Polystyrene(PS) microspheres were functionalized with poly(styrene-b-tert-butyl acrylate)(P(S-b-tBA)) by adsorption from supercritical mixture of CO_2 and hexane.Supercritical deposition formed a shell-core structure that contained a shell of poly(tert-butyl acrylate)(PtBA) blocks and a core of the PS blocks entangling with the PS microspheres. The thickness of the PtBA layer and thereby the areal density of tert-butyl ester groups increased with the deposition pressure until plateau values attained at 20 MPa and higher.The tert-butyl ester groups were hydrolyzed to carboxyl groups for conjugation with tert-butylamine molecules via amide bonds that were further chlorinated into biocidal N-halamine moieties. The functionalization layer and its bonded N-halamine moieties were stable in flowing water and the chlorine could be regenerated upon eventual loss.This functionalization concept is applicable to polymers of any external and internal surfaces to achieve diverse surface properties by varying block copolymer and conjugated moieties. Polystyrene (PS) microspheres were functionalized with poly (styrene-b-tert-butyl acrylate) (P (Sb-tBA)) by adsorption from supercritical mixture of CO 2 and hexane.Supercritical deposition formed a shell-core structure that contained a shell of The thickness of the PtBA layer and thereby the areal density of tert-butyl ester groups increased with the deposition pressure until plateau values ​​attained at 20 MPa and higher. The tert-butyl ester groups were hydrolyzed to carboxyl groups for conjugation with tert-butylamine molecules via amide bonds that were further chlorinated into biocidal N-halamine moieties. The functionalization layer and its bonded N-halamine moieties were stable in flowing water and the chlorine could be regenerated upon eventual loss. This functionalization concept is applicable to polymers of any external and internal surfaces to achieve diverse surface properties b y varying block copolymer and conjugated moieties.