Ionic liquids (ILs) are organic salts that are liquid at or near room temperature (i.e. below 100 ◦C). They possess unique materials and solvent properties that have led to their use in multiple applications. Poly(ionic liquids) (PILs) refer to a special type of polyelectrolyte that carries an IL species in each of the polymer repeating units. PILs offer advantages over ILs in enhanced mechanical stability, and improved processability, durability and spatial control over the IL moieties. The ability to generate surface-tethered polymer films with IL functionality as side chains can enable coatings with versatile and tailorable properties. This dissertation describes the preparation and characterization of surface-polymerized ILs.
Surface-tethered poly(ionic liquid) (PIL) films were prepared via surface-initiated ring-opening metathesis polymerization (SI-ROMP) of ionic liquid-tethered monomers on gold, silicon, and glass substrates and were shown to be adaptive to their anionic environment. A simple anion exchange of PIL films with aqueous solutions containing a binary mixture anions led to the formation of random copolymer PIL films, that offered a continuous tuning of film properties between the extremes of the two homopolymers incorporating the anions present in the copolymer films. For surface-tethered PIL films on gold substrates, anion exchange with certain anions such as triflate, led to the desorption of the PIL films from the surface due to entropic effects and an increase in the glass transition temperature of the films.
Part of the dissertation examines polydicyclopentadiene (pDCPD), which is a rigid, cross-linked polymer with excellent impact strength, high modulus, and high chemical resistance. Commercially used for automotive panels and sporting goods, pDCPD has been experimentally explored for a broad range of applications including ballistic protection. While bulk pDCPD has broad commercial impact, the ability to prepare surface-immobilized polymer films of pDCPD, especially with minimal environmental impact, could lead to tough, impact- resistant surfaces with numerous applications. Surface-tethered pDCPD films were prepared on gold and silicon substrates via a novel SI-ROMP with monomer in the vapor space. The choice of ROMP catalyst was an important factor when SI-ROMP was conducted on different substrates.