Dear all:I just synthesized a polymer. The integrations in the high-chemical-shift regime areconsistent with theoretical values, with error less than 5%. The integrations in thelow-chemical-shift regime corresponding to alkyl chains (delta=0.8-1.8 ppm), however,are greater than theoretical value by 30%. I'm pretty sure this is the polymer I want because elemental analysis is also good, but just can't figure out why integrations are off by so much. The possible solvent peaks there are hexanes and water, but I've had it vacuum dried for a week at 80 C and no such peaks were observed.I heard that the ratio of alkyl NMR integrations are usually higher than expected compared to thearomatic region due to longer relaxation times for aromatics. If so, how do I circumvent this issue? Increase scan time or delay time? I also notice there is something like "shoulder" for this alkyl region as in the spec http://imageshack.us/photo/my-images/863/nmr.png/. Does it look like I didn't a good job on baseline?Thank you very much for your kind help.
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H NMR integraton
Linear Mode
