I'm trying to make a PLGA copolymer via melt polymerization and a lot of the literature suggests performing the reaction under vacuum but the exact directions are unclear.
Dear Sir,
sometimes an ordinary pressure glassware is enough, but better if a Shlank setup is available. Regards
I make a lot of experiments under vacuum in the past (see my papers on anionic polymerisation). The main advantage is to be sure not to have oxygen and moisture in the vessel (N2 can be successsful but Argon is usually preferred to inert a vessel), a second advantage is the possibility to transfer volatil solvents (THF, toluene, etc) by cold distillation directly in the vessel. The simple way is to use rotaflo (teflon taps),(it is not necessary to put lubricant and the best quality (red one) keep 10-5 mm Hg). The vacuum is usually performed by a primary and secondary pump to get 10-6 mm Hg.The addition of chemicals or solvents can be performed by pyrex tubes blowed on the pyrex baloon (reactor) and finished by rubber or silicone stoppers (rabatable) to inject chemicals with a seringue.
If necessary, to improve again the quality of the vacuum it is possible not to use rotaflos but to seal directly the ballon of the pump, and to add chemicals by breakseals and solvents by cold distillation. This was necessary in my case as we were needing an excellent vacuum to quantify alkali metals and alkyl lithim derivatives.
Inert atmosphere is also a condition of relevance when one of your reagents has a low flashpoint, and even at that argon would be preferred over nitrogen in some cases.
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