Objective: The objective of this lab is to become familiar with spectroscopic analytic techniques used in polymer analysis specifically IR and Raman spectroscopy. A background in electromagnetic radiation and Beer-Lambert's Law may prove helpful. The most common techniques are IR spectroscopy from solutions and films and proton NMR from polymer solutions.

We will run IR and Raman this week.

Materials:
Polymers that are available such as Polymethylmethacrylate (PMMA) of 3 tacticities: "atactic", predominantly isotactic, predominantly syndiotactic.  Polybutadiene of variable cis and trans content (from golf ball and super ball), nylon, polystyrene, PET, polycarbonate, other polymers.

Procedure:

There are several ways to make samples for IR/Raman.  Genarally solid samples can be used.  In order to avoid burnout of the samples we grind the Raman samples to a powder and put them in NMR tubes as a dry powder. 

You can bring your samples from the reverse engineering lab to this lab for characterization.

1. 5% solutions of the PMMA samples with a trace amount of TMS (0.1%) in d-chloroform will be used to obtain proton NMR spectra.
2. The same samples will be examined using transmission IR from cast films and in KBR pellets.
3. Thin films of h-chloroform solutions will be cast on surfaces for attenuated total reflection IR measurements.
4. Thin solid sheets of the PMMA samples will be made by hot pressing small amounts of the samples in a Carver Press. These will be examined using transmission IR.
5. Make KBr pellets from ground PMMA samples and examine using Transmission IR.
6. The PET bottle sample from the DSC experiment will be examined as will samples of HIPS and other samples.

Analysis:

1. Identify as many bands as possible in the IR spectra using group contribution methods.
2. From the IR spectra determine the triad tacticity of the PMMA samples.
3. Compare the IR spectra obtained by ATIR, Transmission IR from films, Transmission IR from the solutions, transmission IR from KBr pellets (if these were run).
4. Do the same for the Raman spectra.
5. Compare the Raman and IR spectra for the poybutadiene samples and determine the cis and trans content for these samples. 
   

Questions:

1. Compare the information that was obtained from Raman with that obtained from IR in the determination of tacticity and chemical composition.
2. Compare the cost and complexity of the two measurements and the flexibility of the sample preparation.
3. Why might you want to know the triad tacticity of a polymer?
4. What is the group contribution method for IR/Raman and why is it advantageous for polymeric systems?
5. Spectroscopic techniques generally rely on the presence of a quantized transition which leads to a narrow band of absorption of electromagnetic radiation. What quantized transition exists in IR and in Raman? What wavelength of electromagnetic radiation is involved in the two techniques? How do the two types of quantized transitions differ in energy for the two techniques?
6. Why is IR data plotted against wavenumber?
   
7. Why was PMMA chosen for this experiment?
8. If your sample contained water and you want to ignore this background would you use Raman or IR spectroscopy?  Why?
9. Please add the quiz questions to the text of your writeup.