Polymer brushes form an important class of polymers, as they are extensively used as functional coatings. They confer various properties to surfaces like lubrication, corrosion resistance, anti-fouling properties, stimulus-responsive properties, surface wetting properties, and colloidal stabilization. With its diversity in function, the incentive for improving the method for its synthesis is crucial for its widespread industrial application. In this study, we investigate the use of a light-mediated polymerization process for the efficient production of a polymer brush. We use methyl methacrylate as a model monomer and generate the brush on silicon. We utilized sum frequency generation (SFG) spectroscopy, atomic force microscopy (AFM), ellipsometry, and contact angle goniometry to assess the surface characteristics of the resulting product. Preliminary data for the SFG spectrum showed peaks at 2883 cm<sup>-1</sup> and 2942 cm<sup>-1</sup> for the SSP polarization combination  that is attributed to ester methyl harmonic or fermi-related vibrations. Ellipsometry and contact angle measurements showed the formation of 15.5-22.2 nm thick brushes with contact angle values ranging from 69°-85° when the reaction time is varied between 1-5 hours. The AFM images showed a uniform and relatively flat surface with an RMS value of 1.9-3.5 nm. With this work, it was shown that it is possible to grow polymer brushes on silicon in the absence of a free radical initiator or catalyst and in a solvent-free environment using 385 nm light to initiate the polymerization process.

Catalyst-free and solvent-free light-mediated polymerization of brushes characterized by SFG spectroscopy

ACS Spring 2022

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