This presentation describes the preparation of organic thin films generated from N-heterocyclic carbenes (NHCs) possessing an azo initiator group designed for surface-tethered polymer growth from gold surfaces. Given that NHCs form strong C–Au bonds between the headgroup of the adsorbate molecules and gold atoms, we explored this approach in an effort to overcome stability issues that plague related thiol-based initiators. The generation of NHC self-assembled monolayers (SAMs) typically requires a strong base and inert atmosphere, which limits the functional utility of such films. To overcome these limitations, we initially explored the use of adsorbates possessing benzimidazolium hydrogen carbonate headgroups. However, this approach led to serious contamination by iodide, which significantly diminished the film quality. We then explored the use of adsorbates possessing benzimidazolium methanesulfonate headgroups, which not only allowed the direct formation of NHC films under ambient atmosphere, but also provided a new pathway for adsorbate variability and surface functionalization. The new SAMs were characterized by various surface techniques including ellipsometry, polymerization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), X-ray photoelectron spectroscopy (XPS), and contact angle goniometry. To evaluate the potential of the new radical initiator films as surface-initiated polymerization platforms, polystyrene films were grown from radical-initiator monolayers generated from azo-terminated NHC adsorbates.

Functionalized N-heterocyclic carbene monolayers on gold for surface-initiated polymerizations

ACS Fall 2021

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