[Rodolfo Minto de Moraes]

I’ve been tried to perform the esterification between PNVCL-COOH (PNVCL-S-CH2-CH2-COOH) and PCL-OH homopolymers using DCC and DMAP in DCM, DMF or THF at 0 ° C, room temperature or 50 ° C. I’ve been used the following ratios [PCL-OH]: [DMAP]: [PNVCL]: [DCC] = 1: 0.2: 3: 3.3, 1: 1.5: 3: 3.3 and 1: 0.2: 3: 9. The reagents are dry, except for the DCC that has traces of water (by NMR). After reaction I purified the product in ether and the retreat PNVCL chains (hydrophilic) unreacted by centrifugation in water. I have tried to confirm and quantify the esterification by disappearance / displacement of the methylene protons peak of PCL-OH (-CH2-CH2-OH. However, It’s disappears entirely, but there is no PNVCL peaks in the product NMR spectrum. Therefore, the materials not engaged and some unwanted reaction is happening with the hydroxyl group of the PCL-OH. Does anyone have any suggestions of the possible problem and how to fix it? The reaction is possible between DCC, CDI, DMAP, or NHS and the amide of the poly (N-vinylcaprolactam)?

[TheUnassuming]

Just want to double check my understanding.  You see your alcohol disappear from the reaction, but no ester formation?

How are you monitoring the reaction?

What base are you using? 

As a general rule I use minimum 3 equiv of carbodiimide per acid equiv. and usually 2 equiv of the alcohol.  Add in about 0.1 equiv of catalyst like DMAP and some base (NEt3 common) to start the reaction/mop up the acid formed and you should be good to go.