<p> This thesis presents a study on silane based polymerization in two parts. </p> <p> In Part A, diphenylvinylsilane (1) underwent oligomerization with initiation by azo(bisisobutyronitrile) (AIBN) or benzoyl peroxide (BPO). The vinyl groups were preferentially consumed under either set of conditions. Several products were isolated; these included oligomers 3, an AIBN adduct 4, a dimer 5, and a trimer 6. The residual SiH moieties could be subsequently coupled hydrosilylatively with alkynes or vinylsilicones. The efficiency of the radical reactions was very low. 15% starting material was recovered even with 200 mol% of initiating radicals added to the reaction mixture. The relative radical reactivities of the two functional groups is discussed.</p> <p> In Part B, 1 was radically copolymerized with styrene and methyl methacrylate (MMA). From the results of infrared and 1H NMR it was determined that 1 participated in copolymerization via a vinyl type polymerization and not in the form of a hydrogen-transfer type polymerization. Residual SiH groups along the backbone of the polymer remained reactive. A vinylsilicone and 9-vinylanthracene were grafted onto the copolymer from MMA and 1 by hydrosilylation and radical methods, respectively.</p> / Thesis / Master of Science (MSc)

In this thesis, we use the self-consistent field theory (SCFT) to study neutral and charged block copolymer melts and blends in thin films and bulk. We showcase the utility of the SCFT by applying it to a number of different model systems. In our first study, we examined the elastic properties of multi-component bilayer membranes composed of amphiphilic AB/ED diblock copolymers. We focused on the effects of chain architecture and interactions between the amphiphilic molecules on the line tension or edge energy of a membrane pore. We discovered a direct relationship between the effective volume of the amphiphilic molecules, which is dictated by their architecture, and the line tension. We found that the addition of cone-shaped molecules to the membrane results in a decrease in the line tension. The opposite effect is seen for inverse cone-shaped amphiphiles, where an increase in their concentration results in an increase of the line tension. Studies two and three fall under the theme of directed self assembly of block copolymer thin films. First we examined the effects of ion concentration on the strength of the external electric field required to reori- ent lamellar domains from the parallel to the perpendicular orientation. The change in the critical electric field is found to be dependent on whether the neutral or charged polymer species is favoured by the top and bottom surfaces. In the second study, we examined the mechanism of using the entropic effect to direct the self assembly of micro domains in star block copolymer thin films. We control the architecture of star block copolymers by varying the number of arms, ranging from a linear chain with 1-arm to 4-arm star block copolymers. Using both experiments and SCFT, we showed that the entropic effect is enhanced in star block copolymer blends with greater number of arms. Furthermore, we showed that the entropic effect can be used to direct the self assembly of micro domains perpendicular to the substrate. In our last study, we examined the unbinding transition of the α-BN phase in pentablock terpolymer/ homopolymer blends. We constructed a phase diagram of the system as a function of homopolymer con- centration. We discovered that the unbinding transition is preempted by the macrophase separation of the blends into block copolymer rich/ homopolymer rich domains. The results presented in this thesis help advance our understanding of various properties of polymeric systems, such as the elastic properties of multi-component membranes, directed self assembly in block copolymer thin films and the phase behaviour of block copolymers in bulk. / Thesis / Doctor of Philosophy (PhD)

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The use of waste gas such as carbon dioxide (CO2) to prepare useful and valuable polymers benefits both the economy and the environment. Various strategies have been developed to reduce CO2 emission as well as to transfer CO2 into high-value products. CO2/epoxide copolymerization is one of the most promising methods of not only reducing the CO2 emission from the atmosphere but also producing biodegradable CO2-based materials that are CO2 as source-abundant, renewable, cheap, non-flammable and non-toxic. However, the activation of CO2 is one of several problems associated with the polymerization of CO2 due to its stability as a thermodynamic end product. Herein, my dissertation describes the effectiveness of new lithium/phosphazene complexes to generate highly active species for CO2/epoxide copolymerization and to capture/activate CO2 molecules for the nucleophilic attack of the active species. Well-defined polycarbonates and polycarbonate-based block copolymers are produced that have control of molecular weights, unimodal distributions and narrow molecular weight distributions (Chapter 3 and 4). Besides, these complexes provide access to prepare CO2-based triblock copolymers that are powerful candidates to serve as the next generation of thermoplastic elastomers (Chapter 4). Additionally, these complexes are applied for the anionic polymerization of petrochemical-based sources such as styrene and dienes producing polymers in faster rate of polymerization with control of molecular characteristics (Chapter 2). A general introduction of polymers and their classification based on composition, chemical structure, mechanical properties, degradability, source, applications, and preparative methods, is covered in Chapter 1

No / Crystallization of an isotactic polypropylene (iPP) homopolymer and two propylene/ethylene random copolymers (RACO), induced by high-stress shear, was studied using in situ synchrotron wide-angle X-ray diffraction (WAXD) at 137 °C. The “depth sectioning” method (Fernandez-Ballester Journal of Rheology 2009, 53 (5), 1229−1254) was applied in order to isolate the contributions of different layers in the stress gradient direction and to relate specific structural evolution to the corresponding local stress. This approach gives quantitative results in terms of the specific length of fibrillar nuclei as a function of the applied stress. As expected, crystallization becomes faster with increasing stress—from the inner to the outer layer—for all three materials. Stress-induced crystallization in a RACO with 7.3 mol % ethylene content was triggered at only 1 °C below its nominal melting temperature. The comparison of iPP and RACO’s with 3.4 and 7.3 mol % ethylene monomer reveals the effect of ethylene defects on high-stress shear induced crystallization at 137 °C. It is found that, for a given applied stress, the specific nuclei length formed by flow increases with ethylene content—which is attributed to a greater high molecular weight tail. However, the linear growth rate is significantly reduced by the presence of ethylene comonomers and it is found that this effect dominates the overall crystallization kinetics. Finally, a time lag is found between development of parent lamellae and the emergence of daughter lamellae, consistent with the concept of daughter lamellae nucleated by homoepitaxy on the lateral faces of existing parent lamellae.

Segmented copolymer systems composed of an amorphous g1assy engineering polymer as one segment and a potentially anisotropic polyester as the second segment were synthesized and investigated. The engineering thermoplastic segment was based on various all aromatic poly(arylene ether sulfooes) derived from the nucleophilic aromatic substitution reaction between hydroquinone, biphenol, and dichlorodiphenylsulfone. This reaction was conducted in the presence of potassium carbonate and anhydrous aprotic dipolar solvents. Poly(biphenol terephthalate) and poly(oxybenzoate) were synthesized in situ as the second, potentially anisotropic, sem;crystalline segment. These segmented copolymers were synthesized either by solution t interfacial, or melt acidolysis techniques. The melt acidolysis technique was used to synthesize the segmented copolymers with high poly(arylate) contents. The morphology of the copolymers was found to be totally amorphous for those capolymers with low levels of the poly(arylates). They were semicrystalline when the poly(arylate) contents were increased beyond a critical value of about 15 weight percent. Differential scanning calorimetry, optical microscopy, and wide angle X-ray scattering were used to probe the copolymer morphology. The chemical structures of the segmented copolymers were studied through the use of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy (both ¹H and ¹³C). As the weight percentage of the poly(arylate) was increased, a very significant improvement in the solvent resistance was noted. Evidence of anisotropy and liquid crystallinity in the copolymers was provided by optical microscopy, differential scanning calorimetry, and wide angle X-ray scattering. / Ph. D.