Neodymium Based Catalytic System for the Polymerization of Dienes, Lactones and Vinyl Monomers
Kularatne, Ruvanthi Nilanga
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Polydienes, polylactones, poly(methyl methacrylate), poly(methyl acrylate), polystyrene and poly(vinyl acetate) are some common polymers which are utilized in applications ranging from rubber industry to biomedical applications. These materials are synthesized by various catalysts and by various polymerization techniques such as anionic, cationic, radical, and coordination polymerization. While some monomers such as styrene can be polymerized from all these techniques, monomers such as vinyl acetate can only be polymerized via radical polymerization. Synthesis of copolymers between these different types of monomers is extremely important to tune the properties of the resulting polymers to match the specific application. Unfortunately, due to the mismatch between the polymerization technique and the monomers, synthesis of copolymers between these classes is somewhat limited. In this dissertation, a coordination catalytic system that has the ability to make homopolymers, as well as copolymers between these different classes of monomers is introduced. Chapter 1 will focus on the development of neodymium-based catalytic systems for the polymerization of dienes, lactones, and vinyl monomers. The compounds used as co-catalyst and the effect of polymerization conditions are explored. The advances in the synthesis of copolymers and the mechanistic aspect of the neodymium-based catalysts for the polymerization of dienes and lactones are discussed. In Chapter 2, the synthesis of the novel NdCl₃⋅3TEP (TEP = triethyl phosphate) catalyst and the polymerization of dienes and vinyl monomers with triisobutylaluminum (TIBA) co-catalyst is presented. Pseudo-living characteristics for the polymerization of dienes and the synthesis of copolymers between diene-diene, diene-vinyl, and vinyl-vinyl are demonstrated in this chapter. Chapter 3 extends the ability of NdCl₃⋅3TEP/TIBA catalytic system for the polymerization of lactones. Unsubstituted and γ-substituted-ε-caprolactone monomers are used to show the superiority of this catalytic system over the conventional catalytic systems that are in use for the polymerization of lactones. Presented in Chapter 4 is the application of a polycaprolactone synthesized by the NdCl₃⋅3TEP/TIBA catalytic system for the combined delivery of an anticancer drug, doxorubicin and a histone deacetylase inhibitor, 4-phenylbutyric acid. The polymerization of the γ-substituted-ε-caprolactone monomer was only achievable with the NdCl₃⋅3TEP/TIBA catalytic system. A comparison of the polymerization with other catalytic systems, the formation of nanoparticles with the polymer, characterization of the nanoparticles and its biological studies are discussed.