A hydrophobic polymer fiber having a cationically charged coating thereon, in which the coating includes a functionalized cationic polymer, such as an epichlorohydrin-functionalized polyamine or an epichlorohydrin-functionalized polyamido-amine, which has been crosslinked by heat. The present invention also provides a fibrous filter which includes hydrophobic polymer fibers having the foregoing cationically charged coating thereon. The present invention further provides a method of preparing a fibrous filter. The method involves providing a fibrous filter comprised of hydrophobic polymer fibers; treating the fibrous filter with an aqueous solution of a functionalized cationic polymer crosslinkable by heat under conditions sufficient to substantially coat the fibers with the functionalized cationic polymer, wherein the solution includes the functionalized cationic polymer, a poly(vinyl alcohol), a polar solvent for the poly(vinyl alcohol), and water; and treating the resulting coated fibrous filter with heat at a temperature and for a time sufficient to crosslink the functionalized cationic polymer present on the hydrophobic polymer fibers. The present invention additionally provides a method of preparing a fibrous filter. The method includes providing a fibrous filter comprised of hydrophobic polymer fibers; passing a solution of a functionalized cationic polymer crosslinkable by heat through the fibrous filter under conditions sufficient to substantially coat the fibers with the functionalized cationic polymer, wherein the solution includes the functionalized cationic polymer, a poly(vinyl alcohol), and water; and treating the resulting coated fibrous filter with heat at a temperature and for a time sufficient to crosslink the functionalized cationic polymer present on the hydrophobic polymer fibers.