiency correlated with low PCL core crystallinity. With respect to diffusional PAX release, we found that increasing PCL core crystallinity correlated with slowing diffusional PAX release kinetics. Next, we studied the cytotoxicity of our PAX-loaded PNPs using the MCF-7 cancer cell line. Due to the complex nature of the interactions between our PAX-loaded PNPs and the cancer cells, we were not able to elucidate the exact influence of flow rate on PNP cytotoxicity. / Graduate

This paper considers a free energy functional and corresponding free boundary problem for multilayered structures which arise from a mixture of a block copolymer and a weak solvent. The free boundary problem is formally derived from the limit of large solvent/polymer segregation and intermediate segregation between monomer species. A change of variables based on Legendre transforms of the effective bulk energy is used to explicitly construct a family of equilibrium solutions. The second variation of the effective free energy of these solutions is shown to be positive. This result is used to show more generally that equilibria are local minimizers of the free energy.