Abstract: The present invention relates to new compounds of the general formula: ##STR1## where X is iodine or hydrogen; A is a linking portion; and R is an iodinatable aryl or heteroaryl group having electron donating substituents. These compounds are useful precursors to the iodinated thyroid hormones for radioimmunoassay determination of thyroid hormones in biological fluids.

Abstract: A process for selectively incorporating biocompatible polymers in the interstices of implantable biological tissue while leaving the outer surface of the tissue substantially free of bonded polymer. The process involves covalently binding a monomer to the tissue, contacting the tissue with a free-radical initiator, then contacting the tissue with a solution containing a second monomer and a free-radical scavenger, thereby promoting selective polymerization of the second monomer with the portion of covalently-bound first monomer which is located in the interstices of the tissue.