Objective: The objective of this lab is to become familiar with Nuclear Magnetic Resonance (NMR) technique (polymer analysis, NMR spectroscopy). A background in electromagnetic radiation and Beer-Lambert's Law may prove helpful.

Materials:
Polymethylmethacrylate (PMMA) of 3 tacticities: "atactic", predominantly isotactic, predominantly syndiotactic. Tetramethylsiloxane (TMS), Benzene.

Procedure:

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 PET bottle sample from the DSC experiment will be examined as will samples of PS and other samples.

Analysis:

1. Identify all NMR bands, especially those associated with tacticity in the PMMA samples.
2. From the NMR spectra determine the triad tacticity of the PMMA samples.
3. Identify the polymer for each spectrum. Give detailed analysis with peak identification as well as the number of protons expected for each peak. Does the integrated number of protons for each peak agree with your analysis?
4. Scans 1 and 5 are for the same polymer. Do the spectra differ from each other, if yes, why?    

Questions (some are repeated from last lab but please reanswer with more emphasis on NMR):

1. Explain the working principles and setup for NMR spectroscopy. (A neat sketch of the setup is expected).
2. What is the (n+1) splitting rule for proton NMR? Give 3 examples for polymers.
3. What is the (n+1) splitting rule for proton NMR? Give 3 examples for polymers.
4. Name four isotopes that are NMR active and explain what makes them NMR active?
5. Calculate the magnetogyric ratio for ¹H and ¹³C nuclei (give units).
6. What is proton decoupling in ¹³C NMR? How is it achieved and what are its advantages?
7. 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 NMR. What wavelength of electromagnetic radiation is involved in the two techniques? How do the two types of quantized transition differ in energy for the two techniques?
8. Why is IR data plotted against wavenumber while NMR is plotted against a parameter called the chemical shift? What is the difference between these two parameters and why aren't both of the spectra plotted against wavelength or frequency?
9. What is the purpose of a strong magnetic field in the NMR instrument? Why is a strong magnetic field not necessary in the IR instrument?
10. Explain the meaning of the following words:  meso, racemic, isotactic, syndiotactic, heterotactic, pentad tacticity, atactic.
11. From the literature compare the melting point and glass transition temperature of isotactic, heterotactic and syndiotactic PMMA.