Poly(acrylic acid) (PAAc) is a commonly used polymer grafted on poly(ethylene terephthalate) films for the immobilization of bioactive molecules that directly interact with living cells or tissues for the maintenance of their viability and functionality. The diffusion property of the grafted PAAc on the surface is a critical parameter related to the density, length of polymer chains, and ionic strength of the solution. Fluorescence correlation spectroscopy (FCS) is able to measure the diffusion coefficient of fluorescent particles in solution with single molecule sensitivity and specificity. It was used as an effective tool to detect diffusion dynamics of Atto 565 molecules, a good indicator for viscosity of PAAc, in both aqueous polymer solutions and polymer grafted film surfaces immersed in solution. In this work we determine the polymer chain length under different polymerization conditions in solution and deduce the solution viscosity by FCS measurements of Atto 565 as tracer molecule. By using the same tracer on the grafted polymer films we can infer the viscosity of these grafted layers under a variety of conditions, including the PAAc chain length, the UV exposure time during polymerization, the ionic strength, and the pH value of the immersed solution.
Advanced processing and analysis of conventional confocal microscopy generated scanning FCS data
