TentaGel® resins are grafted copolymers consisting of a low crosslinked polystyrene matrix on which polyethylene glycol (PEG or POE) is grafted via an ethyl ether group which increases stability towards acid treatment and minimizes PEG-leaching. The graft copolymer shows modified physicochemical properties which are highly dominated by the PEG moiety (and no longer by the polystyrene matrix) and has hydrophobic and hydrophilic properties. These copolymers are pressure stable and can be used in batch processes as well as under continuous flow conditions. The PEG spacer is in the range of MW 3000 Da. TentaGel® resins have high diffusion rates and excellent swelling in a wide range of solvents from e.g. toluene to water. Standard resin for a large number of applications, useful in batch and flow through systems. This resin is synthesized from TentaGel® amine and the base labile 4- (hydroxymethyl) benzoic acid linker. It is a versatile support for the immobilization of carboxylic acids. The resulting ester bond is stable to strong acids but is cleaved by nucleophiles like amines, hydrazine or alkoxides to give amides, hydrazides or esters.