(Last Revision: January 31, 1997)
A source of polystyrene foam is dissolved in a solvent and then cast on a glass plate. The resulting film is mounted on cardboard and an IR spectrum recorded. The recorded spectrum is then compared to a library spectrum.
Atkins, "Physical Chemistry", 5th edition, 1994. Chapter 16
Polystyrene is readily soluble in a number of common solvents and can easily be cast as a film by pouring the polymer solution onto a glass plate and letting the solvent evaporate. Polystyrene films give a very good IR spectrum, which is often used as a standard.
The equipment used for this experiment includes beakers, test tubes, glass plate,and a Fourier Transform IR Spectrometer
Polystyrene foam, toluene or acetone are used in the experiment.
About a gram of polystyrene should be broken into small pieces and placed into a test tube or beaker. Then enough solvent should be added to prepare about a 20% solution ( use about 4 to 5 ml ). The mixture should be stirred until the polymer is completely dissolved.
The film is cast by pouring the viscous solution near the edge of a glass plate. It may be spread out and smoothed with a single pass of a knife ( one pass only). Allow the film to dry slowly; it may take an hour or so.
The film is removed by applying pressure with a spatula or razor blade at edges of the film. Then mount the film in a cardboard holder and place in the IR instrument.
A spectrum should be taken of the film and spectral library used to identify the components in the film.
As directed in the laboratory.
Standard spectra are included in the spectral library which is accessed through the computer attached to the spectrometer.