A method for preparing a crosslinked polymer coated controlled porosity glass (CPG) particle is provided. The method involves mixing CPG particles in a solution comprising polyvinylbenzylchloride and a first solvent at a temperature below 10.degree. C. A second solvent is added and a crosslinking agent is added to the mixture. The first solvent is removed rapidly within 11/2 hours of addition of the crosslinking agent. The crosslinking reaction is permitted to proceed and the mixture is then cooled and treated to remove any remaining solvent. The resulting coated CPG particles are washed and dried. Also provided a polymer coated CPG particles using for loading ligand thereon.