Synthesis and Assembly of Butyl Rubber-Poly(ethylene oxide) Graft Copolymers: From Surface Patterning to Resistance to Protein Adsorption

The patterning of copolymers on surfaces is of interest both for a fundamental understanding of polymer assembly processes and for applications ranging from microelectronics to biomaterials. Graft copolymers can provide new opportunities to control polymer composition and architecture, thus opening possibilities for new assembly processes and patterns. In this work, the reaction of a butyl rubber derivative functionalized with activated carbonates along the polymer backbone was reacted with amine terminated poly(ethylene oxide) (PEO-NH2) to provide butyl rubber-PEO graft copolymers. The high efficiency of this reaction allowed for control of the PEO content by the number of equivalents of PEO-NH2 used and its molecular weight, providing a small library of graft copolymers. This approach also provided butyl rubber PEO graft copolymers with unprecedentedly high PEO content. Thin films of the polymers, prepared by spin-casting were studied by a number of techniques including atomic force microscopy, polarized optical microscopy, profilometry, and confocal fluorescence microscopy following the adsorption of a fluorescent protein. Interestingly, as the PEO content of the copolymers increased, an evolution from complex micrometer scale to nanometer scale patterns was observed. This was accompanied by resistance of the surfaces to protein adsorption at high PRO content, demonstrating that function can evolve from the complex interplay of thermodynamic and kinetic factors governing the assembly of these thin films.