1See Tarcha, et al., J. Polym. Sci, Part A, Polym. Chem. 2001, 39, 4189.
Synthesis.
Overall reaction:
1) Determine the amounts of reagents. Use 2.2 equivalents of methacrylic acid (MAA) and triethylamine (TEA) relative to the moles of sebacyl chloride (SbCl) you will be using.
2) Add MAA to a 3-neck round bottom flask (of the appropriate size) fitted with an addition funnel on the center neck and containing a stir bar.
3) Place the set-up on top of a stir plate in a dish that will accommodate an ice bath.
3) Dilute the MAA with approximately 20 times the amount of methylene chloride (MeCl) as MAA (e.g. 30 ml MAA in 600 ml MeCl).
4) Add the TEA, cover the remaining necks with rubber septa, fill the dish with ice and chill the flask for 1 hour, with stirring.
5) Add the SbCl to the addition funnel along with an equal amount of MeCl. Cover the opening with a rubber septa.
6) Add the SbCl to MAA solution dropwise over about 1-2 hours depending on the scale (e.g. 40 g of SbCl should take 2 hours).
7) Once addition is complete, stir for 3 hours while maintaining the ice bath.
Purification.
1) Remove any visible triethylamine-hydrochloride salts via vacuum filtration.
2) Remove any remaining salts by extracting the organic layer with 2 washes of saturated sodium bicarbonate followed by 2 washes with deionized water. The volume of the aqueous layer should be about equal to that of the organic layer (e.g. 600 ml of MeCl = 600 ml of water). This is often easier if you separate large reactions into 2 smaller portions for the extraction steps.
3) Collect (and combine if 2 batches) the organic layer and dry over sodium sulfate.
4) Remove the drying agent via gravity filtration.
5) PRIOR TO ANY FURTHER STEPS - add some type of inhibitor. This will prevent significant oligomerization of the MSA. The monomer itself will be of a honey-like consistency if no oligomerization occurs – the more oligomerization, the more solidified the monomer becomes, potentially complicating usage. Good inhibitors include 2+3-t-butyl-4-methoxy-phenol or if cellular compatibility is desirable, Vitamin D can also be used.
6) After addition of the inhibitor, use a rotovap to remove the MeCl, preferably at 0°C using a strong vacuum to minimize the chances of oligomerization.
7) The MSA can be characterized via NMR using chloroform-d as the solvent. The methacrylation efficiency can be calculated based on the ratio of the integrals for the vinyl resonances to that for those next to the acetate protons. Common %methacrylation = 90-95%.