Theoretical and Experimental Studies of Guest Migration within Supramolecular Copolymers as a Function of Host-Guest Sequence and System Architecture

This dissertation is divided into twelve chapters, detailing the theoretical and experimental work involved in this project and their results. The first chapter places the research into its historical context within the fields of polymer sequencing and supramolecular systems featuring intramolecular guest migration between differential host sites. The second chapter begins the discussion of the theoretical aspects of the project by listing the rules and characteristics that define the model two-host, one-guest supramolecular copolymer system. Within, we define and analyze some potential consequences of guest migration as a function of specific host sequence. The chapter concludes with a consideration of applicable supramolecular architectures, realized and hypothetical, that may be employed either simply for conceptual understanding of the theory, or for experimental targets to test the theory. The third through fifth chapters apply the rules and characteristics as described by the theory to linear perfect block, perfect alternating, and perfect random, i.e., statistical, copolymer sequences, respectively. The relative extents of guest migration are mathematically determined, with separate equations derived for each copolymer architecture for the purpose of determining the migrating guest fraction (MGF). Patterns in migration are observed for each copolymer type that are used later for the formation of a general limit equation. The sixth chapter explores the overall changes to guest migration within the aforementioned sequences within a cyclic rather than linear architecture. Unique patterns to migration are observed respective of sequence, and unique differences are observed and noted for identical sequence types within the different architectures. New equations for the determination of migrating guest fraction are derived for the cyclic species according to sequence type. The seventh chapter focuses on the testing of the previously described theoretical results through the application of Monte Carlo simulations. Through MATLAB simulations providing only the rules and characteristics, guest migration is traced within copolymer populations according to discrete variables, including, but not limited to, comonomer sequence, degree of polymerization, and comonomer feed ratio. The high degree of fidelity between the results of the predictive equations and simulations is noted. The simulations are subsequently used as predictive tools to model guest migration within more complex systems. Finally, guest migration within disperse copolymer populations is modeled via post-processing of the theoretical results. The eighth and ninth chapters conclude the theoretical portion of this work through the derivation of a general limit equation for the determination of migrating guest fractions dependent on the average number of obstacles within the chain. This limit is then advantageously used for the creation of an approximate equation that is useful for the determination of guest migration within alternating, statistical, and imperfect random supramolecular copolymer architectures. These predictive approximations are compared to exact theory, where available, and to simulations where exact theoretical guest migration is not known, i.e., imperfect copolymer architectures. The ninth chapter approximates the extent of guest migration within a bistable switch supramolecular copolymer system. General patterns are observed and noted. The tenth chapter details the synthesis of a bistable [2]rotaxane containing a two-host moiety with a macrocyclic guest whose purpose is to gauge host-site preference as a model for a more complex supramolecular copolymer system. Rationale, synthesis, and experimental observations of this model compound are described herein, with express focus on the relative host site occupancies. The eleventh chapter describes the synthesis and long-term experimental observations of various two-host, one-guest, polypseudorotaxane copolymers formed through ring-opening metathesis polymerization via a ruthenium catalyst. Special focus is given to the extent of conversion in relative host-site occupancy over a three-month-long observation of these copolymer systems. These results are interpolated to the theoretical correspondence of guest migration and copolymer sequence. The sequencing results, using only the theoretical methods, match the known general sequence tendencies provided by the copolymerization technique used. The work is concluded in the twelfth chapter with considerations of possible future directions for this research.