Chemical vapor deposition of functionalized isobenzofuran polymers

Abstract

This thesis develops a platform for deposition of polymer thin films that can be further tailored by chemical surface modification. First, we explore chemical vapor deposition of functionalized isobenzofuran films using two different functional groups: pentafluorophenolate ester and alkyne. Both functional groups can be further modified using either ester substitution or click chemistry, respectively. The resulting thin films are characterized extensively using nuclear magnetic resonance (NMR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). We show that the functional groups remain on the surface post deposition for both films at cracking temperature not exceeding 6000C. However, gel permeation chromatography(GPC) measurements of the pentafluorophenolate ester films show only marginal polymerization. On the other hand, the alkyne films appear crosslinked and showed defect formation. Films deposited at ambient temperature show formation of a large number of micro defects. Increasing the deposition temperature, in addition to increasing the growth rate, also leads to formation of films with two distinct domains: one smooth domain with no micro defects and another filled with defects.

(cont.) Analogous to the deposition of unmodified isobenzofuran films, the films with alkyne moiety have a high refractive index and are transparent in the visible and near IR range. Second, we explore coating of poly(dimethyl siloxane) (PDMS) microfluidic devices with poly(glycidyl methacrylate) (PGMA) thin films using initiated hot filament chemical vapor deposition. We demonstrate a use of a new ultra violet (UV) initiated bonding method that allows PGMA coated PDMS devices to be sealed to PGMA coated glass, while maintaining the integrity of the majority of surface functional groups. This approach allowed us to further functionalize the channel walls with hexamethylene diamine (HMDA) and poly(ethylene glycol) (PEG)-bis(amine) to make a lasting hydrophilic surface. Bonding of devices proved to be stable up to 2 bar.