Khushna, your second option is the correct one, flush/ purge the system.

You need to use a round-bottomed flask with few necks. To one neck , attach a rubber piece similar to the big top of a dropper & it must fit tightly & properly. Insert a sharp needle-like glass tube which penetrates the rubber without itself breaking or tearing the rubber apart. Connect the glass to nitrogen cylinder & let N2 flow at moderate rate over the polymerization system. All this is about the inlet, but you need an outlet from which the undesired gases pass outside by the flush of nitrogen. Within few minutes, the nitrogen forms a good blanket. I used to do this during the preparation of Grignard reagents & each time it was a successful way & reduced the need for excess diethyl ether.

The answer to your question depends on the volatility of the components in your system. Basically your reaction vessel has to have an inlet and outlet. As the inlet a needle passing through a septum can be used. As the outlet a relux condensor with a T-junction at the top can be used, Before starting the poymerisation pass the nitrogen first through a wash bottle containing a small amount of the reaction mixture and then through the needle into the polymerisation vessel. After bubbling for about 20 minutes at a moderate flow, switch the gas flow to pass over the top of the condensor through the T-junction for the duration of the polymerisation. In this way, loss of volatile componants is avoided. The outlet from the T-junctions should have a rubber tube dipped into a beaker containing glycerol to prevent back-diffusion of air into the system. If you need more details, contact me

Thank you for oppinion. Two days ago, i have tried flushing just for 10 minutes before i take on my microwave to synthesis. I set temperature at 170 celcius but it has increase suddenly until 195 celsius. I think that nitrogen gas has function for mantain polimerization temperature.

Nitrogen gas does not keep the temperature of a polymerization system constant but it just acts as a blanket to protect the process from e.g. oxygen & moisture. The increase in temperature, which you observed, means that the polymerization is an exothermic process. If the rise in temperature is not desired, then the round-bottomed flask of the set-up ought to be placed inside a thermostated basin.

But, did increase temperature of polymerization process can make polymer is degradated?

So that, i have to keep temperature properly.

Dr. Khusna,

An increase in temperature during polymerization may lead to various possibilities,e.g. depolymerization which means going back to monomer(s), thermal degradation if the polymerization is highly exothermic "like the so-called popcorn polymerization", and undesired side reactions which give simpler organic compounds instead of polymeric product.

Dear Dr. Nizar,

Thank you for information. I have tried it and i think my polymer is synthezied. But, it has low DPn (Degree of polimerization) and weight. is it caused of microwave energy?

Dear All;

additional precaution should be fullfield if it is to work under the absence of moisture. Nitrogen gas usually contains a high level of moisture, so it must be dehydrated prior to its introduction into the reaction vessel, this is easily and efficiently done by passing the gas current in a solution of concentrated H2SO4 in an Erlen-Meyer glassware to trap the moisture.

As Dr. Aziz said, dry nitrogen is used actually. The low degree of polymerization could be attributed to an increase of temperature when the type of polymerization is addition or chain-reaction. Addition polymerization requires an initiator ; if the amount of initiator is increased, the DP will decrease, i.e. the molecular mass will be lower than what is desired.The microwave heat energy may be a reason but this needs verification by thorough experimental work.

Hello.

My opinion is purging the nitrogen into your solution. Since you want to synthesize, you need to prevent any oxygen inside which can disturb radical reaction

In your outlet, put BUBBLER (contain silicone oil inside) to make nitrogen going out and prevent any gas outside esp oxygen flowing in into your vessel

Thank you for advice, sir.

I will try to synthesis polyethersulfone by purging the nitrogen until the end of time optimized. I am doing polymerisation condensation with dean stark trap system .

Dear Dr. Khusna;

a Dean-Stark setup operates well under a good choice of the azeotrop solvent for an efficient take-off of water molecules by an azeotropic distillation. If the water is not efficientl removed the reversibility of the polycondensation reaction is more likely to occurs, and this may be another probable reason behind the low degree of polymerization (low molecular weight).

The extent of sensitivity of your polymerization system to humidity or oxygen is the important factor to your decision to make purging by nitrogen prior to polymerization or to continue passing nitrogen during polymerization process up to the end of reaction time. Also the need to dry nitrogen gas before flushing process is related also to the sensitivity of the polymerization process to humidity or oxygen. For highly sensitive polymerization processes then working under vacuum is the best choice as in the case of coordination polymerization to make sure you will get reproducible results.

You don't describe the polymerisation system, which makes a difference. However one should note that be continually purging the solution you are constantly introducing fresh impurities, especially if you haven't purified your nitrogen.

I'd highly recommend reading Shriver and Drezdzon, which someone has put online here: http://www.halbmikrotechnik.de/big/literatur/Shriver,%20The%20Manipulation%20of%20Air-Sensitive%20Compounds.pdf

• Sorry, too late. Thank you. I have tried to use nitroger purified. It is more better.