[darkdevil]

Hi,
Here is my problem:
I am doing a polymerization with ATRP with a monomer I synthesized. I tried a series of conditions and most of them gave me low molecular weight polymers (or oligomers). Until last week I setted up a reaction condition that finally gave me a polymer-like product. I quickly analyzed its molecular weight by gel permeation chromatography (GPC) and found out that the polymer had a pretty high polydispersity index (PDI).

Mn :   2388
Mw :   11173
PDI :   4.68

(Monomer:Initiator:CuBr:PMDETA = 1:0.02:0.04:0.04); solvent = toluene; Temperature: 65 degrees celsius; Reaction time: 3 days

The result is quite unsual for ATRP since most ATRP reactions give out polymers with polydispersity near to ~1
I came up a conclusion that my reaction conditions is more like an uncontrolled radical polymerization ( or even worse than a free radical polymerization) . If my assumption is correct, I wonder what shall I do to slow down the rate of radical generation while keeping the polymerization active and "living"? so that I can get a narrower PDI?

Thank you so much!

[darkdevil]

Today I am trying to lower the copper catalyst level so that the whole molar ratios become

Monomer:Initiator:CuBr:PMDETA = 1:0.02:0.02:0.02

This time I am going to react it for 1 day only. I will update the results later

[ATMyller]

I think there's too much catalyst or somekind of air leak or contamination, beacuse those result are appaling for ATRP.

I've done acrylate ATRP polymerations with monomer:initiator:catalyst ratios of 1000:10:1 and I got usually Mn>10000 and PDI<2 after 4 hours at 60^oC.

[darkdevil]

I think there's too much catalyst or somekind of air leak or contamination, beacuse those result are appaling for ATRP.

I've done acrylate ATRP polymerations with monomer:initiator:catalyst ratios of 1000:10:1 and I got usually Mn>10000 and PDI<2 after 4 hours at 60^oC.

In fact, do you think the temperature plays a significant role in the out coming polymer? I tried a 90°C  reaction and most of them failed to obtain a polymer. And this time a 65°C seemed to be an optimum temperature for my monomer

[darkdevil]

I think there's too much catalyst or somekind of air leak or contamination, beacuse those result are appaling for ATRP.

I've done acrylate ATRP polymerations with monomer:initiator:catalyst ratios of 1000:10:1 and I got usually Mn>10000 and PDI<2 after 4 hours at 60^oC.

Can you also show me how did you calculate the PDI ? It seems the method to calculate the distribution curve can lead to very different PDI results.

[ATMyller]

In fact, do you think the temperature plays a significant role in the out coming polymer?

I never tried a very wide temperature range, but it seemed to work pretty much the same between 50 and 70 ^oC.

Can you also show me how did you calculate the PDI ? It seems the method to calculate the distribution curve can lead to very different PDI results.

I used PDI = Mw/Mn, Mw and Mn were calculated by the GPC software.