Spin-Coating of Polystyrene Thin Films as an Advanced Undergraduate Experiment

A simpler version of the well-established technique of spin-coating thin polymer films on glass slides is described. Starting with simple instrumentation and using an ordinary, commercially available cooling fan (a "CPU cooler"), a method of spin-coating an expanded polystyrene foam on glass slides is described. Making thin films of commercially available polystyrene on glass slides is also included for comparison. An interferometric technique is used to measure the film thickness employing a UV–vis spectrophotometer. FTIR spectroscopy is used to verify the identity of the polymer on the glass slide. Using the Beer–Lambert law of absorbance, the film thickness is also calculated from the FTIR spectra of films. A comparison is made between the interferometric and FTIR methods for thickness measurements. An organic dye is doped into a film and a UV–vis spectrum is used to identify the dye.