Polymer brushes are used often for sensing devices, membranes, or as drug delivery vehicles. Characteristics such as brush thickness and pKa dictate polymer brush performance and functionality. These properties are currently determined mainly using in situ ellipsometry techniques, which require lengthy equilibration periods, meaning analysis times as long as days are often necessary to cover a wide pH range with high resolution. We will demonstrate the advantages of silicon photonic microring resonators, a refractive index-sensitive technique that monitors changes in local environments at the sensor surface, as a faster method to determine brush properties. To assess the platform’s performance, pH-sensitive (poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA), poly(acrylic acid) (PAA)) and non-pH sensitive (poly(methyl methacrylate) (pMMA), poly(2-hydroxylethyl methacrylate) (pHEMA)) polymers were grown to various thicknesses on silicon-on-insulator microring resonators using SI-ATRP. Polymer dynamics were measured in response to both pH and solvent deuteration changes. Relevant pKas for polymers were determined with a precision of 0.3 pH units in a period of 4 hours and deuterated solvent comparisons were used to determine brush thicknesses. These results demonstrate that microring resonators could be used as a tool for rapid determination of polymer properties.

Characterization of polymer brush properties using silicon photonic microring resonators

255th National Meeting (2018)

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