Thank you. But I want to produce low molecular weight, soluble P(HEMA). Do you think chain transfer agents work in aqueous synthesis medium?

At 70 C it gelled.. Which temperature do you advice?

The gelling you observed could be due to both the "Trommsdorff effect" and the small amount of di-methacrylate you normally find in HEMA.

Add a transfer agent to reduce the "Trommsdorff gelling", or better yet control the polymerisation via RAFT or ATRP.

Distil the monomer under reduced pressure to remove some of the di-methacrylate. Or if you require only a small amount, try and separate on a chromatography column.

Thank you, that helps a lot.