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Topic: 0.05 wt% of polymer  (Read 2911 times)

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Offline redhat0904

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0.05 wt% of polymer
« on: July 24, 2016, 06:01:47 AM »
Hey,

I am sorry if this question is too easy!

0.04 mol of a polymer (MW: 1000 g/mol) is reacted with B at 150 C in nitrogen atmosphere for several hours using catalyst (0.05 wt% of polymer)

My question is, how do you calculate 0.05 wt% of polymer so I know how much cat I need? Using the internet, I got an answer of 0.02 g but I am not sure if this is right!

Also, what is the best way to achieve nitrogen atmosphere? Would I need a reflux condenser? B is not a solvent, it is another reactant. Would I need mineral oil? Or a schlenk line?

Many thanks!

Offline AWK

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Re: 0.05 wt% of polymer
« Reply #1 on: July 24, 2016, 07:23:44 AM »
0.02 g is OK
Organic compounds at 150 C may decompose, undergo oxidation, even ignition.
Sometimes nitrogen may be insufficient. But author of this procedure probably tested it.
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Offline Arkcon

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Re: 0.05 wt% of polymer
« Reply #2 on: July 24, 2016, 07:49:30 AM »
Hey,

I am sorry if this question is too easy!

0.04 mol of a polymer (MW: 1000 g/mol) is reacted with B at 150 C in nitrogen atmosphere for several hours using catalyst (0.05 wt% of polymer)

My question is, how do you calculate 0.05 wt% of polymer so I know how much cat I need? Using the internet, I got an answer of 0.02 g but I am not sure if this is right!

Like AWK: said, good job.  Now, determine how much catalyst you need.

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Also, what is the best way to achieve nitrogen atmosphere?

You can use the in-house nitrogen, or purchase a cylinder.  Ask whoever handles that at the institution you're at to handle that for you.  Those are the best ways.

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Would I need a reflux condenser?


Probably a good idea, but check the protocol.  Grab on of those anyway from the institution store room, or requisition it, if those are the rules at the institution in question.

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B is not a solvent, it is another reactant.


Interesting.  Well, you can tell if it is present in a great stoichiometric excess, then its solvent and reactant, or maybe the protocol calls for solvent.  Check by confirming the stoiciometry.
Ask an expert at your institution, you'll be using their lab, so they wouldn't want an accident. 

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Would I need mineral oil?


For ... ?

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Or a schlenk line?

Interesting.  You haven't told us what the reaction is, so we can't really say.  Why do you think you might need a vacuum and inert gas purging manifold, instead of a reflux condensor?  What is the difference in function between the two?  And why would you pick one over the other?

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Many thanks!

No problem, we're glad to help.  ...

...

... You're uh, ... not affiliated with a university or industrial lab, are you?  That's OK, we're glad to help anyone.  Give us some more information, to let us know that you know enough to not hurt yourself, and we'll give you some more tips.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline redhat0904

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Re: 0.05 wt% of polymer
« Reply #3 on: July 25, 2016, 07:02:08 AM »
So I calculated I needed 0.02g of cat.

Yep, so the techinician bought a cylinder, and I believe he connected it to the taps. So i will use that as my source!

Unfortunately there isn't much of a protocol :( just relying on a thesis. All it says is use a 250 mL one-neck round-bottom flask equipped with a magnetic stirrer. Because I am heating at 150 C, even though I am have no solvent, I thought having a reflex is good just as a precaution? Though I am not sure how to connect the nitrogen to it. I was thinking: Having a two/three-neck round-bottom flask, reflux condenser and at the top, one tubing going the nitogren tap..I know I can't have a closed system, so I was thinking connecting a bubbler (with mineral oil), or leaving on of the side neck of the flask open (would this affect my reaction), or adding a septa on one of the neck and a sringe?

I do believe my reactant B is in excess.

I am sorry! My reaction is between poly propylene glycol and lactide to make poly propylene glycol -co-lactide. The cat is stannous octoate, which is sensitive to air. The reaction is left for 6 hours. (Please don't quote this in cause I need to remove this information later on!) Many thanks!


Thank you so much AWK and Arkcon - I really appreciate this!

Offline AWK

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Re: 0.05 wt% of polymer
« Reply #4 on: July 25, 2016, 10:09:23 AM »
PLLA-PPG-PLLA copolymer is known ~30 years (Concise Polymeric Materials Encyclopedia  - see Google books). Your catalyst is used as 3 % toluene dispersion, so you have an additional problem. Working under reduced pressure in anhydrous condition under nitrogen or argon is now a standard procedure.

Preparation of block copoly(ester-ether) comprising poly(l-lactide) and poly(oxypropylene) and degradation of its fibre in vitro and in vivo
Yoshiharu Kimura, Yuji Matsuzaki, Hideki Yamane, Toshio Kitao
Polymer 30(7) 1342-1349 (1989)

Synthesis and Characterization of Novel Biodegradable
Triblock Copolymers from L-Lactide, Glycolide, and PPG
S. M. F. FARNIA, J. MOHAMMADI-ROVSHANDEH, M. N. SARBOLOUKI
Journal of Applied Polymer Science,  (73), 633–637 (1999)
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Offline redhat0904

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Re: 0.05 wt% of polymer
« Reply #5 on: July 25, 2016, 10:56:36 AM »
So i am synthesising PGLA-DMA (poly (propylene glycol -co- lactide) dimethacrylate in two steps..my main issue is setting up a nitrogen atmosphere at that temperature and for that long when ..fortunately my cat isn't in toulene

I will post a picture of my set-up later

Also is this a good equation for the cataylst weight, which is 0.05 wt% of polymer (polymer weight is 40g)
x = weight of cat.

xg/40g = 0.05/100

Offline AWK

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Re: 0.05 wt% of polymer
« Reply #6 on: July 25, 2016, 11:06:45 AM »
In procedure (ref2) pressure 100 mmHg was used (the same time and temperature).
AWK

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