I am working on polycaprolactone (PCL)-protein conjugation. Usually the PCL which is available in market has a hydroxyl group (-OH) group on one of the polymer chain and a carboxylic group (-COOH) on other end of the same. PCL-diols (of low molecular weight) are also available which have 2 terminal hydroxyl groups (-OH). This allows protein conjugation only on one side (-COOH end) of PCL via EDC/NHS chemistry etc. Protein conjugation on both sides of PCL is possible by using PCL-diols (by Maleimide functionalization), however the low Mw of PCL-diols gives inferior mechanical properties as compared to high Mw PCL. Hence, I wanted to procure/synthesize PCL with 2 terminal carboxylic groups. I would like to know if there is an easy chemistry to modify the readily available PCL in market rather than starting from the ring opening polymerization (ROP) of ε-Caprolactone.I really appreciate your help.
the easiest way to synthesize polycaprolactone (PCL) from ring opening polymerization with catalyst.
the ring opening polymerization of caprolactone isthe best method to prepre PCL
Succinic anhydride in help, Srujan - it convert -OH into -COOH, keeping functional uniformity of PCL
Thank you all for your suggestions. Andrei Rogoza I want to use succinic anhydride to convert the -OH group at one of the terminal ends of my PCL (Mw:50kDa). I have come across an article (doi:
10.1155/2014/107375) , where succinnic anhydride, DMAP (4-dimethylaminopyridine, triethylamine have been used to convert PCL-OH into PCL-COOH with 1,4-dioxane as the solvent. The reaction was carried out at room temperature (24 hours) in ambient conditions.
I have come across other articles where the reaction is performed in Nitrogen atmosphere, some even use elevated temperatures like 60 degree C or 120 degree C. Hence, I wanted to ask if I use only succinic anhydride, DMAP with DCM (Dicholromethane) as solvent and carry out the reaction at room temperature (24 hours) without nitrogen atmosphere, would it be ok? And why is the triethylamine added, is it to have high basic environment to extract proton? I really appreciate your help.
I can not comment your specific example - it is science, so any new condition is a new experiment. However, some things are clear :
1) Triethylamine is used as proton acceptor to recycle costly catalyst DMAP. If economy is not obligatory, DMAP alone is not bad as it simplify work-up. N-methylimidazole is less effective in comparison to DMAP but also can work and is readily available.
2) DCM seems to be acceptable in absence of triethylamine.
3) Reaction should be monitored ( by 1H-NMR of -CH2-OH if possible); 24-hrs reaction time in publications is usually indicator of one-point control.
4) Higher reaction temperatures are preferable as reagent must penetrate into statistic coil of polymer. You have realative large molecule ( Mw:50kDa )
5) Nitrogen is not nessesary as no oxygen sensitive functional groups are presented. Water trace (including air moisture) is more critical contaminant in this reaction.
N2 is not best protective gas in common as its molecular mass is less than of the air. Argon is excellent.
Andrei Rogoza Thank you so much for your advice. I really appreciate all your help.
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