Nonlinear Polymeric Architectures via Olefin Metathesis

Citation

Gorodetskaya, Irina A. (2009) Nonlinear Polymeric Architectures via Olefin Metathesis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WRYR-4674. https://resolver.caltech.edu/CaltechETD:etd-04262009-232200

Abstract

The research presented in this thesis focuses on application of olefin metathesis to the construction of hyperbranched and cyclic macromolecules. The olefin metathesis reaction is briefly reviewed in Chapter 1, along with its applications in polymer synthesis. A very mild, simple, and modular, olefin metathesis-based hyperbranched polymerization route is presented in Chapter 2. This method utilizes the cross metathesis selectivity of the functional group tolerant N-heterocyclic carbene ruthenium catalyst towards different types of alkenes, and it can be applied to the polymerization of many easily prepared ABn monomers. Moreover, the same method can be used to post-synthetically functionalize such polymers for realization of their substrate carrying potential. Chapter 3 describes one such functionalization example—a pyrene analyte is attached to a metathesis derived hyperbranched polymer. This modification of the polymer provides insight into its solution structure relative to a linear analog. In addition, molecular weight control of the metathesis hyperbranched polymerization is discussed in detail in Chapter 4. The careful choice of the catalysts loading and the use of a multifunctional core are found to be important parameters in preparation of polymers which span a range of molecular weights.

Even well-established materials, such as polyethylene, can benefit from olefin metathesis and the unusual polymeric architectures it can efficiently create. For example, a cyclic polymer which lacks end groups, as opposed to having many end groups like a hyperbranched polymer, is expected to possess unique physical properties. The preparation of cyclic and linear polyethylenes and the study of their relative rheological properties are described in Chapter 5. The polymerization methodology outlined in this chapter takes advantage of ring-expansion metathesis polymerization—a facile method for the synthesis of cyclic macromolecules. Some efforts directed at molecular weight control of this cyclic polymerization are also discussed.

Thesis Files