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Topic: About molecular weight from GPC  (Read 5663 times)

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Offline leeton

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About molecular weight from GPC
« on: September 07, 2009, 09:46:18 AM »
Recently, I prepared some polymer(PSt,PMMA) by RAFT method. But I can not get low PDI products. GPC measurement condition were: THF(GP), 48bar(pressure),1ml/min, standard:PSt(Agilent).

was my experiments failing or GPC results wrong?

I need experts of this field to impress me, thanks!

For further info. you can email me: leetonshao@vip.qq.com ???

Offline marquis

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Re: About molecular weight from GPC
« Reply #1 on: September 08, 2009, 10:37:17 AM »
Please provide more information.  Usually, GPC is done with a bank of columns, sometimes 4 or 5.  You can lower the number of columns if you use a mixed bed column.  What columns did you use? 

What molecular weight are you looking for? Also remember, there can be differences in the estimated molecular weight (by GPC) and the actual value.

Your pressure, flow, and mobile phase look ok. 

Best company I've found for technical assistance on GPC is Waters.  You may want to contact them.


Offline PolymerKnowHow

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Re: About molecular weight from GPC
« Reply #2 on: September 09, 2009, 04:20:25 PM »
Hello Leeton,

I would start with determining the amount of band broadening for your GPC system.
Perhaps the simplest way to test for band broadening would be to inject and analyze one of your narrow polystyrene standards (select a sample which has a molecular weight similar to your experimental samples). Calculate the PDI and compare to what is listed on the packaging.

If the PDI of the narrow standard is much broader than the known value, I would suggest investigating your GPC system further or apply a mathematical correction.

Otherwise, I would suspect your RAFT polymerization is not perfect (which many of them aren't).

Offline PolymerKnowHow

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Re: About molecular weight from GPC
« Reply #3 on: September 09, 2009, 04:29:40 PM »
Best company I've found for technical assistance on GPC is Waters.  You may want to contact them.

I have had many good experiences with PSS, PolymerLabs, and Viscotek. More so than Waters.

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