GPC of latex emulsion

[alambic]

I'm developping a method to analyze latex emulsion by GPC. At this time, the best way I can dissolve the latex is by adding a small amount of water to the emulsion to lower the solids and then adding THF to have about 1% solid content in the THF solution. My feeling is that the polymer isn't completely dissolve because my 0.45 micron filter become clogged. I've tried to lower the concentration but I see almost nothing on GPC. I've tried also to dissolve dry latex directly in THF but it doesn't work even when warming the solution. Our latex emulsion are mainly styrene-acrylic copolymers, vinyl acrylic copolymers, 100% acrylic polymers and vinyl acetate polymers. I want advice on how to analyze these latex emulsion on GPC.

[Rafael Chust]

When you say warming, how warm is it? 50º, 100º, 150º?

There are several solvents you can use, such as toluene, chlorophorm, benzene, DMF, DMSO, methylene chloride, ethyl ether, etc.

I believe your stuff should be dissolved in any of these!

Good luck!

[alambic]

The dissolvation temperature is about 50 Celcius. I've already tried before in toluene and DMF with no success, even over a week-end.

[Rafael Chust]

I did some GPC work in the past and used to dissolve over 100º in THF, for at least 3 minutes.

Give it a try!

[alambic]

How can you warm your THF at 100 celcius when the bp of THF is 66 Celcius??? Also it's not dangerous to degrade polymer at these temperature especially with high MW polymer?

[Rafael Chust]

Well, THF bubbles... so what? When you cook meat, the water boils too...

What is the temp fo your column oven?

Polymer can degrade, although 100º is too low for extensive degradation.

Anyway, you must validate your methiod with standards to see how it goes...

[alambic]

My GPC is running with THF at 40 Celcius

[Uwe Neue]

Your concentration is rather high for GPC. The general recommendations are under 0.1%, or even 5x lower for higher MW stuff.

The signal depends on the injected amount, which is a combination of concentration and injection volume. The common practice would be to inject a larger volume rahter than increase the concentration.

Also, it takes time and patience to dissolve a polymer.

Your solvents and the temperature are right on the money. What columns are you using?

[alambic]

Like I said before, I've tried lower concentration injection but I have almost no signal. My injection volume is 20 µL. So, it would be better if my injection volume was 100 µL. I had to change my injection loop. The columns I use are Waters Styragel 7.8 x 300, an HR5 and HR4.

[Uwe Neue]

Yes, absolutely change the injection loop. In standard GPC with these large diameter columns, 100 microliter is normal.

[alambic]

I have only a 200 µL loop in spare. Do you think it's a good idea to use this loop but inject smaller volume like maybe 100 µL?

[Uwe Neue]

I would first inject the 200 microL, and reduce the volume with a partial loop injection if needed.

[alambic]

I tried heating my styrene-acrylic latex emulsion with boiling THF to dissolve it but doesn't work even after few hours. My concentration is 0.05%. I see that it dissolve partially but I can see a lot of gel. I will try with other solvent.

[alambic]

I was finally able to dissolve my polymer in hot DMF. The solution is easy to filter too. I have now to switch my eluent on my GPC system from THF to DMF.

[PEA]

My GPC is routinely on DMAC/.1% LiCl at 60C. This system is very powerful to dissolve most of the polymers. If u switch from THF to DMF, you need to switch columns too.