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Specialty Chemistry Forums => Materials and Nanochemistry forum => Topic started by: madscientist on November 01, 2007, 05:03:16 PM

Title: 1H NMR and molecular weight
Post by: madscientist on November 01, 2007, 05:03:16 PM

Hi all,

Im trying to figure out a way to calculate a value for the number average molecular weight Mn of a polystyrene sample.  I cant seem to figure out how to make the relation between the presence of functional end groups, i.e the  AIBN initiator used in the polymerisation at one end of the chains and the chlorocarbon formed from the CCl4 transfer agent used at the other end of the chains.  All i can think of is ther must be a way to find the degree of polymerisation Xn from the H NMR spectrum which can be used to calculate Mn.  Can anyone please point me in the right direction.

Cheers,

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Title: Re: 1H NMR and molecular weight
Post by: madscientist on November 02, 2007, 04:02:14 AM

Ahhh, the cerebral lightbulb switches on and the light is shed upon the existence of integral values.

Thanks anyway peoples

Title: Re: 1H NMR and molecular weight
Post by: Mitch on November 02, 2007, 06:39:44 PM

I would of spin coated a glass slide with polystyrene and then taken a UV-Vis. The interference pattern generated is very characteristicly dependent on thickness and can be back calculated to molecular weight: http://www.jce.divched.org/Journal/Issues/2003/Jul/abs806.html