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. TentaGel® resins have high diffusion rates and excellent swelling in a wide range of solvents from e.g. toluene to water. This highloaded version of TentaGel® combines a significantly higher capacity with the advantages of TentaGel® resins. The spacer is in the range of MW 1500 - 2000 Da. This aldehyde resin is synthesized from TentaGel® amine acylated with 6-oxo-caproic acid. The resin is useful for the reversible protection of primary amine substrates via formation of a Schiff's base.