Our current light source for the instrument is a sodium lamp with a 589 nm wavelength filter.The polarimeter operates by directing light through a polarized lens and through the sample cell to quantify how much the molecule in solution rotates the plane-polarized light. NuMega operates a Jasco P-2000 polarimeter for the measurement of optical activity in chiral molecules. If the methyl groups stereochemistry is mixed with no defined pattern in orientation this is called atactic. If the methyl groups alternate every other carbon which side they are oriented this is called syndiotactic. If all the methyl groups are oriented on the same side of polymer this is called isotactic. The stereochemistry of polypropylene groups can also be obtained from carbon NMR with the variations in stereochemistry through differences in chemical shift and number of signals. With clearly defined end groups, you can use the NMR spectra to calculate the average molecular weight of your polymer through the ratios of end groups signals to that from the monomeric and copolymer signals. It is important for polymer NMR to have a clear end group preferably one that does not overlap with peaks of your polymer unit as they are used in analysis for comparison to the monomer. You can use NMR to determine the relative ratio monomers and co-polymers that have been incorporated. NMR can be a useful tool in the characterization of polymers.
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