The pellicular monolith: pore-surface functionalization and surface-phase construction in macroporous polymeric materials

We report synthesis and characterization of a macroporous polymeric material containing a covalently immobilized pore-surface phase of well-defined thickness, gel-phase porosity and organic functional group content. The pore surfaces of otherwise inert macroporous (32 μm mean pore size) ultrahigh-molecular-weight polyethylene (UHMWPE) are aminated throughout using a low-pressure flowing-discharge process to enable covalent immobilization of lightly cross-linked polymer colloid particles on all pore surfaces in the monolith. Solvent swelling and chemical derivitization of the covalently immobilized polymer colloid particles produce a pore-surface gel phase of well-defined thickness, organic amine content, and gel-phase porosity. The low degree of cross-linking in the polymer colloid particles prevents dissolution of the immobilized colloid in good solvents and enables the formation of pore-surface gel phases having high gel porosity on swelling in good solvents. The pore-surface amination introduced by the flowing discharge process varies by less than 17% through 5-mm thickness of the macroporous UHMWPE material. The properties of the pore-surface gel phase also vary by less than 17% through the cross section. The pore-surface immobilized polymer colloid particles swell by a factor of 10 in water and tetrahydrofuran after derivitization with polyethylene glycol. Received: 20 November 1998 Accepted in revised form: 21 January 1999