TentaGel® resins are copolymers consisting of a low crosslinked polystyrene matrix on which polyethylene glycol (PEG or POE) is grafted. TentaGel® resins have high diffusion rates and excellent swelling in a wide range of solvents from e.g. toluene to water.The PEG spacer is in the range of MW 3000 Da. An active ester resin for the immobilization of nucleophiles.