Premature crosslinking during methacrylation of poly(glycerol sebacate) is likely due to residual reactive groups and reaction conditions promoting unwanted condensation or radical reactions. Although 4-methoxyphenol and TEA help inhibit this, controlling temperature, time, and atmosphere is essential to prevent early crosslinking.

Thank you for your suggestion.

1.I was methacrylating for 24 h but planned to reduce it for 12h.

2. I used nitrogen gas flow before but skipping it as it negatively effect MEHQ inhibitors.

What reagent were you using? methacryloyl chloride? anhydride?

reagent ratio?

Steven D. Smith I am using methacrylic anhydride at a 3:10 weight ratio relative to the polymer.

Depending on polymer molecular weight that seems like a good excess of anydride. I think it is also possible that the anydride is reaction with the phenol group of your inhibitor to form an ester linkage - thereby consuming your inhibitor. Possibly try Copper as an inhibitor? Or TEMPO?

@Steven D. Smith Thank you for your suggestion. The amount of the MA is based on the fact that " 1g Poly Glycerol Sebacate would have 3.9 mmol OH group available to be reacted with MA''. I added 0.5 mol MA of the of the available OH groups of my calculated weight of polymer.

Reduce to a minimum MMA concentration

When I used 0.21 mol MA/ mol OH, the polymer was not UV curable.

Steven D. Smith Can I use DMAP instead of TEMPO?

DMAP may act to catlayze the reaction but I am not sure that it would act as an efficient antioxidant. Copper powder or particles would act an an inhibitor. I have used it in the reaction of allyl methacrylate with diemthyl hydro chlorosilane. Which would polymerize every time when using a phenolic inhibitor. I assume the chlorosilane was reacting with the phenolic. Copper inhibits the polymerization reaction- by reacting to form Cu+1 species.?

Thank you Steven D. Smith for your insights.