Photoinitiated Graft Poly(organophosphazenes): Functionalized Immobilization Substrates for the Binding of Amines, Proteins, and Metals

Functionalized poly(organophosphazenes) have been prepared via photoinitiated graft polymerization with bifunctional monomers. Molecular level modification of poly[bis(p-methylphenoxy) phosphazene] (MPP) was accomplished by ultraviolet irradiation of films of the polymer which contained an unsaturated monomer and benzophenone. The grafting behavior of a number of unsaturated monomers that bear two reactive functionalities was studied. The choice of bifunctional monomers enabled the incorporation of reactive sites, which were subsequently employed for the immobilization of amines, biologically active compounds, and metal species. For example, glycidyl methacrylate (GMA) was photoinitiation grafted to MPP to prepare the MPP-graft GMA films, which were later used to immobilize protein A via a ring-opening reaction of the epoxy groups. This substrate-bound protein A retained its activity for the subsequent immobilization of the immunoglobulin IgG. Similarly, the use of 4-vinylpyridine (VP) to synthesize the MPP-graft-VP films afforded a substrate with reactive coordination sites for the attachment of metal carbonyl species. Molecular structural characterization for the poly(organophosphazene) precursors was achieved by ¹H, ¹³C, and ³¹P NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and elemental microanalyses. The photoinitiation grafted immobilization substrates were characterized via attenuated transmission reflectance infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray microanalysis, contact angle measurements, DSC, and elemental microanalyses.