end groups, there have been many analytical techniques developed for the identification of the groups. The three main methods for analyzing the identity of the end group are by NMR, mass spectrometry (MS) or vibrational spectroscopy (IR or Raman). Each technique has its advantages and disadvantages, which are details below. NMR spectroscopy The advantage of NMR for end groups is that it allows for not only the identification of the end group units, but also allows for the quantification of the number-average length of the polymer. End-group analysis with NMR requires that the polymer be soluble in organic or aqueous solvents. Additionally, the signal on the end-group must be visible as a distinct spectral frequency, i.e. it must not overlap with other signals. As molecular weight increases, the width of the spectral peaks also increase. As a result of this, methods which rely on resolution of the end-group signal are mostly used for polymers of low molecular weight (roughly less than 20,000 g/mol number-average molecular weight). By using the information obtained from the integration of a 1H NMR spectrum, the degree of polymerization (Xn) can be calculated. With knowledge of the identity of the end groups/repeat unit and the number of protons contained on each, the Xn can then be calculated. For this example above, once the 1H NMR has been integrated and the values have been normalized to 1, the degree of polymerization is calculated by simply dividing the normalized value for the repeat unit by the number of protons continued in the repeat unit. For this case, Xn = n = 100/2, and therefore Xn = 50, or there are 50 repeat units in this monomer. Mass spectrometry Mass spectrometry (MS) is helpful for the determination of the molecular weight of the polymer, structure of the polymer, etc. Although chemists utilize many kinds of MS, the two that are used most typically are matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) and electrospray ionization-mass spectroscopy (ESI-MS). One of the biggest disadvantages of this technique is that much like NMR spectroscopy the polymers have to be soluble in some organic solvent. An advantage of using MALDI is that it provides the simpler data to interpret for end group identification compared with ESI, but a disadvantage is that the ionization can be rather hard and as a result some end groups do not remain intact for analysis. Because of the harsh