See http://www.fda.gov/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/ucm091048.htm

I will refer you to read following articles for your above stated quiery

http://www.polysciences.com/pdfs/4%20page%20mp_polyfact_web%20R1.pdf

https://books.google.com.pk/books?id=q2LZ6CwkOUgC&pg=PA959&lpg=PA959&dq=US-Food+and+Drug+Administration+(US-FDA)+approved+hydrogels+and+monomers&source=bl&ots=aB11GPLTDk&sig=8GQZVB7t_m5MyA2wo0rMzsih4mw&hl=en&sa=X&ved=0ahUKEwih6pSisPLLAhXkIaYKHeBpBnAQ6AEIIzAC#v=onepage&q=US-Food%20and%20Drug%20Administration%20(US-FDA)%20approved%20hydrogels%20and%20monomers&f=false

https://books.google.com.pk/books?id=yq5_QfbP8HQC&pg=PA363&lpg=PA363&dq=US-Food+and+Drug+Administration+(US-FDA)+approved+hydrogels+and+monomers&source=bl&ots=auQyyxWS1c&sig=QvAICIXx4fS8jDz4QiU0sCpAqiQ&hl=en&sa=X&ved=0ahUKEwih6pSisPLLAhXkIaYKHeBpBnAQ6AEIHDAA#v=onepage&q=US-Food%20and%20Drug%20Administration%20(US-FDA)%20approved%20hydrogels%20and%20monomers&f=false

Thank you very much for your responses