Plug and play polymers: Diversity through supramolecular chemistry

• Main Author: Ilhan, Ulvi Faysal
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2001
• Subjects: Polymers|Organic chemistry
• Online Access: https://scholarworks.umass.edu/dissertations/AAI3027210

Although supramolecular chemistry is a crucial participant in the formation and ordering of biomacromolecules, it is only recently that it has been utilized in the field of polymer chemistry. Polymers employing non-covalent interactions are becoming important in order to form dynamic and reversible macromolecular systems. To demonstrate the strength and versatility of supramolecular applications in synthetic macromolecules, we grafted recognition dyads as sidechain functionality upon the covalently held backbone. This approach enabled us both to tune material structure and properties and to construct higher order architectures. In our preliminary investigations, we studied a polystyrene-based system that self-assembled through aromatic stacking of electron-rich anthracene sidechains. We demonstrated that the complexation of this polymer with an electron-deficient guest resulted in an enhancement of thermostability to the globular polymer structure, dramatically altering the temperature dependence of polymer unfolding. We then employed azobenzene units as side-chain functionality to obtain a photochemical control over the polymer solution structure. We showed that photoisomerization of the azobenzene groups caused changes in sidechain-sidechain aromatic interactions, resulting in structural modulation of the polymer. Likewise, we grafted varying Donor-Acceptor-Donor hydrogen bonding sidechains to the polymer backbone to obtain more specificity in recognition. We demonstrated that intramolecular association between pendant groups resulted in folding of the polymer into a micelle-like structure in non-polar solvents. We also showed that the efficiency of recognition between the polymer and a complementary monomeric guest can be controlled through the choice of recognition element on the polymer by adjusting the balance between intra- and intermolecular interactions. We then extended the versatility of this “plug and play” strategy to bulk materials. Using spin casting, we kinetically trapped these host-guest complexes in polystyrene films, resulting in highly efficient recognition processes. Furthermore, we demonstrated the encapsulation of an electroactive guest into the intramolecularly hydrogen bonded polymer through NMR and electrochemical studies. Finally, we studied the intermolecular association of our polymers with other macromolecules. We demonstrated a polymer-mediated self-assembly of gold nanoparticles into highly ordered spherical arrays. We then extended this approach to the self-assembly of complementary polymer strands into giant vesicles through specific interchain hydrogen bonding.